SWI/SNF protein expression status in fumarate hydratase-deficient renal cell carcinoma: immunohistochemical analysis of 32 tumors from 28 patients

Genomic alterations and diagnosis of renal cancer

The application of molecular profiling has made substantial impact on the classification of urogenital tumors. Therefore, the 2022 World Health Organization incorporated the concept of molecularly defined renal tumor entities into its classification, including succinate dehydrogenase-deficient renal cell carcinoma (RCC), FH-deficient RCC, TFE3-rearranged RCC, TFEB-altered RCC, ALK-rearranged RCC, ELOC-mutated RCC, and renal medullary RCC, which are characterized by SMARCB1-deficiency. This review aims to provide an overview of the most important molecular alterations in renal cancer, with a specific focus on the diagnostic value of characteristic genomic aberrations, their chromosomal localization, and associations with renal tumor subtypes. It may not yet be the time to completely shift to a molecular RCC classification, but undoubtedly, the application of molecular profiling will enhance the accuracy of renal cancer diagnosis, and ultimately guide personalized treatment strategies for patients.

Genomic Characteristics and Single-Cell Profiles After Immunotherapy in Fumarate Hydratase-Deficient Renal Cell Carcinoma

PURPOSE

Fumarate hydratase-deficient renal cell carcinoma (FHRCC) is highly malignant, but the urgent need for effective treatment remains unmet. We aimed to analyze the genomic characteristics and microenvironment of FHRCC and the cause of heterogeneous response to immune checkpoint inhibitor (ICI)-based treatment at single-cell level.

EXPERIMENTAL DESIGN

Whole-exome sequencing and IHC staining analyses were performed in 30 advanced FHRCC patients. Single-cell RNA sequencing following ICI-based treatment was conducted in 4 patients. The clinical characteristics, therapeutic effect, and follow-up data were analyzed.

RESULTS

The median tumor mutation burden was only 0.14 mutations per megabase. IHC staining showed an immune-active tumor microenvironment characterized by extensive CD8+ T-cell infiltration. ATM expression was inversely correlated with percentage of tumor-infiltrating CD8+ T cells. Trajectory analysis indicated gradually upregulated exhausted markers and an increased apoptotic trend of CD8+ T cells despite continuous exposure to ICI-based treatment. ICI-based treatment was associated with improved overall response rate (17.6% vs. 0%, P = 0.046) and disease control rate (DCR; 64.7% vs. 12.5%, P = 0.004) compared with tyrosine kinase inhibitor. Among patients with germline mutation, the ORR (16.7% vs. 0%, P = 0.086) and the DCR (66.7% vs. 14.3%, P = 0.011) were higher after ICI-based treatment.

CONCLUSIONS

Immune infiltration is frequent in FHRCC. ICI-based treatment is a promising regimen, and treatment response depends on the functional status of tumor-infiltrating lymphocytes. ICI-based treatment cannot reverse the exhaustion of CD8+ T cells in patients with progressive disease, highlighting the need for additional therapeutic strategies.

[SMARCB1(INI1)-deficient renal cell carcinoma: medullary and beyond : Evolving concepts]

During the last decades, the SWI/SNF chromatin-remodeling complex has received enormous recognition as a major player in the molecular pathogenesis of diverse neoplasms. Accordingly, SWI/SNF defects affecting different subunits of the complex became defining genetic features in the nosology of different neoplastic entities. In the kidney, loss of SMARCB1(INI1) as a major component of the SWI/SNF complex has emerged as the defining genetic marker for renal medullary carcinoma and pediatric malignant rhabdoid tumor. Diagnosis of these two rare entities is based on a set of defined demographic, clinicopathological, immunophenotypic, and genetic (SMARCB1 loss) criteria. Moreover, the sickle cell trait is considered a prerequisite for renal medullary carcinoma. Current knowledge illustrates that SMARCB1 loss is encountered in three major tumor categories in the kidney: (1) histologically defined neoplasms that are primarily driven by de novo SMARCB1 loss (renal medullary carcinoma and malignant rhabdoid tumor); (2) SMRACB1-deficient renal cell carcinoma (RCC) with variable non-specific histology ranging from collecting duct-like, papillary high-grade (papillary type 2), or medullary-like (lacking sickle cell trait), to fully undifferentiated; and (3) biphasic (dedifferentiated) RCC showing a variable SMARCB1-deficient undifferentiated component. The latter variant most frequently originates from pre-existing clear cell RCC but may rarely superimpose on papillary or chromophobe RCC. This review summarizes the major defining features of the emerging SMARCB1-deficient renal neoplasms. All SMARCB1-deficient carcinomas have a poor prognosis in common. Therefore, exact diagnosis of these tumors is a prerequisite for studies investigating new therapies.

Undifferentiated and dedifferentiated urological carcinomas: lessons learned from the recent developments

Loss of the morphological and immunophenotypic characteristics of a neoplasm is a well-known phenomenon in surgical pathology and occurs across different tumor types in almost all organs. This process may be either partial, characterized by transition from well differentiated to undifferentiated tumor component (=dedifferentiated carcinomas) or complete (=undifferentiated carcinomas). Diagnosis of undifferentiated carcinoma is significantly influenced by the extent of sampling. Although the concept of undifferentiated and dedifferentiated carcinoma has been well established for other organs (e.g. endometrium), it still has not been fully defined for urological carcinomas. Accordingly, undifferentiated/ dedifferentiated genitourinary carcinomas are typically lumped into the spectrum of poorly differentiated, sarcomatoid, or unclassified (NOS) carcinomas. In the kidney, dedifferentiation occurs across all subtypes of renal cell carcinoma (RCC), but certain genetically defined RCC types (SDH-, FH- and PBRM1- deficient RCC) seem to have inherent tendency to dedifferentiate. Histologically, the undifferentiated component displays variable combination of four patterns: spindle cells, pleomorphic giant cells, rhabdoid cells, and undifferentiated monomorphic cells with/without prominent osteoclastic giant cells. Any of these may occasionally be associated with heterologous mesenchymal component/s. Their immunophenotype is often simple with expression of vimentin and variably pankeratin or EMA. Precise subtyping of undifferentiated (urothelial versus RCC and the exact underlying RCC subtype) is best done by thorough sampling supplemented as necessary by immunohistochemistry (e.g. FH, SDHB, ALK) and/ or molecular studies. This review discusses the morphological and molecular genetic spectrum and the recent develoments on the topic of dedifferentiated and undifferentiated genitourinary carcinomas.

New developments in existing WHO entities and evolving molecular concepts: The Genitourinary Pathology Society (GUPS) update on renal neoplasia

The Genitourinary Pathology Society (GUPS) reviewed recent advances in renal neoplasia, particularly post-2016 World Health Organization (WHO) classification, to provide an update on existing entities, including diagnostic criteria, molecular correlates, and updated nomenclature. Key prognostic features for clear cell renal cell carcinoma (RCC) remain WHO/ISUP grade, AJCC/pTNM stage, coagulative necrosis, and rhabdoid and sarcomatoid differentiation. Accrual of subclonal genetic alterations in clear cell RCC including SETD2, PBRM1, BAP1, loss of chromosome 14q and 9p are associated with variable prognosis, patterns of metastasis, and vulnerability to therapies. Recent National Comprehensive Cancer Network (NCCN) guidelines increasingly adopt immunotherapeutic agents in advanced RCC, including RCC with rhabdoid and sarcomatoid changes. Papillary RCC subtyping is no longer recommended, as WHO/ISUP grade and tumor architecture better predict outcome. New papillary RCC variants/patterns include biphasic, solid, Warthin-like, and papillary renal neoplasm with reverse polarity. For tumors with 'borderline' features between oncocytoma and chromophobe RCC, a term "oncocytic renal neoplasm of low malignant potential, not further classified" is proposed. Clear cell papillary RCC may warrant reclassification as a tumor of low malignant potential. Tubulocystic RCC should only be diagnosed when morphologically pure. MiTF family translocation RCCs exhibit varied morphologic patterns and fusion partners. TFEB-amplified RCC occurs in older patients and is associated with more aggressive behavior. Acquired cystic disease (ACD) RCC-like cysts are likely precursors of ACD-RCC. The diagnosis of renal medullary carcinoma requires a negative SMARCB1 (INI-1) expression and sickle cell trait/disease. Mucinous tubular and spindle cell carcinoma (MTSCC) can be distinguished from papillary RCC with overlapping morphology by losses of chromosomes 1, 4, 6, 8, 9, 13, 14, 15, and 22. MTSCC with adverse histologic features shows frequent CDKN2A/2B (9p) deletions. BRAF mutations unify the metanephric family of tumors. The term "fumarate hydratase deficient RCC" ("FH-deficient RCC") is preferred over "hereditary leiomyomatosis and RCC syndrome-associated RCC". A low threshold for FH, 2SC, and SDHB immunohistochemistry is recommended in difficult to classify RCCs, particularly those with eosinophilic morphology, occurring in younger patients. Current evidence does not support existence of a unique tumor subtype occurring after chemotherapy/radiation in early childhood.

SWI/SNF-deficient neoplasms of the genitourinary tract

Since the discovery of association of SMARCB1 mutations with malignant rhabdoid tumors and renal medullary carcinoma, mutations in genes of the SWI/SNF chromatin remodeling complex have been increasingly identified across a diverse spectrum of neoplasms. As a group, SWI/SNF complex subunit mutations are now recognized to be the second most frequent type of mutations across tumors. SMARCB1 mutations were originally reported in malignant rhabdoid tumors of the kidney and thought to be pathognomonic for this tumor. However, more broadly, recognition of typical rhabdoid cytomorphology and SMARCB1 mutations beyond rhabdoid tumors has changed our understanding of the pathobiology of these tumors. While mutations of SWI/SNF complex are diagnostic of rhabdoid tumors and renal medullary carcinoma, their clinical relevance extends to potential prognostic and predictive utility in other tumors as well. Beyond SMARCB1, the PBRM1 and ARID1A genes are the most frequently altered members of the SWI/SNF complex in genitourinary neoplasms, especially in clear cell renal cell carcinoma and urothelial carcinoma. In this review, we provide an overview of alterations in the SWI/SNF complex encountered in genitourinary neoplasms and discuss their increasing clinical importance.

[Hereditary kidney cancers: The pathologist's view in 2020]

Hereditary predispositions to adult kidney tumors involve around 5% of tumors and include a dozen of autosomal dominant syndromes. The most frequent tumors encountered in these setting are clear cell renal cell carcinomas, papillary renal cell carcinomas, chromophobe renal cell carcinomas and angiomyolipomas. Their detection is essential in order to adapt individual care and perform genetic screening of at-risk relatives, especially in the national french network PREDIR, labeled by the National Cancer Institute and dedicated to hereditary predispositions to kidney tumors. Targeted genetic analysis, which was guided in particular by the renal tumor subtype, has recently evolved into genetic analysis using panels of genes. Pathologist contribution's remains however central in the diagnosis of hereditary forms since we currently have immunohistochemical biomarkers that allow us to diagnose two specifically hereditary entities: hereditary leiomyomatosis and renal cell carcinoma associated-renal cell carcinoma, associated with a loss of fumarate hydratase and succinate dehydrogenase-deficient renal cell carcinoma associated with a loss of succinate deshydrogenase B expression. These diagnoses must however be confirmed by the identification of pathogenic germline variation in the corresponding genes. Improvement of kidney tumors characterization has also lead to identify new subtypes, expanding the algorithm of renal tumors associated with hereditary setting. Here we aim to review all subtypes of adult renal tumors encountered in predisposition syndromes.

BRM: the core ATPase subunit of SWI/SNF chromatin-remodelling complex-a tumour suppressor or tumour-promoting factor?

BRM (BRAHMA) is a core, SWI2/SNF2-type ATPase subunit of SWI/SNF chromatin-remodelling complex (CRC) involved in various important regulatory processes including development. Mutations in SMARCA2, a BRM-encoding gene as well as overexpression or epigenetic silencing were found in various human diseases including cancer. Missense mutations in SMARCA2 gene were recently connected with occurrence of Nicolaides-Baraitser genetics syndrome. By contrast, SMARCA2 duplication rather than mutations is characteristic for Coffin-Siris syndrome. It is believed that BRM usually acts as a tumour suppressor or a tumour susceptibility gene. However, other studies provided evidence that BRM function may differ depending on the cancer type and the disease stage, where BRM may play a role in the disease progression. The existence of alternative splicing forms of SMARCA2 gene, leading to appearance of truncated functional, loss of function or gain-of-function forms of BRM protein suggest a far more complicated mode of BRM-containing SWI/SNF CRCs actions. Therefore, the summary of recent knowledge regarding BRM alteration in various types of cancer and highlighting of differences and commonalities between BRM and BRG1, another SWI2/SNF2 type ATPase, will lead to better understanding of SWI/SNF CRCs function in cancer development/progression. BRM has been recently proposed as an attractive target for various anticancer therapies including the use of small molecule inhibitors, synthetic lethality induction or proteolysis-targeting chimera (PROTAC). However, such attempts have some limitations and may lead to severe side effects given the homology of BRM ATPase domain to other ATPases, as well as due to the tissue-specific appearance of BRM- and BRG1-containing SWI/SNF CRC classes. Thus, a better insight into BRM-containing SWI/SNF CRCs function in human tissues and cancers is clearly required to provide a solid basis for establishment of new safe anticancer therapies.

ARID1A knockdown triggers epithelial-mesenchymal transition and carcinogenesis features of renal cells: role in renal cell carcinoma

Down-regulation/mutation of AT-rich interactive domain 1A (ARID1A), a novel tumor suppressor gene, has been reported in various cancers. Nevertheless, its role in renal cell carcinoma (RCC) remained unclear and underinvestigated. We thus evaluated carcinogenesis effects of ARID1A knockdown in nonmalignant Madin-Darby canine kidney (MDCK) renal cells using small interfering RNA (siRNA) against ARID1A (siARID1A). The siARID1A-transfected cells had decreased cell death, increased cell proliferation, and cell cycle shift (from G₀/G₁ to G₂/M) compared with those transfected with controlled siRNA (siControl). Additionally, the siARID1A-transfected cells exhibited epithelial-mesenchymal transition (EMT) shown by greater spindle index, increased mesenchymal markers (fibronectin/vimentin), and decreased epithelial markers (E-cadherin/zonula occludens-1). Moreover, the siARID1A-transfected cells had increases in migratory activity, nuclear size, self-aggregated multicellular spheroid size, invasion capability, chemoresistance (to docetaxel), Snail family transcriptional repressor 1 expression, and TGF-β1 secretion. All of these siARID1A-knockdown effects on the carcinogenic features were reproducible in malignant RCC (786-O) cells, which exhibited a higher degree of carcinogenic phenotypes compared with the nonmalignant MDCK cells. Finally, immunohistochemistry showed obvious decrease in ARID1A protein expression in human RCC tissues (n = 23) compared with adjacent normal renal tissues (n = 23). These data indicate that ARID1A down-regulation triggers EMT and carcinogenesis features of renal cells in vitro, and its role in RCC could be proven in human tissues.-Somsuan, K., Peerapen, P., Boonmark, W., Plumworasawat, S., Samol, R., Sakulsak, N., Thongboonkerd, V. ARID1A knockdown triggers epithelial-mesenchymal transition and carcinogenesis features of renal cells: role in renal cell carcinoma.

A chemoproteomic portrait of the oncometabolite fumarate

Hereditary cancer disorders often provide an important window into novel mechanisms supporting tumor growth. Understanding these mechanisms thus represents a vital goal. Toward this goal, here we report a chemoproteomic map of fumarate, a covalent oncometabolite whose accumulation marks the genetic cancer syndrome hereditary leiomyomatosis and renal cell carcinoma (HLRCC). We applied a fumarate-competitive chemoproteomic probe in concert with LC-MS/MS to discover new cysteines sensitive to fumarate hydratase (FH) mutation in HLRCC cell models. Analysis of this dataset revealed an unexpected influence of local environment and pH on fumarate reactivity, and enabled the characterization of a novel FH-regulated cysteine residue that lies at a key protein-protein interface in the SWI-SNF tumor-suppressor complex. Our studies provide a powerful resource for understanding the covalent imprint of fumarate on the proteome and lay the foundation for future efforts to exploit this distinct aspect of oncometabolism for cancer diagnosis and therapy.

Need for high-resolution Genetic Analysis in iPSC: Results and Lessons from the ForIPS Consortium

Genetic integrity of induced pluripotent stem cells (iPSCs) is essential for their validity as disease models and for potential therapeutic use. We describe the comprehensive analysis in the ForIPS consortium: an iPSC collection from donors with neurological diseases and healthy controls. Characterization included pluripotency confirmation, fingerprinting, conventional and molecular karyotyping in all lines. In the majority, somatic copy number variants (CNVs) were identified. A subset with available matched donor DNA was selected for comparative exome sequencing. We identified single nucleotide variants (SNVs) at different allelic frequencies in each clone with high variability in mutational load. Low frequencies of variants in parental fibroblasts highlight the importance of germline samples. Somatic variant number was independent from reprogramming, cell type and passage. Comparison with disease genes and prediction scores suggest biological relevance for some variants. We show that high-throughput sequencing has value beyond SNV detection and the requirement to individually evaluate each clone.