Bioassay of transforming growth factor-beta activity in acidic protein extracts from primary breast cancer specimens.

Acidic protein extracts have been made from breast tumour specimens, collected at the time of primary surgery. The extracts were partially purified by gel filtration and then tested for transforming growth factor-beta activity in a reproducible cell 3H-thymidine incorporation assay. Purified TGF-beta causes a reproducible increase in NRK colony formation and inhibits incorporation of 3H-thymidine by mink lung cells. However, some of the breast cancer extracts were stimulatory in the mink lung lung assay implying that a mitogenic factor like epidermal growth factor (EGF) was co-purified. Fourteen out of thirty extracts were scored positive for TGF-beta in the NRK colony forming assay and these tumours presented at an earlier clinical stage and were predominantly well differentiated.