A team of investigators from the Argonne National Laboratory have identified a set of genes that might be responsible for cancer-related capillary formation (neoplastic angiogenesis.) The discovery might help to find proteins inside the endothelial cells that are responsible for reshaping these cells, and forming the capillaries:
To identify genes associated only with capillary formation, Rodi’s team grew and compared two cultures of endothelial cells. One culture was grown on plates that mimic tumor tissue and permit capillary formation. The second culture was grown on a plastic plate that does not permit capillary formation.
RNA samples were taken from both cultures at intervals of 30 minutes, 1 hour, 2 hours, 4 hours and 8 hours. RNA determines which proteins a cell produces.
“We wanted to find the proteins that are produced only when endothelial cells make a capillary,” she said. “We took all of the genes that were made on the tissue plate and subtracted those from the plastic plate. And we were left with 217.”
Each RNA sample was tested using microarray analysis at the University of Chicago. The microarrays hold 44,000 samples of known RNA coded by the human genome. A reaction on the microarray reveals which RNA is present.
Since the microarray studies only show that the potential for creating a certain protein exists, Argonne biologists needed to prove that the proteins were actually present. They looked for, and found, 16 of the morphogenesis-specific proteins in the capillaries at the 8-hour mark.
Human protein antibodies are necessary to prove that the 217 proteins are in the capillaries, but these antibodies are not easily foundâ€”only 50 are commercially available. Rodi’s team is working with another Argonne group that has developed a novel approach to express human proteins in bacteria. That group is growing more of the proteins to be used for antibody selection and testing for more of the 217 proteins in the capillaries.
The capillary research revealed a bonus insight into a still mysterious aspect of cells–their polarity. Cells are not the same all over their surface–different sections perform different tasks, such as acting as environmental sensors or making little “feet” to mediate cell movement. But researchers do not yet know all the genes involved in polarity.
The majority of the 217 proteins identified by the Argonne group perform functions associated with polarity, such as movement within the cell, long distance migration, cytoskeletal reorganization and cellular stickiness. The Argonne study revealed that more angiogenic genes–those associated with the formation of new blood vessels–are involved in polarity than previously believed, and identified a large number of novel proteins that may control the rate of blood vessel formation.