Small Cell Carcinoma Of The Ovary, Hypercalcemic Type Research Articles

Small Cell Carcinoma of the Ovary, Hypercalcemic Type (SCCOHT) - Current State of knowledge

Small Cell Carcinoma of the Ovary, Hypercalcemic Type (SCCOHT) - Current State of knowledge

Clinical characteristics and status of treatment of small-cell carcinoma of the ovary, hypercalcemic type in the Chinese population: a meta-analysis.

This study aimed to comprehensively analyze the clinical characteristics and treatment status of Chinese small cell carcinoma of the ovary hypercalcemic type (SCCOHT) patients, providing insights into this unique population and comparing findings with international literature. Through a meta-analysis, we collected data from published case reports and records from the Obstetrics & Gynecology Hospital of Fudan University. Demographic information, clinical presentations, tumor attributes, treatment modalities, and survival outcomes were extracted and examined alongside relevant global studies. The analysis encompassed 80 Chinese SCCOHT patients, of which 62 from 33 previously reported literatures, and the other 18 were from Obstetrics & Gynecology Hospital of Fudan University. In 62 cases with stage information, A total of 25 tumors were International Federation of Gynecology and Obstetrics stage I, 3 were stage II, 19 were stage III, and 15 were stage IV. Most patients received surgery and chemotherapy, but regimens were varied. Median follow-up was 10 months (range=4-120). Elevated carbohydrate antigen 125 and serum calcium levels were consistent findings. Recurrence rates were notable, especially among stage I patients. Platinum-based chemotherapy, paclitaxel and carboplatin (n=11, 13.4%), constituted common treatment regimens. This study observed demographic and clinical similarities with international datasets. And the findings emphasize the urgency for innovative therapeutic approaches to improve outcomes in SCCOHT patients. Continued research efforts are essential to enhance the knowledge surrounding this rare malignancy and to optimize its clinical management.

Dedifferentiated and Undifferentiated Ovarian Carcinoma: An Aggressive and Molecularly Distinct Ovarian Tumor Characterized by Frequent SWI/SNF Complex Inactivation

Dedifferentiated and undifferentiated ovarian carcinomas (DDOC/UDOC) are rare neoplasms defined by the presence of an undifferentiated carcinoma. In this study, we detailed the clinical, pathological, immunohistochemical, and molecular features of a series of DDOC/UDOC. We collected a multi-institutional cohort of 23 DDOC/UDOC and performed immunohistochemistry for core switch/sucrose nonfermentable (SWI/SNF) complex proteins (ARID1A, ARID1B, SMARCA4, and SMARCB1), mismatch repair (MMR) proteins, and p53. Array-based genome-wide DNA methylation and copy number variation analyses were performed on a subset of cases with comparison made to a previously reported cohort of undifferentiated endometrial carcinoma (UDEC), small cell carcinoma of the ovary, hypercalcemic type (SCCOHT), and tubo-ovarian high-grade serous carcinoma (HGSC). The age of all 23 patients with DDOC/UDOC ranged between 22 and 71 years (with an average age of 50 years), and a majority of them presented with extraovarian disease (16/23). Clinical follow-up was available for 19 patients. Except for 2 patients, the remaining 17 patients died from disease, with rapid disease progression resulting in mortality within a year in stage II–IV settings (median disease-specific survival of 3 months). Eighteen of 22 cases with interpretable immunohistochemistry results showed loss of expression of core SWI/SNF protein(s) that are expected to result in SWI/SNF complex inactivation as 10 exhibited coloss of ARID1A and ARID1B, 7 loss of SMARCA4, and 1 loss of SMARCB1. Six of 23 cases were MMR-deficient. Two of 20 cases exhibited mutation-type p53 immunoreactivity. Methylation profiles showed coclustering of DDOC/UDOC with UDEC, which collectively were distinct from SCCOHT and HGSC. However, DDOC/UDOC showed an intermediate degree of copy number variation, which was slightly greater, compared with SCCOHT but much less compared with HGSC. Overall, DDOC/UDOC, like its endometrial counterpart, is highly aggressive and is characterized by frequent inactivation of core SWI/SNF complex proteins and MMR deficiency. Its molecular profile overlaps with UDEC while being distinct from SCCOHT and HGSC.

Establishment and characterization of a novel cell line (SCCOHT-CH-1) and PDX models derived from Chinese patients of small cell ovarian carcinoma of the hypercalcemic type

Small cell carcinoma of the ovary hypercalcemic type (SCCOHT) is a rare and aggressive malignancy that poses a significant clinical challenge due to its grim prognosis. Unfortunately, only three SCCOHT cell lines are currently available for scientific research. In this study, we have successfully established a novel SCCOHT cell line from a recurrent lesion of a SCCOHT patient, named SCCOHT-CH-1. We comprehensively characterized the novel cell line by employing techniques such as morphological observation, CCK-8 assay, Transwell assay, clone formation assay, short tandem repeat sequence (STR) analysis, karyotype analysis, immunohistochemical staining, western blot assay, and xenograft tumor formation assay. SCCOHT-CH-1 cells were small circular and had a unique STR profile. The population-doubling time of SCCOHT-CH-1 was 33.02 h. The cell line showed potential migratory and invasive ability. Compared with another SCCOHT cell line COV434, SCCOHT-CH-1 exhibited higher expression of AKT, VIM, and CCND1. At the same time, SCCOHT-CH-1 has the ability of tumorigenesis in vivo. We also successfully constructed three patient-derived xenograft (PDX) models of SCCOHT, which were pathologically diagnosed to be consistent with the primary tumor, accompanied by loss of SAMRCA4 protein expression. The establishment of SCCOHT-CH-1 cell line and PDX models from Chinese people represent a pivotal step toward unraveling the molecular mechanism of SCCOHT and fostering the development of targeted interventions to tackle this challenging malignancy.

Small Cell Carcinoma of the Ovary, Hypercalcemic Type (SCCOHT): Patient Characteristics, Treatment, and Outcome-A Systematic Review.

Small-cell carcinoma of the ovary, hypercalcemic type (SCCOHT) is a rare aggressive ovarian malignancy mainly affecting children, adolescents, and young adults. Since the discovery of mutations in the SMARCA4 gene in 2014, SCCOHT has become the subject of extensive investigation. However, international uniform treatment guidelines for SCCOHT are lacking and the outcome remains poor. The aim of this systematic review is to generate an overview of all reported patients with SCCOHT from 1990 onwards, describing the clinical presentation, genetic characteristics, treatment, and outcome. A systematic search was performed in the databases Embase, Medline, Web of Science, and Cochrane for studies that focus on SCCOHT. Patient characteristics and treatment data were extracted from the included studies. Survival was estimated using Kaplan-Meier's methodology. To assess the difference between survival, the log-rank test was used. To quantify the effect of the FIGO stage, the Cox proportional hazard regression model was estimated. The chi-squared test was used to study the association between the FIGO stage and the surgical procedures. Sixty-seven studies describing a total of 306 patients were included. The median patient age was 25 years (range 1-60 years). The patients mostly presented with non-specific symptoms such as abdominal pain and sometimes showed hypercalcemia and elevated CA-125. A great diversity in the diagnostic work-up and therapeutic approaches was reported. The chemotherapy regimens were very diverse, all containing a platinum-based (cisplatin or carboplatin) backbone. Survival was strongly associated with the FIGO stage at diagnosis. SCCOHT is a rare and aggressive ovarian cancer, with a poor prognosis, and information on adequate treatment for this cancer is lacking. The testing of mutations in SMARCA4 is crucial for an accurate diagnosis and may lead to new treatment options. Harmonization and international collaboration to obtain high-quality data on diagnostic investigations, treatment, and outcome are warranted to be able to develop international treatment guidelines to improve the survival chances of young women with SCCOHT.

A Population-Based Study of Patients With Small Cell Carcinoma of the Ovary, Hypercalcemic Type, Encompassing a 30-Year Period.

Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) is a rare and lethal tumor, characterized by hypercalcemia and early onset and associated with germline and somatic SMARCA4 variants. To identify all known cases of SCCOHT in the Slovenian population from 1991 to 2021 and present genetic testing results, histopathologic findings, and clinical data for these patients. We also estimate the incidence of SCCOHT. We conducted a retrospective analysis of hospital medical records and data from the Slovenian Cancer Registry in order to identify cases of SCCOHT and obtain relevant clinical data. Histopathologic review of tumor samples with assessment of immunohistochemical staining for SMARCA4/BRG1 was undertaken to confirm the diagnosis of SCCOHT. Germline and somatic genetic analyses were performed using targeted next-generation sequencing. Between 1991 and 2021, we identified 7 cases of SCCOHT in a population of 2 million. Genetic causes were determined in all cases. Two novel germline loss-of-function variants in SMARCA4 LRG_878t1:c.1423_1429delTACCTCA p.(Tyr475Ilefs*24) and LRG_878t1:c.3216-1G>T were identified. At diagnosis, patients were ages 21 to 41 and had International Federation of Gynecology and Obstetrics, or FIGO, stage IA-III disease. Outcomes were poor, with 6 of 7 patients dying of disease-related complications within 27 months from diagnosis. One patient had stable disease for 12 months while receiving immunotherapy. We present genetic, histopathologic, and clinical characteristics for all cases of SCCOHT identified in the Slovenian population during a 30-year period. We report 2 novel germline SMARCA4 variants, possibly associated with high penetrance. We estimate the minimal incidence of SCCOHT to be 0.12 per 1 million per year.

Abstract 2577: Pre-cancerous ovarian cells harboring a familial SMARCA4 mutation acquire in vitro phenotypes associated with transformation in SSCOHT

Abstract Introduction: Small Cell Carcinoma of the Ovary, Hypercalcemic Type (SCCOHT) is an extremely rare but deadly ovarian cancer associated with mutations in the SMARCA4 gene. Using a unique population of ovarian cells derived from a familial carrier of an SCCOHT-associated SMARCA4 mutation, we sought to determine if non-cancerous cells would spontaneously transform during in vitro culture, thereby providing a model system for studying formation of SCCOHT. Methods: Ovarian cells derived from a familial carrier of a SMARCA4 mutation (P590, SMARCA4. c.3081+1G>T) were serially passaged in vitro and interrogated for acquisition of phenotypes consistent with cellular transformation. Loss of contact-dependent inhibition was interrogated with focus-forming assays in confluent monolayers. The ability of cells to escape anoikis and grow independently as spheroids was tested in attachment-free growth conditions using both single and aggregate spheroid growth assays. Senescence-associated β-galactosidase (SA-β-gal), cellular necrosis, and cellular apoptosis was also measured. All experiments were conducted in parallel with an age-matched cell population derived from a benign ovarian surgery (P583). In experiments to determine if these differences could be attributed to loss of functional SMARCA4, non-mutant P583 cells were cultured in the presence of the SWI/SNF inhibitor BRM014 and interrogated in focus-forming and attachment-free growth assays. Results: P590 cells passaged over 12 twelve times (approx. 40 cell divisions) continued to proliferate in culture. In contrast, non-mutant P583 cells failed to grow beyond 11-12 passages. With prolonged culture, P590 cells lost expression of SMARCA4 protein, while P583 cells retained SMARCA4 expression. P590 cells grown to confluency spontaneously formed foci of multicellular aggregates, while P583 cells did not. In attachment-free culture conditions, P590 cells readily formed spheroids from both early-passage and late-passage cells. In contrast, P583 formed small spheroids that failed to expand in culture. Surprisingly, both P590 and P583 cells displayed elevated SA-β-gal staining, with neither cell populations showing elevated necrosis or apoptosis markers. Treating P583 cells with BRM014 increased focus formation and spheroid growth similar to that of mutant cells. Conclusions: SCCOHT is extremely rare, with very few representative samples useful for developing early-stage markers or improved therapeutics. Long-term culture of ovarian cells harboring inactivated forms of SMARCA4 result in the acquisition of several phenotypes consistent with early stages of cellular transformation. Our data suggest that mutating or inactivating SMARCA4 in non-transformed ovarian cells may be a way to create novel research tools for studying formation of SCCOHT. This work was supported by DoD award W81XWH-21-1-0512 Citation Format: Sonali Joshi, Shawn Campbell, Yukie Bean, Tanja Pejovic, Adam Krieg. Pre-cancerous ovarian cells harboring a familial SMARCA4 mutation acquire in vitro phenotypes associated with transformation in SSCOHT [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 2577.

Abstract 3277: SWI/SNF inactivation vulnerability

Abstract Genetic inactivation in specific SWI/SNF complex members induce sensitivity to the inhibition of KDM6A/UTX and KDM6B/JMJD3 in cancer. Despite the genetic inactivation of the tumor suppressor SMARCA4 is frequently found in cancer, there are no therapies that effectively target SMARCA4-deficient tumors. In our previous work, we reported that unlike the cells with activated MYC oncogene, cells with SMARCA4 inactivation are refractory to the histone deacetylase inhibitor, SAHA, leading to the aberrant accumulation of H3K27me3. In this context, SMARCA4 deficient cells showed an impaired transactivation and significantly reduced levels of the histone H3K27me3 specific demethylases, KDM6A/UTX and KDM6B/JMJD3, and their inhibition compromises cell viability specifically in SMARCA4 mutant cells. Furthermore, the in vivo administration of KDM6s inhibitor (GSK-J4) to mice orthotopically implanted with SMARCA4 mutant lung cancer cell lines or primary tumors of small cell carcinoma of the ovary, hypercalcemic type (SCCOHT), showed a strong anti-tumor effect, highlighting the vulnerability of the SMARCA4 deficient tumors to KDM6s inhibition as a biomarker that could be exploited for treating SMARCA4-mutant cancer patients (Romero OA, Vilarrubi A, et al. SMARCA4 deficient tumors are vulnerable to KDM6A/UTX and KDM6B/JMJD3 blockade. Nat Comm 12, 4319, 2021). Considering our previous observations, and due to the biological role of SMARCA4 as a core component of the SWI/SNF chromatin-remodeling complex, whose members are genetically inactivated in approximately 20% of all human cancers, we wanted to determine the potential response to KDM6s inhibitors in a context of genetic alterations in genes encoding for the other subunits of this remodeling complex. For this propose, we have integrated state of the art technology like genome-wide chromatin modification analysis (ChIP-seq) and transcriptome analysis (RNA-seq), using human cancer cell lines and preclinical models of different cancer types with genetic inactivation at different SWI/SNF-complex members, including mouse models such as orthoxenografts, to design a personalized epigenetic treatment based on the genetic background. Our results showed that, like SMARCA4 deficient cells, specific mutations at some, but not all, SWI/SNF components induce refractoriness to SAHA, aberrant increase of H3K27me3 mark and sensitizes cancer cells to KDM6 inhibitor accompanied with significantly reduced levels of KDM6A and KDM6B expression. These results suggest a strong functional relationship between KDM6A/6B activity and the SWI/SNF-complex, in the control of gene expression and cancer development. These results will be of great value for the stratification of tumors according to their genetic background for tailored treatments, opening the possibility to use SWI/SNF mutations as potential biomarkers for personalized epigenetic-based therapeutics in cancer. Citation Format: Andrea Vilarrubi, Fernando Setien, Eva Pros, Pedro P. Medina, Antonio Gomez, Alberto Villanueva, Octavio A. Romero, Montse Sanchez-Cespedes. SWI/SNF inactivation vulnerability [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3277.

The value of SOX2 in the differential diagnosis of SMARCA4 (BRG1)-deficient uterine neoplasms

SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 4 (SMARCA4/BRG1)-deficient undifferentiated uterine sarcoma (SDUS) is a recently described uterine sarcoma. It is characterized by predominantly rhabdoid or large epithelioid cells with abundant cytoplasm and varying components of small and spindle cells, resembling the 'large cell variant' of small cell carcinoma of the ovary, hypercalcemic type (SCCOHT). In addition, SMARCA4-inactivating mutations have been described as the driver mutations in SDUS. However, undifferentiated endometrial carcinoma (UDEC) and dedifferentiated endometrial carcinoma(DDEC) may show some clinical and morphological overlaps with SDUS, and about 20% of reported UDEC/DDEC cases also have loss expression of SMARCA4. SDUS is a very aggressive disease and universally lethal in all reported cases. Differentiating SDUS from UDEC/DDEC is relevant for the prognosis, pathogenesis, and possible targeted therapies for the disease. In this study, we compared the clinical, morphological, immunohistochemical, and molecular characteristics of 10 tumors including 2 SDUS, 2 SCCOHT, 1 uterine carcinoma with neuroendocrine differentiation (UDEC?), and 5 UDEC/DDEC. All 5 UDEC/DDEC cases showed strong and diffuse nuclear positivity for SOX2, while all SCCOHT and SDUS cases were completely negative. We concluded that SOX2 could be a useful marker for the differential diagnosis between SDUS and UDEC/DDEC.

Multi-modality therapies for advanced small cell carcinoma of the ovary, hypercalcemic type (SCCOHT): three case reports and literature review

Background: Small-cell carcinoma of the ovary, hypercalcemic type (SCCOHT) is a rare but highly undifferentiated, aggressive malignancy that primarily affects young women. Most SCCOHT patients present with advanced disease and have a very poor prognosis. Although several therapeutic regimens have been proposed, there is no consensus on the optimal treatment strategy. Case: Herein, we describe three cases of advanced-stage SCCOHT aged from16 to 36 treated with cytoreductive surgery and chemotherapy with or without immune checkpoint blockade treatment. With different strategy, the patients showed utterly different outcomes. Conclusion: The cases highlight the importance of prompt diagnosis as well as early, aggressive, and combined modality treatment of SCCOHT. We believe that improved therapies could result in more young patients surviving SCCOHT.

SWI/SNF‐deficient undifferentiated malignancies: where to draw the line†

Alterations in chromatin remodelling genes are increasingly recognised as drivers of undifferentiated malignancies. In atypical teratoid/rhabdoid tumours (ATRTs) and extracranial rhabdoid tumours (ECRTs), inactivation of SMARCB1 underlies >95% of cases. In the remainder, the culprit is another SWI/SNF family member, SMARCA4. By contrast, in small cell carcinoma of the ovary hypercalcaemic type (SCCOHT), SMARCA4 deficiency is by far the most common driver mechanism, while SMARCB1 alterations are rarely seen. It is unclear why alterations are so heavily weighted towards one or another subunit based on site alone, but both have become essential markers for the diagnosis and management of these undifferentiated lesions. Core SMARCA4-deficient undifferentiated malignancies share an aggressive clinical course and show an overlapping morphologic phenotype. In their study, Andrianteranagna, Cyrta and colleagues used DNA methylation and gene expression profiling to compare two subsets of SMARCA4-deficient malignancies diagnosed as SCCOHT and ECRT. Their work gives further insight into the subtle molecular spectrum of SMARCA4-deficient tumours, and their distinction from ATRT and ECRT with SMARCB1 inactivation. The characterisation of these molecular features is likely to play an important role in the future as we try to establish a clinically meaningful framework for the diagnosis and management of these lesions. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

SMARCA4 deficient tumours are vulnerable to KDM6A/UTX and KDM6B/JMJD3 blockade

Despite the genetic inactivation of SMARCA4, a core component of the SWI/SNF-complex commonly found in cancer, there are no therapies that effectively target SMARCA4-deficient tumours. Here, we show that, unlike the cells with activated MYC oncogene, cells with SMARCA4 inactivation are refractory to the histone deacetylase inhibitor, SAHA, leading to the aberrant accumulation of H3K27me3. SMARCA4-mutant cells also show an impaired transactivation and significantly reduced levels of the histone demethylases KDM6A/UTX and KDM6B/JMJD3, and a strong dependency on these histone demethylases, so that its inhibition compromises cell viability. Administering the KDM6 inhibitor GSK-J4 to mice orthotopically implanted with SMARCA4-mutant lung cancer cells or primary small cell carcinoma of the ovary, hypercalcaemic type (SCCOHT), had strong anti-tumour effects. In this work we highlight the vulnerability of KDM6 inhibitors as a characteristic that could be exploited for treating SMARCA4-mutant cancer patients.

Atypical teratoid/rhabdoid tumors (ATRTs) with SMARCA4 mutation are molecularly distinct from SMARCB1-deficient cases

Atypical teratoid/rhabdoid tumors (ATRTs) are very aggressive childhood malignancies of the central nervous system. The underlying genetic cause are inactivating bi-allelic mutations in SMARCB1 or (rarely) in SMARCA4. ATRT-SMARCA4 have been associated with a higher frequency of germline mutations, younger age, and an inferior prognosis in comparison to SMARCB1 mutated cases. Based on their DNA methylation profiles and transcriptomics, SMARCB1 mutated ATRTs have been divided into three distinct molecular subgroups: ATRT-TYR, ATRT-SHH, and ATRT-MYC. These subgroups differ in terms of age at diagnosis, tumor location, type of SMARCB1 alterations, and overall survival. ATRT-SMARCA4 are, however, less well understood, and it remains unknown, whether they belong to one of the described ATRT subgroups. Here, we examined 14 ATRT-SMARCA4 by global DNA methylation analyses. We show that they form a separate group segregating from SMARCB1 mutated ATRTs and from other SMARCA4-deficient tumors like small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) or SMARCA4 mutated extra-cranial malignant rhabdoid tumors. In contrast, medulloblastoma (MB) samples with heterozygous SMARCA4 mutations do not group separately, but with established MB subgroups. RNA sequencing of ATRT-SMARCA4 confirmed the clustering results based on DNA methylation profiling and displayed an absence of typical signature genes upregulated in SMARCB1 deleted ATRT. In summary, our results suggest that, in line with previous clinical observations, ATRT-SMARCA4 should be regarded as a distinct molecular subgroup.

Re-assigning the histologic identities of COV434 and TOV-112D ovarian cancer cell lines

ObjectiveThe development of effective cancer treatments depends on the availability of cell lines that faithfully recapitulate the cancer in question. This study definitively re-assigns the histologic identities of two ovarian cancer cell lines, COV434 (originally described as a granulosa cell tumour) and TOV-112D (originally described as grade 3 endometrioid carcinoma), both of which were recently suggested to represent small cell carcinoma of the ovary, hypercalcemic type (SCCOHT), based on their shared gene expression profiles and sensitivity to EZH2 inhibitors. MethodsFor COV434 and TOV-112D, we re-reviewed the original pathology slides and obtained clinical follow-up on the patients, when available, and performed immunohistochemistry for SMARCA4, SMARCA2 and additional diagnostic markers on the original formalin-fixed, paraffin-embedded (FFPE) clinical material, when available. For COV434, we further performed whole exome sequencing and validated SMARCA4 mutations by Sanger sequencing. We studied the growth of the cell lines at baseline and upon re-expression of SMARCA4 in vitro for both cell lines and evaluated the serum calcium levels in vivo upon injection into immunodeficient mice for COV434 cells. ResultsThe available morphological, immunohistochemical, genetic, and clinical features indicate COV434 is derived from SCCOHT, and TOV-112D is a dedifferentiated carcinoma. Transplantation of COV434 into mice leads to increased serum calcium level. Re-expression of SMARCA4 in either COV434 and TOV-112D cells suppressed their growth dramatically. ConclusionsCOV434 represents a bona fide SCCOHT cell line. TOV-112D is a dedifferentiated ovarian carcinoma cell line.

Elucidating the immune responsiveness of small cell carcinoma of the ovary, hypercalcemic type

Objective: A recent case series described favorable response of small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) to antiprogrammed death-1 (PD-1) immune checkpoint therapy in 4 patients. In this study, we aimed to examine patterns of immunohistochemical (IHC) expression of PD-L1 in SCCOHT and correlate these with available clinical response to immunotherapy.

Germline mutations of SMARCA4 in small cell carcinoma of the ovary, hypercalcemic type and in SMARCA4-deficient undifferentiated uterine sarcoma: Clinical features of a single family and comparison of large cohorts

Objective: Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) and SMARCA4-deficient undifferentiated uterine sarcoma (SMARCA4-DUS) are rare and aggressive tumors, primarily affecting pre- and perimenopausal women. Inactivating SMARCA4 mutations are thought to be the driving molecular events in the majority of these tumors. Here, we report the clinical course of a family with germline SMARCA4 mutation and compare large cohorts of these rare tumor types.

Arginine Depletion Therapy with ADI-PEG20 Limits Tumor Growth in Argininosuccinate Synthase-Deficient Ovarian Cancer, Including Small-Cell Carcinoma of the Ovary, Hypercalcemic Type.

Many rare ovarian cancer subtypes, such as small-cell carcinoma of the ovary, hypercalcemic type (SCCOHT), have poor prognosis due to their aggressive nature and resistance to standard platinum- and taxane-based chemotherapy. The development of effective therapeutics has been hindered by the rarity of such tumors. We sought to identify targetable vulnerabilities in rare ovarian cancer subtypes. We compared the global proteomic landscape of six cases each of endometrioid ovarian cancer (ENOC), clear cell ovarian cancer (CCOC), and SCCOHT to the most common subtype, high-grade serous ovarian cancer (HGSC), to identify potential therapeutic targets. IHC of tissue microarrays was used as validation of arginosuccinate synthase (ASS1) deficiency. The efficacy of arginine-depriving therapeutic ADI-PEG20 was assessed in vitro using cell lines and patient-derived xenograft mouse models representing SCCOHT. Global proteomic analysis identified low ASS1 expression in ENOC, CCOC, and SCCOHT compared with HGSC. Low ASS1 levels were validated through IHC in large patient cohorts. The lowest levels of ASS1 were observed in SCCOHT, where ASS1 was absent in 12 of 31 cases, and expressed in less than 5% of the tumor cells in 9 of 31 cases. ASS1-deficient ovarian cancer cells were sensitive to ADI-PEG20 treatment regardless of subtype in vitro. Furthermore, in two cell line mouse xenograft models and one patient-derived mouse xenograft model of SCCOHT, once-a-week treatment with ADI-PEG20 (30 mg/kg and 15 mg/kg) inhibited tumor growth in vivo. Preclinical in vitro and in vivo studies identified ADI-PEG20 as a potential therapy for patients with rare ovarian cancers, including SCCOHT.

Abstract LB-038: Novel functional insights revealed by distinct protein-protein interactions of the residual SWI/SNF complex in SMARCA4-deficient small cell carcinoma of the ovary, hypercalcemic type

Abstract Chromatin remodeling plays a critical role in tumor suppression as demonstrated by 20% of human cancers bearing inactivating mutations in SWI/SNF chromatin remodeling complex members. Mutations in different SWI/SNF subunits drive a variety of adult and pediatric tumor types, including non-small cell lung cancers, rhabdoid tumors, medulloblastomas, and ovarian cancers. Small cell carcinoma of the ovary hypercalcemic type (SCCOHT) is an aggressive subtype of ovarian cancer occurring in young women. Nearly all (>98%) SCCOHTs have inactivating mutations in SMARCA4, which encodes 1 of 2 mutually exclusive catalytic subunits of the SWI/SNF complex. Less than half of SCCOHT patients survive 5 years despite aggressive surgery and multimodal chemotherapy. Empirical support for effective SCCOHT treatments is scarce, in part because of the poor understanding of SCCOHT tumorigenesis. To gain insight into the functional consequences of SWI/SNF subunit loss, we defined SWI/SNF composition and its protein-protein interactions (PPIs) by immunoprecipitation and mass spectrometry (IP-MS) of SWI/SNF subunits in 3 SCCOHT cell lines. Comparing these results to a cell line containing a wild-type SWI/SNF complex, the interaction of most canonical core SWI/SNF subunits was observed in all SCCOHT cell lines at a lower abundance. The SCCOHT SWI/SNF also lacked ATPase module subunits and showed a drastic reduction in PBAF-specific subunit interactions. The wild-type and SCCOHT SWI/SNF subunits immunoprecipitated a shared set of 26 proteins, including core SWI/SNF subunits and RNA processing proteins. We observed 131 proteins exclusively interacting with the wild-type SWI/SNF complex including isoform-specific SWI/SNF subunits, members of the NuRD complex, and members of the MLL3/4 complex. We observed 60 PPIs exclusive to the SCCOHT residual SWI/SNF shared in at least 2 of the 3 SCCOHT cell lines, including many proteins involved in RNA processing. Differential interactions with the residual SWI/SNF complex in SCCOHT may further elucidate altered functional consequences of SMARCA4 mutations in these tumors as well as identify synthetic lethal targets that translate to other SWI/SNF-deficient tumors. Citation Format: Elizabeth Raupach, Krystine Garcia-Mansfield, Ritin Sharma, Apurva Hegde, Victoria David-Dirgo, Yemin Wang, Chae Young Shin, Lan Tao, Salvatore Facista, Rayvon Moore, Jessica Lang, Victoria Zismann, Krystal Orlando, Monique Spillman, Anthony Karnezis, Lynda Bennett, David Huntsman, Jeffrey Trent, William Hendricks, Bernard Weissman, Patrick Pirrotte. Novel functional insights revealed by distinct protein-protein interactions of the residual SWI/SNF complex in SMARCA4-deficient small cell carcinoma of the ovary, hypercalcemic type [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-038.

The novel reversible LSD1 inhibitor SP-2577 promotes anti-tumor immunity in SWItch/Sucrose-NonFermentable (SWI/SNF) complex mutated ovarian cancer.

Mutations of the SWI/SNF chromatin remodeling complex occur in 20% of all human cancers, including ovarian cancer. Approximately half of ovarian clear cell carcinomas (OCCC) carry mutations in the SWI/SNF subunit ARID1A, while small cell carcinoma of the ovary hypercalcemic type (SCCOHT) presents with inactivating mutations of the SWI/SNF ATPase SMARCA4 alongside epigenetic silencing of the ATPase SMARCA2. Loss of these ATPases disrupts SWI/SNF chromatin remodeling activity and may also interfere with the function of other histone-modifying enzymes that associate with or are dependent on SWI/SNF activity. One such enzyme is lysine-specific histone demethylase 1 (LSD1/KDM1A), which regulates the chromatin landscape and gene expression by demethylating proteins such as histone H3. Cross-cancer analysis of the TCGA database shows that LSD1 is highly expressed in SWI/SNF-mutated tumors. SCCOHT and OCCC cell lines have shown sensitivity to the reversible LSD1 inhibitor SP-2577 (Seclidemstat), suggesting that SWI/SNF-deficient ovarian cancers are dependent on LSD1 activity. Moreover, it has been shown that inhibition of LSD1 stimulates interferon (IFN)-dependent anti-tumor immunity through induction of endogenous retroviral elements and may thereby overcome resistance to checkpoint blockade. In this study, we investigated the ability of SP-2577 to promote anti-tumor immunity and T-cell infiltration in SCCOHT and OCCC cell lines. We found that SP-2577 stimulated IFN-dependent anti-tumor immunity in SCCOHT and promoted the expression of PD-L1 in both SCCOHT and OCCC. Together, these findings suggest that the combination therapy of SP-2577 with checkpoint inhibitors may induce or augment immunogenic responses of SWI/SNF-mutated ovarian cancers and warrants further investigation.

Small cell carcinoma of the ovary hypercalcemic type (SCCOHT): Comprehensive management of a newly diagnosed young adult

SCCOHT is an aggressive malignancy linked to alterations of SMARCA4. We describe the diagnosis and therapy of a 32 year old who received multi-agent chemotherapy and underwent a second look operation with HIPEC followed by high-dose chemotherapy with stem cell transplant. Supportive care, oncofertility, and genetic counseling are described.