大肠癌microRNA与DNA甲基化修饰相互调控的研究进展

The role of microRNAs in colorectal cancer

Colorectal cancer (CRC) is still the third most common cancer in the world. Mechanism of CRC tumorigenesis has been widely studied at the molecular levels, and has been recently entered the area of microRNAs. MicroRNAs are small 19 to 22 nucleotides of RNA that engage in the regulation of cell differentiation, apoptosis, and cell cycle progression. MicroRNAs are similar to small interfering RNA (siRNA), that post-transcriptionally regulate gene expression and control various cellular mechanisms. They are important factors in the carcinogenesis of CRC, one of the most important factors includes microRNA. MicroRNAs have been linked to CRC development, and these molecules have been recently studied as new potential biomarkers in diagnosis and treatment of CRC. Specific microRNA expression patterns help distinguish CRC from other colon related disease, and may be used as a prognostication factor in patients after treatment with different chemotherapy drugs. More over the newest molecular therapy via tumor suppressor micro RNA replacement can be new insight in molecular therapy of CRC. This review summarizes the potential roles of microRNAs as potential biomarkers for CRC diagnosis, and treatment.

Overexpression of miR-486-5p suppresses tumor lymphangiogenesis in colorectal carcinoma by targeting neuropilin-2

AIM: To investigate the effect of microRNA-486-5p (miRNA-486-5p) overexpression on tumor lymphangiogenesis in colorectal carcinoma cells and to explore the underlying mechanism.

METHODS: A eukaryotic expression vector of miRNA-486-5p was transiently transfected into human colorectal carcinoma SW620 cells to induce miRNA-486-5p overexpression. A human colorectal carcinoma model in nude mice was then established, and the miRNA-486-5p vector was directly injected into local tumor tissue. Then, tumor size was measured every three days. The expression level of miRNA-486-5p in tumor tissue was determined by real-time PCR (RT-PCR). Meanwhile, the expression level of Neuropilin-2 (NRP2) and the number of lymphatic microvessels were detected by immunohistochemistry. The expression of NRP2 was measured by Western blot.

RESULTS: The expression of miRNA-486-5p increased significantly in the miRNA-486-5 transfected SW620 cells, and the mean expression level of miRNA-486-5p increased by 12.57 times ± 2.31 times after transfection. The growth speed of tumor in the miRNA-486-5p vector injected group was significantly slower than that in the control group (P < 0.05). The mass of tumor in the miRNA-486-5p vector injected group was significantly lower than that in the control group (P < 0.05). The expression of NRP2 and the number of lymphatic microvessels in the tumor tissue were also remarkably decreased in the miRNA-486-5p vector injected group (P < 0.05).

CONCLUSION: Overexpression of miRNA-486-5p could significantly inhibit the growth and lymphangiogenesis in colorectal carcinoma cells in vivo, and this might be related to the down-regulated expression of NRP2.

Qxaliplatin plus fluorouracil and calcium folinate for metastatic colorectal cancer

AIM: To explore the effects of oxaliplatin plus fluorouracil and calcium folinate in the treatment of metastatic colorectal cancer.

METHODS: Ninety-six patients with metastatic colorectal cancer were randomly divided into two groups. All patients were treated by oxaliplatin plus fluorouracil. On the basis of this treatment, the experiment group was treated with calcium levofolinate, and the control group was treated with calcium folinate. The clinical effects and adverse reactions were compared, and the influencing factors were analyzed.

RESULTS: The effective rate in the treatment group was higher than that in the control group, but the difference was not statistically significant (29.17% vs 20.83%, P > 0.05). The incidence of adverse reactions in the two groups also had no significant difference (P > 0.05). Although the total effective rate did not differ significantly between the rectal cancer group and the colonic cancer group (31.11% vs 19.61%, P > 0.05) and between the liver, lung and other groups (P > 0.05), a significant difference was noted between the initial treatment group and retreatment group (43.59% vs 12.28%, P < 0.05).

CONCLUSION: The efficacy of oxaliplatin plus fluorouracil and calcium folinate in metastatic colorectal cancer was similar to that of oxaliplatin plus fluorouracil and calcium levofolinate. The efficacy was more significant in patients without previous chemotherapy.

Down-regulation of microRNA-433 expression in gastric cancer: Possible mechanisms involved

AIM: To investigate the expression of microRNA-433 in gastric cancer and to explore the possible mechanisms involved.

METHODS: The expression level of microRNA-433 in 43 cases of gastric cancer and matched adjacent normal tissue samples was examined by qRT-PCR. The relationship between microRNA-433 expression and clinical features of gastric cancer was analyzed. Human gastric cancer SGC-7901 cells were treated with 1, 5, or 10 μmol/L of 5-Aza-CdR for five days, and the expression level of microRNA-433 in treated cells was determined. SGC-7901 cells were then transfected with a microRNA-433 mimic, and the proliferation and apoptosis of the transfected cells were examined by FCM.

RESULTS: The expression level of microRNA-433 was lower in gastric cancer than in normal gastric tissue (P < 0.05). MicroRNA-433 expression was associated with tumor stage (P < 0.05), but not with sex, age or tumor differentiation. The expression level of microRNA-433 in SGC-7901 cells was significantly lower than that in gastric mucosal cell line GES-1. Treatment of SGC-7901 cells with 5-Aza-CdR up-regulated microRNA-433 expression in a dose-dependent manner. Transfection of SGC-7901 cells with a microRNA-433 mimic up-regulated the expression of microRNA-433 and increased cell apoptosis.

CONCLUSION: The expression level of microRNA-433 is lower in gastric cancer than in normal gastric tissue. MicroRNA-433 expression correlates with tumor stage. Treatment of SGC-7901 cells with 5-Aza-CdR up-regulates microRNA-433 expression possibly by regulating promoter methylation. Transfection of SGC-7901 cells with a microRNA-433 mimic accelerates apoptosis of tumor cells, suggesting that microRNA-433 is a potent tumor suppressor.