Involvement of Bcl-2, Src, and ERα in gossypol-mediated growth inhibition and apoptosis in human uterine leiomyoma and myometrial cells

Aim: To investigate the effect of gossypol on the growth of cultured human uterine leiomyoma and myometrial cells, the level of Bcl-2 and the activity of Src and estrogen receptor (ERα). Methods: Human uterine leiomyoma and adjacent normal myometrial cells were cultured in vitro . Both cell types were treated with a graded concentration of gossypol. Cell viability was assayed using CCK-8. Morphological change was observed with optical and electronic microscopy. Apoptosis was evaluated using TUNEL assay. Levels of Bcl-2, ERα and Src were analyzed using Western blotting. Results: Gossypol significantly inhibited growth and promoted apoptosis in cultured human uterine leiomyoma cells with the IC 50 value and its corresponding 95% confidence intervals (CI) of 6.5 (4.0–10.5), 9.0 (4.9–16.5), and 7.5 (4.0–14.1) μmol/L at 20, 40, and 60 h, respectively. Gossypol exerted inhibitory effects on the myometrial cells with the IC 50 value and its 95% CI of 49.1 (28.3–85.0), 14.5 (7.7–27.4), and 2.6 (1.2–5.6) μmol/L at 20, 40, and 60 h, respectively. Compared with control, gossypol 0.1-3.0 μmol/L markedly decreased the protein expression of Bcl-2 ( P <0.05) in both leiomyoma and myometrial cells in a concentration-dependent manner, and significantly suppressed the level of phospho-Tyr416Src ( P <0.05) in both cell types at 3.0 μmol/L without obvious alteration of c-Src and phospho-Tyr527Src levels ( P >0.05). In addition, gossypol markedly reduced both the expression of ERα ( P <0.05) at the low concentration of 0.1 μmol/L in the myometrial cells and the level of phospho-ser167ERα ( P <0.05) at the high concentration of 3.0 μmol/L in the leiomyoma cells. Conclusion: Gossypol inhibits proliferation and induces apoptosis in human uterine leiomyoma and myometrial cells. It is likely that the mechanisms of action involve reducing the protein level of Bcl-2 and the activity of Src and ERα.