An inducible knockout mouse to model the cellautonomous role of PTEN in initiating endometrial, prostate and thyroid neoplasias

PTEN is one of the most frequently mutated tumor suppressor genes in human cancers. The role of PTEN in carcinogenesis has been validated by knockout mouse models. PTEN heterozygous mice develop neoplasms in multiple organs. Unfortunately, the embryonic lethality of biallelic excision of PTEN has inhibited the study of complete PTEN deletion in the development and progression of cancer. By crossing PTEN conditional knockout mice with transgenic mice expressing a tamoxifen-inducible Cre-ERT under the control of a chicken actin promoter, we have generated a tamoxifeninducible mouse model that allows temporal control of PTEN deletion. Interestingly, administration of a single dose of tamoxifen resulted in PTEN deletion mainly in epithelial cells, but not in stromal, mesenchymal or hematopoietic cells. Using the mT/mG double-fluorescent Cre reporter mice, we demonstrate that epithelial-specific PTEN excision was caused by differential Cre activity among tissues and cells types. Tamoxifen-induced deletion of PTEN resulted in extremely rapid and consistent formation of endometrial in situ adenocarcinoma, prostate intraepithelial neoplasia and thyroid hyperplasia. We also analyzed the role of PTEN ablation in other epithelial cells, such as the tubular cells of the kidney, hepatocytes, colonic epithelial cells or bronchiolar epithelium, but those tissues did not exhibit neoplastic growth. Finally, to validate this model as a tool to assay the efficacy of anti-tumor drugs in PTEN deficiency, we administered the mTOR inhibitor everolimus to mice with induced PTEN deletion. Everolimus dramatically reduced the progression of endometrial proliferations and significantly reduced thyroid hyperplasia. This model could be a valuable tool to study the cell-autonomous mechanisms involved in PTEN-loss-induced carcinogenesis and provides a good platform to study the effect of anti-neoplastic drugs on PTEN-negative tumors

Optimal protocol for PTEN immunostaining; role of analytical and preanalytical variables in PTEN staining in normal and neoplastic endometrial, breast, and prostatic tissues

In some tumors, phosphatase and tensin homolog (PTEN) inactivation may have prognostic importance and predictive value for targeted therapies. Immunohistochemistry (IHC) may be an effective method to demonstrate PTEN loss. It was claimed that PTEN IHC showed poor reproducibility, lack of standardization, and variable effects of preanalytical factors. In this study, we developed an optimal protocol for PTEN IHC, with clone 6H2.1, by checking the relevance of analytical variables in normal tissue and tumors of endometrium, breast, and prostate. Pattern and intensity of cellular staining and background nonspecific staining were quantified and subjected to statistical analysis by linear mixed models. The proposed protocol showed a statistically best performance (P .001). However, there was a trend of significance for decreased staining and fixation under high temperature. Moreover, staining was better in endometrial aspirates than in matched hysterectomy specimens, subjected to less controlled preanalytical variables (mean histoscores, 80 and 40, respectively; P = .002). A scoring system combining intensity of staining and percentage of positive cells was statistically associated with PTEN alterations (P = .01).The study was done according to the research collaboration with Dako Denmark A/S. The research team was also supported by grants FIS PI100922, Fundación Mutua Madrileña AP75732010, 2009SGR794, RD12/0036/0013, Fundación Asociación Española contra el Cancer, programa de intensificación de la investigación, Instituto Carlos III, Verelst Baarmoederkankerfonds, Leuven, and European Network for Individualized Treatment of Endometrial Carcinoma. F. A. is senior researcher for the research fund Flandersb. Tumor samples were obtained with the support of XarxaCatalana de Bancs de Tumors, the TumorBanc Platform of RTICC, and Red de Biobancos (RD09/0076/00059

The role of morbid obesity in the promotion of metabolic disruptions and non-alcoholic steatohepatitis by Helicobacter Pylori

Helicobacter pylory (HP) infection has been associated to an increased rate of type 2 diabetes (T2D) and liver disease through its effect on insulin resistance and systemic inflammation. However, results are inconstant and no studies exist in morbidly obese patients, in which both insulin resistance and inflammation coexist

FLIP is frequently expressed in endometrial carcinoma and has a role in resistance to TRAIL-induced apoptosis

The FLICE-inhibitory protein (FLIP) plays a key role in the regulation of apoptosis triggered by death ligands. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been shown to induce apoptosis in some types of tumor but not in others. To assess the possible role of FLIP in apoptosis resistance in endometrial carcinoma, we performed an immunohistochemical study on a tissue microarray composed of 95 endometrial carcinomas. We found positive signals in 43% of the cases, as well as a significant difference in FLIP expression between stage I and II tumors. Moreover, we observed that endometrial carcinoma cell lines Ishikawa and KLE did not undergo apoptosis after TRAIL treatment. Cotreatment of these cells with the inhibitor of transcription actinomycin D resulted in a dramatic decrease in cell viability and induced activation of caspase-8. These events coincided with downregulation of FLIP mRNA and protein. Inhibitors of caspase-8 or overexpression of FLIP completely blocked apoptosis induced by actinomycin D plus TRAIL cotreatment. More importantly, downregulation of endogenous FLIP expression by specific siRNAs sensitized endometrial carcinoma cells to TRAIL-induced apoptosis in the absence of actinomycin D. Taken together, our results suggest for the first time a critical role for FLIP in the regulation apoptosis triggered by TRAIL in endometrial carcinoma cells

Abnormalities in the NF-κB family and related proteins in endometrial carcinoma

The NF-κB family of transcription factors regulates a wide variety of cellular processes including cell growth, differentiation, and apoptosis. A tissue microarray was constructed from paraffin wax-embedded blocks from 95 endometrial carcinomas (EC), previously studied for microsatellite instability, as well as for alterations in PTEN, k-RAS and betacatenin. Immunohistochemical evaluation included members of the NF-κB (p50, p65, p52, c-Rel, Rel-B) and the IκB (IκBα, IκBβ, IκBε, Bcl-3) families, as well as putative targets of NF-κB such as Flip, Bcl-xL, Cyclin D1, and oestrogen and progesterone receptors. Results were correlated with the clinical and pathological data. Nuclear immunostaining for members of the NF-κB family was frequent in EC (p50, 20%; p65, 16.5–21.9%; p52, 9.3%; cRel, 48.9%; Rel-B, 15.7%); and it correlated with negativity for members of the IκB family in some cases. There was a statistically significant association between immunoreaction for p50 and p65 (p = 0.006), suggesting activation of the so-called ‘classic form’ of NF-κB, similar to that described in breast cancer. Bcl-3 nuclear immunostaining was detected in 60.7% of cases. The vast majority of p52-positive tumours showed Bcl-3 nuclear immunoreaction (p = 0.038). Immunostaining for putative targets of NF-κB was as follows: Bcl-xL, 76.2% (p = 0.001); Flip 43.0%; Cyclin D1, 64.79%. p65 immunostaining correlated with increased immunoreaction for steroid hormone receptors. No correlation was found between NF-κB nuclear pattern and the presence of microsatellite instability, or alterations in PTEN, kRAS, or beta-catenin. These results suggest that the NF-κB and IκB families of genes may be important in endometrial carcinogenesis, by controlling apoptosis and cell proliferation

Immunohistochemical analysis of PTEN in endometrial carcinoma: a tissue microarray study with a comparison of four commercial antibodies in correlation with molecular abnormalities

The tumor suppressor gene PTEN/MMAC1 is located on chromosome 10q23.3. Inactivation of PTEN, either by mutations, deletions, or promoter hypermethylation, has been identified in a wide variety of tumors. Inactivation of the two alleles of PTEN is required, because it is a tumor suppressor gene. Immunohistochemical staining may be an effective screening method to demonstrate the absence of the protein in tumors exhibiting PTEN inactivation. We studied a tissue microarray, constructed from paraffin-embedded blocks of 95 endometrial carcinomas, 38 of them previously evaluated for alterations in PTEN. We also studied cell blocks obtained from one PTEN-defective endometrial cancer cell line, after transfection with either a plasmid encoding wild-type PTEN or the empty vector. The tumor samples were tested with four different anti-PTEN commercial antibodies: a polyclonal antibody, the monoclonal antibody 28H6, the monoclonal antibody 10P03, and the monoclonal antibody 6.H2.1. Results were correlated with the presence of abnormalities in PTEN, as well as with the immunohistochemical expression of phosphorylated AKT. Antibody 28H6 produced a predominant nuclear staining, while the other three antibodies produced a predominant cytoplasmic staining. There was no significant correlation between the results obtained with the four antibodies. The monoclonal antibody 6.H2.1 was the only one that exhibited a correlation with the presence of molecular alterations in PTEN, and a statistically significant association with immunostaining for phosphorylated AKT (r ¼ 0.249, P ¼ 0.037). The monoclonal antibody 10P03 exhibited an association with phospho-AKT that did not have statistical significance. Both 6.H2.1 and 10P03 antibodies stained PTEN-transfected cells, and were negative in the PTEN-deficient cell line blocks. The polyclonal antibody and the monoclonal antibody 28H6 produced positive staining in PTEN-deficient cell line blocks, suggesting nonspecific staining. The results indicate that monoclonal antibody 6.H2.1 may be a suitable alternative for tumors with inactivation of PTEN

KSR1 Is Overexpressed in Endometrial Carcinoma and Regulates Proliferation and TRAIL-Induced Apoptosis by Modulating FLIP Levels

The Raf/MEK/extracellular signal-regulated kinase (ERK) pathway participates in many processes altered in development and progression of cancer in human beings such as proliferation, transformation, differentiation, and apoptosis. Kinase suppressor of Ras 1 (KSR1) can interact with various kinases of the Raf/MEK/extracellular signal-regulated kinase pathway to enhance its activation. The role of KSR1 in endometrial carcinogenesis was investigated. cDNA and tissue microarrays demonstrated that expression of KSR1 was up-regulated in endometrial carcinoma. Furthermore, inhibition of KSR1 expression by specific small hairpin RNA resulted in reduction of both proliferation and anchorage-independent cell growth properties of endometrial cancer cells. Because inhibition of apoptosis has a pivotal role in endometrial carcinogenesis, the effects of KSR1 in regulation of tumor necrosis factor–related apoptosis-inducing ligand (TRAIL)–induced apoptosis were investigated. KSR1 knock-down sensitized resistant endometrial cell lines to both TRAIL- and Fas-induced apoptosis. Sensitization to TRAIL and agonistic anti-Fas antibody was caused by down-regulation of FLIP (FLICE-inhibitory protein). Also investigated was the molecular mechanism by which KSR1 regulates FLIP protein levels. It was demonstrated that KSR1 small hairpin RNA did not affect FLIP transcription or degradation. Rather, FLIP down-regulation was caused by Fas-associated death domain protein–dependent inhibition of FLIP translation triggered after TRAIL stimulation in KSR1-silenced cells. Re-expression of heterologous KSR1 in cells with down-regulated endogenous KSR1 restored FLIP protein levels and TRAIL resistance. In conclusion, KSR1 regulates endometrial sensitivity to TRAIL by regulating FLIP levels