Rare driver mutations in head and neck squamous cell carcinomas converge on NOTCH signaling

Cancer drivers converge on NOTCH Cancer genome–sequencing projects have emphasized the handful of genes mutated at high frequency in patients. Less attention has been directed to the hundreds of genes mutated in only a few patients—the so-called “long tail” mutations. Although rare, these mutations may nonetheless inform patient care. Loganathan et al. developed a reverse genetic CRISPR screen that allowed them to functionally assess in mice nearly 500 long tail gene mutations that occur in human head and neck squamous cell carcinoma (HNSCC). They identified 15 tumor-suppressor genes with activities that converged on the NOTCH signaling pathway. Given that NOTCH itself is mutated at high frequency in HNSCC, these results suggest that the growth of these tumors is largely driven by NOTCH inactivation. Science, this issue p. 1264 Functional analysis of rare mutations in head and neck cancers reveals that NOTCH signaling is disrupted in most tumors. In most human cancers, only a few genes are mutated at high frequencies; most are mutated at low frequencies. The functional consequences of these recurrent but infrequent “long tail” mutations are often unknown. We focused on 484 long tail genes in head and neck squamous cell carcinoma (HNSCC) and used in vivo CRISPR to screen for genes that, upon mutation, trigger tumor development in mice. Of the 15 tumor-suppressor genes identified, ADAM10 and AJUBA suppressed HNSCC in a haploinsufficient manner by promoting NOTCH receptor signaling. ADAM10 and AJUBA mutations or monoallelic loss occur in 28% of human HNSCC cases and are mutually exclusive with NOTCH receptor mutations. Our results show that oncogenic mutations in 67% of human HNSCC cases converge onto the NOTCH signaling pathway, making NOTCH inactivation a hallmark of HNSCC.