The Cannabinoid WIN 55,212-2 Decreases Specificity Protein Transcription Factors and the Oncogenic Cap Protein eIF4E in Colon Cancer Cells

Abstract

2,3-Dihydro-5-methyl-3-([morpholinyl]methyl)pyrollo(1,2,3-de)-1,4-benzoxazinyl]-[1-naphthaleny]methanone [WIN 55,212-2 (WIN)] is a synthetic cannabinoid that inhibits RKO, HT-29 and SW480 cell growth, induced apoptosis, and downregulated expression of survivin, cyclin D1, epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF) and its receptor (VEGFR1). WIN also decreased expression of specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4, and this is consistent with the observed downregulation of the aforementioned Sp-regulated genes. In addition, we also observed by RNA interference (RNAi) that the oncogenic cap protein eIF4E was an Sp-regulated gene also downregulated by WIN in colon cancer cells. WIN-mediated repression of Sp proteins was not affected by CB receptor antagonists or by knockdown of the receptor but was attenuated by the phosphatase inhibitor sodium orthovanadate or by knockdown of protein phosphatase 2A (PP2A). WIN-mediated repression of Sp1, Sp3 and Sp4 was due to PP2A-dependent downregulation of microRNA-27a (miR-27a) and induction of miR-27a-regulated ZBTB10 which has previously been characterized as an “Sp repressor”. The results demonstrate that the anticancer activity of WIN is due, in part, to PP2A-dependent disruption of miR-27a:ZBTB10 and ZBTB10-mediated repression of Sp transcription factors and Sp-regulated genes including eIF4E.

Mechanism of Metformin-dependent Inhibition of Mammalian Target of Rapamycin (mTOR) and Ras Activity in Pancreatic Cancer

“…However, knockdown of Sp1, Sp3, and Sp4 also decreased activation of mTOR and mTORregulated kinases/genes, suggesting that inhibition of mTOR by metformin is due, in part, to Sp down-regulation. Metformininduced down-regulation of Sp1, Sp3, and Sp4 was phosphatase-dependent in Panc1 cells (31), and similar results were observed in colon cancer cell lines that were treated with a synthetic cannabinoid (WIN 55,212-2) that also decreases expression of Sp transcription factors (36). Moreover the effects of both metformin and WIN 55,212-2 on expression of Sp1, Sp3, and Sp4 were inhibited in cells cotreated with the phosphatase inhibitor SOV, and similar results were observed in Panc28 and L3.6pL cells treated with SOV (data not shown).…”

“…Moreover, knockdown of Sp1 in pancreatic cancer cells decreases growth and invasion and induces apoptosis, confirming the pro-oncogenic functions of this factor (49). These results suggest that drugs such as metformin and other agents (31)(32)(33)(34)(35)(36)39) that target Sp1, Sp3, and Sp4 represent a class of new mechanism-based drugs that can be used in combination therapies for treating this deadly disease.…”

“…This involved down-regulation of specificity protein (Sp) transcription factors Sp1, Sp3, and Sp4 and pro-oncogenic Sp-regulated genes such as bcl2, fatty acid synthase (FAS), survivin, vascular endothelial growth factor (VEGF), and VEGF receptor 1 (VEGFR1) (31). The anticancer activities of metformin are also similar to * This work was supported, in whole or in part, by National Institutes of Health that observed after knockdown of Sp1 or all three Sp proteins by RNA interference in cancer cells, and this includes growth inhibition, induction of apoptosis, reversal of epithelial to mesenchymal transition, and decreased migration/invasion (32)(33)(34)(35)(36). Metformin also inhibits NFB and decreases cyclin D1 and ErbB2 in cancer cell lines (13,20,27,28), and these gene products are also decreased after Sp1, Sp3, and Sp4 silencing by RNAi or by other drugs that down-regulate Sp proteins (32)(33)(34)(35)(36).…”

Sp1 transcription factor: A long-standing target in cancer chemotherapy

“…There are several natural products, other than curcumin and betulinic acid mentioned above, which also appear to affect Sp factors, such as some cannabinoids that can decrease the expression of the Sp-family of transcription factors (Sreevalsan & Safe, 2013) or resveratrol (3,5,4'-trihydroxy-trans-stilbene), a 'nutraceutical' compound obtained from grapes and other fruits, which represses cell growth and can inhibit Sp1 directly .…”

Colorectal Cancers

“…Other reported anticancer approaches to translational inhibition in CRC include use of patellazoles (Richardson et al 2005); phenethyl isothiocyanate (a constituent of many edible cruciferous vegetables) (Hu et al 2007); curcumin (a natural polyphenol product of the plant Curcuma longa) (Johnson et al 2009); proteasome inhibitor MG-132 (Wu et al 2009); siRNA-mediated gene silencing of mTOR (Zhang et al 2009); enzastaurin (Dumstorf et al 2010); aspirin (Din et al 2012); synthetic cannabinoids (Sreevalsan and Safe 2013); and the antimalarial compound dihydroartemisinin (DHA) (Odaka et al 2014). However, specificity of their effect on the translation machinery and/or anticancer efficacy needs further studies.…”