Ancient Viral DNA: An Unexpected Driver of Cancer
Nearly 9% of the human genome comes from ancient retroviruses that infected our ancestors millions of years ago. Although most of these viral remnants can no longer produce viruses, some still influence how human genes function. Researchers have now found that certain fragments can become active in multiple cancers, switching on genes that help tumors grow and survive.
How Ancient Viral DNA Influences Cancer
Normally, most ancient viral DNA remains tightly packed and inactive within our genome. However, some fragments can act as enhancers, regulatory sequences that help activate genes. When these regions become accessible, they can contribute to abnormal gene activity.
Researchers identified one fragment, known as LTR10, that was active across several cancer types, including colorectal, lung, stomach, and prostate cancer. Their findings suggest that cancer-related proteins, including AP1 and MAPK, can help expose these DNA sequences, allowing them to activate genes associated with cancer.
LTR10's Role in Colorectal Cancer
Further investigation revealed that LTR10 fragments can activate multiple cancer-related genes in colorectal cancer cells. One of these genes, XRCC4, helps cancer cells survive radiation therapy.
In experiments involving mice, radiation therapy slowed colorectal tumor growth. However, when researchers removed the LTR10 sequence responsible for activating XRCC4, the treatment became more effective. This finding suggests that targeting the DNA sequences that regulate cancer-related genes could offer a different approach to cancer treatment.
What This Means For Future Treatments
These findings reveal an unexpected connection between ancient viral DNA and cancer development. Instead of targeting individual genes or proteins, future treatments could focus on the regulatory DNA sequences that activate several cancer-related genes at once. This approach may offer a way to interfere with multiple processes that support tumor growth and survival.
The results involving XRCC4 are particularly promising. Since this gene helps cancer cells resist radiation therapy, disrupting the DNA sequence responsible for activating it made radiation treatment more effective in mouse studies. Researchers could eventually explore whether targeting similar regulatory sequences might improve treatment responses in other cancers.
However, this strategy remains a potential direction for future research rather than an established cancer treatment. Scientists still need to determine how safely and effectively these sequences can be targeted in patients. Ultimately, the findings highlight how ancient viral DNA can have lasting effects on human health, revealing a previously overlooked mechanism that could help guide the development of new cancer therapies.
References
DNA from ancient retrovirus helps cancer grow. (2024, September 6). Cancer.Gov; Cancer.gov. https://www.cancer.gov/news-events/cancer-currents-blog/2024/ancient-retrovirus-dna-ltr10-cancer
