Peroxisome proliferator-activated receptor γ-mediated induction of microRNA-145 opposes tumor phenotype in colorectal cancer.

UNLABELLED: MicroRNAs (miRNAs) regulate diverse biological processes by inhibiting translation or inducing degradation of target mRNAs. miR-145 is a candidate tumor suppressor in colorectal carcinoma (CRC). Colorectal carcinogenesis involves deregulation of cellular processes controlled by a number of intertwined chief transcription factors, such as PPARγ and SOX9. Since PPAR family members are able to modulate complex miRNAs networks, we hypothesized a role of miRNA-145 in the interaction between PPARγ and SOX9 in colorectal carcinogenesis. To address this issue, we evaluated gene expression in tissue specimens of CRC patients and we took advantage of invitro models represented by CRC derived cell lines (CaCo2, SW480, HCT116, and HT-29), employing PPARγ activation and/or miRNA-145 ectopic overexpression to analyze how their interplay impact the expression of SOX9 and the development of a malignant phenotype. RESULTS: PPARγ regulates the expression of miR-145 by directly binding to a PPAR response element (PPRE) in its promoter at -1207/-1194bp from the transcription start site. The binding is essential for miR-145 upregulation by PPARγ upon rosiglitazone treatment. Ectopic expression of miR-145, in turn, regulates SOX9 expression through the binding to specific seed motifs. The PPARγ-miR-145-SOX9 axis overarches cell cycle progression, invasiveness and differentiation of CRC derived cell lines. Together, these results suggest that miR-145 is a novel target of PPARγ, acts as a tumor suppressor in CRC cell lines and is a key regulator of intestinal cell differentiation by directly targeting SOX9, a marker of undifferentiated progenitors in the colonic crypts.

Interplay between SOX9, ß-catenin and PPARγ activation in colorectal cancer.

Colorectal carcinogenesis relies on loss of homeostasic mechanisms regulating cell proliferation, differentiation and survival. These cell processes have been reported to be influenced independently by transcription factors activated downstream of the Wnt pathway, such as SOX9 and ß-catenin, and by the nuclear receptor PPARγ. The purpose of this study was to explore the expression levels and functional link between SOX9, ß-catenin and PPARγ in the pathogenesis of colorectal cancer (CRC). We evaluated SOX9, ß-catenin and PPARγ expression levels on human CRC specimens by qPCR and immunoblot detection. We tested the hypothesis that PPARγ activation might affect SOX9 and ß-catenin expression using four colon cancer cell lines (CaCo2, SW480, HCT116, and HT29 cells). In CRC tissues SOX9 resulted up-regulated at both mRNA and protein levels when compared to matched normal mucosa, ß-catenin resulted up-regulated at protein levels, while PPARG mRNA and PPARγ protein levels were down-regulated. A significant relationship was observed between high PPARG and SOX9 expression levels in the tumor tissue and female gender (p=0.005 and p=0.04, respectively), and between high SOX9 expression in the tumor tissue and age (p=0.04) and microsatellite instability (MSI), in particular with MSI-H (p=0.0002). Moreover, treatment with the synthetic PPARγ ligand rosiglitazone induced different changes of SOX9 and ß-catenin expression and subcellular localization in the colon cancer cell lines examined. In conclusion, SOX9, ß-catenin and PPARγ expression levels are deregulated in the CRC tissue, and in colon cancer cell lines ligand-dependent PPARγ activation unevenly influences SOX9 and ß-catenin expression and subcellular localization, suggesting a variable mechanistic role in colon carcinogenesis.

Neoadjuvant chemo-radiotherapy for patients with borderline resectable pancreatic cancer: a meta-analytical evaluation of prospective studies.

CONTEXT: For patients with borderline resectable pancreatic cancer, the benefit of neoadjuvant therapy remains to be defined. OBJECTIVE: We did a systematic search of the literature on this topic. METHODS: Prospective studies where chemotherapy with or without radiotherapy was given before surgery to patients with borderline resectable cancer, were analyzed by a meta-analytical approach. MAIN OUTCOME MEASURES: Primary outcome was surgical exploration and resection rates; tumor response, therapy-induced toxicity, and survival were secondary outcomes. Data were expressed as weighted pooled proportions with 95% confidence intervals (95% CI). RESULTS: Ten studies with 182 participants were included. Following treatment, 69% of patients (95% CI: 56-80%) were brought to surgery and 80% (95% CI: 66-90%) of surgically-explored patients were resected. Eighty-three percent (95% CI: 74-90%) of resected specimens were deemed R0 resections. The weighted fractions of resected patients alive at 1 and 2 years were 61% (95% CI: 48-100%) and 44% (95% CI: 32-59%), respectively. At restaging following neoadjuvant therapy, weighted frequencies for complete/partial response were 16% (95% CI: 9-28%), 69% (95% CI: 60-76%) for stable disease, and 19% (95% CI: 13-25%) for progressive cancer. Treatment-related grade 3-4 toxicity was 32% (95% CI: 21-45%). CONCLUSION: This meta-analysis shows that downstaging of the lesion following neoadjuvant therapies is uncommon for patients with borderline resectable pancreatic cancer. A clear benefit of this regimen could be to spare surgery to patients with progressive disease during the frame-time chemo-radiotherapy is being delivered.