Flavopiridol synergizes TRAIL cytotoxicity by downregulation of FLIPL
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Flavopiridol is known to modulate the transcription of genes. We investigated the effect of flavopiridol pretreatment on TRAIL cytotoxicity and on the expression of FLIPL in different TRAIL-resistant cell lines, because FLIP expression is known to confer TRAIL-resistance.
Apoptosis was assessed by PI staining and protein expression by Western blotting. RT-PCR was used for mRNA quantitation. siRNA gene silencing was used to knock down FLIPL.
Flavopiridol pretreatment synergized TRAIL-induced apoptosis in human myeloma and breast cancer cells. Flavopiridol treatment repressed the transcription of FLIPL and downregulated its expression in both myeloma and breast cancer cells. Silencing of FLIPL gene by siRNA sensitized myeloma cells to TRAIL. Flavopiridol treatment downregulated the expression of the proapoptotic members of the Bcl-2 family proteins (Bak, Bax and PUMA-α). The expression of the antiapototic Bcl-2 members (Bcl-2 and Bcl-XL) was not altered by flavopiridol treatment in myeloma cells.
Our data indicate that flavopiridol synergizes TRAIL cytotoxicity by downregulation of FLIPL and this synergistic effect is Bcl-2 family independent.
KeywordsFlavopiridol FLIP TRAIL Bcl-2 family Apoptosis
- 4.Shapiro GI, Supko JG, Patterson A, Lynch C, Lucca J, Zacarola PF, Muzikansky A, Wright JJ, Lynch TJ Jr, Rollins BJ (2001) A phase II trial of the cyclin-dependent kinase inhibitor flavopiridol in patients with previously untreated stage IV non-small cell lung cancer. Clin Cancer Res 7:1590–1599PubMedGoogle Scholar
- 12.Shain KH, Landowski TH, Dalton WS (2002) Adhesion-mediated intracellular redistribution of c-Fas-associated death domain-like IL-1-converting enzyme-like inhibitory protein-long confers resistance to CD95-induced apoptosis in hematopoietic cancer cell lines. J Immunol 168:2544–2553PubMedGoogle Scholar
- 13.Srivastava RK (2001) TRAIL/Apo-2L. Mechanisms and clinical applications in cancer. Neoplasia 3:535–546Google Scholar
- 14.Zhang X, Jin TG, Yang H, DeWolf WC, Khosravi-Far R, Olumi AF (2004) Persistent c-FLIP(L) expression is necessary and sufficient to maintain resistance to tumor necrosis factor-related apoptosis-inducing ligand-mediated apoptosis in prostate cancer. Cancer Res 64:7086–7091PubMedCrossRefGoogle Scholar
- 27.Byrd JC, Shinn C, Waselenko JK, Fuchs EJ, Lehman TA, Nguyen PL, Flinn IW, Diehl LF, Sausville E, Grever MR (1998) Flavopiridol induces apoptosis in chronic lymphocytic leukemia cells via activation of caspase-3 without evidence of bcl-2 modulation or dependence on functional p53. Blood 92:3804–3816PubMedGoogle Scholar