Treatment of muscle invasive urinary bladders tumors: A potential role of the mTOR inhibitors

Gemcitabine and cisplatin regimen is an approach currently used in urinary bladder cancer treatment. However, side effects’ arising from its administration is a hard concern. In this study, we evaluated different schedules of gemcitabine and cisplatin to determine the efficacy of this combination together with two mammalian targets of rapamycin (mTOR) inhibitors: temsirolimus and everolimus. The 5637, HT1376 and T24 urinary bladder cancer cell lines were exposed to gemcitabine (72 hours), cisplatin (48 hours), temsirolimus (72 hours) and everolimus (72 hours), in isolation, or in combined schedules (gemcitabine, cisplatin and temsirolimus, or gemcitabine, cisplatin and everolimus). The levels of phosphorylated p70S6 K and 4E-BP1 after treatment with temsirolimus and everolimus were investigated by immunoblotting. The antiproliferative activity, cell cycle distribution, autophagy and apoptosis were analyzed by the MTT assay and immunocytochemistry, flow cytometry, acridine orange staining and M₃₀ CytoDEATH antibody. No significant differences in the expression of P-4E-BP1 and P-p70S6 K after temsirolimus and everolimus exposure were found in the HT1376 and T24 cell line. A statistically significant decrease of phosphorylated 4E-BP1 form was detected in the 5637 cell line (P < 0.05) after everolimus exposure. Temsirolimus and everolimus conjugated with gemcitabine and cisplatin decreased the cell proliferation in all three cell lines. This pattern of response was similar to the other parameters analyzed (reduced Ki-67 expression, increased autophagy and apoptosis). Also, in the combined regimen, an enhanced cell cycle arrest in the G₀/G₁ phase in the 5637 cell line and in the early S-phase in the HT1376 and T24 cell lines were observed. The muscle invasive HT1376 and T24 cell lines were the most sensitive to both combinations. The combination of gemcitabine, cisplatin and temsirolimus or everolimus yields an enhanced cytotoxicity efficacy, namely in the muscle invasive urinary bladder cancer cell lines. Although further studies are necessary to complement this data, the present results opening new perspectives in muscle invasive urinary bladder cancer treatment.