Ovarian Cancer Stem Cells Research Articles

Reciprocal Molecular Dialogues Between Ovarian Cancer Stem Cells and Their Microenvironmental Niches

Reciprocal Molecular Dialogues Between Ovarian Cancer Stem Cells and Their Microenvironmental Niches

Retraction Note: LINC00115 promotes stemness and inhibits apoptosis of ovarian cancer stem cells by upregulating SOX9 and inhibiting the Wnt/β-catenin pathway through competitively binding to microRNA-30a

Retraction Note: LINC00115 promotes stemness and inhibits apoptosis of ovarian cancer stem cells by upregulating SOX9 and inhibiting the Wnt/β-catenin pathway through competitively binding to microRNA-30a

Role of Peroxisome Proliferator-Activated Receptor α-Dependent Mitochondrial Metabolism in Ovarian Cancer Stem Cells.

Peroxisome proliferator-activated receptors (PPARs), including PPAR-α, PPAR-β/δ, and PPAR-γ, are involved in various cellular responses, including metabolism and cell proliferation. Increasing evidence suggests that PPARs are closely associated with tumorigenesis and metastasis. However, the exact role of PPARs in energy metabolism and cancer stem cell (CSC) proliferation remains unclear. This study investigated the role of PPARs in energy metabolism and tumorigenesis in ovarian CSCs. The expression of PPARs and fatty acid consumption as an energy source increased in spheroids derived from A2780 ovarian cancer cells (A2780-SP) compared with their parental cells. GW6471, a PPARα inhibitor, induced apoptosis in A2780-SP. PPARα silencing mediated by small hairpin RNA reduced A2780-SP cell proliferation. Treatment with GW6471 significantly inhibited the respiratory oxygen consumption of A2780-SP cells, with reduced dependency on fatty acids, glucose, and glutamine. In a xenograft tumor transplantation mouse model, intraperitoneal injection of GW6471 inhibited in vivo tumor growth of A2780-SP cells. These results suggest that PPARα plays a vital role in regulating the proliferation and energy metabolism of CSCs by altering mitochondrial activity and that it offers a promising therapeutic target to eradicate CSCs.

Chemotherapy Enriches for Proinflammatory Macrophage Phenotypes that Support Cancer Stem-Like Cells and Disease Progression in Ovarian Cancer.

High-grade serous ovarian cancer remains a poorly understood disease with a high mortality rate. Although most patients respond to cytotoxic therapies, a majority will experience recurrence. This may be due to a minority of drug-resistant cancer stem-like cells (CSC) that survive chemotherapy and are capable of repopulating heterogeneous tumors. It remains unclear how CSCs are supported in the tumor microenvironment (TME) particularly during chemotherapy exposure. Tumor-associated macrophages (TAM) make up half of the immune population of the ovarian TME and are known to support CSCs and contribute to cancer progression. TAMs are plastic cells that alter their phenotype in response to environmental stimuli and thus may influence CSC maintenance during chemotherapy. Given the plasticity of TAMs, we studied the effects of carboplatin on macrophage phenotypes using both THP1- and peripheral blood mononuclear cell (PBMC)-derived macrophages and whether this supports CSCs and ovarian cancer progression following treatment. We found that carboplatin exposure induces an M1-like proinflammatory phenotype that promotes SOX2 expression, spheroid formation, and CD117+ ovarian CSCs, and that macrophage-secreted CCL2/MCP-1 is at least partially responsible for this effect. Depletion of TAMs during carboplatin exposure results in fewer CSCs and prolonged survival in a xenograft model of ovarian cancer. This study supports a role for platinum-based chemotherapies in promoting a transient proinflammatory M1-like TAM that enriches for CSCs during treatment. Improving our understanding of TME responses to cytotoxic drugs and identifying novel mechanisms of CSC maintenance will enable the development of better therapeutic strategies for high-grade serous ovarian cancer. Significance: We show that chemotherapy enhances proinflammatory macrophage phenotypes that correlate with ovarian cancer progression. Given that macrophages are the most prominent immune cell within these tumors, this work provides the foundation for future translational studies targeting specific macrophage populations during chemotherapy, a promising approach to prevent relapse in ovarian cancer.

Bisphenol A-induced oxidative stress increases the production of ovarian cancer stem cells in mice

Bisphenol A (BPA) belongs to the endocrine disruptor chemicals (EDCs) causing various reproductive disorders in females. We analysed the toxic effects of BPA in the uterus and ovaries. The BPA was administered orally with the repeated low dose (LD, 1 mg/kg) and high dose (HD, 5 mg/kg) of body weight on alternate days for 4 months via oral gavage to Swiss mice. BPA administration decreases body weight, ovarian weight and size at LD, but increases ovarian weight and size at HD. The uterus weight, length, and diameter were increased in both the treated groups. The histopathological data show decreased ovarian follicle size, epithelial hyperplasia, and lymphocytic infiltration in the ovary. The BPA-treated uterus shows increased vascularization, atrophied endometrium and myometrium, and endometrial hyperplasia (EH) with aberrant glandular growth. The cancer stem cells (CSCs) in the ovaries were identified based on staining with anti-mouse CD44 and anti-mouse CD133 antibodies and analysed by flow cytometry. Three different populations of ovarian CSCs: CD44+CD133-, CD44+CD133+, and CD44−CD133+, can be recognised based on the intensity of these receptors. CD44+CD133- and CD44+CD133+ cell percentages were increased in BPA-treated groups. CD44−CD133+ were increased in LD but decreased in HD. The BPA administration also induces ROS production, which decreases the expression of antioxidant genes Superoxide dismutase 1 (SOD1), Superoxide dismutase 2 (SOD2), Catalase (CAT), Glutathione peroxidase 1 (GPX1), and Forkhead box O3 (FOXO3) in ovarian cells. In conclusion, BPA exposure induced an inflammatory response, increased CSC proportions, induced ROS, and decreased antioxidant responses in the ovaries.

Knocking down RAD51AP1 enhances chemosensitivity by inhibiting the self-renewal of CD133 positive ovarian cancer stem-like cells

PurposeThis study was designed to investigate the function of RAD51AP1 in the self-renewal and chemosensitivity of CD133 positive (CD133+) ovarian cancer (OC) stem-like cells.MethodsCD133+ (CD133 positive) OVCAR4 and CD133 negative (CD133−) OVCAR4 cells were separated from OVCAR4 by flow cytometry. Then, the separated CD133+OVCAR4 cells were divided into the following groups: Vector group; RAD51AP1 group; siNC group; si-RAD51AP1 group. Next, sphere-formation assay and colony forming assay were used to evaluate the self-renewal and proliferation ability of cells; western blot to detect the expression of RAD51AP1, transforming growth factor beta 1 (TGF-β1) and SMAD4 proteins in tissues and cells; qRT-PCR to assess the mRNA levels of sex-determining region Y-box 2 (SOX2), octamer-binding transcription factor 4 (OCT4), NANOG and Kruppel-like factor 4 (KLF4).ResultsThe performance of CD133+OVCAR4 cells was much better than that of CD133−OVCAR4 cells in sphere-formation assay and colony forming assay. Besides, compared with adjacent group and CD133−OVCAR4 cells, the expression level of RAD51AP1 increased significantly in OC group and CD133+OVCAR4 cells. Moreover, the over-expression of RAD51AP1 promoted the self-renewal and proliferation of CD133+OVCAR4 cells. On the contrary, knocking down the expression level of RAD51AP1 could inhibit the self-renewal and proliferation of CD133+OVCAR4 cells and improve the sensitivity of cells to chemotherapy drugs.ConclusionThe findings of this study showed that RAD51AP1 was highly expressed in OC tissue and CD133+OVCAR4 cells, and regulated the self-renewal and chemosensitivity of tumor cells through the TGF-β1/SMAD4 signaling pathway.

Exosomal LINC00958 maintains ovarian cancer cell stemness and induces M2 macrophage polarization via Hedgehog signaling pathway and GLI1 protein

Long non-coding RNA (lncRNA) LINC00958 has been reported to promote many gynecological cancers, but its detailed function in OC remains unclear. Cancer stem cells (CSCs) and tumor-associated macrophages (TAMs) have been reported to participate in the occurrence and metastasis of cancers. We want to explore the effects of exosomal LINC00958 on cell stemness and macrophage polarization in OC. LINC00958 expression was first verified in OC cells and its function on cell stemness was verified by subcellular fractionation analysis, sphere formation assay and so on. Exosomal LINC00958 was secreted from OC cells and the model of M2 macrophage polarization was established to further verify the impact of exosomal LINC00958 on the cell stemness and macrophage polarization of OC cells using several mechanism experiments including flow cytometry, RNA pulldown, luciferase reporter assays and so on. LINC00958 was up-regulated in OC cells and exosomal LINC00958 enhanced the stem cell-like properties of OC cells and M2 macrophage polarization. Furthermore, LINC00958 combined with glioma-associated oncogene homolog 1 (GLI1) to activate Hedgehog pathway, thereby promoting M2 polarization. Exosomal LINC00958 maintained OC cell stemness and induced M2 polarization via the Hedgehog signaling pathway.

1α,25-hydroxyvitamin D/VDR suppresses stem-like properties of ovarian cancer cells by restraining nuclear translocation of β-catenin

Several studies have indicated that 1α,25-hydroxyvitamin D [1α,25(OH)2D3] inhibits the proliferation and metastasis of cancer cells through suppressing epithelial-mesenchymal transition. However, its influence on the translocation of β-catenin remains unclear. In the present study, ovarian cancer stem-like cells (CSCs), including side population (SP) and CD44+/CD117+, were isolated from mouse ovarian surface epithelial (MOSE) cells with malignant transformation. The findings revealed that 1α,25(OH)2D3 obviously reduced the sphere-forming ability, as well as Notch1 and Klf levels. Moreover, the limiting dilution assay demonstrated that 1α,25(OH)2D3 effectively hindered the tumorigenesis of ovarian CSCs in vitro. Notably, treatment with 1α,25(OH)2D3 led to a substantial increase in the cell population of CD44+/CD117+ forming one tumor from ≤ 100 to 445 in orthotopic transplanted model, indicating a pronounced suppression of stemness of ovarian CSCs. Additionally, 1α,25(OH)2D3 robustly promoted the translocation of β-catenin from the nuclear to the cytoplasm through directly binding to VDR, which resulted in decreased levels of c-Myc and CyclinD1 within late MOSE cells. Taken together, these results strongly supported the role of 1α,25(OH)2D3 in inhibiting stem-like properties in ovarian cancer cells by restraining nuclear translocation of β-catenin, thereby offering a promising target for cancer therapeutics.

Restriction of YWHAB-mediated YAP cytoplasmic retention as a novel mechanism underlying stemness maintenance and chemo-resistance in peritoneal metastasis of ovarian cancer: A comparative proteomic study.

122 Background: Ovarian cancer (OC) peritoneal metastasis (OCPM) is a significant cause of high mortality of OC. To investigate the mechanisms underlying OCPM stemness maintenance and resistance, we characterized proteomic alterations in residual OCPM tissues after neoadjuvant chemotherapy (NACT), and verified restriction of YWHAB-mediated YAP cytoplasmic retention as a novel important mechanism. Methods: Tumor specimens from HGSOC patients underwent proteomic analysis using TMT and REACTOME for pathway and GO analysis. The OVCAR3 cell line, derived from malignant ascites, and formalin-fixed samples were used for Immunohistochemistry. Ovarian cancer stem-like cells, including cisplatin-resistant cells, were cultured, and ALHD activity was measured by qPCR and ALDEFLUOR Kit. Western blot and Co-IP were used for protein analysis. Sphere formation and limiting dilution assays were performed in vitro and in vivo using BALB/c nude mice, and FACS quantified OCSCs. YWHAB-knockdown cells were created via plasmids, lentivirus, and transfection. Statistical tests included paired and unpaired t-tests, one-way ANOVA, and ELDA for limiting dilution. Data are shown as mean ± SD, with *p< 0.05, **p< 0.01, ***p< 0.001 indicating significance. Results: TMT-based proteomics identified 324 differentially expressed proteins in post-NACT OCPM tissues, with 179 upregulated and 145 downregulated. Bioinformatics revealed novel targets in key pathways, including TUBB, VCP in Hedgehog, YWHAB in Hippo, TLA1/2, SPTA1 in MAPK, and FASN in NOTCH. YWHAB downregulation was confirmed in pPR OCPM tissues and cells, serving as a marker to differentiate pNR from pCR/pPR OCPM (AUC = 0.7673). YWHAB inhibition in pCR OCPM cells enhanced stemness, as seen in sphere formation, OCSC percentages, CD133 expression, ALDH activity, and tumorigenicity. It also induced cisplatin resistance. YWHAB inhibition reduced cytoplasmic YAP retention and increased nuclear YAP, enhancing transcriptional activity. YAP5SA expression negated the effects of YWHAB depletion on stemness and resistance in pCR OCPM cells. Conclusions: In summary, this study explored the potential mechanisms underlying OCPM stemness maintenance and resistance by employing proteomic analysis, and revealed a novel YWHAB-mediated mechanism. This finding indicates that YAP would an important target for eradicating YWHAB-restricted OCSCs in OCPM.

Autophagy-mediated ID1 turnover dictates chemo-resistant fate in ovarian cancer stem cells

BackgroundThe mechanisms enabling dynamic shifts between drug-resistant and drug-sensitive states in cancer cells are still underexplored. This study investigated the role of targeted autophagic protein degradation in regulating ovarian cancer stem cell (CSC) fate decisions and chemo-resistance.MethodsAutophagy levels were compared between CSC-enriched side population (SP) and non-SP cells (NSP) in multiple ovarian cancer cell lines using immunoblotting, immunofluorescence, and transmission electron microscopy. The impact of autophagy modulation on CSC markers and differentiation was assessed by flow cytometry, immunoblotting and qRT-PCR. In silico modeling and co-immunoprecipitation identified ID1 interacting proteins. Pharmacological and genetic approaches along with Annexin-PI assay, ChIP assay, western blotting, qRT-PCR and ICP-MS were used to evaluate effects on cisplatin sensitivity, apoptosis, SLC31A1 expression, promoter binding, and intracellular platinum accumulation in ID1 depleted backdrop. Patient-derived tumor spheroids were analyzed for autophagy and SLC31A1 levels.ResultsOvarian CSCs exhibited increased basal autophagy compared to non-CSCs. Further autophagy stimulation by serum-starvation and chemical modes triggered proteolysis of the stemness regulator ID1, driving the differentiation of chemo-resistant CSCs into chemo-sensitive non-CSCs. In silico modeling predicted TCF12 as a potent ID1 interactor, which was validated by co-immunoprecipitation. ID1 depletion freed TCF12 to transactivate the cisplatin influx transporter SLC31A1, increasing intracellular cisplatin levels and cytotoxicity. Patient-derived tumor spheroids exhibited a functional association between autophagy, ID1, SLC31A1, and platinum sensitivity.ConclusionsThis study reveals a novel autophagy-ID1-TCF12-SLC31A1 axis where targeted autophagic degradation of ID1 enables rapid remodeling of CSCs to reverse chemo-resistance. Modulating this pathway could counter drug resistance in ovarian cancer.

STAU1-mediated CNBP mRNA degradation by LINC00665 alters stem cell characteristics in ovarian cancer

BackgroundTo investigate the role of lncRNA LINC00665 in modulating ovarian cancer stemness and its influence on treatment resistance and cancer development.MethodsWe isolated ovarian cancer stem cells (OCSCs) from the COC1 cell line using a combination of chemotherapeutic agents and growth factors, and verified their stemness through western blotting and immunofluorescence for stem cell markers. Employing bioinformatics, we identified lncRNAs associated with ovarian cancer, with a focus on LINC00665 and its interaction with the CNBP mRNA. In situ hybridization, immunohistochemistry, and qPCR were utilized to examine their expression and localization, alongside functional assays to determine the effects of LINC00665 on CNBP.ResultsLINC00665 employs its Alu elements to interact with the 3’-UTR of CNBP mRNA, targeting it for degradation. This molecular crosstalk enhances stemness by promoting the STAU1-mediated decay of CNBP mRNA, thereby modulating the Wnt and Notch signaling cascades that are pivotal for maintaining CSC characteristics and driving tumor progression. These mechanistic insights were corroborated by a series of in vitro assays and validated in vivo using tumor xenograft models. Furthermore, we established a positive correlation between elevated CNBP levels and increased disease-free survival in patients with ovarian cancer, underscoring the prognostic value of CNBP in this context.ConclusionslncRNA LINC00665 enhances stemness in ovarian cancer by mediating the degradation of CNBP mRNA, thereby identifying LINC00665 as a potential therapeutic target to counteract drug resistance and tumor recurrence associated with CSCs.

Targeting Ovarian Cancer Stem Cells by Dual Inhibition of the Long Noncoding RNA HOTAIR and Lysine Methyltransferase EZH2.

Persistence of cancer stem cells (CSCs) is believed to contribute to resistance to platinum-based chemotherapy and disease relapse in ovarian cancer, the fifth leading cause of cancer-related death among US women. HOXC transcript antisense RNA (HOTAIR) is a long noncoding RNA (lncRNA) overexpressed in high-grade serous ovarian cancer and linked to chemoresistance. However, HOTAIR impacts chromatin dynamics in ovarian CSCs and how this oncogenic lncRNA contributes to drug resistant disease are incompletely understood. Here we generated HOTAIR knock-out (KO) high-grade serous ovarian cancer cell lines using paired CRISPR guide RNA design to investigate the function of HOTAIR. We show loss of HOTAIR function re-sensitized ovarian cancer cells to platinum treatment and decreased the population of ovarian CSCs. Furthermore, HOTAIR KO inhibited development of stemness-related phenotypes, including spheroid formation ability, as well as expression of key stemness-associated genes ALDH1A1, NOTCH3, SOX9, and PROM1. HOTAIR KO altered both the cellular transcriptome and chromatin accessibility landscape of multiple oncogenic-associated genes and pathways, including the NF-kB pathway. HOTAIR functions as an oncogene by recruiting enhancer of zeste 2 (EZH2) to catalyze H3K27 tri-methylation to suppress downstream tumor suppressor genes, and it was of interest to inhibit both HOTAIR and EZH2. In vivo, combining a HOTAIR inhibitor with an EZH2 inhibitor and platinum chemotherapy decreased tumor formation and increased survival. These results suggest a key role for HOTAIR in ovarian CSCs and malignant potential. Targeting HOTAIR in combination with epigenetic therapies may represents therapeutic strategy to ameliorate ovarian cancer progression and resistance to platinum-based chemotherapy.

FXN targeting induces cell death in ovarian cancer stem-like cells through PRDX3-Mediated oxidative stress

Ovarian cancer stem cells (OCSCs) significantly impact the prognosis, chemoresistance, and treatment outcomes in OC. While ferroptosis has been proven effective against OCSCs, the intricate relationship between ferroptosis and OCSCs remains incompletely understood. Here, we enriched ovarian cancer stem-like cells (OCSLCs) through mammosphere culture, as an OCSC model. OCSLCs displayed heightened ferroptosis susceptibility, correlating with elevated FXN levels compared to non-stem OC cells. FXN has recently emerged as a potential regulator in ferroptosis. FXN knockdown diminished stemness marker nanog, sphere-forming ability, increased reactive oxygen species (ROS) generation, and attenuated OCSLCs viability. FXN overexpression exacerbated ferroptosis resistance and reduced RSL3-induced cell death. FXN knockdown impeded OCSLC xenograft tumor growth and exacerbated the degeneration of peroxiredoxin 3 (PRDX3), a mitochondrial antioxidant protein participates in oxidative stress. Thus, elevated FXN in OCSLCs suppresses ROS accumulation, fostering ferroptosis resistance, and regulates the antioxidant protein PRDX3. FXN emerges as a potential therapeutic target for OC.

Advances in ovarian tumor stem cells and therapy.

Ovarian cancer is considered the most lethal among all gynecological malignancies due to its early metastatic dissemination, extensive spread, and malignant ascites. The current standard of care for advanced ovarian cancer involves a combination of cytoreductive surgery and chemotherapy utilizing platinum-based and taxane-based agents. Although initial treatment yields clinical remission in 70-80% of patients, the majority eventually develop treatment resistance and tumor recurrence. A growing body of evidence indicates the existence of cancer stem cells within diverse solid tumors, including ovarian cancer, which function as a subpopulation to propel tumor growth and disease advancement by means of drug resistance, recurrence, and metastasis. The presence of ovarian cancer stem cells is widely considered to be a significant contributor to the unfavorable clinical outcomes observed in patients with ovarian cancer, as they play a crucial role in mediating chemotherapy resistance, recurrence, and metastasis. Ovarian cancer stem cells possess the capacity to reassemble within the entirety of the tumor following conventional treatment, thereby instigating the recurrence of ovarian cancer and inducing resistance to treatment. Consequently, the creation of therapeutic approaches aimed at eliminating ovarian cancer stem cells holds great potential for the management of ovarian cancer. These cells are regarded as one of the most auspicious targets and mechanisms for the treatment of ovarian cancer. There is a pressing need for a comprehensive comprehension of the fundamental mechanisms of ovarian cancer's recurrence, metastasis, and drug resistance, alongside the development of effective strategies to overcome chemoresistance, metastasis, and recurrence. The implementation of cancer stem cell therapies may potentially augment the tumor cells' sensitivity to existing chemotherapy protocols, thereby mitigating the risks of tumor metastasis and recurrence, and ultimately improving the survival rates of ovarian cancer patients.

The Potential of Nanotechnology to Replace Cancer Stem Cells.

Stem cells, which were initially identified in the 1900s, are distinct cells with the potential to replenish themselves as well as differentiate into specialised cells with certain forms and functions. Cancer stem cells play a significant role in the growth and recurrence of the tumours and, similar to normal stem cells, are capable of proliferating and differentiating. Traditional cancer treatments are ineffective against cancer stem cells, which leads to tumour regrowth. Cancer stem cells are thought to emerge as a result of epithelial-to-mesenchymal transition pathways. Brain, prostate, pancreatic, blood, ovarian, lung, liver, melanomas, AML, and breast cancer stem cells are among the most prevalent cancer forms. This review aims to comprehend the possibility of using specific forms of nanotechnology to replace cancer stem cells. In terms of nanotechnology, magnetic nanoparticles can deliver medications, especially to the target region without harming healthy cells, and they are biocompatible. In order to kill glioma cancer stem cells, the gold nanoparticles bond with DNA and function as radio sensitizers. In contrast, liposomes can circulate and traverse biological membranes and exhibit high therapeutic efficacy, precise targeting, and better drug release. Similar to carbon nanotubes, grapheme, and grapheme oxide, these substances can be delivered specifically when utilized in photothermal therapy. Recent treatments including signaling pathways and indicators targeted by nanoparticles are being researched. Future research in nanotechnology aims to develop more effective and targeted medicinal approaches. The results of the current investigation also showed that this technology's utilization will improve medical therapy and treatment.

Exosomal miR-4516 derived from ovarian cancer stem cells enhanced cisplatin tolerance in ovarian cancer by inhibiting GAS7

Ovarian cancer (OC) is a devastating disease for women, with chemotherapy resistance taking the lead. Cisplatin has been the first-line therapy for OC for a long time. However, the resistance of OC to cisplatin is an important impediment to its efficacy. Mounting studies showed that ovarian cancer stem cells (OCSCs) affected chemotherapy resistance by secreting exosomes. MicroRNAs (miRNAs) play important roles in exosomes secreted by OCSCs. Here, through the analysis of GEO database (GSE107155) combined with RT-qPCR of OC-related cells/clinical tissues, it was found that hsa-miR-4516 (miR-4516) was significantly up-regulated in OCSCs. Then, OCSCs-derived exosomes were isolated and identified, and it was observed the influence of exosomes on the chemoresistance in SKOV3/cisplatin (SKOV3/DDP) cells. These results manifested that OCSCs-mediated exosomes facilitated the chemoresistance of SKOV3/DDP cells by delivering miR-4516 into them. Growth arrest-specific 7 (GAS7), a downstream target of miR-4516, was determined by bioinformatics prediction combined with molecular biological detection. Next, we up-regulated GAS7 expression and discovered that the promotion of chemoresistance in SKOV3/DDP cells by OCSCs-derived exosomes was significantly impaired. Finally, the mice tumor model of SKOV3/DDP cells was built to estimate the effect of GAS7 over-expression on OC growth. The results showed that GAS7 inhibited the chemoresistance of OC in vivo. In conclusion, our experiments suggested that OCSCs-derived exosomes enhanced OC cisplatin resistance by suppressing GAS7 through the delivery of miR-4516. This study provides a possible target for the treatment of OC DDP resistance.

Astragalus polysaccharides sensitize ovarian cancer stem cells to PARPi by inhibiting mitophagy via PINK1/Parkin signaling

Ovarian cancer (OC) remains the most lethal gynecological malignant tumor. PARP inhibitors (PARPi) have significantly improved survival, particularly in patients with OC with BRCA1/2 mutations. However, the majority of patients eventually develop resistance to PARPi. Cancer stem cells (CSCs) are considered the source of drug resistance in cancer. Our study found that the synergistic effect of astragalus polysaccharides (APSs) and PARPi was observed in ovarian cancer stem cells (OCSCs) by decreasing cell viability and self-renewal potential while inducing apoptosis. The present study also demonstrated that OCSCs had increased mitophagy. Furthermore, it was observed that APS in combination with PARPi inhibits mitophagy and downregulates the PINK1 protein level in OCSCs. The overexpression of PINK1 via the pEGFP(+)-PINK1 plasmid resulted in a partial reversal of the increased susceptibility of OCSCs when PARPi were administrated concurrently with APS. In conclusion, APS increases OCSC sensitivity to PARPi by inhibiting mitophagy via the PINK1/Parkin pathway regulation.

ARID1A restrains EMT and stemness of ovarian cancer cells through the Hippo pathway.

Genes encoding subunits of SWI/SNF (BAF) chromatin‑remodeling complexes are recurrently mutated in a broad array of tumor types, and among the subunits, ARID1A is the most frequent target with mutations. In the present study, it was reported that ARID1A inhibits the epithelial‑mesenchymal transition (EMT) and stemness of ovarian cancer cells, accompanied by reduced cell viability, migration and colony formation, suggesting that ARID1A acts as a tumor suppressor in ovarian cancer. Mechanistically, ARID1A exerts its inhibitory effects on ovarian cancer cells by activating the Hippo signaling pathway. Conversely, the overexpression of a gain‑of‑function transcriptional co‑activator with PDZ‑binding motif (TAZ) mutant (TAZ‑Ser89) effectively reverses the effects induced by ARID1A. In addition, activation of Hippo signaling apparently upregulates ARID1A protein expression, whereas ectopic expression of TAZ‑Ser89 results in the markedly decreased ARID1A levels, indicating a feedback of ARID1A‑TAZ in regulating ovarian cancer cell EMT and stemness. Thus, the present study uncovered the role of ARID1A through the Hippo/TAZ pathway in modulating EMT and stemness of ovarian cancer cells, and providing with evidence that TAZ inhibitors could effectively prevent initiation and metastasis of ovarian cancer cases where ARID1A is lost or mutated.

Integrin-linked kinase-frizzled 7 interaction maintains cancer stem cells to drive platinum resistance in ovarian cancer

BackgroundPlatinum-based chemotherapy regimens are a mainstay in the management of ovarian cancer (OC), but emergence of chemoresistance poses a significant clinical challenge. The persistence of ovarian cancer stem cells (OCSCs) at the end of primary treatment contributes to disease recurrence. Here, we hypothesized that the extracellular matrix protects CSCs during chemotherapy and supports their tumorigenic functions by activating integrin-linked kinase (ILK), a key enzyme in drug resistance.MethodsTCGA datasets and OC models were investigated using an integrated proteomic and gene expression analysis and examined ILK for correlations with chemoresistance pathways and clinical outcomes. Canonical Wnt pathway components, pro-survival signaling, and stemness were examined using OC models. To investigate the role of ILK in the OCSC-phenotype, a novel pharmacological inhibitor of ILK in combination with carboplatin was utilized in vitro and in vivo OC models.ResultsIn response to increased fibronectin secretion and integrin β1 clustering, aberrant ILK activation supported the OCSC phenotype, contributing to OC spheroid proliferation and reduced response to platinum treatment. Complexes formed by ILK with the Wnt receptor frizzled 7 (Fzd7) were detected in tumors and correlated with metastatic progression. Moreover, TCGA datasets confirmed that combined expression of ILK and Fzd7 in high grade serous ovarian tumors is correlated with reduced response to chemotherapy and poor patient outcomes. Mechanistically, interaction of ILK with Fzd7 increased the response to Wnt ligands, thereby amplifying the stemness-associated Wnt/β-catenin signaling. Notably, preclinical studies showed that the novel ILK inhibitor compound 22 (cpd-22) alone disrupted ILK interaction with Fzd7 and CSC proliferation as spheroids. Furthermore, when combined with carboplatin, this disruption led to sustained AKT inhibition, apoptotic damage in OCSCs and reduced tumorigenicity in mice.ConclusionsThis “outside-in” signaling mechanism is potentially actionable, and combined targeting of ILK-Fzd7 may lead to new therapeutic approaches to eradicate OCSCs and improve patient outcomes.

Tumor microenvironment-induced FOXM1 regulates ovarian cancer stemness

In ovarian tumors, the omental microenvironment profoundly influences the behavior of cancer cells and sustains the acquisition of stem-like traits, with major impacts on tumor aggressiveness and relapse. Here, we leverage a patient-derived platform of organotypic cultures to study the crosstalk between the tumor microenvironment and ovarian cancer stem cells. We discovered that the pro-tumorigenic transcription factor FOXM1 is specifically induced by the microenvironment in ovarian cancer stem cells, through activation of FAK/YAP signaling. The microenvironment-induced FOXM1 sustains stemness, and its inactivation reduces cancer stem cells survival in the omental niche and enhances their response to the PARP inhibitor Olaparib. By unveiling the novel role of FOXM1 in ovarian cancer stemness, our findings highlight patient-derived organotypic co-cultures as a powerful tool to capture clinically relevant mechanisms of the microenvironment/cancer stem cells crosstalk, contributing to the identification of tumor vulnerabilities.