Expression and localization of apolipoprotein M in human colorectal tissues

Abstract

BackgroundIt has been well documented that apolipoprotein M (apoM) is principally expressed in the liver and kidney. However we found that there was weak apoM expression in other tissues or organs too, which could not be ignored. In the present study, we therefore examined apoM expression in human colorectal tissues including cancer tissues, cancer adjacent normal tissues, polyp tissues and normal mucosa as well as inflammatory mucosa.MethodsTissue samples were collected from patients who underwent surgical resection or endoscopic examination. ApoM mRNA levels were determined by the real-time RT-PCR and apoM protein mass were examined by the immunohistochemistry.ResultsApoM protein can be detected in all colorectal tissues. However, apoM protein mass were significantly lower in the cancer tissues than its matched adjacent normal tissues, polyp tissues, normal mucosa and inflammatory mucosa. In parallel, apoM mRNA levels in the colorectal cancer tissues (0.0536 ± 0.0131) were also significantly lower than those in their adjacent normal tissues (0.1907 ± 0.0563) (P = 0.033). Interestingly, apoM mRNA levels in colorectal cancer tissues were statistic significant higher in the patients with lymph node metastasis than the patients without lymph node metastasis (P = 0.008). Patients under Dukes' C and D stages had much higher apoM mRNA levels than patients under Dukes' A and B stages (P = 0.034).ConclusionIt is concluded that apoM could also be expressed in human colorectal tissues besides liver and kidney. ApoM mRNA levels in the colorectal cancer tissues were significantly increased in the patients with lymph node metastasis. Whether increased apoM expression in the patients with lymph node metastasis being related to patients' prognosis and the physiopathological importance of apoM expression in colorectal tissues need further investigation.

Apolipoproteins and cancer

“…Overexpression of APOM inhibited the proliferation, migration, and invasion of hepatoma cells and the development of xenograft tumors in nude mice, and promoted apoptosis . APOM mRNA and protein levels were notably reduced in colorectal cancer tissues, compared to adjacent healthy tissues, normal mucosa, polyps, and inflammatory mucosa …”

ABCA1 upregulating apolipoproein M expression mediates via the RXR/LXR pathway in HepG2 cells

“…Human apoM is exclusively expressed in the hepatocytes in liver and tubular epithelial cell in kidney, and small amounts were also found in fetal liver and fetal kidney [2]. Luo, et al,[3] demonstrated that apoM could also be abundantly expressed in human colorectal tissues, although the pathophysiological importance of this expression and if it could influence plasma apoM pool are unknown. Wolfrum, et al, [4] demonstrated that apoM, by influencing preβ-HDL formation, being an important regulator of HDL metabolism in vivo, which could influence cholesterol efflux and the susceptibility of atherosclerosis.…”

Palmitic acid suppresses apolipoprotein M gene expression via the pathway of PPARβ/δ in HepG2 cells

“…Human APOM is mainly found in hepatocytes of the liver and tubular epithelial cells in kidney [1], and it's also expressed weakly in the colorectal tissues [2]. It has been demonstrated that APOM is important for the formation of preβ-HDL and cholesterol efflux to HDL, which could attenuate atherosclerotic process [3].…”