Tetracycline derivative minocycline inhibits autophagy and inflammation in concanavalin-a-activated human hepatoma cells.

Inhibition of soluble matrix metalloproteinase (MMP) activity is among the non-antibiotic cellular effects exerted by the anti-inflammatory tetracycline derivative minocycline. The impact of minocycline on the signal transduction functions of membrane-bound MMPs is however unknown. We assessed minocycline in a concanavalin-A (ConA)-activated human HepG2 hepatoma cell model, a condition known to increase the expression of membrane type-1 MMP (MT-MMP) and to trigger inflammatory and autophagy processes. We found that minocycline inhibited ConA-induced formation of autophagic acidic vacuoles, green fluorescent microtubule-associated protein 1 light chain 3 (GFP-LC3) puncta formation, gene and protein expression of autophagy biomarker BCL2/adenovirus E1B 19 kDa interacting protein 3 (BNIP3), invasion biomarker MT1-MMP, and inflammation biomarker cyclooxygenase (COX)-2. Gene silencing of MT1-MMP abrogated ConA-induced formation of autophagic acidic vacuoles and ConA-induced expressions of BNIP3 and COX-2. Minocycline was also shown to inhibit ConA-induced signal transducer and activator of transcription 3 (STAT3) phosphorylation as well as gene expression of NANOS1, a biomarker believed to colocalize with MT1-MMP and the specific silencing of which further inhibited ConA-induced STAT3 phosphorylation. Collectively, our data demonstrate that part of minocycline's effects on autophagy could be exerted through the inhibition of MT1-MMP signaling functions, which contribute to the autophagy and inflammatory phenotype of ConA-activated HepG2 cells.

Decreasing stearoyl-CoA desaturase-1 expression inhibits ß-catenin signaling in breast cancer cells.

Stearoyl-CoA desaturase-1 (SCD1) is an endoplasmic reticulum anchored enzyme catalyzing the synthesis of monounsaturated fatty acids, mainly palmytoleyl-CoA and oleyl-CoA. Recent studies have revealed a function for SCD1 in the modulation of signaling processes related to cell proliferation, survival and transformation to cancer. We used MCF7 and MDA-MB-231 cells to analyze the role of SCD1 in the metastatic acquisition of breast cancer cells. Silencing SCD1 expression in breast cancer cells has no effect on cell viability but the levels of cell proliferation, cell cycle genes' expressions and the phosphorylation state of ERK1/2 MAPK are significantly reduced. Decreasing SCD1 expression also reduces the level of GSK3 phosphorylation, indicating higher activity of the kinase. Using cells fractionation, immunofluorescence and a ß-catenin/TCF-responsive reporter construct, we demonstrate that lowering SCD1 expression leads to a decrease of ß-catenin amounts within the nucleus and to inhibition of its transactivation capacity. Moreover, MDA-MB-231 cells transfected with the SCD1 siRNA show a lower invasive potential than the control cells. Taken together, our data demonstrate that low SCD1 expression is associated with a decrease in the proliferation rate of breast cancer cells associated with a decrease in ERK1/2 activation. SCD1 silencing also inhibits GSK3 phosphorylation, lowering ß-catenin translocation to the nucleus, and, subsequently, its transactivation capacity and the expression of its target genes. Finally, we show that silencing SCD1 impairs the epithelial to mesenchymal transition-like behavior of the cells, a characteristic of metastatic breast cancer.

Evaluation of microsatellite instability, MLH1 expression and hMLH1 promoter hypermethylation in colorectal carcinomas among Tunisians patients.

BACKGROUND: About 10% to 15% of sporadic colorectal cancers demonstrate high level of microsatellite instability that is generally associated with aberrant methylation of hMLH1 promoter. AIM: To investigate the association between MSI status, hMLH1 protein expression and methylation status of the hMLH1 promoter in a cohort of Tunisian sporadic colorectal cancer. METHODS: Expression of MLH1 and MSH2 was determined by immunohistochemistry and the MSI status was analysed by microfluid-based on-chip electrophoresis. Methylation of the hMLH1 gene promoter was determined by methylation-specific PCR. RESULTS: Of the 150 colorectal cancers 57% were MSS, 28% were MSI-L and 15%were MSI-H. MSI-H tumors were more frequently right-sided, exhibited a stage III of TNM and tended more to be mucinous. The MSI status had no effect on overall patient survival. Most of the MSS/MSI-L 79% cancers were unmethylated at the hMLH1 promoter, while 26% MSI-H cancers were unmethylated. 84% of MSS and MSI-L expressed MLH1 and 52% of MSI-H expressed MLH1. Of the methylated MSI-H cases, 35% expressed MLH1 protein while 100% of the unmethylated MSI-H were positive for MLH1 staining. Of 11 MSI-H cancers with loss of MLH1 expression, all cases were also methylated while 50% MSI-H cancers with positive immunostaining for MLH1 were methylated at the hMLH1 promoter. CONCLUSION: Our study showed that MSI-H phenotype was mucinous, right-side and exhibit stade III of TNM. The relative correlation of MLH1 expression and promotor hypermethylation of hMLH1 for the MSI status is similar to that reported for several study.

Impact of MDM2 polymorphism: increased risk of developing colorectal cancer and a poor prognosis in the Tunisian population.

INTRODUCTION: MDM2 was originally identified as an oncoprotein that binds to p53 and inhibits p53-mediated transactivation. Scientists have described functional single-nucleotide polymorphisms (SNP) in the MDM2 gene. They showed that the genotype of SNP 309 induces an increase in the level of MDM2 protein, which causes attenuation of the p53 pathway. In this study, we sought to investigate whether this polymorphism was related to risk of colorectal cancer and whether there were relationships between SNP 309 and protein expression or clinicopathological variables in Tunisian patients. MATERIALS AND METHODS: To investigate the effect of this polymorphism in colorectal cancer pathogenesis, we genotyped 167 patients and 167 blood donors. Immunohistochemistry was performed on normal mucosa and tumor. RESULTS: The rates of MDM2 genotypes were 6.6% for wild-type (T/T) and 93.4% for the SNP 309 polymorphic genotype (T/G and G/G) in patients and 38.3 and 61.7% in controls, respectively. There were significant differences in the frequencies of genotypes between patients and controls (P<0.01). We did not find any relationship between genotypes and clinicopathological features of patients, except in the case of the nonmucinous histological subtype (P=0.001). Moreover, we found that patients with the wild-type genotype (T/T) had significantly more favorable clinical outcome than did patients with the SNP 309 genotype (T/G, G/G) (P=0.005). In addition, we found an association between positive expression of p53 and polymorphic genotypes of MDM2 (T/G, G/G) (P=0.037). There was a significant association between tumoral immunostaning and MDM2 polymorphism (P=0.01). CONCLUSION: Our results suggest that the MDM2 polymorphism is significantly associated with colorectal cancer risk and may provide useful prognostic information for Tunisian patients with colorectal cancer.