Telomerase as a Possible Candidate Targeting Therapy in Different Breast Cancer Cell Lines

BACKGROUND: Telomerase activity is up regulated in most breast cancer subtypes but not in the adjacent normal tissues. Thus, it is a promising target for anticancer therapy. The present work investigated the effects of telomerase inhibition by siRNA on breast cancer cell lines and studied the feasibility of whether the combined effect of doxorubicin with siRNA treatment on breast cancer cells potentiates a rapid cellular response to the cytotoxic effect of chemotherapy. METHODS: This study was performed on Luminal A (MCF-7), triple negative (MDA-MB-468), and HER-2/neu (SKBR-3) human breast cancer cell lines, wherein telomerase activity inhibition by hTERT siRNA and doxorubicin was detected by measuring telomerase activity using Telomeric Repeat Amplification Protocol (TRAP assay), assessing cell viability through MTT assay, and evaluating apoptosis through scanning electron microscopy (SEM) and through estimating caspase-3 and -8 activities using enzyme-linked immunosorbent assay (ELISA). RESULTS: In the present study, hTERT siRNA effectively reduced telomerase activity and cell viability to more than 90% and 60%, respectively, in most breast cancer cell lines within 72 hours after transfection. The combination of hTERT siRNA and doxorubicin showed a cumulative effect compared with either treatment alone (P < 0.05). Meanwhile, SEM demonstrated apoptotic morphologic cell changes. CONCLUSION: Telomerase inhibition is a promising strategy for the effective treatment of breast cancer. When used in combination with doxorubicin, it could potentiate the cytotoxic effect of the drug on breast cancer cells.