Researchers at the San Francisco VA Medical Center report that they have found a potential molecular cause for the aggressive growth and spread of human head and neck squamous cell carcinoma, a highly malignant form of cancer with a very high death rate.
The discovery could potentially lead to new treatments as well, say the researchers.
Their key finding is the triple interaction between three players: CD44, a surface receptor molecule that plays an important role in a variety of cellular functions; hyaluronan (HA), a complex carbohydrate found in the connective tissues between cells; and LARG, a signal activator found in tumor cells.
That interaction apparently initiates two molecular pathways that simultaneously cause tumor cell growth and tumor cell migration, says lead author Lilly Bourguignon, PhD, a research career scientist at SFVAMC and a professor of medicine at the University of California, San Francisco.
The study results are reported in the current on-line "In Press" section of the Journal of Biological Chemistry.
Working with human cancer cells in culture, Bourguignon and her team found that HA mediates the interaction between CD44 and LARG in a way that stimulates a molecular pathway called RhoA. Through a series of complex steps, the RhoA pathway causes the tumor cell's cytoskeleton - the structure that maintains the cell's shape - to reorganize in a way that causes tumor cells to migrate to other sites in the body, resulting in cancer metastasis.
At the same time, the HA-mediated CD44/LARG complex also binds with epidermal growth factor receptor (EGFR), located on the tumor cell's surface, which sets off a second molecular pathway called Ras. In turn, the Ras pathway promotes tumor cell growth.
The result, according to Bourguignon, is an aggressive, fast-growing, and invasive cancer. "The combination of RhoA and Ras pathway activation is deadly," she says.
Read more at Steve Tokar, UCSF News Services