| Rectal cancer accounts for approximately 30% of all colorectal malignancies, a high proportion of patients have relapse within five years and the prognosis is therefore poor. The treatment choice is concurrent chemoradiotherapy combined with surgery, but an important issue was the broad variety in tumor response, acute adverse events and survival time. This study sought to establish a gene signature for predicting treatment response in local advanced rectal cancer patients received preoperative chemoradiotherapy and explore the molecular mechanisms and identify genetic variations that may be associated with acute adverse events and survival time in rectal cancer patients treated with postoperative chemoradiotherapy.Tumor tissue samples were collected from eighty-one patients in discovery stage and forty-five patients in validation stage with local advanced rectal cancer. Gene expression microarrays were conducted between good response and poor response patients in discovery stage. In a training set of forty-four samples, good response and poor response patients showed significantly different expression for 179 probes (P< 0.05 and Fold Change≥2.0). The ability to predict response was evaluated with different gene sets and generated a top twenty-gene signature. We used the signature to predict chemoradiotherapy response in thirty-seven patients with intermediate response, which were divided into two groups with significant difference in the proportion of residual cancer cells after chemoradiotherapy and disease-free survival (P= 0.0377 and P= 0.0004). We tested the response predictive performance of the twenty-gene signature in a validation cohort using receiver operating characteristic analysis and the AUC was 0.815 (95%Cl= 0.662-0.968; P= 0.0173).By further data analysis, we found that high ZNF37A expression was associated with good response to chemoradiotherapy and a good prognosis in rectal cancer patients. By in vivo and in vitro experiments in cell lines with ZNF37A knockdown or overexpression, we demonstrated that ZNF37A overexpression significantly enhanced sensitivity to chemoradiotherapy and led to increased apoptosis, whereas knockdown ZNF37A expression obtained the opposite results. ZNF37A was a transcriptional repressor, and by co-expression analysis, ChIP-qPCR and Reporter Assay, We found ZNF37A could repress the transcription of TNFRSF6B by directly binding to its promoter, and after knocking down TNFRSF6B expression in cell lines with low-level expression of ZNF37A, treatment-resistant cells recovered sensitive to treatment.CAP-based chemoradiotherapy for rectal cancer patients is with a broad variety in clinical outcomes and genetic variations may play an important role. MicroRNAs are small non-coding RNAs, the most critical region for binding and repression of mRNA by a miRNA are positions 2-8 from the 5’end of the miRNA, referred to as the seed region. To investigate whether single nucleotide polymorphisms (SNPs) in the miRNA seed regions are associated with clinical outcomes in rectal cancer patients receiving chemoradiotherapy. Eighteen SNPs were genotyped in 365 individuals and the associations between genetic variations and acute adverse events were indicated by odds ratios (ORs) and 95% confidence intervals (CIs) by logistic regression model. The associations between genetic variations and survival were computed by the hazard ratios (HRs) and 95% confidence intervals (CIs) by a Cox proportional regression model. We found rs2273626 was significantly associated with decreased risk of grade≥2 leukopenia, with the ORs of 0.48 (95%CI= 0.31-0.74; P = 0.0009). Also, we found rs202195689 was associated with overall survival time and disease-free survival time, with the HR for death being 1.94 (95%CI= 1.19-3.14; P = 0.0074) and 1.83 (95%CI= 1.24-2.72; P= 0.0026).In conclusion, we established a twenty-gene signature for predicting treatment response in local advanced rectal cancer patients based on gene expression profiling and ZNF37A, one of the most significantly different expressed gene, could repress the transcription of TNFRSF6B, then promote cell apoptosis and increase sensitivity to chemoradiotherapy. Association studies of genetic variations and acute adverse events and survival time in patients with locally advanced rectal cancer showed that genetic variations located in miRNA seed regions decreased risk of grade≥2 leukopenia or associated with poor prognosis in rectal cancer patients. Our study may help for understanding the broad variety in clinical outcome of rectal cancer treatment and assist clinicians in making the most appropriate treatment plan for each patient in the future. |
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