#Genome #integration of human #DNA #oncoviruses

ABSTRACT

Tumors of infectious origin globally represent 13%. Oncogenic DNA viruses such as human papillomavirus (HPV), hepatitis B virus (HBV), and Epstein-Barr virus (EBV) are responsible for approximately 60% of these tumors. These oncoviruses are extensively studied to understand their role in cancer development, particularly through viral genome integration into the host DNA. Retroviruses require integration mediated by viral integrase for persistence, whereas DNA oncoviruses do not need integration for replication; instead, integration occurs incidentally. This process often targets fragile sites in the human genome, causing structural rearrangements that disrupt genes, activate proto-oncogenes, and increase genomic instability, all contributing to tumorigenesis. Integration near promoter regions and active genes is closely linked to carcinogenesis, highlighting its importance in developing diagnostic and therapeutic strategies. This review summarizes viral integration’s role in oncogenesis, mechanisms of integration, and methods to study this process, focusing on DNA tumor viruses such as HBV, EBV, HPV, and Merkel cell polyomavirus.

Source: Journal of Virology, https://journals.asm.org/doi/full/10.1128/jvi.00562-25?af=R

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#Geographic and #age #variations in mutational processes in #colorectal #cancer

Abstract

Colorectal cancer incidence rates vary geographically and have changed over time1. Notably, in the past two decades, the incidence of early-onset colorectal cancer, affecting individuals under the age of 50 years, has doubled in many countries2-5. The reasons for this increase are unknown. Here, we investigate whether mutational processes contribute to geographic and age-related differences by examining 981 colorectal cancer genomes from 11 countries. No major differences were found in microsatellite unstable cancers, but variations in mutation burden and signatures were observed in the 802 microsatellite-stable cases. Multiple signatures, most with unknown etiologies, exhibited varying prevalence in Argentina, Brazil, Colombia, Russia, and Thailand, indicating geographically diverse levels of mutagenic exposure. Signatures SBS88 and ID18, caused by the bacteria-produced mutagen colibactin6,7, had higher mutation loads in countries with higher colorectal cancer incidence rates. SBS88 and ID18 were also enriched in early-onset colorectal cancers, being 3.3 times more common in individuals diagnosed before age 40 than in those over 70, and were imprinted early during colorectal cancer development. Colibactin exposure was further linked to APC driver mutations, with ID18 responsible for about 25% of APC driver indels in colibactin-positive cases. This study reveals geographic and age-related variations in colorectal cancer mutational processes, and suggests that early-life mutagenic exposure to colibactin-producing bacteria may contribute to the rising incidence of early-onset colorectal cancer.

Source: Nature, https://www.nature.com/articles/s41586-025-09025-8

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