Rhomboid domain containing 2 (RHBDD2) over-expression is associated to colorectal cancer progression and drug sensitivity to 5-FU treatment.

EZEQUIEL LACUNZA; MARIA V. CROCE; ARIEL ZWENGER; AMADA SEGAL-EIRAS; MARTÏ¿½N C. ABBA

Orlando

Congreso; 102nd Annual Meeting of the American Association for Cancer Research; 2011

Colorectal carcinoma (CRC) is the second leading cause of death among malignancies in the world. Postoperative chemotherapy is widely accepted asthe standard modality for the treatment of this disease; however 50% of patients within an oncology protocol will develop tumor metastaticdissemination. The drug 5-fluorouracil (5-FU) is one of the most commonly used agents for the treatment of CRC at early and advanced tumor stages,but clinical resistance is a major limitation. The identification of novel predictive biomarkers of resistance to 5-FU treatment would allow developingnew therapies and improving the quality of life for CRC patients.The aim of this study was to evaluate the role of RHBDD2 gene expression in human colorectal carcinogenesis and its effect on treatment withchemotherapeutic agent 5-FU. Firstly, we analyzed a dataset of 430 colorectal samples (32 healthy control, 355 primary CRC and 43 metastatic CRC)derived from two independent public available gene expression studies: Bittner et al., 2005 (GEO Acc.#GSE2109), and Sabates-Bellver et al., 2007(GEO Acc.#GSE8671). A statistical significant increase in RHBDD2 expression was detected between normal colorectal samples and CRC specimenswith and without metastasis (p<0.001). In order to validate these data, we performed an immunohistochemical analysis on 140 colorectal tissue samples(5 normal tissues, 20 benign lesions and 115 colorectal carcinomas). We detected high RHBDD2 protein expression in tumor samples compared withnormal and benign lesions (p<0.005). Interestingly, a subset of 33 CRC specimens which were obtained from patients treated with 5-FU prior to surgery,showed a higher intensity of reaction compared with the other CRC samples (p<0.001). To analyze this finding, RHBDD2 5-FU sensitivity wasevaluated by Real Time quantitative RT-PCR in the colon carcinoma cell lines Colo205 and Caco-2. Cells were incubated with 5-FU (50 to 200 μM) for48 and 72Hs. We detected a dramatic up-regulation of RHBDD2 mRNA levels in both cell lines after being exposed to 5-FU (p<0.001). Furthermore,we analyzed the phenotypic effects of silencing RHBDD2 gene expression with and without 5-FU treatment in both cell lines over cell proliferation andapoptosis.In conclusion, our findings suggest that RHBDD2 over-expression might play a role in colorectal neoplastic progression, modulating the response ofcolon cancer cells to 5-FU treatment. Further studies are needed to evaluate the relevance of RHBDD2 gene expression as a predictive biomarker aswell as a therapeutic target to enhance drug efficacy.