Oncogenic fingerprint of epidermal growth factor receptor pathway and emerging epidermal growth factor receptor blockade resistance in colorectal cancer

Precision medicine for metastatic colorectal cancer: an evolving era

Introduction: Metastatic colorectal cancer (CRC) remains a dilemma for cancer researchers with an increasing incidence in the younger patient population. Until the last decade, limited therapeutic options were available for metastatic CRC patients leading to relatively poor clinical outcomes.Areas covered: With advances in genome sequencing technology and reductions in the cost of next-generation sequencing, molecular profiling has become more accessible for cancer researchers and clinical investigators, which has furthered our understanding of the molecular behavior of CRC. This progress has recently translated into significant advances in molecular-based therapeutics and led to the development of new target-specific agents in metastatic CRC patients. In this review article, we extensively elaborate on genomic alterations seen in CRC patients including, but not limited to, EGFR, MMR, BRAF, HER2, NTRKs, FGFR, BRCA1/2, PALB2, POLE, and POLD1 genes, all of which are potentially actionable by either an FDA-approved agent or in a clinical trial setting.Expert opinion: We strongly recommend molecular profiling in metastatic CRC patients during the early course of their disease, as this may provide therapeutic and prognostic information that can guide clinicians to practice precision medicine. Patients with potentially actionable genes should be considered for targeting agents based on molecular alterations.

miR-15b-5p resensitizes colon cancer cells to 5-fluorouracil by promoting apoptosis via the NF-κB/XIAP axis

Drug resistance, which is closely correlated with an imbalance in apoptosis, endows colorectal cancer (CRC) with enhanced progression capacity irrespective of the treatment with therapeutics. We report that miR-15b-5p is a tumor suppressor whose level is globally decreased in CRC cells and tissues. Over-expression of miR-15b-5p not only promoted 5-fluorouracil (5-FU)-induced cellular apoptosis but also reversed the chemoresistance of 5-FU in vitro and in vivo. As a key mediator of inflammation-induced cancer, miR-15b-5p enhances these therapeutic effects are mainly attributed to targeting of the NF-κB signaling pathway through negative regulation of NF-κB1 and one of its kinase complexes IKK-α. miR-15b-5p mediates NF-ĸB regulation by targeting the anti-apoptosis protein XIAP in vitro. Together, these results establish an axis of miR-15b-mediated apoptosis regulation, which reverses chemoresistance and suppresses CRC progression. These findings suggest that miR-15b-5p may be a potential agent for CRC treatment, particularly for 5-FU-resistant CRC.

Antitumor activity of high-dose pulsatile gefitinib in non-small-cell lung cancer with acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have demonstrated efficacy in the treatment of advanced non-small cell lung cancer (NSCLC). However, their clinical efficacy is limited by acquired resistance. Drug resistance may be mediated by EGFR transduction, and a number of clinical trials have demonstrated that high-dose pulsatile TKIs may be effective at treating patients with acquired resistance, though their underlying mechanisms of action remain unknown. The aim of the present study was to investigate the antitumor activity of high-dose pulsatile gefitinib in NSCLC model cell lines, namely the EGFR-TKI-sensitive cell line PC9, as a control group, and the EGFR-TKI-resistant cell lines H1975 and H1650. The cell lines were administered with different doses of gefitinib and cell viability was measured using an MTT assay. Cell apoptosis and cycling were also determined by flow cytometry and the expression of phospho (p)-EGFR, EGFR, p-AKT and AKT were measured by western blot analysis. It was observed that the apoptotic rate of H1975 cells treated with high-dose pulsatile gefitinib significantly increased, while levels of p-EGFR and p-AKT were decreased. However, there was no significant difference in the apoptotic rate or level of p-AKT in gefitinib-treated H1650 cells, while p-EGFR levels decreased. By contrast, the EGFR-TKI-sensitive cell line PC9 exhibited sensitivity to gefitinib. It was demonstrated that the apoptosis rates were markedly increased when treated with high dose pulsatile gefitinib in PC9 cell line, while a decrease was noted in p-EGFR and p-AKT. These data suggest that high-dose pulsatile gefitinib treatment may overcome acquired resistance in NSCLC, though its efficacy is dependent on the type of drug resistance mutation(s) present. Furthermore, high-dose pulsatile gefitinib may inhibit tumor growth and induce cell apoptosis by blocking the EGFR signaling pathway. Therefore, if the signaling pathways involved in drug resistance are not activated by the EGFR gene, high-dose pulsatile gefitinib may have little efficacy in the treatment of NSCLC.