HER2+ mCRC patients with exon 20 R784G substitution mutation do not respond to the cetuximab therapy

Poly (ADP-Ribose) Polymerase 1 Induces Cyclic GMP-AMP Synthase-stimulator of Interferon Genes Pathway Dysregulation to Promote Immune Escape of Colorectal Cancer Cells

Colorectal cancer (CRC) ranks third globally in cancer incidence and mortality, posing a significant human concern. Recent advancements in immunotherapy are noteworthy. This study explores immune modulation for CRC treatment. Initially targeting poly (ADP-ribose) polymerase 1 (PARP-1), a gene overexpressed in CRC tissues per The Cancer Genome Atlas, we examined its correlation with immune cell infiltration using the Tumor Immune Estimation Resource tool. Quantitative reverse transcription polymerase chain reaction assessed PARP-1 mRNA and inflammation-related gene expression in tumor tissues and cells. Assessing CD8 + T-cell proliferation and cytotoxicity towards HCT116 cells involved carboxyfluorescein diacetate succinimidyl ester and lactate dehydrogenase kits. Chemotaxis was gauged using a Transwell system in a CD8 + T-cell coculture setup, with immunofluorescence revealing cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING) levels in HCT116 cells. Enzyme-linked immunosorbent assay kits measured CD8 + T-cell cytokine secretion. The findings suggested that PARP-1 was overexpressed in CRC tissues and cells and this overexpression was positively correlated with Treg cell infiltration. Overexpression of PARP-1 could significantly reduce the proportion of cGAS and STING-positive cells in HCT116 cells, dampen the proliferation, tumor-killing capacity, and chemotaxis of CD8 + T cells, and inhibit the secretion of related cytokines. The introduction of STING agonists could reverse the effects caused by overexpressed PARP-1. In vivo experiments affirmed the independent anti-tumor effects of PARP-1 inhibitors and STING agonists, synergistically inhibiting tumor growth. Silencing PARP-1 in HCT116 cells potentially boosts CD8 + T-cell activity against these cells through the cGAS-STING pathway.

The predictive role of ERBB2 point mutations in metastatic colorectal cancer: A systematic review

ERBB2 amplification is a driver oncogenic alteration in many cancers and it has recently been incorporated among therapeutically actionable biomarkers also in metastatic colorectal cancer (mCRC). In contrast, the role of ERBB2 point mutations, which are detectable in up to 3% of CRC patients, remains to be assessed. In this systematic review, we collected preclinical and clinical data addressing the role of ERBB2 point mutations in mCRC patients as a predictive biomarker for anti-EGFR and anti-HER2 targeted agents, and as mechanism of acquired resistance to ERBB2 amplified mCRC treated with any anti-HER2 regimen. In both preclinical and clinical studies, most ERBB2 point mutations were associated with resistance to anti-EGFR agents, particularly L755S and R784G, which occur in the HER2 protein kinase domain. No ERBB2 mutation was associated with tumor response to HER2-targeted agents in mCRC patients, although signals of activity were observed in preclinical models. Eight ongoing clinical trials are underway to test different anti-HER2 treatments in ERBB2 mutant mCRC. Several reports documented the emergence of ERBB2 mutations in the circulating tumor DNA (ctDNA) of ERBB2 amplified mCRC progressing to anti-HER2 agents, thus hinting a role in acquired resistance.

Liquid biopsy to detect resistance mutations against anti-epidermal growth factor receptor therapy in metastatic colorectal cancer

Colorectal cancer (CRC) is a major cause of mortality worldwide, associated with a steadily growing prevalence. Notably, the identification of KRAS, NRAS, and BRAF mutations has markedly improved targeted CRC therapy by affording treatments directed against the epidermal growth factor receptor (EGFR) and other anti-angiogenic therapies. However, the survival benefit conferred by these therapies remains variable and difficult to predict, owing to the high level of molecular heterogeneity among patients with CRC. Although classification into consensus molecular subtypes could optimize response prediction to targeted therapies, the acquisition of resistance mutations to targeted therapy is, in part, responsible for the lack of response in some patients. However, the acquisition of such mutations can induce challenges in clinical practice. The utility of liquid biopsy to detect resistance mutations against anti-EGFR therapy has recently been described. This approach may constitute a new standard in the decision algorithm for targeted CRC therapy.

SOX8 promotes cetuximab resistance via HGF/MET bypass pathway activation in colorectal cancer

AIM

Cetuximab is an essential drug for the treatment of wild-type K-RAS colorectal cancer (CRC). It improves the overall survival of patients. However, acquired resistance prevents its clinical efficacy. Tumor heterogeneity may be a nonnegligible reason for cetuximab resistance. We attempted to explore the corresponding molecular mechanism.

METHODS

Cetuximab-resistant CRC cell RKO and cetuximab-sensitive CRC cell Caco-2 were applied in this study. Cells were centrifuged to determine the concentration in the culture supernatant (CS). MTT, EdU, and colony formation assays were utilized to evaluate cell survival and proliferation. Chromatin immunoprecipitation (ChIP) and promoter-luciferase reporter assays were employed to confirm the direct binding of transcription factors. Western blot and reverse transcription-polymerase chain reaction (RT-PCR) assays were used to detect the expression of molecular markers in the pathway.

RESULTS

Hepatocyte growth factor (HGF) was up-regulated in RKO cell culture supernatant and induced cetuximab resistance in Caco-2 cells. SRY-Box Transcription Factor 8 (SOX8) bound to the promoter sequence of HGF. HGF activated the HGF/MET bypass pathway and induced cetuximab resistance in Caco-2 cells.

CONCLUSION

The SOX8/HGF/MET axis played a crucial role in the communication between cetuximab-resistant cells and cetuximab-sensitive cells, inducing treatment resistance.

Impact of EGFR and EGFR ligand expression on treatment response in patients with metastatic colorectal cancer

Up to 50% of patients with colorectal cancer (CRC) have either synchronous or metachronous hepatic metastases in the course of their disease. Patients with metastatic CRC (mCRC) whose tumors express wild-type KRAS benefit from treatment with monoclonal antibodies (such as cetuximab or panitumumab) that target the epidermal growth factor receptor (EGFR). However, the therapeutic response to these antibodies is variable, and further predictive models are required. The present study examined whether expression of different EGFRs or their ligands in tumors was associated with the response to cetuximab treatment. Tumor tissues, collected during liver resection in 28 patients with mCRC, were analyzed. The protein expression levels of EGFR/ErbB1, ErbB2, ErbB3 and the EGFR ligands heregulin and amphiregulin were determined using Luminex 200^® and enzyme-linked immunosorbent assays. Computed tomography or magnetic resonance imaging was performed 4 weeks before and 6-8 weeks after treatment with cetuximab. Response to treatment was assessed using the response evaluation criteria for solid tumors (RECIST). The association between the protein expression levels of different EGFRs and their ligands with RECIST criteria was then analyzed to determine whether these protein levels could predict the treatment response to cetuximab. A total of 12 patients exhibited a partial response, 9 exhibited stable disease and 7 exhibited progressive disease after cetuximab therapy according to RECIST. The expression levels of EGFRs (EGFR/ErbB1, ErbB2 and ErbB3) and their ligands (heregulin and amphiregulin) were not significantly associated with the response to cetuximab therapy. Therefore, the present study indicated that EGFR or EGFR ligand expression did not predict treatment response in patients with CRC with liver metastases following cetuximab therapy.

Cellular Mechanisms Accounting for the Refractoriness of Colorectal Carcinoma to Pharmacological Treatment

Simple Summary

Colorectal cancer (CRC) causes a high number (more than 800,000) of deaths worldwide each year. Better methods for early diagnosis and the development of strategies to enhance the efficacy of the therapeutic approaches used to complement or substitute surgical removal of the tumor are urgently needed. Currently available pharmacological armamentarium provides very moderate benefits to patients due to the high resistance of tumor cells to respond to anticancer drugs. The present review summarizes and classifies into seven groups the cellular and molecular mechanisms of chemoresistance (MOC) accounting for the failure of CRC response to the pharmacological treatment.

Abstract

The unsatisfactory response of colorectal cancer (CRC) to pharmacological treatment contributes to the substantial global health burden caused by this disease. Over the last few decades, CRC has become the cause of more than 800,000 deaths per year. The reason is a combination of two factors: (i) the late cancer detection, which is being partially solved by the implementation of mass screening of adults over age 50, permitting earlier diagnosis and treatment; (ii) the inadequate response of advanced unresectable tumors (i.e., stages III and IV) to pharmacological therapy. The latter is due to the existence of complex mechanisms of chemoresistance (MOCs) that interact and synergize with each other, rendering CRC cells strongly refractory to the available pharmacological regimens based on conventional chemotherapy, such as pyrimidine analogs (5-fluorouracil, capecitabine, trifluridine, and tipiracil), oxaliplatin, and irinotecan, as well as drugs targeted toward tyrosine kinase receptors (regorafenib, aflibercept, bevacizumab, cetuximab, panitumumab, and ramucirumab), and, more recently, immune checkpoint inhibitors (nivolumab, ipilimumab, and pembrolizumab). In the present review, we have inventoried the genes involved in the lack of CRC response to pharmacological treatment, classifying them into seven groups (from MOC-1 to MOC-7) according to functional criteria to identify cancer cell weaknesses. This classification will be useful to pave the way for developing sensitizing tools consisting of (i) new agents to be co-administered with the active drug; (ii) pharmacological approaches, such as drug encapsulation (e.g., into labeled liposomes or exosomes); (iii) gene therapy interventions aimed at restoring the impaired function of some proteins (e.g., uptake transporters and tumor suppressors) or abolishing that of others (such as export pumps and oncogenes).

HER2 as a Predictive Biomarker and Treatment Target in Colorectal Cancer

The prognosis of metastatic colorectal cancer (mCRC) is poor. Cetuximab and panitumumab, 2 anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (mAbs), improve the overall survival of patients with RAS wild-type mCRC. However, not all patients with RAS wild-type mCRC will respond to anti-EGFR mAbs. Several retrospective trials suggest that human epidermal growth factor receptor 2 (HER2) amplification could be a predictive biomarker of resistance to anti-EGFR mAbs in patients with metastatic RAS and RAF wild-type mCRC. Dual HER2 inhibition with trastuzumab plus lapatinib or pertuzumab has shown promising preliminary anti-tumoral efficacy in RAS wild-type mCRC. Although these findings need to be confirmed in randomized trials, the data strongly support that HER2 is an actionable gene in CRC and provide the scientific rationale to test HER2 status on a routine basis in this disease. In this review, we discuss the predictive value of HER2 activation in CRC as well as its potential role as a treatment target.

The HER2 S310F Mutant Can Form an Active Heterodimer with the EGFR, Which Can Be Inhibited by Cetuximab but Not by Trastuzumab as well as Pertuzumab

G309 or S310 mutations on the HER2 extracellular domain II induce receptor activation. Clinically, S310F is most frequent among HER2 extracellular domain mutations and patients with the S310F mutation without HER2 amplification responded to trastuzumab with or without the pertuzumab combination. However, the ability of S310F mutant to form homodimers or heterodimers with wild-type HER2 and other HER receptors, or their reactivity to trastuzumab and pertuzumab treatments, has not been reported. We overexpressed S310F as well as G309A, G309E and S310Y HER2 mutants and tested their reactivity to trastuzumab and pertuzumab. All mutants reacted to trastuzumab, but S310F mutant did not react to pertuzumab along with S310Y or G309E mutants. Thereafter, we tested the effects of trastuzumab and pertuzumab on 5637 cell line expressing both wild-type HER2 and S310F mutant. The ligand-independent HER2 homodimerization blocking antibody, trastuzumab, did not inhibit the activation of the HER2 receptor, suggesting that the S310F HER2 mutant did not form homodimers or heterodimers with wild-type HER2. Because 5637 cells overexpressed the EGFR, the effects of cetuximab and gefitinib were determined, and both inhibited the activation of HER2 and significantly reduced cell growth. Because pertuzumab did not inhibit the phosphorylation of HER2 while it bound to wild-type HER2, EGFR-mediated phosphorylation is expected to occur on the S310F mutant. To confirm whether the S310F mutant HER2 retained its affinity to the EGFR, single molecule interaction analyses using TIRF microscopy were performed, which showed that S310F mutant successfully formed complexes with EGFR. In conclusion, HER2 S310F mutant can form an active heterodimer with the EGFR and it can be inhibited by cetuximab, but not by trastuzumab in combination with pertuzumab.