Curcumin significantly enhances dual PI3K/Akt and mTOR inhibitor NVP-BEZ235-induced apoptosis in human renal carcinoma Caki cells through down-regulation of p53-dependent Bcl-2 expression and inhibition of Mcl-1 protein stability

• Published in: PloS one 2014-04, Vol.9 (4), p.e95588
• Main Authors: Seo, Bo Ram, Min, Kyoung-Jin, Cho, Il Je, Kim, Sang Chan, Kwon, Taeg Kyu
• Format: Article
• Language: English
• Subjects: 1-Phosphatidylinositol 3-kinase; AKT protein; Apoptosis; Apoptosis - drug effects; Bcl-2 protein; Bioactive compounds; Biological activity; Biology and life sciences; Blotting, Western; Cancer; Cancer therapies; Carcinoma, Renal Cell - metabolism; Cell death; Cell Line, Tumor; Cell Proliferation - drug effects; Cell survival; Cell Survival - drug effects; Cell Survival - genetics; Chemopreventive agents; Colon; Combined treatment; Curcumin; Curcumin - pharmacology; DNA Fragmentation - drug effects; Ectopic expression; Fibroblasts; Flow Cytometry; Gene expression; Gene regulation; Humans; Imidazoles - pharmacology; Inhibitors; Kidney cancer; Kinases; Mcl-1 protein; Medical research; Medicine and Health Sciences; Mesangial cells; Mortality; p53 Protein; Phosphatidylinositol 3-Kinases - antagonists & inhibitors; Post-transcription; Proto-Oncogene Proteins c-akt - antagonists & inhibitors; Quinolines - pharmacology; Renal cell carcinoma; Reverse Transcriptase Polymerase Chain Reaction; Rhizomes; RNA, Small Interfering; Signal transduction; Signal Transduction - drug effects; Signaling; Skin; Synergistic effect; TOR protein; TOR Serine-Threonine Kinases - antagonists & inhibitors
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0095588

The PI3K/Akt and mTOR signaling pathways are important for cell survival and growth, and they are highly activated in cancer cells compared with normal cells. Therefore, these signaling pathways are targets for inducing cancer cell death. The dual PI3K/Akt and mTOR inhibitor NVP-BEZ235 completely inhibited both signaling pathways. However, NVP-BEZ235 had no effect on cell death in human renal carcinoma Caki cells. We tested whether combined treatment with natural compounds and NVP-BEZ235 could induce cell death. Among several chemopreventive agents, curcumin, a natural biologically active compound that is extracted from the rhizomes of Curcuma species, markedly induced apoptosis in NVP-BEZ235-treated cells. Co-treatment with curcumin and NVP-BEZ235 led to the down-regulation of Mcl-1 protein expression but not mRNA expression. Ectopic expression of Mcl-1 completely inhibited curcumin plus NVP-NEZ235-induced apoptosis. Furthermore, the down-regulation of Bcl-2 was involved in curcumin plus NVP-BEZ235-induced apoptosis. Curcumin or NVP-BEZ235 alone did not change Bcl-2 mRNA or protein expression, but co-treatment reduced Bcl-2 mRNA and protein expression. Combined treatment with NVP-BEZ235 and curcumin reduced Bcl-2 expression in wild-type p53 HCT116 human colon carcinoma cells but not p53-null HCT116 cells. Moreover, Bcl-2 expression was completely reversed by treatment with pifithrin-α, a p53-specific inhibitor. Ectopic expression of Bcl-2 also inhibited apoptosis in NVP-BE235 plus curcumin-treated cells. In contrast, NVP-BEZ235 combined with curcumin did not have a synergistic effect on normal human skin fibroblasts and normal human mesangial cells. Taken together, combined treatment with NVP-BEZ235 and curcumin induces apoptosis through p53-dependent Bcl-2 mRNA down-regulation at the transcriptional level and Mcl-1 protein down-regulation at the post-transcriptional level.