Experimental Study On The Chemotherapy Sensitivity Of Colon Cancer Regulated By Lin28b-let-7Axis

Background: Colon cancer is one of the most common clinical malignant tumors.The incidence of colon cancer showed upward trend according to statisticalanalysis of that in China recently. There are many reasons leading to tumorrecurrence or metastasis, one of the most important is that tumor cells produceddrug-resistance to chemotherapeutic drugs. There are lots of studies indicating thatthe expression of Lin28B, one of Lin28iso-forms in colon cancer tissues, wassignificantly increased. Small molecule RNA (microRNA) let-7,a tumorsuppressor gene, can regulate cell terminal differentiation and apoptosis. Researchfound that Lin28can inhibit Let-7maturation and the mechanism was implicatedthat Lin28B can bind different stages of Let-7products, which was demonstratedby the high levels of expression of Lin28and corresponding decline of Let-7intumor tissues. Previous studies found that due to the reciprocal negative regulationof Lin28B and Let-7, Lin28B expression in colon cancer cells and tissues inducedtumor drug resistance, thus restoring expression of Let-7family may haveextraordinary significance in the treatment of colon cancer. So there is reason tobelieve that the supplementary/increased expression of Let-7in colon cancer cellsmay increase the sensitivity to chemotherapy drugs.Objectives:1, To detect the expression of Lin28B in8kinds of human coloncancer cell lines and human colon cancer tissues;2, To confirm the existence ofLin28B-Let-7regulation axis in the colon cancer cells;3, To observe the effect ofoverexpression of Lin28B/Let-7on sensitivity to chemotherapeutic drugs5-FU inhuman colon cancer cells.Materials and methods:1, PCR was used to detected the expression of Lin28B protein in8kinds of human colon cancer cell lines; Real-time PCR, Western Blotand immunohistochemistry were used to detect the21cases of colon cancertissues and19cases of normal colon tissues that came from PLA General HospitalHainan Branch, and to observe the expression and localization of Lin28B;2,Immunofluorescence, western blot after nucleoplasmic protein separation andtransfection of GFP lentiviral vector were maintained to test the location ofLin28B, then immunohistochemistry was used to determine the location in humancolon cancer cell lines.3, In the human colon cancer cell lines, we detected theeffect of overexpression of Let-7or Lin28B on the chemotherapy sensitivity of5-FU.Results: We found the Lin28B expression in8kinds of colon cancer cell lines andcolon cancer tissues, meanwhile, we also found that expression of Lin28B wassignificantly higher than that of normal colonic tissues. The location experimentshowed that Lin28B expressed in the nucleus and cytoplasm, especially highly inthe cytoplasm. Real-time PCR and Western Blot indicated that theLin28B-Let-7control axis existed. Finally, results of drug sensitivity test showedthat overexpression of Let-7increased the sensitivity of colon cancer cellsto chemotherapeutic drugs of5-FU, whereas overexpression of Lin28B reducedthe sensitivity.Conclusions:1, It was found that Lin28B was expressed in human coloncancer cell lines and colon cancer tissues, and the expression in tumor tissues wassignificantly higher than that in normal colonic tissue;2, Lin28B was expressedin colon cancer cell cytoplasm and nucleus, but the expression in cytoplasm ismuch higher than that in the nucleus;3, We confirmed the existence of Lin28Band Let-7control axis;4, Increasing the expression of Let-7in colon cancercells can improve sensitivity to chemotherapeutic drugs; on thecontrary, increasing expression of Lin28B in colon cancercells can reduce sensitivity to chemotherapeutic drugs in colon cancer cells.