ABSTRACT
BACKGROUND/AIMS: Bromodomain-containing protein 4 (BRD4) and phosphatidylinositol 3-kinase (PI3K) are key oncogenic cascades in colorectal cancer (CRC). SF1126 is a novel and potent PI3K-BRD4 dual inhibitor. METHODS: CRC cells and human colon epithelial cells were treated with SF1126. Cell survival was tested by MTT and soft agar colony formation assays. Cell proliferation was tested by BrdU ELISA method. Cell apoptosis was tested by a TUNEL staining method and Histone DNA ELISA. Western blotting was utilized to test the signaling proteins. A HT-29 xenograft mice model was established to study the anti-tumor activity of SF1126 in vivo. RESULTS: SF1126 potently inhibited the survival, proliferation, and progression of the cell cycle in an established CRC cell line (HT-29) and primary human colon cancer cells. Significant activation of apoptosis was detected in SF1126-treated CRC cells. In CRC cells, SF1126 blocked Akt-mammalian target of rapamycin (mTOR) complex1/2 signaling and downregulated BRD4 target proteins (Myc and cyclin D1). Further studies showed that SF1126 activated p38 signaling in CRC cells. In contrast, the p38 inhibitors or p38 short hairpin RNA inhibited SF1126-induced cytotoxicity and apoptosis in CRC cells. In vivo, subcutaneous administration of SF1126 significantly inhibited HT-29 xenograft tumor growth in nude mice. CONCLUSION: SF1126 inhibits CRC cell growth possibly by targeting PI3K-Akt-mTOR, BRD4, and p38 signaling.
Subject(s)
Cell Cycle Checkpoints/drug effects , Cell Proliferation/drug effects , Chromones/pharmacology , Nuclear Proteins/antagonists & inhibitors , Oligopeptides/pharmacology , Phosphoinositide-3 Kinase Inhibitors , Transcription Factors/antagonists & inhibitors , Animals , Apoptosis/drug effects , Cell Cycle Proteins , Cell Line, Tumor , Chromones/therapeutic use , Colorectal Neoplasms/drug therapy , Colorectal Neoplasms/metabolism , Colorectal Neoplasms/pathology , Humans , Mechanistic Target of Rapamycin Complex 1/metabolism , Mechanistic Target of Rapamycin Complex 2/metabolism , Mice , Mice, Nude , Mitogen-Activated Protein Kinase 14/antagonists & inhibitors , Mitogen-Activated Protein Kinase 14/genetics , Mitogen-Activated Protein Kinase 14/metabolism , Nuclear Proteins/metabolism , Oligopeptides/therapeutic use , Phosphatidylinositol 3-Kinases/metabolism , Proto-Oncogene Proteins c-akt/metabolism , RNA Interference , RNA, Small Interfering/metabolism , Signal Transduction/drug effects , Transcription Factors/metabolism , Transplantation, HeterologousABSTRACT
BACKGROUND: Growth factor mediated activation of RAS-MAP-kinase and PI3-kinase-AKT pathways are critical for the pathogenesis of glioblastoma. The attenuation of PI3-kinase/AKT signaling will be effective in regulating the tumorigenic phenotypes of the glioma cells. METHODS: Glioma cells derived from the brain of the (12) V-Ha-Ras transgenic mice were used to study the effect of PI-3 kinase inhibitor SF1126 on activation of AKT and ERK signaling, proliferation, vitronectin mediated migration and changes in the distribution of cortical actin on vitronectin in the glioma cells in vitro. The anti-tumor effects of SF1126 were also tested in vivo using pre-established tumors (subcutaneous injection of the glioma cells from (12) V-Ha-Ras transgenic mice) in a mouse xenograft model. RESULTS: Our results demonstrate that treatment of LacZ+, GFAP + and PCNA + (12) V-Ras Tg transformed astrocytes with SF1126 and LY294002 blocked the activation of AKT as well as EGF-induced phospho-ERK. Most notably, treatment of SF1126 blocked integrin-dependent migration in transwell and scratch assays and caused a significant change in the organization and distribution of cortical actin on vitronectin in the glioma cells. Moreover, SF1126 treatment inhibited in vitro proliferation of these cells and in vivo growth of pre-established subcutaneous tumors in a xenograft model. CONCLUSION: The present study validate the potent anti-proliferative and anti-migratory activity of SF1126, in a V(12) Ras oncogene driven glioma model and suggest that this effect is mediated potentially through a combined attenuation of PI3-kinase and MAP-kinase signaling pathways.