Whole-exome mutational landscape of neuroendocrine carcinomas of the gallbladder

Neuroendocrine carcinoma(NEC)of the gallbladder(GB-NEC)is a rare but extremely malignant subtype of gallbladder cancer(GBC).The genetic and molecular signatures of GB-NEC are poorly understood;thus,molecular targeting is currently unavailable.Inthe present study,we applied whole-exome sequencing(WES)technology to detect gene mutations and predicted somatic singlenucleotide variants(SNVs)in 15 cases of GB-NEC and 22 cases of general GBC.in 15 GB-NECs,the C>T mutation was predominantamong the 6 types of SNVs.TP53 showed the highest mutation frequency(73%,11/15).Compared with neuroendocrine carcinomasof other organs,signifcantly mutated genes(SMGs)in GB-NECs were more similar to those in pulmonary large-cell euroendocrinecarcinomas(LCNECs),with drver roles for TP53 and RB1.Iin the COSMIC database of cancer-related genes,211 genes were mutated.Strikingly,RB1(4/15,27%)and NAB2(3/15,20%)mutations were found specifically in GB-NECs;in contrast,mutations in 29 genes,including ERB82 and ERBB3,were identified exclusively in GBC.Mutations in RB1 and NAB2 were significanty related to downregulation of the RB1 and NAB2 proteins,respectively,according to immunohistochemical(IHC)data(p values=0.0453 and0.0303).Clinically actionable genes indicated 23 mutated genes,including ALK,BRCA1,and BRCA2.Iin addition,potential somaticSNVs predicted by ISowN and SomVarlUS constituted 6 primary coSMIC mutation signatures(1,3,30,6,7,and 13)in GB-NEC.Genes carrying somatic SNVs were enriched mainly in oncogenic signaling pathways involving the Notch,WNT,Hippo,and RTK-RASpathways.In summary,we have systematically identified the mutation landscape of GB-NEC,and these findings may providemechanistic insights into the specifc pathogenesis of this deadly disease.