Isolation, purification, culture and characterisation of myoepithelial cells from normal and neoplastic canine mammary glands using a magnetic-activated cell sorting separation system.

Mammary cancer is the most common malignant neoplasm in the bitch and, in contrast to human breast cancer, high frequency of these tumours showing myoepithelial (ME) cell proliferation. Both in vitro and in vivo human studies have shown the importante role of ME cells in breast cancer progression, suppressing tumour growth and invasion. Some canine mammary carcinomas had been cultured, but never isolated and cultured ME cells. Our aims were to isolate a purified population of ME cells using the magnetic-activated cell sorting (MACS) separation system, and to culture and to characterize both morphologically and immohophenotypically isolated ME cells from neoplastic and normal canine mammay glands. Monodispersed cells from 5 tumours and 3 normal mammary glands were treated with the anti-Thy1 antibody and the MACS® method. Isolated cells from 4 tumours: cell lines CmME-K1 (complex carcinoma), CmME-K2 (simple tubulopapillary carcinoma), CmME-K3 (carcinoma in benign tumour) and CmME-K4 (carcinoma in benign tumour) and 2 normal glands: cell lines CmME-N1 and CmME-N2 were cultured in supplemented DMEM/F12 media during 40 days. The purity of ME cells was >90% from both neoplastic and normal mammary tissue. ME cell lines had a heterogeneous pattern concerning morphology, growth and immunocytochemical expression of cytokeratins. Cell lines from normal glands maintained their morphology during culture compared with cell lines from tumours. Cell lines from normal glands and carcinomas in benign tumour grew slower than cells from complex and simple carcinomas. This methodology opens up the possibility of in vitro studies of the tumour suppressor or tumour progressor role of ME cells in canine mammary cancer