One of mammals' winning designs for survival is pregnancy and the ability to nurture its young inside the womb to be fully adapted upon birth. However, a new study shows that there are connections between the evolution of pregnancy and the spread of cancer among placental mammals.
PLACENTAL MAMMALS AND THE RISK OF CANCER
There are three types of mammals: the marsupials (those who develop their young in 'pouches'), monotremes (mammals that lay eggs), and placental mammals -- technically known as the eutherians -- or those that develop their young in the womb and facilitates the exchange of nutrients through an organ called placenta. Most mammal species, including humans, are classified under placental mammals, and this is where the connection between pregnancy and cancer starts.
It is observed that the placenta invades the uterus in a similar way a cancer cell invades tissues in its vicinity during metastasis. However, a study discovers that the high risk for cancer -- specifically skin cancer -- among placental mammals are not observed with bovines and equines even though they are placental mammals as well.
Scientists from Yale's Systems of Biology Institute analyzed the evolution of invasibility of the connecting stromal tissue, which affects both placental and cancer invasion. In a press release issued by Yale University, Gunter Wagner, a professor of ecology and evolutionary biology at the university and the study's senior author explains, "Previous research has shown that cancer progression in humans includes the reactivation of embryonic gene expression normally controlling placenta development and immune evasion." He adds that the team would like to find out why melanoma may acquire in pigs, cows, and horses, but it will always be benign, unlike when it occurs in humans where it will almost automatically be malignant.
The study by Wagner and his team has been published on Nature Ecology & Evolution--it focuses on the differences between cows and humans in terms of the rates of cancer cell division. The team worked with in-vitro models and gene expression manipulation to be able to identify genes that can affect the vulnerability of the human stroma when being invaded by cancer cells. This methodology is spearheaded by Dr. Kshitiz, a research associate at the university's Levchenko laboratory and a professor of Biomedical Engineering.
Based on the results of the study, the researchers behind this study modified a certain group of genes in human fibroblast cells to make it similar to the genetic profile in cow cells. These modified cells, in turn, showed strong resistance to melanoma when tested. The results also showed that these differences might be caused by species differences in resistance of stromal cells against invasion.
According to the study, the high risk of cancer among humans and the high level of metastatic potential of cancer in the species could be a consequence of some evolutionary compromise to have better fetuses for a higher chance of species survival.
The researchers, on the other hand, are optimistic about the results of this study. It was able to provide an insight into how to deal with cancer and how to make human cells more resistant to it. Gene modification could certainly lead to therapies to make tumors manageable.
