Massively Parallel Sequencing Analysis of 68 Gastric-Type Cervical Adenocarcinomas Reveals Mutations in Cell Cycle-Related Genes and Potentially Targetable Mutations

Gastric-type cervical adenocarcinoma (GCA) is an aggressive type of endocervical adenocarcinoma characterized by mucinous morphology, gastric-type mucin, lack of association with human papillomavirus (HPV) and resistance to chemo/radiotherapy. We characterized the landscape of genetic alterations in a large cohort of GCAs, and compared it with that of usual-type HPV-associated endocervical adenocarcinomas (UEAs), pancreatic adenocarcinomas (PAs) and intestinal-type gastric adenocarcinomas (IGAs). GCAs (n=68) were subjected to massively parallel sequencing targeting 410–468 cancer-related genes. Somatic mutations and copy number alterations (CNAs) were determined using validated bioinformatics methods. Mutational data for UEAs (n=21), PAs (n=178) and IGAs (n=148) from The Cancer Genome Atlas (TCGA) were obtained from cBioPortal. GCAs most frequently harbored somatic mutations in TP53 (41%), CDKN2A (18%), KRAS (18%) and STK11 (10%). Potentially targetable mutations were identified in ERBB3 (10%), ERBB2 (8%) and BRAF (4%). GCAs displayed low levels of CNAs with no recurrent amplifications or homozygous deletions. In contrast to UEAs, GCAs harbored more frequent mutations affecting cell cycle related genes including TP53 (41% vs 5%, p<0.01) and CDKN2A (18% vs 0%, p=0.01), and fewer PIK3CA mutations (7% vs 33%, p=0.01). TP53 mutations were less prevalent in GCAs compared to PAs (41% vs 56%, p<0.05) and IGAs (41% vs 57%, p<0.05). GCAs showed a higher frequency of STK11 mutations than PAs (10% vs 2%, p<0.05) and IGAs (10% vs 1%, p<0.05). GCAs harbored more frequent mutations in ERBB2 and ERBB3 (9% vs 1%, and 10% vs 0.5%, both p<0.01) compared to PAs, and in CDKN2A (18% vs 1%, p<0.05) and KRAS (18% vs 6%, p<0.05) compared to IGAs. GCAs harbor recurrent somatic mutations in cell cycle-related genes and in potentially targetable genes, including ERBB2/3. Mutations in genes such as STK11 may be used as supportive evidence to help distinguish GCAs from other adenocarcinomas with similar morphology in metastatic sites.