Red Meat Implicated in Colorectal Cancer Initiation

A study published today in Cancer Discovery links a colorectal mutational signature to high intake of processed and unprocessed red meat. Previous studies in preclinical models have suggested that red meat consumption may promote the formation of carcinogenic compounds in the colon, but a direct molecular link to colorectal cancer development in patients has not been shown, explained Marios Giannakis, senior author of the study.

To identify genetic changes associated with red meat intake, Giannakis and colleagues sequenced DNA from matched normal and colorectal tumor tissues from 900 patients with colorectal cancer. Analysis of DNA sequencing data revealed the presence of several mutational signatures in normal and cancerous colon tissue, including a signature indicative of alkylation, a form of DNA damage. The alkylating signature was significantly associated with pre-diagnosis intake of processed or unprocessed red meat, but not with pre-diagnosis intake of poultry or fish or with other lifestyle factors. Red meat consumption was not associated with any of the other mutational signatures identified in this study. In line with prior studies linking red meat consumption with cancer incidence in the distal colon, Giannakis and colleagues found that normal and cancerous tissue from the distal colon had significantly higher alkylating damage than tissue from the proximal colon.

Using a predictive model, the researchers identified the KRAS and PIK3CA genes as potential targets of alkylation-induced mutation. Consistent with this prediction, they found that colorectal tumors harboring KRAS G12D, KRAS G13D, or PIK3CA E545K driver mutations, which are commonly observed in colorectal cancer, had greater enrichment of the alkylating signature compared to tumors without these mutations. The alkylating signature was also associated with patient survival: Patients whose tumors had the highest levels of alkylating damage had a 47 percent greater risk of colorectal cancer-specific death compared to patients with lower levels of damage.

"Our study identified for the first time an alkylating mutational signature in colon cells and linked it to red meat consumption and cancer driver mutations," said Giannakis. "These findings suggest that red meat consumption may cause alkylating damage that leads to cancer-causing mutations in KRAS and PIK3CA, thereby promoting colorectal cancer development. Our data further support red meat intake as a risk factor for colorectal cancer and also provide opportunities to prevent, detect, and treat this disease."