Research on the Synergistic Effect of A Novel Apoptosis Inducer Combined with AKT and HSP90 Selective Inhibitors on Hormone-Sensitive and Hormone-Resistant Breast Cancer Cell Lines.

One of the frequent malignant tumors affecting women is breast cancer. This tumor develops and occurs due to several internal and external factors. Resistance remains a key challenge in modern breast cancer therapy. Novel 1-substituted isatin-5-sulfonamides with antiproliferative effects based on isatin-core-containing antitumor compounds were synthesized in three stages via alkylation using benzyl chlorides. The study focuses on the synergistic effect of the obtained 1-substituted isatin-5-sulfonamides, exhibiting pro-apoptotic activity and is combined with heat shock protein 90 (HSP90) and protein kinase B (AKT) selective inhibitors in breast cancer cell lines, which are sensitive and resistant to antiestrogens.To create resistance, 4-hydroxytamoxifen (HT) was applied to create a resistant cell subline (MCF7/HT), achieving a resistance index of 2. MCF7/p53-LUC cell subline was obtained through transfection using the p53-responsive luciferase reporter plasmid. The lead compound <i>LCTA-3344</i>, exhibited the most significant antiproliferative effect, with a lower half-maximal inhibitory concentration (<i>IC₅₀</i> ) in MCF7/HT (1.4±0.1 μМ) compared to MCF7 (2.6±0.3 μМ). Synergistic effects were observed when Combining the apoptosis inducer <i>LCTA-3344</i> and AKT Inhibitor IV in both MCF7 and MCF7/HT, demonstrating the combination index (CI) values of 0.8 and 0.4, respectively (indicating higher activity). Apoptosis inducer <i>LCTA-3344</i> combined with AKT Inhibitor X and HSP90 inhibitor did not show such significant activity with a minimal CI value of 0.9. Notably,Compound <i>LCTA-3344</i> did not enhance luciferase activity in the MCF7/p53-LUC cell subline, while chemotherapeutic agent doxorubicin has been determined to be its potent inducer. In conclusion, apoptosis inducer <i>LCTA-3344</i> was 1.9-fold more active toward MCF7/HT in comparison to the parental cell line. Compound <i>LCTA-3344</i> together with AKT Inhibitor IV was the most active drug combination on the MCF7/HT subline, with a CI of 0.4. Compound <i>LCTA-3344</i> induced apoptosis through a p53-independent mechanism, which holds promise as a novel therapy for hormone-resistant breast cancers. AKT Inhibitor IV caused apoptosis of MCF7 cells to a greater extent than compound <i>LCTA-3344</i>, and their combination resulted in a synergistic effect.