Suppression of autophagy enhances preferential toxicity of paclitaxel to folliculin-deficient renal cancer cells

• Published in: Journal of experimental & clinical cancer research Vol. 32; no. 1; p. 99
• Main Authors: Zhang, Qi, Si, Shuhui, Schoen, Sue, Chen, Jindong, Jin, Xun-Bo, Wu, Guan
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 04-12-2013; BioMed Central
• Subjects: Antineoplastic Agents, Phytogenic - pharmacology; Apoptosis; Apoptosis - drug effects; Apoptosis Regulatory Proteins - deficiency; Apoptosis Regulatory Proteins - genetics; Apoptosis Regulatory Proteins - metabolism; Autophagy (Cytology); Autophagy - drug effects; Autophagy - genetics; Beclin-1; Breast cancer; Cancer; Cancer cells; Cell Line, Tumor; Chemotherapy; Colorectal cancer; Degeneration; Dose-Response Relationship, Drug; Estrone - deficiency; Estrone - metabolism; Gene Knockdown Techniques; Health aspects; Humans; Kidney Neoplasms - drug therapy; Kidney Neoplasms - enzymology; Kidney Neoplasms - metabolism; Kidney Neoplasms - pathology; Kinases; MAP Kinase Signaling System - drug effects; Medical research; Membrane Proteins - deficiency; Membrane Proteins - genetics; Membrane Proteins - metabolism; Nervous system; Paclitaxel - pharmacology; Physiological aspects; Prevention; RNA, Small Interfering - genetics; RNA, Small Interfering - metabolism; Studies; Transfection; China
• ISSN: 1756-9966; 0392-9078; 1756-9966
• DOI: 10.1186/1756-9966-32-99

Paclitaxel, a widely used chemotherapeutic drug, can induce apoptosis in variety of cancer cells. A previous study has shown preferential toxicity of paclitaxel to FLCN-deficient kidney cancer cell line, UOK257. In this report, we investigate the cellular and molecular mechanism of paclitaxel-induced autophagy and apoptosis in renal cancer cells with and without FLCN expression.
Two pairs of cell lines were used: FLCN siRNA-silenced ACHN cell line (ACHN-5968) and scrambled ACHN cell line (ACHN-sc); FLCN-null UOK257 cell line and UOK257-2 cell line restored with ectopic expression of FLCN. Autophagy was examined by western blot, GFP-LC3, transmission electron microscopy, and MDC assay. Cell viability and apoptosis were detected using MTT assay, DAPI stain and TUNEL assay. After inhibition of autophagy with 3-Methyladenine (3-MA) or Beclin 1 siRNA, cell viability and apoptosis were measured by MTT assay and TUNEL assay.
After paclitaxel treatment, a dose-dependent decrease in cell viability and increase in apoptosis were observed in FLCN-deficient UOK257 and ACHN-5968 cells compared to their FLCN-expressing counterparts, suggesting that renal cancer cells without FLCN were more sensitive to paclitaxel. Enhanced autophagy was found to be associated with paclitaxel treatment in FLCN-deficient RCC cells. The MAPK pathway was also identified as a key pathway for the activation of autophagy in these kidney cancer cells. Inhibition of phosphorylated ERK with ERK inhibitor U0126 showed a significant decrease in autophagy. Furthermore, after inhibition of autophagy with 3-Methyladenine (3-MA) or Beclin 1 siRNA, apoptosis induced by paclitaxel was significantly increased in FLCN-deficient UOK257 and ACHN-5968 cells.
Preferential toxicity of paclitaxel to FLCN-deficient kidney cancer cells is associated with enhanced autophagy. Suppression of autophagy further enhances paclitaxel-induced apoptosis in FLCN-deficient renal cancer cells. Our results suggest that paclitaxel combined with an autophagy inhibitor might be a potentially more effective chemotherapeutic approach for FLCN-deficient renal cancer.