Mirvetuximab Soravtansine in FRα-Positive, Platinum-Resistant Ovarian Cancer.

BACKGROUND: Mirvetuximab soravtansine-gynx (MIRV), a first-in-class antibody-drug conjugate targeting folate receptor α (FRα), is approved for the treatment of platinum-resistant ovarian cancer in the United States. METHODS: We conducted a phase 3, global, confirmatory, open-label, randomized, controlled trial to compare the efficacy and safety of MIRV with the investigator's choice of chemotherapy in the treatment of platinum-resistant, high-grade serous ovarian cancer. Participants who had previously received one to three lines of therapy and had high FRα tumor expression (≥75% of cells with ≥2+ staining intensity) were randomly assigned in a 1:1 ratio to receive MIRV (6 mg per kilogram of adjusted ideal body weight every 3 weeks) or chemotherapy (paclitaxel, pegylated liposomal doxorubicin, or topotecan). The primary end point was investigator-assessed progression-free survival; key secondary analytic end points included objective response, overall survival, and participant-reported outcomes. RESULTS: A total of 453 participants underwent randomization; 227 were assigned to the MIRV group and 226 to the chemotherapy group. The median progression-free survival was 5.62 months (95% confidence interval [CI], 4.34 to 5.95) with MIRV and 3.98 months (95% CI, 2.86 to 4.47) with chemotherapy (P<0.001). An objective response occurred in 42.3% of the participants in the MIRV group and in 15.9% of those in the chemotherapy group (odds ratio, 3.81; 95% CI, 2.44 to 5.94; P<0.001). Overall survival was significantly longer with MIRV than with chemotherapy (median, 16.46 months vs. 12.75 months; hazard ratio for death, 0.67; 95% CI, 0.50 to 0.89; P = 0.005). During the treatment period, fewer adverse events of grade 3 or higher occurred with MIRV than with chemotherapy (41.7% vs. 54.1%), as did serious adverse events of any grade (23.9% vs. 32.9%) and events leading to discontinuation (9.2% vs. 15.9%). CONCLUSIONS: Among participants with platinum-resistant, FRα-positive ovarian cancer, treatment with MIRV showed a significant benefit over chemotherapy with respect to progression-free and overall survival and objective response. (Funded by ImmunoGen; MIRASOL ClinicalTrials.gov number, NCT04209855.).

Insights into the tumor-stromal-immune cell metabolism cross talk in ovarian cancer.

The ovarian cancer tumor microenvironment (TME) consists of a constellation of abundant cellular components, extracellular matrix, and soluble factors. Soluble factors, such as cytokines, chemokines, structural proteins, extracellular vesicles, and metabolites, are critical means of noncontact cellular communication acting as messengers to convey pro- or antitumorigenic signals. Vast advancements have been made in our understanding of how cancer cells adapt their metabolism to meet environmental demands and utilize these adaptations to promote survival, metastasis, and therapeutic resistance. The stromal TME contribution to this metabolic rewiring has been relatively underexplored, particularly in ovarian cancer. Thus, metabolic activity alterations in the TME hold promise for further study and potential therapeutic exploitation. In this review, we focus on the cellular components of the TME with emphasis on 1) metabolic signatures of ovarian cancer; 2) understanding the stromal cell network and their metabolic cross talk with tumor cells; and 3) how stromal and tumor cell metabolites alter intratumoral immune cell metabolism and function. Together, these elements provide insight into the metabolic influence of the TME and emphasize the importance of understanding how metabolic performance drives cancer progression.

Carcinoma-Associated Mesenchymal Stem/Stromal Cells: Architects of the Pro-tumorigenic Tumor Microenvironment.

The interaction between tumor cells and non-malignant hosts cells within the tumor microenvironment (TME) is critical to the pathophysiology of cancer. These non-malignant host cells, consisting of a variety of stromal, immune, and endothelial cells, engage in a complex bidirectional crosstalk with the malignant tumor cells. Mesenchymal stem/stromal cells (MSCs) are one of these host cells, and they play a critical role in directing the formation and function of the entire TME. These MSCs are epigenetically reprogrammed by cancer cells to assume a strongly pro-tumorigenic phenotype and are referred to as carcinoma-associated mesenchymal stem/stromal cells (CA-MSCs). Studies over the last decade demonstrate that CA-MSCs not only directly interact with cancer cells to promote tumor growth and metastasis but also orchestrate the formation of the TME. Carcinoma-associated mesenchymal stem/stromal cells can differentiate into virtually all stromal sub-lineages present in the TME, including pro-tumorigenic cancer-associated fibroblasts (CAF), myofibroblasts, and adipocytes. carcinoma-associated mesenchymal stem/stromal cells and the CAFs they produce, secrete much of the extracellular matrix in the TME. Furthermore, CA-MSC secreted factors promote angiogenesis, and recruit immunosuppressive myeloid cells effectively driving tumor immune exclusion. Thus CA-MSCs impact nearly every aspect of the TME. Despite their influence on cancer biology, as CA-MSCs represent a heterogenous population without a single definitive marker, significant confusion remains regarding the origin and proper identification CA-MSCs. This review will focus on the impact of CA-MSCs on cancer progression and metastasis and the ongoing work on CA-MSC identification, nomenclature and mechanism of action.

Metformin and survival: Is there benefit in a cohort limited to diabetic women with endometrial, breast, or ovarian cancer?

OBJECTIVE: Evaluate the association between metformin and survival in women with Type 2 diabetes (T2DM) and breast, endometrial and ovarian cancer- 3 hormonally mediated cancers. METHODS: We evaluated outcomes in a cohort of 6225 women with T2DM with a new diagnosis of ovarian, breast or endometrial cancer from 2010 to 2019. We classified glycemic medications at time of first cancer diagnosis into 3 tiers in accordance with ADA guidelines. Approaches compared: (i) metformin (tier 1) vs. no glycemic medication, (ii) metformin vs tier 2 medications (sulfonylureas, thiazolidinediones, SGLT2-inhibitors, DPP4-inhibitors, alpha glucosidase-inhibitors, GLP-1 agonists), (iii) metformin vs tier 3 medications (insulins, amylinomimetics), and (iv) tier 2 vs tier 3 medications. Analyses included Cox proportional-hazards models, Kaplan-Meier curves, and conditional logistic regression in a risk set-sampled nested case-control matched on T2DM duration- all modeling survival. Models were adjusted for demographics, cancer type, A1C, T2DM duration, and number of office visits and hospitalizations. RESULTS: Metformin was the most used medication (n = 3232) and consistently demonstrated survival benefit compared with tier 2 and 3 medications, across all methods. Tier 3-users demonstrated highest risk of death when compared to metformin rather than tier 2 [adjHR = 1.83 (95% CI: 1.58, 2.13) vs. adjHR = 1.32 (95% CI: 1.11, 1.57)], despite similar baseline profiles between tier 1 and 2 users. CONCLUSIONS: Metformin users experienced increased survival even after accounting for surrogates of diabetes progression. Benefit extended beyond that seen in tier 2-users. Our findings, consistent with prior studies, indicate metformin use improves survival in women with T2DM and hormonally mediated women's cancers.

Intestinal Radiation Protection and Mitigation by Second-Generation Probiotic Lactobacillus-reuteri Engineered to Deliver Interleukin-22.

(1) Background: The systemic administration of therapeutic agents to the intestine including cytokines, such as Interleukin-22 (IL-22), is compromised by damage to the microvasculature 24 hrs after total body irradiation (TBI). At that time, there is significant death of intestinal microvascular endothelial cells and destruction of the lamina propria, which limits drug delivery through the circulation, thus reducing the capacity of therapeutics to stabilize the numbers of Lgr5+ intestinal crypt stem cells and their progeny, and improve survival. By its direct action on intestinal stem cells and their villus regeneration capacity, IL-22 is both an ionizing irradiation protector and mitigator. (2) Methods: To improve delivery of IL-22 to the irradiated intestine, we gavaged Lactobacillus-reuteri as a platform for the second-generation probiotic Lactobacillus-reuteri-Interleukin-22 (LR-IL-22). (3) Results: There was effective radiation mitigation by gavage of LR-IL-22 at 24 h after intestinal irradiation. Multiple biomarkers of radiation damage to the intestine, immune system and bone marrow were improved by LR-IL-22 compared to the gavage of control LR or intraperitoneal injection of IL-22 protein. (4) Conclusions: Oral administration of LR-IL-22 is an effective protector and mitigator of intestinal irradiation damage.

Ovarian Carcinoma-Associated Mesenchymal Stem Cells Arise from Tissue-Specific Normal Stroma.

Carcinoma-associated mesenchymal stem cells (CA-MSCs) are critical stromal progenitor cells within the tumor microenvironment (TME). We previously demonstrated that CA-MSCs differentially express bone morphogenetic protein family members, promote tumor cell growth, increase cancer "stemness," and chemotherapy resistance. Here, we use RNA sequencing of normal omental MSCs and ovarian CA-MSCs to demonstrate global changes in CA-MSC gene expression. Using these expression profiles, we create a unique predictive algorithm to classify CA-MSCs. Our classifier accurately distinguishes normal omental, ovary, and bone marrow MSCs from ovarian cancer CA-MSCs. Suggesting broad applicability, the model correctly classifies pancreatic and endometrial cancer CA-MSCs and distinguishes cancer associated fibroblasts from CA-MSCs. Using this classifier, we definitively demonstrate ovarian CA-MSCs arise from tumor mediated reprograming of local tissue MSCs. Although cancer cells alone cannot induce a CA-MSC phenotype, the in vivo ovarian TME can reprogram omental or ovary MSCs to protumorigenic CA-MSCs (classifier score of >0.96). In vitro studies suggest that both tumor secreted factors and hypoxia are critical to induce the CA-MSC phenotype. Interestingly, although the breast cancer TME can reprogram bone marrow MSCs into CA-MSCs, the ovarian TME cannot, demonstrating for the first time that tumor mediated CA-MSC conversion is tissue and cancer type dependent. Together these findings (a) provide a critical tool to define CA-MSCs and (b) highlight cancer cell influence on distinct normal tissues providing powerful insights into the mechanisms underlying cancer specific metastatic niche formation. Stem Cells 2019;37:257-269.

Mesenchymal Stem Cells in the Tumor Microenvironment.

The interactions between tumor cells and the non-malignant stromal and immune cells that make up the tumor microenvironment (TME) are critical to the pathophysiology of cancer. Mesenchymal stem cells (MSCs) are multipotent stromal stem cells found within most cancers and play a critical role influencing the formation and function of the TME. MSCs have been reported to support tumor growth through a variety of mechanisms including (i) differentiation into other pro-tumorigenic stromal components, (ii) suppression of the immune response, (iii) promotion of angiogenesis, (iv) enhancement of an epithelial-mesenchymal transition (EMT), (v) enrichment of cancer stem-like cells (CSC), (vi) increase in tumor cell survival, and (vii) promotion of tumor metastasis. In contrast, MSCs have also been reported to have antitumorigenic functions including (i) enhancement of the immune response, (ii) inhibition of angiogenesis, (iii) regulation of cellular signaling, and (iv) induction of tumor cell apoptosis. Although literature supporting both arguments exists, most studies point to MSCs acting in a cancer supporting role within the confines of the TME. Tumor-suppressive effects are observed when MSCs are used in higher ratios to tumor cells. Additionally, MSC function appears to be tissue type dependent and may rely on cancer education to reprogram a naïve MSC with antitumor effects into a cancer-educated or cancer-associated MSC (CA-MSC) which develops pro-tumorigenic function. Further work is required to delineate the complex crosstalk between MSCs and other components of the TME to accurately assess the impact of MSCs on cancer initiation, growth, and spread.

Identifying an ovarian cancer cell hierarchy regulated by bone morphogenetic protein 2.

Whether human cancer follows a hierarchical or stochastic model of differentiation is controversial. Furthermore, the factors that regulate cancer stem-like cell (CSC) differentiation potential are largely unknown. We used a novel microfluidic single-cell culture method to directly observe the differentiation capacity of four heterogeneous ovarian cancer cell populations defined by the expression of the CSC markers aldehyde dehydrogenase (ALDH) and CD133. We evaluated 3,692 progeny from 2,833 cells. We found that only ALDH(+)CD133(+) cells could generate all four ALDH(+/-)CD133(+/-) cell populations and identified a clear branched differentiation hierarchy. We also observed a single putative stochastic event. Within the hierarchy of cells, bone morphologenetic protein 2 (BMP2) is preferentially expressed in ALDH(-)CD133(-) cells. BMP2 promotes ALDH(+)CD133(+) cell expansion while suppressing the proliferation of ALDH(-)CD133(-) cells. As such, BMP2 suppressed bulk cancer cell growth in vitro but increased tumor initiation rates, tumor growth, and chemotherapy resistance in vivo whereas BMP2 knockdown reduced CSC numbers, in vivo growth, and chemoresistance. These data suggest a hierarchical differentiation pattern in which BMP2 acts as a feedback mechanism promoting ovarian CSC expansion and suppressing progenitor proliferation. These results explain why BMP2 suppresses growth in vitro and promotes growth in vivo. Together, our results support BMP2 as a therapeutic target in ovarian cancer.

Carcinoma-associated mesenchymal stem cells promote ovarian cancer heterogeneity and metastasis through mitochondrial transfer.

Ovarian cancer is characterized by early metastatic spread. This study demonstrates that carcinoma-associated mesenchymal stromal cells (CA-MSCs) enhance metastasis by increasing tumor cell heterogeneity through mitochondrial donation. CA-MSC mitochondrial donation preferentially occurs in ovarian cancer cells with low levels of mitochondria ("mito poor"). CA-MSC mitochondrial donation rescues the phenotype of mito poor cells, restoring their proliferative capacity, resistance to chemotherapy, and cellular respiration. Receipt of CA-MSC-derived mitochondria induces tumor cell transcriptional changes leading to the secretion of ANGPTL3, which enhances the proliferation of tumor cells without CA-MSC mitochondria, thus amplifying the impact of mitochondrial transfer. Donated CA-MSC mitochondrial DNA persisted in recipient tumor cells for at least 14 days. CA-MSC mitochondrial donation occurs in vivo, enhancing tumor cell heterogeneity and decreasing mouse survival. Collectively, this work identifies CA-MSC mitochondrial transfer as a critical mediator of ovarian cancer cell survival, heterogeneity, and metastasis and presents a unique therapeutic target in ovarian cancer.

Genetically Engineered Probiotic Limosilactobacillus reuteri Releasing IL-22 (LR-IL-22) Modifies the Tumor Microenvironment, Enabling Irradiation in Ovarian Cancer.

Despite recent advances in cancer therapy, ovarian cancer remains the most lethal gynecological cancer worldwide, making it crucial and of the utmost importance to establish novel therapeutic strategies. Adjuvant radiotherapy has been assessed historically, but its use was limited by intestinal toxicity. We recently established the role of Limosilactobacillus reuteri in releasing IL-22 (LR-IL-22) as an effective radiation mitigator, and we have now assessed its effect in an ovarian cancer mouse model. We hypothesized that an LR-IL-22 gavage would enable intestinal radioprotection by modifying the tumor microenvironment and, subsequently, improving overall survival in female C57BL/6MUC-1 mice with widespread abdominal syngeneic 2F8cis ovarian cancer. Herein, we report that the LR-IL-22 gavage not only improved overall survival in mice when combined with a PD-L1 inhibitor by inducing differential gene expression in irradiated stem cells but also induced PD-L1 protein expression in ovarian cancer cells and mobilized CD8+ T cells in whole abdomen irradiated mice. The addition of LR-IL-22 to a combined treatment modality with fractionated whole abdomen radiation (WAI) and systemic chemotherapy and immunotherapy regimens can facilitate a safe and effective protocol to reduce tumor burden, increase survival, and improve the quality of life of a locally advanced ovarian cancer patient.

Stromal mediated DNA damage promotes high grade serous ovarian cancer initiation.

The fundamental steps in high-grade serous ovarian cancer (HGSOC) initiation are unclear, thus providing critical barriers to the development of prevention or early detection strategies for this deadly disease. Increasing evidence demonstrates most HGSOC starts in the fallopian tube epithelium (FTE). Current models propose HGSOC initiates when FTE cells acquire increasing numbers of mutations allowing cells to evolve into serous tubal intraepithelial carcinoma (STIC) precursors and then to full blown cancer. Here we report that epigenetically altered mesenchymal stem cells (termed high risk MSC-hrMSCs) can be detected prior to the formation of ovarian cancer precursor lesions. These hrMSCs drive DNA damage in the form of DNA double strand breaks in FTE cells while also promoting the survival of FTE cells in the face of DNA damage. Indicating the hrMSC may actually drive cancer initiation, we find hrMSCs induce full malignant transformation of otherwise healthy, primary FTE resulting in metastatic cancer in vivo . Further supporting a role for hrMSCs in cancer initiation in humans, we demonstrate that hrMSCs are highly enriched in BRCA1/2 mutation carriers and increase with age. Combined these findings indicate that hrMSCs may incite ovarian cancer initiation. These findings have important implications for ovarian cancer detection and prevention.

Alternative splice variants of the mitochondrial fission protein DNM1L/Drp1 regulate mitochondrial dynamics and tumor progression in ovarian cancer.

Aberrant mitochondrial fission/fusion dynamics have been reported in cancer cells. While post translational modifications are known regulators of the mitochondrial fission/fusion machinery, we show that alternative splice variants of the fission protein Drp1 (DNM1L) have specific and unique roles in cancer, adding to the complexity of mitochondrial fission/fusion regulation in tumor cells. Ovarian cancer specimens express an alternative splice transcript variant of Drp1 lacking exon 16 of the variable domain, and high expression of this splice variant relative to other transcripts is associated with poor patient outcome. Unlike the full-length variant, expression of Drp1 lacking exon 16 leads to decreased association of Drp1 to mitochondrial fission sites, more fused mitochondrial networks, enhanced respiration, and TCA cycle metabolites, and is associated with a more metastatic phenotype in vitro and in vivo. These pro-tumorigenic effects can also be inhibited by specific siRNA-mediated inhibition of the endogenously expressed transcript lacking exon 16. Moreover, lack of exon 16 abrogates mitochondrial fission in response to pro-apoptotic stimuli and leads to decreased sensitivity to chemotherapeutics. These data emphasize the significance of the pathophysiological consequences of Drp1 alternative splicing and divergent functions of Drp1 splice variants, and strongly warrant consideration of Drp1 splicing in future studies.

Stromal-Modulated Epithelial-to-Mesenchymal Transition in Cancer Cells.

The ability of cancer cells to detach from the primary site and metastasize is the main cause of cancer- related death among all cancer types. Epithelial-to-mesenchymal transition (EMT) is the first event of the metastatic cascade, resulting in the loss of cell-cell adhesion and the acquisition of motile and stem-like phenotypes. A critical modulator of EMT in cancer cells is the stromal tumor microenvironment (TME), which can promote the acquisition of a mesenchymal phenotype through direct interaction with cancer cells or changes to the broader microenvironment. In this review, we will explore the role of stromal cells in modulating cancer cell EMT, with particular emphasis on the function of mesenchymal stromal/stem cells (MSCs) through the activation of EMT-inducing pathways, extra cellular matrix (ECM) remodeling, immune cell alteration, and metabolic rewiring.

Release of Interferon-ß (IFN-ß) from Probiotic Limosilactobacillus reuteri-IFN-ß (LR-IFN-ß) Mitigates Gastrointestinal Acute Radiation Syndrome (GI-ARS) following Whole Abdominal Irradiation.

Irradiation can be an effective treatment for ovarian cancer, but its use is limited by intestinal toxicity. Thus, strategies to mitigate toxicity are important and can revitalize the current standard of care. We previously established that LR-IL-22 protects the intestine from WAI. We now hypothesize that LR-IFN-ß is an effective radiation protector and mitigator and is rapidly cleared from the digestive tract, making it an option for intestinal radioprotection. We report that the gavage of LR-IFN-ß during WAI provides improved intestinal barrier integrity and significantly preserves the numbers of Lgr5+GFP+ intestinal stem cells, improving survival. The rapid clearance of the genetically engineered probiotic from the digestive tract renders it a safe and feasible radiation mitigator. Therefore, the above genetically engineered probiotic is both a feasible and effective radiation mitigator that could potentially revolutionize the management of OC patients. Furthermore, the subsequent addition of platinum/taxane-based chemotherapy to the combination of WAI and LR-IFN-ß should reduce tumor volume while protecting the intestine and should improve the overall survival in OC patients.

Regulatory effects of ferritin on angiogenesis.

Angiogenesis, the synthesis of new blood vessels from preexisting vessels, plays a critical role in normal wound healing and tumor growth. HKa (cleaved high molecular weight kininogen) is an endogenous inhibitor of angiogenesis formed by the cleavage of kininogen on endothelial cells. Ferritin is a protein principally known for its central role in iron storage. Here, we demonstrate that ferritin binds to HKa with high affinity (K(d) 13 nM). Further, ferritin antagonizes the antiangiogenic effects of HKa, enhancing the migration, assembly, and survival of HKa-treated endothelial cells. Effects of ferritin were independent of its iron content. Peptide mapping revealed that ferritin binds to a 22-aa subdomain of HKa that is critical to its antiangiogenic activity. In vivo, ferritin opposed HKa's antiangiogenic effects in a human prostate cancer xenograft, restoring tumor-dependent vessel growth. Ferritin-mediated regulation of angiogenesis represents a new angiogenic regulatory pathway, and identifies a new role for ferritin in cell biology.

Novel Therapies in Gynecologic Cancer.

During the past decade, considerable strides have been made in the understanding and treatment of gynecologic cancers. The advent of PARP inhibitors, antiangiogenic therapies, immunotherapy combinations, and targeted agents have altered the standard of care in ovarian, endometrial, and cervical cancers. However, continued advancement in the treatment of gynecologic cancers is critical. Fortunately, exciting work defining new therapeutic targets and novel treatment strategies is on the horizon. Here, we discuss emerging treatments for gynecologic cancers, including endometrial, cervical, ovarian, and rare gynecologic cancers. We highlight research that has deepened our understanding of the unique biology and molecular underpinnings of these cancers and is being translated into powerful new treatment approaches. We particularly highlight the advent of immunotherapy in endometrial cancer; radiosensitizers in cervical, vaginal, and vulvar cancers; targeted therapies in ovarian cancer; and molecularly driven approaches to treat rare gynecologic cancers. Continued basic, translational, and clinical research holds the promise to change the landscape of gynecologic cancer and improve the lives of all women impacted by these diseases.

Shifting the Soil: Metformin Treatment Decreases the Protumorigenic Tumor Microenvironment in Epithelial Ovarian Cancer.

Controversy persists regarding metformin's role in cancer therapy. Our recent work suggested metformin acts by impacting the tumor microenvironment (TME), normalizing the epigenetic profile of cancer-associated mesenchymal stem cells (CA-MSC). As CA-MSC can negatively impact tumor immune infiltrates, we evaluated metformin's impact on the human TME, focusing on the interplay of stroma and immune infiltrates. Tumor samples from (i) 38 patients treated with metformin and chemotherapy and (ii) 44 non-metformin matched controls were included in a tissue microarray (TMA). The TMA was used to compare the presence of CA-MSC, desmoplasia and immune infiltrates in the TME. In vitro and in vivo models examined metformin's role in alteration of the CA-MSC phenotype. The average percentage of CA-MSC was significantly lower in metformin-treated than in chemotherapy alone-treated tumors (p = 0.006). There were fewer regulatory T-cells in metformin-treated tumors (p = 0.043). Consistent with CA-MSC's role in excluding T-cells from tumor islets, the T-cells were primarily present within the tumor stroma. Evaluation of metformin's impact in vitro suggested that metformin cannot reverse a CA-MSC phenotype; however, the in vivo model where metformin was introduced prior to the establishment of the CA-MSC phenotype supported that metformin can partially prevent the reprogramming of normal MSC into CA-MSC. Metformin treatment led to a decrease in both the presence of protumorigenic CA-MSC and in immune exclusion of T cells, leading to a more immune-permissive environment. This suggests clinical utility in prevention and in treatment for early-stage disease and putatively in immune therapy.

Endometriosis-Associated Mesenchymal Stem Cells Support Ovarian Clear Cell Carcinoma through Iron Regulation.

Ovarian clear cell carcinoma (OCCC) is a deadly and treatment-resistant cancer, which arises within the unique microenvironment of endometriosis. In this study, we identified a subset of endometriosis-derived mesenchymal stem cells (enMSC) characterized by loss of CD10 expression that specifically support OCCC growth. RNA sequencing identified alterations in iron export in CD10-negative enMSCs and reciprocal changes in metal transport in cocultured OCCC cells. CD10-negative enMSCs exhibited elevated expression of iron export proteins hephaestin and ferroportin and donate iron to associated OCCCs, functionally increasing the levels of labile intracellular iron. Iron is necessary for OCCC growth, and CD10-negative enMSCs prevented the growth inhibitory effects of iron chelation. In addition, enMSC-mediated increases in OCCC iron resulted in a unique sensitivity to ferroptosis. In vitro and in vivo, treatment with the ferroptosis inducer erastin resulted in significant death of cancer cells grown with CD10-negative enMSCs. Collectively, this work describes a novel mechanism of stromal-mediated tumor support via iron donation. This work also defines an important role of endometriosis-associated MSCs in supporting OCCC growth and identifies a critical therapeutic vulnerability of OCCC to ferroptosis based on stromal phenotype. SIGNIFICANCE: Endometriosis-derived mesenchymal stem cells support ovarian clear cell carcinoma via iron donation necessary for cancer growth, which also confers sensitivity to ferroptosis-inducing therapy.

Clinical factors associated with failed sentinel lymph node mapping in endometrial cancer.

Objective: Sentinel lymph node (SLN) mapping is a highly accurate surgical technique for detecting metastases in endometrial cancer. The objective of this study was to identify clinical factors associated with failed mapping. Methods: All patients with endometrial cancer undergoing minimally-invasive staging and planned SLN biopsy from 1/1/2017 to 12/31/2020 at a single institution were identified retrospectively. Demographic, clinicopathologic and treatment data were obtained. Data were compared using descriptive statistics. Univariate and multivariable logistic regression were performed to identify predictors of failed mapping. Results: 819 patients were identified with a mean age of 64.6 years (range 26-93) and mean BMI of 35.6 kg/m2 (range 18-68). Most (88.5 %, 725/819) had early-stage disease and endometrioid histology (82.3 %, 674/819). A majority (74.2 %, 608/819) had successful bilateral mapping, and 54 (6.6 %) had unsuccessful bilateral mapping. Increasing BMI was significantly associated with unsuccessful bilateral mapping: patients with BMI > 30 were more likely to have unsuccessful SLN mapping (p = 0.033). Among patients with known lymph node status (799/819), patients with macrometastases and micrometastases were more likely to have failed bilateral mapping compared to those with negative SLNs or isolated tumor cells (p = 0.013). On multivariable analysis, higher BMI and histology were associated with failed bilateral mapping (OR = 1.023, 95 % CI (1.005, 1.041) and OR = 1.678, 95 % CI (1.177, 2.394), respectively). Conclusion: SLN mapping has a high success in patients undergoing minimally-invasive surgical staging for endometrial cancer. Increasing BMI, high risk histology, and lymph node metastases are risk factors for failed mapping.