[Anticancer effects of tea polyphenols on colorectal cancer with microsatellite instability in nude mice].

Objective: To study the anticancer effects of tea polyphenols on colorectal cancer with microsatellite instability (MSI) in nude mice and to explore its mechanism.

Methods: A colostomy was performed on the caecum of nude mice. Tumor fragments collected from the subcutaneous tumor of hMSH2-absence colon carcinoma Lovo cell line were surgically implanted onto the submucosa of the caecum during colostomy to establish the model. Then, the nude mice were divided into untreated group and 50, 75 and 100 mg/kg tea polyphenols groups. The mice in tea polyphenols-treated groups were given intra-abdominal injection of 50, 75 and 100 mg/kg tea polyphenols respectively. The inhibition rates of tumors were calculated, and microsatellite instability (MSI) and the alteration of transforming growth factor-beta1 (TGF-beta1), TGF-beta2 and insulin-like growth factor (IGF) were detected by Genescan method at different times after the injection.

Results: The tumor volumes of the three groups began to decrease at the 1st week and decreased most greatly from 2 to 3 weeks after treatment, and then the tumors tended to increase. The study found that tea polyphenols could inhibit the tumor growth. The tumor inhibition rates in the three treated groups were significantly higher than those in untreated group 1, 2, 3 and 4 weeks after treatment (P<0.01). Detection of MSI showed that the colorectal tumor in the untreated group presented with four MSI signs, including BAT-25, D2S123, D5S346 and D17S250, and TGF-beta1, TGF-beta2, IGF expressions. After using the tea polyphenols, the microsatellite tended to become stable.

Conclusion: Tea polyphenols can inhibit the mismatch-repair-gene deficient colorectal cancer in nude mice by down-regulating the microsatellite instability.