Adjuvant therapy with stattic enriches the anti-proliferative effect of doxorubicin in human ZR-75-1 breast cancer cells via arresting cell cycle and inducing apoptosis.

Adjuvant therapy with novel and effective component has been presented as a contrivance in breast cancer treatment versus the conventional methods. The current research was done to evaluate the implement of stattic, specific STAT3 inhibitor on the anti-proliferative and apoptotic behavior of doxorubicin on ZR-75-1 breast cancer cells. Cell viability was investigated by MTT assay, the percentage of apoptosis by DAPI staining, and Annexin V. Real Time-PCR was applied to find out the correlation between mechanistic roles of the STAT3 pathway and apoptotic signal in the modulation of Bcl-2 and Bax gene expressions axis. The IC50 values for doxorubicin and stattic were 2.5 ± 0.18 μM and 3.5 ± 0.28 μM, respectively. Combination index (CI) value for ZR-75-1 breast cancer was 0.72, which indicated a strong synergistic effect. Incubation of the cells with a combination of stattic and doxorubicin revealed a significant increase in growth inhibitory effect of doxorubicin with more than 50% decrease in proliferation rate and a two-fold increase in the percentage of apoptotic cells. Assessment of gene expression levels demonstrated a visible decrease in antiapoptotic Bcl-2 and Bcl-xl accompanied by an increase in pro-apoptotic Bax mRNA levels (p < 0.05). Taken together, our results show that combination of a STAT3 inhibitor and doxorubicin can be figured out as a promising approach for dealing of patients with breast cancers.