Deciphering genomic characteristics of ERBB family members potentially involved in the recovery of anti-cancer immunity for intrahepatic cholangiocarcinoma patients.

Abstract

e16003 Background: Previous studies showed that the efficacy of immune checkpoint inhibitor (ICI) is enhanced in hepatobiliary cancers harboring activating gene alterations of ERBB family members. The purpose of this study was to explore genomic characteristics of ERBB family members as well as the relationship of them with the activity of anti-cancer immunity in Chinese intrahepatic cholangiocarcinoma (ICC) patients. Methods: Fifty-four ICC patients which carried at least one gene mutation of ERBB family members were pre-selected from 508 ICC patients included in the China Pan-cancer project of OrigiMed 2020 (https://www.cbioportal.org/study/summary?id=pan_origimed_2020). Targeted sequencing was implemented with cancer-related 450-gene panel. Tumor mutation burden (TMB) and microsatellite status were evaluated. To explore the molecular mechanisms, two human cholangiocarcinoma cell lines, RBE and HuCCT1, were transfected with a lentivirus to obtain the cells with stable S310F mutation and overexpression of ERBB2. Results: The variation frequencies of EGFR, ERBB2, ERBB3 and ERBB4 were 2.8% (14/508), 3.5% (18/508), 3.3% (17/508) and 2.4% (12/508) in Chinese ICC patients, respectively. All the patients harboring ERBB family gene mutations were classified as TMB-H (cutoff = 10 Muts/Mb), when co-mutated with ACVR2A or TGFBR2. Moreover, ACVR2A and TGFBR2 were identified as driver genes in the cohort with oncodriveCLUST. TMB and the proportion of MSI-H patients were significantly elevated when ERBB family members co-mutated with ACVR2A (mutation vs wild: TMB, 38.2 ± 19.1 vs 7.0 ± 8.6 Muts/Mb, p<0.0001; MSI-H, 77.8% vs 4.9%, p<0.0001), or with TGFBR2 (TMB, 33.1 ± 8.7 vs 9.0 ± 14.4 Muts/Mb, p<0.0001; MSI-H, 83.3% vs 9.1%, p<0.001). Besides, ACVR2A and TGFBR2 were enriched in TGF-β pathway. Flow cytometry analysis revealed that ERBB2 S310F mutation and amplification were increased by approximate 3-fold and 3.5-fold in PD-L1 expression of cell line RBE ( p < 0.0001, respectively); by approximate 2-fold and 3-fold upregulation of PD-L1 expression in cell line HUCCT1 ( p < 0.0001, respectively). Western-blot results suggested that ERBB2 mutation/overexpression mediated PD-L1 upregulation through the RAS/ERK/c-JUN pathway. T cell cytotoxicity-mediated killing assay demonstrated that ERBB2 S310F mutation and overexpression induced the recovery of anti-cancer immunity by about 30% ( p < 0.05) both in RBE and HuCCT1 cells. Conclusions: The present study revealed two distinct genomic characteristics potentially involved in the recovery of anti-cancer immunity of intrahepatic cholangiocarcinoma patients: on one hand, co-mutation of ERBB family genes with ACVR2A or TGFBR2 was enriched in TGF-β pathway, contributing to MSI-H/TMB-H; on the other hand, ERBB2 might impact expression of PD-L1 by regulating the RAS/ERK/c-Jun pathways.