Effects of different immune microenvironment characteristics on predictive efficacy of PTCH1 mutations in immune checkpoint inhibitor therapy of solid tumors.

Abstract

e21026 Background: The PTCH1 gene encoding the protein corticosteroid receptor, which regulates the activity of the Sonic Hedgehog (SHH) signaling pathway. Mutations in PTCH1 result in disruption of the SHH signaling pathway and are closely related to the development of various solid tumors. Previous research has shown that mutations of the PTCH1 gene may result in decreased of antigen expression on the surface of tumor cells. However, relevant correlation with the efficacy of ICI therapy and immune microenvironment are still lacking. Methods: NGS data from an independent cohort (the MSKCC study cohort) of 1661 patients and Chinese clinical dataset (panel on 381/733-gene) of 35337 patients with pan-cancer to explore the association between PTCH1 mutations and immune biomarkers. TMB was defined as total number of somatic non-synonymous mutations in coding region. MSI was evaluated by NGS of 500 known MSI loci. PD-L1 expression was evaluated using immunohistochemistry (Dako 22C3). Patients from three independent cohorts (OAK, POPLAR and MSKCC study cohort) and were used to analyze the correlation between PTCH1 mutations and the efficacy of immune checkpoint blockade immunotherapies (ICIs). Estimation of immune filtration cells scores were conducted via TIMER2.0 (http://timer.cistrome.org/). Results: In Chinese cohort, there were 1384 (3.91%) patients harboured PTCH1 mutation ( PTCH1mut), slightly more than the MSKCC cohort (2.52%, 42/1661). For the TMB, both Chinese (median, 24.14 Muts/Mb vs 8.52 Muts/Mb, P ＜0.0001) and MSKCC (median, 22.30 Muts/Mb vs 5.90 Muts/Mb, P = 0.0035) cohort were associated with higher TMB than the wild-type. Supplemental analysis of MSI in the Chinese cohort showed significant differences between the PTCH1mut and PTCH1wt groups (P ＜0.0001), but not on PD-L1 levels (P = 0.64). In terms of prognostic effect with ICIs therapy, PTCH1mut were significantly associated with the overall survival (OS) of NSCLC (median, 5 months vs 11 months; HR = 1.61; 95% CI, 1.00-2.60; P = 0.049) and colorectal (median, 11 months vs 8 months; HR = 0.27; 95% CI, 0.08–0.90; P = 0.023). Interestingly, PTCH1mut in NSCLC was inversely associated with ICIs efficacy, as opposed to other solid tumors. Exploring the correlation between PTCH1 and immune microenvironment, it was found that CD4+ T cell (P＜0.001), macrophages (P＜0.001), NK cells (P＜0.001), and CD8+ T cells (P = 0.015) infiltration was significantly positively correlated in colorectal. But the infiltration of most immune cells was negatively correlated with PTCH1mut in NSCLC, that the B cells (P = 0.005), macrophages (P = 0.049), and NK cells (P = 0.022) had a significant difference. Conclusions: The results showed that the PTCH1 had a high correlation in solid tumors with TMB and MSI. The PTCH1 might a potential biomarker for ICIs therapy, and the immune microenvironment may be a factor affecting of it.