Too Much of a Good Thing: Suicide Prevention Promotes Chemoresistance in Ovarian Carcinoma

Alterations in mitochondria isolated from peripheral blood mononuclear cells and tumors of patients with epithelial ovarian cancers

Metabolic alterations play an essential role in ovarian carcinogenesis. The flexibility of mitochondrial functions facilitates cellular adaptation to the tough environment associated with carcinogenesis. An understanding of the differences in mitochondrial functions in normal ovaries and cancers could provide a basis for further exploration of future mitochondria-based screening, diagnosis, prognostic prediction, and targeted therapy for epithelial ovarian cancers. The main objective of this study was to assess mitochondrial function profiles measured from PBMCs and ovarian tissues of epithelial ovarian cancers in comparison with normal ovaries. A total of 36 patients were recruited for the study, all of whom underwent primary surgical treatment for malignant epithelial ovarian neoplasm. Of these, 20 patients were in the early stage and 16 patients were in the advanced stage. Additionally, 21 patients who had pelvic surgery for benign gynecologic conditions, with normal ovaries incidentally removed, were recruited as controls. At the time of surgery, a blood sample was collected from each participant for PBMC isolation, and ovarian tissue was retained for molecular studies. These studies included the examination of oxidative stress, mitochondrial mass, mitochondrial respiration, mitochondrial reactive oxygen species (ROS), mitochondrial membrane potential (MMP) changes, and mitochondrial swelling. Clinical and histopathological data were also collected and compared between different stages of epithelial ovarian cancers: early-stage (group 1), advanced-stage (group 2), and normal ovaries (group 3). The levels of cellular oxidative stress, mitochondrial mass, and mitochondrial biogenesis in the peripheral blood mononuclear cells (PBMCs) of participants with ovarian cancer were significantly lower than those of the control group. However, the mitochondrial respiratory parameters measured from the PBMCs were similar across all three groups. Furthermore, mitochondrial membrane depolarization and mitochondrial swelling were observed in ovarian tissues of both early-stage and advanced-stage cancer groups. We demonstrated the dynamic nature of mitochondrial ROS production, biogenesis, and respiratory function in response to epithelial ovarian carcinogenesis. The flexibility of mitochondrial functions under diverse conditions may make it a challenging therapeutic target for ovarian cancer.

Oncogenic cancer/testis antigens: prime candidates for immunotherapy

Recent developments have set the stage for immunotherapy as a supplement to conventional cancer treatment. Consequently, a significant effort is required to further improve efficacy and specificity, particularly the identification of optimal therapeutic targets for clinical testing. Cancer/testis antigens are immunogenic, highly cancer-specific, and frequently expressed in various types of cancer, which make them promising candidate targets for cancer immunotherapy, including cancer vaccination and adoptive T-cell transfer with chimeric T-cell receptors. Our current understanding of tumor immunology and immune escape suggests that targeting oncogenic antigens may be beneficial, meaning that identification of cancer/testis antigens with oncogenic properties is of high priority. Recent work from our lab and others provide evidence that many cancer/testis antigens, in fact, have oncogenic functions, including support of growth, survival and metastasis. This novel insight into the function of cancer/testis antigens has the potential to deliver more effective cancer vaccines. Moreover, immune targeting of oncogenic cancer/testis antigens in combination with conventional cytotoxic therapies or novel immunotherapies such as checkpoint blockade or adoptive transfer, represents a highly synergistic approach with the potential to improve patient survival.

ARID3B increases ovarian tumor burden and is associated with a cancer stem cell gene signature

Ovarian cancer is the most deadly gynecological malignancy since most patients have metastatic disease at the time of diagnosis. Therefore, identification of critical pathways that contribute to ovarian cancer progression is necessary to yield novel therapeutic targets. Recently we reported that the DNA binding protein ARID3B is overexpressed in human ovarian tumors. To determine if ARID3B has oncogenic functions in vivo, ovarian cancer cell lines stably expressing ARID3B were injected intraperitoneally into nude mice. Overexpression of ARID3B increased tumor burden and decreased survival. To assess how ARID3B contributes to the increased tumor growth in vivo, we identified ARID3B induced genes in tumor ascites cells. ARID3B induced expression of genes associated with metastasis and cancer stem cells (CD44, LGR5, PROM1 (CD133), and Notch2). Moreover, ARID3B increased the number of CD133+ (a cancer stem cell marker) cells compared to control cells. The increase in CD133+ cells resulting from ARID3B expression was accompanied by enhanced paclitaxel resistance. Our data demonstrate that ARID3B boosts production CD133+ cells and increases ovarian cancer progression in vivo.

The miR-200 family differentially regulates sensitivity to paclitaxel and carboplatin in human ovarian carcinoma OVCAR-3 and MES-OV cells

We studied the role of miRNA‐200 family members in cellular sensitivity to paclitaxel and carboplatin, using two ovarian cancer cell lines, OVCAR‐3 and MES‐OV, and their paclitaxel resistant variants OVCAR‐3/TP and MES‐OV/TP. Both resistant variants display a strong epithelial‐mesenchymal transition (EMT) phenotype, with marked decreases in expression of miR‐200c and miR‐141 in OVCAR‐3/TP, and down‐regulation of all five members of the miR‐200 family in MES‐OV/TP. Lentiviral transfection of inhibitors of miR‐200c or miR‐141 in parental OVCAR‐3 triggered EMT and rendered the cells resistant to paclitaxel and carboplatin. Conversely, the infection of OVCAR‐3/TP cells with retroviral particles carrying the miR‐200ab429 and 200c141 clusters triggered a partial mesenchymal to epithelial transition (MET). This partial MET was not sufficient to re‐sensitize OVCAR‐3/TP cells to paclitaxel. However, the miR‐200c/miR‐141 cluster transfectants became 6–8x resistant to carboplatin, an unexpected result, whereas miR‐200a/miR‐200b/miR‐429 had no effect. Transfecting the OVCAR‐3/TP GFP cells with specific miRNA mimics confirmed these data. MiR‐200c and miR‐141 mimics conferred resistance to carboplatin in MES‐OV/TP cells, similar to OVCAR‐3/TP, but sensitized MES‐OV to paclitaxel. Several genes involved in balancing oxidative stress were altered in OVCAR‐3/TP 200c141 cells compared to controls. The miR‐200 family plays major, cell‐context dependent roles in regulating EMT and sensitivity to carboplatin and paclitaxel in OVCAR‐3 and MES‐OV cells.

Paclitaxel resistant ovarian cancer cells manifest EMT and decreases in miRNA‐200s.

Inhibition of miRNA‐200c and 141 produces resistance to paclitaxel and carboplatin.

Re‐introducing miRNA‐200s reverts EMT and re‐sensitizes MES‐OV/TP to paclitaxel.

miRNA‐200 family have differential effects on carboplatin resistance.

Plumbagin induces G2/M arrest, apoptosis, and autophagy via p38 MAPK- and PI3K/Akt/mTOR-mediated pathways in human tongue squamous cell carcinoma cells

Plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone; PLB), a naturally occurring naphthoquinone isolated from the roots of Plumbaginaceae plants, has been reported to possess anticancer activities in both in vitro and in vivo studies, but the effect of PLB on tongue squamous cell carcinoma (TSCC) is not fully understood. This study aimed to investigate the effects of PLB on cell cycle distribution, apoptosis, and autophagy, and the underlying mechanisms in the human TSCC cell line SCC25. The results have revealed that PLB exerted potent inducing effects on cell cycle arrest, apoptosis, and autophagy in SCC25 cells. PLB arrested SCC25 cells at the G2/M phase in a concentration- and time-dependent manner with a decrease in the expression level of cell division cycle protein 2 homolog (Cdc2) and cyclin B1 and increase in the expression level of p21 Waf1/Cip1, p27 Kip1, and p53 in SCC25 cells. PLB markedly induced apoptosis and autophagy in SCC25 cells. PLB decreased the expression of the anti-apoptotic proteins B-cell lymphoma 2 (Bcl-2) and B-cell lymphoma-extra large (Bcl-xl) while increasing the expression level of the pro-apoptotic protein Bcl-2-associated X protein (Bax) in SCC25 cells. Furthermore, PLB inhibited phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR), glycogen synthase kinase 3β (GSK3β), and p38 mitogen-activated protein kinase (p38 MAPK) pathways as indicated by the alteration in the ratio of phosphorylation level over total protein expression level, contributing to the autophagy inducing effect. In addition, we found that wortmannin (a PI3K inhibitor) and SB202190 (a selective inhibitor of p38 MAPK) strikingly enhanced PLB-induced autophagy in SCC25 cells, suggesting the involvement of PI3K- and p38 MAPK-mediated signaling pathways. Moreover, PLB induced intracellular reactive oxygen species (ROS) generation and this effect was attenuated by l-glutathione (GSH) and n-acetyl-l-cysteine (NAC). Taken together, these results indicate that PLB promotes cellular apoptosis and autophagy in TSCC cells involving p38 MAPK- and PI3K/Akt/mTOR-mediated pathways with contribution from the GSK3β and ROS-mediated pathways.

Enrichment for chemoresistant ovarian cancer stem cells from human cell lines

Cancer stem cells (CSCs) are defined as a subset of slow cycling and undifferentiated cells that divide asymmetrically to generate highly proliferative, invasive, and chemoresistant tumor cells. Therefore, CSCs are an attractive population of cells to target therapeutically. CSCs are predicted to contribute to a number of types of malignancies including those in the blood, brain, lung, gastrointestinal tract, prostate, and ovary. Isolating and enriching a tumor cell population for CSCs will enable researchers to study the properties, genetics, and therapeutic response of CSCs. We generated a protocol that reproducibly enriches for ovarian cancer CSCs from ovarian cancer cell lines (SKOV3 and OVCA429). Cell lines are treated with 20 µM cisplatin for 3 days. Surviving cells are isolated and cultured in a serum-free stem cell media containing cytokines and growth factors. We demonstrate an enrichment of these purified CSCs by analyzing the isolated cells for known stem cell markers Oct4, Nanog, and Prom1 (CD133) and cell surface expression of CD177 and CD133. The CSCs exhibit increased chemoresistance. This method for isolation of CSCs is a useful tool for studying the role of CSCs in chemoresistance and tumor relapse.

Platelets increase survival of adenocarcinoma cells challenged with anticancer drugs: mechanisms and implications for chemoresistance

BACKGROUND AND PURPOSE

Cancer cells grow without the restraints of feedback control mechanisms, leading to increased cancer cell survival. The treatment of cancer is often complicated by the lack of response to chemotherapy leading to chemoresistance and persistent survival of tumour cells. In this work we studied the role of platelets in chemotherapy-induced cancer cell death and survival.

EXPERIMENTAL APPROACH

Human adenocarcinoma cells, colonic (Caco-2) and ovarian (59 M) cells, were incubated with 5-fluorouracil (1-300 µg·mL(-1) ) or paclitaxel (1-200 µg·mL(-1) ) in the presence or absence of platelets (1.5 × 10(8) mL(-1) ) for 1, 24 or 72 h. Following incubation, cancer cells were harvested and cell survival/death was assayed using flow cytometry, Western blotting, real-time PCR, TaqMan® Gene Expression Assays and proteomics.

KEY RESULTS

Human platelets increased the survival of colonic and ovarian adenocarcinoma cells treated with two standard anticancer drugs, 5-fluorouracil and paclitaxel. In the presence of platelets, cancer cells up-regulated anti-apoptotic and down-regulated pro-apoptotic genes, increased the number of cells in the synthesis of DNA and decreased the number in the quiescent phase, increased expression of cyclins, DNA repair proteins and MAPKs. The analysis of platelet-Caco-2 secretome demonstrated the release of the chemokine RANTES, thrombospondin-1, TGF-β and clusterin. Finally, human recombinant RANTES and thrombospondin-1 improved survival of Caco-2 cells challenged with paclitaxel.

CONCLUSIONS AND IMPLICATIONS

These data demonstrate that platelets increase adenocarcinoma cells survival, proliferation and chemoresistance to standard anticancer drugs. Modulating cancer cell-platelet interactions may offer a new strategy to improve the efficacy of chemotherapy.

High expression of crystallin αB represents an independent molecular marker for unfavourable ovarian cancer patient outcome and impairs TRAIL- and cisplatin-induced apoptosis in human ovarian cancer cells

Dysregulated apoptotic pathways are regarded as major reasons for chemoresistance development as a particular challenge in ovarian cancer therapy. In search of molecular factors affecting human ovarian cancer cell apoptosis and, consequently, patient survival, we examined tumors of 103 platinum-/taxane-treated ovarian cancer patients by mRNA-array hybridization, qPCR, and immunohistochemistry. We identified high expression of crystallin αB (CRYAB), a proposed negative regulator of tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-mediated apoptosis. By Kaplan Meier analysis, this factor turned out to be significantly associated with poor patient outcome [overall survival (OS) p = 0.001, recurrence-free survival (RFS) p = 0.003]. Elevated hazard ratios (HR) were estimated with regard to OS (HR = 2.11, 95% CI 1.10-4.06) and RFS (HR = 1.92, 95% CI 1.07-3.47) in multivariable analyses. These associations were confirmed in independent, publicly available mRNA data comprising 431 patients for OS (p < 0.001) and 413 for RFS (p < 0.001). Our findings were validated by studying apoptotic events in cultured human ovarian cancer cells which were stably transfected to express elevated CRYAB levels. These data emphasized the crucial role of CRYAB in human ovarian cancer biology since TRAIL- as well as cisplatin-induced apoptosis was significantly impaired as a function of enhanced CRYAB expression. Taken together, we identified CRYAB as an independent biomarker for unfavourable outcome of human ovarian cancer patients. Since TRAIL is currently tested as anti-cancer drug and large proportions of the present patient cohort displayed low CRYAB levels in their tumors, CRYAB may enable the selection of patient subgroups benefiting most from TRAIL-containing therapy.

Metabolic approaches to overcoming chemoresistance in ovarian cancer

The poor prognosis in the treatment of ovarian cancer is mainly attributed to chemoresistance. The development of new strategies is urgently necessary to overcome chemoresistance because of the low efficacy of the current standard chemotherapy in ovarian cancer. Metabolic alterations have been suggested to have a crucial role in cancer development. The key metabolic changes in cancer include aerobic glycolysis and macromolecular synthesis, causing antiapoptosis in cancer cells. Therefore, the manipulation of the metabolic derangement could be an effective strategy to overcome chemoresistance in ovarian cancer. In this review, we will discuss metabolic interventions as promising anticancer strategies in ovarian cancer, focusing on the glycolytic, mitochondrial apoptotic, and necrotic pathways. In addition, the role of p53 in relation to metabolic alterations in cancer will be mentioned.