Myc heterozygosity attenuates the phenotypes of APC deficiency in the small intestine

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Germline mutations in the adenomatous polyposis coli (APC) gene cause familial adenomatous polyposis, a hereditary intestinal cancer syndrome.
• The APC tumor suppressor protein plays a critical role in intestinal homeostasis.
• Previous studies indicated the proto-oncogene c-Myc is essential for phenotypes following APC loss in the mouse small intestine.

Purpose of the Study:

• To investigate the role of c-Myc dosage in APC-deficient intestinal tumorigenesis.
• To determine if modulating c-Myc levels affects Wnt target gene expression and tumor progression in the context of APC loss.
• To evaluate c-Myc as a potential therapeutic target for colorectal cancer prevention.

Main Methods:

• Utilizing a murine model with heterozygous loss of c-Myc in combination with APC loss.
• Analyzing Wnt target gene expression in APC-deficient cells with varying c-Myc levels.
• Monitoring tumor development and progression in the experimental models.

Main Results:

• Heterozygosity for Myc significantly reduced the phenotypic consequences of APC loss.
• Reduced c-Myc levels led to decreased Wnt target gene expression.
• Tumorigenesis was notably slowed in mice with reduced c-Myc levels.
• APC-deficient cells exhibited twofold higher wild-type Myc levels, highlighting Myc's critical role.

Conclusions:

• The level of Myc induced by Wnt signaling is crucial for the survival and proliferation of APC-deficient cells.
• Inhibition of c-Myc may represent a promising chemoprevention strategy for colorectal cancer.
• These findings provide a rationale for targeting the c-Myc pathway in familial adenomatous polyposis and sporadic colorectal cancer.