<i>hSRBC</i> promoter CpG island hypermethylation as resistant predictive biomarker of oxaliplatin based chemotherapy in metastasic colorectal cancer patients.

e14609 Background: Resistance acquisition to chemotherapeutic agents is one of the main problems that come up during cancer treatment. hSRBC is a tumor suppressor gene whose inactivation has been associated with malignant tumor progression. In a previous work, we investigated the influence of hSRBC promoter methylation alterations in oxaliplatin (OXA) resistance acquisition by using a CRC “in vitro” model, detecting an hSRBC promoter hypermethylation in OXA–resistant derived cells when compared with the sensitive counterpart. These results were validated by functional analyses in the same model. Taking this into account, our aim in the present work is to determine the role of hSRBC methylation status as a potential biomarker of OXA resistance, in metastatic CRC patients, treated at first line with fluouropirimidines plus OXA based chemotherapy. Methods: hSRBC promoter hypermethylation was analyzed in DNA extracted from paraffin embebbed tissue of 111 metastatic CRC tumors by using Methylation Specific PCR. Methylation data was correlated to overall response (OR) and progression free survival (PFS) by using F-Fisher test and Kaplan-Meyer Survival curves respectively. A multivariate analysis was carried out by Cox regression. p-values under 0.05 were considered statistic significant. Results: Two independent cohorts of stage IV CRC tumors were included. Twenty-two out of 111 patients received radical surgery for metastasis, that became to be a positive prognostic factor (p-value = 0.04). Gene hypermethylation was detected in a 33% of cases. Although OR was not associated with hSRBC methylation, we observed a significant correlation between hypermethylation of gene and a worse PFS in patients without metastasis surgery (Log Rank; p-value = 0.04). Conclusions: Remarkably, hSRBC promoter hypermethylation is associated with worse PFS in metastatic CRC patients. We suggest hSRBC methylation status as a predictive biomarker of OXA-based treatment outcome in metastatic CRC patients. However, further studies are warranted in order to elucidate the clinical application of these findings.