Isolation and characterization of side population cells from the human ovarian cancer cell line SK-OV-3

Enhanced DNA damage response through RAD50 in triple negative breast cancer resistant and cancer stem-like cells contributes to chemoresistance

A growing body of evidence supports the notion that cancer resistance is driven by a small subset of cancer stem cells (CSC), responsible for tumor initiation, growth, and metastasis. Both CSC and chemoresistant cancer cells may share common qualities to activate a series of self-defense mechanisms against chemotherapeutic drugs. Here, we aimed to identify proteins in chemoresistant triple-negative breast cancer (TNBC) cells and corresponding CSC-like spheroid cells that may contribute to their resistance. We have identified several candidate proteins representing the subfamilies of DNA damage response (DDR) system, the ATP-binding cassette, and the 26S proteasome degradation machinery. We have also demonstrated that both cell types exhibit enhanced DDR when compared to corresponding parental counterparts, and identified RAD50 as one of the major contributors in the resistance phenotype. Finally, we have provided evidence that depleting or blocking RAD50 within the Mre11-Rad50-NBS1 (MRN) complex resensitizes CSC and chemoresistant TNBC cells to chemotherapeutic drugs.

Role of autophagy in regulation of glioma stem cells population during therapeutic stress

Glioblastoma is highly recurrent and aggressive tumor with poor prognosis where existence of glioma stem cell (GSCs) population is well established. The GSCs display stem cell properties such as self-renewable, proliferation and therapeutic resistance which contribute to its role in tumor progression, metastasis and recurrence. Cancer stem cells (CSCs) can also be induced from non-stem cancer cells in response to radio/chemotherapy that further contribute to cancer relapse post therapy. Role of autophagy has been implicated in the existence of CSCs in different cancers; however, its role in GSCs is still unclear. Moreover, since autophagy is induced in response to various chemotherapeutic agents, it becomes imperative to understand the role of autophagy in therapy-induced pool of CSCs. Here, we investigated the role of autophagy in the maintenance of GSCs and temozolomide (TMZ)-induced therapeutic response. Glioblastoma cell lines (U87MG, LN229) were cultured as monolayer as well as GSC enriched tumorspheres and sub-spheroid population. Our results demonstrated that the tumorspheres maintained higher level of autophagy than the monolayer cells and inhibition of autophagy significantly reduced the percentage of GSCs and their self-renewal capacity. Further, TMZ at clinically relevant concentration resulted in an induction of survival autophagy in glioblastoma cells. We also observed that TMZ treatment significantly increased the expression of GSC markers, suggesting an increased pool of GSCs. Importantly, inhibition of autophagy prevented this TMZ-induced increased GSC population, suggesting a critical role for autophagy in therapy-induced generation of GSC pool. Overall, our findings revealed; i) higher levels of autophagy in GSCs; ii) TMZ induces protective autophagy and up-regulates pool of GSCs; and iii) inhibition of autophagy prevents TMZ-induced GSCs pool suggesting its role regulating GSC population in response to chemotherapy. Our study signifies a positive contribution of autophagy in survival of GSCs which implicates the use of autophagy inhibitors in a combinational approach to target TMZ-induced GSCs for developing effective therapeutic strategies. Further efforts are required to study the role of autophagy in therapy- induced GSC pool in other cancer types for its broad therapeutic implication.

Hypoxia induces an endometrial cancer stem-like cell phenotype via HIF-dependent demethylation of SOX2 mRNA

Endometrial cancer stem cells (ECSCs) are stem-like cells endowed with self-renewal and differentiation abilities, and these cells are essential for cancer progression in endometrial cancer (EC). As hallmarks of the tumour microenvironment (TME), hypoxia and hypoxia-inducing factors (HIFs) give rise to the dysregulation of tumour stemness genes, such as SOX2. Against this backdrop, we investigated the regulatory mechanisms regulated by HIFs and SOX2 in ECSCs during EC development. Here, ECSCs isolated from EC cell lines and tissues were found to express stemness genes (CD133 and aldehyde dehydrogenase, ALDH1) following the induction of their ECSC expansion. Notably, m⁶A methylation of RNA and HIF-1α/2α-dependent AlkB homologue 5 (ALKBH5) participate in the regulation of HIFs and SOX2 in EC, as confirmed by the observations that mRNA levels of m⁶A demethylases and ALKBH5 significantly increase under hypoxic conditions in ECSCs. Moreover, hypoxia and high ALKBH5 levels restore the stem-like state of differentiated ECSCs and increase the ECSC-like phenotype, whereas the knockdown of HIFs or ALKBH5 significantly reduces their tumour initiation capacity. In addition, our findings validate the role of ALKBH5 in promoting SOX2 transcription via mRNA demethylation, thereby maintaining the stem-like state and tumorigenicity potential of ECSCs. In conclusion, these observations demonstrate a critical role for m⁶A methylation-mediated regulation of the HIF-ALKBH5-SOX2 axis during ECSC expansion in hypoxic TMEs.

Ovarian cancer stem cells and targeted therapy

BACKGROUND

Ovarian cancer has the highest ratio of mortality among gynecologic malignancies. Chemotherapy is one of the most common treatment options for ovarian cancer. However, tumor relapse in patients with advanced tumor stage is still a therapeutic challenge for its clinical management.

MAIN BODY

Therefore, it is required to clarify the molecular biology and mechanisms which are involved in chemo resistance to improve the survival rate of ovarian cancer patients. Cancer stem cells (CSCs) are a sub population of tumor cells which are related to drug resistance and tumor relapse.

CONCLUSION

In the present review, we summarized the recent findings about the role of CSCs in tumor relapse and drug resistance among ovarian cancer patients. Moreover, we focused on the targeted and combinational therapeutic methods against the ovarian CSCs.

Characterization of the stemness potency of mammospheres isolated from the breast cancer cell lines

Stemness phenotype mammospheres established from cell lines and tissues taken from autopsy can be used to test and to identify the most sensitive drugs for chemotherapy. Therefore, the aim of the present study was isolation and characterization of cancer stem cells derived from MCF7, MDA-MB231, and SKBR3 breast cancer cell lines to demonstrate the stemness phenotypes of mammospheres generated for further their applications in therapeutic approaches. In this study, two luminal subtypes of cell lines, MCF7 and SKBR3 and a basal subtype cell line, MDA-MB-231, were chosen. Mammosphere culturing was implemented for breast cancer stem cells isolation and mammosphere formation efficiency. At the next step, CD44+/CD24– cell ratio, Oct4 and Nanog mRNA levels, proliferation rate, migration rate of mammospheres, and drug resistance (in third passage) were evaluated. In addition, tumorigenicity of mammospheres in the chick embryo model was evaluated and compared through the chick chorioallantoic membrane assay. Among mammospheres formed in all three cell lines, MCF7 had the highest mammosphere formation efficiency. CD24 marker (a differentiation marker for the breast cancer cells) was significantly reduced in the mammospheres generated from MCF7 and SKBR3, during three passages. Also, Oct4 and Nanog transcript levels were significantly higher in all three types of mammospheres, as compared with their cell lines. Proliferation, migration rate, and drug resistance of mammospheres generated from all three cell lines were found to be significantly higher. Tumorigenicity of MCF7 mammospheres was confirmed through tumor size measurement. Also, tumorigenicity of MCF7 and SKBR3 mammospheres was confirmed through more migration from ectoderm to mesoderm and endoderm. We succeeded to establish the technology that can be extended to tissue in the future. We have demonstrated a number of mammospheres can be generated from cell lines. Also, cells with different molecular features showed different stemness phenotypes.

BRCA1 affects the resistance and stemness of SKOV3-derived ovarian cancer stem cells by regulating autophagy

Breast cancer 1 (BRCA1) and autophagy both play a significant role in drug resistance. However, little is known about the dynamic cross talk between BRCA1 and autophagy in the regulation of drug sensitivity. Here, we investigated the drug resistance-associated regulation of BRCA1 in epithelial ovarian cancer stem cells (EOCSCs). The results indicated that BRCA1 could regulate drug resistance in EOCSCs. Autophagy played a significant role in the stemness maintenance and was a key mechanism underlying the survival against chemotherapy in EOCSCs. Further investigation found that BRCA1 could regulate drug resistance of EOCSCs through autophagy. Meanwhile, changes in the level of autophagy provided feedback regarding the expression of BRCA1. Inhibition of autophagy activity could effectively reduce the resistance of EOCSCs caused by BRCA1. In addition, BRCA1 was able to regulate cellular apoptosis and cell cycle progression under the action of cisplatin through autophagy, indirectly affecting the drug sensitivity of EOCSCs. The present results highlight a novel relationship between BRCA1 and autophagy, which may provide insight into the etiology of BRCA1-associated ovarian cancer, and improve our understanding of resistance mechanisms in ovarian cancer.

A Novel TGFβ Trap Blocks Chemotherapeutics-Induced TGFβ1 Signaling and Enhances Their Anticancer Activity in Gynecologic Cancers

Purpose: We investigated the mechanisms of how TGFβ pathway is activated by chemotherapeutics and whether a novel TGFβ trap called RER can block chemotherapeutics-induced TGFβ pathway activation and enhance their antitumor activity in gynecologic cancer.Patients and Methods: An unbiased bioinformatic analysis of differentially expressed genes in 31 ovarian cases due to chemotherapy was used to identify altered master regulators. Phosphorylated Smad2 was determined in 30 paired cervical cancer using IHC. Furthermore, the effects of chemotherapeutics on TGFβ signaling and function, and the effects of RER on chemotherapy-induced TGFβ signaling were determined in gynecologic cancer cells.Results: Chemotherapy-induced transcriptome alteration in ovarian cancer was significantly associated with TGFβ signaling activation. Chemotherapy was found to activate TGFβ signaling as indicated by phosphorylated Smad2 in paired cervical tumor samples (pre- and post-chemotherapy). Similar to TGFβ1, chemotherapeutics were found to stimulate Smad2/3 phosphorylation, cell migration, and markers related to epithelial-mesenchymal transition (EMT) and cancer stem cells (CSC). These TGFβ-like effects were due to the stimulation of TGFβ1 expression and secretion, and could all be abrogated by TGFβ inhibitors including a novel TGFβ trap protein called RER both in vitro and in vivo Importantly, combination treatment with RER and cisplatin showed a higher tumor inhibitory activity than either agent alone in a xenograft model of ovarian cancer.Conclusions: Chemotherapeutics can stimulate TGFβ1 production and consequently enhance TGFβ signaling, EMT, and CSC features resulting in reduced chemo-sensitivity. Combination therapy with a TGFβ inhibitor should alleviate this unintended side effect of chemotherapeutics and enhance their therapeutic efficacy. Clin Cancer Res; 24(12); 2780-93. ©2018 AACR.

3-Oxoacid CoA transferase 1 as a therapeutic target gene for cisplatin-resistant ovarian cancer

Ovarian cancer (OC) is the second leading cause of mortality from gynecological malignancies and has the highest mortality rate worldwide. As it is commonly asymptomatic during the early stages of the disease, >70% of patients with OC are diagnosed at advanced stages with metastasis. Despite treatment methods, including optimal debulking surgery and chemotherapy with the platinum-based drug cisplatin, OC recurrence is often inevitable, with an overall 5-year survival rate of 45%, mostly due to the steady development of cisplatin resistance. To identify genes involved in cisplatin resistance, the present study determined the half-maximal inhibitory concentrations of eight different OC cell lines and classified them into two groups (sensitive and resistant). mRNA expression was analyzed with GeneChip Human Gene 1.0 ST Arrays, and DNA methylation profiles were evaluated with the HumanMethylation450 BeadChip. Using an integrated approach of analyzing gene expression levels and DNA methylation profiles simultaneously, 26 genes were selected that were differentially expressed and methylated between the resistant and sensitive groups. Among these 26 genes, 3-oxoacid CoA transferase 1 (OXCT1), which was demonstrated to be downregulated and hypermethylated at promoter CpGs in the cisplatin-resistant group compared with the cisplatin-sensitive group, was selected for further investigation. Treatment with a DNA methyltransferase inhibitor restored hypermethylation-mediated gene silencing of OXCT1 in the cisplatin-resistant group, but not in the cisplatin-sensitive group. Furthermore, overexpression of OXCT1 conferred sensitivity to cisplatin in OC cells. The results of the present study suggest that OXCT1 serves an important role in conferring cisplatin sensitivity, and may provide a potential therapeutic target for cisplatin chemotherapy in patients with recurrent OC.

Preliminary identification of endometrial cancer stem cells in vitro and in vivo

Stem cells play a critical role in endometrial cancer progression. However, the current methodologies used to isolate endometrial cancer stem cells (ECSCs) remain unsatisfactory. The ECSCs were isolated by serumfree suspension cultivation. The stem cells-related genes CD44, CD133, Oct4, Sox2 and Nanog were analyzed, and the biological behaviour of ECSCs was evaluated in vitro and vivo. The results suggest that (i) serumfree suspension cultivation is non-toxic and a convenient way for isolating the ECSCs, and is not limited to specific surface markers; (ii) Ishikawa cells can be used as an effective source of ECSCs, and the obtained ECSCs expressing the pluripotent stem cells markers CD44, CD133, Oct4, Sox2, and Nanog; (iii) ECSCs originated from Ishikawa cells showed an increased ability to invasion and metastasis in vitro, and exhibited a high proliferative capacity and pluripotency in vivo and vitro. These findings indicate that serumfree suspension cultivation is an effective method for isolating ECSCs from Ishikawa cells, and the obtained ECSCs are tumorigenic and display stem cell-like properties.

The Clinical Relevance of Beta Blockers in Ovarian Carcinoma: A Systematic Review

The last ten years have seen hardly any improvement in the prognosis of ovarian carcinoma. There is a great need for new treatment strategies, and a recent retrospective study showing a survival advantage with the use of beta blockers met with a very positive response. This systematic review summarizes the current state of knowledge and research on the topic: A database analysis identified six clinical studies showing inconsistent results with respect to the administration of beta blockers and disease course. The 13 preclinical studies identified showed almost without exception both that catecholamines had detrimental effects on tumour progression, and that these effects could be influenced by pharmacological blockade. Overall the available evidence does not justify the use of beta blockers in clinical practice for ovarian carcinoma at the present time. This article also outlines details of research design required for further studies needed on the subject. Preclinical research findings are however very impressive: They not only form an important basis for the development of future clinical studies but also, through revealing new pathomechanisms, they already make an important contribution towards the development of new treatment strategies for ovarian carcinoma.