Cell communication in breast cancer.

Direct intercellular communication is the transfer of ions and small molecules between cells in contact. Cells derived from human breast tissue have been examined to determine their pattern of direct communication, which was measured by the 3H-uridine nucleotide transfer method. The behaviour of mammary epithelium from normal and pathological sources has been compared with that of malignant mammary epithelium. Normal human mammary fibroblasts and epithelium demonstrate selectivity in direct communication. Thus although both transfer nucleotide to and from their own cell type, they do not transfer nucleotide between one another in heterologous co-culture. Further study of a variety of non-human fibroblasts and epithelium showed that cells may be functionally subdivided into selective communicators, non-selective communicators, and non-communicators. None of the malignant human breast cells examined showed selectivity in communication. Thus both primary cultures and established lines were either non-communicators or non-selective communicators. This loss of selectivity could favour the metastasis of malignant cells, enabling them either to ignore inhibitory growth control signals or alternatively to receive stimulatory signals from abnormal sources.