Curcumin and synthetic analogs induce reactive oxygen species and decreases specificity protein (Sp) transcription factors by targeting microRNAs

Abstract

BackgroundCurcumin inhibits growth of several cancer cell lines, and studies in this laboratory in bladder and pancreatic cancer cells show that curcumin downregulates specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 and pro-oncogenic Sp-regulated genes. In this study, we investigated the anticancer activity of curcumin and several synthetic cyclohexanone and piperidine analogs in colon cancer cells.MethodsThe effects of curcumin and synthetic analogs on colon cancer cell proliferation and apoptosis were determined using standardized assays. The changes in Sp proteins and Sp-regulated gene products were analysed by western blots, and real time PCR was used to determine microRNA-27a (miR-27a), miR-20a, miR-17-5p and ZBTB10 and ZBTB4 mRNA expression.ResultsThe IC50 (half-maximal) values for growth inhibition (24 hr) of colon cancer cells by curcumin and synthetic cyclohexanone and piperidine analogs of curcumin varied from 10 μM for curcumin to 0.7 μM for the most active synthetic piperidine analog RL197, which was used along with curcumin as model agents in this study. Curcumin and RL197 inhibited RKO and SW480 colon cancer cell growth and induced apoptosis, and this was accompanied by downregulation of specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 and Sp-regulated genes including the epidermal growth factor receptor (EGFR), hepatocyte growth factor receptor (c-MET), survivin, bcl-2, cyclin D1 and NFκB (p65 and p50). Curcumin and RL197 also induced reactive oxygen species (ROS), and cotreatment with the antioxidant glutathione significantly attenuated curcumin- and RL197-induced growth inhibition and downregulation of Sp1, Sp3, Sp4 and Sp-regulated genes. The mechanism of curcumin-/RL197-induced repression of Sp transcription factors was ROS-dependent and due to induction of the Sp repressors ZBTB10 and ZBTB4 and downregulation of microRNAs (miR)-27a, miR-20a and miR-17-5p that regulate these repressors.ConclusionsThese results identify a new and highly potent curcumin derivative and demonstrate that in cells where curcumin and RL197 induce ROS, an important underlying mechanism of action involves perturbation of miR-ZBTB10/ZBTB4, resulting in the induction of these repressors which downregulate Sp transcription factors and Sp-regulated genes.

Combined Effects of Curcumin and Triptolide on an Ovarian Cancer Cell Line

“…Therefore, alternative strategy would be one that not only decreases the dose of chemotherapeutics but enhances the sensitivity of cancer cells to chemotherapeutics. Recently, tumor therapy by traditional Chinese herb such as curcumin (Gandhy et al, 2012;Khaw et al, 2013;Blakemore et al, 2013) and triptolide (Phillips et al, 2007;Matsui et al, 2008;Antonoff et al, 2009; Zhu et al, 2012; Dudeja et al, 2013) is becoming more and more attractive (Du et al, 2013). We therefore attempted to examine the effects of curcumin and triptolide on ovarian cancer.…”

Targeting Apoptosis Pathways in Cancer—Letter

“…For example, the authors have summarized the effects of various proapoptotic agents that act through two interrelated pathways, namely "mitochondrial-mediated" and "reactive oxygen species (ROS)-mediated" apoptosis because drugs targeting mitochondria often induce ROS. Previous studies in this laboratory have demonstrated that natural products such as curcumin, betulinic acid, phenethyl isothiocyanate (PEITC), piperlongumine, and celastrol, which induce ROS and apoptosis, also downregulate specificity protein (Sp) transcription factors Sp1, Sp3, and Sp4, which are highly expressed in cancer cells (2)(3)(4)(5)(6). For most of these studies, compound-induced apoptosis and compound-induced downregulation of Sp transcription factors were reversed in cancer cells after cotreatment with antioxidants.…”

Impact of curcumin on the regulation of microRNAs in colorectal cancer

“…This effect was likely due to the demethylation of miR-34a promoter induced by CDF. There is also evidence indicating that curcuminoids decrease the expression of miR-27a, miR-20a, and miR-17-5p, thereby up-regulating ZBTB10 and ZBTB4, down-regulating the specificity protein transcription factors (Sp1, Sp3, Sp4) and Sp-regulated genes, and inhibiting multidrug resistance protein 1 which collectively lead to growth suppression and apoptosis of colon cancer cells [26,27].…”

“…Given that microRNAs exhibit a central role in the EMT, the effect of curcumin on the expression of miR-200b, miR-200c, miR-141, miR-429, miR-101, and miR-34a has been explored, and the results have revealed upregulation of these EMT-related miRNAs in 5-fluorouracilresistant cell lines [27]. This suggests that the anti-tumor properties of curcumin in human colorectal cancer cells can be explained, at least in part, by the modulation of EMTsuppressive miRNAs.…”

“…Curcumin has also been shown to down-regulate ZEB1, BMI1, EZH2, SUZ12, and Ring1b that are well-recognized markers of epithelial-mesenchymal transition (EMT), thereby inducing epithelial differentiation in chemo-resistant colorectal cancer cell lines [27]. Given that microRNAs exhibit a central role in the EMT, the effect of curcumin on the expression of miR-200b, miR-200c, miR-141, miR-429, miR-101, and miR-34a has been explored, and the results have revealed upregulation of these EMT-related miRNAs in 5-fluorouracilresistant cell lines [27].…”