Notch family gene mutations associate with high tumor mutational burden in diverse cancers.

Abstract

e14616 Background: The Notch pathway has an important role in tumorigenesis in many types of cancer. Clinical trials with Notch inhibitors are ongoing. Recently, Notch pathway has been reported to be part of tumor immunity and patients with NOTCH1 mutations (mut) showed better outcome to PD-1 inhibitors, however, the underlying mechanism is unknown. Methods: Next generation sequencing (NGS) panel of 450 cancer genes was performed on FFPE tissue and matched blood samples from 1341 solid tumors, including hepatocellular carcinoma (HCC, n = 644), esophageal carcinoma (EC, n = 255), breast cancer (BC, n = 175), small cell lung cancer (SCLC, n = 141), head and neck cancer (HNC, n = 77). Notch family gene (NOTCH1/2/3/4) muts were analyzed. Genomic alterations including single base substitution, short and long insertions/deletion, copy number variation, gene fusion and rearrangement were assessed. Tumor mutational burden (TMB) was calculated in all patients by NGS algorithms. TMB high (TMB-H) was defined as TMB values ≥75% tumors in each tumor type. Results: For all patients, Notch family gene mut (substitution/indel/truncation) were found in 27% EC, 19% SCLC, 12% HNC, 6% BC and 5% HCC. The median TMB was 6.1 muts/Mb. In general, tumors with Notch family gene mut had significantly higher median TMB in pan-cancer cohort when compared with tumors without Notch family gene mut (9.2 vs. 6.1 muts/Mb, p < 0.001). Specifically, tumors with NOTCH1 mut had higher TMB in HCC (8.5 vs 5.5, p = 0.034), in BC (23.2 vs. 4.6, p = 0.006) and in SCLC (14.0 vs. 9.4, p = 0.002), while NOTCH2 mutant tumors presented higher TMB in HCC (18.5 vs. 5.5, p = 0.026), in EC (14.7 vs. 6.9, p = 0.001) and in SCLC (13.2 vs. 4.6, p = 0.026). We found 65% of NOTCH1 mut were located in epidermal growth factor (EGF)-like repeats domain. Classes of the NOTCH1 mutation type were substitution/indel (non-frameshift) (58%) and truncation (42%), while NOTCH2 mut were 88% and 12%. In TMB-H tumors, substitution/indel is the predominant mutation type of Notch family gene (NOTCH1 61%, NOTCH2 100%). Conclusions: Tumors with Notch family gene mut presented higher TMB in multiple cancer types, indicating a potential strategy for targeted and immunotherapy in NOTCH mutant cancers.