Epigenetic "Fingerprints" Reveal Environmental Triggers Behind Rising Early-Onset Colorectal Cancer

As colorectal cancer (CRC) rates continue to climb among adults under 50, researchers have been puzzled by a persistent mystery: these patients often show no distinct genetic mutations compared to their older counterparts. A groundbreaking study published in Nature Medicine suggests the answer lies not in our DNA code itself, but in the chemical "bookmarks" left behind by our environment.

Led by José A. Seoane of the Vall d’Hebron Institute of Oncology (VHIO), the research team has successfully identified the "exposome footprint"—a collection of epigenetic signatures shaped by a lifetime of environmental and lifestyle factors—that may explain the surge in early-onset colorectal cancer (EOCRC).

Decoding the Epigenetic Book

Epigenetics refers to the biological mechanisms that regulate gene expression without altering the underlying DNA sequence. DNA methylation, a primary focus of this study, involves chemical markers that act like "post-its" in the genome, instructing the body on which genes to express and which to suppress.

"If we imagine the genome as a book, epigenetic marks don’t change the text but function like markers that indicate which chapters should be read and which should be skipped," explained Seoane. These markers are highly dynamic, shifting in response to diet, stress, and toxic exposures throughout a person’s life.

The Role of Pesticides and Lifestyle

By analyzing DNA methylation patterns from thousands of patients, the research team developed risk scores that reflect long-term environmental exposures. While the study confirmed that classic factors like smoking and diet contribute to the disease, it also uncovered a more specific culprit: the herbicide picloram.

The data revealed a striking correlation between exposure to picloram and the development of colorectal cancer before age 50. Interestingly, tumors in patients with higher exposure to the herbicide showed fewer mutations in the APC gene—a common driver of colorectal cancer. This suggests that the environment can bypass traditional genetic pathways to trigger tumor growth.

"We observed that tumors with high exposure to the pesticide had fewer mutations in the APC gene," noted Seoane. "This suggests that exposure to picloram could promote cancer development even without these classic mutations."

A Shift in Prevention

Colorectal cancer remains the world’s third most common cancer and the second leading cause of cancer-related death. In the United States, it has now become the leading cause of cancer-related mortality in men under 50.

Because picloram has been in use since the 1960s, younger generations have experienced a longer, cumulative window of potential exposure compared to those diagnosed at an older age. This "exposure window" theory provides a new lens through which scientists can view the rising incidence rates in younger demographics.

The researchers emphasize that their findings provide more than just biological insights; they offer a roadmap for public health. By demonstrating that epigenetic signatures can track environmental impact, the study paves the way for better screening, risk assessment, and targeted environmental policies.

"Our findings not only provide exposome traits that could be contributing to the development of EOCRC, but also lay a solid foundation for addressing environmental exposures to reduce risk," concluded Seoane. "This highlights the importance of promoting preventive interventions at both the individual and public policy levels."

Reference: Maas, S.C.E., et al. "Epigenetic fingerprints link early-onset colon and rectal cancer to pesticide exposure." Nature Medicine, 21 April 2026. DOI: 10.1038/s41591-026-04342-5.