Pattern of SMARCB1 (INI1) and SMARCA4 (BRG1) in poorly differentiated endometrioid adenocarcinoma of the uterus: analysis of a series with emphasis on a novel SMARCA4-deficient dedifferentiated rhabdoid variant

Preclinical 3D model screening reveals digoxin as an effective therapy for a rare and aggressive type of endometrial cancer

OBJECTIVE

Dedifferentiated endometrial carcinoma (DDEC) characterized by SWItch/Sucrose Non-Fermentable (SWI/SNF) complex inactivation is a highly aggressive type of endometrial cancer without effective systemic therapy options. Its uncommon nature and aggressive disease trajectory pose significant challenges for therapeutic progress. To address this obstacle, we focused on developing preclinical models tailored to this tumor type and established patient tumor-derived three-dimensional (3D) spheroid models of DDEC.

METHODS

High-throughput drug repurposing screens were performed on in vitro 3D spheroid models of DDEC cell lines (SMARCA4-inactivated DDEC-1 and ARID1A/ARID1B co-inactivated DDEC-2). The dose-response relationships of the identified candidate drugs were evaluated in vitro, followed by in vivo evaluation using xenograft models of DDEC-1 and DDEC-2.

RESULTS

Drug screen in 3D models identified multiple cardiac glycosides including digoxin and digitoxin as candidate drugs in both DDEC-1 and DDEC-2. Subsequent in vitro dose-response analyses confirmed the inhibitory activity of digoxin and digitoxin with both drugs showing lower IC50 in DDEC cells compared to non-DDEC endometrial cancer cells. In in vivo xenograft models, digoxin significantly suppressed the growth of DDEC tumors at clinically relevant serum concentrations.

CONCLUSION

Using biologically precise preclinical models of DDEC derived from patient tumor samples, our study identified digoxin as an effective drug in suppressing DDEC tumor growth. These findings provide compelling preclinical evidence for the use of digoxin as systemic therapy for SWI/SNF-inactivated DDEC, which may also be applicable to other SWI/SNF-inactivated tumor types.

NUT carcinoma and thoracic SMARCA4-deficient undifferentiated tumour: facts and controversies

NUT carcinoma and thoracic SMARCA4-deficient undifferentiated tumour are unique entities in the 5th edition of the World Health Organisation (WHO) Classification of Thoracic Tumours, whose definitions include molecular genetic abnormalities. These aggressive tumours require rapid work-ups on biopsies, but a broad list of differential diagnoses poses challenges for practising pathologists. This review provides an update on their key clinicopathological and molecular characteristics, as well as controversies regarding tumour classification and diagnostic strategy. Phenotypical assessment plays a substantial role in diagnosis because recurrent and predictable clinicopathological findings exist, including robust immunohistochemical phenotypes. Accurate diagnosis is crucial for appropriate management and a clearer understanding of the disease.

Dedifferentiated Endometrial Carcinoma: A Rare Aggressive Neoplasm-Clinical, Morphological and Immunohistochemical Features

Dedifferentiated endometrioid adenocarcinoma is characterised by the coexistence of an undifferentiated carcinoma and a low-grade endometrioid adenocarcinoma. The low-grade component in this subtype of endometrial carcinoma is Grade 1 or 2 according to the Federation of Gynaecology and Obstetrics (FIGO) grading system. The coexistence of low-grade endometrial carcinoma and solid undifferentiated carcinoma can cause diagnostic problems on histological examination. In fact, this combination can often be mistaken for a more common Grade 2 or Grade 3 endometrial carcinoma. Therefore, this subtype of uterine carcinoma can often go under-recognised. An accurate diagnosis of dedifferentiated endometrial carcinoma is mandatory because of its poorer prognosis compared to Grade 3 endometrial carcinoma, with a solid undifferentiated component that can amount to as much as 20% of the entire tumour. The aim of this review is to provide clinical, immunohistochemical, and molecular data to aid with making an accurate histological diagnosis and to establish whether there are any findings which could have an impact on the prognosis or therapeutic implications of this rare and aggressive uterine neoplasm.

Establishment and validation of preclinical models of SMARCA4-inactivated and ARID1A/ARID1B co-inactivated dedifferentiated endometrial carcinoma

OBJECTIVE

Dedifferentiated endometrial cancer (DDEC) is an uncommon and clinically highly aggressive subtype of endometrial cancer characterized by genomic inactivation of SWItch/Sucrose Non-Fermentable (SWI/SNF) complex protein. It responds poorly to conventional systemic treatment and its rapidly progressive clinical course limits the therapeutic windows to trial additional lines of therapies. This underscores a pressing need for biologically accurate preclinical tumor models to accelerate therapeutic development.

METHODS

DDEC tumor from surgical samples were implanted into immunocompromised mice for patient-derived xenograft (PDX) and cell line development. The histologic, immunophenotypic, genetic and epigenetic features of the patient tumors and the established PDX models were characterized. The SMARCA4-deficienct DDEC model was evaluated for its sensitivity toward a KDM6A/B inhibitor (GSK-J4) that was previously reported to be effective therapy for other SMARCA4-deficient cancer types.

RESULTS

All three DDEC models exhibited rapid growth in vitro and in vivo, with two PDX models showing spontaneous development of metastases in vivo. The PDX tumors maintained the same undifferentiated histology and immunophenotype, and exhibited identical genomic and methylation profiles as seen in the respective parental tumors, including a mismatch repair (MMR)-deficient DDEC with genomic inactivation of SMARCA4, and two MMR-deficient DDECs with genomic inactivation of both ARID1A and ARID1B. Although the SMARCA4-deficient cell line showed low micromolecular sensitivity to GSK-J4, no significant tumor growth inhibition was observed in the corresponding PDX model.

CONCLUSIONS

These established patient tumor-derived models accurately depict DDEC and represent valuable preclinical tools to gain therapeutic insights into this aggressive tumor type.

Diagnosis of thoracic SMARCA4-deficient undifferentiated tumor in cytology

INTRODUCTION

Although alterations in SMARCA4-deficient occur in non-small cell lung carcinoma (SD-NSCLC), thoracic SMARCA4-deficient undifferentiated tumor (TSDUT) is recognized as a distinct entity in the 2021 World Health Organization Classification of Thoracic Tumors because of unique morphologic, immunophenotypic and molecular features, and worse survival compared with SD-NSCLC. Cytologic diagnosis of TSDUT is clinically important because of its aggressive behavior and because it is often diagnosed by fine-needle aspiration because TSDUTs are usually unresectable at presentation. Here, we identify cytologic features that can be used for recognition of TSDUT and distinction from SD-NSCLC.

MATERIALS AND METHODS

Cytomorphologic features were investigated in cytology specimens from patients with TSDUT (n = 11) and compared with a control group of patients with SD-NSCLC (n = 20).

RESULTS

The presence of classic rhabdoid morphology, at least focally, was entirely specific for TSDUT (n = 6, 55%) compared with SD-NSCLC (n = 0) in this study. TSDUT more frequently showed tumor necrosis (n = 11, 100% vs. n = 8, 40%; p = .001), dominant single-cell pattern on aspirate smears or touch preparation slides (n = 8 [of 9], 80% vs. n = 3, 15%; p = .010), nuclear molding (n = 5, 45% vs. n = 1, 5%; p = .013), and indistinct cell borders (n = 11, 100% vs. n = 5, 25%; P < .001) compared with SD-NSCLC, respectively.

CONCLUSIONS

Cytomorphologic features occurring more frequently in TSDUT include tumor necrosis, dominant single-cell pattern, nuclear molding indistinct cell borders, and focal rhabdoid cells. Presence of these features in a cytology specimen of an undifferentiated tumor, particularly in a patient with a thoracic mass, should raise suspicion for TSDUT and prompt appropriate ancillary workup.

SMARCB1/INI1 loss in skull base conventional chordomas: a clinicopathological and molecular analysis

Introduction

The loss of SMARCB1/INI1 protein has been recently described in poorly differentiated chordoma, an aggressive and rare disease variant typically arising from the skull base.

Methods

Retrospective study aimed at 1) examining the differential immunohistochemical expression of SMARCB1/INI1 in conventional skull base chordomas, including the chondroid subtype; 2) evaluating SMARCB1 gene deletions/copy number gain; and 3) analyzing the association of SMARCB1/INI1 expression with clinicopathological parameters and patient survival.

Results

65 patients (35 men and 30 women) affected by conventional skull base chordoma, 15 with chondroid subtype, followed for >48 months after surgery were collected. Median age at surgery was 50 years old (range 9-79). Mean tumor size was 3.6 cm (range 2-9.5). At immunohistochemical evaluation, a partial loss of SMARCB1/INI1 (>10% of neoplastic examined cells) was observed in 21 (32.3%) cases; the remaining 43 showed a strong nuclear expression. Fluorescence in situ hybridization (FISH) analysis was performed in 15/21 (71.4%) cases of the chordomas with partial SMARCB1/INI1 loss of expression. Heterozygous deletion of SMARCB1 was identified in 9/15 (60%) cases and was associated to copy number gain in one case; no deletion was found in the other 6 (40%) cases, 3 of which presenting with a copy number gain. No correlations were found between partial loss of SMARCB1/INI1 and the clinicopathological parameters evaluated (i.e., age, tumor size, gender, tumor size and histotype). Overall 5-year survival and 5-year disease-free rates were 82% and 59%, respectively. According to log-rank test analysis the various clinico-pathological parameters and SMARCB1/INI1 expression did not impact on overall and disease free-survival.

Discussion

Partial loss of SMARCB1/INI1, secondary to heterozygous deletion and/or copy number gain of SMARCB1, is not peculiar of aggressive forms, but can be identified by immunohistochemistry in a significant portion of conventional skull base chordomas, including the chondroid subtype. The variable protein expression does not appear to correlate with clinicopathological parameters, nor survival outcomes, but still, it could have therapeutic implications.

Adenomyosis and Its Possible Malignancy: A Review of the Literature

Cancer arising from adenomyosis is very rare, with transformation occurring in only 1% of cases and in older individuals. Adenomyosis, endometriosis and cancers may share a common pathogenic mechanism that includes hormonal factors, genetic predisposition, growth factors, inflammation, immune system dysregulation, environmental factors and oxidative stress. Endometriosis and adenomyosis both exhibit malignant behaviour. The most common risk factor for malignant transformation is prolonged exposure to oestrogens. The golden standard for diagnosis is histopathology. Colman and Rosenthal emphasised the most important characteristics in adenomyosis-associated cancer. Kumar and Anderson emphasised the importance of demonstrating a transition between benign and malignant endometrial glands in cancer arising from adenomyosis. As it is very rare, it is difficult to standardize treatment. In this manuscript, we try to emphasize some aspects regarding the management strategy, as well as how heterogenous the studies from the literature are in terms of prognosis in both cancers that develop from adenomyosis or those that are only associated with adenomyosis. The pathogenic mechanisms of transformation remain unclear. As these types of cancer are so rare, there is no standardised treatment. A novel target in the diagnosis and treatment of gynaecological malignancies associated with adenomyosis is also being studied for the development of new therapeutic concepts.

SWI/SNF complexes and cancers

Epigenetics refers to the study of genetic changes that can affect gene expression without altering the underlying DNA sequence, including DNA methylation, histone modification, chromatin remodelling, X chromosome inactivation and non-coding RNA regulation. Of these, DNA methylation, histone modification and chromatin remodelling constitute the three classical modes of epigenetic regulation. These three mechanisms alter gene transcription by adjusting chromatin accessibility, thereby affecting cell and tissue phenotypes in the absence of DNA sequence changes. In the presence of ATP hydrolases, chromatin remodelling alters the structure of chromatin and thus changes the transcription level of DNA-guided RNA. To date, four types of ATP-dependent chromatin remodelling complexes have been identified in humans, namely SWI/SNF, ISWI, INO80 and NURD/MI2/CHD. SWI/SNF mutations are prevalent in a wide variety of cancerous tissues and cancer-derived cell lines as discovered by next-generation sequencing technologies.. SWI/SNF can bind to nucleosomes and use the energy of ATP to disrupt DNA and histone interactions, sliding or ejecting histones, altering nucleosome structure, and changing transcriptional and regulatory mechanisms. Furthermore, mutations in the SWI/SNF complex have been observed in approximately 20% of all cancers. Together, these findings suggest that mutations targeting the SWI/SNF complex may have a positive impact on tumorigenesis and cancer progression.

SMARCA4-deficient Undifferentiated Uterine Sarcoma: Clinicopathological Features of an Emerging Entity

SMARCA4-deficient undifferentiated uterine sarcoma is a recently described molecularly defined entity among the subset of aggressive undifferentiated uterine tumors. Mutation in the SMARCA4 gene is a key driver alteration, as also seen in small cell carcinoma of ovary, hypercalcemic type (SCCOHT) and thoracic undifferentiated carcinoma. Limited number of cases of SMARCA4-deficient undifferentiated uterine sarcoma has been reported in literature. We hereby describe a case of this distinct entity in a 52-year-old woman. Histomorphological examination showed sheets of monomorphic epithelioid cells with a variable proportion of cells displaying rhabdoid features, brisk mitotic activity, and lymphovascular invasion. A panel of immunohistochemical markers was required to exclude the differential diagnoses. The tumor was microsatellite stable. Loss of SMARCA4 expression and intact expression of INI1 in tumor cells by immunohistochemistry (IHC) confirmed the diagnosis of SMARCA4- deficient undifferentiated uterine sarcoma. The patient had a rapidly progressive clinical course.

Malignant undifferentiated and rhabdoid tumors of the gastroesophageal junction and esophagus with SMARCA4 loss: a case series

Undifferentiated SMARCA4-deficient carcinoma of the esophagus and gastroesophageal junction is a rare, highly aggressive, and diagnostically challenging malignancy. Here we present a case series of high-grade undifferentiated malignant neoplasms of the esophagus and gastroesophageal junction that share SMARCA4 loss by immunohistochemistry and demonstrate a rhabdoid phenotype. Five cases are presented, including 4 men and 1 woman with an age range of 48-79 years. Interestingly, only one case showed intestinal metaplasia (Barrett's esophagus) and no cases demonstrated glandular dysplasia or glandular differentiation. In all, the lesional cells were immunoreactive with antibodies to keratins (3/5), CD34 (2/4), and CD138 (4/5). SMARCA4 expression was diffusely lost in all cases, whereas SMARCB1 expression was intact. OncoScan™ assay demonstrated loss of SMARCA4 in all cases analyzed. Additional OncoScan™ findings included abnormalities of CDKN2A in 2 of 3 cases, abnormalities of TP53 in 2 of 3 cases, and abnormalities of PTPRD in 2 of 3 cases, among other abnormalities.

ARID1A, BRG1, and INI1 deficiency in undifferentiated and dedifferentiated endometrial carcinoma: a clinicopathologic, immunohistochemical, and next-generation sequencing analysis of a case series from a single institution

Undifferentiated/dedifferentiated endometrial carcinomas (UDEC and DDEC) are rare, aggressive uterine neoplasms, with no specific line of differentiation. A significant proportion of these cases feature mutations of SWI/SNF chromatin remodeling complex members, including ARID1A, SMARCA4, and SMARCB1 genes. To study these entities more comprehensively, we identified 10 UDECs and 10 DDECs from our pathology archives, obtained clinicopathologic findings and follow-up data, and performed immunohistochemical studies for ARID1A, BRG1 (SMARCA4), and INI1 (SMARCB1) proteins. In addition, we successfully conducted targeted next-generation sequencing for 23 samples, including 7 UDECs, and 7 undifferentiated and 9 well/moderately-differentiated components of DDECs. Cases consisted of 18 hysterectomies and 2 curettage/biopsy specimens. Patient age ranged from 47 to 77 years (median, 59 years), with a median tumor size of 8.0 cm (range, 2.5-13.0 cm). All cases demonstrated lymphovascular invasion and the majority (13/20) were FIGO stage III-IV. By immunohistochemistry, ARID1A loss was observed in 15 cases, BRG1 loss in 4, and all cases had intact INI1 expression. A trend for enrichment of the undifferentiated component of DDECs for ARID1A loss was seen, although not statistically significant. Sequencing revealed frequent pathogenic mutations in PTEN, PIK3CA, ARID1A, CTNNB1, and RNF43, a recurrent MAX pathogenic mutation, and MYC and 12p copy number gains. In DDECs, the undifferentiated component featured a higher tumor mutational burden compared to the well/moderately-differentiated component; however, the mutational landscape largely overlapped. Overall, our study provides deep insights into the mutational landscape of UDEC/DDEC, SWI/SNF chromatin remodeling complex member status, and their potential relationships with tumor features.

Endometrial neuroendocrine carcinoma and undifferentiated carcinoma are distinct entities with overlap in neuroendocrine marker expression

AIMS

Dedifferentiated/undifferentiated endometrial carcinomas (DDEC/UDEC) frequently harbor genomic activation of SWItch/Sucrose Non-Fermentable (SWI/SNF) complex proteins, and can show histologic overlap with neuroendocrine carcinoma (NEC). This study compares the expression of neuroendocrine markers, SWI/SNF proteins and mismatch repair (MMR) proteins in DDEC/UDEC and NEC.

METHODS AND RESULTS

The expressions of synaptophysin, chromogranin, CD56, ARID1A, ARID1B, SMARCA4, SMARCB1 and MMR proteins were evaluated by immunohistochemistry on 44 SWI/SNF-deficient DDEC/UDEC and 15 NEC. 33 of 44 (75%) DDEC/UDEC showed expression of at least one neuroendocrine marker with 18 of 44 (41%) expressing 2 or more neuroendocrine markers, whereas all 15 NEC showed expression of at least one neuroendocrine marker with 14 of 15 (93%) expressing 2 or more neuroendocrine markers. Neuroendocrine marker expression in DDEC/UDEC was typically focal when present, with an average extent of 17%, 4% and 8% for synaptophysin, chromogranin and CD56 in the positive cases respectively, in contrast to 73%, 40% and 62% in the positive NEC cases respectively. All 15 NEC showed intact expression of SWI/SNF proteins except for 1 that showed isolated loss of ARID1A. 38 of 44 DDEC/UDEC were MMR-abnormal (34 with loss of MLH1 and PMS2, 4 with loss of PMS2 alone) whereas all NEC retained MMR protein expression.

CONCLUSIONS

Our study demonstrates frequent but typically focal neuroendocrine marker expression in SWI/SNF-deficient DDEC/UDEC, while NECs typically express 2 or more neuroendocrine markers with diffuse expression in at least one marker. ARID1B, SMARCA4 and SMARCB1 immunohistochemistry can be used to aid differentiation between DDEC/UDEC and NEC.

Rare Subtype of Endometrial Cancer: Undifferentiated/Dedifferentiated Endometrial Carcinoma, from Genetic Aspects to Clinical Practice

Endometrial cancer (EC) is one of the most common gynecologic cancers worldwide. There were 417,367 newly diagnosed cases and 97,370 deaths due to this disease worldwide in 2020. The incidence rates have increased over time, especially in countries with rapid socioeconomic transitions, and EC has been the most prevalent gynecologic malignancy in Taiwan since 2012. The new EC molecular classifications of The Cancer Genome Atlas (TCGA) Research Network include clear-cell carcinoma, serous carcinoma, and carcinosarcoma, while undifferentiated/dedifferentiated EC (UDEC) is not mentioned, and most previous clinical trials for EC have not included UDEC. UDEC is rare, has an aggressive growth pattern, tends to be diagnosed at an advanced stage, and is resistant to conventional chemotherapy. In this review, case series or case reports on the clinical features and genomic/epigenetic and expression profiles on UDEC data are summarized in order to identify potential molecular targets for current and future research.

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 ovary, hypercalcemic type (SCCOHT). In addition, SMARCA4 inactivating mutations have been described as the driver mutations in SDUS. However, undifferentiated (UDEC) and dedifferentiated endometrial carcinomas (DDEC) may show some clinical and morphological overlaps with SDUS, and about 20% 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.

Proceedings of the North American Society of Head and Neck Pathology, Los Angeles, CA, March 20, 2022: SWI/SNF-deficient Sinonasal Neoplasms: An Overview

The pathology of poorly differentiated sinonasal malignancies has been the subject of extensive studies during the last decade, which resulted into significant developments in the definitions and histo-/pathogenetic classification of several entities included in the historical spectrum of "sinonasal undifferentiated carcinomas (SNUC)" and poorly differentiated unclassified carcinomas. In particular, genetic defects leading to inactivation of different protein subunits in the SWI/SNF chromatin remodeling complex have continuously emerged as the major (frequently the only) genetic player driving different types of sinonasal carcinomas. The latter display distinctive demographic, phenotypic and genotypic characteristics. To date, four different SWI/SNF-driven sinonasal tumor types have been recognized: SMARCB1(INI1)-deficient carcinoma (showing frequently non-descript basaloid, and less frequently eosinophilic, oncocytoid or rhabdoid undifferentiated morphology), SMARCB1-deficient adenocarcinomas (showing variable gland formation or yolk sac-like morphology), SMARCA4-deficient carcinoma (lacking any differentiation markers and variably overlapping with large cell neuroendocrine carcinoma and SNUC), and lastly, SMARCA4-deficient sinonasal teratocarcinosarcoma. These different tumor types display highly variable immunophenotypes with SMARCB1-deficient carcinomas showing variable squamous immunophenotype, while their SMARCA4-related counterparts lack such features altogether. While sharing same genetic defect, convincing evidence is still lacking that SMARCA4-deficient carcinoma and SMARCA4-deficient teratocracinosarcoma might belong to the spectrum of same entity. Available molecular studies revealed no additional drivers in these entities, confirming the central role of SWI/SNF deficiency as the sole driver genetic event in these aggressive malignancies. Notably, all studied cases lacked oncogenic IDH2 mutations characteristic of genuine SNUC. Identification and precise classification of these entities and separating them from SNUC, NUT carcinoma and other poorly differentiated neoplasms of epithelial melanocytic, hematolymphoid or mesenchymal origin is mandatory for appropriate prognostication and tailored therapies. Moreover, drugs targeting the SWI/SNF vulnerabilities are emerging in clinical trials.

SMARCA4-Deficient Undifferentiated Tumor Diagnosed on Adrenal Sampling

OBJECTIVES

SMARCA4-deficient undifferentiated tumor has distinct clinicopathologic features. We describe our experience with primary diagnosis on adrenal sampling.

METHODS

We collected six SMARCA4-deficient undifferentiated tumors diagnosed on adrenal sampling. Immunostains for SMARCA4, SF-1, inhibin, calretinin, S-100 protein, EMA, and TTF-1 were performed. A control group of 63 primary adrenocortical tumors was also immunostained.

RESULTS

Patients included four men and two women (aged 52-77 years). Five had unilateral adrenal masses and one bilateral (range, 2.4-9.6 cm). Five had pulmonary masses, and one had a midline mediastinal mass. All cases had a monotonous epithelioid appearance and variable rhabdoid morphology. Immunophenotypically, all six cases had loss of nuclear SMARCA4 expression and no staining for SF-1, inhibin, calretinin, or S-100 protein. Variable EMA immunoreactivity was present in four of six cases and focal nuclear TTF-1 expression in one of six. All 63 adrenocortical neoplasms had retained nuclear SMARCA4 expression.

CONCLUSIONS

SMARCA4-deficient undifferentiated tumor may present in the adrenal gland, and this series likely represents metastases from thoracic primaries. Because of the frequent absence of lineage marker expression, knowledge of the characteristic clinical presentation, the rhabdoid morphology, and the typical immunophenotype (loss of SMARCA4/BRG1) allow for appropriate distinction from adrenocortical carcinoma.

A Patient-Derived Xenograft Model of Dedifferentiated Endometrial Carcinoma: A Proof-of-Concept Study for the Identification of New Molecularly Informed Treatment Approaches

Simple Summary

Reliable animal models of human malignancies are paramount for preclinical studies of novel treatment approaches. Here, we successfully developed a patient-derived xenograft (PDX) model of dedifferentiated endometrial carcinoma (DEC)–an uncommon uterine malignancy that is generally unresponsive to standard chemo- and radiotherapy. The murine model–termed PDX-mLung–was established through the implantation of lung metastatic lesions obtained from a woman with DEC. Histologic and molecular findings revealed that PDX-mLung was highly similar to the parent human malignant lesions (both primary DEC and lung metastases). Importantly, molecular analyses revealed that PDX-mLung exhibited druggable alterations including a FGFR2 mutation and CCNE2 amplification. The former was targeted with the FGFR inhibitor lenvatinib while the latter with the cell cycle inhibitor palbociclib. The combination of the two drugs exhibited synergistic therapeutic effects against in vivo tumor growth. Collectively, these data illustrate the value of PDX models for preclinical testing of new molecularly informed therapies in difficult-to-treat gynecologic malignancies. Our results may also prompt further clinical research to examine whether the combination of lenvatinib and palbociclib has potential to improve clinical outcomes of women with DEC.

Abstract

Conventional treatment of dedifferentiated endometrial carcinoma (DEC)–an uncommon and highly aggressive uterine malignancy–is beset by high failure rates. A line of research that holds promise to overcome these limitations is tailored treatments targeted on specific molecular alterations. However, suitable preclinical platforms to allow a reliable implementation of this approach are still lacking. Here, we developed a patient-derived xenograft (PDX) model for preclinical testing of investigational drugs informed by molecular data. The model–termed PDX-mLung was established in mice implanted with lung metastatic lesions obtained from a patient with DEC. Histologic and whole-exome genetic analyses revealed a high degree of identity between PDX-mLung and the patient’s parental lesions (both primary DEC and lung metastases). Interestingly, molecular analyses revealed that PDX-mLung harbored druggable alterations including a FGFR2 mutation and CCNE2 amplification. Targeted combined treatment with the FGFR inhibitor lenvatinib and the cell cycle inhibitor palbociclib was found to exert synergistic therapeutic effects against in vivo tumor growth. Based on the results of RNA sequencing, lenvatinib and palbociclib were found to exert anti-tumor effects by interfering interferon signaling and activating hormonal pathways, respectively. Collectively, these data provide proof-of-concept evidence on the value of PDX models for preclinical testing of molecularly informed drug therapy in difficult-to-treat human malignancies. Further clinical research is needed to examine more rigorously the potential usefulness of the lenvatinib and palbociclib combination in patients with DEC.

Histologic and genomic features of breast cancers with alterations affecting the SWI/SNF (SMARC) genes

The SWI/SNF family of proteins is a multisubunit ATPase complex frequently altered in human cancer. Inactivating mutations in SWI/SNF-related matrix-associated actin-dependent regulator of chromatin (SMARCs) underpin a subset of tumors such as the malignant rhabdoid tumor and small cell carcinoma of the ovary, hypercalcemic type. Here, we investigated the genotypic and phenotypic characteristics of breast cancers harboring somatic genetic alterations affecting genes of the SMARC family. We analyzed a series of 6026 primary and metastatic breast cancers subjected to targeted-capture sequencing. SMARC core subunit (SMARCA4, SMARCB1, and SMARCA2) alterations were identified in <1% of all breast cancers, consisting of 27 primary and 30 recurrent/metastatic tumors. The majority of SMARC alterations were monoallelic mutations (47/57, 82%) and thus categorized into two groups: Class 1 alterations consisting of potentially pathogenic mutations and rearrangements and Class 2 alterations consisting of missense mutations and small in-frame deletions of unknown significance. Biallelic events in a SMARC gene were present in a minority of cases (10/57, 18%). Histologic patterns in the form of rhabdoid, composite rhabdoid, sarcomatoid or anaplastic features were observed in a subset of Class 1 primary and metastatic tumors (7/57, 12%). SMARC protein was preserved in nearly all tumors analyzed with immunohistochemistry (26/30, 87%). Four Class 1 tumors demonstrated altered SMARC protein expression in the form of loss (1/30, 3%) or mosaic pattern (3/30, 10%). Complete loss of SMARCA2 (BRM) was observed in a sole tumor with composite rhabdoid morphology, and biallelic hits in the SMARCA2 gene. The genomic landscape of both primary Class 1 and 2 breast cancers did not reveal any characteristic findings. In summary, SMARC alterations likely contribute to the biology of a rare subset of breast cancers in the form of biallelic or pathogenic alterations in SMARC, as evidenced by SMARC-deficient phenotype or altered expression of SMARC protein.

Cytomorphologic Spectrum of SMARCB1-Deficient Soft Tissue Neoplasms

OBJECTIVES

The SWI/SNF complex core subunit SMARCB1 is inactivated in a variety of neoplasms that share characteristic "rhabdoid" cytomorphology. The aim of this study was to evaluate SMARCB1-deficient soft tissue neoplasms on cytology to identify diagnostic clues.

METHODS

Eleven SMARCB1-deficient tumors, including six epithelioid sarcomas, three malignant rhabdoid tumors, one epithelioid malignant peripheral nerve sheath tumor (MPNST), and one poorly differentiated chordoma with fine-needle aspiration (FNA), serous effusion, or touch prep (TP) from two institutions, were included. Targeted next-generation sequencing (NGS) was performed in two cases.

RESULTS

Evaluation of FNA (n = 4), effusion (n = 4), and TP (n = 3) in nine adult and two pediatric patients demonstrated cellular samples (n = 11), epithelioid cells with rhabdoid morphology (n = 9), eccentrically located nuclei with prominent nucleoli (n = 7), and cytoplasmic bodies (n = 4); two patients were diagnosed on FNA with cell block. Immunohistochemistry (IHC) demonstrated SMARCB1 loss in all cases and keratin and/or EMA expression in all but the epithelioid MPNST; NGS identified SMARCB1 inactivation in both cases.

CONCLUSIONS

SMARCB1-deficient soft tissue neoplasms comprise a variety of tumors with epithelioid morphology and frequent expression of keratin and/or EMA. Recognition of characteristic rhabdoid morphology on cytology can prompt IHC and/or NGS testing for SMARCB1 deficiency and help establish the diagnosis.

SMARCB1/INI1-deficient tumors of adulthood

The SMARCB1/INI1 gene was first discovered in the mid-1990s, and since then it has been revealed that loss of function mutations in this gene result in aggressive rhabdoid tumors. Recently, the term "rhabdoid tumor" has become synonymous with decreased SMARCB1/INI1 expression. When genetic aberrations in the SMARCB1/INI1 gene occur, the result can cause complete loss of expression, decreased expression, and mosaic expression. Although SMARCB1/INI1-deficient tumors are predominantly sarcomas, this is a diverse group of tumors with mixed phenotypes, which can often make the diagnosis challenging. Prognosis for these aggressive tumors is often poor. Moreover, refractory and relapsing progressive disease is common. As a result, accurate and timely diagnosis is imperative. Despite the SMARCB1/INI1 gene itself and its implications in tumorigenesis being discovered over two decades ago, there is a paucity of rhabdoid tumor cases reported in the literature that detail SMARCB1/INI1 expression. Much work remains if we hope to provide additional therapeutic strategies for patients with aggressive SMARCB1/INI1-deficient tumors.

Sarcomatoid hepatocellular carcinoma is distinct from ordinary hepatocellular carcinoma: Clinicopathologic, transcriptomic and immunologic analyses

Sarcomatoid hepatocellular carcinoma (SHCC), which was a rare histological subtype of hepatocellular carcinoma (HCC), is currently subclassified as poorly differentiated HCC because of insufficient evidence to define SHCC as a subtype of HCC. We aimed to assess the feasibility of classifying SHCC as a histological subtype of HCC by comprehensively identifying novel and distinct characteristics of SHCC compared to ordinary HCC (OHCC). Fifteen SHCCs (1.4%) defined as HCC with at least a 10% sarcomatous component, 15 randomly disease-stage-matched OHCCs and 163 consecutive OHCCs were extracted from 1106 HCCs in the Pathology Database (1997-2019) of our hospital. SHCC patients showed poor prognosis, and the tumors could be histologically subclassified into the pleomorphic, spindle and giant cell types according to the subtype of carcinomas with sarcomatoid or undifferentiated morphology in other organs. The transcriptomic analysis revealed distinct characteristics of SHCC featuring the upregulation of genes associated with epithelial-to-mesenchymal transition and inflammatory responses. The fluorescent multiplex immunohistochemistry results revealed prominent programmed death-ligand 1 (PD-L1) expression on sarcomatoid tumor cells and higher infiltration of CD4⁺ and CD8⁺ T cells in SHCCs compared to OHCCs. The density of CD8⁺ T cells in the nonsarcomatous component of SHCCs was also higher than that in OHCCs. In conclusion, the comprehensive analyses in our study demonstrated that SHCC is distinct from OHCC in terms of clinicopathologic, transcriptomic and immunologic characteristics. Therefore, it is reasonable to consider SHCC as a histological subtype of HCC.

SWI/SNF-deficient head and neck neoplasms: An overview

With wide-spread use of next generation sequencing tools in surgical pathology, a variety of neoplasms have been increasingly recognized to be associated with specific recurrent defining genetic abnormalities. This has led to recognition of new genetically defined entities and refinements of preexisting heterogeneous neoplastic categories. Among these, neoplasms associated with inactivating mutations involving different subunits of the SWI/SNF chromatin remodeling complex have received special attention. In the head and neck area, SMARCB1 (INI1) and SMARCA4 (BRG1) are the main two SWI/SNF components responsible for several recently described highly aggressive undifferentiated malignancies with predilection for the soft tissue of the neck (SMARCB1-deficient malignant rhabdoid tumors in children and rare epithelioid sarcoma cases in adults) and the sinonasal tract (SMARCB1-deficient sinonasal carcinoma including a small subset of adenocarcinomas, SMARCA4-deficient sinonasal undifferentiated carcinoma and SMARCA4-deficient sinonasal teratocarcinosarcoma). Molecular studies confirmed paucity of additional genetic abnormalities in these diseases underlining the central role of SWI/SNF deficiency as the primary and frequently sole genetic driver of these lethal diseases. Initiation of clinical trials using drugs that target the SWI/SNF collapse encourages recognition and correct classification of these morphologically frequently overlapping malignancies and underpins the role of SWI/SNF immunohistochemistry as emerging powerful adjunct tool in surgical pathology of the head and neck.

SMARCA4/BRG1-Deficient Non-Small Cell Lung Carcinomas: A Case Series and Review of the Literature

CONTEXT.—

Somatic mutations in SMARCA4 (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 4) gene and/or BRG1 (Brahma-related gene 1) loss identifies a subset of non-small cell lung carcinomas (NSCLCs) lacking alterations in EGFR (epidermal growth factor receptor), ALK (anaplastic lymphoma kinase), and ROS1 (ROS proto-oncogene 1) genes. Preliminary observations suggest responsiveness to immunotherapy and targeted therapies.

OBJECTIVE.—

To study BRG1 loss in NSCLCs and elucidate the clinicopathologic profile of such SMARCA4-deficient NSCLCs.

DESIGN.—

Non-small cell lung carcinomas diagnosed during 6 years were subject to immunohistochemistry for BRG1 and BRM (Brahma). Tumors with BRG1 loss were stained with antibodies against thyroid transcription factor 1 (TTF-1), p40, cytokeratins, hepatocyte paraffin 1 (Hep Par 1), Sal-like protein 4 (SALL4), CD34, SRY-box 2 (SOX2), chromogranin, synaptophysin, p53, integrase interactor 1, ALK, and ROS1. EGFR mutation testing was performed by polymerase chain reaction-based method.

RESULTS.—

Among 100 NSCLCs tested, 4 cases (4%) showed BRG1 loss. The histology ranged from solid adenocarcinomas (n = 1) to large cell/poorly differentiated carcinomas (n = 3) with clear cell cytology in 2 cases. All showed loss/reduction of BRM with variable cytokeratin and SALL4 expression, and were negative for TTF-1, p40, Hep Par 1, ALK, ROS1, and EGFR mutations. CD34 and SOX2 were negative in all 4 cases. Isolated BRM loss was common (21%), distributed across all NSCLC subtypes including squamous cell carcinomas and a hepatoid adenocarcinoma.

CONCLUSIONS.—

BRG1 loss occurs in a subset of TTF-1/p40-negative poorly differentiated NSCLCs. Identification and follow-up will clarify the prognosis, diagnostic criteria, and potential for therapeutic personalization.

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

OBJECTIVE

The 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.

METHODS

For 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.

RESULTS

The 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.

CONCLUSIONS

COV434 represents a bona fide SCCOHT cell line. TOV-112D is a dedifferentiated ovarian carcinoma cell line.

SWI/SNF-deficient thoraco-pulmonary neoplasms

The SWI/SNF complexes are major regulators of gene expression and their alterations occur in a large array of cancers both of epithelial and mesenchymal lineages. Malignant rhabdoid tumors were the first malignancies linked to deregulation of these complexes with the involvement of SMARCB1 in their development but genetic alterations affect all subunits in other malignancies. In the chest and lung regions, SMARCA4 (BRG1) is the most frequently altered subunit and is involved in the pathogenesis of two subtypes of tumors, including bona fide carcinomas (SMARCA4-deficient non-small cell lung cancers) but also undifferentiated tumors that harbor an undifferentiated phenotype close to those of malignant rhabdoid tumors (SMARCA4-undifferentiated tumors). Although their histogenesis is yet to be fully understood, these tumors are associated with distinct clinical and pathological features even though some overlapping features have been reported in rare cases. SMARCA4 deficiency is easily asserted by immunohistochemistry that show the loss of nuclear expression of the protein in the nuclei of tumor cells. These tumors are commonly associated with high-grade cytological features, rhabdoid cytomorphology, solid architecture and extensive necrosis. The typical immunohistochemical signature of SMARCA4-UT combines co-inactivation of SMARCA2 (BRM) and the overexpression of SOX2 and SALL4. No specific therapeutic strategies have been so far developed for SMARCA4-deficient neoplasms. SMARCB1 subunit is involved in the development of several SMARCB1-deficient sarcomas on top of malignant rhabdoid tumors that may develop in the thorax. Malignant rhabdoid tumors affect mostly children of less than 5y. The differential diagnosis includes epithelioid sarcomas, malignant myoepithelial tumors or myoepithelial carcinomas, extra-skeletal myxoid chondrosarcomas and synovial sarcomas.

BRG1, INI1, and ARID1B Deficiency in Endometrial Carcinoma: A Clinicopathologic and Immunohistochemical Analysis of a Large Series From a Single Institution

Switch/sucrose nonfermenting complex subunits, such as BRG1, INI1, and ARID1B, are inactivated in a subset of endometrial undifferentiated carcinoma and dedifferentiated carcinoma (DC). Limited information is currently available on their prevalence in other subtypes or the nosological status of endometrial carcinoma with their deficiencies. This study immunohistochemically examined the expression status of BRG1, INI1, and ARID1B using 570 archived cases of endometrial carcinoma and carcinosarcoma resected at a single institution. We identified 1 BRG1-deficient undifferentiated carcinoma, 8 BRG1/INI1/ARID1B-deficient DC, and 3 BRG1-deficient clear-cell carcinomas. None of the cases of endometrioid and serous carcinomas or carcinosarcoma showed deficiencies of these subunits. We then compared 8 BRG1/INI1/ARID1B-deficient DC with 6 BRG1/INI1/ARID1B-intact DC and 28 carcinosarcomas, the latter of which was often confused with DC. Histologically, BRG1/INI1/ARID1B-intact and BRG1/INI1/ARID1B-deficient DC shared a monotonous solid appearance with rhabdoid and epithelioid cells and a myxoid stroma; however, abrupt keratinization and cell spindling was absent in BRG1/INI1/ARID1B-deficient tumors. The median overall survival of patients with BRG1/INI1/ARID1B-deficient DC was 3.8 months, which was worse than those with BRG1/INI1/ARID1B-intact DC (P=0.008) and with carcinosarcoma (P=0.004). BRG1/INI1/ARID1B-deficient DC may be a separate entity with an aggressive behavior to be distinguished from BRG1/INI1/ARID1B-intact DC and carcinosarcoma. Regarding clear-cell carcinoma (n=12), BRG1 deficiency appeared to be mutually exclusive with abnormal ARID1A, BRM, and p53 expression. Further studies are needed to clarify whether BRG1 deficiency plays a role in the pathogenesis of clear-cell carcinoma.

SMARCA4 (BRG1) and SMARCB1 (INI1) expression in TTF-1 negative neuroendocrine carcinomas including merkel cell carcinoma

SMARCA4 and SMARCB1 loss of function has been implicated in many different tumors. The objective of this study was to investigate the loss of BRG1 and INI1 expression in TTF-1 negative neuroendocrine carcinomas to see if they are analogous to small-cell carcinoma of the ovary, hypercalcemic type. The potential role of these tumor suppressor genes in high-grade neuroendocrine carcinoma largely remains unknown. Cases of previously diagnosed Small cell carcinoma (SmCC), Large cell neuroendocrine carcinoma (LCNEC) and Merkel cell carcinoma (MCC) were selected. Immunohistochemical expression patterns for BRG1 and INI1 were interpreted as: intact, hybrid and complete loss of nuclear staining. SmCC and LCNEC cases were divided as TTF-1 positive and TTF-1 negative subsets. One case of TTF-1 negative SmCC (lung) showed loss of SMARCA4(BRG1) expression. Amongst TTF-1 negative LCNEC, one case (lung) showed complete loss of SMARCA4(BRG1) and partial loss of SMARCB1(INI1) and one case (lymph node) had hybrid expression of SMARCA4(BRG1) with intact SMARCB1(INI1) expression. All TTF-1 positive cases and all MCC cases showed intact expression of SMARCA4(BRG1) and SMARCB1(INI1). Our study highlights that SMARCA4(BRG1) is deficient in a subset of NEC. Inactivation of SMARCA4 in a subset of TTF-1 negative neuroendocrine carcinomas especially of pulmonary site can be further studied for their therapeutic response to targeted therapy e.g. EZH2 inhibitors. In addition, our study is the first to show that BRG1 and INI1 expression are intact in MCC and hence the biology of MCC might be completely exclusive of these two tumor suppressor genes.

Recurrent Loss of SMARCA4 in Sinonasal Teratocarcinosarcoma

Molecular analysis has reshaped the landscape of high grade sinonasal tumors by defining novel entities and identifying recurrent mutations in established tumor types. However, sinonasal teratocarcinosarcoma (TCS), a rare and aggressive tumor with intermixed teratomatous, carcinomatous, and sarcomatous elements, remains poorly understood. The multiphenotypic differentiation of TCS has engendered persistent controversy about its histogenesis and leads to diagnostic overlap with several other malignancies. In this study, we evaluated the molecular underpinnings of TCS to clarify its pathogenesis and diagnosis. We performed SMARCA4 immunohistochemistry (IHC) on 22 TCS and 153 other sinonasal tumors. We identified loss of SMARCA4 expression in 18 TCS (82%), including 15 (68%) with complete loss and 3 (14%) with partial loss. Although we also identified partial SMARCA4 loss in 1 of 8 SMARCB1-deficient sinonasal carcinomas (13%), SMARCA4 was intact in all other sinonasal carcinomas and neuroendocrine tumors. We then selected 3 TCS with complete SMARCA4 loss by IHC for a targeted next-generation sequencing panel that included 1425 cancer-related genes. We confirmed biallelic somatic inactivation of SMARCA4 without other known oncogenic mutations in these 3 cases. Overall, these findings suggest that SMARCA4 inactivation may be the dominant genetic event in TCS, expanding understanding of this gene's role in sinonasal tumorigenesis. They also raise the possibility that TCS is on a diagnostic spectrum with the newly described SMARCA4-deficient sinonasal carcinoma, blurring the lines between established and emerging sinonasal entities. In addition, SMARCA4 IHC may provide a useful adjunct for confirming a diagnosis of TCS in limited material.

Undifferentiated and dedifferentiated neoplasms of the female genital tract

Undifferentiated neoplasms in the female gynecologic tract comprise two main groups-undifferentiated carcinoma, most common in the endometrium and ovary, and undifferentiated uterine sarcoma, although tumors with an undifferentiated appearance may occur in all gynecologic organs. Their differential diagnosis is broad and generous sampling, careful morphological evaluation, judicious use of immunohistochemistry, and in many cases, molecular testing is often essential in the diagnostic work-up. As some of these neoplasms fail to respond to conventional chemotherapy regimens and/or radiation therapy, targeted therapy may be valuable in treating these highly aggressive tumors, thus the importance of precise diagnosis. In this review we discuss the clinicopathological features of undifferentiated carcinoma, dedifferentiated carcinoma, and undifferentiated uterine sarcoma, followed by a comprehensive analysis of morphological mimickers. Finally, we briefly review ovarian and lower genital tract tumors with an undifferentiated histological appearance.

SWI/SNF-deficiency defines highly aggressive undifferentiated endometrial carcinoma

Dedifferentiated/undifferentiated endometrial carcinoma (DDEC/UEC) is an endometrial cancer characterized by the presence of histologically undifferentiated carcinoma. Genomic inactivation of core switch/sucrose nonfermentable (SWI/SNF) complex proteins was recently identified in approximately two-thirds of DDEC/UEC. The aim of this study was to delineate the clinical behavior of SWI/SNF-deficient DDEC/UEC in comparison to SWI/SNF-intact DDEC/UEC. The study cohort consisted of 56 SWI/SNF-deficient DDEC/UEC (2 POLE-mutated), which showed either SMARCA4 (BRG1) loss, ARID1A/1B co-loss, or SMARCB1 (INI1) loss in the undifferentiated tumor, and 26 SWI/SNF-intact DDEC/UEC (4 POLE-mutated). The average age at diagnosis was 61 years for patients with SWI/SNF-deficient tumors and 64 years for SWI/SNF-intact tumors. Mismatch repair (MMR) protein deficiency was seen in 66% of SWI/SNF-deficient and 50% of SWI/SNF-intact tumors. At initial presentation, 55% of patients with SWI/SNF-deficient tumors had extrauterine disease spread in contrast to 38% of patients with SWI/SNF-intact tumors. The 2-year disease specific survival (DSS) for stages I and II disease was 65% for SWI/SNF deficient tumors relative to 100% for SWI/SNF-intact tumors (p = 0.042). For patients with stages III and IV disease, the median survival was 4 months for SWI/SNF-deficient tumors compared to 36 months for SWI/SNF-intact tumors (p = 0.0003). All six patients with POLE-mutated tumors, including one with stage IV SWI/SNF-deficient tumor were alive with no evidence of disease. Among the patients with advanced stage SWI/SNF-deficient tumors, 68% (21 of 31) received adjuvant or neoadjuvant chemotherapy (platinum/taxane-based) and all except the patient with a POLE-mutated tumor (20 of 21) experienced disease progression either during chemotherapy or within 4 months after its completion. These findings show that core SWI/SNF-deficiency defines a highly aggressive group of undifferentiated cancer characterized by rapid disease progression that is refractory to conventional platinum/taxane-based chemotherapy. This underscores the importance of accurate clinical recognition of this aggressive tumor and the need to consider alternative systemic therapy for these tumors.

Establishment and characterization of VOA1066 cells: An undifferentiated endometrial carcinoma cell line

Dedifferentiated endometrial carcinoma (DDEC) is a rare but highly aggressive type of endometrial cancer, in which an undifferentiated carcinoma arises from a low-grade endometrioid endometrial carcinoma. The low-grade component is often eclipsed, likely due to an outgrowth of the undifferentiated component, and the tumor may appear as a pure undifferentiated endometrial carcinoma (UEC). We and others have recently identified inactivating mutations of SMARCA4, SMARCB1 or ARID1B, subunits of the SWI/SNF chromatin-remodeling complex, that are unique to the undifferentiated component and are present in a large portion of DDEC and UEC. However, the understanding of whether and how these mutations drive cancer progression and histologic dedifferentiation is hindered by lack of cell line models of DDEC or UEC. Here, we established the first UEC cell line, VOA1066, which is highly tumorigenic in vivo. This cell line has a stable genome with very few somatic mutations, which do include inactivating mutations of ARID1A and ARID1B (2 mutations each), and a heterozygous hotspot DICER1 mutation in its RNase IIIb domain. Immunohistochemistry staining confirmed the loss of ARID1B, but ARID1A staining was retained due to the presence of a truncating non-functional ARID1A protein. The heterozygous DICER1 hotspot mutation has little effect on microRNA biogenesis. No additional DICER1 hotspot mutations have been identified in a cohort of 33 primary tumors. Therefore, we have established the first UEC cell line with dual inactivation of both ARID1A and ARID1B as the main genomic feature. This cell line will be useful for studying the roles of ARID1A and ARID1B mutations in the development of UEC.

Undifferentiated endometrial carcinoma arising in the background of high-grade endometrial carcinoma - Expanding the definition of dedifferentiated endometrial carcinoma

Dedifferentiated endometrial adenocarcinoma (DEC) is defined by the coexistence of undifferentiated carcinoma with low-grade (FIGO grade 1 or 2) endometrioid carcinoma. Few cases of DEC arising in the background of high-grade carcinoma (DEC-HG) have been reported, however, this phenomenon is poorly characterized. In this study we describe the morphologic, immunohistochemical and clinico-pathologic characteristics of DEC-HG. 18 DECs were diagnosed at our institution between 2008-2019, and in 11 (61%), the undifferentiated component was associated with high-grade carcinoma (8 endometrioid FIGO grade 3, 2 with ambiguous features, 1 serous). The remaining 7 (39%) represented DEC-LG (3 FIGO grade 1 and 4 FIGO grade 2). 7/11 (64%) patients with DEC-HG presented with advanced stage (FIGO stage III/IV), whereas most with DEC-LG (6/7, 86%) were stage I. On follow up, 2 patients in the DEC-HG group died of disease and 2 had progressive disease within 2 months of surgery. There was only one recurrence in the DEC-LG, 6 months post-surgery. The DEC component in both groups showed similar morphology and immunophenotype, with predominantly focal or complete loss of expression of pan-keratin, EMA, E-cadherin, CK8/18, PAX8 and ER. The DEC component in the DEC-HG group had wild-type p53 expression in 8/11 (73%) cases, loss of MLH1 and PMS2 in 6/11 (55%) and loss of SMARCA4 in 3/9 (33%). Although numbers are small, we show that DEC-HG is a previously under-recognized phenomenon, with morphologic and immunophenotypic similarities to DEC-LG, which supports expanding the definition of DEC to include DEC-HG. DEC-HG may be more aggressive than DEC-LG.

SWI/SNF-deficient malignancies of the female genital tract

Mutations and other molecular events involving subunits of the SWI/SNF chromatin remodelling complex are common in a wide variety of malignancies, including those arising at various sites in the female genital tract. Endometrioid and clear cell carcinomas in the uterine corpus and ovary not uncommonly contain mutations in ARID1A and these also occur in other endometriosis-associated ovarian neoplasms such as seromucinous tumours. In these organs, mutations in SMARCA4, SMARCB1, ARID1A and ARID1B (with subsequent loss of corresponding protein expression as a reliable surrogate) are relatively common in undifferentiated carcinomas, including the undifferentiated component of dedifferentiated carcinoma. SMARCA4 mutations are extremely common (almost ubiquitous) in small cell carcinoma of the ovary of hypercalcaemic type (SCCOHT), occurring in about 98% of these neoplasms, often in association with epigenetic SMARCA2 loss. SMARCB1-deficient vulval neoplasms include epithelioid sarcoma and myoepithelial carcinoma, as well as related malignancies which defy easy classification. Recently the spectrum of SWI/SNF deficient female genital malignancies has been expanded to include SMARCA4-deficient undifferentiated uterine sarcoma and mural nodules of anaplastic carcinoma in ovarian mucinous neoplasms.

Review of SMARCA4 (BRG1)-deficient carcinomas following a malignant pleural effusion specimen confounded by reduced claudin-4 expression

SMARCA4-deficient neoplasms are recently characterized high-grade malignancies associated with a poor prognosis. The SMARCA4 gene encodes BRG1, which is part of the SWI/SNF complex. SMARCA4-deficient neoplasms have an undifferentiated, often rhabdoid morphology, and demonstrate loss of BRG1 nuclear expression on immunohistochemistry. These neoplasms have become increasingly recognized and diagnosed in tissue specimens, but their features in cytologic specimens are poorly defined in the literature. The review is introduced by a diagnostically challenging case of a SMARCA4-deficient carcinoma involving a pleural fluid specimen in which the carcinoma cells demonstrated greatly reduced claudin-4 expression in the setting of strong, diffuse BerEP4 expression. Most of the malignant cells also demonstrated positive cytoplasmic staining for PAS and all were PAS-diastase negative, suggesting that the cytoplasm contained glycogen granules.

SMARCB1-deficient carcinomas of the head and neck region: a cytopathologic characterization

INTRODUCTION

SMARCB1 encodes for a component of the SWI/SNF complex and is widely implicated in carcinogenesis. In the head and neck, SMARCB1-deficient carcinomas typically arise in the sinonasal tract but can be found at other sites. EZH2 inhibitors have emerged as potential targeted therapy against SWI/SNF-deficient tumors. We sought to characterize the cytomorphology of head and neck carcinomas with SMARCB1 deficiencies to identify potential candidates for targeted therapy.

MATERIALS AND METHODS

Head and neck carcinomas with SMARCB1 mutations were retrospectively identified and confirmed to be SMARCB1-deficient by both molecular (fluorescent in-situ hybridization or next generation sequencing) and immunohistochemical means. Cases with positive cytology were reviewed and their cytologic features cataloged.

RESULTS

A total of 19 specimens from 13 patients were reviewed, including 8 specimens from 7 sinonasal carcinomas, 4 specimens from 3 thyroid carcinomas, 3 specimens from 2 skin carcinomas, and 4 specimens from 1 carcinoma of unknown primary origin. High-grade features were common, including mitoses (11 of 19) necrosis (13 of 19) and multinucleation (16 of 19). Tumors showed either dense cytoplasm with distinct cell borders (10 of 19) or delicate cytoplasm with indistinct cell borders (9 of 19). Most tumors showed no distinct epithelial differentiation (12 of 19), while some (7 of 19) showed glandular or signet ring features. A minor cohort demonstrated rhabdoid cells (4 of 19).

CONCLUSIONS

Head and neck carcinomas with SMARCB1 deficiencies have a wide array of morphologies and tend to demonstrate high-grade features. Only a minor cohort demonstrate rhabdoid-type cells. Evaluation of SMARCB1 deficiency for potential targeted therapy should not be limited to tumors with rhabdoid morphology.

Loss of switch/sucrose non-fermenting complex protein expression in undifferentiated gastrointestinal and pancreatic carcinomas

AIMS

Undifferentiated carcinoma refers to an epithelial malignancy that lacks morphological evidence of differentiation. Recent studies have implicated the loss of constitutively expressed switch/sucrose non-fermenting (SWI/SNF) complex subunits in undifferentiated carcinomas of the gastrointestinal tract and other sites. In this study we examine the expression of SWI/SNF and mismatch repair (MMR) proteins in a series of undifferentiated carcinomas from the gastrointestinal tract and the pancreas.

METHODS AND RESULTS

We searched pathology databases from four Canadian health centres for primary undifferentiated carcinoma from gastrointestinal and pancreatic resection specimens. Upon review of 31 cases, 19 were confirmed to be undifferentiated carcinomas (eight colonic, six gastric, three pancreatic, one appendiceal and one duodenal). Immunohistochemical analysis of SMARCA4, SMARCA2, SMARCB1, ARID1A, ARID1B, MSH2, MSH6, MLH1 and PMS2 was performed on whole sections. Five of 19 (26%) showed loss of core SWI/SNF proteins (two loss of SMARCA4, one loss of SMARCB1 and two concurrent loss of ARID1A and ARID1B). SMARCA4, SMARCB1, or ARID1A/ARID1B-deficient undifferentiated carcinoma consistently exhibited sheet-like growth pattern, with cellular discohesion and rhabdoid morphology. Nine of 17 undifferentiated carcinomas tested were MMR-deficient by immunohistochemistry. In comparison, none of the 12 poorly differentiated carcinomas that were originally diagnosed as undifferentiated carcinomas showed loss of SMARCA4, SMARCA2, SMARCB1 or ARID1B.

CONCLUSIONS

Undifferentiated gastrointestinal/pancreatic carcinomas show frequent loss of expression of SWI/SNF complex proteins. The loss of these core components of SWI/SNF complex may contribute to the arrest of cellular differentiation, resulting in the undifferentiated histology and aggressive clinical behaviour.

SWI/SNF complex-deficient soft tissue neoplasms: An update

The SWItch Sucrose Non-Fermentable (SWI/SNF) chromatin remodeling complex is a large multi-subunit protein assembly that orchestrates chromatin compaction and accessibility for gene transcription in an ATP-dependent manner. As a key epigenetic regulator, the SWI/SNF complex coordinates gene expression, cell proliferation and differentiation, and its biologic functions, in part, antagonize the polycomb repressive complex 2. The mammalian SWI/SNF complex consists of 15 subunits encoded by 29 genes, some of which are recurrently mutated in human cancers, in the germline or sporadic setting. Most SWI/SNF-deficient tumors share common "rhabdoid" cytomorphology. SMARCB1 (INI1) is the subunit most frequently inactivated in soft tissue neoplasms. Specifically, SMARCB1 deficiency is observed as the genetic hallmark in virtually all malignant rhabdoid tumors, and most cases of epithelioid sarcoma and poorly differentiated chordoma. In addition, subsets of myoepithelial carcinoma (10-40%), extraskeletal myxoid chondrosarcoma (20%), epithelioid schwannoma (40%), and epithelioid malignant peripheral nerve sheath tumor (70%) demonstrate SMARCB1 loss. The gene encoding the SS18 subunit is involved in the SS18-SSX rearrangement, which is pathognomonic of synovial sarcoma and indirectly inactivates SMARCB1. Finally, undifferentiated SMARCA4-deficient thoracic sarcomas are defined by SMARCA4 subunit inactivation, leading to SMARCA4 and SMARCA2 loss. Rarely, inactivation of alternate but biologically equivalent key regulators can substitute for canonical subunit deficiency, such as SMARCA4 inactivation in cases of SMARCB1-retained epithelioid sarcoma. This review briefly highlights SWI/SNF complex biologic functions and its roles in human cancer and provides a detailed update on recent advances in soft tissue neoplasms with canonical SWI/SNF complex deficiency, correlating morphologic, genomic, and immunohistochemical findings.

SWI/SNF Complex Mutations in Gynecologic Cancers: Molecular Mechanisms and Models

The SWI/SNF (mating type SWItch/Sucrose NonFermentable) chromatin remodeling complexes interact with histones and transcription factors to modulate chromatin structure and control gene expression. These evolutionarily conserved multisubunit protein complexes are involved in regulating many biological functions, such as differentiation and cell proliferation. Genomic studies have revealed frequent mutations of genes encoding multiple subunits of the SWI/SNF complexes in a wide spectrum of cancer types, including gynecologic cancers. These SWI/SNF mutations occur at different stages of tumor development and are restricted to unique histologic types of gynecologic cancers. Thus, SWI/SNF mutations have to function in the appropriate tissue and cell context to promote gynecologic cancer initiation and progression. In this review, we summarize the current knowledge of SWI/SNF mutations in the development of gynecologic cancers to provide insights into both molecular pathogenesis and possible treatment implications for these diseases.

The SWI/SNF chromatin-remodeling complex status in renal cell carcinomas with sarcomatoid or rhabdoid features

The presence of sarcomatoid or rhabdoid features (which are associated with advanced disease and poor prognosis) is rarely observed in the subtypes of renal cell carcinoma (RCC). The SWI/SNF chromatin-remodeling complex, which is composed of evolutionarily conserved core subunits including SMARCB1/INI1 (SMARCB1), SMARCA4/BRG1 (SMARCA4), SMARCC1/BAF155 (SMARCC1), and SMARCC2/BAF170 (SMARCC2), can be regarded as the prototype of an epigenetic regulator of gene expression that is involved in tumor suppression. We analyzed the histological, immunohistochemical, and clinicopathological status in 72 cases of RCC with sarcomatoid or rhabdoid features, focusing on the expression status of the subunits of SWI/SNF chromatin-remodeling complex proteins. Cases with lost or reduced expression were defined as showing aberrant expression. The frequency of aberrant SMARCA4 immunoexpression of a sarcomatoid or rhabdoid component in clear cell RCC (ccRCC) (47/50, 94%) was significantly higher than that in non-ccRCC (4/9, 44%) (p < 0.001). In ccRCC without sarcomatoid or rhabdoid features, aberrant SMARCA4 immunoexpression was observed in 33 of 48 (67%) cases. Immunoreactivities for SMARCB1, SMARCA2, and SMARCC2 were retained in almost all subtypes of RCC. The patients with aberrant SMARCA4 expression in RCC with sarcomatoid or rhabdoid features achieved shorter progression-free survival compared with the patients with retained SMARCA4 expression (all subtypes of RCC, p = 0.0212; ccRCC, p = 0.0265). These results suggest that in ccRCC, aberrant SMARCA4 expression is one of the adverse prognostic factors or a high-grade malignant transforming factor. The evaluation of SMARCA4 immunoexpression may be a useful diagnostic tool to help distinguish ccRCC from non-ccRCC.

SMARCA family of genes

The SMARCA subgroup of genes belong to the SWI1/SNF1 family that are responsible chromatin remodelling and repair. Inactivating mutations in the main SMARCA genes A2 and A4 lead to loss of expression of their respective proteins within the nucleus and, as such have characterised a set of malignancies that are underpinned by SMARCA-deficiency.The morphology of these tumours ranges from small to large epithelioid cells, giant cells and rhabdoid cells. The rhabdoid cells are frequently present in these tumours but are not a sine qua non for the diagnosis. Most of these tumours are undifferentiated or dedifferentiated, high-grade pleomorphic carcinomas. Focally, areas of better differentiation can be seen. The initial description of a SMARCA4-deficient malignancy was the small cell carcinoma of the ovary, hypercalcaemic type. Subsequently, tumours fitting this characteristic morphology and immunophenotype have been described in the lung, thoracic cavity, endometrium and sinonasal tract, gastrointestinal tract and kidney. Immunohistochemical loss of SMARCA2 and SMARCA4 may occur concomitantly or independently of each other.SMARCA-deficient malignant tumours represent a unique subset of tumours with typical morphological and immunohistochemical findings.

A Comprehensive Review of Biomarker Use in the Gynecologic Tract Including Differential Diagnoses and Diagnostic Pitfalls

Morphologic (ie, hematoxylin and eosin) evaluation of the Mullerian tract remains the gold standard for diagnostic evaluation; nevertheless, ancillary/biomarker studies are increasingly utilized in daily practice to assist in the subclassification of gynecologic lesions and tumors. The most frequently utilized "biomarker" technique is immunohistochemistry; however, in situ hybridization (chromogenic and fluorescence), chromosomal evaluation, and molecular analysis can also be utilized to aid in diagnosis. This review focuses on the use of immunohistochemistry in the Mullerian tract, and discusses common antibody panels, sensitivity and specificity of specific antibodies, and points out potential diagnostic pitfalls when using such antibodies.

[Un- and dedifferentiated endometrial carcinoma : A rare entity with a wide range of differential diagnosis]

Dedifferentiated endometrial carcinomas (ECs) are composed of undifferentiated EC and a FIGO grade 1 or 2 endometrioid carcinoma. The undifferentiated component represents a malignant epithelial neoplasm with no obvious differentiation and immunohistochemical loss of PAX8, E‑cadherin and focal expression of EMA and/or CK18 and the predominant presence of nuclear staining for INI1 (SMARCB1) and BRG1 (SMARCA4). The main differential diagnoses include poorly differentiated endometrioid EC, neuroendocrine carcinoma, lymphoma, plasmocytoma, high-grade endometrial stromal sarcomas, undifferentiated uterine sarcomas (UUS), carcinosarcomas, and metastases to the endometrium. The histogenesis is not yet fully understood and molecular data are still limited. Some tumors represent a loss of MHL1 and PMS2 staining due to MLH1-promotor methylation. Rare cases are associated with Lynch syndrome or POLE mutation. The un- or dedifferentiated EC represents a high-grade endometrial carcinoma that requires extended surgery and indicates a poor prognosis. In cases with mismatch repair protein deficiency or POLE mutation, immuno-oncological treatment with checkpoint inhibitors are a therapeutic option.

Dedifferentiated Endometrial Carcinoma Could be A Target for Immune Checkpoint Inhibitors (Anti PD-1/PD-L1 Antibodies)

Dedifferentiated endometrial carcinoma (DDEC) is defined as an undifferentiated carcinoma admixed with differentiated endometrioid carcinoma (Grade 1 or 2). It has poor prognosis compared with Grade 3 endometrioid adenocarcinoma and is often associated with the loss of mismatch repair (MMR) proteins, which is seen in microsatellite instability (MSI)-type endometrial cancer. Recent studies have shown that the effectiveness of immune checkpoint inhibitor therapy is related to MMR deficiency; therefore, we analyzed the immunophenotype (MMR deficient and expression of PD-L1) of 17 DDEC cases. In the undifferentiated component, nine cases (53%) were deficient in MMR proteins and nine cases (53%) expressed PD-L1. PD-L1 expression was significantly associated with MMR deficiency (p = 0.026). In addition, the presence of tumor-infiltrating lymphocytes (CD8+) was significantly associated with MMR deficiency (p = 0.026). In contrast, none of the cases showed PD-L1 expression in the well-differentiated component. Our results show that DDEC could be a target for immune checkpoint inhibitors (anti PD-L1/PD-1 antibodies), especially in the undifferentiated component. As a treatment strategy for DDEC, conventional paclitaxel plus carboplatin and cisplatin plus doxorubicin therapies are effective for those with the well-differentiated component. However, by using immune checkpoint inhibitors in combination with other conventional treatments, it may be possible to control the undifferentiated component and improve prognosis.