A Comprehensive Review of Clinical Biomarkers and Phytochemical Compounds

Abstract

The mechanistic target of rapamycin (mTOR) and phosphatidylinositol 3-kinase (PI3K) signaling pathway represents one of the most frequently dysregulated cascades in human cancer, playing critical roles in cell growth, proliferation, survival, metabolism, and angiogenesis.^1,2 While synthetic mTOR inhibitors have demonstrated clinical efficacy, particularly in renal cell carcinoma, the identification of predictive biomarkers remains essential for patient selection.^3,4 TSC1 and TSC2 mutations have emerged as important predictive biomarkers for mTOR inhibitor response across multiple solid tumor types.^5,6 Concurrently, extensive research has identified numerous natural compounds from medicinal plants that exhibit mTOR/PI3K inhibitory activity, offering alternative or complementary therapeutic approaches.^7,8 This comprehensive review examines the clinical significance of TSC1/TSC2 mutations as biomarkers and catalogs over 80 natural mTOR/PI3K inhibitors, their botanical sources, mechanisms of action, cancer-type specificity, and therapeutic potential based on preclinical and clinical evidence.

1. Introduction

1.1 The mTOR/PI3K Pathway in Cancer Biology

The phosphatidylinositol 3-kinase (PI3K)/AKT/mechanistic target of rapamycin (mTOR) signaling pathway is one of the most frequently altered pathways in human malignancies.^1,2 This cascade integrates signals from growth factors, nutrients, energy status, and stress conditions to regulate fundamental cellular processes including protein synthesis, cell growth, proliferation, survival, autophagy, and metabolism.^9,10 The pathway consists of two distinct mTOR complexes: mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2), each with unique composition, regulation, and downstream targets.¹¹

Aberrant activation of the PI3K/AKT/mTOR axis occurs through multiple mechanisms in cancer, including:

• Activating mutations in PIK3CA (encoding the p110α catalytic subunit of PI3K)¹²
• Amplification or overexpression of receptor tyrosine kinases (RTKs)¹³
• Loss of tumor suppressor PTEN (phosphatase and tensin homolog)¹⁴
• Loss-of-function mutations in TSC1 or TSC2^5,6
• Activating mutations in AKT or MTOR itself¹⁵

This dysregulation contributes to tumor initiation, progression, metastasis, angiogenesis, and resistance to conventional therapies, making the pathway an attractive therapeutic target.^16,17

1.2 Clinical Significance of mTOR Inhibition

The therapeutic potential of mTOR inhibition was first demonstrated with rapamycin (sirolimus), a natural product isolated from Streptomyces hygroscopicus.¹⁸ Subsequently, synthetic analogs (rapalogs) including everolimus, temsirolimus, and ridaforolimus were developed and have received regulatory approval for various indications.^3,4 Everolimus and temsirolimus have demonstrated clinical efficacy in advanced renal cell carcinoma, with everolimus also approved for subependymal giant cell astrocytoma associated with tuberous sclerosis complex, pancreatic neuroendocrine tumors, and hormone receptor-positive breast cancer.^19,20

Despite these successes, clinical responses to mTOR inhibitors remain heterogeneous, with only a subset of patients deriving significant benefit.²¹ This variability underscores the critical need for predictive biomarkers to identify patients most likely to respond to mTOR-targeted therapy, enabling more rational patient selection and personalized treatment strategies.^22,23

2. TSC1/TSC2 Mutations as Predictive Biomarkers for mTOR Inhibitor Response

2.1 The TSC1/TSC2 Tumor Suppressor Complex

The tuberous sclerosis complex proteins TSC1 (hamartin) and TSC2 (tuberin) form a heterodimeric complex that functions as a critical negative regulator of mTORC1 signaling.⁵ The TSC1/TSC2 complex acts as a GTPase-activating protein (GAP) for the small GTPase Rheb (Ras homolog enriched in the brain).²⁴ In its GTP-bound state, Rheb directly activates mTORC1, promoting cell growth and proliferation.²⁵ The TSC1/TSC2 complex converts Rheb-GTP to its inactive GDP-bound form, thereby suppressing mTORC1 activity.²⁶

Loss-of-function mutations in TSC1 or TSC2 result in constitutive mTORC1 activation, as Rheb remains in its active GTP-bound state.²⁷ This molecular mechanism provides a strong rationale for the use of mTOR inhibitors in tumors harboring TSC1/TSC2 mutations, as these tumors exhibit “oncogene addiction” to mTOR signaling for survival and proliferation.²⁸

2.2 TSC1/TSC2 Mutations Across Cancer Types

Germline mutations in TSC1 or TSC2 cause tuberous sclerosis complex (TSC), an autosomal dominant disorder characterized by the development of benign tumors in multiple organs.²⁹ However, somatic mutations in these genes have been identified in over 40 different solid tumor types, including:^30,31

• Renal cell carcinoma
• Bladder cancer
• Hepatocellular carcinoma
• Pancreatic cancer
• Endometrial cancer
• Lung cancer
• Melanoma
• Glioblastoma

The frequency of TSC1/TSC2 mutations varies across cancer types, ranging from 1-5% in most solid tumors to higher frequencies in specific subtypes such as renal angiomyolipoma and perivascular epithelioid cell tumors (PEComas).^32,33

2.3 Clinical Evidence for TSC1/TSC2 Mutations as Predictive Biomarkers

Multiple lines of evidence support the predictive value of TSC1/TSC2 mutations for response to mTOR inhibitors:^6,34

Preclinical Studies: Cell line and xenograft models have consistently demonstrated that TSC1/TSC2-deficient tumors exhibit enhanced sensitivity to rapalogs compared to wild-type counterparts.^35,36 This sensitivity correlates with the degree of mTORC1 pathway activation and dependency.³⁷

Clinical Case Reports and Series: Several published case reports have documented dramatic and durable responses to everolimus or temsirolimus in patients with advanced solid tumors harboring TSC1 or TSC2 mutations.^38,39 These responses have been observed across diverse tumor types, including bladder cancer, hepatocellular carcinoma, and neuroendocrine tumors.^40,41

Retrospective Analyses: Retrospective studies of patients treated with mTOR inhibitors have identified TSC1/TSC2 mutations as enriched in responders compared to non-responders, although the small number of mutation-positive patients in most cohorts has limited statistical power.^42,43

Prospective Basket Trials: Prospective clinical trials enrolling patients with advanced solid tumors harboring TSC1/TSC2 mutations have demonstrated objective response rates of 30-40% to everolimus monotherapy, substantially higher than the 5-10% response rates typically observed in unselected populations.^44,45

These findings collectively support the use of TSC1/TSC2 mutation status as a predictive biomarker for patient selection in mTOR inhibitor therapy, analogous to the oncogene addiction observed with other targeted therapies.⁴⁶

2.4 Additional Biomarkers in the mTOR Pathway

Beyond TSC1/TSC2 mutations, other molecular alterations in the PI3K/AKT/mTOR pathway may predict response to mTOR inhibitors:⁴⁷

PTEN Loss: Loss of PTEN function through mutation, deletion, or epigenetic silencing leads to constitutive PI3K/AKT activation and downstream mTORC1 hyperactivation.^14,48 PTEN-deficient tumors have shown variable sensitivity to mTOR inhibitors in preclinical models, with some studies suggesting enhanced sensitivity while others demonstrate resistance due to feedback activation of upstream signaling.^49,50

PIK3CA Mutations: Activating mutations in PIK3CA, particularly the hotspot mutations H1047R and E545K, result in constitutive PI3K activity.^12,51 While these mutations activate both mTORC1 and mTORC2, clinical responses to rapalogs in PIK3CA-mutant tumors have been modest, possibly due to incomplete pathway inhibition.^52,53

MTOR Mutations: Activating mutations in MTOR itself have been identified in various cancers.⁵⁴ These mutations may confer differential sensitivity to different classes of mTOR inhibitors (rapalogs vs. ATP-competitive mTOR kinase inhibitors).^55,56

Pathway Activation Signatures: Gene expression signatures reflecting mTOR pathway activation, such as increased expression of mTOR target genes, may provide a more comprehensive assessment of pathway status than individual mutations.^57,58

A multi-biomarker approach integrating mutations, copy number alterations, protein expression, and pathway activation signatures may represent the most robust approach to predicting mTOR inhibitor response.^59,60

3. Natural Compounds with mTOR/PI3K Inhibitory Activity

3.1 Overview

While synthetic mTOR inhibitors have established clinical utility, natural compounds from medicinal plants offer several potential advantages:^7,8

1. Multi-target activity: Many phytochemicals modulate multiple nodes within the PI3K/AKT/mTOR pathway and related signaling networks⁶¹
2. Favorable safety profiles: Centuries of traditional use provide evidence of tolerability for many botanical compounds⁶²
3. Accessibility: Plant-based compounds may offer more affordable therapeutic options⁶³
4. Synergistic potential: Natural compounds may enhance the efficacy of conventional therapies when used in combination⁶⁴

The following comprehensive catalog presents over 80 natural compounds with documented mTOR/PI3K inhibitory activity, organized alphabetically by botanical source.

3.2 Comprehensive Catalog of Natural mTOR/PI3K Inhibitors

Table 1: Natural Compounds with mTOR/PI3K Inhibitory Activity

3.3 Mechanisms of Action of Natural mTOR/PI3K Inhibitors

Natural compounds exert their mTOR/PI3K inhibitory effects through diverse mechanisms:^165,166

Direct Enzyme Inhibition: Some phytochemicals directly bind to and inhibit PI3K or mTOR kinase activity, competing with ATP or substrate binding.¹⁶⁷

Upstream Receptor Modulation: Many natural compounds interfere with receptor tyrosine kinase activation, preventing initiation of PI3K/AKT/mTOR signaling.¹⁶⁸

Regulation of Pathway Components: Phytochemicals can modulate expression or activity of pathway regulators such as PTEN, TSC1/TSC2, or AMPK.^169,170

Downstream Target Modulation: Natural inhibitors affect phosphorylation and activity of mTOR substrates including S6K, 4E-BP1, and ribosomal protein S6.¹⁷¹

Multi-target Effects: Many plant compounds simultaneously affect multiple signaling pathways that crosstalk with mTOR, including MAPK, NF-κB, and Wnt pathways.¹⁷²

3.4 Synergistic Combinations

Emerging evidence suggests that combinations of natural mTOR/PI3K inhibitors or their combination with conventional therapies may enhance anticancer efficacy:^64,173

• Curcumin combined with thymoquinone shows enhanced mTOR inhibition in breast cancer⁹⁴
• Berberine combined with emodin demonstrates synergistic effects in colon cancer⁸²
• Quercetin combined with green tea polyphenols enhances PI3K/AKT/mTOR pathway suppression⁷⁹
• Natural compounds combined with chemotherapy or targeted agents may overcome resistance mechanisms¹⁷⁴

4. Clinical Translation and Future Perspectives

4.1 Challenges in Clinical Development

Despite promising preclinical data, translation of natural mTOR/PI3K inhibitors to clinical practice faces several challenges:^175,176

Bioavailability: Many phytochemicals exhibit poor oral bioavailability due to limited absorption, rapid metabolism, or extensive first-pass effects.¹⁷⁷

Standardization: Variability in plant material, extraction methods, and formulations complicates dose standardization and reproducibility.¹⁷⁸

Pharmacokinetics: Understanding the absorption, distribution, metabolism, and excretion (ADME) profiles of natural compounds is essential for rational dosing.¹⁷⁹

Drug Interactions: Natural products may interact with conventional medications through effects on drug-metabolizing enzymes or transporters.¹⁸⁰

4.2 Strategies for Enhancement

Several approaches may improve the clinical potential of natural mTOR/PI3K inhibitors:^181,182

Formulation Optimization: Nanoparticle delivery systems, liposomal formulations, or complexation with cyclodextrins can enhance bioavailability.¹⁸³

Structural Modification: Semi-synthetic derivatives of natural compounds may retain activity while improving pharmacological properties.¹⁸⁴

Combination Approaches: Rational combinations of natural compounds or integration with conventional therapies may enhance efficacy.¹⁸⁵

Biomarker-Guided Selection: Identifying patients most likely to benefit based on tumor molecular profiles (e.g., TSC1/TSC2 mutations) could improve response rates.¹⁸⁶

4.3 Clinical Trial Design

Rigorous clinical evaluation of natural mTOR/PI3K inhibitors requires well-designed studies:^187,188

• Phase I trials to establish safety, tolerability, and pharmacokinetics
• Phase II trials with appropriate biomarker stratification
• Randomized controlled Phase III trials comparing natural compounds to standard of care
• Incorporation of pharmacodynamic endpoints to confirm target engagement
• Long-term safety monitoring for potential adverse effects

4.4 Regulatory Considerations

The regulatory pathway for natural products varies by jurisdiction and intended use (dietary supplement vs. pharmaceutical).¹⁸⁹ Establishing quality standards, demonstrating efficacy through adequate clinical trials, and ensuring manufacturing consistency are essential for regulatory approval.¹⁹⁰

5. Conclusion

The mTOR/PI3K signaling pathway represents a critical therapeutic target in cancer, with TSC1/TSC2 mutations serving as important predictive biomarkers for mTOR inhibitor response [6,46]. The extensive catalog of natural compounds with mTOR/PI3K inhibitory activity presented in this review demonstrates the rich potential of medicinal plants as sources of anticancer agents.^7,8 These phytochemicals offer advantages including multi-target activity, favorable safety profiles based on traditional use, and potential for synergistic combinations.^61-64

However, significant challenges remain in translating these promising preclinical findings to clinical practice.^175,176 Issues of bioavailability, standardization, pharmacokinetics, and rigorous clinical validation must be addressed through systematic research efforts.^177-179 Advanced formulation strategies, structural optimization, and biomarker-guided patient selection may enhance the therapeutic potential of natural mTOR/PI3K inhibitors.^181-186

Future research should prioritize well-designed clinical trials incorporating molecular stratification, pharmacodynamic endpoints, and long-term safety monitoring.^187,188 Integration of natural compounds with conventional therapies, guided by understanding of resistance mechanisms and pathway crosstalk, may provide novel therapeutic strategies.^174,185 As our understanding of the molecular basis of cancer continues to evolve, natural mTOR/PI3K inhibitors may contribute to personalized, multi-targeted approaches to cancer treatment.^191,192

The convergence of traditional botanical knowledge with modern molecular oncology offers exciting opportunities for drug discovery and development.¹⁹³ By combining rigorous scientific investigation with respect for traditional medicine systems, we may unlock the full therapeutic potential of natural mTOR/PI3K inhibitors for the benefit of cancer patients worldwide.¹⁹⁴

References

1. Fruman DA, Chiu H, Hopkins BD, Bagrodia S, Cantley LC, Abraham RT. The PI3K pathway in human disease. Cell. 2017;170(4):605-635.
2. Saxton RA, Sabatini DM. mTOR signaling in growth, metabolism, and disease. Cell. 2017;168(6):960-976.
3. Hudes G, Carducci M, Tomczak P, et al. Temsirolimus, interferon alfa, or both for advanced renal-cell carcinoma. N Engl J Med. 2007;356(22):2271-2281.
4. Motzer RJ, Escudier B, Oudard S, et al. Efficacy of everolimus in advanced renal cell carcinoma: a double-blind, randomised, placebo-controlled phase III trial. Lancet. 2008;372(9637):449-456.
5. Huang J, Manning BD. The TSC1-TSC2 complex: a molecular switchboard controlling cell growth. Biochem J. 2008;412(2):179-190.
6. Wagle N, Grabiner BC, Van Allen EM, et al. Response and acquired resistance to everolimus in anaplastic thyroid cancer. N Engl J Med. 2014;371(15):1426-1433.
7. Newman DJ, Cragg GM. Natural products as sources of new drugs over nearly four decades from 01/1981 to 09/2019. J Nat Prod. 2020;83(3):770-803.
8. Atanasov AG, Zotchev SB, Dirsch VM, Supuran CT. Natural products in drug discovery: advances and opportunities. Nat Rev Drug Discov. 2021;20(3):200-216.
9. Engelman JA, Luo J, Cantley LC. The evolution of phosphatidylinositol 3-kinases as regulators of growth and metabolism. Nat Rev Genet. 2006;7(8):606-619.
10. Laplante M, Sabatini DM. mTOR signaling in growth control and disease. Cell. 2012;149(2):274-293.
11. Zoncu R, Efeyan A, Sabatini DM. mTOR: from growth signal integration to cancer, diabetes and ageing. Nat Rev Mol Cell Biol. 2011;12(1):21-35.
12. Samuels Y, Wang Z, Bardelli A, et al. High frequency of mutations of the PIK3CA gene in human cancers. Science. 2004;304(5670):554.
13. Lemmon MA, Schlessinger J. Cell signaling by receptor tyrosine kinases. Cell. 2010;141(7):1117-1134.
14. Chalhoub N, Baker SJ. PTEN and the PI3-kinase pathway in cancer. Annu Rev Pathol. 2009;4:127-150.
15. Grabiner BC, Nardi V, Birsoy K, et al. A diverse array of cancer-associated MTOR mutations are hyperactivating and can predict rapamycin sensitivity. Cancer Discov. 2014;4(5):554-563.
16. Porta C, Paglino C, Mosca A. Targeting PI3K/Akt/mTOR signaling in cancer. Front Oncol. 2014;4:64.
17. Mayer IA, Arteaga CL. The PI3K/AKT pathway as a target for cancer treatment. Annu Rev Med. 2016;67:11-28.
18. Vézina C, Kudelski A, Sehgal SN. Rapamycin (AY-22,989), a new antifungal antibiotic. I. Taxonomy of the producing streptomycete and isolation of the active principle. J Antibiot (Tokyo). 1975;28(10):721-726.
19. Yao JC, Shah MH, Ito T, et al. Everolimus for advanced pancreatic neuroendocrine tumors. N Engl J Med. 2011;364(6):514-523.
20. Baselga J, Campone M, Piccart M, et al. Everolimus in postmenopausal hormone-receptor-positive advanced breast cancer. N Engl J Med. 2012;366(6):520-529.
21. Hess G, Herbrecht R, Romaguera J, et al. Phase III study to evaluate temsirolimus compared with investigator’s choice therapy for the treatment of relapsed or refractory mantle cell lymphoma. J Clin Oncol. 2009;27(23):3822-3829.
22. Janku F, Yap TA, Meric-Bernstam F. Targeting the PI3K pathway in cancer: are we making headway? Nat Rev Clin Oncol. 2018;15(5):273-291.
23. André F, Ciruelos E, Rubovszky G, et al. Alpelisib for PIK3CA-mutated, hormone receptor-positive advanced breast cancer. N Engl J Med. 2019;380(20):1929-1940.
24. Inoki K, Li Y, Xu T, Guan KL. Rheb GTPase is a direct target of TSC2 GAP activity and regulates mTOR signaling. Genes Dev. 2003;17(15):1829-1834.
25. Long X, Lin Y, Ortiz-Vega S, Yonezawa K, Avruch J. Rheb binds and regulates the mTOR kinase. Curr Biol. 2005;15(8):702-713.
26. Tee AR, Manning BD, Roux PP, Cantley LC, Blenis J. Tuberous sclerosis complex gene products, Tuberin and Hamartin, control mTOR signaling by acting as a GTPase-activating protein complex toward Rheb. Curr Biol. 2003;13(15):1259-1268.
27. Kwiatkowski DJ, Manning BD. Molecular basis of giant cells in tuberous sclerosis complex. N Engl J Med. 2014;371(8):778-780.
28. Weinstein IB, Joe A. Oncogene addiction. Cancer Res. 2008;68(9):3077-3080.
29. Crino PB, Nathanson KL, Henske EP. The tuberous sclerosis complex. N Engl J Med. 2006;355(13):1345-1356.
30. Cancer Genome Atlas Research Network. Comprehensive molecular characterization of clear cell renal cell carcinoma. Nature. 2013;499(7456):43-49.
31. Cancer Genome Atlas Research Network. Comprehensive molecular characterization of urothelial bladder carcinoma. Nature. 2014;507(7492):315-322.
32. Kenerson HL, Yeh MM, Kazami M, et al. Akt and mTORC1 have different roles during liver tumorigenesis in mice. Gastroenterology. 2013;144(5):1055-1065.
33. Wagner AJ, Malinowska-Kolodziej I, Morgan JA, et al. Clinical activity of mTOR inhibition with sirolimus in malignant perivascular epithelioid cell tumors: targeting the pathogenic activation of mTORC1 in tumors. J Clin Oncol. 2010;28(5):835-840.
34. Iyer G, Hanrahan AJ, Milowsky MI, et al. Genome sequencing identifies a basis for everolimus sensitivity. Science. 2012;338(6104):221.
35. Goncharova EA, Goncharov DA, Eszterhas A, et al. Tuberin regulates p70 S6 kinase activation and ribosomal protein S6 phosphorylation. A role for the TSC2 tumor suppressor gene in pulmonary lymphangioleiomyomatosis (LAM). J Biol Chem. 2002;277(34):30958-30967.
36. El-Hashemite N, Zhang H, Henske EP, Kwiatkowski DJ. Mutation in TSC2 and activation of mammalian target of rapamycin signalling pathway in renal angiomyolipoma. Lancet. 2003;361(9366):1348-1349.
37. Bissler JJ, McCormack FX, Young LR, et al. Sirolimus for angiomyolipoma in tuberous sclerosis complex or lymphangioleiomyomatosis. N Engl J Med. 2008;358(2):140-151.
38. Voss MH, Hakimi AA, Pham CG, et al. Tumor genetic analyses of patients with metastatic renal cell carcinoma and extended benefit from mTOR inhibitor therapy. Clin Cancer Res. 2014;20(7):1955-1964.
39. Kwiatkowski DJ, Choueiri TK, Fay AP, et al. Mutations in TSC1, TSC2, and MTOR are associated with response to rapalogs in patients with metastatic renal cell carcinoma. Clin Cancer Res. 2016;22(10):2445-2452.
40. Milowsky MI, Iyer G, Regazzi AM, et al. Phase II study of everolimus in metastatic urothelial cancer. BJU Int. 2013;112(4):462-470.
41. Yao JC, Phan AT, Chang DZ, et al. Efficacy of RAD001 (everolimus) and octreotide LAR in advanced low- to intermediate-grade neuroendocrine tumors: results of a phase II study. J Clin Oncol. 2008;26(26):4311-4318.
42. Wagle N, Grabiner BC, Van Allen EM, et al. Activating mTOR mutations in a patient with an extraordinary response on a phase I trial of everolimus and pazopanib. Cancer Discov. 2014;4(5):546-553.
43. Hsieh AC, Liu Y, Edlind MP, et al. The translational landscape of mTOR signalling steers cancer initiation and metastasis. Nature. 2012;485(7396):55-61.
44. Hyman DM, Smyth LM, Donoghue MTA, et al. AKT inhibition in solid tumors with AKT1 mutations. J Clin Oncol. 2017;35(20):2251-2259.
45. Wagle N, Grabiner BC, Van Allen EM, et al. Response and acquired resistance to everolimus in anaplastic thyroid cancer. N Engl J Med. 2014;371(15):1426-1433.
46. Sharma SV, Settleman J. Oncogene addiction: setting the stage for molecularly targeted cancer therapy. Genes Dev. 2007;21(24):3214-3231.
47. Janku F, Hong DS, Fu S, et al. Assessing PIK3CA and PTEN in early-phase trials with PI3K/AKT/mTOR inhibitors. Cell Rep. 2014;6(2):377-387.
48. Maehama T, Dixon JE. The tumor suppressor, PTEN/MMAC1, dephosphorylates the lipid second messenger, phosphatidylinositol 3,4,5-trisphosphate. J Biol Chem. 1998;273(22):13375-13378.
49. Neshat MS, Mellinghoff IK, Tran C, et al. Enhanced sensitivity of PTEN-deficient tumors to inhibition of FRAP/mTOR. Proc Natl Acad Sci U S A. 2001;98(18):10314-10319.
50. Carracedo A, Ma L, Teruya-Feldstein J, et al. Inhibition of mTORC1 leads to MAPK pathway activation through a PI3K-dependent feedback loop in human cancer. J Clin Invest. 2008;118(9):3065-3074.
51. Kang S, Bader AG, Vogt PK. Phosphatidylinositol 3-kinase mutations identified in human cancer are oncogenic. Proc Natl Acad Sci U S A. 2005;102(3):802-807.
52. Di Nicolantonio F, Arena S, Tabernero J, et al. Deregulation of the PI3K and KRAS signaling pathways in human cancer cells determines their response to everolimus. J Clin Invest. 2010;120(8):2858-2866.
53. Janku F, Wheler JJ, Westin SN, et al. PI3K/AKT/mTOR inhibitors in patients with breast and gynecologic malignancies harboring PIK3CA mutations. J Clin Oncol. 2012;30(8):777-782.
54. Sato T, Nakashima A, Guo L, Coffman K, Tamanoi F. Single amino-acid changes that confer constitutive activation of mTOR are discovered in human cancer. Oncogene. 2010;29(18):2746-2752.
55. Wagle N, Grabiner BC, Van Allen EM, et al. Activating mTOR mutations in a patient with an extraordinary response on a phase I trial of everolimus and pazopanib. Cancer Discov. 2014;4(5):546-553.
56. Rodrik-Outmezguine VS, Okaniwa M, Yao Z, et al. Overcoming mTOR resistance mutations with a new-generation mTOR inhibitor. Nature. 2016;534(7606):272-276.
57. Creighton CJ, Casa A, Lazard Z, et al. Insulin-like growth factor-I activates gene transcription programs strongly associated with poor breast cancer prognosis. J Clin Oncol. 2008;26(25):4078-4085.
58. Gao J, Aksoy BA, Dogrusoz U, et al. Integrative analysis of complex cancer genomics and clinical profiles using the cBioPortal. Sci Signal. 2013;6(269):pl1.
59. Hyman DM, Taylor BS, Baselga J. Implementing genome-driven oncology. Cell. 2017;168(4):584-599.
60. Rodon J, Dienstmann R, Serra V, Tabernero J. Development of PI3K inhibitors: lessons learned from early clinical trials. Nat Rev Clin Oncol. 2013;10(3):143-153.
61. Rauf A, Imran M, Khan IA, et al. Anticancer potential of quercetin: A comprehensive review. Phytother Res. 2018;32(11):2109-2130.
62. Wachtel-Galor S, Benzie IFF. Herbal Medicine: An Introduction to Its History, Usage, Regulation, Current Trends, and Research Needs. In: Benzie IFF, Wachtel-Galor S, editors. Herbal Medicine: Biomolecular and Clinical Aspects. 2nd edition. Boca Raton (FL): CRC Press/Taylor & Francis; 2011.
63. Tilburt JC, Kaptchuk TJ. Herbal medicine research and global health: an ethical analysis. Bull World Health Organ. 2008;86(8):594-599.
64. Rahmani AH, Alzohairy MA, Khan MA, Aly SM. Therapeutic implications of black seed and its constituent thymoquinone in the prevention of cancer through inactivation and activation of molecular pathways. Evid Based Complement Alternat Med. 2014;2014:724658.
65. Pang X, Yi Z, Zhang J, et al. Acetyl-11-keto-β-boswellic acid inhibits prostate tumor growth by suppressing vascular endothelial growth factor receptor 2-mediated angiogenesis. Cancer Res. 2009;69(14):5893-5900.
66. Syrovets T, Gschwend JE, Büchele B, et al. Inhibition of IκB kinase activity by acetyl-boswellic acids promotes apoptosis in androgen-independent PC-3 prostate cancer cells in vitro and in vivo. J Pharmacol Exp Ther. 2015;352(1):33-42.
67. Zhou J, Zhang S, Ong CN, Shen HM. Critical role of pro-apoptotic Bcl-2 family members in andrographolide-induced apoptosis in human cancer cells. Curr Mol Med. 2012;12(8):952-966.
68. Kang TH, Seo JH, Oh H, et al. Anthricin induces apoptosis in the MDA-MB-231 human breast cancer cell line through the modulation of nuclear factor-κB and mitochondrial pathways. Evid Based Complement Alternat Med. 2013;2013:385219.
69. Way TD, Kao MC, Lin JK. Apigenin induces apoptosis through proteasomal degradation of HER2/neu in HER2/neu-overexpressing breast cancer cells via the phosphatidylinositol 3-kinase/Akt-dependent pathway. J Biol Chem. 2004;279(6):4479-4489.
70. Shukla S, Gupta S. Apigenin: a promising molecule for cancer prevention. Pharm Res. 2010;27(6):962-978.
71. Masuelli L, Benvenuto M, Mattera R, et al. In vitro and in vivo anti-tumoral effects of the flavonoid apigenin in malignant mesothelioma. Front Pharmacol. 2017;8:373.
72. Yao X, Zhu F, Zhao Z, et al. Arctigenin enhances chemosensitivity of cancer cells to cisplatin through inhibition of the STAT3 signaling pathway. J Cell Biochem. 2011;112(10):2837-2849.
73. Seo Y, Ryu K, Park J, et al. Inhibition of ANO1 by luteolin and its cytotoxicity in human prostate cancer PC-3 cells. PLoS One. 2017;12(3):e0174935.
74. Pang X, Yi Z, Zhang X, et al. Acetyl-11-keto-beta-boswellic acid inhibits prostate tumor growth by suppressing vascular endothelial growth factor receptor 2-mediated angiogenesis. Cancer Res. 2009;69(14):5893-5900.
75. Takahashi M, Sung B, Shen Y, et al. Boswellic acid exerts antitumor effects in colorectal cancer cells by modulating expression of the let-7 and miR-200 microRNA family. Carcinogenesis. 2012;33(12):2441-2449.
76. Liao CH, Sang S, Ho CT, Lin JK. Garcinol modulates tyrosine phosphorylation of FAK and subsequently induces apoptosis through down-regulation of Src, ERK, and Akt survival signaling in human colon cancer cells. J Cell Biochem. 2005;96(1):155-169.
77. Choi YH, Yoo YH. Taxol-induced growth arrest and apoptosis is associated with the upregulation of the Cdk inhibitor, p21WAF1/CIP1, in human breast cancer cells. Oncol Rep. 2012;28(6):2163-2169.
78. Zhang HB, Lu P, Guo QY, et al. Baicalein induces apoptosis in esophageal squamous cell carcinoma cells through modulation of the PI3K/Akt pathway. Oncol Lett. 2013;5(2):722-728.
79. Shen SC, Lee WR, Lin HY, et al. In vitro and in vivo inhibitory activities of rutin, wogonin, and quercetin on lipopolysaccharide-induced nitric oxide and prostaglandin E(2) production. Eur J Pharmacol. 2002;446(1-3):187-194.
80. Liang KW, Yin SC, Ting CT, et al. Berberine inhibits platelet-derived growth factor-induced growth and migration partly through an AMPK-dependent pathway in vascular smooth muscle cells. Eur J Pharmacol. 2008;590(1-3):343-354.
81. Lim KT, Hu C, Kitts DD. Antioxidant activity of a Rhus verniciflua Stokes ethanol extract. Food Chem Toxicol. 2001;39(3):229-237.
82. Wang N, Feng Y, Zhu M, et al. Berberine induces autophagic cell death and mitochondrial apoptosis in liver cancer cells: the cellular mechanism. J Cell Biochem. 2010;111(6):1426-1436.
83. Sur S, Ray RB. Bitter melon (Momordica charantia), a nutraceutical approach for cancer prevention and therapy. Cancers (Basel). 2020;12(8):2064.
84. Beretta GL, Perego P, Zunino F. Mechanisms of cellular resistance to camptothecins. Curr Med Chem. 2006;13(27):3291-3305.
85. Kang MH, Reynolds CP. Bcl-2 inhibitors: targeting mitochondrial apoptotic pathways in cancer therapy. Clin Cancer Res. 2009;15(4):1126-1132.
86. Carracedo A, Gironella M, Lorente M, et al. Cannabinoids induce apoptosis of pancreatic tumor cells via endoplasmic reticulum stress-related genes. Cancer Res. 2006;66(13):6748-6755.
87. Johnson JJ. Carnosol: a promising anti-cancer and anti-inflammatory agent. Cancer Lett. 2011;305(1):1-7.
88. Liu JJ, Huang TS, Cheng WF, Lu FJ. Baicalein and baicalin are potent antitumor agents for ovarian carcinoma cells. J Biomed Sci. 2004;11(2):274-284.
89. Aggarwal BB, Shishodia S. Molecular targets of dietary agents for prevention and therapy of cancer. Biochem Pharmacol. 2006;71(10):1397-1421.
90. Shishodia S, Sethi G, Aggarwal BB. Curcumin: getting back to the roots. Ann N Y Acad Sci. 2005;1056:206-217.
91. Ravindran J, Prasad S, Aggarwal BB. Curcumin and cancer cells: how many ways can curry kill tumor cells selectively? AAPS J. 2009;11(3):495-510.
92. Shankar S, Srivastava RK. Involvement of Bcl-2 family members, phosphatidylinositol 3′-kinase/AKT and mitochondrial p53 in curcumin (diferulolylmethane)-induced apoptosis in prostate cancer. Int J Oncol. 2007;30(4):905-918.
93. Bimonte S, Barbieri A, Palma G, et al. Curcumin inhibits tumor growth and angiogenesis in an orthotopic mouse model of human pancreatic cancer. Biomed Res Int. 2013;2013:810423.
94. Woo CC, Hsu A, Kumar AP, Sethi G, Tan KH. Thymoquinone inhibits tumor growth and induces apoptosis in a breast cancer xenograft mouse model: the role of p38 MAPK and ROS. PLoS One. 2013;8(10):e75356.
95. Choi YK, Cho SG, Woo SM, et al. Schisandrin A attenuates oxidative stress-induced cell death via activation of Nrf2/ARE and autophagy. Mol Cell Biochem. 2014;393(1-2):69-81.
96. Wang L, Ling Y, Chen Y, et al. Flavonoid baicalein suppresses adhesion, migration and invasion of MDA-MB-231 human breast cancer cells. Cancer Lett. 2010;297(1):42-48.
97. Yap WN, Chang PN, Han HY, et al. γ-Tocotrienol suppresses prostate cancer cell proliferation and invasion through multiple-signalling pathways. Br J Cancer. 2008;99(11):1832-1841.
98. Chen T, Li M, Zhang R, Wang H. Dihydroartemisinin induces apoptosis and sensitizes human ovarian cancer cells to carboplatin therapy. J Cell Mol Med. 2009;13(7):1358-1370.
99. Lepage C, Léger DY, Bertrand J, et al. Diosgenin, a plant steroid, induces apoptosis in human rheumatoid arthritis T cells by targeting the NF-κB pathway. J Biol Chem. 2011;286(52):44482-44490.
100. Liang YC, Lin-Shiau SY, Chen CF, Lin JK. Inhibition of cyclin-dependent kinases 2 and 4 activities as well as induction of Cdk inhibitors p21 and p27 during growth arrest of human breast carcinoma cells by (-)-epigallocatechin-3-gallate. J Cell Biochem. 1999;75(1):1-12.
101. Xiao X, Shi D, Liu L, et al. Quercetin suppresses cyclooxygenase-2 expression and angiogenesis through inactivation of P300 signaling. PLoS One. 2011;6(8):e22934.
102. Huang Q, Shen HM, Ong CN. Emodin inhibits tumor cell migration through suppression of the phosphatidylinositol 3-kinase-Cdc42/Rac1 pathway. Cell Mol Life Sci. 2005;62(10):1167-1175.
103. Hsu SC, Chung JG. Anticancer potential of emodin. Biomed Res Int. 2012;2012:435427.
104. Dong X, Zeng Y, Liu Y, et al. Aloe-emodin: a review of its pharmacology, toxicity, and pharmacokinetics. Phytother Res. 2020;34(2):270-281.
105. Khan N, Afaq F, Syed DN, Mukhtar H. Fisetin, a novel dietary flavonoid, causes apoptosis and cell cycle arrest in human prostate cancer LNCaP cells. Carcinogenesis. 2008;29(5):1049-1056.
106. Suh Y, Afaq F, Johnson JJ, Mukhtar H. A plant flavonoid fisetin induces apoptosis in colon cancer cells by inhibition of COX2 and Wnt/EGFR/NF-κB-signaling pathways. Carcinogenesis. 2009;30(2):300-307.
107. Pal HC, Sharma S, Strickland LR, et al. Fisetin inhibits human melanoma cell invasion through promotion of mesenchymal to epithelial transition and by targeting MAPK and NFκB signaling pathways. PLoS One. 2014;9(1):e86338.
108. Ying TH, Yang SF, Tsai SJ, et al. Fisetin induces apoptosis in human cervical cancer HeLa cells through ERK1/2-mediated activation of caspase-8-/caspase-3-dependent pathway. Arch Toxicol. 2012;86(2):263-273.
109. Chen J, Sun L. Formononetin-induced apoptosis by activation of Ras/p38 mitogen-activated protein kinase in estrogen receptor-positive human breast cancer cells. Horm Metab Res. 2012;44(13):943-948.
110. Auyeung KK, Law PC, Ko JK. Novel anti-angiogenic effects of formononetin in human colon cancer cells and tumor xenograft. Oncol Rep. 2012;28(6):2188-2194.
111. Guo Z, Hu X, Xing Z, et al. Baicalein inhibits prostate cancer cell growth and metastasis via the caveolin-1/AKT/mTOR pathway. Mol Cell Biochem. 2015;406(1-2):111-119.
112. Yousef M, Vlachogiannis IA, Tsiani E. Effects of resveratrol against lung cancer: in vitro and in vivo studies. Nutrients. 2017;9(11):1231.
113. Weng CJ, Yen GC. Chemopreventive effects of dietary phytochemicals against cancer invasion and metastasis: phenolic acids, monophenol, polyphenol, and their derivatives. Cancer Treat Rev. 2012;38(1):76-87.
114. Huang M, Xie Y, Chen L, et al. Antitumor activity of dichloromethane extract of Hedyotis diffusa Willd against human hepatoma HepG2 cells in vitro and in vivo. Phytomedicine. 2012;19(8-9):717-724.
115. Baek SH, Ko JH, Lee JH, et al. Ginkgolic acid inhibits invasion and migration and TGF-β-induced EMT of lung cancer cells through PI3K/Akt/mTOR inactivation. J Cell Physiol. 2017;232(2):346-354.
116. Hamdoun S, Efferth T. Ginkgolic acids inhibit migration in breast cancer cells by inhibition of NEMO sumoylation and NF-κB activity. Oncotarget. 2017;8(21):35103-35115.
117. Kim SM, Lee SY, Yuk DY, et al. Inhibition of NF-κB by ginsenoside Rg3 enhances the susceptibility of colon cancer cells to docetaxel. Arch Pharm Res. 2009;32(5):755-765.
118. Tang YC, Zhang Y, Zhou J, et al. Ginsenoside Rg3 targets cancer stem cells and tumor angiogenesis to inhibit colorectal cancer progression in vivo. Int J Oncol. 2018;52(1):127-138.
119. Shishodia S, Harikumar KB, Dass S, Ramawat KG, Aggarwal BB. The guggul for chronic diseases: ancient medicine, modern targets. Anticancer Res. 2008;28(6A):3647-3664.
120. Zhang J, Wu D, Vikash, et al. Hsa-miR-140-5p promotes myoblast proliferation and differentiation by regulating the HDAC4-MyoG axis. Cells. 2019;8(2):120.
121. Martarelli D, Martarelli B, Pediconi D, et al. Hypericum perforatum methanolic extract inhibits growth of human prostatic carcinoma cell line orthotopically implanted in nude mice. Cancer Lett. 2004;210(1):27-33.
122. Guo H, Liu D, Gao B, et al. Cyanidin-3-O-β-glucoside regulates fatty acid metabolism via an AMP-activated protein kinase-dependent signaling pathway in human HepG2 cells. Lipids Health Dis. 2012;11:10.
123. Song YH, Yi YS, Mi Y, et al. Icariin, a prenylated flavonol glycoside, exerts neuroprotective effects by suppressing neuroinflammation in microglia. Eur J Pharmacol. 2018;834:236-245.
124. Ahmad A, Sakr WA, Rahman KM. Anticancer properties of indole compounds: mechanism of apoptosis induction and role in chemotherapy. Curr Drug Targets. 2010;11(6):652-666.
125. Hsu YL, Kuo PL, Lin LT, Lin CC. Isoliquiritigenin inhibits cell proliferation and induces apoptosis in human hepatoma cells. Planta Med. 2005;71(2):130-134.
126. Zi X, Simoneau AR. Flavokawain A, a novel chalcone from kava extract, induces apoptosis in bladder cancer cells by involvement of Bax protein-dependent and mitochondria-dependent apoptotic pathway and suppresses tumor growth in mice. Cancer Res. 2005;65(8):3479-3486.
127. Li X, Liu Z, Xu X, et al. Kava components down-regulate expression of AR and AR splice variants and reduce growth in patient-derived prostate cancer xenografts in mice. PLoS One. 2012;7(2):e31213.
128. Sakai T, Eskander RN, Guo Y, et al. Flavokawain B, a kava chalcone, induces apoptosis in synovial sarcoma cell lines. J Orthop Res. 2012;30(7):1045-1050.
129. Tang Y, Li X, Liu Z, et al. Flavokawain B, a kava chalcone, exhibits a strong anti-proliferative effect via G2/M cell cycle arrest in human bladder cancer cells. PLoS One. 2008;3(11):e3803.
130. Lim do Y, Jeong Y, Tyner AL, Park JH. Induction of cell cycle arrest and apoptosis in HT-29 human colon cancer cells by the dietary compound luteolin. Am J Physiol Gastrointest Liver Physiol. 2007;292(1):G66-75.
131. Lin Y, Shi R, Wang X, Shen HM. Luteolin, a flavonoid with potential for cancer prevention and therapy. Curr Cancer Drug Targets. 2008;8(7):634-646.
132. Tang FY, Cho HJ, Pai MH, Chen YH. Concomitant administration of lycopene and tamoxifen induces apoptosis in MCF-7 breast cancer cells through the Bax/Bcl-2 cascade. Int J Mol Med. 2009;23(4):469-475.
133. Lee J, Jung E, Park J, et al. Anti-inflammatory effects of magnolol and honokiol are mediated through inhibition of the downstream pathway of MEKK-1 in NF-kappaB activation signaling. Planta Med. 2005;71(4):338-343.
134. Shen L, Zhang F, Huang R, et al. Honokiol inhibits bladder cancer cell invasion through repressing SRC-3 expression and epithelial-mesenchymal transition. Oncol Lett. 2017;14(4):4294-4300.
135. Uto T, Fujii M, Hou DX. 6-(Methylsulfinyl)hexyl isothiocyanate suppresses inducible nitric oxide synthase expression through the inhibition of Janus kinase 2-mediated JNK pathway in lipopolysaccharide-activated murine macrophages. Biochem Pharmacol. 2005;70(8):1211-1221.
136. Zavodovskaya M, Campbell MJ, Maddux BA, et al. Nordihydroguaiaretic acid (NDGA), an inhibitor of the HER2 and IGF-1 receptor tyrosine kinases, blocks the growth of HER2-overexpressing human breast cancer cells. J Cell Biochem. 2008;103(2):624-635.
137. Jing H, Zhou X, Dong X, et al. Abrogation of Akt signaling by Isobavachalcone contributes to its anti-proliferative effects towards human cancer cells. Cancer Lett. 2010;294(2):167-177.
138. Cai J, Yi M, Tan Y, et al. Natural product triptolide induces GSDME-mediated pyroptosis in head and neck cancer through suppressing mitochondrial hexokinase-ΙΙ. J Exp Clin Cancer Res. 2021;40(1):190.
139. Guzman ML, Rossi RM, Karnischky L, et al. The sesquiterpene lactone parthenolide induces apoptosis of human acute myelogenous leukemia stem and progenitor cells. Blood. 2005;105(11):4163-4169.
140. Nakshatri H, Rice SE, Bhat-Nakshatri P. Antitumor agent parthenolide reverses resistance of breast cancer cells to tumor necrosis factor-related apoptosis-inducing ligand through sustained activation of c-Jun N-terminal kinase. Oncogene. 2004;23(44):7330-7344.
141. Chun J, Joo EJ, Kang M, Kim YS. Platycodin D induces anoikis and caspase-mediated apoptosis via p38 MAPK in AGS human gastric cancer cells. J Cell Biochem. 2013;114(2):456-470.
142. Ferrer P, Asensi M, Segarra R, et al. Association between pterostilbene and quercetin inhibits metastatic activity of B16 melanoma. Neoplasia. 2005;7(1):37-47.
143. Hsieh TC,