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Cancer culprit hidden in mouse genes: How does MMTV affect tumorigenesis?
In the mouse world, a retrovirus called mouse mammary tumor virus (MMTV) is quietly influencing tumor formation. As a virus transmitted through breast milk, MMTV not only arouses the curiosity of current cancer researchers, but also reveals the complex relationship between cancer and viruses. This article will take a closer look at how this virus affects the formation and development of tumors in mice.
MMTV's Background and Discovery
The mouse mammary tumor virus was first discovered in 1936 by John Joseph Bittner while conducting research at the Jackson Laboratory in the United States. Bitney pointed out the existence of a "milk factor," a cancer factor that can be transmitted to pups through the breast milk of cancer-bearing mothers. Although most mammary tumors in mice are caused by MMTV, its transmission mechanism is very complex and deserves further exploration.
MMTV infection and life cycle
Multiple strains of mice carry the MMTV virus. These viruses are mainly transmitted vertically through breast milk, but can also be produced through endogenous infection. When the mother's milk enters the puppies through the digestive tract, the virus infects the macrophages and lymphocytes in the puppies' bodies, thus beginning its life cycle.
MMTV is not only considered a simple retrovirus, but recent studies have shown that it also encodes a self-regulating mRNA transporter protein, Rem, which is similar to the Rev protein of human immunodeficiency virus (HIV). Became the first composite mouse retrovirus to be documented.
Mechanisms of tumorigenesis
As a retrovirus, MMTV has the ability to insert its genome into the host genome. When the viral RNA genome is reverse transcribed into DNA, this intermediate state is called "provirus". If viral DNA is inserted near or within a host gene, it can alter the expression of that gene, thereby producing oncogenes that may induce cancer. Notably, a viral genome could lead to the development of cancer only if it altered the expression of an oncogene.
The impact of hormones on MMTV
Endogenous MMTV responds to a variety of hormones that regulate normal mammary development and lactation. Particularly during puberty, the virus begins to express its messenger RNA in estrogen-sensitive tissues, resulting in all breast cells containing active retrovirus and replicating in the genome.
The long terminal repeat (LTR) of MMTV contains a glucocorticoid response element, making it an excellent animal model system to study diseases similar to human breast cancer.
Application of MMTV in human breast cancer models
Many studies targeting breast cancer have utilized MMTV as a promoter. In these models, the MMTV promoter was used to create a mouse that develops a breast cancer-like disease. In particular, the MMTV-PyMT model has been shown to be a reliable model of breast cancer metastasis, however, polyoma-central T antigen has not been found in human breast cancer.
Conclusion
With the in-depth understanding of mouse mammary tumor virus, the scientific community has a more comprehensive understanding of the impact of viruses on tumor formation. But in this context, we can't help but wonder whether MMTV and other similar viruses can provide new inspiration and direction for human fight against cancer in future cancer research?
