UV light and papillomaviruses promote the development of white skin cancer

UV light and papillomavirus are a dangerous combination, which leads to increased skin cancer

When it comes to skin cancer, many people think of UV rays first. These have long been considered a known risk factor for the development of skin cancer. Researchers have now found that infection with human papillomavirus in the context of UV light promotes the development of white skin cancer.

The scientists of the German Cancer Research Center (DKFZ) found in their current study that a combination of UV rays together with a simultaneous infection with human papillomaviruses favors the development of white skin cancer. The experts published a press release on the results of their study.

Skin cancer often occurs in conjunction with exposure to UV light. Physicians found that so-called white skin cancer develops more intensively when UV irradiation occurs together with infection with human papillomaviruses. (Image: fovito / fotolia.com)

Researchers investigated why the viruses are only detectable in benign cancer precursors

There has been a long-standing belief that UV rays, together with human papillomavirus infection, could promote skin cancer. This is especially true for organ transplant recipients, researchers say. The scientists of the German Cancer Research Center were able to prove for the first time in a natural system that papillomaviruses in the context of UV light can promote the development of white skin cancer. The results of the study provide an explanation as to why the viruses are no longer detectable in humans in benign precancerous lesions, but in advanced carcinoma.

Every human being eventually becomes infected with human papillomaviruses

In the course of life, every human being becomes infected with so-called skin-specific (cutaneous) human papillomaviruses (HPV). Usually the infection happens already in the early childhood. In healthy people, the immune system is able to fight off the viruses. In old age, however, the defense against the human papillomavirus decreases.

Recipients of donor organs are particularly at risk

Recipients of donor organs, whose immune system is suppressed in the long term with drugs, are particularly at risk. Affected people are up to 250 times more likely to develop white skin cancer, say the authors. In addition, the incidence of this cancer has continued to increase in recent years. UV radiation is an important known risk factor for the development of white skin cancer. This type of cancer occurs preferentially on sun-exposed parts of the body, the physicians explain further. So far, however, there has been insufficient evidence for the influence of certain types of human papillomavirus (HPV) in the development of cancer.

Tests on mice led to evidence

Scientists at the German Cancer Research Center (DKFZ) headed by Frank Rösl have now succeeded in providing proof of this connection. In their study, the researchers examined mice that usually have an infection by papillomavirus shortly after birth. Rösl and his team compared animals infected by the virus with uninfected members. The mice were then treated with a dose of UV radiation which is comparable to exposure to the sun during a holiday in Mediterranean latitudes. Finally, only the infected animals developed white skin cancer (squamous cell carcinoma).

Viruses affect the stability of the genome of their host cell

One group of the tumors was cornified, but the other group was not. So-called keratinized tumors contained large amounts of viruses, as they are also found in cancer precursors (the so-called actinic keratosis) in humans, say the experts. The upper layers of the skin grow excessively, but still remember the original structure of the skin. The results of the study showed that the viruses impair the stability of the genome of their host cell. This leads to a promotion of the accumulation of UV damage.

The tumor-promoting influence of cutaneous papilloma viruses was demonstrated for the first time

The second group of tumors studied did not contain viruses, as did advanced cancers. In the course of the investigations, however, it was also possible in such cases to detect antibodies in the blood of the animals, which pointed to a preceding virus infection. Such tumors show conspicuously often mutations in a particularly important gene for the cell (p53), the researchers explain. In humans, this gene is defective in a majority of squamous cell carcinomas. This leads to unhindered growth. "This is the first direct evidence of the tumor-promoting influence of cutaneous papillomaviruses in a natural system, which is very similar to the situation of patients," says expert Frank Rösl.

The amount of virus is related to the differentiation of the tumor

An uncontrolled growth of cells further degenerates tumors, explain the physicians. In this way it is prevented that the now superfluous for tumor growth viruses proliferate even further. The absence of viruses in advanced carcinomas has been a major argument against the involvement of cutaneous papillomaviruses in the development of cancer. "Here we show for the first time that the amount of virus is related to the differentiation of the tumor. This relationship has never been thoroughly studied in previous studies of patient biopsy, "explains lead author Daniel Hasche.

Further research is needed

The missing examinations should now be made up according to the medical profession. According to the scientists from the German Cancer Research Center, the findings are an important argument for the development of vaccines against cutaneous papillomaviruses. Such a drug would be particularly important for the recipient of organ transplants, because just these people often get white skin cancer, the authors add. (As)