Breast cancer has become the prevailing cause of death, so the research for their treatment has become advanced day by day. Breast cancer behaves differently in normoxic and hypoxic condition so does the anticancer drugs in both the condition in order to treat them. These drugs might have different effect on the expression of miRNAs in both normoxic and hypoxic conditions. In the present study, we evaluated the IC50 of three anticancer drugs-doxorubicin, ?-Amanitin, DCA on MDA-MB-231 and after treatment with these drugs, have checked the expression of miRNAs- let-7b and miR1275 in both hypoxic and normoxic condition by RT-PCR and results were analyzed by native PAGE