https://hdl.handle.net/20.500.14178/904 2026-03-07T21:03:04Z https://hdl.handle.net/20.500.14178/3532 Mitochondrial Transfer Rescues Respiration to Support De Novo Pyrimidine Biosynthesis and Tumor Progression Dubišová, Mária; Boháčová, Klára; Nahácka, Zuzana; Kraus, Daniel; Novák, Jaromír; Dvořáková, Šárka; Brisudová, Petra; Danešová, Natálie; Selvi, Saba; Hrysiuk, Mariia; Endaya, Berwini Beduya; Botsios, Panagiotis; Le, Thi Dan Diem; Novotná, Monika; Vodenková, Soňa; Truksa, Jaroslav; Chalupský, Karel; Klíma, Kryštof; Procházka, Jan; Sedláček, Radislav; Mengarelli, Francesco; Orlando, Patrick; Tiano, Luca; Boukalová, Štěpána; Berridge, Michael V.; Zobalová, Renata; Neužil, Jiří Cancer cells with severe defects in mitochondrial DNA (mtDNA) can import mitochondria via horizontal mitochondrial transfer to restore respiration. Mitochondrial respiration is necessary for the activity of dihydroorotate dehydrogenase (DHODH), an enzyme of the inner mitochondrial membrane that catalyzes the fourth step of de novo pyrimidine synthesis. In this study, we investigated the role of de novo synthesis of pyrimidines in driving tumor growth in mtDNA-deficient (ρ(0)) cells. Although ρ(0) cells grafted in mice readily acquired mtDNA, this process was delayed in cells transfected with alternative oxidase (AOX), which combines the functions of mitochondrial respiratory complexes III and IV. The ρ(0) AOX cells were glycolytic but maintained normal DHODH activity and pyrimidine production. Deletion of DHODH in a panel of tumor cells completely blocked or delayed tumor growth. The grafted ρ(0) cells rapidly recruited tumor-promoting/stabilizing cells of the innate immune system, including protumor M2 macrophages, neutrophils, eosinophils, and mesenchymal stromal cells (MSC). The ρ(0) cells recruited MSCs early after grafting, which were potential mitochondrial donors. Grafting MSCs together with ρ(0) cancer cells into mice resulted in mitochondrial transfer from MSCs to cancer cells. Overall, these findings indicate that cancer cells with compromised mitochondrial function readily acquire mtDNA from other cells in the tumor microenvironment to restore DHODH-dependent respiration and de novo pyrimidine synthesis. The inhibition of tumor growth induced by blocking DHODH supports targeting pyrimidine synthesis as a potential widely applicable therapeutic approach. SIGNIFICANCE: Mitochondrial complexes III and IV promote tumor progression by supporting de novo pyrimidine synthesis, requiring cancer cells devoid of mitochondrial DNA to recruit mitochondria from source cells to restore respiration in order to form tumors. 2026-01-01T00:00:00Z https://hdl.handle.net/20.500.14178/3530 Basal cell adenoma with S100 protein-positive "stroma": a distinct triphasic salivary gland neoplasm characterized by CTNNB1 mutation Skálová, Alena; Bradová, Martina; Laco, Jan; Vaněček, Tomáš; Hájková, Veronika; Martínek, Petr; Grendár, Marián; Querzoli, Giulia; Leivo, Ilmo; Michal, Michal Basal cell adenoma (BCA) is a benign salivary neoplasm that exhibits a divergent spectrum of growth patterns, including cribriform, tubular, trabecular, membranous, and solid. A subset of BCAs is characterized by the presence of abundant S100 protein-positive stroma, which makes this variant unique and potentially represents a hybrid lesion or an entity intermediate between BCA and pleomorphic adenoma (PA). From the authors' registry, we selected 17 cases of BCA with abundant S100 protein-positive stromal components and compared them with 7 cases of BCA without S100 protein-positive stroma, and 6 cases of myoepithelial cell-rich PAs. All cases were analyzed by immunohistochemistry (IHC) using antibodies to S100 protein, SOX10, PLAG1, HMGA2, p63/p40, cytokeratins, EMA, LEF1, and/or β-catenin. Next-generation sequencing (NGS), fluorescence in situ hybridization (FISH) for the rearrangement of PLAG1, and methylation analysis were performed. The BCA S100 protein stromal cell-rich group consisted of 7 males and 10 females with an average age of 62 years. Their tumors showed typical S100 protein-positive stroma, which was also positive for SOX10 in all cases. The stromal and/or epithelial components showed expression of LEF1 and β-catenin in 17 and 15 cases, respectively. HMGA2 IHC showed nuclear expression in one case while PLAG1 was negative in all cases. In 11 cases, one or more mutations were present, including CTNNB1 mutation (n = 11). The first control cohort of BCA without S100 protein-positive stroma consisted of 1 male and 6 females with an average age of 50 years. This group showed LEF1 and nuclear β-catenin expression in 1 and 2 cases, respectively. The second control group of PA (including 4 spindle-shaped cellular and 2 oncocytic PAs) was devoid of CTNNB1 mutations. Two cases presented with gene fusions, including MEG3::PLAG1 and ACTA2::PLAG1, and an additional two cases showed PLAG1 break. It has been proposed earlier that BCA is related to PA based on a shared biphasic nature and a divergent spectrum of growth patterns. Our findings suggest that BCAs with abundant S100 protein-positive stroma are tumors that morphologically display tricellular differentiation into inner (luminal) ductal epithelial cells, outer (abluminal) basaloid myoepithelial cells, and spindle-shaped stromal S100-positive cells (stromal abluminal). According to our investigation, BCAs with S100 protein-positive stroma represent a distinctive triphasic subset of BCA, which is substantially different from PA, both in immunoprofile and molecular underpinnings. 2026-01-01T00:00:00Z https://hdl.handle.net/20.500.14178/3529 Sclerosing mucoepidermoid carcinoma of salivary glands Othman, Bacem Abdullah Essam Othman Khalele; Bradová, Martina; Simpson, Roderick H W; Laco, Jan; Agaimy, Abbas; Rito, Miguel; Ihrler, Stephan; Steiner, Petr; Grossmann, Petr; Hájková, Veronika; de Rezende, Gisele; Goma, Montse; Koljenovic, Senada; Fonseca, Isabel; Michal, Michal; Leivo, Ilmo; Skálová, Alena Sclerosing mucoepidermoid carcinoma (SMEC) of the salivary glands is a rare variant of low-grade mucoepidermoid carcinoma with scanty cellular atypia characterized by marked fibrosis/sclerosis and a rich inflammatory infiltrate. Herein, we report 25 unpublished cases of SMEC, two of them with prominent eosinophilia (2/25; 8%) and three with abundant IgG4-positive plasma cells (3/25; 12%). In our series of salivary SMEC, molecular analysis using fluorescence in situ hybridization (FISH) and/or next-generation sequencing (NGS) provided evidence of MAML2 gene rearrangement in 18 cases of the 21 analyzable cases tested (86%), while this gene locus was intact in 3 cases (14%). This study focuses on the diagnostic criteria of salivary SMEC given its challenge of abundant collagenous stroma, minimal residual neoplastic areas, and inconspicuous mucous cells. Follow-up data of our cases indicate that salivary SMECs have favorable outcomes. Molecular analysis for MAML2 gene rearrangement suggests that SMECs of salivary glands represent a rare variant of conventional low-grade MECs of salivary glands. In contrast, SMECs of the thyroid gland are genetically distinct from salivary-type thyroid MECs. 2025-01-01T00:00:00Z https://hdl.handle.net/20.500.14178/3528 Sinonasal adenosquamous carcinomas arising in seromucinous hamartoma or respiratory epithelial adenomatoid hamartoma with atypical features: Report of five detailed clinicopathological and molecular characterisation of rare entity Bradová, Martina; Costes-Martineau, Valerie; Laco, Jan; Vaněček, Tomáš; Grossmann, Petr; Němcová, Jana; Pavlovský, Zdeněk; Skálová, Alena; Michal, Michal AIMS: Sinonasal adenosquamous carcinoma (ASC) is a rare tumour classified as a variant of squamous cell carcinoma, exhibiting both squamous and glandular differentiation. ASC has a poorer prognosis compared to sinonasal mucoepidermoid carcinoma (MEC), another uncommon tumour in this region. ASC is believed to originate from metaplastic squamous epithelium, though it may also arise from respiratory epithelium in respiratory epithelial adenomatoid hamartoma (REAH) or seromucinous glands in seromucinous hamartoma (SH). METHODS AND RESULTS: Five cases of sinonasal ASC were retrieved from our registry. Initially, they were classified as sinonasal MEC (n = 3), ASC (n = 2), and carcinoma ex REAH (n = 1). All cases showed adenosquamous malignant proliferation beneath the surface respiratory epithelium with occasional squamous metaplasia, except for one case that showed dysplasia. The respiratory epithelium exhibited an inverted growth pattern consistent with REAH/SH, and displayed atypical sinonasal glands (ASGSH) arising within seromucinous hamartoma. Next-generation sequencing (NGS) revealed multiple pathogenic mutations in two cases, and in case 4 GGA2::PRKCB and EYA2::SERINC3 gene fusions. One case was positive for high-risk HPV. None of the cases exhibited CRTC1/3::MAML2 gene fusion. CONCLUSION: The connection between ASGSH and ASC has not been described in the literature. There is a growing need for additional studies on the morphological, immunohistochemical, and genetic aspects of these tumours. SH/REAH may serve as precursor lesions in the progression of atypical sinonasal glands to malignancy, and their role in tumour development deserves further investigation. 2025-01-01T00:00:00Z