THE HUMAN BREAST-CANCER CELL-LINE IIB-BR-G HAS AMPLIFIED C-MYC AND C-FOS ONCOGENES IN-VITRO AND IS SPONTANEOUSLY METASTATIC IN-VIVO

IIB-BR-G is an undifferentiated, highly heterogeneous, hormone recepto r negative human breast cancer cell line previously established in our laboratory from a patient's primary tumor. An in vitro growing cell l ine (W-BR-G) and a xenotransplanted tumor growing in nude mice (IIB-BR -G(NUDE)) were derived. To further characterize these systems, immunoc ytochemical analysis was performed for differentiation antigens (PEM 2 00 kDa, CEA, NCA 90 kDa), blood-group related antigens (Le(x), sTn), o ncogenes and tumor suppressor gene products (Her-2/neu protein, p53), metastasis-related cathepsin D and CD63/5.01 Ag, and the chemokine mon ocyte chemotactic protein 1 (MCP-I). Expression of markers was heterog eneous in these different systems. Previously reported karyotypic anal ysis has shown extensive chromosomal alterations including double min. Searching for oncogene amplification, we detected augmented copy numb er of c-myc and c-fos, the last one with two rearranged fragments. No amplification was found for c-erbB-2 in the cell line or in IIB-BR-G(N UDE), although this oncogene was amplified in the patient's primary tu mor DNA. The differences observed between the patient's tumor, the cel l line and the IIB-BR-G(NUDE) tumors are probably due to clonal expans ion of cell variants not present in the original tumor. Electron micro scopy of IIB-BR-G growing cells revealed epithelial characteristics wi th abundant dense granules, presumably secretory, distributed all over the cytoplasm and great nuclear pleomorphism. In vitro, IIB-BR-G cell s showed a significant number of invading cells by Matrigel assay. Aft er nearly 40 sequential subcutaneous passages of the original xenograf t through nude mice, 80% of recipients developed spontaneous metastase s, primarily to the lung and lymph nodes. Since this experimental mode l allowed to analyze changes produced in cancer cells from the primary tumor during adaptation to in vitro and in vivo growth, our results p rovide novel insights on the behaviour of hormone independent metastat ic breast cancer.