Phospholipases A 2 in ras-transformed and immortalized human mammary epithelial cells

Abstract

Phospholipase A 2 (PLA 2) activities of non-tumorigenic and tumorigenic human mammary epithelial cells, 184B5 cells (immortalized cell line from a reduction mammoplasty) and B5KTu cells (cells from a tumor induced by ras-transformed 184B5 cells), are characterized, with emphasis on lipid biomediator-related phospholipases A 2. Phospholipases A 2 associated with regulation of arachidonic acid metabolism include the high molecular mass cytosolic PLA 2 (cPLA 2) and group II PLA 2. The major PLA 2 activity in the mammary epithelial cells has the characteristics of cPLA 2; this activity is higher in the B5KTu cells. In contrast, the 184B5 and B5KTu cells have similar levels of a Ca 2+-independent, cytosolic PLA 2 activity and low levels of a particulate fraction PLA 2 activity, which does not have the properties of group II PLA 2. Thus, cPLA 2 activity is selectively elevated in the tumorigenic human mammary epithelial cells and this may result in increased generation of lipid biomediators such as arachidonic acid metabolites.