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Objectives Ovarian cancer stem-like cells (CSCs), which can form non-adherent sphere cells in a stem-cell selection culture system, exhibit stemness and drug resistance to chemotherapeutics, which are properties not observed in differentiated cells. Recent studies have demonstrated that Kruppel-like factor 5 (KLF5) is involved in cell proliferation and mediates cell survival and tumourigenesis. Here, we investigated the role of KLF5 and its downstream target survivin, in strengthening drug resistance of ovarian CSCs. Materials and methods Ovarian cancer cell line SKOV3 was cultured under serum-free conditions and differentiating conditions to promote formation of sphere cells and differentiated cells, respectively. siRNA-KLF5 was used to knock down KLF5, and survivin expression vector was used to overexpress survivin. Cells were further analysed by qPCR, immunofluorescence staining and western blotting. Chromatin immunoprecipitation (ChIP) assay and electrophoretic mobility shift assay (EMSA) were performed to investigate the relationship between KLF5 and survivin expression. Drug resistance was examined by MTT and apoptosis assays. Results KLF5 was highly expressed in the ovarian cancer cell line SKOV3 sphere cells, accompanied by elevated survivin expression. Silencing KLF5 by small interfering RNA in sphere cells down-regulated survivin expression, which also sensitized the sphere cells to apoptosis induced by chemotherapeutic drugs (cisplatin or paclitaxel). Furthermore, ChIP assay, survivin overexpression and EMSA results indicated that KLF5 controlled survivin expression by directly binding the surivin promoter in the cells. Conclusions The KLF5-mediated signalling pathway is a potential target for elimination of ovarian CSCs.

Naïve and primed embryonic stem cells (ESCs) represent 2 pluripotent states of mouse embryonic stem cells (mESCs), corresponding to the pre- and postimplantation cells, respectively, in vivo. Primed ESCs are distinct from naïve cells in biological characteristics, genetic features, developing potentials, and antagonistic signal pathway dependences to support undifferentiated growth. In vitro, naïve mESCs are readily converted to primed cells upon transferring to primed pluripotency signaling. ESC-derived epiblast stem cells (ESD-EpiSCs) are stabilized primed cells derived from naïve mESCs in vitro, and cannot be maintained with leukemia inhibitory factor (LIF) signaling with or without mouse embryonic fibroblasts as the feeder layer. Here, we show that the undifferentiated growth of ESD-EpiSCs could be maintained with the basic fibroblast growth factor employing human amnion epithelial cells (hAECs) as the feeder layer. Upon exposure to LIF, ESD-EpiSCs could undergo a reprogramming process on hAECs and be converted to naïve-like cells converted ESCs (cESCs), in which naïve pluripotency markers were activated, and primed markers were suppressed. DNA methylation analysis also validated the epigenetic conversion from primed to naïve-like pluripotent status. The bone morphogenetic protein 4 (BMP4) is an important signaling factor in pluripotency controlling, germ cell development, and neural commitment. It showed that ESD-EpiSCs and cESCs exhibited different features toward BMP4. Our results prove that hAECs are ideal feeder cells for both naïve and primed ESCs. More importantly, the primed ESCs are allowed to be reprogrammed to naïve-like pluripotent cells on hAECs. These findings suggest that under suitable conditions primed ESCs have the potency of converting to naïve-like ESCs.

Background As ovarian cancer stem cells (CSCs) are responsible for tumor initiation, invasion, metastasis, and chemo-resistance, new stratagems that selectively target ovarian CSCs are critically significant. Our previous work have demonstrated that ovarian cancer spheroid cells are tumorigenic and chemo-resistant, and have the properties of ovarian CSCs. Herein, we hypothesized that expressing α-gal epitopes on ovarian spheroid cells may help eliminate CSCs and improve the outcome of therapeutic intervention for ovarian cancer patients. Methods Lentivirus-mediated transfer of a pig α(1,3)galactosyltransferase [α1,3GT] enzyme gene into human ovarian cell line SKOV3 cells formed α-gal epitope-expressing cells (SKOV3-gal cells), and then these cells were maintained in a serum-free culture system to form SKOV3-gal spheroid cells. Efficacy of this cell vaccine was demonstrated in α1,3GT knockout mice (α1,3GT KO mice). Results The antibody titers to α-gal epitopes measured by ELISA were significantly increased in α1,3GT KO mice after immunization with SKOV3-gal spheroid cells. Furthermore, compared with the non-immunized KO mice, the SKOV3 tumors grafted under renal capsules of KO mice immunized with SKOV3-gal spheroid cells grew slower and began to shrink on day 12. Western blot analysis also showed that immunized KO mice can produce effective antibody against certain tumor associated antigens (TAAs) derived from both SKOV3 cells and SKOV3 spheroid cells. The TAAs were further investigated by mass spectrometry and RNA interference (RNAi) technology. The results suggested that antibodies responding to protein c-erbB-2 may be raised in the sera of the mice after immunization with SKOV3-gal spheroid cells. Ultimately, vaccination with SKOV3-gal spheroid cells induced more CD3 + CD4 + T cells in the spleen of immunized mice than non-immunized KO mice. Conclusions The results suggest that vaccination using ovarian cancer stem-like cells engineered to express α-gal epitopes may be a novel strategy for treatment of ovarian cancer. Electronic supplementary material The online version of this article (doi:10.1186/s12885-015-1973-7) contains supplementary material, which is available to authorized users.

PCR primers used to detect gene expression. (DOC 34Â kb)

siRNA sequences used in this study. (DOC 30Â kb)

International audience; The important functions of heat shock factor 1 (HSF1) in certain malignant cancers have granted it to be an appealing target for developing novel strategy for cancer therapy. Here, we report that higher HSF1 expression is associated with more aggressive malignization in epithelial ovarian tumors, indicating that targeting HSF1 is also a promising strategy against ovarian cancer. We found that a nucleoside analog (Ly101-4B) elicits efficient inhibition on HSF1 expression and potent anticancer activity on epithelial ovarian cancer both in vitro and in vivo. Moreover, by targeting HSF1, Ly101-4B inhibits the biogenesis of microRNA-214, which has been revealed to be overexpressed and to promote cell survival in human ovarian epithelial tumors. These findings demonstrate that Ly101-4B is a promising candidate for ovarian cancer therapy, and expand our understanding of HSF1, by revealing that it can regulate microRNA biogenesis in addition to its canonical function of regulating protein-coding RNAs.

Epithelial ovarian cancer remains the most lethal gynecologic malignancy and high recurrence rates due to resistance to further treatment with chemotherapy. Evidences showed that a pool of self-renewing malignant progenitors, cancer stem cells (CSCs) may contribute to chemotherapy resistance. Thus, targeting of CSC fraction may be critical for eliminating cancers cells. Here we will discuss the current knowledge regarding isolation of ovarian CSCs, EMT and the role of regulation by miRNAs in the context of drug resistance. Furthermore, we discuss direct CSC targeting approaches, for which therapeutic proof of principle has recently been established.

Skin-derived mesenchymal stem cells (SMSCs) can differentiate into the three embryonic germ layers. For this reason, they are considered a powerful tool for therapeutic cloning and offer new possibilities for tissue therapy. Recent studies showed that skin-derived stem cells can differentiate into cells expressing germ-cell specific markers in vitro and form oocytes in vivo. The idea that SMSCs may be suitable for the treatment of intractable diseases or traumatic tissue damage has attracted attention. To determine the ability of SMSCs to reactivate injured ovaries, a mouse model with ovaries damaged by busulfan and cyclophosphamide was developed and is described here. Female skin-derived mesenchymal stem cells (F-SMSCs) and male skin-derived mesenchymal stem cells (M-SMSCs) from red fluorescence protein (RFP) transgenic adult mice were used to investigate the restorative effects of SMSCs on ovarian function. Significant increases in total body weight and the weight of reproductive organs were observed in the treated animals. Both F-SMSCs and M-SMSCs were shown to be capable of partially restoring fertility in chemotherapy-treated females. Immunostaining with RFP and anti-Müllerian hormone (AMH) antibodies demonstrated that the grafted SMSCs survived, migrated to the recipient ovaries. After SMSCs were administered to the treated mice, real-time PCR showed that the expression levels of pro-inflammatory cytokines TNF-α, TGF-β, IL-8, IL-6, IL-1β, and IFNγ were significantly lower in the ovaries than in the untreated controls. Consistent with this observation, expression of oogenesis marker genes Nobox, Nanos3, and Lhx8 increased in ovaries of SMSCs-treated mice. These findings suggest that SMSCs may play a role within the ovarian follicle microenvironment in restoring the function of damaged ovaries and could be useful in reproductive health.