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Pathways of Targeted Therapy for Colorectal Cancer

Sameeksha Jain*¹, Arpana Purohit¹, Prakhar Nema¹, Harshna Vishwakarma¹, Arzoo Qureshi ², Prateek kumar Jain¹

¹ Adina College of Pharmacy, ADINA Campus Rd, Lahdara, Sagar, MP, 470001

² Yuva Institute of Pharmacy, Infront of Bees Bhuja Mata Mandir, Bajrangarh, Guna, MP, 473249

Introduction 

The second most deadly and third most common malignant tumor in the world is colorectal cancer (CRC). Nearly 10% of all new cancer cases and fatalities globally occurred in 2018 due to the 1.8 million new CRC cases that were diagnosed and the 881,000 deaths that were reported ¹. By 2035, the number of new cases may reach nearly 2.5 million². The survival time for CRC has been increasing as a result of improvements in main and adjuvant therapies. The optimum CRC treatment typically entails surgical surgery to completely remove the tumor and any metastases³. However, despite the development of numerous screening programs to lower CRC incidence, 20% of the remaining cases may develop metachronous metastases, which make curative surgical control challenging and ultimately lead to tumor-related deaths. Nearly 25% of CRCs are diagnosed at a later stage with metastases^4-7. The goal for patients with refractory lesions or those who are not surgical candidates is optimal cancer shrinking and suppression of further tumor spread and progression. Radiotherapy and chemotherapy are the most effective methods for managing disease in these individuals. It should be noted that in some circumstances, chemotherapy or radiotherapy may be used as neoadjuvant or adjuvant treatments before or after surgery to help the tumor be reduced and stabilized to its full potential ^8-11. Currently available chemotherapy options include myriad regimens with one or more medicines, such as oxaliplatin (OX), irinotecan (IRI), and capecitabine, as well as standard therapy, which is mostly based on fluoropyrimidine (5-FU) (CAP or XELODA or XEL). The combined therapy regimens FOLFOX (5-FU+OX), FOXFIRI (5-FU+IRI), XELOX or CAPOX (CAP+OX), and CAPIRI (CAP+OX) remain the standard first-line treatments, while patients with poor performance or at low risk of deterioration are advised to receive single-agent therapy. This is true even though study results have asserted that first-line single-agent therapy is not subordinate to combined regimens in terms of overall Effectiveness seems to be comparable when selecting additive agents, and only negative impacts may vary across different regimens ^11-16. In the multiple-agent regimen FOLOXIRI (5-FU+OX+IRI), which is rarely used because it has the potential for greater toxicity, emerging evidence does not suggest higher efficacy^{17, 18}. Chemotherapy does have several drawbacks, though, including systemic toxicity that already exists, an unsatisfactory response rate, unpredictability in innate and acquired resistance, and a lack of tumor-specific selectivity. The concept of molecular targeted therapy has been around for a while. The idea of a chemical agent that particularly targets a microorganism was first put forth in the early 1900s, expanded to include cancer treatment in 1988 ¹⁹, and has since been revived and prospered over the past 20 years²⁰. By specifically preventing cell division, migration, and proliferation, targeted medicines can effectively treat malignant cells. Targeted medications may also change the tumor microenvironment, which includes local blood vessels and immune cells, to reduce tumor development and strengthen immune surveillance and defense. Targeted therapies rely heavily on small molecules like monoclonal antibodies^21-23. Small molecules are a class of molecules with a molecular weight of less than 900 Da that can enter cells and work primarily inside cells to inactivate certain enzymes, inhibiting the tumor cell proliferation and even inducing apoptosis. The majority of the molecular targets include proteasomes, poly ADP-ribose polymerase, and cyclin-dependent kinases. Some examples include rucaparib for BRCA-positive ovarian cancer, carfilzomib for multiple myeloma, and ribociclib for metastatic breast cancer²⁰. Monoclonal antibodies or therapeutic antibodies can detect and bind receptors outside of cells, such as cell surface receptors or membrane-bound sites, to directly control subsequent cell cycle progression and cell death. Additionally, several monoclonal antibodies target immune cells and other cells outside cancer cells, which aids in the manipulation of the immune system to attack cancer.

Pathways of current CRC-targeted therapy 

Desirable targets for targeted therapy can be found in a number of pathways that control the onset, progression, and migration of CRC, including Wnt/-catenin, Notch, Hedgehog, and TGF- (transforming growth factor-)/SMAD, in addition to those that can activate signaling cascades, like phosphatidylinositol 3-kinase (PI3K)/AKT or RAS/rapidly accelerated fibros ^24,25. A substantial number of targeted drugs are still in preclinical models or phase I trials due to the complexity of down-stream signalling pathway and the challenges associated with completely inhibiting particular biological interactions. As a result, not all CRC-related pathways can indeed be satisfactorily tried to interfere with, and the available data only cover a small number of pathways in which experimentally identified targeted agents can be demonstrated to be effective in clinical studies.

The VEGF/VEFGR pathway

Angiogenesis, a physiological process through which new blood vessels develop or remodel from pre-existing ones, is essential for the development, growth, and spread of tumors. A number of proangiogenic and antiangiogenic substances, including VEGF, fibroblast growth factors (FGFs), TGF-, TGF-, platelet-derived endothelial cell growth factor (PDGF) and angiopoietins produced by cancer or stromal cells, are involved in the complicated regulation of angiogenesis ^26-28. Until the discovery of VEGF-A (also known as VEGF) and the creation of its monoclonal antibody inhibitor, the link between neo-vessels and carcinogenesis remained hypothetical. This was followed by conclusive evidence of the tumor-promoting role of angiogenesis²⁹. For a tumor to form, grow, and spread, angiogenesis, a physiological process wherein new blood capillaries form or reorganize from already-existing ones, is required. VEGF, fibroblast growth factors (FGFs), TGF-, platelet-derived endothelial cell growth factor (PDGF), and angiopoietins produced by cancer or stromal cells are only a few of the proangiogenic and antiangiogenic chemicals that are involved in the intricate regulation of angiogenesis^26-28. Neo-vessels and carcinogenesis were thought to be unrelated till the identification of VEGF-A (popularly called as VEGF) and the development of its monoclonal antibody inhibitor. Thereafter, unambiguous proof of angiogenesis' participation in tumor promotion was presented.

Immune checkpoint inhibitor therapy 

In addition to methods directly blocking pathways that contribute to tumor growth and spread, accumulating data suggest that targeting other pathways to enhance immune recognition and the response against cancer cells might be effective. Malignancies harboring various genetic and epigenetic alterations may be identified and obliviated by the host immune system via the expression of abnormal antigens. The detection process comprises several steps, including T cells binding to major histo-compatibility complex (MHC) molecules held by antigen-presenting cells (APCs), followed by the next step involving secondary signals mediated via co stimulatory or inhibitory receptors that play a vital role in the activation and tolerance of T cells ^30,31. The mounting research shows that targeting alternative pathways to improve immunorecognition and the response against cancer cells may be useful in contrast to techniques that directly disrupt pathways that support tumor development and spread. Through the production of aberrant antigens, the host immune system is able to recognize and eradicate cancers that possess a variety of genetic and epigenetic abnormalities. The detection method involves a number of steps, starting with T cells binding to major histocompatibility complex (MHC) molecules held by antigen-presenting cells (APCs), then moving on to secondary transmissions mediated by co - stimulatory or inhibiting receptors, which are crucial for the stimulation and sensitivity of T cells ^30,31. A dual system is crucial in disastrous disorders to allow for flexible attack of aberrant cells as well as physiological functions to prevent an overwhelming immune response³².

The EGFR-related pathway 

EGFR (epidermal growth factor receptor) is one of 4 members of the ErbB/HER family: ErbB1 (EGFR/HER1), ErbB2 (Neu/HER2), ErbB3 (HER3), and ErbB4 (HER4) ^{33, 34}. which also includes erythroblastosis oncogene B and human epidermal growth factor receptor. The ErbB receptors are highly distinctive among the variety of receptor tyrosine kinases and were initially thought to be associated with cancer approximately 30 years ago. These transmembrane glycoproteins can only be activated after homo- or heterodimerization with HER2, HER3, or HER4 by specific binding, mostly by EGF or TGF-, due to the decreased kinase activity of HER3/ErbB3 and the lack of a direct ligand for HER2/ ErbB2. In order to control cell growth, survival, and migration, a number of downstream intracellular signaling pathways, such as the Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3), RAS/RAF/MEK/ERK, PI3K/AKT, and JAK/STAT3 pathways, are triggered once they have been activated ^35-37. 

Glioma, melanoma, medulloblastoma, gastrointestinal malignancies such esophageal, colorectal, and gastric cancers, as well as cancers of the lung, breast, bladder, prostate, pancreas, and ovary have indeed been found to express EGFR and HER abnormally³³. A poor prognosis may also be indicated by the overexpression of EGFR, which has been seen in 15-30% of breast tumors, 60% of NSCLCs (non-small-cell lung cancer), and 2-77% of CRCs^{38, 40}. 20-30% of breast and ovarian cancers^{37, 41}, 3.8-36.6% of gastric cancers³⁸and 1.3-47.7% of CRCs exhibit HER2 over expression^{33, 40}. HER3 was not allowed to be a pharmacological target due to the difficulty in locating its ligand, despite the fact that it expressed at a higher level in malignancies of the breast, ovary, and bladder, as well as 83% of gastrointestinal tumors, than in normal tissues. Given that both cancer-promoting and cancer-suppressing effects have been observed, HER4 is still a contentious topic^{45, 46}. As a result, significant efforts are being made to create widely used, targeted medicines for HER1 and HER2, despite the threat of drug resistance brought on by HER1 and HER2 mutations.

The HGF/C-MET Pathway

Hepatocyte growth factor (HGF) as well as the MET proto-oncogene-encoded receptor tyrosine kinase, also called as mesenchymal-epithelial transition factor (c-MET or MET), are essential for the growth, survival, metastasis, and development of drug resistance in tumors^47-51. In the 1980s, a human osteosarcoma cell line containing TPR-MET fusion genes (translocated promoter region locus on chromosome 1 and MET sequence on chromosome 7) was utilized to identify this signaling pathway for the very first time. At the time, HGF was also known as scatter factor since it had briefly sequestered from rat platelets and existed in charge of epithelial dissemination in organ regeneration and recovery. The only known ligand for MET at this time is^52-55. HGF, which is mostly released by mesenchymal tissues. Its tissue and serum expression levels are associated with a poor prognosis in patients with several malignant tumors, including breast, esophageal, gastric, and most significantly CRC malignancies⁵⁶. At the time of diagnosis, blood HGF levels are higher in patients who have advanced CRC and they drop after the cancer has been removed^{57, 58}. 

Other pathways 

It seems that the creation of novel targeted drugs based on pathways other than those already well-known to science proceeds relatively slowly. Drugs targeting IGF-1R, Wnt, Notch, Hedgehog, human death receptor 5, and TGF- were the subject of a few clinical trials, but as yet, no promising findings have been seen. In phase II trials, for instance, the -secretase inhibitor RO4929097 used in Notch blockade therapy and the Hedgehog pathway inhibitor vismode gib had negligible effects^{59, 60}. Review was also done on the meager success of anti-TGF- and anti-Wnt treatment against CRC^{61, 62}. When it comes to Wnt inhibition, medicines like COX-2 inhibitors have been proven to be useful in CRC prevention; however, alternative agents that could improve chemotherapeutic sensitivity while also directing CRC-control-targeted medications with high affinity to single targets are currently being developed. The fact that therapy is ineffective and many other challenges, such as finding outcome monitor markers, screening patients who would respond well, and effectively blocking specific targets, have emerged, but this has not stopped research on novel drugs⁶³.

Future directions and conclusions 

Because of improving sequence technology, human genomic, transcriptional, proteomic, and epigenetic details have never been as accessible as they were in the last few years. Changes in cell differentiation, proliferation, and survival caused by genetic profile changes contribute to the onset and progression of cancer. Based on the identification of these heterogeneities, treatments targeting specific enzymes, growth factor receptors, and signal transducers enable customized cancer therapy, allowing many oncogenic cellular systems to also be effectively interrupted to, holding the pledge of accurate cancer elimination and improved patient care. After decades of investigation and production, significant steps have been taken to update CRC-targeted medications for improved patient compliance, fewer adverse effects, and more personalized therapy regimens. While targeted therapy has been linked to longer survival, it comes with a number of drawbacks like When current chemotherapy is substantially affordable than more tailored regimens, especially for patients who may require numerous targeted drugs, the cost-benefit balance is unclear and Targeted therapy may result in unexpected side effects. In general, we are inspired not simply by the reality that patients with CRC are living longer lives with a plethora of targeted treatments, one or more of which may eventually be beneficial, but we also anticipate the development of even more services to the patients that promote even longer survival, have fewer adverse reactions, and have the prospects for complete recovery.

References

1. Bray F et al., Global cancer statistics 2018: Globocan estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin., 2018; 68:394-424.https://doi.org/10.3322/caac.21492

2. Dekker E, Tanis PJ, Vleugels JLA, Kasi PM, Wallace MB. Colorectal cancer. Lancet, 2019; 394:1467-1480. https://doi.org/10.1016/S0140-6736(19)32319-0

3. Kuipers EJ, et al., Colorectal cancer. Nat Rev Dis Prim., 2015; 1: 15065. https://doi.org/10.1038/nrdp.2015.65

4. Keum N, Giovannucci E. Global burden of colorectal cancer: emerging trends, risk factors and prevention strategies. Nat Rev Gastroenterol Hepatol., 2019; 16:713-732. https://doi.org/10.1038/s41575-019-0189-8

5. Sanchez-Gundin J, Fernandez-Carballido AM, Martinez-Valdivieso L, BarredaHernandez D, Torres-Suarez AI. New trends in the therapeutic approach to metastatic colorectal cancer. Int J Med Sci., 2018; 15:659-665. https://doi.org/10.7150/ijms.24453

6. Wolf AMD, et al., Colorectal cancer screening for average-risk adults: 2018 guideline update from the American Cancer Society. CA Cancer J Clin., 2018; 68:250-281. https://doi.org/10.3322/caac.21457

7. Van der Stok EP, Spaander MCW, Grunhagen DJ, Verhoef C, Kuipers EJ. Surveillance after curative treatment for colorectal cancer. Nat Rev Clin Oncol 2017; 14:297-315. https://doi.org/10.1038/nrclinonc.2016.199

8. Messersmith WA. NCCN guidelines updates: management of metastatic colorectal cancer. J Natl Compr Cancer Netw., 2019; 17:599-601.

9. Brown KGM, Solomon MJ, Mahon K, O'Shannassy S. Management of colorectal cancer. British Med J., 2019; 366: l4561. https://doi.org/10.1136/bmj.l4561

10. Labianca R, et al., Early colon cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann. Oncol., 2013; 24(6):vi64-vi72. https://doi.org/10.1093/annonc/mdt354

11. Van Cutsem E, Cervantes A, Nordlinger B, Arnold D. Metastatic colorectal cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and followup. Ann Oncol., 2014; 25(3):iii1-iii9. https://doi.org/10.1093/annonc/mdu260

12. Seymour MT, et al., Different strategies of sequential and combination chemotherapy for patients with poor prognosis advanced colorectal cancer (MRC FOCUS): a randomised controlled trial. Lancet. 2007; 370:143-152. https://doi.org/10.1016/S0140-6736(07)61087-3

13. Koopman M, et al., Sequential versus combination chemotherapy with capecitabine, irinotecan, and oxaliplatin in advanced colorectal cancer (CAIRO): a phase III randomised controlled trial. Lancet. 2007; 370:135-142. https://doi.org/10.1016/S0140-6736(07)61086-1

14. Colucci G, et al., Phase III randomized trial of FOLFIRI versus FOLFOX4 in the treatment of advanced colorectal cancer: a multicenter study of the Gruppo Oncologico Dell'Italia Meridionale. J Clin Oncol., 2005; 23:4866-4875. https://doi.org/10.1200/JCO.2005.07.113

15. Tournigand C, et al., FOLFIRI followed by FOLFOX6 or the reverse sequence in advanced colorectal cancer: a randomized GERCOR study. J Clin Oncol., 2004; 22:229-237. https://doi.org/10.1200/JCO.2004.05.113

16. Sundari A, Jayakumararaj  R, Herbal remedies used to treat skin disorders in Arasankulam region of Thoothukudi District in Tamil Nadu, India Journal of Drug Delivery and Therapeutics, 2020; 8(5):33-38. https://doi.org/10.22270/jddt.v10i5.4277  

17. Falcone A, et al., Phase III trial of infusional fluorouracil, leucovorin, oxaliplatin, and irinotecan (FOLFOXIRI) compared with infusional fluorouracil, leucovorin, and irinotecan (FOLFIRI) as first-line treatment for metastatic colorectal cancer: the Gruppo Oncologico Nord Ovest. J Clin Oncol., 2007; 25:1670-1676. https://doi.org/10.1200/JCO.2006.09.0928

18. Souglakos J, et al., FOLFOXIRI (folinic acid, 5-fluorouracil, oxaliplatin and irinotecan) vs FOLFIRI (folinic acid, 5-fluorouracil and irinotecan) as first-line treatment in metastatic colorectal cancer (MCC): a multicentre randomised phase III trial from the Hellenic Oncology Research Group (HORG). Br J Cancer., 2006; 94:798-805. https://doi.org/10.1038/sj.bjc.6603011

19. Brodsky FM. Monoclonal antibodies as magic bullets. Pharm Res., 1988; 5:1-9.

20. Lee YT, Tan YJ, Oon CE. Molecular targeted therapy: treating cancer with specificity. Eur J Pharm., 2018; 834:188-196. https://doi.org/10.1016/j.ejphar.2018.07.034

21. Oh DY, Bang YJ. HER2-targeted therapies-a role beyond breast cancer. Nat Rev Clin Oncol., 2020; 17:33-48. https://doi.org/10.1038/s41571-019-0268-3

22. Ferguson FM, Gray NS. Kinase inhibitors: the road ahead. Nat Rev Drug Discov., 2018; 17:353-377. https://doi.org/10.1038/nrd.2018.21

23. Tariman JD. Changes in cancer treatment: Mabs, Mibs, Mids, Nabs, and Nibs. Nurs. Clin N Am., 2017; 52:65-81. https://doi.org/10.1016/j.cnur.2016.10.004

24. Tiwari A, Saraf S, Verma A, Panda PK, Jain SK. Novel targeting approaches and signaling pathways of colorectal cancer: An insight. World J Gastroenterol., 2018; 24:4428-4435. https://doi.org/10.3748/wjg.v24.i39.4428

25. Krishnamurthy N, Kurzrock R. Targeting the Wnt/beta-catenin pathway in cancer: update on effectors and inhibitors. Cancer Treat Rev., 2018; 62: 50-60. https://doi.org/10.1016/j.ctrv.2017.11.002

26. Saharinen P, Eklund L, Pulkki K, Bono P, Alitalo K. VEGF and angiopoietin signaling in tumor angiogenesis and metastasis. Trends Mol Med., 2011; 17:347-362. https://doi.org/10.1016/j.molmed.2011.01.015

27. Goel HL, Mercurio AM. VEGF targets the tumour cell. Nat Rev Cancer. 2013; 13:871-882. https://doi.org/10.1038/nrc3627

28. Ferrara N, Gerber HP, LeCouter J. The biology of VEGF and its receptors. Nat Med., 2003; 9:669-676. https://doi.org/10.1038/nm0603-669

29. Folkman J. Tumor angiogenesis: therapeutic implications. N Engl J Med., 1971; 285:1182-1186. https://doi.org/10.1056/NEJM197111182852108

30. Sharpe AH, Freeman GJ. The B7-CD28 superfamily. Nat Rev Immunol., 2002; 2:116-126. https://doi.org/10.1038/nri727

31. Jelinek T, Mihalyova J, Kascak M, Duras J, Hajek R. PD-1/PD-L1 inhibitors in haematological malignancies: update 2017. Immunology. 2017; 152:357-371. https://doi.org/10.1111/imm.12788

32. Chen L Han X. Anti-PD-1/PD-L1 therapy of human cancer: past, present, and future. J Clin Invest., 2015; 125:3384-3391. https://doi.org/10.1172/JCI80011

33. Arteaga CL, Engelmann JA. ERBB receptors: from oncogene discovery to basic science to mechanism-based cancer therapeutics. Cancer Cell. 2014; 25: 282-303. https://doi.org/10.1016/j.ccr.2014.02.025

34. Tebbutt N, Pedersen MW, Johns TG. Targeting the ERBB family in cancer: couples therapy. Nat Rev Cancer. 2013; 13:663-673. https://doi.org/10.1038/nrc3559

35. Roskoski R. Small molecule inhibitors targeting the EGFR/ErbB family of protein-tyrosine kinases in human cancers. Pharm Res., 2019; 139: 395-411. https://doi.org/10.1016/j.phrs.2018.11.014

36. Vecchione L, Jacobs B, Normanno N, Ciardiello F, Tejpar S. EGFR-targeted therapy. Exp Cell Res., 2011; 317:2765-2771. https://doi.org/10.1016/j.yexcr.2011.08.021

37. Wang Z. ErbB receptors and cancer. Methods Mol Biol., 2017; 1652:3-35. https://doi.org/10.1007/978-1-4939-7219-7_1

38. Hsu JL, Hung MC. The role of HER2, EGFR, and other receptor tyrosine kinases in breast cancer. Cancer Metastasis Rev., 2016; 35:575-588. https://doi.org/10.1007/s10555-016-9649-6

39. Rotow J, Bivona TG. Understanding and targeting resistance mechanisms in NSCLC. Nat Rev Cancer. 2017; 17: 637-658. https://doi.org/10.1038/nrc.2017.84

40. Roskoski R. The ErbB/HER family of protein-tyrosine kinases and cancer. Pharm Res., 2014; 79:34-74. https://doi.org/10.1016/j.phrs.2013.11.002

41. Hayes DF. HER2 and breast cancer-a phenomenal success story. N Engl J Med., 2019; 381:1284-1286. https://doi.org/10.1056/NEJMcibr1909386

42. Boku N. HER2-positive gastric cancer. Gastric Cancer. 2014; 17:1-12. https://doi.org/10.1007/s10120-013-0252-z

43. Takegawa N, Yonesaka K. HER2 as an emerging oncotarget for colorectal cancer treatment after failure of anti-epidermal growth factor receptor therapy. Clin Colorectal Cancer. 2017; 16:247-251. https://doi.org/10.1016/j.clcc.2017.03.001

44. Kiavue N, et al., ERBB3 mutations in cancer: biological aspects, prevalence and therapeutics. Oncogene. 2019. https://doi.org/10.1038/s41388-019-1001-5

45. Veikkolainen V, et al., Function of ERBB4 is determined by alternative splicing. Cell Cycle. 2011; 10:2647-2657. https://doi.org/10.4161/cc.10.16.17194

46. Junttila TT, et al., Cleavable ErbB4 isoform in estrogen receptor-regulated growth of breast cancer cells. Cancer Res., 2005; 65:1384-1393. https://doi.org/10.1158/0008-5472.CAN-04-3150

47. Wang Q, Yang S, Wang K, Sun SY. MET inhibitors for targeted therapy of EGFR TKI-resistant lung cancer. J Hematol Oncol., 2019; 12:63. https://doi.org/10.1186/s13045-019-0759-9

48. Cheng F, Guo D. MET in glioma: signaling pathways and targeted therapies. J Exp Clin Cancer Res., 2019; 38: 270. https://doi.org/10.1186/s13046-019-1269-x

49. Demkova L, Kucerova L. Role of the HGF/c-MET tyrosine kinase inhibitors in metastasic melanoma. Mol Cancer. 2018; 17:26. https://doi.org/10.1186/s12943-018-0795-z

50. Lam BQ, Dai L, Qin Z. The role of HGF/c-MET signaling pathway in lymphoma. J Hematol Oncol., 2016; 9: 135. https://doi.org/10.1186/s13045-016-0366-y

51. Bradley CA, et al. Targeting c-MET in gastrointestinal tumours: rationale, opportunities and challenges. Nat Rev Clin Oncol., 2017; 14:562-576. https://doi.org/10.1038/nrclinonc.2017.40

52. Cooper CS, et al., Molecular cloning of a new transforming gene from a chemically transformed human cell line. Nature. 1984; 311:29-33. https://doi.org/10.1038/311029a0

53. Nakamura T, et al., Molecular cloning and expression of human hepatocyte growth factor. Nature. 1989; 342:440-443. https://doi.org/10.1038/342440a0

54. Stoker M, Gherardi E, Perryman M, Gray J. Scatter factor is a fibroblastderived modulator of epithelial cell mobility. Nature. 1987; 327: 239-242. https://doi.org/10.1038/327239a0

55. Schmidt C, et al., Scatter factor/hepatocyte growth factor is essential for liver development. Nature. 1995; 373: 699-702. https://doi.org/10.1038/373699a0

56. Anestis A, Zoi I, Karamouzis MV. Current advances of targeting HGF/c-Met pathway in gastric cancer. Ann Transl Med., 2018; 6:247. https://doi.org/10.21037/atm.2018.04.42

57. Safaie QE, et al., The c-Met receptor: implication for targeted therapies in colorectal cancer. Tumour Biol., 2017; 39:1010. https://doi.org/10.1177/1010428317699118

58. Otte JM et al., Functional expression of HGF and its receptor in human colorectal cancer. Digestion. 2000; 61:237-246. https://doi.org/10.1159/000007764

59. Strosberg JR, et al., A phase II study of RO4929097 in metastatic colorectal cancer. Eur J Cancer. 2012; 48:997-1003. https://doi.org/10.1016/j.ejca.2012.02.056

60. Berlin J, et al., A randomized phase II trial of vismodegib versus placebo with FOLFOX or FOLFIRI and bevacizumab in patients with previously untreated metastatic colorectal cancer. Clin Cancer Res., 2013; 19:258-267. https://doi.org/10.1158/1078-0432.CCR-12-1800

61. Villalba M, Evans SR, Vidal-Vanaclocha F, Calvo A. Role of TGF-beta in metastatic colon cancer: it is finally time for targeted therapy. Cell Tissue Res., 2017; 370: 29-39. https://doi.org/10.1007/s00441-017-2633-9

62. Ghosh N, Hossain U, Mandal A, Sil PC. The Wnt signaling pathway: a potential therapeutic target against cancer. Ann NY Acad Sci., 2019; 1443:54-74. https://doi.org/10.1111/nyas.14027

63. Guinney J, et al., The consensus molecular subtypes of colorectal cancer. Nat Med., 2015; 21:1350-1356.