Inhibition Of Autophagy With MicroRNA-30a And 3-MA Increases The Sensitivity Of Cancer Cells And Tumors To Chemotherapeutic Agents

Cancer is a kind of disease hard to cure, it imperiling the health of human. Using drug to cure cancer is widely adopt and acquired significant therapeutic effects. However, many cancer are insensitive or resistant to drugs, more worse, there are still cancers developed multi-drug resistance, i.e. They can endure many different drugs, which brought about evil consequence to the patients and no way to cure. The patients have to endure the cancer ailment but waiting for the coming of their life end-day.Many courses can bring about drug resistance for cancer. Under drug stress, cells can initiate autophagy as the response. During autophagy phase, the cells block the outside drugs enter in, and digest the autophagosomes seclude damaged organelles or error folded protein and recycle utilize the degraded substances to maintain their basic metabolisms. This incurred the drugs can not kill the cancer cells immediately and conferring cells drugs resistance. Thus, inhibiting the autophagy during chemotherapy is a possible way to remove the drug resistance of cancer cells which can improve the curative effects for anticancer agents.With the idea, we using cis-platinum treated HeLa cells and cis-platinum resistant liver cancer cell strain HepG2and breast cancer cell MCF-7. the result indicate cis-platinum can induce autophagy for these cells, autophagosome reached to45every10cells, and Beclin-1expression enhanced. Whereas, cis-platinum declined the miR-30a level to18%of the control. The reason is that miR-30a transcription was shrunk after cis-platinum aggregated the DNA in cells, with the result removing the restrain on Beclin-1and the Beclin-1expression facilitated the autophagosome formation.Transfect liposome coated miR-30a to the cis-platinum caused miR-30a deficient cells leads to the number of autopgagosome abated to5around, and Beclin-1expression reduced. The autophagy inhibition caused a31%apoptosis for the cells,10%more than the cis-plutinum only treated. We also transfect miR-30a to gastric cancer cell strain SGC-7091which resistant to both taxol and cis-platinum. The result is the same as the previous experiments on HeLa, HepG2and MCF-7. That is, inhibiting the autophagy via forcing the multi-drugs therapy undergoing SGC-7091cell to over-express miR-30a, cell apoptosis will increase, and drug dose was therefore diminished.To verify whether the more obtained apoptosis is brout about by autophagy inhibiting, we used an other autophagy restraining agent3-methyladenine (3-MA), which can block PI3K-Ⅲ binding to Beclin-1and inhibit autophagosome forming, diminished the autophagy of gastric cancer cells SGC-7091and cervical carcinoma HeLa cells under taxol or cis-platinum therapy. No singularity, the used anticancer drugs also made more apoptosis for the autophagy deficient cells.The curative effect measurement in vivo was carried out on tumor bearing mouse. After injected the miR-30a sequence carried lentivirus in cis-platinum treated mouse, the tumors shrunk to4.5mm from6mm, more efficient than that of cis-platinum only administrated samples. Accompanied to the curative effect, transfect of miR-30a during chemotherapy can also save half drugs.Although using synthesized miR-30a or constructing miR-30a containing lentivirus to inhibiting autophagy can improve the curative effects of anti-cancer drugs and solve the drug resistance problem. We must face the reality that the cost of miRNAs synthesis or construction of miRNAs carrier lentivirus is very high, which can not afford by the patients and limited its use. So we move our eyes to the nature to seek costless miR-30a resources. Colostrums is abundant of miR-30a, it contained9times higher miR-30a than that of matured milk, and10times more than all tested cell strains. Besides, an outstanding merit of colostrums is that the miR-30a in it is coated in a kind of vesicle, which facilitated the miR-30a transfect into cells or into tumor tissues. So we extracted the miR-30a from colostrums and used the extracted fragment treated cancer cells and tumor undergoing cis-platinum curing. The results indicate that the colostrums miR-30a can also inhibit the drug induced autophagy, diminished the autophagosome number, declining the level of Beclin-1. Among them, the most important things are it restrained the tumor development and saved drug dose. These results are meaningful for cancer patients:the colostrums miR-30a is not only sensitization the tumor or cancer cells to anticancer drugs and thus brought dose save, but it also impose survival hope to the despair cancer patients.