RTVP-1 promotes mesenchymal transformation of glioma via a STAT-3/IL-6-dependent positive feedback loop.

Glioblastomas (GBMs), the most aggressive primary brain tumors, exhibit increased invasiveness and resistance to anti-tumor treatments. We explored the role of RTVP-1, a glioma-associated protein that promotes glioma cell migration, in the mesenchymal transformation of GBM. Analysis of The Cancer Genome Atlas (TCGA) demonstrated that RTVP-1 expression was higher in mesenchymal GBM and predicted tumor recurrence and poor clinical outcome. ChiP analysis revealed that the RTVP-1 promoter binds STAT3 and C/EBPß, two master transcription factors that regulate mesenchymal transformation of GBM. In addition, IL-6 induced RTVP-1 expression in a STAT3-dependent manner. RTVP-1 increased the migration and mesenchymal transformation of glioma cells. Similarly, overexpression of RTVP-1 in human neural stem cells induced mesenchymal differentiation, whereas silencing of RTVP-1 in glioma stem cells (GSCs) decreased the mesenchymal transformation and stemness of these cells. Silencing of RTVP-1 also increased the survival of mice bearing GSC-derived xenografts. Using gene array analysis of RTVP-1 silenced glioma cells we identified IL-6 as a mediator of RTVP-1 effects on the mesenchymal transformation and migration of GSCs, therefore acting in a positive feedback loop by upregulating RTVP-1 expression via the STAT3 pathway. Collectively, these results implicate RTVP-1 as a novel prognostic marker and therapeutic target in GBM.

MicroRNA-137 is downregulated in glioblastoma and inhibits the stemness of glioma stem cells by targeting RTVP-1.

Glioblastomas (GBM), the most common and aggressive malignant astrocytic tumors, contain a small subpopulation of cancer stem cells (GSCs) that are implicated in therapeutic resistance and tumor recurrence. Here, we study the expression and function of miR-137, a putative suppressor miRNA, in GBM and GSCs. We found that the expression of miR-137 was significantly lower in GBM and GSCs compared to normal brains and neural stem cells (NSCs) and that the miR-137 promoter was hypermethylated in the GBM specimens. The expression of miR-137 was increased in differentiated NSCs and GSCs and overexpression of miR-137 promoted the neural differentiation of both cell types. Moreover, pre-miR-137 significantly decreased the self-renewal of GSCs and the stem cell markers Oct4, Nanog, Sox2 and Shh. We identified RTVP-1 as a novel target of miR-137 in GSCs; transfection of the cells with miR-137 decreased the expression of RTVP-1 and the luciferase activity of RTVP-1 3'-UTR reporter plasmid. Furthermore, overexpression of RTVP-1 plasmid lacking its 3'-UTR abrogated the inhibitory effect of miR-137 on the self-renewal of GSCs. Silencing of RTVP-1 decreased the self-renewal of GSCs and the expression of CXCR4 and overexpression of CXCR4 abrogated the inhibitory effect of RTVP-1 silencing on GSC self-renewal. These results demonstrate that miR-137 is downregulated in GBM probably due to promoter hypermethylation. miR-137 inhibits GSC self-renewal and promotes their differentiation by targeting RTVP-1 which downregulates CXCR4. Thus, miR-137 and RTVP-1 are attractive therapeutic targets for the eradication of GSCs and for the treatment of GBM.

Chemopreventive effects of Coltect, a novel dietary supplement, alone and in combination with 5-aminosalicylic acid in 1,2-dimethylhydrazine-induced colon cancer in rats.

OBJECTIVES: Coltect is a novel dietary supplement containing curcumin, green tea and selenomethionine. Previous reports have suggested that these agents can prevent colorectal cancer (CRC). The present study examined the chemopreventive effect of Coltect alone or combined with 5-aminosalicylic acid (5-ASA) using the 1,2-dimethylhydrazine (DMH) model in rats. METHODS: The effect of Coltect was examined on HT-29 CRC cells by growth inhibition assay. Apoptosis was determined by annexin V-FITC/PI staining. Male rats were injected with DMH in vivo and treated with Coltect 150 mg/kg, 5-ASA 50 mg/kg or their combination, by oral gavage. Aberrant crypt foci (ACF) were identified by methylene blue staining. RESULTS: HT-29 cells exhibited a dose-dependent response to Coltect. Part of the growth inhibition can be explained by the induction of mild-moderate apoptosis in cancer cells (28%) compared with the untreated cells (10%). In the in vivo model, the average number of ACF was divided into small (1-3 crypts) or large (≥4 crypts). The Coltect compound reduced the number of small and large ACF similarly to 5-ASA (40% reduction). This reduction was amplified by combining the two agents (70% reduction). CONCLUSION: Coltect inhibits the growth of colon cancer cells, induces apoptosis and inhibits ACF development. Furthermore, it augments the growth inhibitory effect of 5-ASA in vivo. This may be clinically important since this safe dietary supplement-drug combination can be administered as a chemopreventive regimen for the treatment of CRC.

Curcumin potentiates the pro-apoptotic effects of sulindac sulfone in colorectal cancer.

OBJECTIVE: The use of sulindac sulfone (SFN) for colorectal cancer (CRC) therapy is limited due to its toxicity. The present study was carried out to examine whether curcumin, a novel chemopreventive agent, can potentiate the effects of low dosages of SFN in CRC treatment. METHODS: HT-29 CRC cells were exposed to SFN (200 - 400 microM), curcumin (5 - 10 microM) or their combination. The cytotoxic effects of the drugs were evaluated using growth inhibition assays. Annexin V/PI and cell cycle analysis were employed to study the mechanism of action of the drugs. The therapeutic efficacy of the drugs in vivo was examined using the aberrant crypt foci (ACF) model. The treatment groups included eight rats/group. RESULTS: Treatment of cells with curcumin and SFN resulted in a synergistic inhibitory effect of 50 - 90% (p < 0.005) on cell growth. Growth inhibition was associated with inhibition of proliferation, G2/M arrest and induction of apoptosis. Administration of curcumin (0.6%) and SFN (0.06%) to 1, 2-dimethylhydrazine treated rats significantly reduced (by 75%, p < 0.01) the number of ACF. CONCLUSIONS: Curcumin augments the therapeutic effects of SFN. This may be clinically important since the addition of curcumin to low dosages of SFN may encourage a safer and potent combinatorial treatment regimen for CRC.

Gene therapy approach in prostate cancer cells using an active Wnt signal.

BACKGROUND: Functional activation of beta-catenin/T-cell factor (Tcf) signaling plays an important role in the early events of carcinogenesis. In past recent years accumulated evidence has demonstrated a significant role for the Wnt pathway in the development and progression of human prostate cancer. The objective of the current study was to use a gene-targeting approach to selectively kill human prostate cancer cells with activated beta-catenin/Tcf signaling. METHODS: A recombinant adenovirus that carries a lethal gene (PUMA) under the control of a beta-catenin/T-cell factor (Tcf)-responsive promoter (Ad-TOP-PUMA), was used to selectively target human prostate cancer cells (PC-3) in which the beta-catenin/Tcf pathway is activated, and compared its killing efficiency in cancer cells in which this pathway is inactive (DU145 cells). Ad-FOP-PUMA, carrying a mutant Tcf binding site, was used as a control virus. Cell viability was measured by methylene blue assay, and the level of beta-catenin/Tcf activity was measured by luciferase assay. RESULTS: The Ad-TOP-PUMA adenovirus inhibited PC-3 cell growth in a dose and time-dependent fashion, but did not had any effect on DU145 cell growth. CONCLUSIONS: Selective targeting of prostate cancer cells with the activated beta-catenin pathway may be a novel and effective therapy in prostate cancer.

Celecoxib and curcumin additively inhibit the growth of colorectal cancer in a rat model.

BACKGROUND: Multiple studies have indicated that specific COX-2 inhibitors may prevent CRC. However, the long-term use of COX-2 inhibitors is not toxicity-free and may be limited due to its cardiovascular side effects. The present study was carried out to examine the chemopreventive effects of celecoxib and curcumin alone and in combination using the 1,2-dimethylhydrazine (DMH) rat model. METHODS: Male rats were injected with DMH and randomly divided into four groups that consumed one of the following diets: (a) AIN-076 control diet; (b) AIN-076/curcumin (0.6%); (c) AIN-076/celecoxib (0.16%), or (d) AIN-076/celecoxib (0.16%) and curcumin (0.6%). Aberrant crypt foci (ACF) were identified by intensive staining with methylene blue in comparison to the surrounding normal crypts. RESULTS: The average number of ACF per rat colon was 64.2 +/- 3 in the control group, 39 +/- 5 and 47 +/- 10 for the curcumin- and celecoxib-treated group, respectively, and 24.5 +/- 6 in the group that had received both agents. CONCLUSIONS: In vivo, curcumin augments the growth inhibitory effect of celecoxib. This may be clinically important as this dose of celecoxib can be achieved in human serum following standard anti-inflammatory dosing of 100 mg.