Genomic characterization of vulvar squamous cell carcinoma reveals differential gene expression based on clinical outcome.

OBJECTIVE: The greatest challenge in the management of vulvar squamous cell carcinoma (VSCC) is treatment of recurrent disease where options for surgery and radiation have been exhausted, or treatment of disease where distant metastasis is present. Identification of mutations differentially expressed between tumor from patients who died of aggressive disease and tumor from patients with an indolent course could reveal novel prognostic indicators and guide development of therapeutic drugs. METHODS: From 202 consecutive patients with VSCC, patients who recurred and died of disease (group A) were identified and matched by age, tumor size, depth of invasion and nodal status with those whose disease did not recur (group B). Tumors from 21 patients were subjected to whole exome sequencing of DNA and RNA, immunohistochemistry (IHC) antibodies of PD-L1 and P16, and in-situ hybridization (ISH) for high-risk HPV. RESULTS: Analysis of DNA and RNA revealed six genes that were strongly differentially expressed between group A and B: TGM3, ACVR2A, ROS1, NFEL2, CCND1 and BCL6. Clinically relevant DNA mutations were significantly greater in group A versus B: 7 vs 2.3 mutations per patient. The most common genomic alterations were mutations in TP53 and the promoter region of TERT. Other common genomic events include alterations of FAT1, CDKN2A, PIK3CA, CCND1, and LRP1B. All samples were MSI stable and tumor mutational burden (TMB) was similar in groups A and B. Most VSCC specimens (81%) were positive for PD-L1. CONCLUSIONS: ACVR2A and TGM3 are significantly under-expressed in tumors with poor outcome, suggesting they may play a role in tumor suppression. Clinical outcome of VSCC appears independent of MSI, TMB, or PD-L1 status.