EGFR gene copy number as a predictive biomarker for resistance to anti-EGFR monoclonal antibodies in metastatic colorectal cancer treatment: a meta-analysis

The use of SP/Neurokinin-1 as a Therapeutic Target in Colon and Rectal Cancer

Different studies have highlighted the role of Substance P / Neurokinin 1 Receptor (SP/NK-1R) axis in multiple hallmarks of cancer including cell transformation, proliferation, and migration as well as angiogenesis and metastasis of a wide range of solid tumors including colorectal cancer. Until now, the selective high-affinity antagonist of human SP/NK1-R aprepitant (Emend) has been authorized by the Food and Drug Administration as a low dosage medication to manage and treat chemotherapy-induced nausea. However, increasing evidence in recent years support the potential utility of high doses of aprepitant as an antitumor agent and thus, opening the possibility to the pharmacological repositioning of SP/NK1-R antagonists as an adjuvant therapy to conventional cancer treatments. In this review, we summarize current knowledge on the molecular basis of colorectal cancer as well as the pathophysiological importance of SP/NK1-R and the potential utility of SP/NK-1R axis as a therapeutic target in this malignancy.

Targeting BRAF and RAS in Colorectal Cancer

Simple Summary

In colorectal cancer, mutations of the KRAS and BRAF genes are quite common and can contribute to the activation of cell signaling pathways that lead to cell proliferation and differentiation. These processes promote cancer growth, and in some cases, they may cause cells to develop resistance to certain types of treatment, notably EGFR inhibitors. We summarize recent knowledge regarding the effects of KRAS and BRAF mutations in the setting of colorectal cancer and discuss the new therapies under development.

Abstract

Colorectal cancer (CRC) is still one of the most frequent forms of cancer in the world in terms of incidence. Around 40% of CRC patients carry a mutation of the Kirsten rat sarcoma (KRAS) gene, while 10% have a mutation in the B-Raf proto-oncogene serine/threonine kinase (BRAF) gene. These mutations are responsible for dysregulation of the mitogen-associated protein kinase (MAPK) pathway, leading to the proliferation, differentiation, angiogenesis, and resistance to apoptosis of cells. Activation of the MAPK pathway results in adaptive therapeutic resistance, rendering EGFR inhibitors ineffective. This review aims to highlight the recent findings that have improved our understanding of KRAS and BRAF mutations in colorectal cancer and to describe new targeted therapies, used alone or in combination.

Use of Gefitinib in EGFR-Amplified Refractory Solid Tumors: An Open-Label, Single-Arm, Single-Center Prospective Pilot Study

BACKGROUND

Treatment options for patients with chemotherapy-refractory solid tumors are limited.

OBJECTIVE

We conducted an open-label, single-arm, single-center phase II trial to evaluate the efficacy and safety of gefitinib in patients with chemotherapy-refractory solid tumors and EGFR amplification or sensitivity to an EGFR inhibitor identified through a drug-screening platform with patient-derived tumor cells (PDCs).

PATIENTS AND METHODS

EGFR amplification was detected by targeted sequencing. Sensitivity to an EGFR inhibitor was established in chemical screening using PDCs. Gefitinib (250 mg daily) was administered continuously in 28-day cycles until the occurrence of disease progression, unacceptable toxicity, or death due to any cause. The primary endpoint was the objective response rate (ORR).

RESULTS

In total, 15 patients were assigned to the present study. The most common tumor type was glioblastoma multiforme (n = 9, 60%), followed by gastric cancer (n = 3, 20%), anal squamous cancer, rectal cancer, and sarcoma (each n = 1, 6.7%). Among 13 evaluable patients, one patient had a partial response and five had stable disease, with an ORR of 7.7% and a disease control rate of 46.1%. The median progression-free survival was 2.1 months (95% confidence interval [CI] 0.77-3.43). The most common adverse events were diarrhea (26.7%) and skin rash (26.7%).

CONCLUSION

Gefitinib demonstrated modest anti-tumor activity and a manageable safety profile in chemotherapy-refractory solid tumors with EGFR amplification or sensitivity to an EGFR inhibitor identified through a drug-screening platform with PDCs. CLINICALTRIALS.

GOV IDENTIFIER

NCT02447419.

Guardant360 Circulating Tumor DNA Assay Is Concordant with FoundationOne Next-Generation Sequencing in Detecting Actionable Driver Mutations in Anti-EGFR Naive Metastatic Colorectal Cancer

BACKGROUND

Direct comparisons between Guardant360 (G360) circulating tumor DNA (ctDNA) and FoundationOne (F1) tumor biopsy genomic profiling in metastatic colorectal cancer (mCRC) are limited. We aim to assess the concordance across overlapping genes tested in both F1 and G360 in patients with mCRC.

MATERIALS AND METHODS

We retrospectively analyzed 75 patients with mCRC who underwent G360 and F1 testing. We evaluated the concordance among gene mutations tested by both G360 and F1 among three categories of patients: untreated, treated without, and treated with EGFR inhibitors, while considering the clonal and/or subclonal nature of each genomic alteration.

RESULTS

There was a high rate of concordance in APC, TP53, KRAS, NRAS, and BRAF mutations in the treatment-naive and non-anti-EGFR-treated cohorts. There was increased discordance in the anti-EGFR treated patients in three drivers of anti-EGFR resistance: KRAS, NRAS, and EGFR somatic mutations. Based on percentage of ctDNA, discordant somatic mutations were mostly subclonal instead of clonal and may have limited clinical significance. Most discordant amplifications noted on G360 showed the magnitude below the top decile, occurred in all three cohorts of patients, and were of unknown clinical significance. Serial ctDNA in anti-EGFR treated patients showed the emergence of multiple new alterations that affected the EGFR pathway: EGFR and RAS mutations and MET, RAS, and BRAF amplifications.

CONCLUSION

G360 Next-Generation Sequencing platform may be used as an alternative to F1 to detect targetable somatic alterations in non-anti-EGFR treated mCRC, but larger prospective studies are needed to further validate our findings.

IMPLICATIONS FOR PRACTICE

Genomic analysis of tissue biopsy is currently the optimal method for identifying DNA genomic alterations to help physicians target specific genes but has many disadvantages that may be mitigated by a circulating free tumor DNA (ctDNA) assay. This study showed a high concordance rate in certain gene mutations in patients who were treatment naive and treated with non-anti-EGFR therapy prior to ctDNA testing. This suggests that ctDNA genomic analysis may potentially be used as an alternative to tumor biopsy to identify appropriate patients for treatment selection in mCRC, but larger prospective studies are needed to further validate concordance among tissue and ctDNA tumor profiling.

Clinical Impact of PI3K/BRAF Mutations in RAS Wild Metastatic Colorectal Cancer: Meta-analysis Results

BACKGROUND

Understanding the molecular mechanisms of colorectal cancer has evolved during the last decade ushering the era of personalized medicine. Alteration of BRAF and PI3K is common in colorectal cancer, and can affect several signaling pathways including EGFR (epidermal growth factor receptor). The aim of this meta-analysis is to evaluate the clinical role of PI3K and BRAF mutations in patients with KRAS wild-type metastatic colorectal cancer (MCRC) receiving an EGFR monoclonal antibody (anti-EGFR) inhibitor as first-line therapy.

METHODS

A literature search was performed to identify studies exploring the association between PI3K/BRAF mutations and clinical outcomes of KRAS wild-type mCRC patients treated with anti-EGFR as a first-line therapy. The primary clinical outcome was overall response rate (ORR). The secondary outcomes included progression-free survival (PFS) and overall survival (OS). The pooled relative risk (RR) or hazard ratio (HR) was estimated by using fixed-effect model or random effect model according to heterogeneity between studies.

RESULTS

Ten studies with 1470 mCRC patients (357 for PI3K studies and 1113 from BRAF studies) met selection criteria. We observed a trend towards lower ORR in patients with PI3K mutations (3 studies, 357 patients; ORR = 14.3% in mutant-type PI3K vs. 52.4% in wild-type PIK3CA [95% CI - 0.12-0.02]; P = 0.13). Patients with mutant-type PI3K have significant shorter PFS (3 studies, 357 patients, 3.8 vs. 4.15 months, HR = 1.36; [95% CI 1.04-1.77]; P = 0.02]), and OS (3 studies, 357 patients, 14.17 vs. 16.3 months, HR = 1.50; [95% CI 1.14-1.97]; P = 0.004) compared to those with wild PI3K. For BRAF, patients with mutant type have significantly lower ORR (7 studies, 1113 patients; ORR = 33% vs. 39%; [95% CI - 0.16-0.01]; P = 0.03), shorter PFS (5 studies, 814 patients, 3.9 vs. 5.7 months, HR = 1.72; [95% CI 1.47-2.01]; P = 0.00001), and shorter OS (4 studies, 766 pts., 9.1 vs. 18.9 months, HR = 1.22; [95% CI 1.04-1.44]; P = 0.01) compared to those with wild-type.

CONCLUSION

This analysis suggests that patients with mCRC and either PI3K or BRAF mutation may have a lower response and worse outcome when treated with anti-EGFR in the first line. Given their worse outcome, routine testing for BRAF and PI3K mutational status should be considered. Novel therapeutic approaches are needed for patients with mutations in BRAF or PI3K.

New frontiers in the treatment of colorectal cancer: Autophagy and the unfolded protein response as promising targets

Colorectal cancer (CRC), despite numerous therapeutic and screening attempts, still remains a major life-threatening malignancy. CRC etiology entails both genetic and environmental factors. Macroautophagy/autophagy and the unfolded protein response (UPR) are fundamental mechanisms involved in the regulation of cellular responses to environmental and genetic stresses. Both pathways are interconnected and regulate cellular responses to apoptotic stimuli. In this review, we address the epidemiology and risk factors of CRC, including genetic mutations leading to the occurrence of the disease. Next, we discuss mutations of genes related to autophagy and the UPR in CRC. Then, we discuss how autophagy and the UPR are involved in the regulation of CRC and how they associate with obesity and inflammatory responses in CRC. Finally, we provide perspectives for the modulation of autophagy and the UPR as new therapeutic options for CRC treatment.

Potential biomarkers for anti-EGFR therapy in metastatic colorectal cancer

Anti-epidermal growth factor receptor (EGFR) therapy has established efficacy in metastatic colorectal cancer, but a significant number of patients do not respond to such treatment. Recently, various biomarkers were reported to be useful in predicting resistance to anti-EGFR. All the potential biomarkers predicting resistance to anti-EGFR are reviewed herein from five aspects. First, upstream molecules, including epiregulin (EREG) and amphiregulin (AREG), might play different roles according to their abnormal levels in tumor tissue and serum. Second, the EGFR amplification and distinct polymorphisms may have roles in identifying patients for initial anti-EGFR mAbs therapy, while rare EGFR mutations have limited predictive values. Third, among the downstream molecularly related factors, rat sarcoma viral oncogene (Ras) has been identified as a successful predictor, while B-Raf proto-oncogene (BRAF) is considered as a prognostic factor rather than a predictor. Fourth, among the molecular bypass pathway components, phosphatidylinositol 3-kinase (PI3K) and phosphatase and tensin homolog (PTEN) may be potential biomarkers in the future, while activation of hepatocyte growth factor (HGF)/c-Met signaling confers resistance to anti-EGFR therapy. Fifth, many microRNAs and additional molecular biomarkers are promising in predicting the efficacy of anti-EGFR therapy. Applications of multiple biomarkers are more effective than the use of a single biomarker in selecting patients who might benefit from cetuximab- or panitumumab-based treatments. Comprehensive molecular analyses of the EGFR signaling pathways should be considered in the future. Subsequent prospective trials will be required to further confirm the clinical utility of these biomarkers.

Expression of the chemokine CXCL14 and cetuximab-dependent tumour suppression in head and neck squamous cell carcinoma

Cetuximab, a monoclonal antibody against the epidermal growth factor receptor (EGFR), has been successfully used to treat some patients with colorectal cancer and those with head and neck squamous cell carcinoma (HNSCC). For the effective treatment, it is essential to first identify cetuximab-responsive patients. The level of EGFR expression and/or the presence of mutations in signalling molecules downstream of the EGFR pathway have been reported to be determining factors for cetuximab responsiveness in colorectal cancer patients; however, limited data have been reported for HNSCC patients. We previously reported that the chemokine CXCL14 exhibits tumour-suppressive effects against xenografted HNSCC cells, which may be classified into two groups, CXCL14-expressing and non-expressing cells under serum-starved culture conditions. Here we employed CXCL14-expressing HSC-3 cells and CXCL14-non-expressing YCU-H891 cells as representatives of the two groups and compared their responses to cetuximab and their CXCL14 expression under various conditions. The growth of xenografted tumours initiated by HSC-3 cells, which expressed CXCL14 in vivo and in vitro, was suppressed by the injection of cetuximab into tumour-bearing mice; however, neither the expression of the chemokine nor the cetuximab-dependent suppression of xenograft tumour growth was observed for YCU-H891 cells. Both types of cells expressed EGFR and neither type harboured mutations in signalling molecules downstream of EGFR that have been reported in cetuximab-resistant colon cancer patients. The inhibition of the extracellular signal-regulated kinase (ERK) signalling increased the levels of CXCL14 messenger RNA (mRNA) in HSC-3 cells, but not in YCU-H891 cells. We also observed that the CXCL14 promoter region in YCU-H891 cells was hypermethylated, and that demethylation of the promoter by treatment with 5-aza-2′-deoxycytidine restored CXCL14 mRNA expression and in vivo cetuximab-mediated tumour growth suppression. Finally, we observed in vivo tumour growth suppression when YCU-H891 cells were engineered to express CXCL14 ectopically in the presence of doxycycline. These results indicate that CXCL14 expression may be a good predictive biomarker for cetuximab-dependent tumour suppression.

Biomarkers predicting resistance to epidermal growth factor receptor-targeted therapy in metastatic colorectal cancer with wild-type KRAS

EGFR pathway is an important therapeutic target in human tumors, including metastatic colorectal cancer (mCRC). The advent of EGFR-targeted monoclonal antibodies panitumumab and cetuximab has generated promise for the treatment of mCRC and has largely improved patients' progression-free survival (PFS) and overall survival (OS). However, treatment with anti-EGFR monoclonal antibodies is only effective in a subset of mCRC patients with wild-type KRAS. This indicates that there are other factors affecting the efficacy of anti-EGFR monoclonal antibodies. Existing studies have demonstrated that among colorectal cancer patients with wild-type KRAS, harboring mutations of BRAF, PIK3CA, NRAS, or PTEN-null may demonstrate resistance to anti-EGFR-targeted therapy, and biomarkers detection can provide better-personalized treatment for mCRC patients. How to identify and reverse the secondary resistance to anti-EGFR monoclonal antibody therapy is also another great challenge to improve the anti-EGFR efficacy in wild-type KRAS mCRC patients. Finally, both of the molecular mechanisms of response and acquired resistance would be important for the directions of future research. This review focuses on how to further improve the predictive value of anti-EGFR therapies and how to also try and avoid futile treatment for wild-type KRAS colorectal cancer patients.

Acquired resistance to anti-EGFR mAb ICR62 in cancer cells is accompanied by an increased EGFR expression, HER-2/HER-3 signalling and sensitivity to pan HER blockers

BACKGROUND

The human epidermal growth factor receptor (EGFR) is an important target for cancer treatment. Currently, only the EGFR antibodies cetuximab and panitumumab are approved for the treatment of patients with colorectal cancer. However, a major clinical challenge is a short-term response owing to development of acquired resistance during the course of the treatment.

METHODS

In this study, we investigated the molecular mechanisms underlying development of acquired resistance in DiFi colorectal cancer cells to the anti-EGFR mAb ICR62 (termed DiFi62) and to the small molecule tyrosine kinase inhibitor (TKI) gefitinib (termed DiFiG) using a range of techniques.

RESULTS

Compared with the findings from parental DiFi and DiFiG cells, development of acquired resistance to anti-EGFR mAb ICR62 in DiFi62 cells was accompanied by an increase in cell surface EGFR and increased phosphorylation of HER-2 and HER-3. Interestingly, DiFi62 cells also acquired resistance to treatment with anti-EGFR mAbs cetuximab and ICR61, which bind to other distinct epitopes on the extracellular domain of EGFR, but these cells remained equally sensitive as the parental cells to treatment with pan-HER inhibitors such as afatinib.

CONCLUSIONS

Our results provide a novel mechanistic insight into the development of acquired resistance to EGFR antibody-based therapy in colorectal cancer cells and justify further investigations on the therapeutic benefits of pan-HER family inhibitors in the treatment of colorectal cancer patients once acquired resistance to EGFR antibody-based therapy is developed.