Colorectal cancer is increasing among younger adults worldwide. According to the American Cancer Society, diagnoses among people under 50 rose by 2.9% annually between 2013 and 2022, making colorectal cancer the leading cause of cancer death in this age group.
A study published in Nature Medicine provides new clues about the biology of colorectal tumors in younger patients and how they differ from tumors diagnosed in older adults. Researchers from the Broad Institute, Dana-Farber Cancer Institute and Mass General Brigham analyzed nuclear RNA from more than 850,000 tumor and non-tumor cells taken from 189 colorectal tumors.
The patients ranged in age from 29 to over 90. Fifty-four had been diagnosed before the age of 50, while 135 were diagnosed at 50 or older. By examining which genes were active in individual cell populations, the researchers looked for changes that developed gradually with age rather than relying only on a simple under-50 versus over-50 comparison.
Among microsatellite-stable tumors, the most common form of colorectal cancer, tumors from younger patients contained a higher proportion of stromal cells than those from older patients. Stroma is supportive, vascularized connective tissue surrounding tumor cells. A greater presence of this support tissue has been associated with increased resistance to chemotherapy in several types of cancer.
The same tumors also showed greater activity from long non-coding RNAs. These molecules regulate gene activity without producing proteins, although the functions of many of them remain unclear. One of the observed patterns appeared to be linked to a greater ability of tumor cells from younger patients to migrate and invade surrounding tissues.
The study was based on observations of human tissue and does not explain why colorectal cancer cases are rising among younger people or how their tumors respond to treatment. The researchers also noted that further work is needed to clarify how the immune system’s response changes with age and how treatments may affect tumor spread.
Sources: Focus.it.