Expression of domains for protein-protein interaction of nucleotide excision repair proteins modifies cancer cell sensitivity to platinum derivatives and genomic stability

Single Nucleotide Polymorphisms in MiRNA Binding Sites of Nucleotide Excision Repair-Related Genes Predict Clinical Benefit of Oxaliplatin in FOLFOXIRI Plus Bevacizumab: Analysis of the TRIBE Trial

Background: The nucleotide excision repair (NER) pathway participates in platinum-induced DNA damage repair. Single nucleotide polymorphisms (SNPs) in miRNA-binding sites in the NER genes RPA2 and GTF2H1 are associated with the risk of colorectal cancer (CRC). Here, we analyzed whether RPA2 and GTF2H1 SNPs predict the efficacy of oxaliplatin in metastatic CRC (mCRC) patients. Patients and methods: Genomic DNA was extracted from blood samples from 457 patients with mCRC enrolled in the TRIBE trial, which compared first-line FOLFOXIRI plus bevacizumab (BEV) (n = 230, discovery cohort) and first-line FOLFIRI plus BEV (n = 227, control cohort). SNPs were analyzed by PCR-based direct sequencing. Results: In the FOLFOXIRI + BEV-treated cohort expressing wild-type KRAS, progression-free survival (PFS) was shorter for the RPA2 rs7356 C/C variant subgroup than the any T allele subgroup in univariate analysis (9.1 versus 13.3 months respectively, hazard ratio (HR) 2.32, 95% confidence interval (CI): 1.07–5.03, p = 0.020) and this remained significant in multivariable analysis (HR 2.97, 95%CI: 1.27–6.94, p = 0.012). A similar trend was observed for overall survival. In contrast, patients expressing mutant RAS and RPA2 rs7356 C/C variant had longer PFS with FOLFOXIRI + BEV than with FOLFIRI + BEV (12.1 versus 7.6 months, HR 0.23, 95%CI: 0.09–0.62, p = 0.002) but no superiority of FOLFOXIRI + BEV was observed for the RAS mutant, RPA2 rs7356 any T variant subgroup (11.7 versus 9.6 months, HR 0.77, 95%CI: 0.56–1.07, p = 0.12) or the RAS wild-type, RPA2 rs7356 C/C variant subgroup. Conclusion: RPA2 SNPs may serve as predictive and prognostic markers of oxaliplatin responsiveness in a RAS status-dependent manner in mCRC patients receiving FOLFOXIRI + BEV.

Shp2 confers cisplatin resistance in small cell lung cancer via an AKT-mediated increase in CA916798

The tyrosine phosphatase Shp2 is associated with tumorigenesis in small cell lung cancer (SCLC). However, the relationship between Shp2 and resistance to chemotherapy remains unclear. Here, we show that Shp2 plays an important role in inducing resistance to cisplatin-based chemotherapy via the SHP2-AKT-CA916798 pathway. In an SCLC cell line, overexpression of Shp2 induced cisplatin resistance and the increased expression of AKT, pAKT, pmTOR, and CA916798. Conversely, depletion of Shp2 in a cisplatin-resistant cell line via RNA interference increased cisplatin sensitivity and decreased AKT, pAKT, pmTOR, and CA916798 expression levels. Activation of AKT stimulated CA916798 expression and altered the level of Shp2. A mouse xenograft model verified the results obtained from the in vitro experiments. In addition, we collected and analyzed clinical SCLC specimens and found that Shp2 levels correlated with CA916798 expression in tumor tissues. Importantly, higher levels of Shp2 or CA916798 were associated with a poorer prognosis in SCLC patients who received chemotherapy. Together, our findings indicate that Shp2 induces cisplatin resistance in SCLC patients via the SHP2-AKT-CA916798 pathway. Therefore, Shp2 and CA916798 may be promising biomarkers for predicting resistance to chemotherapy and may function as targets for enhancing treatments.

Disruption of DNA repair in cancer cells by ubiquitination of a destabilising dimerization domain of nucleotide excision repair protein ERCC1

DNA repair pathways present in all cells serve to preserve genome stability, but in cancer cells they also act reduce the efficacy of chemotherapy. The endonuclease ERCC1-XPF has an important role in the repair of DNA damage caused by a variety of chemotherapeutic agents and there has been intense interest in the use of ERCC1 as a predictive marker of therapeutic response in non-small cell lung carcinoma, squamous cell carcinoma and ovarian cancer. We have previously validated ERCC1 as a therapeutic target in melanoma, but all small molecule ERCC1-XPF inhibitors reported to date have lacked sufficient potency and specificity for clinical use. In an alternative approach to prevent the repair activity of ERCC1-XPF, we investigated the mechanism of ERCC1 ubiquitination and found that the key region was the C-terminal (HhH)₂ domain which heterodimerizes with XPF. This ERCC1 region was modified by non-conventional lysine-independent, but proteasome-dependent polyubiquitination, involving Lys33 of ubiquitin and a linear ubiquitin chain. XPF was not polyubiquitinated and its expression was dependent on presence of ERCC1, but not vice versa. To our surprise we found that ERCC1 can also homodimerize through its C-terminal (HhH)₂ domain. We exploited the ability of a peptide containing this C-terminal domain to destabilise both endogenous ERCC1 and XPF in human melanoma cells and fibroblasts, resulting in reductions of up to 85% in nucleotide excision repair and near two-fold increased sensitivity to DNA damaging agents. We suggest that the ERCC1 (HhH)₂ domain could be used in an alternative strategy to treat cancer.

DNA repair gene polymorphisms in non-small-cell lung cancer patients treated with first-line platinum-containing chemotherapy

PURPOSE

Single nucleotide polymorphisms (SNPs) in the DNA repair genes are believed to contribute to the clinical outcome of patients receiving platinum-based chemotherapy. We investigated the impact of 2 SNPs of excision repair cross-complementation group 1 and 2 of xeroderma pigmentosum complementation group G on the outcome in patients with non-small-cell lung cancer (NSCLC) treated with platinum-based chemotherapy.

METHODS

Between October 2007 and March 2012, we collected 374 blood samples from consecutive patients registered in the TAILOR trial. Four SNPs (rs11615, rs3212986, rs17655, rs1047768) were genotyped using real-time polymerase chain reaction.

RESULTS

The rs11615 polymorphism was associated with histotype (p = 0.0123). No other correlations were found with clinical variables or with EGFR or KRAS mutational status. None of the SNPs had any impact on overall survival or progression-free survival.

CONCLUSIONS

The findings suggest that the investigated SNPs do not make any significant contribution to the outcome of NSCLC.

Nucleotide excision repair and response and survival to chemotherapy in colorectal cancer patients

Several new chemotherapeutic agents have become available for the treatment of colorectal cancer, which has led to increased complexity in treatment planning. Treatment decision making for individual patients could be facilitated if guided by predictive and prognostic markers. As most cytotoxic drugs induce DNA damage, the DNA damage repair pathways hold potential for yielding such biomarkers. Here, we review the current evidence of a possible involvement of the nucleotide excision repair pathway in the efficacy of chemotherapeutic agents used in the treatment of colorectal cancer. Although a large number of studies have been conducted, they are generally of moderate size and heterogeneous in design. Up to date no firm conclusions can be drawn to translate these results into the clinic. We recommend further comprehensive investigations of the nucleotide excision repair pathway in large patient studies that include both discovery and validation cohorts.

Novel strategies for molecular targeting to cancer

This editorial draws attention to the work published by CEPP in 2014-2015 on mechanisms underlying cancer drug resistance, invasion and metastasis. Genetic, genomic and immunological changes in platinum drug resistance and new drug candidates for cancer metastasis are highlighted. Attention is paid to the Epimedium plant drug icariin in glioblastoma invasion, the plant Avicennia marina bioactive compound Naphtho[1,2-b]furan-4,5-dione in breast cancer metastasis, the PI3K inhibitor BEZ235 in colon cancer stem cells, the histone methyltransferase EZH1 inhibitor GSK343 in cervical cancer, and vitamin D3 in prostate cancer.