The mutational landscape of LN metastasis and recurrence in HNSCC

Abstract

Recent whole exome sequencing (WES) studies have reported the mutations that characterize primary head and neck squamous cell carcinomas (HNSCC). While exposure to tobacco, alcohol and HPV infection are known to contribute to HNSCC development and prognosis, the largest obstacle to long term survival is recurrent and metastatic disease. Approximately 50% of patients present with synchronous lymph node metastases (SLNM), where 5-year adjusted survival is ≈85% for patients without SLNM compared with 30-60% in patients with SLNM. 20-30% of patients cured of their primary HNSCC go on to develop recurrent disease, which is usually refractory to standard therapies. Here, we report the first WES study of paired primary tumor and SLNM from 14 HNSCC patients, and paired primary tumor and metachronous loco-regional metastases (MLRM) from 11 HNSCC patients. Primary tumors averaged 67 nonsynonymous mutations per tumor (n=21), SLNM averaged 89.3 (n=12), and MLRM averaged 41.7 (n=9). TP53 was the only gene mutated in a majority (57%) of primary tumors in our cohort. We observed similar rates of mutation in several of the TCGA-defined “HNSCC signature” genes in our primary cohort, including FAT1 (14.3%) and CASP8 (4.8%), among others. While the size of our cohort does not allow for appropriately powered statistical analyses; 206 and 204 genes, were mutated in metastatic tumors, but not the respective paired primary tumors, in the SLNM and MLRM cohorts, respectively. AP2B1 and ITPR3 mutations were enriched in SLNM, as newly acquired mutations were seen in multiple (2 and 2/12) SLNM samples. GLUL and DDR2 mutations were enriched in MLRM, as newly acquired mutations were seen in multiple (2 and 2/9) MLRM samples. All 4 genes have previously been implicated in the metastatic process in other cancers. The potential enrichment of DDR2 mutations in HNSCC metastases is especially intriguing, as mutations in this gene have been shown to confer sensitivity to the SRC-family kinase inhibitor, dasatinib, in lung and breast cancer. Here we report exquisite sensitivity to dasatinib in our HNSCC preclinical models harboring DDR2 mutations, suggesting further investigation of this drug is warranted in recurrent HNSCC. ©2014 American Association for Cancer Research.