OBJECTIVETo investigate the mRNA and protein expression levels of apolipoprotein M (apoM) in the human colorectal cancer tissues, and to explore its clinical relevance.

METHODSReal-time PCR was carried out to determine the mRNA expression levels both in cancer tissue and its adjacent normal tissue from 20 patients with colorectal cancer. Immunohistochemistry was also carried out to determine the protein levels in 23 colorectal biopsy samples (7 normal mucosa, 6 inflammatory mucosa and 10 polyp tissues) and 20 cases of colorectal cancer tissues as well as the adjacent normal tissues.

RESULTSReal-time PCR result showed that apoM mRNA level in the colorectal cancer tissues was significantly lower than that in their adjacent normal tissues (0.05±0.01 vs. 0.19±0.05, P<0.05). ApoM mRNA level in colorectal cancer tissues was statistically significant higher in the patients with lymph node metastasis as compared to the patients without lymph node metastasis (P<0.01). The median value of apoM protein in cancer tissues was 5.50, which was significantly lower than that in the adjacent normal tissues (10.5, P<0.05), inflammatory mucosa tissues (9.75, P<0.05), polyp tissues (11.0, P<0.01) and normal mucosa (10.5, P<0.05). No significant association was observed between the apoM protein level and the clinicopathological parameters of patients.

CONCLUSIONSBoth apoM mRNA and protein expression levels in colorectal cancer tissues are significantly decreased in contrast to normal and benign colorectal tissues. The apoM mRNA expression in colorectal cancer tissues is closely associated with nodal metastasis.