PTEN/MMAC1/TEP1 in signal transduction and tumorigenesis

Relationship between mismatch repair protein, RAS, BRAF, PIK3CA gene expression and clinicopathological characteristics in elderly colorectal cancer patients

BACKGROUND

Colorectal cancer (CRC) is common in elderly patients. Mismatch repair (MMR) protein deletion is one of the causes of CRC. The RAS (KRAS/NRAS), BRAF, and PIK3CA genes are important gene targets in CRC treatment and are closely related to the prognosis and survival of patients. However, little is known regarding the relationship between the expression of MMR, RAS, BRAF, PIK3CA and the clinicopathological features in CRC patients.

AIM

To analyze the relationship between the expression of MMR, RAS, BRAF, PIK3CA and the clinicopathological features in CRC.

METHODS

A total of 327 elderly patients with CRC were enrolled, and immuno-histochemistry was used to detect the MMR protein. Real-time quantitative polymerase chain reaction was used to detect the RAS (KRAS/NRAS), BRAF, and PIK3CA genes. The clinicopathological data of the patients were recorded and analyzed by SPSS 19.0 statistical software.

RESULTS

In 327 elderly patients with CRC, the rate of MMR protein loss was 9.79% (32/327), and the deletion rate of four MMR proteins (MSH2, MSH6, MLH1, PMS2) was 1.83% (6/327), 3.06% (10/327), 7.65% (25/327), and 7.65% (25/327), respectively. There were no significant differences between MMR protein deletion and sex, pathological type, tumor morphology, differentiation degree or lymph node metastasis (P > 0.05), but there was a significant difference between MMR protein deletion and tumor diameter and tumor location (P = 0.048/P = 0.000). The mutation rates of the KRAS, NRAS, BRAF and PIK3CA genes in elderly CRC patients were 44.95% (147/327), 2.45% (8/327), 3.36% (11/327) and 2.75% (9/327), respectively; the KRAS gene mutation was closely related to tumor morphology (P = 0.002) but not to other clinicopathological features (P > 0.05), and there were no significant differences between NRAS gene mutation and clinicopathological features (P > 0.05). The BRAF gene mutation showed a significant difference in pathological type, tumor location, differentiation degree and lymph node metastasis (P < 0.05), but was not correlated with sex, tumor size and tumor morphology (P > 0.05). The PIK3CA gene mutation showed no significant differences in the above clinicopathological characteristics (P > 0.05). Significant differences were observed between MMR protein deletion and KRAS, BRAF, and PIK3CA gene mutations in elderly CRC patients (P = 0.044, P = 0.000, P = 0.003, respectively), but there was no significant difference between MMR protein deletion and NRAS mutation (P > 0.05).

CONCLUSION

In elderly CRC patients, the tumor is mainly located in the right colon, and the deletion rate of MMR protein is higher when the tumor diameter is greater than or equal to 5 cm; the deletion rate of MLH1 and PMS2 is more common; the mutation rate of KRAS gene is higher than that of the NRAS, BRAF and PIK3CA genes, the BRAF gene mutation has different degrees of correlation with clinicopathological characteristics; when the MMR protein is deleted, the BRAF and PIK3CA gene mutations are often present, and the KRAS gene mutation rate is low.

Expression of protein tyrosine phosphatases and Bombyx embryonic development

Protein phosphorylation is an integral component of signal transduction pathways within eukaryotic cells, and it is regulated by coordinated interactions between protein kinases and protein phosphatases. Our previous study demonstrated differential expressions of serine/threonine protein phosphatases (PP2A and calcineurin) between diapause and developing eggs in Bombyx mori. In the present study, we further investigated expression of protein tyrosine phosphatases (PTPs) in relation to the Bombyx embryonic development. An immunoblot analysis showed that eggs contained the proteins of the 51-kDa PTP 1B (PTP1B), the 55-kDa phosphatase and tensin homologue (PTEN), and the 70-kDa Src homology 2 (SH2) domain-containing phosphatase 2 (SHP2), which undergo differential changes between diapause and developing eggs. Protein level of PTP1B and PTEN in eggs whose diapause initiation was prevented by HCl gradually increased toward embryonic development. The protein level of SHP2 also showed a dramatic increase on days 7 and 8 after HCl treatment. However, protein levels of PTP1B, PTEN, and SHP2 in diapause eggs remained at low levels during the first 9 days after oviposition. These differential changing patterns in protein levels were further confirmed using both non-diapause eggs and eggs in which diapause had been terminated by chilling of diapausing eggs at 5 °C for 70 days and then were transferred to 25 °C. Direct determination of PTP enzymatic activities showed higher activities in developing eggs (HCl-treated eggs, non-diapause eggs, and chilled eggs) compared to those in diapause eggs. Examination of temporal changes in mRNA expression levels of PTP1B, PTEN, and SHP2 did not show significant differences between diapause eggs and HCl-treated eggs except high expression in SHP2 variant B during the later embryonic development in HCl-treated eggs. These results demonstrate that higher protein levels of PTP1B, PTEN, and SHP2 and increased tyrosine phosphatase enzymatic activities in developing eggs are likely related to embryonic development of B. mori.

MicroRNA and Diabetic Complications: A Clinical Perspective

SIGNIFICANCE

The rising global prevalence of diabetes and its debilitating complications give rise to significant disability and premature mortality. Due to the silent nature of diabetes and its vascular complications, and limitations in current methods for detection, there is a need for novel biomarkers for early detection and prognosis. Recent Advances: Metabolic memory and epigenetic factors are important in the pathogenesis of diabetic complications and interact with genetic variants, metabolic factors, and clinical risk factors. Micro(mi)RNAs interact with epigenetic mechanisms and pleiotropically mediate the effects of hyperglycemia on the vasculature. Utilizing mature profiling techniques and platforms, an increasing number of miRNA signatures and interaction networks have been identified for diabetes and its related cardiorenal complications. As a result, these short, single-stranded molecules are emerging as potential diagnostic and predictive tools in human studies, and may function as disease biomarkers, as well as treatment targets.

CRITICAL ISSUES

However, there is complex interaction between the genome and epigenome. The regulation of miRNAs may differ across species and tissues. Most profiling studies to date lack validation, often requiring large, well-characterized cohorts and reliable normalization strategies. Furthermore, the incremental benefits of miRNAs as biomarkers, beyond prediction provided by traditional risk factors, are critical issues to consider, yet often neglected in published studies.

FUTURE DIRECTIONS

All in all, the future for miRNA-based diagnostics and therapeutics for diabetic complications appears promising. Improved understanding of the complex mechanisms underlying miRNA dysregulation, and more well-designed studies utilizing prospective samples would facilitate the translation to clinical use.

Alcohol or Not: A Review Comparing Initial Mechanisms, Contributing Factors, and Liver Transplantation Outcomes Between Alcoholic and Nonalcoholic Steatohepatitis

Chronic liver diseases take many forms; alcohol-related liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD) are two common illnesses that potentially lead to cirrhosis, liver failure, and liver cancer. It is estimated that a quarter of heavy drinkers develop ALD and the same portion of people without heavy drinking habits have NAFLD. Alcohol intake is regularly used to differentiate NAFLD from ALD; however, diagnosis based on the discrimination threshold may be suboptimal when facing an obese patient with a high level of alcohol exposure. Therefore, understanding the common and/or different mechanism(s) driving each disease is extremely important. The ‘two-hit’ or ‘multi-hit’ hypothesis is used to explain the pathogenesis of both diseases. The ‘first hit’ refers to developing steatosis, the accumulation of fat components in the liver, and the ‘second hits’ are factors leading to oxidative stress, inflammation, and fibrosis, such as metabolic syndromes (e.g., morbid obesity, hyperglycaemia, hyperlipidaemia, disturbed circadian cycles, and altered intestinal microbiota) and environmental toxins (e.g., cigarette smoke and pollutants). Heritable factors also affect the probability and disease progression of both ALD and NAFLD. Whereas PNPLA3 and TM6SF2 variants are influential genetic risk factors for the diseases, epigenetic factors, such as DNA methylation, post-translational histone modifications, and small non-coding RNA, are of paramount importance. Moreover, considering that both ALD and NAFLD patients may eventually develop end-stage liver disease and require liver transplantation, the authors extensively investigated the worldwide outcomes from original literature for these two aetiologies, and the results showed no obvious differences in post-transplantation survival between them. Precise percentage determination of these two aetiologies contributing to steatohepatitis and its secondary injuries in the future would allow for better strategies for therapeutic and preventive intervention.

miR-494 protects pancreatic β-cell function by targeting PTEN in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is one of the most common pregnancy complications characterized by insulin resistance and pancreatic β-cell dysfunction. Increasing evidence suggests that microRNAs (miRNAs) play key roles in the diverse types of diabetes, including GDM. However, the underlying mechanisms remain largely unknown. The purpose of this study is to investigate the role of microRNAs in GDM. The microarray data of dysregulated miRNAs in blood and placenta was retrieved in the GEO dataset under the accession number GSE19649. Quantitative reverse transcription PCR (qRT-PCR) was performed to analyze the expression levels of miR-494 in peripheral blood from twenty pairs of gestational diabetes (GDM) women and healthy women. Then, we investigated the effects of miR-494 on the insulin secretion of pancreatic β-cells. Moreover, the role of this miR-494 in regulating the proliferation and apoptosis of pancreatic β-cells were determined by MTT assay and flow cytometry, respectively in INS1 cells transfected with a miR-494 mimic or inhibitor. In addition, the direct target of miR-494 was confirmed using 3' untranslated region (UTR) luciferase reporter assay. Our data demonstrated that the miR-494 level was significantly decreased in the blood of GDM patients, and the low level was associated with a high concentration of blood glucose. Furthermore, overexpression of miR-494 improved pancreatic β-cell dysfunction by enhancing insulin secretion and total insulin content, inducing cell proliferation, and inhibiting cell apoptosis, whereas miR-494 knockdown exhibited decreased insulin secretion and proliferation, as well as stimulated apoptosis. In addition, phosphatase and tensin homolog (PTEN) which has been shown to play a pivotal role in apoptosis, was proved to be a direct target of miR-494 in pancreatic β-cells. More importantly, siRNA-induced downregulation of PTEN reversed the effects of miR-494 knockdown on insulin secretion, cell proliferation, and apoptosis of pancreatic β-cells.

Immunohistochemical analysis of PTEN, HER2/neu, and ki67 expression in patients with gastric cancer and their association with survival

BACKGROUND

Considering the poor prognosis of patients with gastric cancer, molecular diagnostic and prognostic markers for this cancer should be established. The aims of our study were to assess the correlations between PTEN, HER2/neu, and Ki67 expressions and clinicopathological factors of gastric cancer patients in upper Egypt, as well as their influence on OS and DFS.

PATIENTS AND METHODS

In this descriptive-analytic study, 42 patients with gastric carcinoma treated by postioerative chemoradiation between 2004 and 2014. Pathological review was done. Immunohistochemical staining and evaluation were performed.

RESULTS

All the studied markers were significantly correlated with increased TNM stage. Her2/neu overexpression and positive Ki67 expression were significantly associated with histological grade. High percentage of positive Her2/neu and Ki67expression was found in gastric carcinoma tissue samples which lack PTEN expression. The one-year OS rate for the entire group (n=42) was 77.4%, whereas the DFS rate was 45%. Pathological T stage PTEN status significantly affected both OS (p=0.029 and 0.027 respectively) and DFS (p=0.006 and 0.012 respectively) rates. Multivariate Cox analyses showed that only pathological T stage was an independent prognostic factor affecting OS (P=0. 007, HR: 2.02; 95% CI: 1.2-3.38)and DFS(P<0.0001, HR: 2.69; 95% CI: 1.54-4.69).

CONCLUSION

All the studied molecular markers, was significantly correlated with pathological T stage that significantly affected both OS and DFS rates. These findings indicate that these markers have an important role in gastric cancer growth and dissemination so these markers can be used as a prognostic biomarker. In addition, therapies targeting Her2 and PTEN may help develop novel therapeutics for gastric cancer.

Identification of a Novel lincRNA-p21-miR-181b-PTEN Signaling Cascade in Liver Fibrosis

Previously, we found that long intergenic noncoding RNA-p21 (lincRNA-p21) inhibits hepatic stellate cell (HSC) activation and liver fibrosis via p21. However, the underlying mechanism of the antifibrotic role of lincRNA-p21 in liver fibrosis remains largely unknown. Here, we found that lincRNA-p21 expression was significantly downregulated during liver fibrosis. In LX-2 cells, the reduction of lincRNA-p21 induced by TGF-β1 was in a dose- and time-dependent manner. lincRNA-p21 expression was reduced in liver tissues from patients with liver cirrhosis when compared with that of healthy controls. Notably, lincRNA-p21 overexpression contributed to the suppression of HSC activation. lincRNA-p21 suppressed HSC proliferation and induced a significant reduction in α-SMA and type I collagen. All these effects induced by lincRNA-p21 were blocked down by the loss of PTEN, suggesting that lincRNA-p21 suppressed HSC activation via PTEN. Further study demonstrated that microRNA-181b (miR-181b) was involved in the effects of lincRNA-p21 on HSC activation. The effects of lincRNA-p21 on PTEN expression and HSC activation were inhibited by miR-181b mimics. We demonstrated that lincRNA-p21 enhanced PTEN expression by competitively binding miR-181b. In conclusion, our results disclose a novel lincRNA-p21-miR-181b-PTEN signaling cascade in liver fibrosis and suggest lincRNA-p21 as a promising molecular target for antifibrosis therapy.

PTEN mRNA expression is less pronounced in left- than right-sided colon cancer: a retrospective observational study

BACKGROUND

Several recent studies have reported that patients with metastatic colorectal cancer (CRC) whose primary tumor is located in left side of the colon have more favorable responses to anti-epidermal growth factor receptor (EGFR) antibody therapy than those with right-sided tumors. However, the mechanism for this phenomenon is unknown.

METHODS

Fifty-two cases of primary CRC with liver metastases were analyzed in this retrospective study. The mRNA levels of 19 signal transduction genes in both primary tumor and liver metastases were measured by real-time reverse transcription polymerase chain reaction. The purposes of this study were (1) to determine the correspondence between signal transduction gene expressions in primary tumors and corresponding liver metastases, and (2) to determine whether expression levels of these genes differ by primary tumor location.

RESULTS

mRNA expression levels of 14 of 19 signal transduction genes, including PTEN, ERBB2, MET, HGF, AREG, and EREG, showed significant correlations between the primary tumor and corresponding liver metastases. When the mRNA levels of the primary tumors were compared by tumor location, only PTEN mRNA expression differed significantly between left and right-sided CRC (median PTEN expression: left 1.00 vs. right 1.68; p = 0.017). When rectal cancers were separated from left-sided colon cancers, PTEN mRNA levels increased progressively from rectum to right-sided colon (median; rectum 0.84, left colon 1.23, right colon 1.68, p = 0.013). PTEN mRNA expression in liver metastases also differed significantly according to primary tumor location (median; left 0.92 vs. right 1.27, p = 0.048). There was no difference in overall survival between patients with high versus low levels of PTEN mRNA (p = 0.59).

CONCLUSIONS

Our data suggest that the PIK3/AKT/mTOR pathway is more active in left- than right-sided CRC, which provides a possible explanation for the fact that efficacy of anti-EGFR therapy differs by location of primary tumor.

Roles of oxidative stress and the ERK1/2, PTEN and p70S6K signaling pathways in arsenite-induced autophagy

Studies show that arsenite induces oxidative stress and modifies cellular function via phosphorylation of proteins and inhibition of DNA repair enzymes. Autophagy, which has multiple physiological and pathological roles in cellular function, is initiated by oxidative stress and is regulated by the signaling pathways of phosphatidylinositol 3-phosphate kinase (PI3K)/mammalian target of rapamycin (mTOR)/p70S6 kinase (p70S6K) and extracellular signaling-regulated protein kinase 1/2 (ERK1/2) that play important roles in oncogenesis. However, the effects of arsenite-induced oxidative stress on autophagy and on expression of related proteins are not fully understood. This study found that cells treated with sodium arsenite had reduced 8-oxoguanine DNA glycosylase 1 (OGG1) and increased 8-hydroxy-2'-deoxyguanosine (8-OHdG) and activating transcription factor (ATF) 3 in SV-40 immortalized human uroepithelial (SV-HUC-1) cells. Arsenite also increased the number of autophagosomes and increased levels of the autophagy markers Beclin-1 and microtubule-associated protein 1 light chain 3B. Reactive oxygen species scavenger decreased arsenite-induced autophagy in SV-HUC-1 cells. Our previous work showed that arsenite induced phosphorylation of the ERK1/2 signaling pathway. The current study further showed that arsenite decreased phosphatase and tensin homologue (PTEN) levels and increased phospho-p70S6 kinase (p-p70S6K) in SV-HUC-1 cells. However, both kinase inhibitor U0126 and the DNA (cytosine-5-)-methyltransferase 1 (DNMT1) inhibitor 5-aza-deoxycytidine abolished the effect of arsenite on expressions of PTEN and p-p70S6K. These results show that autophagy induced by arsenite exposure is mediated by oxidative stress, which regulates activation of the PTEN, p70S6K and ERK1/2 signaling pathways. Thus, this study clarifies the role of autophagy in arsenite-induced urothelial carcinogenesis.

Effects of PTEN gene alteration in patients with gallbladder cancer

Gallbladder cancer (GBC) is an aggressive malignancy usually diagnosed in an advanced stage. We investigated the effects of alterations of the phosphatase and tensin homologue (PTEN) gene on the occurrence and development of GBC, which has not been previously reported. A total 141 cases of GBC were analyzed for mutation, expression, and methylation across the nine exons of the PTEN gene. DNA sequencing methods were applied for mutation detection, whereas protein expression and methylation status were evaluated by immunohistochemical and methylation-specific PCR analysis, respectively. Novel PTEN mutations were observed in 6.3% of cases (9/141), and they included two silent mutations. In mutant cases, according to changes in codons, the respective amino acid sequences were also changed, which caused of proteins. A high percentage (72%) of loss of protein expression was observed more often in cases than in control samples. Interestingly, all nine cases with mutations showed loss of PTEN expression, whereas four of these nine cases showed positive promoter methylation. Hypermethylation was significantly more common in older patients than in younger ones (P<0.02). These findings suggest that PTEN mutations and inactivation may play an important role in the development and progression of gallbladder carcinoma.

Molecular mechanisms of apoptosis and cell selectivity of zinc dithiocarbamates functionalized with hydroxyethyl substituents

In the solid state each of three binuclear zinc dithiocarbamates bearing hydroxyethyl groups, {Zn[S2CN(R)CH2CH2OH]2}2 for R = iPr (1), CH2CH2OH (2), and Me (3), and an all alkyl species, [Zn(S2CNEt2)2]2 (4), features a centrosymmetric {ZnSCS}2 core with a step topology; both 1 and 3 were isolated as monohydrates. All compounds were broadly cytotoxic, specifically against human cancer cell lines compared with normal cells, with greater potency than cisplatin. Notably, some selectivity were indicated with 2 being the most potent against human ovarian carcinoma cells (cisA2780), and 4 being more cytotoxic toward multidrug resistant human breast carcinoma cells (MCF-7R), human colon adenocarcinoma cells (HT-29), and human lung adenocarcinoma epithelial cells (A549). Based on human apoptosis PCR-array analysis, caspase activities, DNA fragmentation, cell apoptotic assays, intracellular reactive oxygen species (ROS) measurements and human topoisomerase I inhibition, induction of apoptosis in HT-29 cells is demonstrated via both extrinsic and intrinsic pathways. Compounds 2-4 activate the p53 gene while 1 activates both p53 and p73. Cell cycle arrest at the S and G2/M phases correlates with inhibition of HT-29 cell growth. Cell invasion is also inhibited by 1-4 which is correlated with down-regulation of NF-κB.

Roles of PTEN (Phosphatase and Tensin Homolog) in gastric cancer development and progression

Gastric cancer is highly invasive, aggressively malignant, and amongst the most prevalent of all forms of cancer. Despite improved management strategies, early stage diagnosis of gastric cancer and accurate prognostic assessment is still lacking. Several recent reports have indicated that the pathogenesis of gastric cancer involves complex molecular mechanisms and multiple genetic and epigenetic alterations in oncogenes and tumor suppressor genes. Functional inactivation of the tumor suppressor protein PTEN (Phosphatase and Tensin Homolog) has been detected in multiple cases of gastric cancer, and already shown to be closely linked to the development, progression and prognosis of the disease. Inactivation of PTEN can be attributed to gene mutation, loss of heterozygosity, promoter hypermethylation, microRNA- mediated regulation of gene expression, and post-translational phosphorylation. PTEN is also involved in mechanisms regulating tumor resistance to chemotherapy. This review provides a comprehensive analysis of PTEN and its roles in gastric cancer, and emphasizes its potential benefits in early diagnosis and gene therapy-based treatment strategies.

PTEN knockdown alters dendritic spine/protrusion morphology, not density

Mutations in phosphatase and tensin homolog deleted on chromosome 10 (PTEN) are implicated in neuropsychiatric disorders including autism. Previous studies report that PTEN knockdown in neurons in vivo leads to increased spine density and synaptic activity. To better characterize synaptic changes in neurons lacking PTEN, we examined the effects of shRNA knockdown of PTEN in basolateral amygdala neurons on synaptic spine density and morphology by using fluorescent dye confocal imaging. Contrary to previous studies in the dentate gyrus, we find that knockdown of PTEN in basolateral amygdala leads to a significant decrease in total spine density in distal dendrites. Curiously, this decreased spine density is associated with increased miniature excitatory postsynaptic current frequency and amplitude, suggesting an increase in number and function of mature spines. These seemingly contradictory findings were reconciled by spine morphology analysis demonstrating increased mushroom spine density and size with correspondingly decreased thin protrusion density at more distal segments. The same analysis of PTEN conditional deletion in the dentate gyrus demonstrated that loss of PTEN does not significantly alter total density of dendritic protrusions in the dentate gyrus, but does decrease thin protrusion density and increases density of more mature mushroom spines. These findings suggest that, contrary to previous reports, PTEN knockdown may not induce de novo spinogenesis, but instead may increase synaptic activity by inducing morphological and functional maturation of spines. Furthermore, behavioral analysis of basolateral amygdala PTEN knockdown suggests that these changes limited only to the basolateral amygdala complex may not be sufficient to induce increased anxiety-related behaviors.

Recent advances in the molecular characterization of circulating tumor cells

Although circulating tumor cells (CTCs) were first observed over a century ago, lack of sensitive methodology precluded detailed study of these cells until recently. However, technological advances have now facilitated the identification, enumeration, and characterization of CTCs using a variety of methods. The majority of evidence supporting the use of CTCs in clinical decision-making has been related to enumeration using the CellSearch® system and correlation with prognosis. Growing evidence also suggests that CTC monitoring can provide an early indication of patient treatment response based on comparison of CTC levels before and after therapy. However, perhaps the greatest potential that CTCs hold for oncology lies at the level of molecular characterization. Clinical treatment decisions may be more effective if they are based on molecular characteristics of metastatic cells rather than on those of the primary tumor alone. Molecular characterization of CTCs (which can be repeatedly isolated in a minimally invasive fashion) provides the opportunity for a "real-time liquid biopsy" that allows assessment of genetic drift, investigation of molecular disease evolution, and identification of actionable genomic characteristics. This review focuses on recent advances in this area, including approaches involving immunophenotyping, fluorescence in situ hybridization (FISH), multiplex RT-PCR, microarray, and genomic sequencing.

Curcumin up-regulates phosphatase and tensin homologue deleted on chromosome 10 through microRNA-mediated control of DNA methylation--a novel mechanism suppressing liver fibrosis

Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) has been reported to play a role in the suppression of activated hepatic stellate cells (HSCs). Moreover, it has been demonstrated that hypermethylation of the PTEN promoter is responsible for the loss of PTEN expression during HSC activation. Methylation is now established as a fundamental regulator of gene transcription. MicroRNAs (miRNAs), which can control gene expression by binding to their target genes for degradation and/or translational repression, were found to be involved in liver fibrosis. However, the mechanism responsible for miRNA-mediated epigenetic regulation in liver fibrosis still remained unclear. In the present study, curcumin treatment significantly resulted in the inhibition of cell proliferation and an increase in the apoptosis rate through the up-regulation of PTEN associated with a decreased DNA methylation level. Only DNA methyltransferase 3b (DNMT3b) was reduced in vivo and in vitro after curcumin treatment. Further studies were performed aiming to confirm that the knockdown of DNMT3b enhanced the loss of PTEN methylation by curcumin. In addition, miR-29b was involved in the hypomethylation of PTEN by curcumin. MiR-29b not only was increased by curcumin in activated HSCs, but also was confirmed to target DNMT3b by luciferase activity assays. Curcumin-mediated PTEN up-regulation, DNMT3b down-regulation and PTEN hypomethylation were all attenuated by miR-29b inhibitor. Collectively, it is demonstrated that curcumin can up-regulate miR-29b expression, resulting in DNMT3b down-regulation in HSCs and epigenetically-regulated PTEN involved in the suppression of activated HSCs. These results indicate that miRNA-mediated epigenetic regulation may be a novel mechanism suppressing liver fibrosis.

Novel dual-color immunohistochemical methods for detecting ERG-PTEN and ERG-SPINK1 status in prostate carcinoma

Identification of new molecular markers has led to the molecular classification of prostate cancer based on driving genetic lesions. The translation of these discoveries for clinical use necessitates the development of simple, reliable and rapid detection systems to screen patients for specific molecular aberrations. We developed two dual-color immunohistochemistry-based assays for the simultaneous assessment of ERG-PTEN and ERG-SPINK1 in prostate cancer. A total of 232 cases from 184 localized and 48 metastatic prostate cancers were evaluated for ERG-PTEN and 284 cases from 228 localized and 56 metastatic prostate cancers were evaluated for ERG-SPINK1. Of the 232 cases evaluated for ERG-PTEN, 81 (35%) ERG-positive and 77 (33%) PTEN-deleted cases were identified. Of the 81 ERG-positive cases, PTEN loss was confirmed in 35 (15%) cases by fluorescence in situ hybridization (FISH). PTEN status was concordant in 203 cases (sensitivity 90% and specificity 87%; P<0.0001) by both immunohistochemisty and FISH; however, immunohistochemisty could not distinguish between heterozygous and homozygous deletion status of PTEN. Of the 284 cases evaluated for ERG-SPINK1, 111 (39%) cases were positive for ERG. In the remaining 173 ERG-negative cases, SPINK1 was positive in 26 (9%) cases. SPINK1 expression was found to be mutually exclusive with ERG expression; however, we identified two cases, of which one showed concomitant expression of ERG and SPINK1 in the same tumor foci, and in the second case ERG and SPINK1 were seen in two independent foci of the same tumor nodule. Unlike the homogenous ERG staining in cancer tissues, heterogeneous SPINK1 staining was observed in the majority of the cases. Further studies are required to understand the molecular heterogeneity of cases with concomitant ERG-SPINK1 expression. Automated dual ERG-PTEN and ERG-SPINK1 immunohistochemisty assays are simple, reliable and portable across study sites for the simultaneous assessment of these proteins in prostate cancer.

New advances of DNA methylation in liver fibrosis, with special emphasis on the crosstalk between microRNAs and DNA methylation machinery

Epigenetics refers to the study of heritable changes in the pattern of gene expression that is controlled by a mechanism specifically not due to changes the primary DNA sequence. Well-known epigenetic mechanisms include DNA methylation, post-translational histone modifications and RNA-based mechanisms including those controlled by small non-coding RNAs (miRNAs). Recent studies have shown that epigenetic modifications orchestrate the hepatic stellate cell (HSC) activation and liver fibrosis. In this review we focus on the aberrant methylation of CpG island promoters of select genes is the prominent epigenetic mechanism to effectively silence gene transcription facilitating HSC activation and liver fibrosis. Furthermore, we also discuss epigenetic dysregulation of tumor-suppressor miRNA genes by promoter DNA methylation and the interaction of DNA methylation with miRNAs involved in the regulation of HSC activation and liver fibrosis. Recent advances in epigenetics alterations in the pathogenesis of liver fibrosis and their possible use as new therapeutic targets and biomarkers.

Loss and reduced expression of PTEN correlate with advanced-stage gastric carcinoma

Phosphatase and tensin homolog (PTEN) is a tumor suppressor involved in multiple cell processes. To investigate the role of PTEN in the development of gastric carcinoma, we determined the expression pattern of PTEN in primary gastric carcinoma and in paired adjacent non-neoplastic tissue. We also determined the correlation of PTEN expression with clinicopathological characteristics and patient survival. Overall, 159 gastric carcinomas and 151 paired adjacent non-neoplastic tissues were used in the present study. PTEN expression was determined using tissue microarrays and immunohistochemistry. The clinical sensitivity and specificity of PTEN expression were calculated using receiver operator characteristic curves. Results showed that the loss of cytoplasmic PTEN was significantly more frequent in carcinoma tissue compared with adjacent non-neoplastic tissue (62 vs. 5%, respectively; P<0.0001). PTEN expression was markedly downregulated in carcinoma tissues compared with adjacent non-neoplastic tissues. The loss of cytoplasmic PTEN expression was positively correlated with histological stage (P=0.016). The loss of nuclear or total PTEN, and downregulation of total PTEN expression, was significantly different between American Joint Committee on Cancer tumors of stage I and stages II-IV. A low cytoplasmic or total PTEN expression showed high clinical sensitivity and specificity for gastric carcinoma. However, PTEN expression was not significantly associated with overall or 3-year survival rates. The findings of the present study indicated that PTEN expression may be a molecular diagnostic marker for gastric cancer. Thus, the loss or reduced expression of PTEN potentially correlate with advanced stages of gastric carcinoma.

PTEN, a widely known negative regulator of insulin/PI3K signaling, positively regulates neuronal insulin resistance

Lipid and protein tyrosine phosphatase, phosphatase and tension homologue (PTEN), is a widely known negative regulator of insulin/phosphoinositide 3-kinase signaling. Down-regulation of PTEN is thus widely documented to ameliorate insulin resistance in peripheral tissues such as skeletal muscle and adipose. However, not much is known about its exact role in neuronal insulin signaling and insulin resistance. Moreover, alterations of PTEN in neuronal systems have led to discovery of several unexpected outcomes, including in the neurodegenerative disorder Alzheimer's disease (AD), which is increasingly being recognized as a brain-specific form of diabetes. In addition, contrary to expectations, its neuron-specific deletion in mice resulted in development of diet-sensitive obesity. The present study shows that PTEN, paradoxically, positively regulates neuronal insulin signaling and glucose uptake. Its down-regulation exacerbates neuronal insulin resistance. The positive role of PTEN in neuronal insulin signaling is likely due to its protein phosphatase actions, which prevents the activation of focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK), the kinases critically involved in neuronal energy impairment and neurodegeneration. Results suggest that PTEN acting through FAK, the direct protein substrate of PTEN, prevents ERK activation. Our findings provide an explanation for unexpected outcomes reported earlier with PTEN alterations in neuronal systems and also suggest a novel molecular pathway linking neuronal insulin resistance and AD, the two pathophysiological states demonstrated to be closely linked.

DNMT1-mediated PTEN hypermethylation confers hepatic stellate cell activation and liver fibrogenesis in rats

Hepatic stellate cell (HSC) activation is an essential event during liver fibrogenesis. Phosphatase and tension homolog deleted on chromosome 10 (PTEN), a tumor suppressor, is a negative regulator of this process. PTEN promoter hypermethylation is a major epigenetic silencing mechanism in tumors. The present study aimed to investigate whether PTEN promoter methylation was involved in HSC activation and liver fibrosis. Treatment of activated HSCs with the DNA methylation inhibitor 5-aza-2'-deoxycytidine (5-azadC) decreased aberrant hypermethylation of the PTEN gene promoter and prevented the loss of PTEN expression that occurred during HSC activation. Silencing DNA methyltransferase 1 (DNMT1) gene also decreased the PTEN gene promoter methylation and upregulated the PTEN gene expression in activated HSC-T6 cells. In addition, knockdown of DNMT1 inhibited the activation of both ERK and AKT pathways in HSC-T6 cells. These results suggest that DNMT1-mediated PTEN hypermethylation caused the loss of PTEN expression, followed by the activation of the PI3K/AKT and ERK pathways, resulting in HSC activation.

Molecular changes in mesothelioma with an impact on prognosis and treatment

CONTEXT

In recent decades, research on malignant pleural mesothelioma (MPM) has been developed to improve patients' outcomes by increasing the level of confidence in MPM diagnosis and prognosis.

OBJECTIVE

To summarize data on genetic and epigenetic abnormalities in MPM that may be of interest for a better management of patients with MPM.

DATA SOURCES

Data were obtained from scientific publications on genetic and epigenetic abnormalities in MPM by studying gene mutations, DNA methylation, and gene and microRNA expression profiling.

CONCLUSIONS

Molecular changes in MPM consist in altered expression and in activation or inactivation of critical genes in oncogenesis, especially tumor suppressor genes at the INK4 and NF2 loci. Activation of membrane receptor tyrosine kinases and deregulation of signaling pathways related to differentiation, survival, proliferation, apoptosis, cell cycle control, metabolism, migration, and invasion have been demonstrated. Alterations that could be targeted at a global level (methylation) have been recently reported. Experimental research has succeeded especially in abolishing proliferation and triggering apoptosis in MPM cells. So far, targeted clinical approaches focusing on receptor tyrosine kinases have had limited success. Molecular analyses of series of MPM cases have shown that defined alterations are present in MPM subsets, consistent with interindividual variations of molecular alterations, and suggesting that identification of patient subgroups will be essential to develop more specific therapies.

Comparative effects of retinoic acid, vitamin D and resveratrol alone and in combination with adenosine analogues on methylation and expression of phosphatase and tensin homologue tumour suppressor gene in breast cancer cells

Aberrations in DNA methylation patterns have been reported to be involved in driving changes in the expression of numerous genes during carcinogenesis and have become promising targets for chemopreventive action of natural compounds. In the present study, we investigated the effects of all-trans retinoic acid (ATRA), vitamin D₃ and resveratrol alone and in combination with adenosine analogues, 2-chloro-2'-deoxyadenosine (2CdA) and 9-β-d-arabinosyl-2-fluoroadenine (F-ara-A), on the methylation and expression of phosphatase and tensin homologue (PTEN) tumour suppressor gene in MCF-7 and MDA-MB-231 breast cancer cells. The present results showed that in non-invasive MCF-7 cells, ATRA, vitamin D₃ and resveratrol possess high efficacy in the reduction of PTEN promoter methylation. It was associated with PTEN induction as well as DNA methyltransferase down-regulation and p21 up-regulation after treatments with vitamin D₃ and resveratrol, suggesting a complex regulation of the DNA methylation machinery. Vitamin D₃ and resveratrol improved the inhibitory effects of 2CdA and F-ara-A on PTEN methylation in MCF-7 cells; however, only the combined action of vitamin D₃ and 2CdA boosted the induction of PTEN expression, suggesting a cooperation of these compounds in additional processes driving changes in PTEN expression. In contrast, in highly invasive MDA-MB-231 cells, only vitamin D₃ reduced PTEN methylation and induced its expression without notable effects in combined treatments. The present results suggest that natural compounds can find application in epigenetic anticancer therapy aimed at inhibition of promoter methylation of tumour suppressor genes and induction of their expression at early stages of carcinogenesis.

CpG-island methylation study of liver fluke-related cholangiocarcinoma

BACKGROUND

Genetic changes have been widely reported in association with cholangiocarcinoma (CCA), while epigenetic changes are poorly characterised. We aimed to further evaluate CpG-island hypermethylation in CCA at candidate loci, which may have potential as diagnostic or prognostic biomarkers.

METHODS

We analysed methylation of 26 CpG-islands in 102 liver fluke related-CCA and 29 adjacent normal samples using methylation-specific PCR (MSP). Methylation of interest loci was confirmed using pyrosequencing and/or combined bisulfite restriction analysis, and protein expression by immunohistochemistry.

RESULTS

A number of CpG-islands (OPCML, SFRP1, HIC1, PTEN and DcR1) showed frequency of hypermethylation in >28% of CCA, but not adjacent normal tissues. The results showed that 91% of CCA were methylated in at least one CpG-island. The OPCML was the most frequently methylated locus (72.5%) and was more frequently methylated in less differentiated CCA. Patients with methylated DcR1 had significantly longer overall survival (Median; 41.7 vs 21.7 weeks, P=0.027). Low-protein expression was found in >70% of CCA with methylation of OPCML or DcR1.

CONCLUSION

Aberrant hypermethylation of certain loci is a common event in liver fluke-related CCA and may potentially contribute to cholangiocarcinogenesis. The OPCML and DcR1 might serve as methylation biomarkers in CCA that can be readily examined by MSP.

Ptenb mediates gastrulation cell movements via Cdc42/AKT1 in zebrafish

Phosphatidylinositol 3-kinase (PI3 kinase) mediates gastrulation cell migration in zebrafish via its regulation of PIP₂/PIP₃ balance. Although PI3 kinase counter enzyme PTEN has also been reported to be essential for gastrulation, its role in zebrafish gastrulation has been controversial due to the lack of gastrulation defects in pten-null mutants. To clarify this issue, we knocked down a pten isoform, ptenb by using anti-sense morpholino oligos (MOs) in zebrafish embryos and found that ptenb MOs inhibit convergent extension by affecting cell motility and protrusion during gastrulation. The ptenb MO-induced convergence defect could be rescued by a PI3-kinase inhibitor, LY294002 and by overexpressing dominant negative Cdc42. Overexpression of human constitutively active akt1 showed similar convergent extension defects in zebrafish embryos. We also observed a clear enhancement of actin polymerization in ptenb morphants under cofocal microscopy and in actin polymerization assay. These results suggest that Ptenb by antagonizing PI3 kinase and its downstream Akt1 and Cdc42 to regulate actin polymerization that is critical for proper cell motility and migration control during gastrulation in zebrafish.

Curtailing the High Rate of Late-Stage Attrition of Investigational Therapeutics Against Unprecedented Targets in Patients with Lung and Other Malignancies: Fig. 1

A greater understanding of the pathogenesis and biology of cancer coupled with major advances in biotechnology has resulted in the identification of rationally designed, target-based (RDTB) anticancer therapeutics, ushering in new therapeutic opportunities and high expectations for the future as well as developmental challenges. Because these agents appear to principally target malignant cells, it is expected that they will produce less toxicity at clinically effective doses than nonspecific cytotoxic agents, but their target requirements are likely to be much more stringent. The innate complexity of the networks that contain elements targeted by these agents also decreases the probability that any single therapeutic manipulation will result in robust clinical activity and success when used alone, particularly in patients with solid malignancies that have multiple relevant signaling aberrations. In contrast, proof of principle and robust antitumor activity may be most efficiently demonstrated in nonrandomized evaluations involving tumors that are principally driven by aberrations of the specific target. The predominant therapeutic manifestation of RDTB agents in preclinical studies is due to decreased tumor growth rates and will likely be similar in the clinic; however, such manifestations are not readily detectable and quantifiable using nonrandomized clinical evaluations. To curtail the increasing rate of late-stage attrition of RDTB agents, which, if maintained, will stymie progress in cancer therapy, the design of initial nonrandomized evaluations, particularly the selection of tumors and patients, must be guided by the principal biological features of the agents. Next, evaluations, some of which must be randomized, can be performed in a wide range of tumor types, depending on the presence and relevance of the target. To validate the concept of RDTB therapeutics and to realize their full potential, radically different development, evaluation, and regulatory paradigms must be adopted.

Sphingosine-1-phosphate protects intestinal epithelial cells from apoptosis through the Akt signaling pathway

OBJECTIVE

The regulation of apoptosis of intestinal mucosal cells is important in maintenance of normal intestinal physiology.

SUMMARY

Sphingosine-1-phosphate (S1P) has been shown to play a critical role in cellular protection to otherwise lethal stimuli in several nonintestinal tissues.

METHODS

The current study determines whether S1P protected normal intestinal epithelial cells (IECs) from apoptosis and whether Akt activation was the central pathway for this effect.

RESULTS

S1P demonstrated significantly reduced levels of apoptosis induced by tumor necrosis factor-alpha (TNF-alpha)/cycloheximide (CHX). S1P induced increased levels of phosphorylated Akt and increased Akt activity, but did not affect total amounts of Akt. This activation of Akt was associated with decreased levels of both caspase-3 protein levels and of caspase-3 activity. Inactivation of Akt by treatment with the PI3K chemical inhibitor LY294002 or by overexpression of the dominant negative mutant of Akt (DNMAkt) prevented the protective effect of S1P on apoptosis. Additionally, silencing of the S1P-1 receptor by specific siRNA demonstrated a lesser decrease in apoptosis to S1P exposure.

CONCLUSION

These results indicate that S1P protects intestinal epithelial cells from apoptosis via an Akt-dependent pathway.

Involvement of PTEN promoter methylation in cerebral cavernous malformations

BACKGROUND AND PURPOSE

Cerebral cavernous malformations (CCMs) are prevalent cerebral vascular lesions involving aberrant angiogenesis. However, the underlying mechanism is poorly understood. Phosphatase and tension homolog deleted on chromosome 10 (PTEN), a tumor suppressor, is frequently deficient in various pathologies due to mutation or epigenetic alterations. PTEN promoter hypermethylation is a major epigenetic silencing mechanism leading to activation of angiogenesis in tumors. The present study aimed to investigate whether PTEN promoter methylation was involved in CCMs.

METHODS

PTEN promoter methylation was detected in surgical specimens of CCMs (n=69) by methylation-specific polymerase chain reaction. The methylation status was correlated to the clinical manifestations and to PTEN expression, which was analyzed by both Western blot and immunohistochemistry. To investigate the endothelial proliferation and the potential signaling pathways affected by PTEN methylation, proliferating cell nuclear antigen as well as phosphor-Akt and phosphor-Erk1,2 were detected by immunofluorescence and Western blot, respectively, in CCM specimens.

RESULTS

Methylation-specific polymerase chain reaction revealed PTEN promoter methylation in 15.9% CCMs. Strikingly, 5 of 6 familial CCMs showed PTEN promoter methylation (83.3%), which was significantly higher than in sporadic cases (9.4%; P<0.001). In addition, PTEN promoter methylation appeared more frequently in multiple CCMs, including familial cases (46.7%), than that in single-lesioned CCMs (11.8%; P<0.05). Immunostaining and Western blot revealed a more significant PTEN downregulation in PTEN-methylated CCMs in comparison to PTEN-unmethylated CCMs. Reduced PTEN expression was inversely correlated to the expression of proliferating cell nuclear antigen and to the activation of Erk1,2, but not of Akt.

CONCLUSIONS

We reported here for the first time the involvement of PTEN promoter methylation in CCMs, particularly in familial CCMs, suggesting this epigenetic alteration as a potential pathomechanism of CCMs. The identification of Erk1,2 as triggered signaling in the lesions may be valuable for the development of effective therapy for this disease.

The mechanism of action of the tumour suppressor gene PTEN

Intracellular levels of phosphorylation are regulated by the coordinated action of protein kinases and phosphatases. Disregulation of this balance can lead to cellular transformation. Here we review knowledge of the mechanisms of one protein phosphatase, the tumour suppressor PTEN/MMAC/TEP 1 apropos its role in tumorigenesis and signal transduction. PTEN plays an important role in the phosphatidyl-inositol-3-kinase (PI3-K) pathway by catalyzing degradation of phosphatidylinositol-(3,4,5)-triphosphate generated by PI3-K. This inhibits downstream targets mainly protein kinase B (PKB/Akt), cell survival and proliferation. PTEN contributes to cell cycle regulation by blockade of cells entering the S phase of the cell cycle, and by upregulation of p27(Kip1) which is recruited into the cyclin E/cdk2 complex. PTEN also modulates cell migration and motility by regulation of the extracellular signal-related kinase - mitogen activated protein kinase (ERK-MAPK) pathway and by dephosphorylation of focal adhesion kinase (FAK). We also emphasize the increasingly important role that PTEN has from an evolutionary point of view. A number of PTEN functions have been elucidated but more information is needed for utilization in clinical application and potential cancer therapy.

Absence of TMPRSS2:ERG fusions and PTEN losses in prostate cancer is associated with a favorable outcome

TMPRSS2:ERG gene fusions and PTEN deletions are the most common genomic aberrations in prostate cancer. Recent work has suggested that the TMPRSS2:ERG fusion is associated with a more aggressive phenotype. Similarly, PTEN deletion has been associated with biochemical recurrence and lymph node metastasis. To date, there has been no systematic analysis of the combined influence of genomic PTEN deletion with TMPRSS2:ERG gene fusions on clinical parameters of prostate cancer progression. We carried out a retrospective analysis of 125 prostate cancers with known clinical outcome using interphase fluorescence in situ hybridization to detect the relative prevalence of TMPRSS2:ERG rearrangements and/or PTEN genomic deletions. TMPRSS2:ERG rearrangement was found in 60 of 125 (48%) prostate cancers. Duplication of TMPRSS2:ERG fusion was observed in seven (6%) tumors. Gleason grade (P=0.0002)/score (P=0.001), median tumor volume (P=0.0024), preoperative PSA (P=0.001) and perineural invasion (P=0.0304) were significantly associated with biochemical recurrence by univariate analysis with TMPRSS2:ERG approaching significance (P=0.0523). By multivariate analysis, relevant factors associated with recurrence were Gleason scores 7 (P=0.001) and 8-10 (P=0.015), PTEN homozygous deletion (P=0.013) and concurrent TMPRSS2:ERG fusion and PTEN deletion (P=0.036). Kaplan-Meier analysis indicated that the presence of TMPRSS2:ERG fusion was marginally less favorable in comparison to no fusion. Duplication of fusion gene showed worse prognosis. It was possible to determine the relative frequencies of PTEN deletion and/or TMPRSS2:ERG fusions in 82 of 125 prostate cancers. With biochemical recurrence as an endpoint, the genomic biomarkers identified three patient groups: (1) 'poor genomic grade' characterized by both PTEN deletion and TMPRSS2:ERG fusions (23/82, 28%); (2) 'intermediate genomic grade' with either PTEN deletion or TMPRSS2:ERG fusion (35/82, 43%) and (3) 'favorable genomic grade' in which neither rearrangement was present (24/82, 29%). Kaplan-Meier and multivariate analysis indicate that TMPRSS2:ERG fusion and PTEN loss together are a predictor of earlier biochemical recurrence of disease.

The role of mTOR in the management of solid tumors: an overview

Mammalian target of rapamycin (mTOR) is a key protein kinase controlling signal transduction from various growth factors and upstream proteins to the level of mRNA and ribosome with a regulatory effect on cell cycle progression, cellular proliferation and growth. TOR genes were discovered rather serendipitously while investigating the cause of resistance to immunosuppressant rapamycin in yeast. In normal cells, mTOR controls brilliantly the load of signals from its effectors resulting in a normal cell function. On the contrary, in various diseases and mainly in cancer this balance is lost due to mutations or overactivation of upstream pathways leading to a persistent proliferation and tumor growth. What makes mTOR attractive to researchers seems to be its key position which is on the crossroad of various signal pathways (Ras, PI3K/Akt, TSC, NF-kappaB) towards mRNA, ribosome, protein synthesis and translation of significant molecules, the uncontrolled production of which may lead to tumor proliferation and growth. Inhibition of mTOR by rapamycin (a natural product) or its analogs aims to prevent the deleterious effects of the abnormal signaling, regardless at which point of the signal pathway has the abnormality launched. Here, we will review the physiological functions of mTOR, its association to carcinogenesis and the latest evidence regarding the use of mTOR inhibitors in cancer treatment as well as future trends and aims of research.

RhoC promotes metastasis via activation of the Pyk2 pathway in prostate cancer

RhoC is a member of the Ras-homologous family of genes which have been implicated in tumorigenesis and tumor progression. However, the exact role of RhoC is controversial and is yet to be clarified. We have examined the effect of RhoC on prostate tumor cells and found that RhoC had no effect on cell proliferation in vitro or on tumor growth in mice. However, RhoC significantly enhanced the metastatic ability of the tumor cells in these animals, suggesting that RhoC affects only the metastasis but not the growth of prostate tumor cells. The results of our immunohistochemical analyses on tumor specimens from 63 patients with prostate cancer indicate that RhoC expression had no significant correlation with Gleason grade. However, the expression of RhoC showed significant positive correlation with both lymph node and distant metastasis, and it was inversely correlated with patient survival. We also found that RhoC significantly augmented the invasion and motility of prostate tumor cells by activating matrix metalloproteinases 2 and 9 (MMP2 and MMP9) in vitro. The results of our antibody array analysis for signal molecules revealed that RhoC significantly activated kinases including mitogen-activated protein kinase (MAPK), focal adhesion kinase (FAK), Akt, and Pyk2. Inhibition of Pyk2 kinase blocked the RhoC-dependent activation of FAK, MAPK, and Akt, followed by the suppression of MMP2 and MMP9. Inhibitors of both MAPK and Akt also significantly blocked the activities of these MMPs. Therefore, our results indicate that RhoC promotes tumor metastasis in prostate cancer by sequential activation of Pyk2, FAK, MAPK, and Akt followed by the up-regulation of MMP2 and MMP9, which results in the stimulation of invasiveness of tumor cells.

Targeting AMPK: a new therapeutic opportunity in breast cancer

BACKGROUND

This paper reviews the mammalian Target Of Rapamycin (mTOR) pathway dysregulation in breast cancer, and the current evidence targeting this pathway directly or through activation of AMP-activated protein kinase (AMPK) as an additional therapeutic opportunity for intervention in breast cancer.

METHODS

Relevant articles were identified through computerised searches of Medline and Pubmed. Secondary articles were identified from the reference lists of key papers and by hand searching.

RESULTS AND CONCLUSION

The current consensus to target the AMPK/mTOR pathway in breast cancer is based on in vitro and epidemiological evidences. A low incidence of cancer in diabetic patients on metformin has been explained in vitro by the drug's anti-proliferative effect through activation of AMPK. There is a need to explore the anticancer effects of metformin and the potential to develop the therapeutic avenues offered by targeting the AMPK/mTOR pathway.

Effects and mechanisms of silibinin on human hepatoma cell lines

AIM

To investigate in vitro effects and mechanisms of silibinin on hepatocellular carcinoma (HCC) cell growth.

METHODS

Human HCC cell lines were treated with different doses of silibinin. The effects of silibinin on HCC cell growth and proliferation, apoptosis, cell cycle progression, histone acetylation, and other related signal transductions were systematically examined.

RESULTS

We demonstrated that silibinin significantly reduced the growth of HuH7, HepG2, Hep3B, and PLC/PRF/5 human hepatoma cells. Silibinin-reduced HuH7 cell growth was associated with significantly up-regulated p21/CDK4 and p27/CDK4 complexes, down-regulated Rb-phosphorylation and E2F1/DP1 complex. Silibinin promoted apoptosis of HuH7 cells that was associated with down-regulated survivin and up-regulated activated caspase-3 and -9. Silibinin's anti-angiogenic effects were indicated by down-regulated metalloproteinase-2 (MMP2) and CD34. We found that silibinin-reduced growth of HuH7 cells was associated with increased activity of phosphatase and tensin homolog deleted on chromosome ten (PTEN) and decreased p-Akt production, indicating the role of PTEN/PI(3)K/Akt pathway in silibinin-mediated anti-HCC effects. We also demonstrated that silibinin increased acetylation of histone H3 and H4 (AC-H3 and AC-H4), indicating a possible role of altered histone acetylation in silibinin-reduced HCC cell proliferation.

CONCLUSION

Our results defined silibinin's in vitro anti-HCC effects and possible mechanisms, and provided a rationale to further test silibinin for HCC chemoprevention.

Expression and significance of hypoxia-inducible factor-1α and its regulator phosphatase and tensin homolog deleted in chromosome 10 in gastric cancer

AIM: To study the expression of hypoxia-inducible factor-1α (HIF-1α) and its regulator phosphatase and tensin homolog deleted in chromosome 10 (PTEN) in gastric cancer and their relationship with tumor angiogenesis and clinicopathologic features.

METHODS: Immunohistochemistry was performed to detect the expression of HIF-1α and its regulator PTEN in 54 cases of gastric cancer. The relationships among the expression of HIF-1α and PTEN, tumor angiogenesis and clinicopathologic features of patients were analyzed.

RESULTS: The positive expression rate of HIF-1α in gastric cancer (74.07%) was significantly higher than that in normal gastric tissue (0%, P < 0.01); the expression of HIF-1α in gastric cancer was significantly associated with TNM stage (P < 0.05), invasive depth (P < 0.01) and lymph-node metastasis (P < 0.05); the positive expression rate of PTEN in gastric cancers was low (51.9%), and reduced with increased invasive depth (38.5% vs 86.7%, P < 0.01) and clinical stage (28.6% vs 76.9%, P < 0.01), reduced histological differentiation (22.2% vs 70.6%, 63.2%, P < 0.01) and the occurrence of lymphatic (28.0% vs 72.4%, P < 0.01) and long distance metastases (16.7% vs 61.9%, P < 0.05). There was a negative correlation between the expression of HIF-1α and PTEN (r = -0.41, P < 0.05).

CONCLUSION: HIF-1α and its regulator PTEN play a very important role in the development of gastric cancer and could be useful factors in the diagnosis of gastric cancer and estimation of prognosis.

Cytotoxicity of honeybee (Apis mellifera) venom in normal human lymphocytes and HL-60 cells

Whole bee venom (BV) is used to treat inflammatory diseases in Korean traditional medicine. Various studies have demonstrated anti-inflammatory and anticancer effects of BV. The toxicity of individual components of BV has been widely studied, although few studies have reported on the toxicity of BV. We sought to evaluate the cytotoxicity of BV in normal human lymphocytes and HL-60 cells. When cells were treated with BV at concentrations of 1 or 5 microg/ml, BV induced cell death in a time-dependent manner until 24 h, but these cytotoxic effects ended thereafter. When cells were treated with BV at a concentration of 10 microg/ml, however, viability decreased until 72 h, which may have been due to the half-life of BV. Whole BV also inhibited proliferation in these cells. BV induced DNA fragmentation and micronuclei in HL-60 cells and DNA fragmentation in human lymphocytes. Phosphate and tensin homolog (PTEN) up-regulation in HL-60 cells may induce S-phase cell cycle arrest. Forkhead transcription factor (FKHR and FKHRL1) up-regulation in human lymphocytes by whole BV treatment may be involved in the repair of damaged DNA and reduce genotoxicity. Based on these results, whole BV may exert cytotoxicity in these two cells in a different fashion.

FISH analysis of 107 prostate cancers shows that PTEN genomic deletion is associated with poor clinical outcome

This study examines the clinical impact of PTEN genomic deletions using fluorescence in situ hybridisation (FISH) analysis of 107 prostate cancers, with follow-up information covering a period of up to 10 years. Tissue microarray analysis using interphase FISH indicated that hemizygous PTEN losses were present in 42/107 (39%) of prostatic adenocarcinomas, with a homozygous PTEN deletion observed in 5/107 (5%) tumours. FISH analysis using closely linked probes centromeric and telomeric to the PTEN indicated that subband microdeletions accounted for ∼70% genomic losses. Kaplan–Meier survival analysis of PTEN genomic losses (hemizygous and homozygous deletion vs not deleted) identified subgroups with different prognosis based on their time to biochemical relapse after surgery, and demonstrated significant association between PTEN deletion and an earlier onset of disease recurrence (as determined by prostate-specific antigen levels). Homozygous PTEN deletion was associated with a much earlier onset of biochemical recurrence (P=0.002). Furthermore, PTEN loss at the time of prostatectomy correlated with clinical parameters of more advanced disease, such as extraprostatic extension and seminal vesicle invasion. Collectively, our data indicates that haploinsufficiency or PTEN genomic loss is an indicator of more advanced disease at surgery, and is predictive of a shorter time to biochemical recurrence of disease.

Loss of PTEN expression does not contribute to PDK-1 activity and PKC activation-loop phosphorylation in Jurkat leukaemic T cells

Unopposed PI3-kinase activity and 3'-phosphoinositide production in Jurkat T cells, due to a mutation in the PTEN tumour suppressor protein, results in deregulation of PH domain-containing proteins including the serine/threonine kinase PKB/Akt. In Jurkat cells, PKB/Akt is constitutively active and phosphorylated at the activation-loop residue (Thr308). 3'-phosphoinositide-dependent protein kinase-1 (PDK-1), an enzyme that also contains a PH domain, is thought to catalyse Thr308 phosphorylation of PKB/Akt in addition to other kinase families such as PKC isoforms. It is unknown however if the loss of PTEN in Jurkat cells also results in unregulated PDK-1 activity and whether such loss impacts on activation-loop phosphorylation of other putative PDK-1 substrates such as PKC. In this study we have addressed if loss of PTEN in Jurkat T cells affects PDK-1 catalytic activity and intracellular localisation. We demonstrate that reducing the level of 3'-phosphoinositides in Jurkat cells with pharmacological inhibitors of PI3-kinase or expression of PTEN does not affect PDK-1 activity, Ser241 phosphorylation or intracellular localisation. In support of this finding, we show that the levels of PKC activation-loop phosphorylation are unaffected by reductions in the levels of 3'-phosphoinositides. Instead, the dephosphorylation that occurs on PKB/Akt at Thr308 following reductions in 3'-phosphoinositides is dependent on PP2A-like phosphatase activity. Our finding that PDK-1 functions independently of 3'-phosphoinositides in T cells is also confirmed by studies in HuT-78 T cells, a PTEN-expressing cell line with undetectable levels of 3'-phosphoinositides. We conclude therefore that loss of PTEN expression in Jurkat T cells does not impact on the PDK-1/PKC pathway and that only a subset of kinases, such as PKB/Akt, are perturbed as a consequence PTEN loss.

Co-existence of high levels of the PTEN protein with enhanced Akt activation in renal cell carcinoma

Recruiting Akt to the membrane-bound phosphatidylinositol (3,4,5) trisphosphate (PIP3) is required for Akt activation. While PI3 kinase (PI3K) produces PIP3, PTEN dephosphorylates the 3-position phosphate from PIP3, thereby directly inhibiting Akt activation. PTEN is the dominant PIP3 phosphatase, as knockdown of PTEN results in increases in Akt activation in mice. The PTEN tumor suppressor gene is frequently mutated in a variety of human cancers, consistent with an inverse correlation between levels of the PTEN protein and Akt activation. We have examined PTEN expression and Akt activation in 35 primary clear cell renal cell carcinomas RCCs (ccRCCs) and 9 papillary RCCs (pRCCs) and their respective non-tumor kidney tissues. The PTEN protein was reduced in 16 ccRCCs (16/35=45.7%) and 8 pRCCs (8/9=88.9%). In these RCCs, 25.0% (4/16) of ccRCCs and 25.0% (2/8) of pRCCs expressed elevated Akt activation. 19 ccRCCc (19/35=54.3%) expressed comparable or higher levels of PTEN. Of these ccRCCs, 31.6% (6/19) showed increases in Akt activation. As PTEN dominantly inhibits Akt activation, the coexistence of high levels of the PTEN protein with enhanced Akt activation suggests the existence of novel mechanisms which attenuate PTEN function in ccRCC. These mechanisms may reduce PTEN function or increase PIP3 production.

Modulation of intracellular signaling pathways to induce apoptosis in prostate cancer cells

An understanding of the molecular pathways defining the susceptibility of prostate cancer, especially refractory prostate cancer, to apoptosis is the key for developing a cure for this disease. We previously demonstrated that up-regulating Ras signaling, together with suppression of protein kinase C (PKC), induces apoptosis. Dysregulation of various intracellular signaling pathways, including those governed by Ras, is the important element in the development of prostate cancer. In this study, we tested whether it is possible to modulate the activities of these pathways and induce an apoptotic crash among them in prostate cancer cells. Our data showed that DU145 cells express a high amount of JNK1 that is phosphorylated after endogenous PKC is suppressed, which initiates caspase 8 cleavage and cytochrome c release, leading to apoptosis. PC3 and LNCaP cells contain an activated Akt. The inhibition of PKC further augments Akt activity, which in turn induces ROS production and the accumulation of unfolded proteins in the endoplasmic reticulum, resulting in cell death. However, the concurrent activation of JNK1 and Akt, under the condition of PKC abrogation, dramatically augment the magnitude of apoptosis in the cells. Thus, our study suggests that Akt, JNK1, and PKC act in concert to signal the intracellular apoptotic machinery for a full execution of apoptosis in prostate cancer cells.

Application and interpretation of FISH in biomarker studies

Emerging genomic and proteomic data is creating new opportunities to identify novel biomarkers that will have pathway-specific therapeutic impact on cancer progression. Molecular cytogenetic and fluorescence in situ hybridization (FISH) methods have been primarily used in discovery genetic research laboratories until recently. New automated analytical platforms based on FISH technologies and tissue microarray methods are providing a rapid means to determine the impact of consistent genomic aberrations in clinical trials, and in studies designed to investigate differential chemotherapeutic response.

Molecular targets in gynaecological cancers

The application of high throughput expression profiling and other advanced molecular biology laboratory techniques has revolutionised the management of cancers and is gaining attention in the field of gynaecological cancers. Such new approaches may help to improve our understanding of carcinogenesis and facilitate screening and early detection of gynaecological cancers and their precursors. Individualised prediction of patients' responses to therapy and design of personalised molecular targeted therapy is also possible. The studies of various molecular targets involved in the various signal pathways related to carcinogenesis are particularly relevant to such applications. At the moment, the application of detection and genotyping of human papillomavirus in management of cervical cancer is one of the most well established appliances of molecular targets in gynaecological cancers. Methylation, telomerase and clonality studies are also potentially useful, especially in assisting diagnosis of difficult clinical scenarios. This post-genomic era of clinical medicine will continue to make a significant impact in routine pathology practice. The contribution of pathologists is indispensable in analysis involving tissue microarray. On the other hand, both pathologists and bedside clinicians should be aware of the limitation of these molecular targets. Interpretation must be integrated with clinical and histopathological context to avoid misleading judgement. The importance of quality assurance of all such molecular techniques and their ethical implications cannot be over-emphasised.

Phosphatase PTEN is inactivated in bovine aortic endothelial cells exposed to cyclic strain

Hemodynamic forces, including cyclic strain (CS) and shear stress (SS), have been recognized as important modulators of vascular cell morphology and function. PTEN (also known as MMAC1/TEP1) is a lipid phosphatase that leads to a decrease in intracellular phosphatidylinositol 3,4,5 trisphosphate (PIP3) and therefore can modulate the stimulating effect of phosphatidylinositol 3-kinase (PI3K). In this study, we focused on the upstream regulators of the PI3K-Akt pathway by assessing Akt, PTEN, casein kinase 2 (CK2) (a kinase that catalyzes phosphorylation of PTEN), and PI3K activity in endothelial cells (EC) exposed to CS. The activity of phospho-PTEN (n = 4) and phospho-CK2 (n = 4) increased in a time-dependent fashion, reaching maximal activity by 10 min of CS stimulation. The peak of phospho-Akt activity (n = 4) occurred later, at 60 min. Akt activity was altered by transfection of EC with dominant negative PTEN plasmids. Furthermore, CS increased PIP3 immunoreactivity in a time-dependent manner, reaching maximal activity after 60 min of CS stimulation, and these effects were affected by transfection of EC with dominant negative PTEN plasmids. Inhibition of PTEN activity had no effect on CS-mediated cell proliferation but inhibited CS-mediated suppression of apoptosis.

Implication of PTEN in production of reactive oxygen species and neuronal death in in vitro models of stroke and Parkinson's disease

Oxidative stress plays crucial role in the pathogenesis of neurodegenerative diseases. However, the precise mechanism for an increased production of reactive oxygen species (ROS) under pathological conditions is not yet fully understood. We have recently demonstrated an implication of phosphatase and tensin homologue deleted on chromosome 10 (PTEN), a tumor suppressor, in ROS generation and neuronal apoptosis induced by staurosporine. These findings raised further interest whether PTEN functions as a common mediator of oxidative stress in neurodegenerative processes. To address this issue, neural cells were exposed to oxygen-glucose deprivation (OGD) and to the neurotoxin 1-methyl-4-phenylpyridinium iodide (MPP(+)), which mimic cerebral ischemia and Parkinson's disease, respectively. OGD for 4 h followed by 16 h of reoxygenation or incubation with MPP(+) (250 microM) for 48 h induced 33% and 45% neuronal death in rat hippocampal and in human dopaminergic SH-SY5Y neurons, respectively, accompanied by a gradual increase in the intracellular level of ROS. The increase in ROS by OGD and by MPP(+) did not cause oxidative inactivation of PTEN and thus, PTEN remains constitutively active. In support, the protein level of PTEN was not reduced in both cell cultures after challenging with OGD or MPP(+). Importantly, the elevated intracellular ROS levels and the neuronal death caused by OGD or by MPP(+) toxicity were significantly inhibited when PTEN was downregulated by a specific antisense oligonucleotide or by siRNA. Because SOD2 protein level is not altered either by knockdown of PTEN nor by an inhibition of the PI3K/Akt signalling, we suggest that SOD2 do not contribute to the pathomechanism of oxidative stress induced by PTEN or by inhibiting the related Akt signalling. The present study highlights PTEN as a crucial and common mediator of ROS generation and neuronal death and suggests that PTEN could become a potential therapeutic target for interfering with neurodegeneration.

Interphase FISH analysis of PTEN in histologic sections shows genomic deletions in 68% of primary prostate cancer and 23% of high-grade prostatic intra-epithelial neoplasias

Prostate cancer (CaP) is characterized by the accumulation of both genetic and epigenetic alterations that transform premalignant lesions to invasive carcinoma. However, the molecular events underlying this critical transition are poorly understood. One of the important genes that might play a role in CaP development is the PTEN gene. At the present time, there has been no systematic analysis of the incidence of genomic PTEN deletion by fluorescence in situ hybridization (FISH) in CaP and associated preneoplastic histologic lesions. This study assesses the frequency of PTEN deletion by interphase FISH analysis in CaP and prostatic intra-epithelial neoplasia (PIN). Dual-color FISH was performed using DNA probes for bands 10q23.3 (PTEN locus) and chromosome 10 centromere using 35 radical prostatectomy specimens. PTEN deletions were not found in 3/3 of stroma, 6/6 samples of benign glandular epithelium, and 12/12 samples of low-grade PIN. However, PTEN deletions were found in 3/13 (23%) of high-grade PIN and 24/35 (68%) of CaP. Concordance was observed between PTEN deletion status and the overall cellular PTEN protein expression levels, as assessed by immunohistochemistry. The high frequency of PTEN deletion observed in CaP versus precursor lesions implicates a pivotal role for PTEN haploinsufficiency in the transition from preneoplastic PIN to CaP. Moreover, this observation is an important consideration for novel therapeutic trials in CaP in which biologic efficacy is influenced by the activity level of PTEN. These findings draw attention to the usefulness of this relatively simple FISH assay for future applications in clinical laboratories.

ATM activation is accompanied with earlier stages of prostate tumorigenesis

The ATM (ataxia telangiectasia mutated) kinase plays an essential role in maintaining genome integrity by coordinating cell cycle arrest, apoptosis, and DNA damage repair. Phosphorylation of ATM at serine 1981 (ATMpSer1981) by DNA damage activates ATM, which subsequently phosphorylates H2AX Ser139 (gammaH2AX), Chk2 Thr68 (Chk2pThr68), and p53 Ser15 (p53pSer15). To determine the role of the ATM pathway in prostate cancer tumorigenesis, we have analyzed 35 primary prostate cancer specimens for ATMpSer1981 (ATM activation), Chk2pThr68, gammaH2AX, and p53pSer15 by immunohistochemistry (IHC) in normal glands, prostatic intraepithelial neoplasias (PINs), and carcinomas. Increases in the intensities of ATMpSer1981, Chk2pThr68, and gammaH2AX and in the percentage of cells that are positive for ATMpSer1981, Chk2pThr68, or gammaH2AX were observed in PINs (p<0.001) compared to normal prostatic glands and carcinoma. However, this pattern of immunostaining was not seen for p53pSer15. Thus, ATM and Chk2 are specifically activated in PINs. As PINs are generally regarded as precursors of prostatic carcinoma, our results suggest that ATM and Chk2 activation at earlier stages of prostate tumorigenesis suppresses tumor progression, with attenuation of ATM activation leading to cancer progression.

Relationship among PTEN, matrix metalloproteinase-9, and Caspase-3 Expression in gastric carcinoma

AIM: To study the expression of PTEN, matrix metalloproteinase-9 (MMP-9), and Caspase-3 in gastric cancer, and to discuss their roles and correlations in the occurrence, development, invasion and metastasis of gastric cancer.

METHODS: SP immunohistochemistry was used to measure the expression of PTEN, MMP-9, and Caspase-3 in 54 samples of gastric carcinoma selected from paraffin wax embodied specimens with complete clinicopathological data, and another 15 cases of normal gastric mucosa.

RESULTS: The expression of PTEN in gastric cancer was low (28/54, 51.9%), and reduced with the increased invasive depth (P= 0.004) and clinical stages (P = 0.001), reduced histological differentiation (P = 0.008) and occurrence of lymph node (P = 0.003) and long distance metastasis (P = 0.015). The expression of MMP-9 in gastric cancer was high (41/54, 75.9%), and increased with increased invasive depth (P = 0.04) and clinical stages (P = 0.039), reduced histological differentiation (P = 0.009), and occurrence of lymph node metastasis (P = 0.025). The expression of Caspase-3 in gastric cancers was low (12/54, 22.2%), and reduced with increased clinical stages (P = 0.015), reduced histological differentiation (P = 0.035) and occurrence of lymph node metastasis (P = 0.045). The expression of PTEN and MMP-9 (r = -0.543, P = 0.001), Caspase-3 and MMP-9 (r = -0.741, P = 0.001) were in inversely correlation, while the expression of PTEN and Caspase-3 (r = 0.515, P = 0.001) were in positive correlation in gastric cancer.

CONCLUSION: PTEN and Caspase-3 are lowly expressed in gastric caner, while MMP-9 is highly expressed. PTEN, MMP-9, and Caspase-3 can serve as the markers in the diagnosis and prognosis of gastric cancer.