Sun protection also prevents cancer


Many people may think that sun protection is just for beauty, but this is not the case. Excessive ultraviolet rays will not only darken our skin, cause sun spots, accelerate wrinkles, and increase the risk of skin cancer. In fact, ultraviolet rays can even cause bone marrow damage.

A research paper just published in the authoritative academic journal "Nature" found that the harm of ultraviolet rays can affect cells in the bone marrow, eventually becoming the driver of an acute leukemia.

Cancer does not appear all at once. The development of many tumors takes a long time. At first, precancerous cells (premalignant cells) may appear in a certain site, and certain environmental pressures will promote the growth of certain cells carrying specific mutations. , further transforms into cancer cells through clonal expansion and leads to the spread of the disease.

In this new study, researchers from the Broad Institute, Memorial Sloan Kettering Cancer Center, Harvard Medical School and other institutions collaborated to focus on how ultraviolet rays induce the development of precancerous cells. malignant transformation.

They used a series of genomic analysis methods such as whole-genome sequencing and single-cell transcriptomics to examine the cancer development process in 16 patients. These patients all suffer from a rare form of leukemia called blastic plasmacytoid dendritic cell neoplasm (BPDCN).

BPDCN is an aggressive tumor that develops from immature immune cells, plasmacytoid dendritic cells (pDC). It is often diagnosed by the appearance of malignant cells on the skin, sometimes involving the bone marrow, and eventually develops into a systemic disease. disease.

Typical BPDCN patients have malignant cell infiltration in skin tumors. The bone marrow may have normal hematopoietic function or may be infected by malignant cells.

Pathological cells were detected in the skin of these patients, but only some showed involvement of the bone marrow. However, the researchers' analysis showed that BPDCN actually originated from the bone marrow and came from clonal hematopoietic precursor cells in the bone marrow.

Clonal hematopoiesis does not immediately cause symptoms of blood diseases, but it is an important foreshadowing of leukemia. This study found that precancerous cells move from the bone marrow to the skin and eventually develop into malignant cells on the skin, and that ultraviolet rays play a significant role in the development stage of the disease.

They observed that tumors on patients' skin first developed in areas that were frequently exposed to the sun, such as the top of their heads, and that these tumors carried new mutations induced by ultraviolet radiation. The results of tumor phylogenetic reconstruction show that ultraviolet damage occurs before the malignant transformation of precancerous cells.

As a kind of immune cell, pDC cells will move to the skin injury during skin wound healing, anti-virus, sunburn and other processes. Like other cells, normal pDCs are very sensitive to UV-induced death. But for BPDCN patients, pDCs, which are precancerous cells, usually have a mutation in the TET22 gene, allowing them to continue to survive after being exposed to ultraviolet light. However, at the same time, these cells will also acquire new mutations related to malignant tumors, such as CDK2NA or RAS mutations, induced by ultraviolet radiation. Eventually, malignant cells emerge that carry more mutations and can continue to spread, including back to the bone marrow.

Taken together, these results indicate that the influence of ultraviolet radiation on precancerous cells in the skin is an important step in the pathogenesis of BPDCN tumors. Although BPDCN is a relatively rare type of leukemia, the study authors also mentioned in the paper that the model of how precancerous cells in the blood system undergo early evolution due to the influence of ultraviolet light may also be applicable to some other types of leukemia.