Annual Report 2021
Molecular Genetics Unit
Haruna Takeda, Kotomi Sato
Introduction
Our group has been conducting research using in vivo screening in mice to elucidate the mechanisms of colorectal cancer progression. This year, we focused on colitis-associated and metastatic colorectal cancer (CRC). We established a screening system, identified cancer-related genes, validated the function of candidate genes, and elucidated the molecular mechanisms underlying malignant progression using omics analyses.
Cancer cells acquire genetic alterations adapted to the cancer microenvironment to promote malignant progression. In a microenvironment with chronic inflammatory stimuli, epithelial damage and repair occur repeatedly. The selection pressure and gene mutations that are selected for in such an environment have not been analyzed yet, because there are few suitable model systems. In this study, we used SB transposon screening for genome-wide identification of genes that are thought to be specifically involved in inflammation-associated cancer and performed detailed analysis of candidate genes. In addition, to elucidate what kind of selection pressure operates in the metastatic processes of CRC, we started to develop a model system using SB mice.
Research activities
Analysis of colorectal tumors formed in mice with colitis and in control mice identified 23 genes that were frequently mutated in an inflammation-related cancer-specific manner. These genes were involved in several pathways, including the p53 pathway. To elucidate the molecular mechanism, inflammatory cytokines were added to colonic epithelial organoids, and RNA-seq and ChIP-seq analyses were performed. Inflammatory stimuli induced epigenetic reprogramming in the colonic organoids to promote epithelial regeneration. At the same time, inflammatory stimuli were shown to activate the p53 pathway-mediated cell cycle arrest, indicating that this may be a selection pressure.
In order to model metastatic CRC using SB mice, we induced inflammation and fed them a high-fat diet. As a result, lymph node and liver metastases were observed at low frequency.
Education
We accepted one undergraduate and one graduate student from Kitasato University as trainees.
Future Prospects
We will perform functional validation and analysis of candidate genes that may specifically act in inflammation-associated tumorigenesis, and analyze their association with inflammatory stimuli in detail using organoids. From these analyses, we will identify novel therapeutic targets for inflammation-associated CRC and validate the efficacy of candidate compounds using mouse models.
To model metastatic CRC using SB mice, we will further optimize the conditions to increase metastatic efficiency. Tumors formed in these mice will be analyzed to identify molecules associated with metastasis and lead to the identification of new therapeutic targets.