A scanning electron micrograph of ovarian cancer cells forming a small tumor. Image courtesy of the University of Gothenburg.
Potential New Way to Suppress Tumor Growth Discovered
Researchers at the University of California, San Diego School of Medicine, with colleagues at the University of Rochester Medical Center, have identified a new mechanism that appears to suppress tumor growth, opening the possibility of developing a new class of anti-cancer drugs.
Writing in this week’s online Early Edition of the Proceedings of the National Academy of Sciences (PNAS), Willis X. Li, PhD, a professor in the Department of Medicine at UC San Diego, reports that a particular form of a signaling protein called STAT5A stabilizes the formation of heterochromatin (a form of chromosomal DNA), which in turn suppresses the ability of cancer cells to issue instructions to multiply and grow.
Specifically, Li and colleagues found that the unphosphorylated form of STAT promotes and stabilizes heterochromatin, which keeps DNA tightly packaged and inaccessible to transcription factors. “Therefore, genes ‘buried’ in heterochromatin are not expressed,” explained Li.
Phosphorylation is a fundamental cellular function in which a phosphate group is added to a protein or molecule, causing it to turn it on or off or to alter its function. An unphosphorylated STAT lacks this phosphate group.