Molecular Pathology of Thyroid Tumors: Essential Points to Comprehend Regarding the Latest WHO Classification.

In 2022, the new WHO Classification of Endocrine and Neuroendocrine Tumors, Fifth Edition (beta version) (WHO 5th), was published. Large-scale genomic analyses such as The Cancer Genome Atlas (TCGA) have revealed the importance of understanding the molecular genetics of thyroid tumors. Consequently, the WHO 5th was fundamentally revised, resulting in a systematic classification based on the cell of origin of tumors and their clinical risk. This paper outlines the following critical points of the WHO 5th. 1. Genetic mutations in follicular cell-derived neoplasms (FDNs) highlight the role of mutations in the MAP kinase pathway, including RET, RAS, and BRAF, as drivers of carcinogenesis. Differentiated thyroid cancers such as follicular thyroid carcinoma (FTC) and papillary thyroid carcinoma (PTC) have specific genetic alterations that correlate with morphological classifications: RAS-like tumors (RLTs) and BRAF p.V600E-like tumors (BLTs), respectively. 2. The framework for benign lesions has been revised. The WHO 5th introduces a new category: "developmental abnormalities". Benign FDNs comprise "thyroid follicular nodular disease", follicular thyroid adenoma (FTA), FTA with papillary architecture, and oncocytic adenoma (OA). "Hürthle cell adenoma/carcinoma" is renamed oncocytic adenoma/carcinoma of the thyroid (OA/OCA), which can be distinguished from FTA/FTC by its unique genetic background. 3. Low-risk tumors include NIFTP, TT-UMP, and HTT, and they have an extremely low malignant potential or an uncertain malignant potential. 4. PTC histological variants are reclassified as "subtypes" in the WHO 5th. 5. The concept of high-grade carcinomas is introduced, encompassing poorly differentiated thyroid carcinoma (PDTC), differentiated high-grade thyroid carcinoma (DHGTC), and high-grade medullary thyroid carcinoma (MTC). 6. Squamous cell carcinoma is included in anaplastic thyroid carcinoma (ATC) in the WHO 5th due to their shared genetic and prognostic features. 7. Other miscellaneous tumors are categorized as salivary-gland-type carcinomas of the thyroid, thyroid tumors of uncertain histogenesis, thymic tumors within the thyroid, and embryonal thyroid neoplasms. The WHO 5th thus emphasizes the importance of classifying tumors based on both genetic abnormalities and histomorphology. This approach aids in achieving accurate pathological diagnosis and facilitates the early selection of appropriate treatment options, including molecular targeted therapies.

Prevalence and diagnostic significance of non-invasive follicular thyroid neoplasm with papillary-like nuclear features in Japan-A multi-institutional study.

This multi-institutional study investigated non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) frequency and its diagnostic significance in Japan. We reviewed 4008 thyroid nodules resected in six institutions before NIFTP was proposed. Overall, 26 cases diagnosed as non-invasive encapsulated follicular variant of papillary thyroid carcinoma (PTC) and 145 cases of follicular thyroid adenoma (FTA) were included. Of these nodules, 80.8% and 31.0%, respectively, were NIFTPs. In five institutions, NIFTPs were more commonly found in FTA than in PTC nodules. When NIFTP was included with PTC, the overall prevalence was 2.3%, with rates in five institutions below 5.0% (0.8%-4.4%). One NIFTP case with nuclear score 3 revealed nodal metastasis 2.5 years post-resection, and the carcinoma cells were immunohistochemically positive for BRAF. FTAs or NIFTPs with nuclear score 2 did not metastasize. NIFTP was more common among FTA than among PTC nodules, possibly due to underdiagnosis of PTC on nuclear findings. Considering the clinical findings, molecular pathogenesis, and therapeutic strategy in Japan, NIFTP with nuclear score 2 is not different from FTA, and use of this entity terminology is not meaningful. In contrast, NIFTP with nuclear score 3 has potential for metastasis and BRAFV600E mutation. Therefore, in NIFTP cases, nuclear scores 2 and 3 should be separately reported.

Microanatomical organization of hepatic venous lymphatic system in humans.

Lymphatic fluid drains from the liver via the periportal lymphatic, hepatic venous lymphatic, and superficial lymphatic systems. We performed a postmortem study to clarify the three-dimensional structure and flow dynamics of the human hepatic venous lymphatic system, as it still remains unclear. Livers were excised whole from three human cadavers, injected with India ink, and sliced into 1-cm sections from which veins were harvested. The distribution of lymphatic vessels was observed in 5 µm sections immunostained for lymphatic and vascular markers (podoplanin and CD31, respectively) using light microscopy. Continuity and density of lymphatic vessel distribution were assessed in en-face whole-mount preparations of veins using stereomicroscopy. The structure of the external hepatic vein wall was assessed with scanning electron microscopy (SEM). The lymphatic dynamics study suggested that lymphatic fluid flows through an extravascular pathway around the central and sublobular veins. A lymphatic vessel network originates in the wall of sublobular veins, with a diameter greater than 110 µm, and the peripheral portions of hepatic veins and continues to the inferior vena cava. The density distribution of lymphatic vessels is smallest in the peripheral portion of the hepatic vein (0.03%) and increases to the proximal portion (0.22%, p = 0.012) and the main trunk (1.01%, p < 0.001), correlating positively with increasing hepatic vein diameter (Rs = 0.67, p < 0.001). We revealed the three-dimensional structure of the human hepatic venous lymphatic system. The results could improve the understanding of lymphatic physiology and liver pathology.

Identifying large vessel occlusion using the hyperdense artery sign in patients treated with mechanical thrombectomy.

OBJECTIVES: The hyperdense artery sign on non-contrast computed tomography-reconstructed images is useful for identifying large vessel occlusion in acute ischemic stroke. This study aimed to assess its efficacy in patients with large vessel occlusion treated with mechanical thrombectomy. MATERIALS AND METHODS: This retrospective and prospective single-centered study from June 2019 to May 2021 evaluated the use of non-contrast computed tomography-reconstructed images for detecting hyperdense artery sign to identify large vessel occlusion from June 2020 to May 2021. We registered consecutive potential candidates for mechanical thrombectomy due to suspected stroke and assessed the accuracy of hyperdense artery sign on non-contrast computed tomography-reconstructed images for large vessel occlusion in the hyperacute setting. Non-contrast computed tomography images were reconstructed into maximum intensity projection images with iterative reconstruction algorithms to detect hyperdense artery signs. We compared the door-to-puncture time and functional outcome at 90 days before and after employing non-contrast computed tomography-reconstructed images in patients with large vessel occlusion treated with mechanical thrombectomy. RESULTS: The cohort included 82 patients, wherein 47 were treated with mechanical thrombectomy. The sensitivity (96%) and specificity (94%) of hyperdense artery sign on non-contrast computed tomography-reconstructed images for large vessel occlusion were performed. The door-to-puncture time was significantly shortened after using non-contrast computed tomography-reconstructed images (49 versus 28 min, p = 0.001), but the functional outcome at 90 days remained unchanged. CONCLUSIONS: Non-contrast computed tomography-reconstructed images, as a vascular imaging tool for mechanical thrombectomy, can reduce workflow time in hospitals by identifying large vessel occlusion with high sensitivity and specificity.

Immune microenvironment, homologous recombination deficiency, and therapeutic response to neoadjuvant chemotherapy in triple-negative breast cancer: Japan Breast Cancer Research Group (JBCRG)22 TR.

BACKGROUND: Triple-negative breast cancer (TNBC) is a biologically diverse disease, with characteristics such as homologous recombination deficiency (HRD), gene mutation, and immune reactions. Japan Breast Cancer Research Group 22 is a multicenter trial examining TNBC's response to neoadjuvant chemotherapy (NAC) according to the HRD status. This translational research investigated the clinical significance of the immune microenvironment of TNBC in association with HRD, tumor BRCA1/2 (tBRCA1/2) mutation, and response to NAC. METHODS: Patients aged below 65 years with high HRD or germline BRCA1/2 (gBRCA1/2) mutation randomly received paclitaxel + carboplatin (group A1) or eribulin + carboplatin (A2), followed by anthracycline. Patients aged below 65 years with low HRD or those aged 65 years or older without gBRCA1/2 mutation randomly received eribulin + cyclophosphamide (B1) or eribulin + capecitabine (B2); nonresponders to the first four cycles of the therapy received anthracycline. A pathological complete response (pCR) was defined as the absence of residual cancer cells in the tissues. Pretreatment biopsy specimens were stained by multiplexed fluorescent immunohistochemistry using antibodies against CD3, CD4, CD8, Foxp3, CD204, and pan-cytokeratin. Immune cells with specific phenotypes were counted per mm2 in cancer cell nests (intratumor) and stromal regions. The immune cell densities were compared with clinicopathological and genetic factors including tumor response. RESULTS: This study analyzed 66 samples. T1 tumors had a significantly higher density of intratumoral CD8+ T cells than T2 or larger tumors. The tBRCA1/2 mutation or HRD status was not associated with the density of any immune cell. The density of intratumoral and stromal CD4+ T cells was higher in patients showing pCR than in those without pCR. In a multivariate analysis, intratumoral and stromal CD4+ T cell density significantly predicted pCR independent of age, chemotherapy dose, HRD status, and treatment groups (P = 0.009 and 0.0057, respectively). In a subgroup analysis, the predictive value of intratumoral and stromal CD4+ T cell density persisted in the platinum-containing chemotherapy group (A1+A2) but not in the non-platinum-containing group (B1+B2). CONCLUSIONS: Intratumoral and stromal CD4+ T cell density was an independent predictor of pCR in patients with TNBC. A larger study is warranted to confirm the results. TRIAL REGISTRATION: UMIN000023162.

Correlation between low expression of protein disulfide isomerase A3 and lymph node metastasis in papillary thyroid carcinoma and poor prognosis: a clinicopathological study of 1,139 cases with long-term follow-up.

The incidence of papillary thyroid carcinoma (PTC) is increasing worldwide. The biomarkers to identify aggressive types of PTC are limited, illustrating the need to establish reliable novel biomarkers. Protein disulfide isomerase A3 (PDIA3) is a chaperone protein that modulates the folding of newly synthesized glycoproteins and stress-responsive proteins in the endoplasmic reticulum. Although the role of PDIA3 in various cancers such as breast, uterine cervix, head and neck, and gastrointestinal tract has been examined, its expression in thyroid cancer has not been reported. We retrospectively reviewed accumulated data with long-term follow-up of 1,139 PTC patients, and investigated the correlation between immunohistochemical expression of PDIA3 in PTC patients and clinicopathological features and prognosis. PDIA3 expression was significantly lower in PTCs compared to normal thyroid tissues (NTT; n = 80, p = 0.002). In PTCs, correlation between low PDIA3 expression and lymph node metastasis (p = 0.018) and the number of positive nodes (p = 0.004) was observed. Patients with low PDIA3 expression exhibited worse cause-specific survival compared to those with high PDIA3 expression (p = 0.013). Our findings indicate that low PDIA3 expression is related to poor clinical outcome in PTC patients, and that PDIA3 may potentially be a novel ancillary biomarker. Further clarification of the biological role of PDIA3 in PTC is warranted for the future clinical application.

Pathological diagnosis of general rules for the description of thyroid cancer by Japanese Society of Thyroid Pathology and Japan Association of Endocrine Surgery.

The Japanese Society of Thyroid Pathology and the Japan Association of Endocrine Surgeons developed the eighth edition of the General Rules for the Description of Thyroid Cancer (GRDTC) in December 2019. This article describes the pathological diagnosis of the GRDTC, which has been improved through repeated revisions based on the experience of Japanese pathologists and translated into English to introduce the Japanese diagnostic standard to foreign countries. In this edition of the GRDTC, the histopathological classification and descriptions differ in some respects from those of the fourth edition of the World Health Organization (WHO) classification as revised in 2017. For example, the GRDTC does not adopt the concept of borderline lesions (FT-UMP, WDT-UMP, and NIFTP) of the WHO, taking into consideration the popular histological criteria accepted by Japanese pathologists. The cytological reporting system of the GRDTC was partly modified from the Bethesda system in 2015. It has an additional cyst fluid category separated from the unsatisfactory category that has been demonstrated to be useful in Japan. This translated edition makes it easy to submit Japanese clinicopathological studies of thyroid tumors in an international journal. We also wish to contribute to the improvement, standardization, and globalization of the pathological diagnosis of thyroid tumors.

Observation of a tight junction structure generated in LbL-3D skin reconstructed by layer-by-layer cell coating technique.

Tissue-engineered skin equivalents are reconstructed the functions of human skin and can be used as an alternative to animal experiments in basic study or as cultured skin for regenerative medicine. Recent studies confirmed that epidermal tight junctions (TJs), which are complex intercellular junctions formed in the stratum granulosum of human skin, play an important part in the formation of the skin barrier function. In well-formed reconstructed human skin models, there are several reports on the expression of TJ proteins and their localization in epidermal layer, however, the morphological features of TJ, showing tight junctional contacts and the process of TJ formation have yet to be investigated. In this study, we systematically examined and identified TJ-related proteins and TJ structure in three-dimensional (3D) human skin equivalents reconstructed by layer-by-layer (LbL) cell coating technique (LbL-3D Skin). We demonstrate localization of TJ-related proteins and time course of formation of TJ structure with typical junctional morphology in LbL-3D Skin. These data provide evidence that the LbL-3D Skin is an in vitro model with structure and function extremely similar to living skin.

Long-term results of fluorescence and indigo carmine blue dye-navigated sentinel lymph node biopsy.

BACKGROUND: Sentinel lymph node biopsy is widely applied for the management of clinically node-negative breast cancer, and a radioisotope with a blue dye are most often used as tracers. Fluorescence of indocyanine green could also potentially be used as tracer. This study aimed to demonstrate the long-term survival results of fluorescence-guided sentinel lymph node biopsy. PATIENTS AND METHODS: Patients with clinically node-negative breast cancer who underwent surgery as initial treatment were included in this study. Both fluorescence of indocyanine green and indigo carmine blue dye were used as tracers. Axillary lymph node dissection was omitted unless metastasis was pathologically proven in sentinel nodes. Breast cancer recurrence and death were recorded and prognostic factors were identified using disease-free survival and overall survival data. RESULTS: A total of 565 patients were analyzed. There were 14 (2.5%) patients whose sentinel nodes could not be identified, yielding an identification rate of 97.5%. Axillary dissection was performed in 90 patients. Forty-three recurrences including 6 ipsilateral axilla recurrence and 13 deaths were observed during the median 83 months of follow-up period. Seven-year disease-free and overall survival were 92.4% and 97.3%, respectively. Multivariate analyses demonstrated that pre-menopausal status and invasive lobular carcinoma were significant unfavorable prognostic factors of disease-free survival. Half of ipsilateral axilla recurrences occurred within 5 years after surgery and these recurrences were correlated with inappropriate adjuvant therapy. CONCLUSION: Fluorescence-guided sentinel lymph node biopsy demonstrated favorable prognostic results and could be alternative to the radioisotope for clinically node-negative breast cancer.

Immunogenomic landscape of gynecologic carcinosarcoma.

OBJECTIVE: Carcinosarcoma (CS) of the uterus or ovary is a rare, biphasic tumor comprising epithelial and mesenchymal elements, and exhibits more aggressive clinical features than its carcinoma counterpart. Four molecular subtypes of CS were recently established based on genomic aberration profiles (POLE, MSI, CNH, and CNL) and shown to be associated with multiple clinicopathological parameters, including patient outcomes. However, the role of the immune microenvironment in CS remains unclear. Here, we investigated the influence of the immune cells that infiltrate CS to better understand the immunological status of gynecological CS. METHODS: Tumor immune microenvironmental analyses on CS samples were performed using immune cell profiling with RNA-seq, transcriptomic subtyping with microenvironmental genes, and T-cell receptor repertoire assay. Carcinoma and sarcoma elements from CS samples were also assessed separately. RESULTS: Relying on estimations of tumor-infiltrating cell types from RNA-seq data, POLE and MSI (hypermutator) tumors showed an enrichment of M1 macrophages, plasma cells and CD8+ T cells, whereas CNH and CNL (non-hypermutator) tumors had high levels of M2 macrophages. Further subclassification by immune-related, non-cancer genes identified a fraction of tumors with distinct patient outcomes, particularly those with the CNH genomic aberration subtype. T-cell heterogeneity was independently correlated with prolonged progression-free survival. Differential analysis of carcinoma and sarcoma elements identified many shared mutations but there was little overlap in the T-cell receptor repertoire between the two elements. CONCLUSIONS: Tumor immune microenvironmental analyses could offer potential clinical utility in the stratification of gynecological CS above classification by genomic aberration subtype alone.

Regulatory Single Nucleotide Polymorphism Increases TERT Promoter Activity in Thyroid Carcinoma Cells.

BACKGROUND/AIM: The telomerase reverse transcriptase (TERT) promoter has a regulatory single nucleotide polymorphism (rSNP), rs2853669, and occasionally shows point mutations C228T and C250T. Although C228T and C250T have been well examined to increase TERT promoter activity and are known as risk factors for thyroid carcinoma, the significance of rs2853669 has not been well investigated. This study aimed to clarify the influence of rs2853669 on TERT promoter activity in thyroid carcinoma cells. MATERIALS: Seven of 8 examined thyroid cell lines had rs2853669, 5 had C228T, and 1 had C250T. RESULTS: Three papillary thyroid carcinoma cell lines, harboring both rs2853669 and C228T, showed higher TERT mRNA expression on real-time PCR than the other cell lines. Anaplastic thyroid carcinoma cell lines, in contrast, showed variable TERT mRNA expression depending on the combination of rs2853669, C228T, and C250T. Luciferase assays, performed to compare the influences of rs2853669, C228T, and C250T on TERT promoter activity in thyroid carcinoma, showed that rs2853669, as well as C228T, increased the promoter activity, and the combination of rs2853669 and C228T increased the promoter activity even more strongly than C228T alone. CONCLUSION: We conclude that the presence of rs2853669 within the TERT promoter could be as significant as the C228T mutation in thyroid carcinoma.

Immunohistochemical markers and the clinical course of adenosarcoma: a series of seven cases.

BACKGROUND: Uterine adenosarcoma, a rare uterine tumor subtype, is a biphasic tumor consisting of epithelial and mesenchymal elements. To date, there is no research comparing the histopathological features and immunohistochemistry of primary and recurrent tumors; furthermore, the relationship between pathology and the clinical course remains unclear. We reviewed the pathology and immunohistochemical features of patients with adenosarcoma and investigated the relevance of the histomorphological features to the clinical course. We also compared the immunohistochemical features of the primary and recurrent tumors. METHODS: The data of seven patients with adenosarcoma who underwent surgery in our hospital were evaluated. We performed immunohistochemical staining for the progesterone receptor, estrogen receptor, p53, and two Switch/Sucrose Non-Fermentable chromatin remodeling proteins (SMARCA4, BCOR), which were recently developed for the undifferentiated sarcoma diagnosis in addition to conventional staining methods. RESULTS: All patients had International Federation of Gynecology and Obstetrics stage IB-IC diseases. All tumors were polypoid and every patient presented with abnormal uterine bleeding. Six patients aged over 50 years and were menopausal; one patient aged under 50 years and was non-menopausal (average age: 59.1 years). Histologically, the sarcomatous components were homologous and heterogenous in six and one patient, respectively. Four and three cases were recurrent and non-recurrent, respectively. The recurrent patients showed high-grade morphology with sarcomatous overgrowth and were negative for ER and PR. Three recurrences could be evaluated by imaging, showing recurrence only in a distant area; biopsy specimens from these tissues revealed the identical mesenchymal component found in the primary tumor without a benign epithelial component. Immunohistochemical staining results were also similar to the corresponding of the original tumor, except for the p53 expression in one patient. At the primary site, p53 was overexpressed in two recurrent patients and had a wild-type level in one recurrent patient; however, all three recurrent tissues showed p53 overexpression. None of our patients showed SMARCA4 loss, and BCOR expression was positive in one case. CONCLUSIONS: Initial pathological adenosarcoma analysis with appropriate immunohistochemical staining is vital for prognostic assessment. p53 expression might increase at recurrence. SMARCA4 and BCOR might not be an index of malignancy.

Gastropathy associated with lanthanum phosphate deposition that was endoscopically tracked for 3 years. A case report.

BACKGROUND: With the recent increased use of lanthanum carbonate, several cases of lanthanum phosphate deposition to gastric mucosa in dialysis patients have been reported. However, the endoscopic appearance of the early-stage lesion and the over-time alterations of endoscopic findings due to the progression of lanthanum phosphate deposition remain unclear. CASE PRESENTATION: An 80-year-old man receiving dialysis and taking lanthanum carbonate as a phosphate binder over a 4-year period underwent upper gastrointestinal endoscopy four times beginning 1 year after initiation of treatment. The first endoscopic examination (after 1 year of exposure to lanthanum carbonate) revealed rough mucosa with a few areas of white granular mucosa. Over the 3 years of endoscopic follow-up, the white granular mucosa spread and multiple erosions appeared. Histopathological findings of biopsy specimens from an erosion showed extensive infiltration by histiocytes containing deposits. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) revealed that the presence of the deposits containing phosphorus and lanthanum in the gastric mucosa. On the basis of these results, the patient was diagnosed with gastropathy associated with lanthanum phosphate deposition. CONCLUSIONS: Over a 3-year period, endoscopic findings associated with lanthanum deposition gradually changed and expanded from the early stage.

Functional characterization of a germline ETV6 variant associated with inherited thrombocytopenia, acute lymphoblastic leukemia, and salivary gland carcinoma in childhood.

Germline pathogenic ETV6 variants have been discovered in families with inherited thrombocytopenia and predisposition to hematological and solid malignancies. We present a patient with short stature who was initially diagnosed with chronic immune thrombocytopenia. Subsequently, the patient developed acute lymphoblastic leukemia, followed by mammary analog secretory carcinoma. Sequencing analysis identified an ETV6 c.641C > T (p.Pro214Leu) germline variant. The variant protein exhibited attenuated nuclear localization, increased protein degradation, and reduced transcription repression function. Our findings suggest that the ETV6 gene should be sequenced in patients with inherited thrombocytopenia and malignancy, and emphasize the importance of careful follow-up to identify secondary cancer in patients with pathogenic ETV6 variants.

Clinicopathological significance of the single nucleotide polymorphism, rs2853669 within the TERT promoter in papillary thyroid carcinoma.

Papillary thyroid carcinoma (PTC) is the most common thyroid malignancy. Point mutations in the telomerase reverse transcriptase (TERT) promoter, C228T and C250T and oncogene BRAFV600E have been investigated as risk factors for PTC. However, little research has been done on the single nucleotide polymorphism rs2853669 in the TERT promoter in PTC. This study aimed to clarify the clinicopathological significance of rs2853669 in Japanese patients with PTC. The genetic frequencies of rs2853669, C228T, C250T and BRAFV600E were investigated in 58 patients with PTC and compared with the clinicopathological parameters of PTC. rs2853669, C228T, C250T and BRAFV600E were found in 58.6%, 17.2%, 5.2% and 37.0% of the PTC patients, respectively. PTC with rs2853669 and C228T were associated only with tumor sizes larger than 2.0 cm (P < 0.05). Furthermore, the coexistence of rs2853669 and C228T was strongly associated with tumor size (P < 0.01), with an odds ratio of 6.4 (P < 0.05). We showed that rs2853669, as well as C228T, may be a risk factor for the aggressiveness of PTC, and the coexistence of these mutations might represent greater risk.

Effect of single-nucleotide polymorphism in TERT promoter on follicular thyroid tumor development.

Follicular thyroid neoplasm is a common tumor, and consists of follicular thyroid adenoma (FTA) and carcinoma (FTC). The mechanisms of tumor development of FTA and FTC are not well-understood. Single-nucleotide polymorphisms (SNPs) and point mutations in the telomerase reverse transcriptase (TERT) promoter have been associated with tumor development of many cancers. In order to clarify the significance of TERT promoter SNPs and mutations, including rs2853669 (-245T>C), C228T, and C250T, we analyzed 59 FTA patients and 19 FTC patients. Rs2853669 was found in 67.8% (40/59) and 57.9% (11/19) of FTAs and FTCs, respectively, and homozygous rs2853669 (CC) was more frequently found in FTC than in FTA. Furthermore, in FTA, rs2853669 was significantly associated with tumor size greater than 2.0 cm (P < 0.05). C228T was found in 5.1% and 36.8% of FTAs and FTCs, respectively. Frequencies of rs2853669 or/and C228T mutation were 71.2% in FTAs and 73.7%, in FTCs, and were significantly associated with larger tumor sizes in FTAs (P < 0.05). Rs2853669 is considered to be associated with tumor development in FTA and FTC.

Poor outcomes in carriers of the RNF213 variant (p.Arg4810Lys) with pulmonary arterial hypertension.

BACKGROUND: A variant of c.14429G>A (p.Arg4810Lys, rs112735431) in the ring finger protein 213 gene (RNF213; NM_001256071.2) has been recently identified as a risk allele for pulmonary arterial hypertension (PAH). PAH can be added as a new member of RNF213-associated vascular diseases, which include Moyamoya disease and peripheral pulmonary stenosis. Our aim was to identify the clinical features and outcomes of PAH patients with this variant. METHODS: Whole-exome sequencing was performed in 139 idiopathic (or possibly heritable) PAH patients. RESULTS: The RNF213 p.Arg4810Lys variant was identified in a heterozygous state in 11 patients (7.9%). Time-course changes in hemodynamics after combination therapy in the patients with the RNF213 p.Arg4810Lys variant were significantly poorer compared with those carrying the bone morphogenic protein receptor type 2 (BMPR2) mutation (n = 36) (comparison of changes in mean pulmonary arterial pressure, p = 0.007). The event-free rate of death or lung transplantation was significantly poorer in RNF213 p.Arg4810Lys variant carriers than in BMPR2 mutation carriers (5-year event-free rate since the introduction of prostaglandin I2 infusion, 0% vs 93%, respectively; p < 0.001). CONCLUSIONS: Idiopathic PAH patients with the RNF213 p.Arg4810Lys variant are associated with poor clinical outcomes even in recent times. Earlier consideration of lung transplantation might be required for RNF213 p.Arg4810Lys variant carriers who are developing PAH. Documentation of the RNF213 p.Arg4810Lys variant, as well as already known pathogenic genes, such as BMPR2, can provide clinically relevant information for therapeutic strategies, leading to a personalized approach for the treatment of PAH.

Endothelial-Mesenchymal Transition Drives Expression of CD44 Variant and xCT in Pulmonary Hypertension.

Pulmonary arterial hypertension (PAH) pathogenesis shares similarities with carcinogenesis. One CD44 variant (CD44v) isoform, CD44v8-10, binds to and stabilizes the cystine transporter subunit (xCT), producing reduced glutathione and thereby enhancing the antioxidant defense of cancer stem cells. Pharmacological inhibition of xCT by sulfasalazine suppresses tumor growth, survival, and resistance to chemotherapy. We investigated whether the CD44v-xCT axis contributes to PAH pathogenesis. CD44v was predominantly expressed on endothelial-to-mesenchymal transition (EndMT)-like cells in the neointimal layer of PAH affected pulmonary arterioles. In vitro, CD44 standard form and CD44v were induced as a result of EndMT. Among human pulmonary artery endothelial cells that have undergone EndMT, CD44v+ cells showed high levels of xCT expression on their cell surfaces and high concentrations of glutathione for survival. This made CD44v+ cells the most vulnerable target for sulfasalazine. CD44v+xCThi cells showed the highest expression levels of proinflammatory cytokines, antioxidant enzymes, antiapoptotic molecules, and cyclin-dependent kinase inhibitors. In the Sugen5416/hypoxia mouse model, CD44v+ cells were present in the thickened pulmonary vascular wall. The administration of sulfasalazine started either at the same time as "Sugen5416" administration (a prevention model) or after the development of pulmonary hypertension (a reversal model) attenuated the muscularization of the pulmonary vessels, decreased the expression of markers of inflammation, and reduced the right ventricular systolic pressure, while reducing CD44v+ cells. In conclusion, CD44v+xCThi cells appear during EndMT and in pulmonary hypertension tissues. Sulfasalazine is expected to be a novel therapeutic agent for PAH, most likely targeting EndMT-derived CD44v+xCThi cells.