Flavopiridol disrupts STAT3/DNA interactions, attenuates STAT3-directed transcription, and combines with the Jak kinase inhibitor AG490 to achieve cytotoxic synergy

• Published in: Molecular cancer therapeutics Vol. 5; no. 1; pp. 138 - 148
• Main Authors: Lee, Yean Kit, Isham, Crescent R, Kaufman, Scott H, Bible, Keith C
• Format: Journal Article
• Language: English
• Published: United States American Association for Cancer Research 01.01.2006
• Subjects: Antineoplastic Combined Chemotherapy Protocols; Carcinoma, Non-Small-Cell Lung - drug therapy; Carcinoma, Non-Small-Cell Lung - pathology; CDKs and CDK inhibitors; DNA - metabolism; Down-Regulation; Drug Screening Assays, Antitumor; Enzyme Inhibitors - pharmacology; Flavonoids - administration & dosage; Flavonoids - pharmacology; Humans; Janus Kinase 1; Lung Neoplasms - drug therapy; Lung Neoplasms - pathology; Mechanisms of drug action; Myeloid Cell Leukemia Sequence 1 Protein; Neoplasm Proteins - drug effects; Neoplasm Proteins - genetics; Phosphoproteins - drug effects; Phosphoproteins - metabolism; Piperidines - administration & dosage; Piperidines - pharmacology; Protein-Tyrosine Kinases - antagonists & inhibitors; Proto-Oncogene Proteins c-bcl-2 - drug effects; Proto-Oncogene Proteins c-bcl-2 - genetics; RNA Polymerase II - drug effects; RNA Polymerase II - metabolism; STAT3 Transcription Factor - drug effects; STAT3 Transcription Factor - genetics; STAT3 Transcription Factor - metabolism; Transcription, Genetic; Tumor Cells, Cultured; Tyrphostins - pharmacology
• ISSN: 1535-7163; 1538-8514
• DOI: 10.1158/1535-7163.MCT-05-0235

Up-regulated signal transducers and activators of transcription (STAT)–mediated signaling is believed to contribute to the pathogenesis of a variety of solid and hematologic cancers. Consequently, inhibition of STAT-mediated signaling has recently been proposed as a potential new therapeutic approach to the treatment of cancers. Having shown previously that the pan–cyclin-dependent kinase inhibitor flavopiridol binds to DNA and seems to kill cancer cells via that process in some circumstances, we evaluated the hypothesis that flavopiridol might consequently disrupt STAT3/DNA interactions, attenuate STAT3-directed transcription, and down-regulate STAT3 downstream polypeptides, including the antiapoptotic polypeptide Mcl-1. SDS-PAGE/immunoblotting and reverse transcription-PCR were used to assess RNA and polypeptide levels, respectively. DNA cellulose affinity chromatography and a nuclear elution assay were used to evaluate the ability of flavopiridol to disrupt STAT3/DNA interactions. A STAT3 luciferase reporter assay was used to examine the ability of flavopiridol to attenuate STAT3-directed transcription. Colony-forming assays were used to assess cytotoxic synergy between flavopiridol and AG490. Flavopiridol was found to ( a ) disrupt STAT3/DNA interactions (DNA cellulose affinity chromatography and nuclear elution assay), ( b ) attenuate STAT3-directed transcription (STAT3 luciferase reporter assay), and ( c ) down-regulate the STAT3 downstream antiapoptotic polypeptide Mcl-1 at the transcriptional level (reverse transcription-PCR and SDS-PAGE/immunoblotting). Furthermore, flavopiridol, but not the microtubule inhibitor paclitaxel, could be combined with the STAT3 pathway inhibitor AG490 to achieve cytotoxic synergy in A549 human non–small cell lung cancer cells. Collectively, these data suggest that flavopiridol can attenuate STAT3-directed transcription in a targeted fashion and may therefore be exploitable clinically in the development of chemotherapy regimens combining flavopiridol and other inhibitors of STAT3 signaling pathways. [Mol Cancer Ther 2006;5(1):138–48]