Molecular Profiling Provides Clinical Insights Into Targeted and Immunotherapies as Well as Colorectal Cancer Prognosis.

ABSTRACT

BACKGROUND & AIMS: Tumor genetic testing is indispensable in the management of primary and metastatic colorectal cancer (CRC), yet the indications for genomics-guided precision medicine and immunotherapy must be better understood and defined. METHODS: We prospectively sequenced tumors from 869 Chinese patients with CRC by a large panel and evaluated the clinical significance of single-gene somatic mutations and co-occurring events in metastatic CRC, as well as their functional effects and tumorigenic mechanisms. We systematically assessed the heterogeneity of the tumor immune microenvironment in different genomic contexts through the combined analysis of Immunoscore, multiplex immunostaining, whole-exome sequencing, transcriptome, and single-cell sequencing. RESULTS: Single-gene somatic mutations in BRAF or RBM10 were associated with shorter progression-free survival in patients with metastatic CRC. Functional studies suggested RBM10 acts as a tumor suppressor in CRC development. Co-mutations of KRAS/AMER1 or KRAS/APC were enriched in the metastatic cohort, which had poor progression-free survival and did not benefit from bevacizumab due to accelerated drug metabolism. Forty patients (4.6%) carried pathogenic or likely pathogenic germline alterations in the DNA damage repair pathway and 37.5% of these tumors had secondary-hit events with loss of heterozygosity or biallelic alterations. A high tumor insertion or deletion burden with high microsatellite instability suggested immunogenicity with numerous activated tumor-infiltrating lymphocytes, whereas polymerase epsilon exonuclease mutation with ultrahigh tumor mutation burden indicated a relatively quiescent immunophenotype. The heterogeneous genomic-immunologic interactions were reflected in the divergent neoantigen presentation and depletion, immune checkpoint expression, PD-1/PD-L1 interaction, and T-cell responsiveness to pembrolizumab. CONCLUSIONS: Our integrated analysis provides insights into CRC prognostic stratification, drug response, and personalized genomics-guided targeted and immunotherapies.