Frequent loss of PTEN expression is linked to elevated phosphorylated Akt levels, but not associated with p27 and cyclin D1 expression, in primary epithelial ovarian carcinomas

Correlation between protein expression of PTEN in human pancreatic cancer and the proliferation, infiltration, metastasis and prognosis

In order to investigate the correlation between protein expression of PTEN and the proliferation, infiltration, metastasis and prognosis in pancreatic cancer, immunohistochemical SP method was used to examine the protein expression of PTEN, PCNA, MVD, MMP-2, MMP-9 and TUNEL method to detect the levels of apoptosis of pancreatic cells in 41 pancreatic head cancers from regional pancreatectomy (RP) and 10 normal pancreatic tissues. The results showed that among 41 cases of pancreatic cancers, the positive staining of PTNE (39.02%) was significantly weaker than that in normal pancreatic tissues (P < 0.05). The levels of PCNA labeling index (LI), apoptotic index (AI), microvessel density (MVD), MMP-2 LI and MMP-9 LI were decreased gradually with the increase of the expression intensity of PTEN, and there was a significant difference in the above parameters among the patients having different expression levels of PTEN (P < 0.01 or P < 0.05). There was a negative correlation between the expression of PTEN and PCNA LI, MVD, MMP-2 LI, MMP-9 LI, and a positive correlation between AI and the expression of PTEN. The expression intensity of PTEN was correlated with the postoperative survival of the patients with pancreatic cancer (chi2 = 22.3400, P < 0.0001, RR = 2.030). It was suggested that the expression levels of PTEN protein were closely related with proliferation, infiltration and metastasis in human pancreatic cancer, and the expression of PTEN protein was one of the prognostic factors for pancreatic cancer following RP.

The search for genes contributing to endometriosis risk

BACKGROUND

Genetic variation contributes to the risk of developing endometriosis. This review summarizes gene mapping studies in endometriosis and the prospects of finding gene pathways contributing to disease using the latest genome-wide strategies.

METHODS

To identify candidate-gene association studies of endometriosis, a systematic literature search was conducted in PubMed of publications up to 1 April 2008, using the search terms 'endometriosis' plus 'allele' or 'polymorphism' or 'gene'. Papers included were those with information on both case and control selection, showed allelic and/or genotypic results for named germ-line polymorphisms and were published in the English language.

RESULTS

Genetic variants in 76 genes have been examined for association, but none shows convincing evidence of replication in multiple studies. There is evidence for genetic linkage to chromosomes 7 and 10, but the genes (or variants) in these regions contributing to disease risk have yet to be identified. Genome-wide association is a powerful method that has been successful in locating genetic variants contributing to a range of common diseases. Several groups are planning these studies in endometriosis. For this to be successful, the endometriosis research community must work together to genotype sufficient cases, using clearly defined disease classifications, and conduct the necessary replication studies in several thousands of cases and controls.

CONCLUSIONS

Genes with convincing evidence for association with endometriosis are likely to be identified in large genome-wide studies. This will provide a starting point for functional and biological studies to develop better diagnosis and treatment for this debilitating disease.

Analysis of complex protein kinase B signalling pathways in human prostate cancer samples

OBJECTIVE

To provide a rational basis for targeted treatment approaches in prostate cancer deregulation of the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (PKB/Akt) system was analysed.

PATIENTS AND METHODS

In all, 45 patients with primary localized prostate cancer that underwent radical prostatectomy were included in the present study. Upon scoring of the pathological grade, expression and phosphorylation levels of PKB/Akt and relevant downstream targets were determined in tissue specimens by immunohistochemistry using specific antibodies against PTEN, PKB/Akt, its downstream targets, and the respective phosphorylated proteins.

RESULTS

Most patients (>90%) had up-regulated expression and/or phosphorylation of PKB/Akt in the malignant tissue compared with the surrounding benign tissue, with a higher prevalence of increased phosphorylated PKB/Akt in patients with Gleason scores of > or =6 (100%) compared with those with Gleason scores of 4-5 (five of 13 patients), and in particular in patients with clinical progression. Up-regulated phosphorylation of PKB/Akt occurred either in association with loss or inactivation of PTEN or in a PTEN-independent manner. Enhanced phosphorylation levels of the PKB/Akt substrates glycogen synthase kinase 3, the mammalian target of rapamycin or the forkhead transcription factor like 1 (FKHRL1) were found in 29%, 42% and 40% of the tumours, respectively. Of these, only increased phosphorylated-FKHRL1 levels correlated with clinical progression. Interestingly, 80% of patients had a notable overexpression but not phosphorylation of the eucaryotic initiation factor 4E binding protein.

CONCLUSION

Deregulation of p-PKB/Akt is common in localized prostate cancer and has a putative value as predictive marker for disease progression and as therapeutic target. However, as a consequence of the substantial heterogeneity in the expression and phosphorylation levels of relevant PKB/Akt effector pathways, for a rational use of specified inhibitors of the PI3K/PKB system a complex pattern testing of expression and activity of the respective target proteins for prediction of efficacy and prognosis seems mandatory.

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.

MicroRNA expression profiling in human ovarian cancer: miR-214 induces cell survival and cisplatin resistance by targeting PTEN

MicroRNAs (miRNA) represent a novel class of genes that function as negative regulators of gene expression. Recently, miRNAs have been implicated in several cancers. However, aberrant miRNA expression and its clinicopathologic significance in human ovarian cancer have not been well documented. Here, we show that several miRNAs are altered in human ovarian cancer, with the most significantly deregulated miRNAs being miR-214, miR-199a*, miR-200a, miR-100, miR-125b, and let-7 cluster. Further, we show the frequent deregulation of miR-214, miR-199a*, miR-200a, and miR-100 in ovarian cancers. Significantly, miR-214 induces cell survival and cisplatin resistance through targeting the 3'-untranslated region (UTR) of the PTEN, which leads to down-regulation of PTEN protein and activation of Akt pathway. Inhibition of Akt using Akt inhibitor, API-2/triciribine, or introduction of PTEN cDNA lacking 3'-UTR largely abrogates miR-214-induced cell survival. These findings indicate that deregulation of miRNAs is a recurrent event in human ovarian cancer and that miR-214 induces cell survival and cisplatin resistance primarily through targeting the PTEN/Akt pathway.

Targeting the PI3K/Akt/mTOR pathway: effective combinations and clinical considerations

The PI3K/Akt/mTOR pathway is a prototypic survival pathway that is constitutively activated in many types of cancer. Mechanisms for pathway activation include loss of tumor suppressor PTEN function, amplification or mutation of PI3K, amplification or mutation of Akt, activation of growth factor receptors, and exposure to carcinogens. Once activated, signaling through Akt can be propagated to a diverse array of substrates, including mTOR, a key regulator of protein translation. This pathway is an attractive therapeutic target in cancer because it serves as a convergence point for many growth stimuli, and through its downstream substrates, controls cellular processes that contribute to the initiation and maintenance of cancer. Moreover, activation of the Akt/mTOR pathway confers resistance to many types of cancer therapy, and is a poor prognostic factor for many types of cancers. This review will provide an update on the clinical progress of various agents that target the pathway, such as the Akt inhibitors perifosine and PX-866 and mTOR inhibitors (rapamycin, CCI-779, RAD-001) and discuss strategies to combine these pathway inhibitors with conventional chemotherapy, radiotherapy, as well as newer targeted agents. We will also discuss how the complex regulation of the PI3K/Akt/mTOR pathway poses practical issues concerning the design of clinical trials, potential toxicities and criteria for patient selection.

Targeting Akt in cancer therapy

In an effort to improve therapeutic options in cancer, many investigational drugs are being developed to inhibit signaling pathways that promote the survival of cancer cells. The prototypic pathway that promotes cellular survival is the phosphoinositide 3'-kinase/Akt/mammalian target of rapamycin pathway, which is constitutively activated in many types of cancers. Mechanisms for activation of the serine/threonine kinase, Akt, include loss of tumor suppressor PTEN (phosphatase and tensin homolog deleted on chromosome 10) function, amplification or mutation of phosphoinositide 3'-kinase, amplification of Akt, activation of growth factor receptors and exposure to carcinogens. Activation of Akt promotes cellular survival as well as resistance to treatment with chemotherapy and/or radiation therapy. Immunohistochemical analyses have shown that Akt is activated in many types of cancers and preneoplastic lesions, and Akt activation is a poor prognostic factor in various cancers. Taken together, these data demonstrate that Akt is a valid target for inhibition. This review will focus on published data using different approaches to inhibit Akt. We will also consider how the complex regulation of the phosphoinositide 3'-kinase/Akt/mammalian target of rapamycin pathway poses practical issues concerning the design of clinical trials, potential toxicities and the likelihood of finding a therapeutic index when targeting such a critical cellular pathway.

Novel agents in ovarian cancer

The standard treatment for epithelial ovarian cancer remains surgical debulking and chemotherapy with carboplatin and paclitaxel. However, the majority of patients relapse, and few, if any, achieve a cure. Future advancement in treatment should aim at targeting the biology of the disease, specifically mechanisms critical to tumor initiation and progression. Several Phase I and II clinical trials have identified novel opportunities for therapy. The most promising venues appear to be the antiangiogenic agents and the inhibitors of intracellular signaling. Novel modalities of delivering cytotoxics to tumor cells by exploiting ovarian cancer-specific biomarkers are also being tested, and appear promising. Immunomodulatory agents are being developed for consolidation therapy. Although devoid of the common side effects associated with chemotherapy, the use of targeted agents is associated with specific toxicities, related to the biological processes they block. The main challenge for future successful clinical development will be defining molecular markers predictive of response and judicious patient selection based on the biological features of the tumor. Individualized treatment driven by molecular characteristics will open the door to a new age in anticancer medicine.

EF24 induces G2/M arrest and apoptosis in cisplatin-resistant human ovarian cancer cells by increasing PTEN expression

We report that EF24, a synthetic compound 3,5-bis(2-flurobenzylidene)piperidin-4-one, greatly inhibits cisplatin-resistant (CR) human ovarian cancer cell proliferation. The inhibitory effect of EF24 on cell proliferation is associated with G(2)/M phase cell cycle arrest and increased G(2)/M checkpoint protein (pp53, p53, and p21) levels. Within 24 h following treatment, EF24 induced apoptosis in CR cells. The apoptosis was partially blocked by the general caspase inhibitor z-VAD. Within 12 h, EF24 induced a membranous FasL expression, consistent with a substantial decrease in the Ser(473) and Thr(308) phosphorylation of Akt, a known negative regulator of FasL transcription. Also, EF24 activated the phosphorylated PTEN and marginally up-regulated total PTEN expression through the inhibition of ubiquitin-mediated PTEN degradation. Suppression of PTEN expression with siRNA significantly reduced the p53 and p21 levels and activated Akt phosphorylation at Ser(473) and Thr(308), resulting in decreased apoptosis and increased cell survival. On the other hand, overexpression of PTEN markedly induced apoptosis. Our results clearly suggested that EF24 induced significant increase in PTEN expression. The up-regulation of PTEN inhibited Akt and MDM2, which enhanced the level of p53, thereby inducing G(2)/M arrest and apoptosis. Therefore, EF24 appears to have a potential therapeutic role in human ovarian cancer through the activation of PTEN.

Combination of all-trans retinoic acid and interferon-gamma suppressed PI3K/Akt survival pathway in glioblastoma T98G cells whereas NF-kappaB survival signaling in glioblastoma U87MG cells for induction of apoptosis

Phosphatase and tension homolog located on chromosome ten (PTEN) is a tumor suppressor as it negatively regulates activation of Akt. Mutation or deletion of PTEN has been found in as high as 80% of glioblastomas, which harbor aberrant cell signaling passing through the phosphatidylinositol-3-kinase (PI3K) and Akt (PI3K/Akt) survival pathway. Glioblastoma cells without functional PTEN are not easily amenable to apoptosis. We investigated the possibility of modulation of signal transduction pathways for induction of apoptosis in human glioblastoma T98G (PTEN-harboring) and U87MG (PTEN-deficient) cell lines after treatment with the combination of all-trans retinoic acid (ATRA) and interferon-gamma (IFN-gamma). Treatment with ATRA plus IFN-gamma stimulated PTEN expression and suppressed Akt activation in T98G cells, whereas no PTEN expression but Akt activation in U87MG cells under the same conditions. Pretreatment of U87MG cells with the PI3K inhibitor LY294002 could prevent Akt activation. Interestingly, ATRA plus IFN-gamma could significantly decrease cell viability and increase morphological features of apoptosis in both cell lines. Combination of ATRA and IFN-gamma showed more efficacy than IFN-gamma alone in causing apoptosis that occurred due to increases in Bax:Bcl-2 ratio, mitochondrial release of cytochrome c, and caspase-3 activity. Luciferase reporter gene assay showed that combination of ATRA and IFN-gamma significantly down regulated transcriptional activity of the nuclear factor kappa B (NF-kappaB), a survival signaling factor, in U87MG cells. Thus, combination of ATRA and IFN-gamma caused significant amounts of apoptosis in T98G cells due to suppression of the PI3K/Akt survival pathway while the same treatment caused apoptosis in U87MG cells due to down regulation of the NF-kappaB activity. Therefore, the combination of ATRA and IFN-gamma could modulate different survival signal transduction pathways for induction of apoptosis and should be considered as an effective therapeutic strategy for controlling the growth of both PTEN-harboring and PTEN-deficient glioblastomas.

Prognostic implications of the nuclear localization of Y-box-binding protein-1 and CXCR4 expression in ovarian cancer: their correlation with activated Akt, LRP/MVP and P-glycoprotein expression

The nuclear localization of Y-box-binding protein-1 (YB-1) is known to be a poor prognostic factor in several human malignancies, including ovarian carcinoma. Following on from our basic study dealing with microarray analyses of YB-1-associated gene expression in ovarian cancer cells, we examined whether nuclear localization of YB-1 is associated with the expression of CXCR4, a vault protein named lung resistance-related vault protein (LRP/MVP), phosphorylated Akt (p-Akt) or P-glycoprotein (P-gp) in human ovarian carcinoma. Fifty-three surgically resected ovarian carcinomas treated with paclitaxel and carboplatin were examined immunohistochemically for nuclear YB-1 expression and intrinsic expression of p-Akt, P-gp, LRP/MVP and CXCR4. Nuclear expression of YB-1 demonstrated significant correlation with p-Akt, P-gp and LRP expression, but no relationship with CXCR4 expression. By multivariate analysis, only YB-1 nuclear expression and CXCR4 expression were independent prognostic factors with regard to overall survival. These results indicate that YB-1 nuclear expression and CXCR4 expression are important prognostic factors in ovarian carcinoma.

Variants in EMX2 and PTEN do not contribute to risk of endometriosis

Endometriosis has a genetic component, and significant linkage has been found to a region on chromosome 10q. Two candidate genes, EMX2 and PTEN, implicated in both endometriosis and endometrial cancer, lie on chromosome 10q. We hypothesized that variation in EMX2 and/or PTEN could contribute to the risk of endometriosis and may account for some of the linkage signal on 10q. We genotyped single nucleotide polymorphisms (SNPs) in a case-control design to evaluate association between endometriosis and common variations in these two genes. The genotyping and statistical analysis were based on samples collected from Australian volunteers. The cases were 768 unrelated women with surgically confirmed endometriosis selected from affected sister pair (ASP) families participating in the Australian Genes behind Endometriosis Study. The controls were 768 female participants in twin studies who, based on screening questions, did not have a diagnosis of endometriosis. Genotypes of 22 SNPs in the EMX2 gene and 15 SNPs in the PTEN gene were the main outcome measures. Statistical analysis provided measures of linkage disequilibrium and association. Permutation testing showed no globally significant association between any SNPs or haplotypes and endometriosis for either gene. It is unlikely that the EMX2 or PTEN gene variants investigated contribute to risk for initiation and/or development of endometriosis.

A Novel Substrate Mimetic Inhibitor of PKB/Akt Inhibits Prostate Cancer Tumor Growth in Mice by Blocking the PKB Pathway

We describe a novel, potent peptide substrate mimetic inhibitor of protein kinase B (PKB/Akt). The compound selectively kills prostate cancer cells, in which PKB is highly activated, but not normal cells, or cancer cells in which PKB is not activated. The inhibitor induces apoptosis and inhibits the phosphorylation of PKB substrates in prostate cancer cell lines and significantly increases the efficacy of chemotherapy agents to induce prostate cancer cell death, when given in combination. In vivo, the inhibitor exhibits a strong antitumor effect in two prostate cancer mouse models. Moreover, treated animals develop significantly less lung metastases compared to untreated ones, and the effect is accompanied by a significant decrease in blood PSA [prostate-specific antigen] levels in treated animals. This compound and its potential analogues may be developed into novel, potent, and safe anticancer agents, both as stand-alone treatment and in combination with other chemotherapy agents.

Antiproliferative activity of sulforaphane in Akt-overexpressing ovarian cancer cells

Epidemiologic studies show a correlation between increased consumption of fruits and vegetables with reduced risk of ovarian cancer. One major bioactive compound found in cruciferous vegetables, particularly broccoli, is sulforaphane, derived from the breakdown of glucoraphanin. We observed potent antiproliferative effects of sulforaphane on human ovarian cancer cell line SKOV3 (IC(50) 40 micromol/L) and mouse ovarian cancer cell lines C3 and T3 (IC(50) 25 micromol/L each) by cell viability assays. The loss of viability is reflected by a down-regulation of cell cycle transition regulators cyclin D1, cyclin-dependent kinase 4 (cdk4), and cdk6. The upstream mediators of sulforaphane effects on the cell cycle in ovarian cancer are still unknown. However, because the Akt signal transduction pathway is overactivated in ovarian cancer, we investigated the effects of sulforaphane on this prosurvival pathway. Both total Akt protein and active phosphorylated levels of Akt (Ser(473)) and phosphoinositide 3-kinase were significantly decreased in sulforaphane-treated SKOV3, C3, and T3 cells with a concomitant inhibition of Akt kinase activity by sulforaphane in SKOV3 and C3 cells. This inhibitory effect of sulforaphane leads to a potent induction of apoptosis in all three cell lines, along with the cleavage of poly(ADP)ribose polymerase. Our study is the first to report the antiproliferative effects of sulforaphane in ovarian cancer and identifying the Akt pathway as a target of sulforaphane, with implications for the inhibition of carcinogenesis by diet-based chemoprevention.

Specific inhibition of AKT2 by RNA interference results in reduction of ovarian cancer cell proliferation: Increased expression of AKT in advanced ovarian cancer

The protein kinase AKT is involved in several signaling pathways that are important for tumor development and progression, suggesting that AKT might be an interesting target for a molecular tumor therapy. In this study, we investigated the AKT expression in ovarian carcinomas and the role of the AKT isoforms to ovarian cancer cell proliferation. We observed an increased AKT expression in 58% of the primary ovarian carcinomas as compared to normal ovaries by immunohistochemistry. AKT expression was significantly associated with positive lymph node status (P=0.002) and advanced FIGO stage (P=0.009). In western blot analysis, total AKT was expressed in all ovarian cancer cell lines and HOSE cells, while phosphorylated AKT was only observed in OVCAR-3 and SKOV-3 cells. The isoforms AKT1 and AKT2 were expressed at the mRNA level in all cell lines, while no relevant AKT3 mRNA levels were detected by conventional and quantitative RT-PCR. To determine the effects on cell proliferation, we used the unselective PI3K-inhibitor LY294002 as well as RNA interference to selectively inhibit the AKT isoforms. Treatment with LY294002 and the AKT2 siRNA reduced proliferation of OVCAR-3 cells. Our results show that AKT is expressed in a subpopulation of advanced ovarian carcinomas suggesting a role for this protein in the progression of this entity. Deactivation of AKT, especially AKT2 can result in reduction of cell growth. Accordingly, AKT is an interesting target for therapeutic intervention in ovarian cancer.

Oncolytic virotherapy synergism with signaling inhibitors: Rapamycin increases myxoma virus tropism for human tumor cells

Myxoma virus is a rabbit-specific poxvirus pathogen that also exhibits a unique tropism for human tumor cells and is dramatically oncolytic for human cancer xenografts. Most tumor cell lines tested are permissive for myxoma infection in a fashion intimately tied to the activation state of Akt kinase. A host range factor of myxoma virus, M-T5, directly interacts with Akt and mediates myxoma virus tumor cell tropism. mTOR is a regulator of cell growth and metabolism downstream of Akt and is specifically inhibited by rapamycin. We report that treatment of nonpermissive human tumor cell lines, which normally restrict myxoma virus replication, with rapamycin dramatically increased virus tropism and spread in vitro. This increased myxoma replication is concomitant with global effects on mTOR signaling, specifically, an increase in Akt kinase. In contrast to the effects on human cancer cells, rapamycin does not increase myxoma virus replication in rabbit cell lines or permissive human tumor cell lines with constitutively active Akt. This indicates that rapamycin increases the oncolytic capacity of myxoma virus for human cancer cells by reconfiguring the internal cell signaling environment to one that is optimal for productive virus replication and suggests the possibility of a potentially therapeutic synergism between kinase signaling inhibitors and oncolytic poxviruses for cancer treatment.

PTEN mutation, expression and LOH at its locus in ovarian carcinomas. Relation to TP53, K-RAS and BRCA1 mutations

OBJECTIVE

We aimed to evaluate frequency of PTEN mutation, LOH and expression in ovarian tumors. In search for a molecular pathway, we confronted PTEN gene mutations with TP53, K-RAS and BRCA1 gene status in the same tumors. We also evaluated clinical significance of PTEN expression in a subgroup of patients uniformly treated with platinum-based regimens.

METHODS

Molecular analysis was performed on 105 ovarian tumors (100 carcinomas) with the use of the SSCP and sequencing. Seventy-six tumors were analyzed for LOH at 10q23 locus with the use of six polymorphic markers. Immunohistochemical PTEN expression was done on paraffin-embedded material. Multivariate and univariate analysis was performed with the STATA program.

RESULTS

PTEN mutations occurred in 5/100 (5%) of all carcinomas and in 3/15 (20%) of endometrioid carcinomas (EC). Low-grade EC that developed in borderline tumors had PTEN and/or K-RAS mutation (4/5, 80%), while high-grade EC had TP53 mutations only. There was a reverse association between PTEN and TP53 mutations (P = 0.005). LOH at PTEN locus was found in 60% of endometrioid and in 28% of serous and clear cell carcinomas. PTEN expression did not associate with PTEN mutations or LOH. Strong PTEN expression diminished risk of death in a TP53 positive group only (HR = 0.35, P = 0.029).

CONCLUSION

Our results suggest that PTEN mutations may play a role in a development of low-grade endometrioid tumors. PTEN haploinsufficiency caused by LOH or epigenetic events may possibly contribute to development of other histological types and may be an adverse prognostic factor.

Endocrine signaling in ovarian surface epithelium and cancer

Ovarian cancer is the sixth most common cancer and the fifth leading cause of cancer-related death among women in developed countries. Greater than 85% of human ovarian cancer arises within the ovarian surface epithelium (OSE), with the remainder derived from granulosa cells or, rarely, stroma or germ cells. The pathophysiology of ovarian cancer is the least understood among all major human malignancies because of a poor understanding of the aetiological factors and mechanisms of ovarian cancer progression. There is increasing evidence suggesting that several key reproductive hormones, such as GnRH, gonadotrophins and sex steroids, regulate the growth of normal OSE and ovarian cancer cells. The objective of this review was to highlight the effects of these endocrine factors on ovarian cancer cell growth and to summarize the signalling mechanisms involved in normal human OSE and its neoplastic counterparts.

Molecular and Pathologic Aspects of Endometrial Carcinogenesis

Endometrial cancer is the most common gynecological malignancy, with 41,000 new cases projected in the United States for 2006. Two different clinicopathologic subtypes are recognized: the estrogen-related (type I, endometrioid) and the non–estrogen-related types (type II, nonendometrioid such as papillary serous and clear cell). The morphologic differences in these cancers are mirrored in their molecular genetic profile with type I showing defects in DNA-mismatch repair and mutations in PTEN, K-ras, and beta-catenin, and type II showing aneuploidy and p53 mutations. This article reviews the genetic aspects of endometrial carcinogenesis and progression. We will define the precursor lesion of type I endometrioid cancer and the role of genetics and estrogen in its progression.

Patterns of loss of heterozygosity at 10q23.3 and microsatellite instability in endometriosis, atypical endometriosis, and ovarian carcinoma arising in association with endometriosis

Genetic aberrations, such as loss of heterozygosity (LOH) and mutations leading to functional inactivation of the PTEN tumor suppressor gene, located on chromosome 10q23.3, have been shown to be associated with approximately one third of ovarian adenocarcinomas. In addition, microsatellite instability (MSI) leading to the functional inactivation of the PTEN gene has also been reported for ovarian adenocarcinomas with frequencies varying from 6 to 37%. However, the frequency of PTEN gene abnormalities has not been well studied or evaluated in lesions such as typical and atypical endometriosis. The aim of this study was to investigate a possible sequential progression from endometriosis through atypical endometriosis to ovarian carcinoma by assessing LOH at 10q23.3 and MSI in those entities. Genomic DNA was analyzed for LOH and MSI at 3 loci on chromosome 10, using polymerase chain reaction amplification. Significant differences in LOH were seen between endometriosis (4.3%) and ovarian carcinoma (23.5%) at D10S608. The differences at the other 2 loci were not significant. A high frequency of MSI was found in endometriosis (82.6%) and atypical endometriosis (75%); however, the differences were not significant. These results suggest that LOH at D105608 may possibly be an important molecular event in the progression of endometriosis to carcinoma. This study highlights that endometriosis and atypical endometriosis might act as precursor lesions that have the potential to progress into ovarian adenocarcinoma.

Over-expression of PTEN sensitizes human ovarian cancer cells to cisplatin-induced apoptosis in a p53-dependent manner

OBJECTIVE

Resistance to cisplatin-centered chemotherapy is a major cause of treatment failure in human ovarian cancer. Whereas PTEN, a tumor suppressor gene product, is believed to promote apoptosis primarily via inactivation of the PI3K/Akt cell survival pathway, recent evidence suggests that PTEN may function independently of this pathway. Activation of p53 is a key determinant of sensitivity to cisplatin-induced apoptosis. Whether PTEN can facilitate cisplatin sensitivity, and this involves the activation of p53, remains unclear. In this study, we determined whether and how PTEN over-expression sensitizes ovarian cancer cells to CDDP-induced apoptosis.

METHODS AND RESULTS

Using pairs of chemosensitive and chemoresistant ovarian cancer cell lines (OV20028 vs. C13* and A2780-s vs. A2780-cp) as an in vitro model, we have examined the influence of PTEN over-expression in regulation of cisplatin-induced apoptosis. Apoptosis was assessed morphologically by Hoechst staining and confirmed by the detection of cleaved products of caspase-3 and PARP by Western blot. Over-expression of PTEN by PTEN cDNA transfection up-regulates p53 content and increases the sensitivity of chemoresistant cells to cisplatin-induced apoptosis without detectable changes in the levels of phosphorylated Akt and FKHR as well as FasL mRNA abundance as determined by Western blot and RT-PCR, respectively. PTEN-mediated chemosensitization was attenuated by p53 down-regulation by siRNA in C13*, a chemoresistant wild-type p53 cell. Moreover, PTEN over-expression failed to sensitize the chemoresistant p53 mutant ovarian cancer cell line A2780-cp to cisplatin-induced apoptosis, unless wild-type p53 was reconstituted by adenoviral p53 infection.

CONCLUSION

Taken together, these data suggest that PTEN over-expression may represent a novel therapeutic approach for chemoresistant human ovarian cancer and that this may involve a p53-mediated apoptotic cascade independent of the PI3K/Akt pathway.

Molecular prognostic markers in ovarian cancer: toward patient-tailored therapy

In ovarian cancer the ceiling seems to be reached with chemotherapeutic drugs. Therefore a paradigm shift is needed. Instead of treating all patients according to standard guidelines, individualized molecular targeted treatment should be aimed for. This means that molecular profiles of the distinct ovarian cancer subtypes should be established. Until recently, most studies trying to identify molecular targets were single-marker studies. The prognostic role of key components of apoptotic and prosurvival pathways such as p53, EGFR, and HER2 has been extensively studied because resistance to chemotherapy is often caused by failure of tumor cells to go into apoptosis. However, it is more than likely that different ovarian cancer subtypes with extensive molecular heterogeneity exist. Therefore, exploration of the potential of specific tumor-targeted therapy, based on expression of a prognostic tumor profile, may be of interest. Recently, new profiling techniques, such as DNA and protein microarrays, have enabled high-throughput screening of tumors. In this review an overview of the current status of prognostic marker and molecular targeting research in ovarian cancer, including microarray studies, is presented.

Immunohistochemical expression of phospho-Akt in uveal melanoma

The aim of this study was to evaluate the immunohistochemical expression of phospho-Akt and its possible association with clinicopathological features in uveal melanoma. Thirty-four enucleated eyes from 34 patients with choroidal melanoma were included in the study. Patients were divided into two groups based on the treatment received: (1) primary enucleation (n=18); (2) radiotherapy, either external beam or brachytherapy, and enucleation (n=16). Clinicopathological data were obtained. The minimum follow-up time was 72 months. Immunohistochemistry for phospho-Akt was performed using an anti-phospho-Akt (Ser 473) rabbit antibody. The association of phospho-Akt with clinicopathological parameters was investigated in each patient group separately. Phospho-Akt immunostaining was cytoplasmic in both groups. In the primary enucleation group, 10 tumours were phospho-Akt positive (55.5%). Patients with phospho-Akt-positive tumours were older (average 70.8 years versus 59 years, P=0.01) and phospho-Akt immunoreactivity was significantly associated with a higher risk of metastatic disease (Kaplan-Meier analysis, P=0.02). In the radiotherapy and enucleation group, nine tumours were phospho-Akt positive (56.2%). The absence of phospho-Akt expression was correlated with male gender (P=0.02). The following conclusions can be drawn from this study: (1) phospho-Akt immunoexpression was detected in 55.5% of uveal melanomas treated with primary enucleation and in 56.2% of uveal melanomas treated with radiotherapy and enucleation; (2) the association of phospho-Akt immunoexpression with clinicopathological features, including prognosis, merits further study.

Expression of PTEN in the progression of cervical neoplasia and its relation to tumor behavior and angiogenesis in invasive squamous cell carcinoma

BACKGROUND AND OBJECTIVES

Loss of PTEN expression has been associated with tumor progression and adverse patient outcome. The purpose of this study was to evaluate PTEN expression in the successive steps of progression in cervical neoplasia and to determine its correlation with tumor angiogenesis and clinicopathologic features in squamous cell carcinoma of the uterine cervix.

METHODS

Immunohistochemical staining with anti-PTEN antibody was performed in a total of 160 patients with 12 normal cervical epithelium, 63 cervical intraepithelial neoplasia (33 CIN I, 30 CIN III), and 85 cervical squamous cell carcinomas. Microvessels were immunohistochemically labeled with an antibody for CD34. Computerized image analysis was used to evaluate microvessel density (MVD).

RESULTS

Reduced PTEN expression progressively increased along the continuum from normal epithelium to squamous cell carcinoma (P < 0.01). There was no significant correlation between PTEN expression and MVD. On univariate analysis, stage and reduced PTEN expression were significant prognostic factors for both disease-free and overall survival. However, stage was the only independent prognostic factor by multivariate analysis.

CONCLUSIONS

Our results suggest that tumor progression in the cervical epithelium is accompanied by loss of PTEN protein expression. Reduced PTEN expression is not associated with tumor angiogenesis of squamous cell carcinoma of the uterine cervix.

Beta1,4-galactosyltransferase V functions as a positive growth regulator in glioma

beta1,4-galactosyltransferase V (GalT V; EC 2.4.1.38) can effectively galactosylate the GlcNAcbeta1-->6Man arm of the highly branched N-glycans that are characteristic of glioma. Previously, we have reported that the expression of GalT V is increased in the process of glioma. However, currently little is known about the role of GalT V in this process. In this study, the ectopic expression of GalT V could promote the invasion and survival of glioma cells and transformed astrocytes. Furthermore, decreasing the expression of GalT V in glioma cells promoted apoptosis, inhibited the invasion and migration and the ability of tumor formation in vivo, and reduced the activation of AKT. In addition, the activity of GalT V promoter could be induced by epidermal growth factor, dominant active Ras, ERK1, JNK1, and constitutively active AKT. Taken together, our results suggest that GalT V functioned as a novel glioma growth activator and might represent a novel target in glioma therapy.

Inactivation of PTEN is associated with a low p27Kip1 protein expression in breast carcinoma

BACKGROUND

It was previously demonstrated that PTEN protein expression is reduced in 67 of 236 (28%) breast carcinomas. Recent experimental studies suggested that the cell cycle inhibitor p27Kip1 (p27) is a downstream mediator through which PTEN negatively regulates cell cycle progression.

METHODS

The immunohistochemic expression of p27 and PTEN protein expression was evaluated in a series of 228 invasive ductal carcinomas of the breast.

RESULTS

PTEN protein expression was found to have decreased in 65 of 228 (29%) cases, while the nuclear accumulation of p27 protein was low in 99 of 228 (43%) cases. A reduced PTEN protein expression correlated significantly (P = 0.0214) with a low p27 protein expression. Univariate analysis indicated that the patients demonstrating a combined decrease in PTEN and p27 protein expression have a significantly (P = 0.0044) worse disease-free survival (DFS) than those with other combinations of these two protein expression patterns, while multivariate analysis indicated that the lymph node status, MIB-1 counts, and the combination of PTEN/p27 protein expression (P = 0.0452) are independently significant prognostic factors for DFS.

CONCLUSIONS

A reduced PTEN protein expression correlated significantly with a low p27 protein expression in breast carcinoma. The finding that the patients with a combined decrease in both protein expressions had a poor prognosis thus suggests that a combined loss of PTEN and p27 function is associated with an aggressive phenotype in breast carcinoma.

Proteome profile changes that are differentially regulated by lipid and protein phosphatase activities of tumor suppressor PTEN in PTEN-expressing U-87 MG human glioblastoma cells

The phosphatase and tensin homolog tumor suppressor (PTEN) belongs to a class of "gatekeeper" tumor suppressors together with p53, retinoblastoma and adenomatous polyposis. It is considered one of the most important tumor suppressors in the post p53 era. Previously to identify the molecules involved in the signaling network regulated by PTEN using proteomic tools, we reported global proteome profiles at different time points using the PTEN inducible NIH3T3 cells (Kim, S.-y., Kim, Y. S., Bahk, Y. Y., Mol. Cells 2003, 15, 396-405). However, the system had a critical limitation that NIH3T3 cell has endogenous wild-type PTEN and, thus to be exact, the induced PTEN could not give the answer about the real physiological roles of this tumor suppressor. Here, to find out PTEN-related protein network we have established various PTEN (wild-type, an activity inert C124G, and a lipid phosphatase deficient G129E)-expressing cell clones in U-87 MG human glioblastoma cells lacking detectable PTEN as a result of genetic lesions. In this biological context, we compared their morphological and expression patterns, and proteome images of each PTEN-expressing cell clone by 2-DE followed by identification with MALDI-TOF MS. We obtained some pieces of evidence that morphological change by PTEN expression is mediated by its protein phosphatase activity and their growth rate by the lipid phosphatase activity. The proteomic approaches showed that 30 proteins possibly correlated with PTEN's protein phosphatase activity (13 down-regulated and 17 up-regulated) and 20 with the lipid phosphatase activity (14 down-regulated and 6 up-regulated) were identified. Taken together, we conclude that the comparative analysis of proteome from various PTEN-expressing cells has yielded interpretable data to elucidate the protein network directly and/or indirectly caused by individual phosphatase activities of PTEN in vivo.

Evaluation of two phosphorylation sites improves the prognostic significance of Akt activation in non-small-cell lung cancer tumors

PURPOSE

Akt is a serine/threonine kinase that has been implicated in lung tumorigenesis and lung cancer therapeutic resistance. Full activation of Akt requires two phosphorylation events, but only one site of phosphorylation (S473) has been evaluated thus far in clinical non-small-cell lung cancer (NSCLC) specimens, which has resulted in conflicting results regarding the prognostic significance of Akt activation in NSCLC. In this study, we sought to determine whether evaluation of Akt phosphorylation at T308 would improve prognostic accuracy.

PATIENTS AND METHODS

Phosphospecific antibodies against T308 and S473 were validated and used in an immunohistochemical analysis of tissue microarray slides containing NSCLC specimens (n = 300) and surrounding lung tissue specimens (n = 100).

RESULTS

Phosphorylation of either S473 or T308 was positive in most NSCSLC specimens, but was detected rarely in surrounding normal tissues. When Akt activation was defined by using both sites of phosphorylation, Akt activation was specific for NSCLC tumors versus surrounding tissue (73.4% v 0%; P < .05), was higher in adenocarcinoma than in squamous cell carcinoma (78.1% v 68.5%; P = .040), and was associated with shorter overall survival for all stages of disease (log-rank P = .041). In multivariate analyses, increased phosphorylation of T308 alone was a poor prognostic factor for stage I patients or for tumors < 5 cm (log-rank P = .011 and P = .015, respectively).

CONCLUSION

These results suggest that monitoring phosphorylation of Akt at T308 improves the assessment of Akt activation, and show that Akt activation is a poor prognostic factor for all stages of NSCLC.

Akt phosphorylation associates with LOH of PTEN and leads to chemoresistance for gastric cancer

Growth factor receptor-mediated signal transduction has been implicated in conferring resistance to conventional chemotherapy on cancer cells. We describe a pathway that involves AKT/PI3K to mediate chemoresistance in gastric cancer patients. Primary gastric carcinoma tissues and corresponding normal mucosa were obtained from 76 gastric cancer patients who underwent surgery in the Department of Surgery II in Kyushu University Hospital from the years 1996-2000. AKT activation was investigated by immunostaining with a phosphorylation-specific antibody, and LOH (loss of heterozygosity) of PTEN was studied in the same samples. AKT was phosphorylated in 22 cases (28.9%) of gastric cancer cases. AKT and phosphorylated AKT were not correlated with any clinicopathological factor. We found that the gastric cancer patients who had higher AKT phosphorylation (activated AKT) seemed to have LOH of PTEN (p = 0.0008). When the chemotherapeutic sensibilities of these patients were studied in an MTT assay, it was found that the activated AKT was associated with increased resistance to multiple chemotherapeutic agents (5-fluorouracil, adriamycin, mitomycin C and cis-platinum). The results of our study indicate that AKT activation and LOH of PTEN plays an important role in conferring a broad-spectrum chemoresistance in gastric cancer patients. It also indicates that AKT may therefore be a novel molecular target for therapies or chemosensitivity tests that improve the outcomes of gastric cancer patients.

PTEN expression in clear cell adenocarcinoma of the ovary

OBJECTIVES

In this study, we analyzed the PTEN expression in a large collection of clear cell adenocarcinomas of the ovary. Furthermore, we analyzed the expression of cyclin D1 and p27, and investigated the correlation among all these variables.

METHODS

Totally, 40 clear cell adenocarcinomas were included in this study. The protein expression of PTEN, cyclin D1 and p27 was investigated by immunohistochemistry.

RESULTS

Of 40 clear cell adenocarcinomas, 15 (37.5%) lost all PTEN immunoreactivity. There was no significant correlation between PTEN expression and clinical stage. Cyclin D1 expression and loss of p27 expression were detected in 16/40 (40.0%) and 14/40 (35.0%) clear cell adenocarcinoma cases. There was no significant correlation between PTEN expression and cyclin D1 or p27 protein expression.

CONCLUSIONS

Loss of PTEN expression is relatively common and both cyclin D1 and p27 expressions are not related with PTEN inactivation in clear cell adenocarcinoma of the ovary.

Rapamycin inhibits hTERT telomerase mRNA expression, independent of cell cycle arrest

OBJECTIVES

Rapamycin and its analogues have been shown to be promising as anti-neoplastic agents but have not been extensively studied in gynecologic malignancies. Our goal was to examine the ability of rapamycin to suppress growth and regulate telomerase activity in cervical and ovarian cancer cell lines.

METHODS

Cell proliferation was assessed after exposure to rapamycin. Cell cycle progression was determined by flow cytometry, and apoptosis was evaluated by DNA fragmentation. hTERT mRNA levels were quantified by real-time RT-PCR. Western blot analysis was performed to assess PTEN status, phosphorylated S6 and total S6 expression.

RESULTS

Rapamycin inhibited growth of all the cervical cancer cell lines and 3 of the 4 ovarian cancer cell lines in a dose-dependent manner with IC50 values <50 nM. Loss of PTEN protein expression was seen in only one of the cervical cancer cell lines. Rapamycin induced G1 arrest in those cell lines sensitive to its growth inhibitory effects. In all cell lines, rapamycin rapidly inhibited phosphorylation of S6 and resulted in decreased levels of total S6 protein. Treatment with rapamycin reduced hTERT mRNA expression in both rapamycin-sensitive and -resistant cell lines within 24 h. Thus, the effect of rapamycin on hTERT expression was not dependent on its ability to induce G1 cell cycle arrest.

CONCLUSIONS

Our data suggest that rapamycin may potentially exert its anti-tumor effects through two independent pathways by G1 cell cycle arrest as well as suppression of telomerase activity by inhibition of hTERT mRNA transcription.

Resistance to epidermal growth factor receptor-targeted therapy

The epidermal growth factor receptor (EGFR) has been a major target of molecular anticancer therapy. Two approaches have been developed, involving monoclonal antibodies and receptor tyrosine kinase inhibitors, and both have demonstrated benefit in clinical trials. However, evidence of resistance to these drugs has been described. Cellular levels of EGFR do not always correlate with response to the EGFR tyrosine kinase inhibitors, indicating acquired resistance to these drugs. Since EGFR antagonists interfere with the activation of several intracellular pathways that control cell proliferation, survival, apoptosis, angiogenesis, invasion and metastasis, acquired resistance can occur as a result of several different molecular mechanisms: autocrine/paracrine production of ligand, receptor mutation, constitutive activation of the downstream pathway and activation of alternative pathways. We will describe here potential mechanisms that can cause resistance to EGFR-targeted drugs. Combinations of EGFR antagonists with inhibitors targeting different signaling mechanism(s) - such as insulin-like growth factor receptor and vascular endothelial growth factor receptor - that share the same downstream mediator (e.g., phosphatidylinositol 3-kinase/Akt, mitogen-activated protein kinase), may circumvent or delay the development of resistance to EGFR antagonists resulting in enhanced antitumor activities.

Drug resistance in ovarian cancer: The emerging importance of gene transcription and spatio-temporal regulation of resistance

Resistance to carboplatin plus paclitaxel, one of the most active drug combinations in ovarian cancer, is the major barrier to the successful long-term treatment of this disease. Understanding the mechanisms involved is a first step towards rational strategies to overcome drug resistance and is an area of intense research effort. Recent work has identified several gene families which appear to contribute to the evolution of drug resistance and which are involved in regulating DNA damage, apoptosis and survival signalling. These genes may be co-ordinately regulated as part of a gene expression program that confers drug resistance through multiple pathways. The subcellular localisation of the gene products and their kinetic regulation following exposure to chemotherapeutic agents may also play a part in the development of drug resistance. This provides a more complex paradigm for drug resistance in which the steady-state expression of a single gene may not be predictive of response to therapy. Nevertheless, the identification of critical genes, most relevant to the development of clinical drug resistance, is now feasible through microarray analysis of tumour samples, and strategies aimed at the circumvention of resistance can be developed using these data.

PTEN expression in non-small-cell lung cancer: evaluating its relation to tumor characteristics, allelic loss, and epigenetic alteration

The tumor suppressor PTEN encodes a lipid phosphatase that negatively regulates the phosphatidylinositol 3-kinase/AKT cell survival pathway. Mutations of this gene are common in brain, prostate, endometrial, and gastric cancers but occur rarely in non-small-cell lung cancer (NSCLC), although the PTEN protein is often lost in lung tumors. We have studied hypermethylation of the PTEN promoter, loss of heterozygosity (LOH) at microsatellites in chromosome 10q23 (surrounding and intragenic to the PTEN locus), and hypermethylation of PTEN's highly homologous pseudogene, PTENP1, and their association with PTEN protein loss in a surgical case series study of primary NSCLC. PTEN protein expression was reduced or lost in 74% (86/117) of tumors, with loss occurring more often in well to moderately differentiated tumors. In squamous cell carcinomas, PTEN loss occurred significantly more often in early-stage (stage I or II) disease. PTEN protein loss also occurred more frequently in tumors with low to no aberrant TP53 staining. Methylation of PTEN occurred in 26% (39/151) of tumors, and LOH at 10q23 was rare, occurring in only 19% (17/90) of informative tumors. Neither methylation nor LOH was a significant predictor of PTEN protein expression, although LOH occurred exclusively in early-stage disease. In NSCLC, loss of PTEN protein expression occurs frequently, although the mechanism responsible for loss is not clearly attributable to deletion or epigenetic silencing. PTEN loss may also be a favorable prognostic marker, although further studies are needed to confirm this finding.

Activation of AKT kinases in cancer: implications for therapeutic targeting

The AKT1, AKT2, and AKT3 kinases have emerged as critical mediators of signal transduction pathways downstream of activated tyrosine kinases and phosphatidylinositol 3-kinase. An ever-increasing list of AKT substrates has precisely defined the multiple functions of this kinase family in normal physiology and disease states. Cellular processes regulated by AKT include cell proliferation and survival, cell size and response to nutrient availability, intermediary metabolism, angiogenesis, and tissue invasion. All these processes represent hallmarks of cancer, and a burgeoning literature has defined the importance of AKT alterations in human cancer and experimental models of tumorigenesis, continuing the legacy represented by the original identification of v-Akt as the transforming oncogene of a murine retrovirus. Many oncoproteins and tumor suppressors intersect in the AKT pathway, finely regulating cellular functions at the interface of signal transduction and classical metabolic regulation. This careful balance is altered in human cancer by a variety of activating and inactivating mechanisms that target both AKT and interrelated proteins. Reprogramming of this altered circuitry by pharmacologic modulation of the AKT pathway represents a powerful strategy for rational cancer therapy. In this review, we summarize a large body of data, from many types of cancer, indicating that AKT activation is one of the most common molecular alterations in human malignancy. We also review mechanisms of activation of AKT kinases, examples of therapeutic modulation of the AKT pathway in animal models, and the current status of efforts to target molecular components of the AKT pathway for cancer therapy and, possibly, cancer prevention.

The Akt-mTOR tango and its relevance to cancer

The downstream effector of PI3K, Akt, is frequently hyperactivated in human cancers. A critical downstream effector of Akt, which contributes to tumorigenesis, is mTOR. In the PI3K/Akt/mTOR pathway, Akt is flanked by two tumor suppressors: PTEN, acting as a brake upstream of Akt, and TSC1/TSC2 heterodimer, acting as a brake downstream of Akt and upstream of mTOR. In the absence of the TSC1/TSC2 brake, mTOR activity is unleashed to inhibit Akt via an inhibitory feedback mechanism. Two recent studies used mouse genetics to assess the roles of PTEN and TSC2 in cancer, underscoring the importance of Akt-mTOR interplay for cancer progression and therapy.

Phospho-akt expression is associated with a favorable outcome in non-small cell lung cancer

Akt, a Serine/Threonine protein kinase, mediates growth factor-associated cell survival. Constitutive activation of Akt (phosphorylated Akt, P-Akt) has been observed in several human cancers, including lung cancer and may be associated with poor prognosis and chemotherapy and radiotherapy resistance. The clinical relevance of P-Akt in non-small cell lung cancer (NSCLC) is not well described. In the present study, we examined 82 surgically resected snap-frozen and paraffin-embedded stage I to IIIA NSCLC samples for P-Akt and Akt by Western blotting and for P-Akt by immunohistochemistry. P-Akt protein levels above the median, measured using reproducible semiquantitative band densitometry, correlated with a favorable outcome (P = 0.007). Multivariate analysis identified P-Akt as a significant independent favorable prognostic factor (P = 0.004). Although associated with a favorable prognosis, high P-Akt levels correlated with high tumor grade (P = 0.02). Adenocarcinomas were associated with low P-Akt levels (P = 0.039). Akt was not associated with either outcome or clinicopathologic variables. Cytoplasmic (CP-Akt) and nuclear (NP-Akt) P-Akt tumor cell staining was detected in 96% and 42% of cases, respectively. Both CP-Akt and NP-Akt correlated with well-differentiated tumors (P = 0.008 and 0.017, respectively). NP-Akt also correlated with nodal metastases (P = 0.022) and squamous histology (P = 0.037).These results suggest P-Akt expression is a favorable prognostic factor in NSCLC. Immunolocalization of P-Akt, however, may be relevant as NP-Akt was associated with nodal metastases, a known poor prognostic feature in this disease. P-Akt may be a potential novel therapeutic target for the management of NSCLC.

Reduced Expression of PTEN Protein and Its Prognostic Implications in Invasive Ductal Carcinoma of the Breast

OBJECTIVE

The PTEN tumor suppressor gene has been demonstrated to be inactivated in a variety of human tumors. In breast cancer, the PTEN gene mutation is not commonly found whereas loss of heterozygosity affecting the PTEN locus is frequently found. The aim of this study was to analyze PTEN protein expression in breast cancer and to evaluate the prognostic significance of PTEN protein expression.

METHODS

Paraffin-embedded sections ofinvasive ductal carcinoma of the breast were immunohistochemically stained for PTEN protein expression in 236 breast cancers. The immunohistochemical expression of breast cancer cells was judged to be either normal or reduced compared with the PTEN protein expression of the normal mammary gland.

RESULTS

The expression of PTEN protein was found to have decreased in 67 (28%) of 236 breast cancers. The reduced expression correlated with lymph node metastasis (p = 0.0371), but not with tumor size, nuclear grade, MIB-1 counts or p53 protein expression. Univariate analysis indicated that patients with a reduced PTEN expression had a shorter disease-free survival (DFS) than those with a normal PTEN expression (p = 0.0174). Univariate analyses also determined tumor size, lymph node metastases, nuclear grade, MIB-1 counts, p53 protein as well as PTEN protein expression to be significant factors for DFS, while multivariate analysis determined lymph node metastases and the MIB-1 counts to be independent significant factors for DFS.

CONCLUSIONS

The inactivation of PTEN, demonstrated by a reduced expression of PTEN protein by immunohistochemistry, was found in about one third of all breast cancers. The reduced expression of PTEN protein correlated with lymph node metastases and a worse prognosis in the patients with breast cancer.

Activation of PI3K/Akt pathway by PTEN reduction and PIK3CA mRNA amplification contributes to cisplatin resistance in an ovarian cancer cell line

OBJECTIVE

The aim of this study was to understand the role of PIK3CA and PTEN on the resistance of human ovarian cancer cells to cisplatin-induced apoptosis.

METHODS

Human ovarian cancer cell OVCAR-3 and cisplatin-resistant subclone OVCAR-3/CDDP cells were used for these studies. The expressions of apoptosis regulating proteins and PI3K/Akt signaling proteins were systematically examined.

RESULTS

OVCAR-3/CDDP cells were 4.8-fold more resistant to cisplatin compared to OVCAR-3 cells following 72 h exposure to this drug. This resistance was paralleled with reduced susceptibility to cisplatin-induced apoptosis. Apoptotic proteins were differentially expressed in OVCAR-3/CDDP cells, resulting in the inhibition of Bax translocalization. Cisplatin inhibited Akt phosphorylation and activation in OVCAR-3 cells but not in OVCAR-3/CDDP cells. The specific PI3K inhibitors LY294002 and wortmannin sensitized OVCAR-3/CDDP cells to cisplatin-induced apoptosis and decreased cell viability. A low level of PTEN expression was strongly associated with amplified PIK3CA and PI3K/Akt activities in OVCAR-3/CDDP cells. Small interfering RNA knockdown of PTEN and the expression of active p110alpha resulted in a blockade of apoptosis by cisplatin in OVCAR-3 cells.

CONCLUSIONS

These results collectively indicate that the development of resistance in OVCAR-3 cells was derived by increased PIK3CA transcription and reduction of PTEN expression. These alterations conferred cisplatin resistance to cisplatin through the activation of PI3K/Akt and the inhibition of Bax translocation.

A genetically defined mouse ovarian carcinoma model for the molecular characterization of pathway-targeted therapy and tumor resistance

Cell lines and tumors with defined genetic alterations provide ideal systems in which to test the molecular mechanisms of tumor sensitivity to pathway-targeted therapy. We have generated mouse ovarian epithelial tumor cell lines that contain various combinations of genetic alterations in the p53, c-myc, K-ras and Akt genes. Using both in vitro and in vivo approaches, we investigated the effect of rapamycin on cell proliferation, tumor growth, and the accumulation of peritoneal ascites. We demonstrated that rapamycin effectively inhibits the growth of tumors that rely on Akt signaling for proliferation, whereas tumors in which Akt signaling is not the driving force in proliferation are resistant to rapamycin. The introduction of activated Akt to the rapamycin-resistant cells does not render the cells susceptible to rapamycin if they can use alternative pathways for survival and proliferation. Accordingly, the rapamycin-sensitive tumors develop resistance to rapamycin when presented with alternative survival pathways, such as the mitogen-activated extracellular kinase signaling pathway. The combination of rapamycin and the mitogen-activated extracellular kinase inhibitor PD98059 is required to diminish proliferation in these cell lines. Our results indicate that mammalian target of rapamycin inhibitors may be effective in a subset of tumors that depend on Akt activity for survival but not effective in all tumors that exhibit Akt activation. Tumors with alternative survival pathways may require the inactivation of multiple individual pathways for successful treatment.

PTEN expression in ovine granulosa cells increases during terminal follicular growth

In the present paper, we have studied the expression of the Phosphatase and TENsin homolog deleted on chromosome 10 (PTEN) and its putative biological role in the sheep ovary. We found by Northern-blot, immunohistochemistry and immunoblot that PTEN is highly expressed in granulosa cells from large differentiated follicles (LF) in comparison with small proliferating follicles (SF) (P < 0.001), with no clear effect of follicle quality. Moreover, the PTEN lipid phosphatase activity is also higher in LF than in SF (P < 0.01). In contrast, levels of the phosphorylated form of AKT (pAKT) are lower in LF than in SF (P < 0.0001). IGF-I and insulin but not FSH, LH or forskolin are able to stimulate the expression of PTEN mRNA (P < 0.001) and protein by ovine granulosa cells after 48 h of culture in vitro. An IGF-1 time course analysis showed that expression of PTEN protein appeared after 12h of culture, concomitant with the fall of the pAKT levels, which peaked after 6h of stimulation with IGF-I. Moreover, transfection experiments showed that overexpression of PTEN in ovine granulosa cells induced a decrease and an increase in E2F and p27 promoter activity, respectively (P < 0.05). Overall, our present data show for the first time that the expression of PTEN increases during terminal follicular growth. This increase, that might be induced by IGF-I but not FSH, would participate in the proliferation/differentiation transition of ovine granulosa cells in differentiating follicles.

Heat-shock protein 90 inhibitors as novel cancer chemotherapeutic agents

Heat-shock protein 90 (Hsp90) is a molecular chaperone whose association is required for the stability and function of multiple mutated, chimeric and overexpressed signalling proteins that promote cancer cell growth and/or survival. Hsp90 client proteins include mutated p53, Bcr-Abl, Raf-1, Akt, HER2/Neu (ErbB2) and hypoxia inducible factor-1alpha (HIF-1alpha). Through specific interaction with a single molecular target, Hsp90 inhibitors cause the destabilisation and eventual degradation of Hsp90 client proteins, and they have shown promising antitumour activity in preclinical model systems. One Hsp90 inhibitor, 17-allylamino-geldanamycin (17-AAG), is currently in Phase I clinical trials. Hsp90 inhibitors are unique in that, although they are directed towards a specific molecular target, they simultaneously inhibit multiple signalling pathways on which cancer cells depend for growth and survival. Further, because of the unique effect that Hsp90 inhibition has on cancer cells, combination of an Hsp90 inhibitor with standard chemotherapeutic agents may dramatically increase the in vivo efficacy of the standard agent.

Molecular genetic alterations in endometrioid carcinomas of the ovary: similar frequency of beta-catenin abnormalities but lower rate of microsatellite instability and PTEN alterations than in uterine endometrioid carcinomas

Endometrioid carcinomas of the ovary closely resemble their uterine counterparts. It has been suggested that the former tumors have the same molecular alterations (microsatellite instability [MSI], PTEN, and beta-catenin) described in endometrioid carcinomas of the uterus. We analyzed 55 ovarian carcinomas, including 22 endometrioid, 18 clear cell, and 15 mixed types. MSI was detected in 5 of 39 cases (13%). MLH1 promoter hypermethylation was identified in 2 of the 5 MSI-positive tumors. PTEN was mutated in 5 of 54 cases (9%); of these, 3 had MSI and exhibited frameshift mutations in short-coding mononucleotide repeats. Beta-catenin nuclear expression was detected in 11 of 54 cases (20%) by immunostaining; of these, 7 exhibited CTNNB1 gene mutations. These alterations were found more frequently in endometrioid carcinomas than in tumors of the other 2 groups. Among the former tumors, MSI was detected in 3 of 17 cases (17.5%); PTEN mutations, in 3 of 21 (14%); and beta-catenin, in 8 of 21 (38%). The molecular alterations were found more often in tumors associated with endometriosis than in tumors without endometriosis. Six endometrioid tumors demonstrating matrix metalloproteinase-7 (MMP-7) immunoreactivity with nuclear accumulation of beta-catenin had good outcomes, in contrast to poor outcomes in 7 of 9 predominantly nonendometrioid tumors demonstrating expression of MMP-7 only. We found a similar frequency of beta-catenin abnormalities but lower rates of MSI and PTEN alterations than in uterine endometrioid carcinomas. Alterations in beta-catenin and PTEN genes, as well as MSI, are frequent in low-stage ovarian carcinomas of endometrioid type that have a favorable prognosis.

The major target of the endogenously generated reactive oxygen species in response to insulin stimulation is phosphatase and tensin homolog and not phosphoinositide-3 kinase (PI-3 kinase) in the PI-3 kinase/Akt pathway

Phosphoinositide-3 kinase (PI-3 kinase) and its downstream signaling molecules PDK-1 and Akt were analyzed in SK-N-SH and SK-N-BE(2) human neuroblastoma cell lines. When cells were stimulated with insulin, PI-3 kinase was activated in both cell lines, whereas the translocation of PDK-1 to the membrane fraction and phosphorylated Akt were observed only in SK-N-SH cells. Analyses of the insulin-mediated reactive oxygen species (ROS) generation and Phosphatase and Tensin homolog (PTEN) oxidation indicate that PTEN oxidation occurred in SK-N-SH cells, which can produce ROS, but not in SK-N-BE(2) cells, which cannot increase ROS in response to insulin stimulation. When SK-N-SH cells were pretreated with the NADPH oxidase inhibitor diphenyleneiodonium chloride before insulin stimulation, insulin-mediated translocation of PDK-1 to the membrane fraction and phosphorylation of Akt were remarkably reduced, whereas PI-3 kinase activity was not changed significantly. These results indicate that not only PI-3 kinase activation but also inhibition of PTEN by ROS is needed to increase cellular level of phosphatidylinositol 3,4,5-trisphosphate for recruiting downstream signaling molecules such as PDK-1 and Akt in insulin-mediated signaling. Moreover, the ROS generated by insulin stimulation mainly contributes to the inactivation of PTEN and not to the activation of PI-3 kinase in the PI-3 kinase/Akt pathway.

Antibody-based profiling of the phosphoinositide 3-kinase pathway in clinical prostate cancer

PURPOSE

As kinase inhibitors transition from the laboratory to patients, it is imperative to develop biomarkers that can be used in the clinic. The primary objectives are to identify patients most likely to benefit from molecularly targeted therapies and to document modulation of the drug target. Constitutive activation of the phosphoinositide 3-kinase (PI3K) pathway and its downstream effectors, as a result of PTEN loss or by other mechanisms, occurs in a high proportion of prostate cancers, making it an ideal template for the design of clinical trials involving PI3K pathway inhibitors. Prostate cancers also present unique organ-specific challenges, in that tumors are heterogeneous and diagnostic tissue is extremely limited.

EXPERIMENTAL DESIGN

Working within these limitations, we have developed a set of immunohistochemical assays that define activation of the PI3K pathway in clinical samples.

RESULTS AND CONCLUSIONS

Using both univariate and multivariate analyses, we show that loss of PTEN is highly correlated with the activation of AKT, and this, in turn, is associated with the phosphorylation of S6, one of its main effectors. These three antibodies are potentially able to define a molecular signature of PTEN loss and/or AKT pathway activation in prostate cancer.

The epigenetics of ovarian cancer drug resistance and resensitization

Ovarian cancer is the most lethal of all gynecologic neoplasms. Early-stage malignancy is frequently asymptomatic and difficult to detect and thus, by the time of diagnosis, most women have advanced disease. Most of these patients, although initially responsive, eventually develop and succumb to drug-resistant metastases. The success of typical postsurgical regimens, usually a platinum/taxane combination, is limited by primary tumors being intrinsically refractory to treatment and initially responsive tumors becoming refractory to treatment, due to the emergence of drug-resistant tumor cells. This review highlights a prominent role for epigenetics, particularly aberrant DNA methylation and histone acetylation, in both intrinsic and acquired drug-resistance genetic pathways in ovarian cancer. Administration of therapies that reverse epigenetic "silencing" of tumor suppressors and other genes involved in drug response cascades could prove useful in the management of drug-resistant ovarian cancer patients. In this review, we summarize recent advances in the use of methyltransferase and histone deacetylase inhibitors and possible synergistic combinations of these to achieve maximal tumor suppressor gene re-expression. Moreover, when used in combination with conventional chemotherapeutic agents, epigenetic-based therapies may provide a means to resensitize ovarian tumors to the proven cytotoxic activities of conventional chemotherapeutics.