Primary human tumor cells and continuous cell lines differ in clonal growth in soft agar

This study is a sequel in our continuing efforts to improve the colony forming efficiency of the Human Tumor Colony Assay. We have previously reported that the use of culture media supplemented with rat red blood cells and a low oxygen environment resulted in notable improvements in the clonal growth of three different tumor cell lines (colon, breast and melanoma). We now report, however, that the application of these methods to cells from 18 different samples of primary human tumors resulted in no improvements in growth. Our results suggest that caution must be exercised in extrapolating results obtained from the use of homogeneous cell lines to that of cells from human solid tumors.