SELECTIVE GROWTH OF FRESHLY ISOLATED HUMAN BREAST EPITHELIAL-CELLS CULTURED AT LOW CONCENTRATIONS IN THE PRESENCE OR ABSENCE OF BONE-MARROWCELLS

In this study, we show that conditions previously found to promote the selective growth of human breast epithelial cells (HBEC) in serum-fre e primary cultures established from normal or malignant tissue can be extended to cultures initiated at low seeding densities (< 5000 cells/ cm(2)). The epithelial nature of the cells produced was documented by their positive staining with antibodies specific for keratins 8, 14, a nd 18, and 2 antibodies that recognize epithelial-specific antigens (B er-EP4 and HB8630). HBEC growth was not affected, either positively or negatively, by the use of a medium containing a combination of fetal calf and horse serum, which promotes the growth of many types of strom al cells and associated hematopoietic precursors, or by the inclusion in the initial cell suspension of marrow cells at HBEC to marrow cell ratios typical of bone marrow samples from patients with metastatic br east cancer. The presence of fibroblast feeders from a variety of sour ces enhanced the growth of HBEC to different degrees. In cultures init iated with low numbers of cells obtained from samples of breast carcin oma, HBEC growth was generally reduced by comparison to cultures of no rmal HBEC. With the detection methods used, it was not possible to det ermine the extent to which this decreased growth was due to a reduced frequency of malignant HBEC with in vitro precursor activity, or the p resence of reduced numbers of residual normal HBEC precursors, or both . However, preliminary data indicate that this approach also allows th e detection of some breast carcinoma cells with proliferative ability that are present in the marrow or pleural effusions of some breast can cer patients. These studies demonstrate the feasibility of detecting n ormal and malignant HBEC with growth potential when these are cultured at low density and/or as rare contaminants of marrow cell suspensions , and provide a starting point for their further characterization.