Time to progression is dependent on the expression of the tumour suppressor PTEN in ovarian cancer patients

SPAG6 silencing induces apoptosis in the myelodysplastic syndrome cell line SKM‑1 via the PTEN/PI3K/AKT signaling pathway in vitro and in vivo

Apoptosis is a multi-step mechanism of cell self‑destruction for maintaining cellular homeostatic balance. Accumulating evidence indicates that abnormal apoptosis promotes the evolution and progression of myelodysplastic syndromes (MDS). As a novel cancer-testis antigen, sperm‑associated antigen 6 (SPAG6) has been reported to regulate apoptosis through the tumor necrosis factor-related apoptosis-inducing ligand signaling pathway in the MDS cell line SKM‑1. However, the mechanism of the intrinsic cell death pathway for apoptosis induction by SPAG6 silencing is unclear. In the present study, the in vitro effects of SPAG6 silencing were investigated in SKM‑1 cells through extensive biochemical and molecular approaches. Western blotting and reverse transcription-quantitative polymerase chain reaction were used to detect the expression of SPAG6 and activation of PTEN/PI3K/AKT signal pathway. Additionally, SKM‑1 cells transduced with SPAG6 short hairpin RNA (shRNA) lentivirus were treated with the phosphatidylionositol 3-kinase (PI3K) inhibitor LY294002 or pan caspase inhibitor z‑VAD‑fmk and the apoptosis rates were measured by flow cytometry, and the expressions of associated proteins were examined by western blot analysis. A mouse xenograft model was also used to further evaluate the effects of SPAG6 knockdown on inducing tumor apoptosis in vivo. Lentivirus-mediated knockdown of SPAG6 in SKM‑1 cells increased phosphatase and tensin homolog (PTEN) expression and reduced protein kinase B (AKT) phosphorylation, which in turn resulted in cell apoptosis as evidenced by induced myeloid leukaemia cell differentiation protein Mcl‑1 downregulation, cytochrome c release and increased caspase‑9 expression. Consistently, the PI3K inhibitor LY294002 synergistically enhanced apoptosis of SKM‑1 cells when co-administered with SPAG6 shRNA lentivirus. Furthermore, treatment with the pan caspase inhibitor z‑VAD‑fmk failed to prevent PTEN activation upon SPAG6 knockdown, suggesting that SPAG6-regulated PTEN expression was caspase activation-independent. In addition, SPAG6 knockdown was associated with DNMT1 downregulation, implying that SPAG6 may indirectly control PTEN expression via DNA methylation. Furthermore, tumor tissues from nonobese diabetic/severe combined immunodeficient mice inoculated with SPAG6-shRNA lentivirus pre-infected SKM‑1 cells exhibited significantly elevated apoptosis in the extrinsic and intrinsic pathways. These results demonstrate that SPAG6 silencing induces PTEN expression to regulate apoptosis though the PI3K/AKT pathway, indicating that SPAG6 may be a potential therapeutic target for MDS.

Induction of galectin-1 by TLR-dependent PI3K activation enhances epithelial-mesenchymal transition of metastatic ovarian cancer cells

The expression of different toll-like receptors (TLRs) on tumor cells has been associated with disease aggressiveness, treatment resistance, and poor prognosis. The phosphatidylinositol 3-kinase (PI3K)/AKT pathway is considered critical for cancer cell survival and proliferation. Thus, we investigated the effect of TLR-stimulated PI3K activation on the epithelial-to-mesenchymal transition (EMT) of primary (Caov-3) and metastatic (SK‑OV‑3) epithelial ovarian cancer cell lines in this study. TLR engagement with various ligands promoted the expression of class IA PI3K (p110α, p110β, and p110δ) and increased the expression of mesenchymal markers (N-cadherin, Slug, Vimentin, Snail, α-SMA, and TCF) in SK‑OV‑3 cells. The migratory activity and secretion of EMT-related cytokines of SK‑OV‑3 were significantly higher compared to those of Caov-3 after activation with TLR agonist. Although the invasive capacity and production of EMT-related cytokines of LPS-stimulated SK‑OV‑3 cells were significantly suppressed by all pharmacological inhibitors of the p110 isoform, the Syk/Src-dependent p110β isoform prominently attenuated migration activity. In contrast, the production of IL-10 and galectin-1 was mainly affected by the p110δ isoform. Gene silencing of TLR4 and galectin-1 with siRNA decreased the expression of matrix metalloproteinase-2 (MMP2) and MMP9 and reduced mesenchymal markers in LPS-treated SK‑OV‑3 cells. This study demonstrated that TLR-mediated PI3K activation modulated the invasion and metastasis of ovarian cancer through the production of galectin-1, suggesting that inhibition of the p110 isoform is a promising therapeutic approach against metastatic ovarian cancer.

Phosphatase and Tensin Homolog Is a Potential Target for Ovarian Cancer Sensitization to Cytotoxic Agents

OBJECTIVES

The phosphatase and tensin homolog (PTEN) tumor suppressor protein has been found to be inactivated or mutated in various human malignancies and to play a role in cisplatin and poly(ADP-ribose) polymerase inhibitor sensitivity. In this study, we assessed the association of PTEN loss with homologous recombination (HR) deficiency and increased chemosensitivity.

MATERIALS AND METHODS

The PTEN knockdown models were created using MISSION shRNA lentiviral transduction particles in cell lines derived from normal ovarian surface epithelium and a mixed endometrioid/clear-cell carcinoma. Sensitivity to common therapeutics was assessed using sulforhodamine B assay. Twenty-eight unselected primary epithelial ovarian cancer cultures derived from ascitic fluid collected at the time of surgery and matched genomic DNA were assessed for PTEN mutations using polymerase chain reaction amplification and Sanger sequencing and for mRNA expression using quantitative reverse transcription-polymerase chain reaction; HR was determined using γH2AX/RAD51 assay. The Cancer Genome Atlas data were analyzed using cBioPortal.

RESULTS

In the carcinoma cell line, the PTEN knockdown enhanced sensitivity to cisplatin, rucaparib, doxorubicin, camptothecin, paclitaxel, and irradiation. In the primary ovarian cancer cultures, 2 point mutations were found (1105T>TG, 25L>L in 6 cultures and 1508G>GA, 159R>R in 4 cultures). The PTEN mRNA expression varied over 40-fold between the cultures, but did not correlate with HR status or in vitro sensitivity to cisplatin or rucaparib. The Cancer Genome Atlas data showed a rate of 8% alteration in PTEN and a trend toward improved survival in PTEN-mutated cases.

CONCLUSIONS

These data indicate that although PTEN mutations in ovarian cancer are rare, PTEN inhibition results in therapeutic sensitization. Therefore, PTEN may be an important therapeutic target, in at least some cancers.

Timing of the loss of Pten protein determines disease severity in a mouse model of myeloid malignancy

Juvenile myelomonocytic leukemia (JMML) is an aggressive pediatric mixed myelodysplastic/myeloproliferative neoplasm (MDS/MPN). JMML leukemogenesis is linked to a hyperactivated RAS pathway, with driver mutations in the KRAS, NRAS, NF1, PTPN11, or CBL genes. Previous murine models demonstrated how those genes contributed to the selective hypersensitivity of JMML cells to granulocyte macrophage-colony-stimulating factor (GM-CSF), a unifying characteristic in the disease. However, it is unclear what causes the early death in children with JMML, because transformation to acute leukemia is rare. Here, we demonstrate that loss of Pten (phosphatase and tensin homolog) protein at postnatal day 8 in mice harboring Nf1 haploinsufficiency results in an aggressive MPN with death at a murine prepubertal age of 20 to 35 days (equivalent to an early juvenile age in JMML patients). The death in the mice was due to organ infiltration with monocytes/macrophages. There were elevated activities of protein kinase B (Akt) and mitogen-activated protein kinase (MAPK) in cells at physiological concentrations of GM-CSF. These were more pronounced in mice with Nf1 haploinsufficiency than in littermates with wild-type Nf1,but this model is insufficient to cause cells to be GM-CSF hypersensitive. This new model represents a murine MPN model with features of a pediatric unclassifiable mixed MDS/MPN and mimics many clinical manifestations of JMML in terms of age of onset, aggressiveness, and organ infiltration with monocytes/macrophages. Our data suggest that the timing of the loss of PTEN protein plays a critical role in determining the disease severity in myeloid malignancies. This model may be useful for studying the pathogenesis of pediatric diseases with alterations in the Ras pathway.

The impact of enzastaurin (LY317615.HCl) on CA125 biosynthesis and shedding in ovarian cancer cells

BACKGROUND

In this study the modulatory effect of the proteinase kinase C beta (PKC beta) selective inhibitor enzastaurin on CA125 expression and shedding in ovarian cancer cells (OVCAR-3 cells) was investigated. MATERIAL ANDMETHODS: OVCAR-3 cells were cultured in vitro and treated with increasing concentrations of carboplatin (2-1000 microM), paclitaxel (0.2-100 nM) or enzastaurin (1-100 microM) single agent. Growth inhibitory effects were evaluated by MTS and luminescence assay. CA 125 was determined in supernatans and in cell lysate using an electrochemo-iluminescence immunoassay.

RESULTS

Cell growth of OVCAR-3 cells was inhibited by single agent carboplatin, paclitaxel or enzastaurin in a dose dependent manner. Carboplatin caused a transient increase of CA125 in supernatans followed by a gradual decrease of CA125. Treatment with increasing doses of paclitaxel or enzastaurin caused an increase of CA125 shedding in culture medium but also the membrane bound fraction of CA125 was increased.

CONCLUSION

These results suggest that enzastaurin, as paclitaxel, has a direct stimulatory effect on CA 125 synthesis and shedding in vitro.

Prognostic value and clinicopathological significance of p53 and PTEN in epithelial ovarian cancers

OBJECTIVE

The aim of the study was to evaluate the prognostic significance of p53 and PTEN in patients with epithelial ovarian cancer who were treated with taxane and platinum-based chemotherapy.

METHODS

Retrospectively collected paraffin blocks from 151 epithelial ovarian cancer patients treated with debulking surgery followed by taxane and platinum chemotherapy were analyzed. Expression of p53 and PTEN was assessed by immunohistochemistry. The staining pattern was correlated with clinicopathological variables.

RESULTS

Overexpression of p53 was found in 80 of the 151 cases (53.0%), and it was related to stage, histology and grade. Reduced expression of PTEN was found in 104 of the 151 cases (68.9%), and it was not related to any clinicopathological factors other than age. In survival analysis, stage (p=0.001), residual tumor (p=0.045), lymph node metastases (p=0.012), and PTEN expression (p=0.009) were significant predictors for disease-free survival (DFS). The median DFS of patients with reduced PTEN expression was 20 months (range, 3-71 months), whereas that of patients with normal PTEN expression was 53 months (range, 2-81 months).

CONCLUSIONS

Reduced PTEN expression is a poor prognostic factor for DFS in patients with epithelial ovarian cancer who were treated with debulking surgery and postoperative taxane and platinum chemotherapy.

PTEN promoter methylation and LOH of 10q22-23 locus in PTEN expression of ovarian clear cell adenocarcinomas

OBJECTIVES

Loss of phosphatase and tensin homolog (PTEN) expression is common in ovarian clear cell adenocarcinomas (OCCA), but PTEN mutations are not frequently observed in OCCA. The mechanism of PTEN gene silencing in OCCA is still not clear.

MATERIALS AND METHODS

Immunohistochemical analysis of PTEN expression was performed in 40 OCCA paraffin-embedded tissues. PTEN promoter methylation in 24 OCCA tissues and 5 OCCA cell lines was examined by methylation-specific PCR. Eighteen OCCA patients and 13 serous adenocarcinomas were analyzed for loss of heterozygosity (LOH) at 10q23 with five polymorphic markers.

RESULTS

Of the 40 OCCAs, 37.5% (15/40) had reduced PTEN immunoreactivity, LOH was found in 33% (6/18) of OCCAs, and 31% (4/13) of serous adenocarcinomas. In the 33% of OCCAs with LOH, only 33% (2/6) lost PTEN expression. PTEN promoter was unmethylated in 5 OCCA cell lines and 24 OCCA tissues detected by MSP-PCR. No significant correlation between PTEN expression and advanced stage disease or overall survival was found.

CONCLUSION

Our results indicate that reduced PTEN expression was detected in more than one third of OCCA cases. Neither PTEN promoter methylation nor LOH at 10q23 locus is significantly related to PTEN inactivation and is not an adverse prognostic factor in OCCA.

The ErbB signalling pathway: protein expression and prognostic value in epithelial ovarian cancer

Ovarian cancer is the most frequent cause of death from gynaecological cancer in the Western world. Current prognostic factors do not allow reliable prediction of response to chemotherapy and survival for individual ovarian cancer patients. Epidermal growth factor receptor (EGFR) and HER-2/neu are frequently expressed in ovarian cancer but their prognostic value remains unclear. In this study, we investigated the expression and prognostic value of EGFR, EGFR variant III (EGFRvIII), HER-2/neu and important downstream signalling components in a large series of epithelial ovarian cancer patients. Immunohistochemical staining of EGFR, pEGFR, EGFRvIII, Her-2/neu, PTEN (phosphatase and tensin homologue deleted on chromosome 10), total and phosphorylated AKT (pAKT) and phosphorylated ERK (pERK) was performed in 232 primary tumours using the tissue microarray platform and related to clinicopathological characteristics and survival. In addition, EGFRvIII expression was determined in 45 tumours by RT–PCR. Our results show that negative PTEN immunostaining was associated with stage I/II disease (P=0.006), non-serous tumour type (P=0.042) and in multivariate analysis with a longer progression-free survival (P=0.015). Negative PTEN staining also predicted improved progression-free survival in patients with grade III or undifferentiated serous carcinomas (P=0.011). Positive pAKT staining was associated with advanced-stage disease (P=0.006). Other proteins were expressed only at low levels, and were not associated with any clinicopathological parameter or survival. None of the tumours were positive for EGFRvIII. In conclusion, our results indicate that tumours showing negative PTEN staining could represent a subgroup of ovarian carcinomas with a relatively favourable prognosis.

Reversal of the malignant phenotype of ovarian cancer A2780 cells through transfection with wild-type PTEN gene

OBJECTIVE

PTEN (phosphatase and tensin homologue deleted on chromosome 10) is a tumor suppressor gene identified on human chromosome 10q23. Substantial studies have demonstrated that PTEN can inhibit cell proliferation, migration and invasion of many cancer cells. The purpose of this study was to determine whether upregulation of PTEN gene by transfection wild-type PTEN gene to ovarian cancer cells can inhibit growth and migration and to explore the potential for PTEN gene therapy of ovarian cancers.

METHOD

Wild-type and phosphatase-inactive (C124A) PTEN plasmids were transfected into ovarian epithelial cancer A2780 cells, and their effects on cell apoptosis, cell proliferation, cell migration and cell invasion were analyzed by flow cytometry analysis, TUNEL assay, MTT assay, wound-healing assay and transwell assay.

RESULTS

Both wild-type and mutant PTEN can upregulate the expression of PTEN gene dramatically; however, it is wild-type PTEN not phosphatase-inactive PTEN that can induce apoptosis and decrease cell migration, invasion and proliferation in ovarian cancer cells.

CONCLUSION

These results demonstrated that PTEN had played an important role in the cell proliferation, cell migration and invasion dependent on its phosphatase activity. Enhanced expression of PTEN by gene transfer is sufficient to reverse the malignant phenotype of ovarian cancer cells and transfection of ovarian cancer cells with wild-type PTEN gene might be another novel approach for therapeutic intervention in ovarian cancer.

Ovarian carcinomas with genetic and epigenetic BRCA1 loss have distinct molecular abnormalities

BACKGROUND

Subclassification of ovarian carcinomas can be used to guide treatment and determine prognosis. Germline and somatic mutations, loss of heterozygosity (LOH), and epigenetic events such as promoter hypermethylation can lead to decreased expression of BRCA1/2 in ovarian cancers. The mechanism of BRCA1/2 loss is a potential method of subclassifying high grade serous carcinomas.

METHODS

A consecutive series of 49 ovarian cancers was assessed for mutations status of BRCA1 and BRCA2, LOH at the BRCA1 and BRCA2 loci, methylation of the BRCA1 promoter, BRCA1, BRCA2, PTEN, and PIK3CA transcript levels, PIK3CA gene copy number, and BRCA1, p21, p53, and WT-1 immunohistochemistry.

RESULTS

Eighteen (37%) of the ovarian carcinomas had germline or somatic BRCA1 mutations, or epigenetic loss of BRCA1. All of these tumours were high-grade serous or undifferentiated type. None of the endometrioid (n = 5), clear cell (n = 4), or low grade serous (n = 2) carcinomas showed loss of BRCA1, whereas 47% of the 38 high-grade serous or undifferentiated carcinomas had loss of BRCA1. It was possible to distinguish high grade serous carcinomas with BRCA1 mutations from those with epigenetic BRCA1 loss: tumours with BRCA1 mutations typically had decreased PTEN mRNA levels while those with epigenetic loss of BRCA1 had copy number gain of PIK3CA. Overexpression of p53 with loss of p21 expression occurred significantly more frequently in high grade serous carcinomas with epigenetic loss of BRCA1, compared to high grade serous tumors without loss of BRCA1.

CONCLUSION

High grade serous carcinomas can be subclassified into three groups: BRCA1 loss (genetic), BRCA1 loss (epigenetic), and no BRCA1 loss. Tumors in these groups show distinct molecular alterations involving the PI3K/AKT and p53 pathways.

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.

Role of PI3K and AKT specific isoforms in ovarian cancer cell migration, invasion and proliferation through the p70S6K1 pathway

Ovarian cancer is the leading cause of death from gynecological malignancy for women. The amplification of the PI3K catalytic subunit (p110alpha) and the lost function of PTEN are frequently detected in ovarian cancer cells. PI3K plays an important role in tumorigenesis. To specifically inhibit PI3K activity in ovarian cancer cells, we constructed small interfering RNA (siRNA) against p110alpha. The expression of p110alpha siRNA significantly decreased cell migration, invasion, and proliferation compared to the siSCR control cells. The expression of p110alpha siRNA induced CDK inhibitor p27(KIP1) levels, and decreased levels of cyclin D1, CDK4, and phosphorylated retinoblastoma protein. PI3K transmits the mytogenic signal through AKT. AKT has three isoforms in the cells: AKT1, AKT2 and AKT3. We found that inhibition of AKT1 is sufficient to affect cell migration, invasion, and proliferation. Expression of AKT1 siRNA had a similar effect as p110alpha siRNA in the cells. We showed the roles of specific PI3K and AKT isoforms in the cells, which are important to understanding the mechanism of PI3K/AKT signaling in ovarian cancer cells. Both p110alpha and AKT1 siRNA-expressing cells decreased the activation of p70S6K1. Inhibition of p70S6K1 activity by its siRNA also decreased cell migration, invasion, and proliferation associated with the induction of p27(KIP1) levels, and with the inhibition of cell cycle-associated proteins including cyclin D1, CDK2, and phosphorylated retinoblastoma protein. This study demonstrates the important role of the PI3K/AKT/mTOR/p70S6K1 pathway in cell proliferation, migration, and invasion in ovarian cancer cells by using siRNA-mediated gene silencing as a reverse genetic method.

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.

RRM1 and PTEN as prognostic parameters for overall and disease-free survival in patients with non-small-cell lung cancer

PURPOSE

RRM1 has important functions in the determination of the malignant phenotype. It controls cell proliferation through deoxynucleotide production and metastatic propensity through PTEN induction. It is located in a region of loss of heterozygosity in non-small-cell lung cancer (NSCLC), which is a predictor of poor survival. We hypothesized that RRM1 expression would be a significant predictor of outcome in NSCLC.

PATIENTS AND METHODS

A retrospective data set of 49 patients and a prospective data set of 77 patients with resectable NSCLC were studied. RNA was extracted from tumor and normal lung tissue, and expression of the genes RRM1, PTEN, and RRM2 was determined by real-time quantitative polymerase chain reaction.

RESULTS

RRM1 expression was significantly correlated with PTEN and RRM2 expression in tumor tissue. RRM1 and PTEN expression in tumor tissue was highly predictive of overall (P =.011 and.018, respectively) and disease-free survival (P =.002 and.026, respectively). Patients with high levels of expression lived longer and had disease recurrence later than patients with low levels of RRM1 and PTEN. In a multivariate analysis, high RRM1 expression was predictive of long survival independent of tumor stage, performance status, and weight loss.

CONCLUSION

RRM1 is a biologically and clinically important determinant of malignant behavior in NSCLC. Knowing the level of expression of this gene adds significant information to management decisions independent of the currently used outcome predictors of tumor stage, performance status, and weight loss. Future clinical trials should stratify patients based on expression of this gene to avoid unwanted biases.