There are several DNA repair pathways that protect cellular DNA from injury, such as nucleotide excision repair (NER) and mismatch repair (MMR). The protein product of the excision repair cross-complementation group 1 (ERCC1) gene plays a pivotal role in NER. The exact relationship between MMR proteins and ERCC1 is not well known in colorectal carcinoma (CRC). Aim of the Study: To investigate expression of ERCC1 and MMR proteins in colorectal mucinous carcinoma (MA) and non-mucinous carcinoma (NMA) using tissue microarray technique. Material and Methods: We studied tumor tissue specimens from 150 patients with colorectal mucinous (MA) and non-mucinous adenocarcinoma (NMA). Tissue microarrays were constructed using modified mechanical pencil tips technique and immunohistochemistry for ERCC1, MLH1, MSH2, MSH6, and PMS2. Results: NMA showed a significantly more frequent aberrant cytoplasmic expression than MA while MA showed a more frequent intact nuclear expression than NMA. There were no significant differences between the NMA and MA groups in the expression of MMR proteins. In NMA cases, ERCC1 expression was significantly related to MMR status while was not significantly related in MA cases. ERCC1 expression was not significantly related to overall and disease-free survival in both NMA and MA groups. Conclusion: this study is the first to investigate the relation between MMR status and ERCC1 expression in colorectal MA and NMA. ERCC1 expression was significantly related to MMR status only in NMA cases. Hence, the current study emphasizes that further research about the relation between various DNA repair pathways is needed.
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