Tetraploidy in cultured dermal fibroblasts from patients with heritable colon cancer

The incidence of tetraploidy in monolayer cultures of dermal fibroblasts from 40 clinically affected members from 10 families with heritable colon cancer was compared with similar cultures from 40 clinically normal volunteers with three different techniques: (1) metaphase assay (MA), (2) flow cytometry of stationary cell cultures (FCMs), and (3) flow cytometry of proliferating cell cultures (FCMd). In vitro tetraploidy was considered to be present (IVT+): (1) by MA if more than 7 per cent of metaphases were tetraploids, (2) by FCMs if more than 8 per cent of cells in stationary cultures were tetraploids (i.e. DNA index greater than 1), and (3) by FCMd of more than 8 per cent of cells in logarithmic cultures were tetraploids (i.e. DNA index greater than 2). There was excellent concordance between the three assays, which assigned all the 40 HCC patients to the IVT+ category and all the 40 normal individuals to IVT- category. This in vitro data on the incidence of IVT in clinically affected members from HCC families suggested that this putative biomarker for colon cancer proneness may ultimately be useful in identification of such increased genetic risk for colon cancer in such HCC families and further supported the hypothesis that germinal mutations for cancer proneness (detected by in vitro expression of IVT) are relevant in the development of HCC.