Aberrant SERCA3 expression during the colorectal adenoma-adenocarcinoma sequence

Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) 3 is involved in calcium mobilization from the endoplasmic reticulum into the cytosol and is closely linked to metabolism, neuronal plasticity, gene transcription, cell growth, differentiation, apoptosis, protein folding and carcinogenesis. In order to elucidate the role of SERCA3 in colorectal carcinogenesis and subsequent progression, its expression was examined using immunohistochemistry and in situ hybridization (ISH) on tissue microarrays containing colorectal carcinomas, adjacent non-neoplastic mucosa (NNM) and adenoma, and metastatic carcinoma in lymph node and liver. Colorectal carcinoma tissue and cell lines were assessed for SERCA3 expression by western blotting or RT-PCR, respectively. SERCA3 was distinctively expressed in Colo201, Colo205, DLD-1, HCT-15, HCT-116, HT-29, KM-12, SW480, SW620 and WiDr cells at both the mRNA and protein levels. SERCA3 mRNA expression was low in carcinoma when compared to that in matched NNM by quantitative PCR (P<0.05), while the converse was true by ISH. Lower expression of SERCA3 was immunohistochemically observed in colorectal carcinoma when compared to that in NNM and adenoma (P<0.05). In contrast, primary carcinoma showed high SERCA3 expression when compared to that in metastatic carcinoma in lymph node or liver by IHC (P<0.05). Immunohistochemically, SERCA3 expression was negatively related to lymphatic invasion, but not with age, gender, depth of invasion, venous invasion, lymph node metastasis, distant metastasis, TNM stage, degree of differentiation or survival rate (P>0.05). There was a positive relationship between SERCA3 expression and serum CEA levels in the carcinoma patients (P<0.05). Cox's proportional hazards model indicated that depth of invasion and distant metastasis are independent prognostic factors for overall colorectal carcinomas (P<0.05). These findings suggest that aberrant SERCA3 expression is closely linked to the adenoma-adenocarcinoma sequence and progression of colorectal carcinomas.