Protocol for the isolation of tumor cell-derived extracellular vesicles followed by in vivo metastasis assessment in a murine ovarian cancer model

Extracellular vesicles (EVs) play a crucial role in facilitating communication between cancer cells and their immediate or remote microenvironments, thereby promoting the extensive spread of cancer throughout the body. In this context, we present a protocol for the isolation of tumor cell-derived EVs followed by in vivo metastasis assessment in a murine ovarian cancer model. We describe steps for the isolation and characterization of EVs from ID8 cells, development of a metastatic mouse model, and sample preparation for flow cytometry. For complete details on the use and execution of this protocol, please refer to Gupta et al.1.

Preclinical activity of selinexor in combination with eribulin in uterine leiomyosarcoma

Leiomyosarcoma (LMS) is a rare soft tissue sarcoma (STS) that begins in smooth muscle tissue and most often initiates in the abdomen or uterus. Compared with other uterine cancers, uterine LMS (ULMS) is an aggressive tumor with poor prognosis and a high risk of recurrence and death, regardless of the stage at presentation. Selinexor is a first-in-class selective inhibitor of nuclear export (SINE) compound that reversibly binds to exportin 1 (XPO1), thereby reactivating tumor suppressor proteins and downregulating the expression of oncogenes and DNA damage repair (DDR) proteins. In this study, we evaluated the effects of selinexor in combination with doxorubicin and eribulin in the LMS tumor model in vitro and in vivo. Treatment of selinexor combined with eribulin showed synergistic effects on tumor growth inhibition in SK-UT1 LMS-derived xenografts. Immunohistochemical assessment of the tumor tissues showed a significantly reduced expression of proliferation (Ki67) and XPO1 markers following combination therapy compared to the control group. Global transcriptome analyses on tumor tissue revealed that the combination therapy regulates genes from several key cancer-related pathways that are differentially expressed in ULMS tumors. To our knowledge, this is the first preclinical study demonstrating the anti-cancer therapeutic potential of using a combination of selinexor and eribulin in vivo. Results from this study further warrant clinical testing a combination of chemotherapy agents with selinexor to reduce the morbidity and mortality from ULMS.

Abstract 1463: Fxr1 is an oncogenic driver in ovarian cancer

Introduction: Ovarian cancer is primarily driven by copy number variations, mutations in p53, BRCA1 or BRCA2 genes. Using the single nucleotide polymorphism (SNP) array data of The Cancer Genome Atlas (TCGA), we identified that FXR1 (Fragile X-Related protein 1), which is in the 3q26.3 chromosomal locus is either amplified or copy-gained in ~40% of ovarian cancer patients. As FXR1 plays a critical role in the pathogenesis of ovarian cancer, it is thought to be an attractive target for anticancer drugs. Nevertheless, till date, no specific chemical inhibitors are available that can target FXR1. Therefore, the goal of this study is to develop an agent that can knockdown the expression of FXR1.

Methods: We performed Surface sensing of translation (SUnSET) assay to demonstrate that FXR1 enhances the overall translation in cancer cells. RNA electromobility shift and proximity ligation assays were done to show that FXR1 binds to the AU Rich Elements (ARE) present within the 3'UTR of cMYC. Immunoprecipitation assay was performed to show interaction of FXR1 with translation initiation factors (eIFs). Western blotting was performed to evaluate the target specificity of customized FXR1-specific siRNAs FXR1. Flow cytometry analysis was then performed to see cell death and cell cycle arrest in ovarian cancer cells after siFXR1s (1-5) treatment. Live cell immunofluorescence was done to measure cellular uptake of siFXR1 labelled with Texas Red in cells. FXR1-specific siRNA incorporated DOPC was injected as 5 μg (200 μL) intraperitoneally twice a week starting 1 week after inoculation of cancer cells. The IVIS Lumina II Bioluminescence and Fluorescence Imaging System was used for in vivo bioluminescent imaging.

Results: Our previous data suggest that FXR1 is an important oncoprotein and has critical roles in the pathophysiology of ovarian cancer. We also found that FXR1 promoted the overall translation in cancer cells, which is a critical feature for oncogenesis. Our mechanistic investigation provided evidence that FXR1 upregulated cMYC protein levels by stabilizing cMYC mRNA via binding to AREs within its 3′UTR. We also found that FXR1 recruits eIFs to the translation initiation site. In our therapeutic approaches, we found that custom designed siRNAs against FXR1 shows maximum potency in reducing the FXR1 protein levels, induces G1-phase of cell cycle and apoptosis in ovarian cancer cells. Importantly, intraperitoneally delivery of siFXR1 incorporated in DOPC nanoliposomes inhibited ovarian tumor growth and prolonged survival of ovarian cancer bearing mice.

Conclusion: Our studies have identified that FXR1 is a critical molecule that is important for ovarian cancer progression. We discovered that cMYC is an important target of FXR1 required for FXR1-mediated oncogenesis. Moreover, DOPC encapsulation enhances the siFXR1 uptake, stability, efficiency of cellular delivery, biodistribution, and target-specific knockdown in vivo.

Citation Format: Jasmine George, Ishaque P. Kadamberi, Anjali Geethadevi, Sudhir Kumar, Sonam Mittal, Cristian Rodriguez-Aguayo, Lingegowda S. Mangala, Anil K. Sood, Sunila Pradeep, Pradeep Chaluvally-Raghavan. Fxr1 is an oncogenic driver in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1463.

Abstract 2321: Tumor-derived extracellular vesicles induce macrophages immunosuppressive polarization to promote ovarian cancer progression

Background: Communication between cancer cells and surrounding cells in the tumor microenvironment (TME) is critical for tumor metastasis. There has been an increasing focus on how tumor-derived extracellular vesicles (EVs) contribute to the complex intracellular communications within the TME. More recent characterizations in both mice and humans have demonstrated that expression of the immune checkpoint molecule, programmed death ligand-1 (PD-L1) on EVs contributes to systemic immunosuppression, higher overall tumor burdens, and decreased survival of a variety of cancer types. In ovarian carcinoma, macrophages are reprogrammed toward pro-tumorigenic phenotypes, including the release of anti-inflammatory cytokines and expression of immunosuppressive molecules such as arginase-1 and PD-L1. However, a detailed mechanism that explains how tumor-derived EVs induce immunosuppressive phenotype in macrophages is necessary to develop novel immunotherapy strategies for advanced ovarian cancer treatment. The present study aimed to examine the effect of EVs derived from ovarian cancer cells on macrophage functions.

Methods: We isolated murine peritoneal macrophages from naïve C57BL/6 female mice and co-cultured the macrophages with EVs derived from ovarian cancer (ID8-Trp53-/-Brca2-/-) cell lines. The expression of PD-L1, CD206, interleukin-6 (IL-6), and other inflammatory cytokines on EVs treated macrophages was evaluated using flow cytometry and a cytokine array kit. Further, we created Rab27aKO ID8 cell lines to generate ovarian cancer in vivo mouse models for studying the effect of exogenous EVs on the immunosuppressive ability of macrophages and tumor progression.

Results: Our results indicate that EVs uptake efficiency of macrophages is higher than fibroblast, endothelial, and mesothelial cells. We found that tumor-derived EVs can significantly upregulate the expressions of PD-L1, CD206, and IL-6 on macrophages to support tumor growth. Treatment of macrophages with EVs also decreased their phagocytic ability. In addition, our data show that in the Rab27aKO ovarian cancer in vivo mouse model, intravenous injection of tumor-derived EVs increased the tumor burden, metastasis, and ascites accumulation as compared to PBS control. EVs treatment increased the infiltration of tumor-associated macrophages (TAM) in ascites. We also found increased expression of PD-L1 and CD206 on TAM isolated from ascites.

Conclusion: We uncover a tumor-promoting role of ovarian cancer-derived EVs on reprogramming TAM towards pro-tumor phenotype. Our data suggest that tumor-derived EVs contribute to the formation of an immunosuppressive microenvironment to promote ovarian cancer growth.

Citation Format: Sonam Mittal, Ishaque Pulikkal Kadamberi, Prachi Gupta, Sudhir Kumar, Jasmine George, Anjali Geethadevi, Pradeep Chaluvally-Raghavan, Sunila Pradeep. Tumor-derived extracellular vesicles induce macrophages immunosuppressive polarization to promote ovarian cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2321.

Fluorinated triphenylphosphonium analogs improve cell selectivity and in vivo detection of mito-metformin

Triphenylphosphonium (TPP⁺) conjugated compounds selectively target cancer cells by exploiting their hyperpolarized mitochondrial membrane potential. To date, studies have focused on modifying either the linker or the cargo of TPP⁺-conjugated compounds. Here, we investigated the biological effects of direct modification to TPP⁺ to improve the efficacy and detection of mito-metformin (MMe), a TPP⁺-conjugated probe we have shown to have promising preclinical efficacy against solid cancer cells. We designed, synthesized, and tested trifluoromethyl and methoxy MMe analogs (pCF₃-MMe, mCF₃-MMe, and pMeO-MMe) against multiple distinct human cancer cells. pCF₃-MMe showed enhanced selectivity toward cancer cells compared to MMe, while retaining the same signaling mechanism. Importantly, pCF₃-MMe allowed quantitative monitoring of cellular accumulation via ¹⁹F-NMR in vitro and in vivo. Furthermore, adding trifluoromethyl groups to TPP⁺ reduced toxicity in vivo while retaining anti-tumor efficacy, opening an avenue to de-risk these next-generation TPP⁺-conjugated compounds.

Extracellular vesicle contents as non-invasive biomarkers in ovarian malignancies

Ovarian cancer most commonly presents at an advanced stage where survival is approximately 30% compared with >80% if diagnosed and treated before disease spreads. Diagnostic capabilities have progressed from surgical staging via laparotomy to image-guided biopsies and immunohistochemistry staining, along with advances in technology and medicine. Despite improvements in diagnostic capabilities, population-level screening for ovarian cancer is not recommended. Extracellular vesicles (EVs) are 40–150 nm structures formed when the cellular lipid bilayer invaginates. These structures function in cell signaling, immune responses, cancer progression, and establishing the tumor microenvironment. EVs are found in nearly every bodily fluid, including serum, plasma, ascites, urine, and effusion fluid, and contain molecular cargo from their cell of origin. This cargo can be analyzed to yield information about a possible malignancy. In this review we describe how the cargo of EVs has been studied as biomarkers in ovarian cancer. We bring together studies analyzing evidence for various cargos as ovarian cancer biomarkers. Then, we describe the role of EVs in modulation of the tumor microenvironment. This review also summarizes the therapeutic and translational potential of EVs for their optimal utilization as non-invasive biomarkers for novel treatments against cancer.

Optimized proximity ligation assay (PLA) for detection of RNA-protein complex interactions in cell lines

Conventional proximity ligation assay (PLA) suffers from target specificity issues that curtail their accuracy on interpreting proximal interactions in cell biology. Here, we present a reliable and sensitive approach by including a fluorochrome-labeled mRNA fragment along with biotin-labeled RNA probe and a target-specific antibody, which were used to generate proximal ligation signals through linear connectors in intact cells. This protocol will be particularly useful for studying the proximal interactions between RNA binding proteins (RBPs) and their target mRNAs in cells.

For complete details on the use and execution of this protocol, please refer to George et al. (2021).

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FXR1 binds to the AU-rich elements (ARE) within cMYC 3′UTR

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Use of fluorescence-labeled mRNA improves the specificity of PLA reaction

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Linear connectors linked to the probes produce high levels of PLA signals

Patient-Derived Ovarian Cancer Spheroids Rely on PI3K-AKT Signaling Addiction for Cancer Stemness and Chemoresistance

Simple Summary

Epithelial ovarian cancer (EOC) is the most fatal gynecological cancer with poor survival rates and high mortality. EOC patients respond to standard platinum-based chemotherapy in the beginning, but relapse often due to chemoresistance. Ovarian cancer cells disseminate from the ovarian tumors and spread within the abdomen, where ascites fluid supports the growth and transition. Malignant ascites is present in a third of patients at diagnosis and is considered as a major source of chemoresistance, recurrence, poor survival, and mortality. Malignant ascites is a complex fluid that contains a pro-tumorigenic environment with disseminated cancer cells in 3D spheroids form. In this study, we established an ovarian cancer cell line and identified that 3D spheroids develop from the 2D monolayer, and the platinum-resistant phenotype develops due to the aberrant PI3K-AKT signaling in tumor cells. Furthermore, when we used a combinatorial approach of cisplatin with LY-294002 (a PI3K-AKT dual kinase inhibitor) to treat the cisplatin version of both MCW-OV-SL-3 and A-2780 cell lines, it prevented the 3D spheroid formation ability and also sensitized the cells for cisplatin. In brief, our results provided evidence to advance therapeutic approaches to treat cisplatin resistance in ovarian cancer patients.

Abstract

Ovarian cancer is the most lethal gynecological malignancy among women worldwide and is characterized by aggressiveness, cancer stemness, and frequent relapse due to resistance to platinum-based therapy. Ovarian cancer cells metastasize through ascites fluid as 3D spheroids which are more resistant to apoptosis and chemotherapeutic agents. However, the precise mechanism as an oncogenic addiction that makes 3D spheroids resistant to apoptosis and chemotherapeutic agents is not understood. To study the signaling addiction mechanism that occurs during cancer progression in patients, we developed an endometrioid subtype ovarian cancer cell line named ‘MCW-OV-SL-3’ from the ovary of a 70-year-old patient with stage 1A endometrioid adenocarcinoma of the ovary. We found that the cell line MCW-OV-SL-3 exhibits interstitial duplication of 1q (q21–q42), where this duplication resulted in high expression of the PIK3C2B gene and aberrant activation of PI3K-AKT-ERK signaling. Using short tandem repeat (STR) analysis, we demonstrated that the cell line exhibits a unique genetic identity compared to existing ovarian cancer cell lines. Notably, the MCW-OV-SL-3 cell line was able to form 3D spheroids spontaneously, which is an inherent property of tumor cells when plated on cell culture dishes. Importantly, the tumor spheroids derived from the MCW-OV-SL-3 cell line expressed high levels of c-Kit, PROM1, ZEB1, SNAI, VIM, and Twist1 compared to 2D monolayer cells. We also observed that the hyperactivation of ERK and PI3K/AKT signaling in these cancer cells resulted in resistance to cisplatin. In summary, the MCW-OV-SL3 endometrioid cell line is an excellent model to study the mechanism of cancer stemness and chemoresistance in endometrioid ovarian cancer.

Establishment of In Vivo Ovarian Cancer Mouse Models Using Intraperitoneal Tumor Cell Injection

Mouse models-xenograft models, syngeneic models (directly implanted or chemically or virally induced), and genetically engineered mice (including transgenic and knockout methods) are invaluable for preclinical studies of ovarian cancer as they recapitulate the structures and microenvironments of tumors, which in vitro studies are unable to accomplish.This chapter describes the methodology and approaches for generating various murine models currently employed in ovarian cancer research. It covers the implantation of cells from ovarian cancer cell lines into mice by intraperitoneal injection.

RNA-binding protein FXR1 drives cMYC translation by recruiting eIF4F complex to the translation start site

Fragile X-related protein-1 (FXR1) gene is highly amplified in patients with ovarian cancer, and this amplification is associated with increased expression of both FXR1 mRNA and protein. FXR1 expression directly associates with the survival and proliferation of cancer cells. Surface sensing of translation (SUnSET) assay demonstrates that FXR1 enhances the overall translation in cancer cells. Reverse-phase protein array (RPPA) reveals that cMYC is the key target of FXR1. Mechanistically, FXR1 binds to the AU-rich elements (ARE) present within the 3' untranslated region (3'UTR) of cMYC and stabilizes its expression. In addition, the RGG domain in FXR1 interacts with eIF4A1 and eIF4E proteins. These two interactions of FXR1 result in the circularization of cMYC mRNA and facilitate the recruitment of eukaryotic translation initiation factors to the translation start site. In brief, we uncover a mechanism by which FXR1 promotes cMYC levels in cancer cells.

Oncostatin M Receptor-targeted antibodies suppress STAT3 signaling and inhibit ovarian cancer growth

While patients with advanced ovarian cancer may respond initially to treatment, disease relapse is common and nearly 50% of patients do not survive beyond five years, indicating an urgent need for improved therapies. To identify new therapeutic targets, we performed single cell and nuclear RNA-seq dataset analyses on 17 human ovarian cancer specimens, revealing the oncostatin M receptor (OSMR) as highly expressed in ovarian cancer cells. Conversely, oncostatin M (OSM), the ligand of OSMR, was highly expressed by tumor-associated macrophages and promoted proliferation and metastasis in cancer cells. Ovarian cancer cell lines and additional patient samples also exhibited elevated levels of OSMR when compared to other cell types in the tumor microenvironment or to normal ovarian tissue samples. OSMR was found to be important for ovarian cancer cell proliferation and migration. Binding of OSM to OSMR caused OSMR-IL6ST dimerization, which is required to produce oncogenic signaling cues for prolonged STAT3 activation. Human monoclonal antibody clones B14 and B21 directed to the extracellular domain of OSMR abrogated OSM-induced OSMR-IL6ST heterodimerization, promoted the internalization and degradation of OSMR, and effectively blocked OSMR-mediated signaling in vitro. Importantly, these antibody clones inhibited the growth of ovarian cancer cells in vitro and in vivo by suppressing oncogenic signaling through OSMR and STAT3 activation. Collectively, this study provides a proof of principle that anti-OSMR antibody can mediate disruption of OSM-induced OSMR-IL6ST dimerization and oncogenic signaling, thus documenting the pre-clinical therapeutic efficacy of human OSMR antagonist antibodies for immunotherapy in ovarian cancer.

Targeted biologic inhibition of both tumor cell-intrinsic and intercellular CLPTM1L/CRR9-mediated chemotherapeutic drug resistance

Recurrence of therapy-resistant tumors is a principal problem in solid tumor oncology, particularly in ovarian cancer. Despite common complete responses to first line, platinum-based therapies, most women with ovarian cancer recur, and eventually, nearly all with recurrent disease develop platinum resistance. Likewise, both intrinsic and acquired resistance contribute to the dismal prognosis of pancreatic cancer. Our previous work and that of others has established CLPTM1L (cleft lip and palate transmembrane protein 1-like)/CRR9 (cisplatin resistance related protein 9) as a cytoprotective oncofetal protein that is present on the tumor cell surface. We show that CLPTM1L is broadly overexpressed and accumulated on the plasma membrane of ovarian tumor cells, while weakly or not expressed in normal tissues. High expression of CLPTM1L is associated with poor outcome in ovarian serous adenocarcinoma. Robust re-sensitization of resistant ovarian cancer cells to platinum-based therapy was achieved using human monoclonal biologics inhibiting CLPTM1L in both orthotopic isografts and patient-derived cisplatin resistant xenograft models. Furthermore, we demonstrate that in addition to cell-autonomous cytoprotection by CLPTM1L, extracellular CLPTM1L confers resistance to chemotherapeutic killing in an ectodomain-dependent fashion, and that this intercellular resistance mechanism is inhibited by anti-CLPTM1L biologics. Specifically, exosomal CLPTM1L from cisplatin-resistant ovarian carcinoma cell lines conferred resistance to cisplatin in drug-sensitive parental cell lines. CLPTM1L is present in extracellular vesicle fractions of tumor culture supernatants and in patients' serum with increasing abundance upon chemotherapy treatment. These findings have encouraging implications for the use of anti-CLPTM1L targeted biologics in the treatment of therapy-resistant tumors.

Emerging Role of Extracellular Vesicles in Immune Regulation and Cancer Progression

Simple Summary

Accumulating evidence has reported that extracellular vesicles secreted by different tumor microenvironment cells can interfere with the host immune system. These vesicles transmit the signals in the tumor microenvironment that affect the proliferation, apoptosis, activation, and, metabolism of immune cells such as dendritic cells, T cells, macrophages, and natural killer cells, creating a pro-tumoral environment for tumor progression and survival. In this review, we summarize the recent literature on the function of extracellular vesicles derived from tumor cells and immune cells in regulating the critical processes associated with cancer progression. Besides, we also provide insights on how the extracellular vesicles are employed as diagnostic and prognostic biomarkers and drug carriers in cancer.

Abstract

The development of effective therapies for cancer treatment requires a better understanding of the tumor extracellular environment and a dynamic interaction between tumor cells, the cells of the immune system, and the tumor stroma. Increasing evidence suggests that extracellular vesicles play an important role in this interaction. Extracellular vesicles are nanometer-sized membrane-bound vesicles secreted by various types of cells that facilitate intracellular communication by transferring proteins, various lipids, and nucleic acids, especially miRNAs, between cells. Extracellular vesicles play discrete roles in the immune regulatory functions, such as antigen presentation, and activation or suppression of immune cells. Achieving therapeutic intervention through targeting of extracellular vesicles is a crucial area of research now. Thus, a deeper knowledge of exosome biology and the molecular mechanism of immune regulation is likely to provide significant insight into therapeutic intervention utilizing extracellular vesicles to combat this dreadful disease. This review describes the recent updates on immune regulation by extracellular vesicles in cancer progression and possible use in cancer therapy.

Peritoneal Spread of Ovarian Cancer Harbors Therapeutic Vulnerabilities Regulated by FOXM1 and EGFR/ERBB2 Signaling

Peritoneal spread is the primary mechanism of metastasis of ovarian cancer, and survival of ovarian cancer cells in the peritoneal cavity as nonadherent spheroids and their adherence to the mesothelium of distant organs lead to cancer progression, metastasis, and mortality. However, the mechanisms that govern this metastatic process in ovarian cancer cells remain poorly understood. In this study, we cultured ovarian cancer cell lines in adherent and nonadherent conditions in vitro and analyzed changes in mRNA and protein levels to identify mechanisms of tumor cell survival and proliferation in adherent and nonadherent cells. EGFR or ERBB2 upregulated ZEB1 in nonadherent cells, which caused resistance to cell death and increased tumor-initiating capacity. Conversely, Forkhead box M1 (FOXM1) was required for the induction of integrin β1, integrin-α V, and integrin-α 5 for adhesion of cancer cells. FOXM1 also upregulated ZEB1, which could act as a feedback inhibitor of FOXM1, and caused the transition of adherent cells to nonadherent cells. Strikingly, the combinatorial treatment with lapatinib [dual kinase inhibitor of EGFR (ERBB1) and ERBB2] and thiostrepton (FOXM1 inhibitor) reduced growth and peritoneal spread of ovarian cancer cells more effectively than either single-agent treatment in vivo. In conclusion, these results demonstrate that FOXM1 and EGFR/ERBB2 pathways are key points of vulnerability for therapy to disrupt peritoneal spread and adhesion of ovarian cancer cells. SIGNIFICANCE: This study describes the mechanism exhibited by ovarian cancer cells required for adherent cell transition to nonadherent form during peritoneal spread and metastasis. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/24/5554/F1.large.jpg.

ERBB3-induced furin promotes the progression and metastasis of ovarian cancer via the IGF1R/STAT3 signaling axis

High-grade serous carcinoma, accounts for up to 70% of all ovarian cases. Furin, a proprotein convertase, is highly expressed in high-grade serous carcinoma of ovarian cancer patients, and its expression is even higher in tumor omentum than in normal omentum, the preferred site of ovarian cancer metastasis. The proteolytic actions of this cellular endoprotease helps the maturation of several important precursors of protein substrates and its levels increase the risk of several cancer. We show that furin activates the IGF1R/STAT3 signaling axis in ovarian cancer cells. Conversely, furin knockdown downregulated IGF1R-β and p-STAT3 (Tyr705) expression. Further, silencing furin reduced tumor cell migration and invasion in vitro and tumor growth and metastasis in vivo. Collectively, our findings show that furin can be an effective therapeutic target for ovarian cancer prevention or treatment.

Abstract 206: miR551b-mediated tumor-specific angiogenesis in ovarian cancer

Background: Ovarian cancer is the most lethal gynecological cancer. Tumor angiogenesis is essential for the progression and metastasis of ovarian cancer. Our data shows that STAT3, HIF-1α and VEGFA are the key regulators of tumor-specific angiogenesis. Our studies have provided evidence that VEGF is directly regulated by STAT3 in miR551b-3p expressing cells, which indicates that STAT3 is an important regulator of angiogenesis in a subset of ovarian cancers. Recently, we showed that miR551b-3p acts as an upstream regulator of STAT3 in ovarian cancer cells. We identified that anti-miR551b-3p inhibit the expression of miR551b-3p disrupt tumor-specific angiogenesis by preventing the expression of HIF-1α and VEGFA through direct inhibition of STAT3.

Methods: In this study, we explored the role of miR551b on angiogenesis in ovarian cancer cells by performing cell proliferation, western blot and qPCR of angiogenic markers, in vitro capillary tube formation, in vivo matrigel plug assay and ex-vivo aortic ring assays.

Results: We found that miR551b-3p upregulates STAT3, HIF-1α, VEGFR and VEGF in ovarian cancer cells and increases the abilities of cell proliferation, migration and tube formation of human umbilical vein endothelial (HUVEC) cells. In conjunction, knockdown of miR-551b decreased the level of STAT3, HIF-1α and VEGFR2 proteins as well as the angiogenic activity; also increased cellular apoptosis. Altogether, our data suggest critical roles of miR-551b on STAT-3–mediated angiogenesis in ovarian cancer cells. In complement to our in vitro results, the delivery of anti-miR551b inhibited angiogenesis in the matrigel plug injected in nude mice. Furthermore, the treatment of anti-miR551b reduced the angiogenic sprouting from rat thoracic aorta in our ex vivo culture. Taken together, our findings provide the first evidence that miR-551b is a pivotal regulator of tumor angiogenesis and inhibiting miR551b could be used to inhibit tumor-specific angiogenesis in ovarian cancer.

Conclusions: miR551b markedly augmented the pro-angiogenic effects in vitro, in vivo and ex-vivo models. Our data suggest that miR551b is an actionable target to disrupt tumor-specific angiogenesis in ovarian cancer. In our pre-clinical model, we are using anti-miR551b encapsulated in nanoliposomes for in vivo delivery to inhibit and sensitize anti- angiogenic therapy and chemotherapy. We expect that the completion of our studies will identify novel mechanisms regulate tumor-specific angiogenesis and novel targets to treat ovarian cancer patients.

Citation Format: Deepak Parashar, Anjali Geethadevi, Jasmine George, Gopakumar Gopinathan Nair, Changliang Chen, Sunila Pradeep, Pradeep Chaluvally-Raghavan. miR551b-mediated tumor-specific angiogenesis in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 206.

miRNA-Mediated RNA Activation in Mammalian Cells

MicroRNA (miRNA or miR) is a small noncoding RNA molecule ~22 nucleotides in size, which is found in plants, animals, and some viruses. miRNAs are thought to primarily down regulate gene expression by binding to 3' untranslated regions of target transcripts, thereby triggering mRNA cleavage or repression of translation. Recently, evidence has emerged that miRNAs can interact with the promoter and activate gene expression. This mechanism, called RNA activation (RNAa), is a process of transcriptional activation where the direct interaction of miRNA on the promoter triggers the recruitment of transcription factors and RNA-Polymerase-II on the promoter to activate gene transcription. To date, very little is known about the mechanism by which miRNA regulates RNA activation (RNAa) and their role in tumor progression. This is an emerging field in RNA biology. In this chapter, we describe the mechanisms utilized by miRNAs to activate transcription.

Abstract A195: A novel selective estrogen receptor degrader, EC-372, inhibits tumor growth and metastasis of breast cancer cells

Background: Breast cancer is one of the most common malignancies in women with high mortality rate worldwide. Clinical evidence suggests that antiestrogens have potential to inhibit the progression of hormone-dependent breast cancer. Here we showed that a novel selective estrogen receptor degrader (SERD), EC372, reduced estrogen receptor-α (ER-α), progesterone receptor (PR) and stabilized the expression of ER-β, which resulted in apoptosis in ER-positive breast cancer cells. Methods: We studied the effect of EC372 on DNA damage, cell cycle arrest, apoptosis, epithelial-to-mesenchymal transition (EMT), and mitochondrial membrane potential (MMP) in breast cancer cells. We also performed in vitro assays to evaluate the effect of EC372 on cell proliferation, colony formation, invasion, migration, cell adhesion in 2-dimensional (2-D) and sphere-forming abilities of tumor cells in 3-dimensional (3-D) cultures. Results: Our data show that EC372 inhibited the growth of T47D and MCF-7 human breast cancer cells. EC372 induced apoptosis in both cell lines as marked by cell shrinkage and apoptotic bodies. We found that treatment of EC372 downregulated the levels of ER-α and PR and stabilized the levels of ER-β, which subsequently resulted in cell cycle arrest, apoptosis, and suppressed the growth of breast cancer cells. We have also shown that EC372 reduced cell proliferation, colony formation, 3-D tumor spheroid size, migration, and invasive ability of breast cancer cells. Our cell cycle analysis data indicated that EC372 induced G1 arrest, as evidenced by a decrease in the protein levels of Cyclin D, phospho-Rb (S-807/811), and CDK-6 and increased Rb and p21 levels. We have further shown that EC372 induced apoptosis as evidenced by an increase in the levels of Annexin-V and by upregulation of proapoptotic molecules such as BAK, BAX, BID, cytochrome C, PARP1/cleaved PARP, and caspase 3, with a decrease in the levels of antiapoptotic molecules including BCl2, BCLxL, and survivin. In complement to our results, EC372 reduced the mitochondrial membrane potential (MMP) that triggered the activation of caspase 3 cascade, cleavage of PARP proteins, DNA damage, and subsequent cell death of breast cancer cells. Based on our in vitro results, EC372 is a unique and novel SERD, which inhibits tumor growth, migration, and invasion of breast cancer cells. Studies evaluating the potential of EC372 on in vivo tumor growth and metastasis are under way. Conclusions: This is the first comprehensive study on the mechanism by which EC372 inhibits tumor growth and promotes apoptosis of human breast cancer cells. Our collective data suggest that EC372 inhibits cell growth of ER-positive breast cancer cell lines through downregulating the levels of ER-α and PR, and stabilized the levels of ER-β. Based on our results, we suggest that EC372 is a potent SERD with anticancer effects that could be developed as a novel therapeutic agent to treat ER-positive breast cancer.

Citation Format: Deepak Parashar, Anjali Geethadevi, Jyotsna Mishra, Bindu Nair, Bindu Santhamma, Klaus Nickisch, Pradeep Chaluvally-Raghavan. A novel selective estrogen receptor degrader, EC-372, inhibits tumor growth and metastasis of breast cancer cells [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A195.

Direct Upregulation of STAT3 by MicroRNA-551b-3p Deregulates Growth and Metastasis of Ovarian Cancer

3q26.2 amplification in high-grade serous ovarian cancer leads to increased expression of mature microRNA miR551b-3p, which is associated with poor clinical outcome. Importantly, miR551b-3p contributes to resistance to apoptosis and increased survival and proliferation of cancer cells in vitro and in vivo. miR551b-3p upregulates STAT3 protein levels, and STAT3 is required for the effects of miR551b-3p on cell proliferation. Rather than decreasing levels of target mRNA as expected, we demonstrate that miR551b-3p binds a complementary sequence on the STAT3 promoter, recruiting RNA polymerase II and the TWIST1 transcription factor to activate STAT3 transcription, and thus directly upregulates STAT3 expression. Furthermore, anti-miR551b reduced STAT3 expression in ovarian cancer cells in vitro and in vivo and reduced ovarian cancer growth in vivo. Together, our data demonstrate a role for miR551b-3p in transcriptional activation. Thus, miR551b-3p represents a promising candidate biomarker and therapeutic target in ovarian cancer.

Copy number gain of hsa-miR-569 at 3q26.2 leads to loss of TP53INP1 and aggressiveness of epithelial cancers

Small noncoding miRNAs represent underexplored targets of genomic aberrations and emerging therapeutic targets. The 3q26.2 amplicon is among the most frequent genomic aberrations in multiple cancer lineages including ovarian and breast cancers. We demonstrate that hsa-miR-569 (hereafter designated as miR569), which is overexpressed in a subset of ovarian and breast cancers, at least in part due to the 3q26.2 amplicon, alters cell survival and proliferation. Downregulation of TP53INP1 expression by miR569 is required for the effects of miR569 on survival and proliferation. Targeting miR569 sensitizes ovarian and breast cancer cells overexpressing miR569 to cisplatin by increasing cell death both in vitro and in vivo. Thus targeting miR569 could potentially benefit patients with the 3q26.2 amplicon and subsequent miR569 elevation.

Hematogenous metastasis of ovarian cancer: rethinking mode of spread

Ovarian cancer has a clear predilection for metastasis to the omentum, but the underlying mechanisms involved in ovarian cancer spread are not well understood. Here, we used a parabiosis model that demonstrates preferential hematogenous metastasis of ovarian cancer to the omentum. Our studies revealed that the ErbB3-neuregulin 1 (NRG1) axis is a dominant pathway responsible for hematogenous omental metastasis. Elevated levels of ErbB3 in ovarian cancer cells and NRG1 in the omentum allowed for tumor cell localization and growth in the omentum. Depletion of ErbB3 in ovarian cancer impaired omental metastasis. Our results highlight hematogenous metastasis as an important mode of ovarian cancer metastasis. These findings have implications for designing alternative strategies aimed at preventing and treating ovarian cancer metastasis.

Abstract P5-10-03: OncomiR-569 deregulate p53 pathway and initiate breast oncogenesis

Background: The 3q26.2 chromosomal loci is highly amplified in large set of breast cancers, primarily in aggressive basal tumors are difficult to treat in the clinic. Our amplicon data suggests that 3q26.2 is a large structurally complex amplicon and multiple components in the amplicon contribute to tumor initiation and progression either alone or through cooperative activity. Detailed mapping of the 3q26.2 amplicon by us demonstrated a microRNA, miR569 is highly amplified as a part of 3q26.2 amplicon in breast cancer patient's samples. The role of microRNAs amplified at 3q26 loci is not well studied and their molecular functions and targets were not well known. Thus our studies provide novel mechanism underlying miR569 oncogenesis.

Methods: Following the Institutional Review Board approval, tissues obtained from MD Anderson Cancer Center tumor bank were used to exatract DNA and RNA. Human miR-569 was cloned into pEZX-MR06 lentiviral vector used for the production of amphotropic viruses to infect the target cells. The miRIDIAN microRNA mimics were used to overexpress miRs and the antimiRs were used to knock down the miRNAs. All the transfections were performed using Oligofectamine. Trypsinized cells were grown in 5% matrigel for the 3D morphogenesis of epithelial cells.

Results: Our results demonstrated a strong correlation between 3q26.2 amplification and expression of miR569 in patient samples of breast cancer. We subsequently demonstrated that overexpression and knockdown of miR569 in the breast epithelial cells altered their growth, proliferation, and lumen filling in 3-dimensional cultures grown in Matrigel. Importantly ectopic expression of miR569 in breast epithelial cells promoted tumor growth and increased metastatic potential in mouse xenograft models. Seed match based analysis of the microRNA targets, in silico studies and in vitro experiments showed that miR-569 directly target Tumor protein 53-induced nuclear protein1 (TP53INP1) and inhibited the expression of a tumor suppressor gene TP53INP1 expression. Loss of TP53INP1 expression mediated by miR569 altered normal cell growth cycle and subsequently promoted the survival and growth of tumor cells. Our in vitro results showed that knockdown of miR-569 and subsequent increase in TP53INP1 expression enhanced the sensitivity of cancer cell lines to cisplatin. Our immunohistochemical analysis showed that TP53INP1 protein levels were higher in normal tissues compared to cancer tissues. Further, reduced expression of TP53INP1 was observed in invasive cancers as compared to low malignant potential tumors, and decreased TP53INP1 protein levels were associated with worsened outcomes in breast cancer patients.

Disscussion: TP53INP1 had previously been identified as a combined target of p53 and p73; however our studies indicate that miR-569 regulates TP53INP1 levels independently of p53 and p73 expression. Based on our preclinical results of antimiR-569 on cell survival, tumor growth and cisplatin sensitivity, inhibiting miR-569 activity or increasing TP53INP1 expression may be valid therapeutic approaches to treat breast cancer.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-10-03.

HER2-Associated Breast Cancer Signature Using a 3D Culture Model

Background: Carcinomas of the breast account for one third of all cancers occurring in woman and responsible for approximately one quarter of cancer-related deaths in females. The HER2/Neu -oncogene is amplified in 20-25% percent of human primary breast cancers and this alteration is associated with disease behaviour. Whereas signalling pathways emanating from HER2 have been characterized, much less is known about the transcriptionally regulated genes that contribute to HER2 tumorigenic effects.Materials and Methods: Normal and HER2 overexpressing mammary epithelial cells (MCF10A) were grown in extracellular matrix to form 3D structures, which allow epithelial cells to organize into structures that resemble their in vivo architecture. RNA was isolated from the 3D structures and hybridized to an Affymetrix HuGene 1.0 ST oligonucleotide array.Results: Upon HER2 overexpression, mammary epithelial cells lost their polarity and formed disorganized structures in matrigel. Using microarrays we analyzed transcriptional events responsible for the morphological changes and found that several sets of genes such as integral proteins, transcription factors, matrix proteases and chemokines were highly altered in the HER2 overexpressing group. Using gene annotation we defined molecular-pathways which are highly altered in HER2 overexpressing cells. More generally, our study proposes a mechanistic description of the processes underlying the HER2 transcriptional network.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4146.