ELEVATED LEVELS OF ANNEXIN-I PROTEIN IN-VITRO AND IN-VIVO IN RAT AND HUMAN MAMMARY ADENOCARCINOMA

Annexin I is a phospholipid and actin binding protein which may play a role in signal transduction to the cytoskeleton. Previous work report ed the differential expression of annexin I mRNA among rat adenocarcin oma cell lines of various metastatic potential (MTLn3, MTLn2, MTC.4: h ighest to lowest, respectively) (Pencil et al. 1993, Breast Cancer Res Treat, 25, 165-74). This relationship has been extended to the protei n level in in vitro cultures using Western blotting and flow cytometry . Annexin I protein levels in MTLn3 cells are 3- to 5-fold higher than in MTC. 4 cells. The weakly metastatic cell line MTLn2 shows levels 1 .5- to 2.5-fold higher than MTC.4. In vivo tumors were produced by inj ecting 1 x 10(6) cells into mammary fat pads of syngeneic rats and nec ropsies were performed 40 days later. Semiquantitative immunohistochem ical color image analysis was performed using a polyclonal rat annexin I specific antibody. Annexin I protein expression was highest in lung metastases of MTLn3, at 8-fold the levels observed in the MTC.4 prima ry tumors. MTLn3 cells in the primary tumor had an annexin I specific optical density 3-fold higher than that of cells in the MTC.4 primary tumor. MTLn2 primary tumors had an annexin I specific optical density 1.5-fold higher than MTC.4. A proportion of human mammary adenocarcino mas also have positive annexin I immunoreactivity, often with more uni form annexin I staining in the lymph node metastases. These results su ggest that there may be survival advantages for nascent metastatic cel ls with high annexin I levels. (C) 1998 Rapid Science Ltd.