Functional Characterization of Age-Dependent p16 Epimutation Reveals Biological Drivers and Therapeutic Targets for Colorectal Cancer

Authors

Li Yang
Xiaomin Chen
Christy Lee
Jiejun Shi
Emily B Lawrence
Lanjing Zhang
Yumei Li
Nan Gao
Sung Yun Jung
Chad J Creighton
Jingyi Jessica Li
Ya Cui
Sumimasa Arimura
Yunping Lei
Wei Li
Lanlan Shen

Publication Date

5-4-2023

Journal

Journal of Experimental & Clinical Cancer Research

DOI

10.1186/s13046-023-02689-y

PMID

37143122

PMCID

PMC10157929

Published Open-Access

no

Keywords

Humans, Animals, Mice, Epigenesis, Genetic, Carcinogenesis, Cell Transformation, Neoplastic, Colonic Neoplasms, DNA Methylation, Colorectal Neoplasms, Tumor Microenvironment, B7-H1 Antigen, Colon cancer, p16 epimutation, Tumor microenvironment, Epigenetic and immunotherapy

Abstract

BACKGROUND: Methylation of the p16 promoter resulting in epigenetic gene silencing-known as p16 epimutation-is frequently found in human colorectal cancer and is also common in normal-appearing colonic mucosa of aging individuals. Thus, to improve clinical care of colorectal cancer (CRC) patients, we explored the role of age-related p16 epimutation in intestinal tumorigenesis.

METHODS: We established a mouse model that replicates two common genetic and epigenetic events observed in human CRCs: Apc mutation and p16 epimutation. We conducted long-term survival and histological analysis of tumor development and progression. Colonic epithelial cells and tumors were collected from mice and analyzed by RNA sequencing (RNA-seq), quantitative PCR, and flow cytometry. We performed single-cell RNA sequencing (scRNA-seq) to characterize tumor-infiltrating immune cells throughout tumor progression. We tested whether anti-PD-L1 immunotherapy affects overall survival of tumor-bearing mice and whether inhibition of both epigenetic regulation and immune checkpoint is more efficacious.

RESULTS: Mice carrying combined Apc mutation and p16 epimutation had significantly shortened survival and increased tumor growth compared to those with Apc mutation only. Intriguingly, colon tumors with p16 epimutation exhibited an activated interferon pathway, increased expression of programmed death-ligand 1 (Pdl1), and enhanced infiltration of immune cells. scRNA-seq further revealed the presence of Foxp3

CONCLUSIONS: Our study demonstrated that age-dependent p16 epimutation creates a permissive microenvironment for malignant transformation of polyps to colon cancer. Our findings provide a mechanistic rationale for future targeted therapy in patients with p16 epimutation.

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