Targeting Signaling Pathways in Epithelial Ovarian Cancer

Ovarian carcinoma (OC) is the most lethal gynecological malignancy. Response to platinum-based chemotherapy is poor in some patients and, thus, current research is focusing on new therapy options. The various histological types of OC are characterized by distinctive molecular genetic alterations that are relevant for ovarian tumorigenesis. The understanding of these molecular pathways is essential for the development of novel therapeutic strategies.

Purpose

We want to give an overview on the molecular genetic changes of the histopathological types of OC and their role as putative therapeutic targets.

In Depth Review of Existing Data

In 2012, the vascular endothelial growth factor (VEGF) inhibitor, bevacizumab, was approved for OC treatment. Bevacizumab has shown promising results as single agent and in combination with conventional chemotherapy, but its target is not distinctive when analyzed before treatment. At present, mammalian target of rapamycin (mTOR) inhibitors, poly-ADP-ribose polymerase (PARP) inhibitors and components of the EGFR pathway are in the focus of clinical research. Interestingly, some phytochemical substances show good synergistic effects when used in combination with chemotherapy.

Conclusion

Ongoing studies of targeted agents in conjunction with chemotherapy will show whether there are alternative options to bevacizumab available for OC patients. Novel targets which can be assessed before therapy to predict efficacy are needed. The assessment of therapeutic targets is continuously improved by molecular pathological analyses on tumor tissue. A careful selection of patients for personalized treatment will help to reduce putative side effects and toxicity.     

The Interaction of Adrenomedullin and Macrophages Induces Ovarian Cancer Cell Migration via Activation of RhoA Signaling Pathway

Tumor-associated macrophages (TAMs) are correlated with poor prognosis in many human cancers; however, the mechanism by which TAMs facilitate ovarian cancer cell migration and invasion remains unknown. This study was aimed to examine the function of adrenomedullin (ADM) in macrophage polarization and their further effects on the migration of ovarian cancer cells. Exogenous ADM antagonist and small interfering RNA (siRNA) specific for ADM expression were treated to macrophages and EOC cell line HO8910, respectively. Then macrophages were cocultured with HO8910 cells without direct contact. Flow cytometry, Western blot and real-time PCR were used to detect macrophage phenotype and cytokine production. The migration ability and cytoskeleton rearrangement of ovarian cancer cells were determined by Transwell migration assay and phalloidin staining. Western blot was performed to evaluate the activity status of signaling molecules in the process of ovarian cancer cell migration. The results showed that ADM induced macrophage phenotype and cytokine production similar to TAMs. Macrophages polarized by ADM promoted the migration and cytoskeleton rearrangement of HO8910 cells. The expression of RhoA and its downstream effector, cofilin, were upregulated in macrophage-induced migration of HO8910 cells. In conclusion, ADM could polarize macrophages similar to TAMs, and then polarized macrophages promote the migration of ovarian cancer cells via activation of RhoA signaling pathway in vitro.     

Nonylphenol Induces Apoptosis through ROS/JNK Signaling in a Spermatogonia Cell Line

Nonylphenol (NP) is an endocrine-disruptor chemical that negatively affects reproductive health. Testes exposure to NP results in testicular structure disruption and a reduction in testicular size and testosterone levels. However, the effects of NP on spermatogonia in testes have not been fully elucidated. In this study, the molecular mechanisms of NP in GC-1 spermatogonia (spg) cells were investigated. We found that cell viability significantly decreased and apoptosis increased in a dose-dependent manner when GC-1 spg cells were exposed to NP. Furthermore, the expression levels of the pro-apoptotic proteins increased, whereas anti-apoptosis markers decreased in NP-exposed GC-1 spg cells. We also found that NP increased reactive oxygen species (ROS) generation, suggesting that ROS-induced activation of the MAPK signaling pathway is the molecular mechanism of NP-induced apoptosis in GC-1 spg cells. Thus, NP could induce c-Jun phosphorylation; dose-dependent expression of JNK, MKK4, p53, and p38; and the subsequent inhibition of ERK1/2 and MEK1/2 phosphorylation. The genes involved in apoptosis and JNK signaling were also upregulated in GC-1 spg cells treated with NP compared to those in the controls. Our findings suggest that NP induces apoptosis through ROS/JNK signaling in GC-1 spg cells.     

CXC Chemokine Signaling in Progression of Epithelial Ovarian Cancer: Theranostic Perspectives

Patients with epithelial ovarian cancer (EOC) are often diagnosed at an advanced stage due to nonspecific symptoms and ineffective screening approaches. Although chemotherapy has been available and widely used for the treatment of advanced EOC, the overall prognosis remains dismal. As part of the intrinsic defense mechanisms against cancer development and progression, immune cells are recruited into the tumor microenvironment (TME), and this process is directed by the interactions between different chemokines and their receptors. In this review, the functional significance of CXC chemokine ligands/chemokine receptors (CXCL/CXCR) and their roles in modulating EOC progression are summarized. The status and prospects of CXCR/CXCL-based theranostic strategies in EOC management are also discussed.     

Arsenic Trioxide Inhibits Cell Growth and Induces Apoptosis through Inactivation of Notch Signaling Pathway in Breast Cancer

Arsenic trioxide has been reported to inhibit cell growth and induce apoptotic cell death in many human cancer cells including breast cancer. However, the precise molecular mechanisms underlying the anti-tumor activity of arsenic trioxide are still largely unknown. In the present study, we assessed the effects of arsenic trioxide on cell viability and apoptosis in breast cancer cells. For mechanistic studies, we used multiple cellular and molecular approaches such as MTT assay, apoptosis ELISA assay, gene transfection, RT-PCR, Western blotting, and invasion assays. For the first time, we found a significant reduction in cell viability in arsenic trioxide-treated cells in a dose-dependent manner, which was consistent with induction of apoptosis and also associated with down-regulation of Notch-1 and its target genes. Taken together, our findings provide evidence showing that the down-regulation of Notch-1 by arsenic trioxide could be an effective approach, to cause down-regulation of Bcl-2, and NF-κB, resulting in the inhibition of cell growth and invasion as well as induction of apoptosis. These results suggest that the anti-tumor activity of arsenic trioxide is in part mediated through a novel mechanism involving inactivation of Notch-1 and its target genes. We also suggest that arsenic trioxide could be further developed as a potential therapeutic agent for the treatment of breast cancer.     

Guidance of Signaling Activations by Cadherins and Integrins in Epithelial Ovarian Cancer Cells

Epithelial ovarian cancer (EOC) is the deadliest tumor among gynecological cancer in the industrialized countries. The EOC incidence and mortality have remained unchanged over the last 30 years, despite the progress in diagnosis and treatment. In order to develop novel and more effective therapeutic approaches, the molecular mechanisms involved in EOC progression have been thoroughly investigated in the last few decades. At the late stage, peritoneal metastases originate from the attachment of small clusters of cancer cells that shed from the primary site and carried by the ascites adhere to the abdominal peritoneum or omentum. This behavior suggests that cell–cell or cell–matrix adhesion mechanisms regulate EOC growth and dissemination. Complex downstream signalings, which might be influenced by functional cross-talk between adhesion molecules and co-expressed and activated signaling proteins, can affect the proliferation/survival and the migration/invasion of EOC cells. This review aimed to define the impact of the mechanisms of cell–cell, through cadherins, and cell–extracellular matrix adhesion, through integrins, on the signaling cascades induced by membrane receptors and cytoplasmic proteins known to have a role in the proliferation, migration and invasion of EOC cells. Finally, some novel approaches using peptidomimetic ligands to cadherin and integrins are summarized.     

Inhibition of BMI-1 Induces Apoptosis through Downregulation of DUB3-Mediated Mcl-1 Stabilization

BMI-1, a polycomb ring finger oncogene, is highly expressed in multiple cancer cells and is involved in cancer cell proliferation, invasion, and apoptosis. BMI-1 represents a cancer stemness marker that is associated with the regulation of stem cell self-renewal. In this study, pharmacological inhibition (PTC596) or knockdown (siRNA) of BMI-1 reduced cancer stem-like cells and enhanced cancer cell death. Mechanistically, the inhibition of BMI-1 induced the downregulation of Mcl-1 protein, but not Mcl-1 mRNA. PTC596 downregulated Mcl-1 protein expression at the post-translational level through the proteasome-ubiquitin system. PTC596 and BMI-1 siRNA induced downregulation of DUB3 deubiquitinase, which was strongly linked to Mcl-1 destabilization. Furthermore, overexpression of Mcl-1 or DUB3 inhibited apoptosis by PTC596. Taken together, our findings reveal that the inhibition of BMI-1 induces Mcl-1 destabilization through downregulation of DUB3, resulting in the induction of cancer cell death.     

Methylmercury Induces Mitochondria- and Endoplasmic Reticulum Stress-Dependent Pancreatic β-Cell Apoptosis via an Oxidative Stress-Mediated JNK Signaling Pathway

Methylmercury (MeHg), a long-lasting organic pollutant, is known to induce cytotoxic effects in mammalian cells. Epidemiological studies have suggested that environmental exposure to MeHg is linked to the development of diabetes mellitus (DM). The exact molecular mechanism of MeHg-induced pancreatic β-cell cytotoxicity is still unclear. Here, we found that MeHg (1-4 μM) significantly decreased insulin secretion and cell viability in pancreatic β-cell-derived RIN-m5F cells. A concomitant elevation of mitochondrial-dependent apoptotic events was observed, including decreased mitochondrial membrane potential and increased proapoptotic (Bax, Bak, p53)/antiapoptotic (Bcl-2) mRNA ratio, cytochrome c release, annexin V-Cy3 binding, caspase-3 activity, and caspase-3/-7/-9 activation. Exposure of RIN-m5F cells to MeHg (2 μM) also induced protein expression of endoplasmic reticulum (ER) stress-related signaling molecules, including C/EBP homologous protein (CHOP), X-box binding protein (XBP-1), and caspase-12. Pretreatment with 4-phenylbutyric acid (4-PBA; an ER stress inhibitor) and specific siRNAs for CHOP and XBP-1 significantly inhibited their expression and caspase-3/-12 activation in MeHg-exposed RIN-mF cells. MeHg could also evoke c-Jun N-terminal kinase (JNK) activation and reactive oxygen species (ROS) generation. Antioxidant N-acetylcysteine (NAC; 1mM) or 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox; 100 μM) markedly prevented MeH-induced ROS generation and decreased cell viability in RIN-m5F cells. Furthermore, pretreatment of cells with SP600125 (JNK inhibitor; 10 μM) or NAC (1 mM) or transfection with JNK-specific siRNA obviously attenuated the MeHg-induced JNK phosphorylation, CHOP and XBP-1 protein expression, apoptotic events, and insulin secretion dysfunction. NAC significantly inhibited MeHg-activated JNK signaling, but SP600125 could not effectively reduce MeHg-induced ROS generation. Collectively, these findings demonstrate that the induction of ROS-activated JNK signaling is a crucial mechanism underlying MeHg-induced mitochondria- and ER stress-dependent apoptosis, ultimately leading to β-cell death.     

Androgen/Androgen Receptor Signaling in Ovarian Cancer: Molecular Regulation and Therapeutic Potentials

Ovarian cancer (OVCA) arises from three cellular origins, namely surface epithelial cells, germ cells, and stromal cells. More than 85% of OVCAs are EOCs (epithelial ovarian carcinomas), which are the most lethal gynecological malignancies. Cancer stem/progenitor cells (CSPCs) are considered to be cancer promoters due to their capacity for unlimited self-renewal and drug resistance. Androgen receptor (AR) belongs to the nuclear receptor superfamily and can be activated through binding to its ligand androgens. Studies have reported an association between AR expression and EOC carcinogenesis, and AR is suggested to be involved in proliferation, migration/invasion, and stemness. In addition, alternative AR activating signals, including both ligand-dependent and ligand-independent, are involved in OVCA progression. Although some clinical trials have previously been conducted to evaluate the effects of anti-androgens in EOC, no significant results have been reported. In contrast, experimental studies evaluating the effects of anti-androgen or anti-AR reagents in AR-expressing EOC models have demonstrated positive results for suppressing disease progression. Since AR is involved in complex signaling pathways and may be expressed at various levels in OVCA, the aim of this article was to provide an overview of current studies and perspectives regarding the relevance of androgen/AR roles in OVCA.     

The Novel Benzothiazole Derivative PB11 Induces Apoptosis via the PI3K/AKT Signaling Pathway in Human Cancer Cell Lines

Among several anti-cancer therapies, chemotherapy can be used regardless of the stage of the disease. However, development of anti-cancer agents from potential chemicals must be executed very cautiously because of several problems, such as safety, drug resistance, and continuous administration. Most chemotherapeutics selectively cause cancer cells to undergo apoptosis. In this study, we tested the effects of a novel chemical, the benzothiazole derivative N-[2-[(3,5-dimethyl-1,2-oxazol-4-yl)methylsulfanyl]-1,3-benzothiazol-6-yl]-4-oxocyclohexane-1-carboxamide (PB11) on the human cell lines U87 (glioblastoma), and HeLa (cervix cancer). It was observed that this chemical was highly cytotoxic for these cells (IC50s < 50 nM). In addition, even 40 nM PB11 induced the classical apoptotic symptoms of DNA fragmentation and nuclear condensation. The increase of caspase-3 and -9 activities also indicated an increased rate of apoptosis, which was further confirmed via Western blotting analysis of apoptosis-associated proteins. Accordingly, PB11 treatment up-regulated the cellular levels of caspase-3 and cytochrome-c, whereas it down-regulated PI3K and AKT. These results suggest that PB11 induces cytotoxicity and apoptosis in cancer cells by suppressing the PI3K/AKT signaling pathways and, thus, may serve as an anti-cancer therapeutic.     

CD26 Induces Colorectal Cancer Angiogenesis and Metastasis through CAV1/MMP1 Signaling

CD26 has been reported as a marker for colorectal cancer stem cells endowed with tumor-initiating properties and capable of colorectal cancer (CRC) metastasis. In this study, we investigated the functional effect of CD26 on CRC angiogenesis and metastasis, and the potential underlying mechanism. The functional effects of CD26 overexpression or repression were determined by a wound healing experiment, and cell migration and invasion assays in vitro and in mouse models. Differentially expressed genes regulated by CD26 were identified by genome-wide mRNA expression array and validated by quantitative PCR. CD26 functionally regulated CRC cell migration and invasion in vitro and angiogenesis and metastasis in vivo. Genome-wide mRNA expression array and qPCR showed that MMP1 was up-regulated in CD26+ subpopulation, and a subsequent experiment demonstrated the regulatory effect of CD26 on MMP1 in CRC cell lines with CD26 repression or overexpression. Furthermore, overexpression of CAV1 abrogated the CD26-regulated MMP1 induction in CRC cell lines. This study demonstrated the functional roles of CD26 in inducing CRC migration, invasion, angiogenesis and metastasis and identified the potential involvement of MMP1 and CAV1 in such process. CD26 is an attractive therapeutic target for combating tumor progression to improve the prognosis of CRC patients.     

Novel Nitrogen-Based Chalcone Analogs Provoke Substantial Apoptosis in HER2-Positive Human Breast Cancer Cells via JNK and ERK1/ERK2 Signaling Pathways

Natural chalcones possess antitumor properties and play a role as inducers of apoptosis, antioxidants and cytotoxic compounds. We recently reported that novel nitrogen chalcone-based compounds, which were generated in our lab, have specific effects on triple-negative breast cancer cells. However, the outcome of these two new compounds on human epidermal growth factor receptor 2 (HER2)-positive breast cancer remains nascent. Thus, we herein investigated the effects of these compounds (DK-13 and DK-14) on two HER2-positive breast cancer cell lines, SKBR3 and ZR75. Our data revealed that these compounds inhibit cell proliferation, deregulate cell-cycle progression and significantly induce cell apoptosis in both cell lines. Furthermore, the two chalcone compounds cause a significant reduction in the cell invasion ability of SKBR3 and ZR75 cancer cells. In parallel, we found that DK-13 and DK-14 inhibit colony formation of both cell lines in comparison to their matched controls. On the other hand, we noticed that these two compounds can inhibit angiogenesis in the chorioallantoic membrane model. The molecular pathway analysis of chalcone compounds exposed cells revealed that these compounds inhibit the expression of both JNK1/2/3 and ERK1/2, the major plausible molecular pathways behind these events. Our findings implicate that DK-13 and DK-14 possess effective chemotherapeutic outcomes against HER2-positive breast cancer via the ERK1/2 and JNK1/2/3 signaling pathways.     

Coprinopsis cinerea Galectin CGL1 Induces Apoptosis and Inhibits Tumor Growth in Colorectal Cancer Cells

Mushroom galectins are promising anticancer agents for their low IC₅₀ values against cancer cells in vitro. In this study, two Coprinopsis cinerea galectins, CGL1 and CGL2, were heterologously expressed, and their biochemistry properties and anticancer effects were evaluated. The purified galectins were thermostable at neutral pH conditions. They both existed as tetramers and shared a high affinity towards lactose. CGL1 and CGL2 strongly inhibited the cell viability of many cancer cell lines, including three colorectal cancer cells, in a dose-dependent manner by inducing mitochondria-mediated caspase-dependent apoptosis. Furthermore, CGL1 exhibited higher apoptosis-inducing ability and cytotoxicity than CGL2. In vivo cell viability experiments based on two xenograft mouse models showed that CGL1 had a more substantial inhibitory effect than CGL2 on HCT116 tumor growth (p < 0.0001), whereas only CGL1 inhibited DLD1 tumor growth (p < 0.01). This is the first study to evaluate the anti-colorectal cancer effect of mushroom lectins in vivo, and our results showed that CGL1 is a potent agent for colorectal cancer treatment.     

Curcumin Induces Apoptosis of Chemoresistant Lung Cancer Cells via ROS-Regulated p38 MAPK Phosphorylation

This study aimed to challenge chemoresistance by curcumin (CUR) with drug-selected human lung cancer A549 sublines that continuously proliferate in the present of docetaxel (DOC) and vincristine (VCR). Their sensitivities to CUR were measured by MTT assay and the particular intracellular reactive oxygen species (ROS) was detected by fluorescence activated cell sorting (FACS) analysis. Apoptosis was analyzed by Annexin V assay of the flow cytometry. Inhibitors and RNA interference were used to examine the signaling pathway regulated by the kinases. The obtained data demonstrated that CUR induces chemoresistant cell apoptosis by generating ROS and application of N-acetylcysteine (NAC) blocks ROS production, resulting in apoptosis suppression. Phosphorylation of extracellular regulated kinase (ERK), p38 MAPK, and eIF-2α were increased but c-Jun N-terminal kinase (JNK) did not increase when chemoresistant cells were treated with CUR. Downregulation of ERK and p38 MAPK phosphorylation by their inhibitors had no effect on CUR-induced apoptosis. Interestingly, the knockdown of p38 MAPK with shRNA significantly reduced CUR-induced apoptosis on the chemoresistant sublines. Phosphorylation of the eIF-2α protein was inhibited when p38 MAPK was knocked down in DOC-resistant A549 cells, but a high level of phosphorylated eIF-2α protein remained on the VCR-resistant A549 cells when p38 MAPK was knocked down. These data confirmed that CUR-augmented ROS potently induced apoptosis via upregulated p38 MAPK phosphorylation. Therefore, activated p38 MAPK is considered a pro-apoptotic signal for CUR-induced apoptosis of chemoresistant human lung cancer cells.     

Trace Amine-Associated Receptor 1 (TAAR1) Is a Positive Prognosticator for Epithelial Ovarian Cancer

Trace amine-associated receptor 1 (TAAR1) is a G_αs- protein coupled receptor that plays an important role in the regulation of the immune system and neurotransmission in the CNS. In ovarian cancer cell lines, stimulation of TAAR1 via 3-iodothyronamine (T₁AM) reduces cell viability and induces cell death and DNA damage. Aim of this study was to evaluate the prognostic value of TAAR1 on overall survival of ovarian carcinoma patients and the correlation of TAAR1 expression with clinical parameters. Ovarian cancer tissue of n = 156 patients who were diagnosed with epithelial ovarian cancer (serous, n = 110 (high-grade, n = 80; low-grade, n = 24; unknown, n = 6); clear cell, n = 12; endometrioid, n = 21; mucinous, n = 13), and who underwent surgery at the Department of Obstetrics and Gynecology, University Hospital of the Ludwig-Maximilians University Munich, Germany between 1990 and 2002, were analyzed. The tissue was stained immunohistochemically with anti-TAAR1 and evaluated with the semiquantitative immunoreactive score (IRS). TAAR1 expression was correlated with grading, FIGO and TNM-classification, and analyzed via the Spearman’s rank correlation coefficient. Further statistical analysis was obtained using nonparametric Kruskal-Wallis rank-sum test and Mann-Whitney-U-test. This study shows that high TAAR1 expression is a positive prognosticator for overall survival in ovarian cancer patients and is significantly enhanced in low-grade serous carcinomas compared to high-grade serous carcinomas. The influence of TAAR1 as a positive prognosticator on overall survival indicates a potential prognostic relevance of signal transduction of thyroid hormone derivatives in epithelial ovarian cancer. Further studies are required to evaluate TAAR1 and its role in the development of ovarian cancer.     

Arylquin 1 (Potent Par-4 Secretagogue) Inhibits Tumor Progression and Induces Apoptosis in Colon Cancer Cells

Colorectal cancer (CRC) is one of the most common gastrointestinal cancers worldwide. Current therapeutic strategies mainly involve surgery and chemoradiotherapy; however, novel antitumor compounds are needed to avoid drug resistance in CRC, as well as the severe side effects of current treatments. In this study, we investigated the anticancer effects and underlying mechanisms of Arylquin 1 in CRC. The MTT assay was used to detect the viability of SW620 and HCT116 cancer cells treated with Arylquin 1 in a dose-dependent manner in vitro. Further, wound-healing and transwell migration assays were used to evaluate the migration and invasion abilities of cultured cells, and Annexin V was used to detect apoptotic cells. Additionally, Western blot was used to identify the expression levels of N-cadherin, caspase-3, cyclin D1, p-extracellular signal-regulated kinase (ERK), p-c-JUN N-terminal kinase (JNK), and phospho-p38, related to key signaling proteins, after administration of Arylquin 1. Xenograft experiments further confirmed the effects of Arylquin 1 on CRC cells in vivo. Arylquin 1 exhibited a dose-dependent reduction in cell viability in cultured CRC cells. It also inhibited cell proliferation, migration, and invasion, and induced apoptosis. Mechanistic analysis demonstrated that Arylquin 1 increased phosphorylation levels of ERK, JNK, and p38. In a mouse xenograft model, Arylquin 1 treatment diminished the growth of colon tumors after injection of cultured cancer cells. Arylquin 1 may have potential anticancer effects and translational significance in the treatment of CRC.     

Artesunate Induces Apoptosis of Bladder Cancer Cells by miR-16 Regulation of COX-2 Expression

Bladder cancer is the most common malignant tumor of the urinary tract and remains one of the major causes of cancer death worldwide. In this study, we investigated the effect and mechanism of Artesunate (ART), a traditional Chinese medicine, on inducing apoptosis of human bladder cancer cells. In vivo antitumor activity was investigated in bladder cancer in rat by subcutaneous injection of different concentration of ART. The effect of ART on growth inhibition and apoptosis of bladder cancer cells was evaluated using dimethylthiazoly-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry analysis, respectively. Cyclooxygenase-2 (COX-2) and miR-16 expression levels were determined with real-time PCR. The concentrations of prostaglandin E2 (PGE2) in the supernatants of bladder cancer cells were measured with an ELISA kit. The miR-16 inhibitor or mimic were transfected into cells to up- or down-regulate miR-16 expression. ART efficiently inhibited orthotopic tumor growth in the bladder cancer rat, which is accompanied with an increase of miR-16 expression and a decrease of COX-2 expression. In vitro, ART could induce cytotoxicity and apoptosis in bladder cancer cells, but presented a much lighter toxicity effect against normal human urothelial cells. ART significantly increased miR-16 expression and decreased the expression of COX-2 and the production of PGE2. More importantly, down-regulation of miR-16 expression could reverse the effect of ART on apoptosis and COX-2 expression in bladder cells. Moreover, exogenous PGE2 could inhibit apoptosis of bladder cancer cells treated with ART. In conclusion, ART can elicit an anti-tumor effect against bladder cancer by up-regulation of miR-16 expression, which resulted in the decrease of COX-2 expression and PGE2 production. Hence, ART might be an effective drug for the treatment of bladder cancer.     

Combination of Fenretinide and Selenite Inhibits Proliferation and Induces Apoptosis in Ovarian Cancer Cells

The combination of fenretinide and selenite on ovarian cancer cells was investigated to assess its effects on proliferation and ability to induce apoptosis. Our results showed that fenretinide and selenite in combination significantly suppress the proliferation of ovarian cancer cells and induced apoptosis (including reactive oxygen species generation, and the loss of mitochondrial membrane potential) compared with either drug used alone. The caspase3/9-dependent pathway was triggered significantly in combination treatment, and moreover, the AMPK pathway also mediated the apoptosis induction in fenretinide and selenite combination. Fenretinide and selenite combination treatment was demonstrated to suppress tumor growth in vivo, this drug combination has been thus found to have an enhanced anti-tumor effect on ovarian cancers cells.