PHOSPHOLIPASES A(2) IN RAS-TRANSFORMED AND IMMORTALIZED HUMAN MAMMARY EPITHELIAL-CELLS

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 Ca2+-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.