SDHx mutations are associated with the PI3K-Akt signaling pathway in vagal paragangliomas

Background: Vagal paraganglioma (VPGL) is a very rare neuroendocrine tumor arising from the paraganglion associated with the vagus nerve. VPGL is mainly characterized by an asymptomatic course and slow growth. However, up to 19% of tumors can metastasize. Due to the rarity of this tumor, information about VPGL is limited to single cases and small sample sets; the data on molecular genetic features is extremely scarce. Methods: For the first time we have analyzed the enrichment of biological pathways associated with mutations in the SDHx genes in VPGLs. Bioinformatics analysis was performed based on the results of high-throughput transcriptome sequencing on an Illumina platform for 33 tumor tissues obtained from patients with vagal paragangliomas. Results: Eight pathways of the Kyoto Encyclopedia of Genes and Genomes (KEGG) database with gene overrepresentation (top-40 mode) have been identified. Significant changes were shown for the cancer-associated PI3K-Akt signaling pathway and interconnected pathways of focal adhesion and interaction of receptors with the extracellular matrix enriched by overexpressed genes. Conclusion: Our result indicates the association of SDHx mutations with changes in the PI3K-Akt signaling pathway in vagal paraganglioma. The potential mechanism of deregulation in this pathway could be linked with a state of pseudohypoxia induced by the dysfunction of succinate dehydrogenase due to mutations in the SDHx genes

ТОРАКОБИФЕМОРАЛЬНОЕ ШУНТИРОВАНИЕ У ПАЦИЕНТКИ ПОСЛЕ НЕОДНОКРАТНЫХ ВМЕШАТЕЛЬСТВ НА АОРТОБЕДРЕННОМ СЕГМЕНТЕ ПО ПОВОДУ АТЕРОСКЛЕРОТИЧЕСКОГО ПОРАЖЕНИЯ

Aortobifemoral bypass is still the gold standard treatment in surgery of the aortofemoral segment. The 1980s – 1990s classic publications showed that primary patency ranges from 76–95% in 5 years, and 75–85% in 10-years [1, 2]. Thrombosis of both branches of the bifurcation prosthesis occurs in 1–4% of patients. These patients may undergo thrombectomy with reconstruction of the distal anastomoses, re-aortofemoral prosthetics and, finally, extraanatomic bypass surgery.Аортобифеморальное шунтирование до сих пор остается «золотым стандартом» в хирургии аортобедренного сегмента. Классические публикации 1980-х – 1990-х гг. показали, что первичная проходимость через 5 лет колеблется в диапазоне 76–95%, а 10-летняя – 75–85% [1, 2]. У 1–4% больных возникают тромбозы обеих бранш бифуркационного протеза. Этим пациентам может быть выполнена тромбэктомия с реконструкцией дистальных анастомозов, повторное аортобедренное протезирование и, наконец, экстраанатомическое шунтирование

Immunohistochemistry and Mutation Analysis of SDHx Genes in Carotid Paragangliomas

Carotid paragangliomas (CPGLs) are rare neuroendocrine tumors often associated with mutations in SDHx genes. The immunohistochemistry of succinate dehydrogenase (SDH) subunits has been considered a useful instrument for the prediction of SDHx mutations in paragangliomas/pheochromocytomas. We compared the mutation status of SDHx genes with the immunohistochemical (IHC) staining of SDH subunits in CPGLs. To identify pathogenic/likely pathogenic variants in SDHx genes, exome sequencing data analysis among 42 CPGL patients was performed. IHC staining of SDH subunits was carried out for all CPGLs studied. We encountered SDHx variants in 38% (16/42) of the cases in SDHx genes. IHC showed negative (5/15) or weak diffuse (10/15) SDHB staining in most tumors with variants in any of SDHx (94%, 15/16). In SDHA-mutated CPGL, SDHA expression was completely absent and weak diffuse SDHB staining was detected. Positive immunoreactivity for all SDH subunits was found in one case with a variant in SDHD. Notably, CPGL samples without variants in SDHx also demonstrated negative (2/11) or weak diffuse (9/11) SDHB staining (42%, 11/26). Obtained results indicate that SDH immunohistochemistry does not fully reflect the presence of mutations in the genes; diagnostic effectiveness of this method was 71%. However, given the high sensitivity of SDHB immunohistochemistry, it could be used for initial identifications of patients potentially carrying SDHx mutations for recommendation of genetic testing

Novel potential causative genes in carotid paragangliomas

Abstract Background Carotid paragangliomas (CPGLs) are rare neuroendocrine tumors that arise from the paraganglion at the bifurcation of the carotid artery and are responsible for approximately 65% of all head and neck paragangliomas. CPGLs can occur sporadically or along with different hereditary tumor syndromes. Approximately 30 genes are known to be associated with CPGLs. However, the genetic basis behind the development of these tumors is not fully elucidated, and the molecular mechanisms underlying CPGL pathogenesis remain unclear. Methods Whole exome and transcriptome high-throughput sequencing of CPGLs was performed on an Illumina platform. Exome libraries were prepared using a Nextera Rapid Capture Exome Kit (Illumina) and were sequenced under 75 bp paired-end model. For cDNA library preparation, a TruSeq Stranded Total RNA Library Prep Kit with Ribo-Zero Gold (Illumina) was used; transcriptome sequencing was carried out with 100 bp paired-end read length. Obtained data were analyzed using xseq which estimates the influence of mutations on gene expression profiles allowing to identify potential causative genes. Results We identified a total of 16 candidate genes (MYH15, CSP1, MYH3, PTGES3L, CSGALNACT2, NMD3, IFI44, GMCL1, LSP1, PPFIBP2, RBL2, MAGED1, CNIH3, STRA6, SLC6A13, and ATM) whose variants potentially influence their expression (cis-effect). The strongest cis-effect of loss-of-function variants was found in MYH15, CSP1, and MYH3, and several likely pathogenic variants in these genes associated with CPGLs were predicted. Conclusions Using the xseq probabilistic model, three novel potential causative genes, namely MYH15, CSP1, and MYH3, were identified in carotid paragangliomas

Mutational load in carotid body tumor

Abstract Background Carotid body tumor (CBT) is a rare neoplasm arising from paraganglion located near the bifurcation of the carotid artery. There is great intra-tumor heterogeneity, and CBT development could be associated with both germline and somatic allelic variants. Studies on the molecular genetics of CBT are limited, and the molecular mechanisms of its pathogenesis are not fully understood. This work is focused on the estimation of mutational load (ML) in CBT. Methods Using the NextSeq 500 platform, we performed exome sequencing of tumors with matched lymph node tissues and peripheral blood obtained from six patients with CBT. To obtain reliable results in tumors with low ML, we developed and successfully applied a complex approach for the analysis of sequencing data. ML was evaluated as the number of somatic variants per megabase (Mb) of the target regions covered by the Illumina TruSeq Exome Library Prep Kit. Results The ML in CBT varied in the range of 0.09–0.28/Mb. Additionally, we identified several pathogenic/likely pathogenic somatic and germline allelic variants across six patients studied (including TP53 variants). Conclusions Using the developed approach, we estimated the ML in CBT, which is much lower than in common malignant tumors. Identified variants in known paraganglioma/pheochromocytoma-causative genes and novel genes could be associated with the pathogenesis of CBT. The obtained results expand our knowledge of the mutation process in CBT as well as the biology of tumor development

Exome analysis of carotid body tumor

Abstract Background Carotid body tumor (CBT) is a form of head and neck paragangliomas (HNPGLs) arising at the bifurcation of carotid arteries. Paragangliomas are commonly associated with germline and somatic mutations involving at least one of more than thirty causative genes. However, the specific functionality of a number of these genes involved in the formation of paragangliomas has not yet been fully investigated. Methods Exome library preparation was carried out using Nextera® Rapid Capture Exome Kit (Illumina, USA). Sequencing was performed on NextSeq 500 System (Illumina). Results Exome analysis of 52 CBTs revealed potential driver mutations (PDMs) in 21 genes: ARNT, BAP1, BRAF, BRCA1, BRCA2, CDKN2A, CSDE1, FGFR3, IDH1, KIF1B, KMT2D, MEN1, RET, SDHA, SDHB, SDHC, SDHD, SETD2, TP53BP1, TP53BP2, and TP53I13. In many samples, more than one PDM was identified. There are also 41% of samples in which we did not identify any PDM; in these cases, the formation of CBT was probably caused by the cumulative effect of several not highly pathogenic mutations. Estimation of average mutation load demonstrated 6–8 mutations per megabase (Mb). Genes with the highest mutation rate were identified. Conclusions Exome analysis of 52 CBTs for the first time revealed the average mutation load for these tumors and also identified potential driver mutations as well as their frequencies and co-occurrence with the other PDMs