Clear Cell Carcinoma Cell Research Articles

Abstract A014: Role of stromal CD10 expression in progression of endometrial and endometriosis-associated cancers

Abstract Endometriosis-associated carcinomas (EACs) and endometrial malignancies have many commonalities yet their pathophysiology, particularly those with high-risk histology such as clear cell, is understudied. EACs are histologically and clinically distinct from other gynecological cancers due to their unique origin within endometriosis. The endometriotic microenvironment is uniquely hypoxic with high levels of iron due to recurrent menstrual cycling, and this iron-rich microenvironment has been linked to promoting carcinogenesis through iron-induced oxidative stress. However, the mechanism by which the endometriotic microenvironment contributes to EAC tumorigenesis and how this compares with endometrial cancer is unknown. Most of our current knowledge of EACs is built on either epidemiologic analyses or correlative studies. Additionally, most studies of the endometriotic microenvironment primarily focus on the epithelial component while the role of the stroma has been largely unexplored. Mesenchymal stem cells (MSC) are a critical component of the stromal microenvironment. Recently, we identified a key role of endometriosis derived MSCs (enMSCs) in altering ovarian clear cell carcinoma iron regulation. Interestingly, enMSCs resemble the primary endometrium derived MSCs, which suggested their role in endometrial cancer. This stromal subset is characterized by the loss of surface CD10 expression. It is known that cancer cells, particularly clear cell carcinoma (CCC), have a unique requirement for high levels of iron. We hypothesize that CD10 negative enMSCs promote growth of EAC and endometrial cancer through iron regulation. MSCs were isolated from primary human benign endometriosis, benign endometrium, or endometrial cancer. Flow cytometry was used to measure surface CD10 expression. We investigated the role of CD10 negative enMSCs on CCC iron regulation. Our results showed that CD10 negative enMSCs promote CCC growth by exporting iron through the upregulation of Hephaestin (HEPH) and Ferroportin (FPO) which then led to increase labile iron pool (LIP) in CCC cells. However, increasing the LIP does not occur with iron supplementation alone, this indicates the critical role of CD10 negative enMSCs in regulating iron handling in CCC cells. Additionally, our data showed that CD10 negative enMSCs alter the balance of Ferritin L and Ferritin H- the main iron storage proteins- in CCC cells. Mechanistically, our preliminary data showed that CD10 negative enMSCs directly donate Ferritin L into CCC cells. Further, CD10 negative enMSCs enhance Ferritin H degradation through the upregulation of ferritinophagy in CCC cells. In conclusion, our results indicate there is a sub-population of enMSCs, marked by the loss of CD10 expression, that enhances EAC and endometrial cancer cell growth through iron regulation. This highlights the existence of a tumor-promoting stromal cell within both the endometrium and endometriosis which can be capitalized on as an “Achilles' heel” to uncover novel treatment targets for EAC and endometrial cancer. Citation Format: Huda I. Atiya, Lan G. Coffman. Role of stromal CD10 expression in progression of endometrial and endometriosis-associated cancers [abstract]. In: Proceedings of the AACR Special Conference on Endometrial Cancer: Transforming Care through Science; 2023 Nov 16-18; Boston, Massachusetts. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(5_Suppl):Abstract nr A014.

Cancer cell-derived CD69 induced under lipid and oxygen starvation promotes ovarian cancer progression through fibronectin.

Cancer tissues generally have molecular oxygen and serum component deficiencies because of poor vascularization. Recently, we revealed that ICAM1 is strongly activated through lipophagy in ovarian clear cell carcinoma (CCC) cells in response to starvation of long-chain fatty acids and oxygen and confers resistance to apoptosis caused by these harsh conditions. CD69 is a glycoprotein that is synthesized in immune cells and is associated with their activation through cellular signaling pathways. However, the expression and function of CD69 in nonhematological cells is unclear. Here, we report that CD69 is induced in CCC cells as in ICAM1. Mass spectrometry analysis of phosphorylated peptides followed by pathway analysis revealed that CD69 augments CCC cell binding to fibronectin (FN) in association with the phosphorylation of multiple cellular signaling molecules including the focal adhesion pathway. Furthermore, CD69 synthesized in CCC cells could facilitate cell survival because the CD69-FN axis can induce epithelial-mesenchymal transition. Experiments with surgically removed tumor samples revealed that CD69 is predominantly expressed in CCC tumor cells compared with other histological subtypes of epithelial ovarian cancer. Overall, our data suggest that cancer cell-derived CD69 can contribute to CCC progression through FN.

Preclinical Activity of Plitidepsin Against Clear Cell Carcinoma of the Ovary

To evaluate the antitumor effects of Plitidepsin against clear cell carcinoma (CCC) of the ovary. The expression of eEF1A2 in ovarian cancer was assessed by immunohistochemistry. Using ovarian CCC cell lines, the antitumor effect of Plitidepsin was assessed both in vitro and in vivo. By over-expressing or knocking down the eEF1A2 expression, we investigated the role of eEF1A2 in the sensitivity of CCC cells to Plitidepsin. Immunoreactivity to eEF1A2 was observed in 76.2% of CCC, which was significantly higher than other histological subtypes of ovarian cancer. Plitidepsin exhibited significant antitumor activity toward chemonaive and chemoresistant CCC cells both in vitro and in vivo. Ectopic expression of eEF1A2 in CCC cells resulted in increased sensitivity to Plitidepsin. In contrast, eEF1A2 knockdown decreased sensitivity of CCC cells to plitidepsin. Plitidepsin, a novel anti-cancer agent that targets eEF1A2, may be a promising agent for treating ovarian CCC.

Abstract 2005: ZDHHC7 contributes to ferroptosis resistance through YAP localization in ovarian clear cell carcinoma

Abstract [Objective] Ovarian clear cell carcinoma (CCC) shows unique clinical features including an association with benign endometriosis which contains iron-rich fluid, and poor prognosis because of resistance to chemotherapy. Therefore, elucidating the basic mechanism as well as new treatment strategy of ovarian CCC is urgently needed. Recently, ferroptosis, which is characterized by the iron-dependent accumulation of lipid ROS, was reported to affect the malignant behaviors. Also, some reports showed ferroptosis regulation by Hippo signaling. ZDHHC7 is reported as the molecule regulating yes-associated protein (YAP), a key molecule of Hippo signature and is one of the ovarian CCC gene signature which we previously identified. We explored the impact of ferroptosis in ovarian CCC by investigating YAP localization.[Methods] We performed immunohistochemistry (IHC) of malondialdehyde (MDA; a marker of lipid reactive oxygen species, ROS) and 8-Oxo-2'-deoxyguanosine (8-OHdG, a marker of oxidative stress DNA damage) to analyze the status of lipid ROS with ovarian cancer patients. We also performed IHC of YAP and ZDHHC7 to evaluate them in clinical status. We calculated IC50 values of erastin (ferroptosis inducer) with seventeen ovarian cancer cell lines. Functional annotation clustering of microarray expression data was performed using Metascape. ZDHHC7 knockdown and YAP-5SA mutant, or YAP-activated form of ovarian CCC cell lines were generated and applied for in vitro assays.[Results] IHC analysis indicated higher MDA expression (p=0.0354) and 8-OHdG (p<0.0001) in CCC compared to high-grade serous carcinoma (HGSC), suggesting higher lipid ROS as well as oxidative stress status in ovarian CCC. IC50 values of erastin were significantly higher in CCC than in other types of ovarian cancer (p<0.01). Categorical analysis revealed that genes related to Hippo signaling were enriched in erastin-resistant cell lines. IHC analyses indicated low nuclear expression of YAP and high expression of ZDHHC7 in CCC samples (p=0.0010). The cases with low expression of nuclear YAP showed significantly poorer prognosis compared to high expression cases (p=0.0075) in ovarian CCC. YAP-5SA mutant (YAP-active-mutant) CCC cells showed higher sensitivity to erastin and ML210 (ferroptosis inducer) than control in ovarian CCC cell lines. ZDHHC7 knockdown of CCC cells induced nuclear localization of YAP and showed decreased IC50 values of erastin and ML210 compared to control cells.[Conclusion] Although lipid ROS is accumulated in ovarian CCC, ovarian CCC showed ferroptosis resistance through YAP localization regulated by ZDHHC7. Citation Format: Yoko Furutake, Ken Yamaguchi, Masayo Ukita, Mana Taki, Koji Yamanoi, Junzo Hamanishi, Takashi Kobayashi, Masaki Mandai. ZDHHC7 contributes to ferroptosis resistance through YAP localization in ovarian clear cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2005.

Toward an understanding of tissue factor pathway inhibitor-2 as a novel serodiagnostic marker for clear cell carcinoma of the ovary.

Tissue factor pathway inhibitor (TFPI)-2 has recently emerged as a serodiagnostic marker for patients with epithelial ovarian cancer (EOC), especially clear cell carcinoma (CCC). This review discusses the biological properties of TFPI-2 and why serum levels are elevated in CCC patients. A comprehensive literature search was conducted in PubMed up until March, 2021. TFPI-2 is a Kunitz-type protease inhibitor and negatively regulates the enzymatic activities, such as plasmin. TFPI-2 has been characterized as a tumor suppressor gene and was frequently downregulated through promoter hypermethylation in various human cancers. In contrast, TFPI-2 was overexpressed only in CCC. TFPI-2 may be involved in the pathophysiology of CCC, possibly through regulation of coagulation system, stabilization of extracellular matrix (ECM), and induction of intracellular signal transduction. TFPI-2 suppresses tissue factor-induced hypercoagulation in a hypoxic environment. TFPI-2, secreted by CCC cells, platelets, and adjacent vascular endothelial cells, may suppress tumor growth and invasion through ECM remodeling. Nuclear TFPI-2 may suppress matrix metalloproteinase production via transcription factors and modulate caspase-mediated cell apoptosis. CCC cells may upregulate the TFPI-2 expression to adapt to survival in the demanding environment. TFPI-2 is secreted by CCC cells and enters the systemic circulation, resulting in elevated blood levels. Serum TFPI-2 reflects the overexpression of TFPI-2 in CCC tissues and is a potential serodiagnostic marker. Further research is needed to explore the expression, clinical significance, biological function, and potential mechanism of TFPI-2 in CCC.

Diagnostic efficacy of ascites cell block for ovarian clear cell carcinoma.

Ascites cytology is important for determining the stage and treatment methods for ovarian clear cell carcinoma (CCC) as defined by the 2014 International Federation of Obstetrics and Gynecology classification. Patients with CCC who underwent surgery at our hospital between January 2012 and December 2019 and who received cytodiagnosis of their ascites using Papanicolaou (Pap) and May-Grünwald-Giemsa (MGG) staining, and cell block methods were identified. The cell block technique was performed using hematoxylin-eosin (H&E) staining and immunohistochemical staining for hepatocyte nuclear factor-1β (HNF-1β), estrogen receptor (ER), progesterone receptor (PR), and Wilms tumor-1 (WT-1). Cancer cells of CCC were defined as tumor cells that were positive for HNF-1β and negative for ER, PR, and WT-1. The diagnostic accuracy of ascites cytology using Pap and MGG staining and cell block methods was examined. Based on cytological data, our study included 17 patients: seven (41.1%) with malignant (MAL) ascites, eight (47.1%) with negative for malignancy (NFM), and two (11.8%) with atypia of undetermined significance (AUS) because of a few atypical cells based on Pap and MGG staining. Malignant cells diagnosed by cell blocks were detected in 7/7 patients with MAL ascites based on PAP and MGG staining, 2/8 (25.0%) patients with NFM, and 1/2 (50%) patients with AUS. These findings show that the cell block method combined with the immunohistochemical investigation may be useful for increasing the diagnostic accuracy of malignant cells in CCC.

Tissue factor expression and tumor-infiltrating T lymphocytes in ovarian carcinomas and their association with venous thromboembolism.

Ovarian cancer is a known risk factor of venous thromboembolism (VTE). Thrombogenic factor expression and lymphocytic infiltrate have been reported in endometriosis and ovarian cancers. We reviewed 30 cases of ovarian carcinomas (high grade serous carcinoma, 10; endometrioid carcinoma, 10; clear cell carcinoma (CCC), 10) and 16 endometriotic lesions. We immunohistochemically investigated the expressions of tissue factor (TF), podoplanin, P-selectin, and number of CD4 and CD8 positive lymphocytes in cancer tissue and endometriotic lesions, along with their relationship with VTE. The expression of TF was higher in CCC. The TF expression and the number of CD8 positive cells were higher in cancer tissues with VTE than in those without VTE. The podoplanin or P-selectin expression did not differ among histological types or between cases with and without VTE. Our results demonstrated a high TF expression and intraepithelial CD8 cells in CCC, which were associated with VTE. The results suggest that infiltrating lymphocytes may affect TF expression that, in turn, influences VTE.

Hypoxia-inducible Factor-1α Suppression in Ovarian Clear-cell Carcinoma Cells by Silibinin Administration.

Advanced ovarian clear-cell carcinoma (CCC) fails to respond to standard chemotherapy, and has a poor prognosis. Since hypoxia-inducible factor-1 (HIF-1) stimulates various genes involved in cancer, we aimed to examine the efficacy of silibinin, an active component of milk thistle belonging to Asteraceae, in suppressing HIF-1 activity, and elucidate the underlying mechanism in human CCC cell lines. Human ovarian CCC cell lines HAC-2, OVISE, and RMG-1 were treated with 500 μM silibinin for 4 h under normoxic and hypoxic conditions. Using DNA microarray, we analysed genes whose expression modulated more than 2-fold in response to hypoxia, whereas HIF-1α expression was measured using ELISA. Silibinin treatment decreased HIF-1α protein in all cell lines, and eIF4E2 and RPS6 mRNA in HAC-2 and RMG-1 cells. Silibinin suppressed HIF-1α protein under hypoxic conditions in CCC cell lines and could be a potential anti-cancer drug.

High Expression of p21 as a Potential Therapeutic Target in Ovarian Clear-cell Carcinoma.

DNA damage response (DDR), wherein p21 is a cell fate determinant, is a potential cancer therapeutic target. Molecular expression during DDR was explored in ovarian clear-cell carcinoma (CCC). CHK1, CHK2, TP53 and p21 expression in DDR was examined using immunostaining in surgical sections of CCC (n=22). Molecular alterations in two types of CCC cell lines, JHOC-5 and JHOC-9, were investigated using western blot analysis. Expression of DDR-associated molecules was noted in most patients. While high p21 expression was found in half of the patients, the remaining patients exhibited low p21 expression. Treatment with UC2288, a p21 inhibitor, attenuated proliferation of both cell lines, more prominently in JHOC-9, resulting in reduced viability and subsequent apoptosis. p21 Inhibitor induced cell death in cells with high p21 expression, suggesting that p21 suppression can be a therapeutic strategy to treat patients with CCC.

Abstract A73: BCL-XL dependency in a subset of ovarian clear-cell carcinoma cell lines

Abstract Clear-cell ovarian carcinoma is a rare histologic subtype of epithelial ovarian cancers. Clear-cell ovarian cancers tend to be less responsive to platinum-based chemotherapy compared to high-grade serous ovarian cancers. In a dataset of large-scale CRISPR knockout and RNAi screens of cancer cell lines (depmap.org), a subset of ovarian clear-cell carcinoma cell lines were sensitive to knockout or knockdown of BCL2L1, encoding antiapoptotic protein BCL-XL. Most clear-cell ovarian cancer cell lines also express BCL2L1 mRNA and protein. We therefore tested a panel of ovarian cancer cell lines for response to BH3 mimetic drugs, which inhibit different members of the BCL-2 family of antiapoptotic proteins. Initial data showed that a subset of ovarian clear-cell carcinoma cell lines was sensitive to single-agent BCL-XL inhibition with A1331852 and dual BCL-2/BCL-XL inhibition with ABT-263. In contrast, these cell lines were relatively insensitive to single-agent BCL-2 inhibition or MCL1 inhibition. We are currently applying BH3 profiling, a functional assay for apoptotic priming, to test the response of ovarian clear-cell carcinoma cell lines to BCL-XL inhibition using a BCL-XL specific peptide, HRK. Collectively, these studies suggest that ovarian clear-cell carcinomas may be sensitive to BCL-XL inhibition, either alone or in combination with chemotherapy. Citation Format: Elizabeth H. Stover, Maya K. Gelbard, Ursula A. Matulonis, Matthew Meyerson. BCL-XL dependency in a subset of ovarian clear-cell carcinoma cell lines [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr A73.

Pathology of clear cell carcinoma of the ovary: A basic view based on cultured cells and modern view from comprehensive approaches.

Clear cell carcinoma (CCC) is a distinct histologic type of ovarian carcinoma. CCC is more frequent in Japan than in the Western world. CCC is chemo-resistant and often associated with paraneoplastic thromboembolism. Histologically, CCC is characterized by both cancer cells and stromas, being concordant with the cytological features. Clear cells contain abundant glycogen. Hepatocyte nuclear factor-1β is a specific marker of CCC, and is likely to be involved in glucose metabolism. Extracellular matrix (ECM)-deposited stroma and plasma cell-rich inflammatory stroma are characteristic stromas of CCC. Studies using CCC cell lines showed that CCC cells produce ECMs and stimulate plasma cell differentiation in a paracrine manner. Most CCCs, as well as endometrioid carcinomas, originate from ovarian endometriosis. This is supported by molecular genetic data, although it remains unclear why different histologic types originate from the same precursor. CCC and endometrioid carcinoma are Lynch syndrome-associated ovarian carcinomas. Recent comprehensive studies indicate that CCC is distinct not only in terms of histology but also in genomics, epigenomics and transcriptomics. This review summarizes the pathology of ovarian CCC along with a basic view based on cultured cells, and refers to recent genetic and omic data.

CDNA expression library screening revealed novel functional genes involved in clear cell carcinogenesis of the ovary in vitro

In order to identify genes involved in the pathogenesis of clear cell carcinoma of the ovary (CCC), functional screening using a cDNA expression library was performed. We extracted mRNA from a CCC cell line (RMG-1), established a cDNA library using a retroviral vector, transfected that library into mouse NIH3T3 cells and sequenced the resultant foci. The tissue-type specific expression of isolated genes and their transforming activities were evaluated. Seven genes were isolated. Of these genes, the mRNA expression of SEC61B and DVL1 is significantly stronger in CCC than in other histological types (p < .05). Immunohistochemical staining reveals the stronger expression of SEC61B and C1ORF38 than normal ovarian tissues (p < .05). Focus formation is confirmed by the transfection of SEC61B, C1ORF38, and DVL1 into NIH3T3 cells. The present study identified novel genes including SEC61B, C1ORF38, and DVL1, involved in the pathogenesis of CCC. These genes may be additional therapeutic targets for CCC. Impact statement What is already known on this subject? Several important genetic abnormalities, including ARID1A and PIK3CA mutations, have been reported in ovarian clear cell carcinoma (CCC). What the results of this study add? SEC61B, C1ORF38, and DVL1 were newly detected as candidate genes involved in ovarian clear cell carcinogenesis. What the implications are of these findings for clinical practice and/or further research? Functional screening using a cDNA expression library may be a useful technique to identify functional genes for pathogenesis. The information obtained using this technique may provide new therapeutic targets of CCC.

Abstract GMM-036: COMPREHENSIVE GENOMIC, PROTEOMIC, AND EXPERIMENTAL CHARACTERIZATION OF OVARIAN CLEAR CELL CARCINOMA CELL LINES FOR IMPROVED DRUG DEVELOPMENT

Abstract PURPOSE: Ovarian cancer is a heterogeneous disease with multiple histological subtypes and a wide range of genetic aberrations. While high-grade serous carcinoma (HGSC) is the most common type, clear cell carcinoma (CCC) of the ovary is notoriously the most challenging to treat and exhibits very low response rates to standard therapies. However, efforts to understand CCC and develop new therapeutic approaches to this subtype have been limited because it represents a minority of ovarian cancer cases in the United States and Europe. In contrast, CCC accounts for more than 30% of all ovarian cancer in Japan. To improve the survival of patients with ovarian CCC, a deeper understanding of the molecular features of available model systems is needed. Our goal is to characterize a panel of CCC cell lines genomically and functionally and identify those that can serve as tractable model systems for future in vivo drug discovery studies. METHOD: First, we characterize 9 CCC cell lines (ES-2, TOV21G, OVTOKO, OVMANA, OCI-C5x, JHOC-5, JHOC-7, JHOC-9, and OVISE) with whole exome sequence and proteomics approaches (reverse phase protein array; RPPA). Secondly, we performed in vitro assays, including soft-agar colony formation assays and MTT assays using standard chemotherapies. Thirdly, to test in vivo tumorigenic potential, by injecting 5 million cells of luciferized CCC lines in NSG female mice using both the subcutaneous route and the intraperitoneal route. Imaging was performed weekly using the In Vivo Imaging System. RESULTS: Among the 9 CCC lines, seven (TOV21G, OVTOKO, OVMANA, OCI-C5x, JHOC-5, JHOC-9, and OVISE) harbor ARID1A mutation, which is the most prevalent mutation in CCC (50%). The second common mutation in CCC (40%), PIK3CA mutation, and was detected in 4 cells (TOV21G, OVMANA, OCI-C5x, and OVISE). The ES-2 line has TP53 and BRAF mutation and its genomic profile is inconsistent with CCC. A BRCA2 mutation was found in OVTOKO and JHOC-5, finding not previously reported. Principal component analysis of RPPA data showed distinct clusters between the 9 CCC lines and the 6 HGSC lines. Interestingly, we also observed two distinct clusters within the CCC lines. Consistent with our genomic analysis, ES-2 correlated with HGSC lines based on RPPA data. In our in vitro drug studies, OVTOKO, OCI-C5x, and OVISE exhibited a Carboplatin/Paclitaxel resistance phenotype. In xenograft study, 4 cell lines (ES-2, TOV21G, OVTOKO, and OCI-C5x) formed tumor within a month, suggesting they are useful tools for in vivo studies. In contrast, OVMANA, JHOC-7, JHOC-9, and OVISE take more than 100 days to form the tumors. Soft-agar colony formation results correlated with how long it took to develop xenograft tumor in each line. CONCLUSION: Our genomic studies identified aberrations in CCC lines not previously described. The proteomics data revealed two clusters within the CCC lines that might represent functionally distinct groups. Finally, we identified four cell lines (ES-2, TOV21G, OVTOKO, and OCI-C5x) that readily form tumors in mice and could be used for future in vivo drug studies. However, ES-2 appears to cluster more closely with HGSC and may not represent the CCC histotype. Citation Format: Yasuto Kinose, Dorothy Hallberg, Gordon Mills, Tan Ince, Victor Velculescu, Fiona Simpkins, Ronny Drapkin. COMPREHENSIVE GENOMIC, PROTEOMIC, AND EXPERIMENTAL CHARACTERIZATION OF OVARIAN CLEAR CELL CARCINOMA CELL LINES FOR IMPROVED DRUG DEVELOPMENT [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr GMM-036.

Integrating modern approaches to pathogenetic concepts of malignant transformation of endometriosis.

In the present study, we summarize the role of the shared and independent (epi)genetic background between endometrioid carcinoma (EC) and clear cell carcinoma (CCC), two histological subtypes of endometriosis-associated ovarian cancer (EAOC). Using the PubMed database, we conducted a literature review of various studies related to the malignant transformation of endometriosis. Both endometriosis and EAOC face potential environmental hazards, including hemoglobin (Hb), heme and free iron, which induces DNA damage and mutations. Although EC is distinguished from CCC due to different morphologies, both represent common environmental profiles and maintain the similar (epi)genomic abnormalities with multiple overlaps and share similar molecular signatures. By contrast, EAOC also has disease-specific gene signatures corresponding with each histological subtype: Estrogen receptor promotes EC cell proliferation ('go') and hepatocyte nuclear factor-1β (HNF-1β) induces CCC cell cycle arrest ('stop') under oxidative stress conditions. This model underscores a subtype-dependent 'go or stop' dichotomy, possibly through better ability to adapt in a changing environment. It was found that cyst fluid Hb and iron concentrations were significantly lower in EAOC when compared to benign ovarian endometrioma (OE), supporting the hypothesis that the redox imbalance plays a key role in the pathogenesis of EAOC. There are at least two phases of iron carcinogenesis and tumor progression: The initial wave of iron-induced oxidative stress and DNA mutations would be followed by the second big wave of subsequent synthesis of the antioxidants, which diminishes cellular oxidative stress capacity, increases apoptosis resistance and promotes tumor initiation and progression. Special emphasis is given to novel pathophysiological concepts of malignant transformation of endometriosis.

KIF20A expression as a prognostic indicator and its possible involvement in the proliferation of ovarian clear‑cell carcinoma cells.

Kinesin family member 20A (KIF20A), which is involved in cytokinesis and intracellular transportation, has been recently reported to be upregulated in several malignancies and may contribute to chemotherapeutic resistance. We examined the distribution and expression of KIF20A in clear-cell carcinoma (CCC) of the ovary to elucidate its clinical significance and molecular mechanism. Paraffin sections from ovarian CCC tissues (N=43) were immunostained with KIF20A antibody, and the staining intensities were semi-quantitatively evaluated. Furthermore, we investigated whether silencing of KIF20A contributes to the proliferation-inhibitory potential using CCC cells. During the observational period, 18 patients (41.9%) developed recurrence. The median time to recurrence was 11.5 months. Patients in the high KIF20A expression group showed poorer progression-free survival (PFS) and overall survival (OS) than those in the low expression group (P=0.0443 and P=0.0478, respectively). In multivariable analyses, KIF20A expression was also a significantly independent indicator of PFS and a marginally significant indicator of OS [PFS: HR (high vs. low), 5.488; 95% CI, 1.410–24.772 (P=0.0136); OS: HR, 2.835; 95% CI, 0.854–11.035, (P=0.0897)]. In in vitro studies, the ovarian CCC cell proliferation was significantly decreased by KIF20A silencing or in the presence of KIF20A inhibitor in CCC cells. Cell cycle G2/M arrest and a higher apoptosis-induced fraction were more frequently observed in si-KIF20A-transfected CCC cells than in the control cells. Although the present study was preliminary, these data indicate the possible involvement of KIF20A in the proliferation of CCC, suggesting that targeting this molecule may contribute to reversing the malignant potential consequently affecting the oncologic outcome of CCC patients.

The HNF-1β-USP28-Claspin pathway upregulates DNA damage-induced Chk1 activation in ovarian clear cell carcinoma.

Transcription factor hepatocyte nuclear factor 1-beta (HNF-1β) enhances checkpoint kinase 1 (Chk1) activation and promotes G2/M cell cycle progression in ovarian clear cell carcinoma (CCC) following exposure to diverse genotoxic agents including bleomycin. However, the underlying mechanism leading to checkpoint activation of HNF-1β still remains largely unknown. To clarify the effects of HNF-1β on cell cycle checkpoints, human CCC cell lines were transfected with siRNAs targeting HNF-1β, Claspin, USP28, or a control vector. Ubiquitination and stabilization of Claspin protein by HNF-1β was assessed by immunoprecipitation. Loss-of-function studies using RNAi-mediated gene silencing indicated that HNF-1β facilitated the Claspin expression after treatment with a genotoxic agent bleomycin, resulting in accumulation of phosphorylated Chk1 (p-Chk1) and promotion of survival in CCC cell lines. This study showed for the first time that USP28, a de-ubiquitinase crucial for Claspin expression, is one target gene of HNF-1β. Knockdown of endogenous USP28 suppressed the Claspin expression and p-Chk1 activation and cell viability. Our findings identify a novel pathway of the HNF-1β―USP28―Claspin―Chk1 axis in checkpoint signal amplification in response to DNA damage. Targeting this pathway may represent a putative, novel, anticancer strategy in ovarian CCC.

Novel potential photodynamic therapy strategy using 5-Aminolevulinic acid for ovarian clear-cell carcinoma.

Photodynamic therapy (PDT) is known as a minimally invasive treatment for cancer. 5-Aminolevulinic acid (ALA) is a precursor of the photosensitizing agent protoporphyrin IX (PpIX). Patients with ovarian clear-cell carcinoma (CCC) have poorer prognoses than those of patients with other histological CCC types. We evaluated the efficacy of ALA-PDT on CCC cells in vitro. We used seven human CCC cell lines to measure the cytotoxicity of ALA-PDT. PpIX production in cancer cells was measured using a micro-plate reader. Quantitative real-time PCR was performed to assess the mRNA levels of genes involved in the accumulation of PpIX in cancer cells. Additionally, we measured the enhancement in cytotoxicity with the use of an ABCG2 inhibitor. We found that three cell lines were highly sensitive to ALA-PDT. In contrast, one cell line was resistant to ALA-PDT. The cytotoxicity of ALA-PDT varied among CCC cell lines. The IC50 values of ALA-PDT for the CCC cell lines had a wide range (30-882μM). The cytotoxicity of ALA-PDT was correlated with the intracellular PpIX accumulation. The cell lines sensitive to ALA-PDT expressed PEPT1 (an ALA uptake transporter). The cell line resistant to ALA-PDT expressed ABCG2 (a PpIX export transporter). In the resistant cell line, a combination treatment with both ALA and an ABCG2 inhibitor resulted in the promotion of cytotoxic sensitivity. The present study revealed the efficacy of ALA-PDT against CCC with chemoresistance in vitro.

The Anti-tumor Effect of Cabozantinib on Ovarian Clear Cell Carcinoma In Vitro and In Vivo.

Several reports have shown that the overexpression of the MET proto-oncogene, receptor tyrosine kinase (MET), was more frequently observed in clear cell carcinoma (CCC) than in non-CCC. We evaluated the antitumor activity of cabozantinib, that targets MET. A gene expression analysis of tumors from human ovarian cancers was carried out by transcriptome sequencing. An in vitro 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide assay (MTT assay) and in vivo experiments were performed to determine the activity of cabozantinib. The MET levels were higher in tumors with CCC than high-grade serous carcinoma (2.2-fold). Cabozantinib inhibited cell viability and phosphorylation of AKT and MAPK under the treatment of hepatocyte growth factor in RMG-I CCC cells. The tumors removed from mice given cabozantinib of 10 mg/kg weighed 70% less than control on day 15, and the immunohistochemical reactivity of phosphorylated MET was reduced compared with control mice. Cabozantinib contributes to tumor reduction, and phosphorylated MET represents an attractive target of CCC.

Low uptake of fluorodeoxyglucose in positron emission tomography/computed tomography in ovarian clear cell carcinoma may reflect glutaminolysis of its cancer stem cell-like properties.

The characteristics of ovarian cancers that showed low activation of glycolysis were investigated. Using medical records of patients with ovarian cancers who had undergone fluorodeoxyglucose positron emission tomography/computed tomography(FDG-PET/CT) prior to their primary surgery at the University of Tokyo Hospital between 2010 and2015, we identified cases with a low uptake of FDG in PET/CT. We considered the maximum standardized uptake value(SUVmax) as the degree of glucose uptake. We investigated the properties which may account for the low activation of glycolysis invitro. The expression level of alanine, serine, cysteine-preferring transporter2(ASCT2, a glutamine influx transporter), system L-type amino acid transporter1(LAT1, a glutamine efflux transporter) and glucose transporter1(GLUT1, a glucose influx transporter) were investigated by western blotting. The phosphorylation level of AMP-activated protein kinase(AMPK), which is one of the metabolic sensors, was also investigated. Most of the cases with a low uptake SUVmax were limited to patients with ovarian clear cell carcinoma(CCC). We obtained cancer stem cell(CSC)-like properties from CCC cell lines, and compared the expression levels of transporters between non-CSCs and CSCs. Whereas the expression level of ASCT2 was nearly unchanged between non-CSCs and CSCs, the expression levels of LAT1 and GLUT1 were decreased in CSCs compared to non-CSCs. The phosphorylation level of AMPK was reduced in CSCs compared to non-CSCs. Inconclusion, we suggested that ovarian CCC showed low activation of glycolysis, and this may reflect glutaminolysis of its CSC-like properties.

Inhibition of autophagy protein LC3A as a therapeutic target in ovarian clear cell carcinomas.

ObjectiveOvarian clear cell carcinoma (CCC) is one of histological subtypes showing poor prognosis due to chemoresistance. The association of autophagy-related proteins and clinical implementation in CCC has not been determined.MethodsThe present study investigated whether expression of autophagy-related protein, light chain 3A (LC3A), was related with prognoses in the patients with CCC using immuno-histochemical stainings, and whether inhibition of autophagy modified the sensitivity to cisplatin in CCC cells in vitro.ResultsHigh expression of autophagy-related protein, LC3A, was detected in 78 cases (78%) in all CCC cases. The patients with high LC3A expression showed significantly lower response rate to primary chemotherapy (17% vs. 100%, p<0.010), and had worse progression-free survival (PFS) and overall survival (OS) compared with those with LC3A low expression. Furthermore, multivariate analyses revealed that high expression of LC3A was identified as independent worse prognostic factors for PFS and OS. Inhibition of autophagy protein LC3A using hydroxychloroquine (HCQ) increased sensitivity to cisplatin in CCC cells in vitro.ConclusionHigh expression of LC3A proteins was associated with lower response to platinum therapy, leading to worse prognoses in CCC. Although further studies are needed to confirm the results, inhibition of autophagy by HCQ was associated with platinum sensitivity. Autophagy protein LC3A could be a promising target for treatment for CCC.