Establishment and Characterization of a Human Cell Strain, KT, with High Sensitivity to UV‐killing and to Cell Proliferation Inhibition by Interferon

We have established a human cell line, designated KT, with high susceptibility to both cell proliferation inhibition by interferon and UV‐killing, from a metastatic breast carcinoma. A tumor marker, a pregnancy‐specific glycoprotein (Schwangerschaftsprotein 1; SP1), and carcinoma characteristics compatible with ductal carcinoma of the breast were seen in KT cells by electron microscopic observation. KT cells were slightly more resistant to X‐ray‐induced toxicity than fibroblastic cells, termed KS, from the scalp of the patient. But, KT cells had lower cloning efficiency after UV irradiation than did KS cells: D 0 values of 1.5 J/m 2 and 7.2 J/m 2 , respectively. KT cells also appeared more susceptible to human interferon (HuIFN) preparations (α, β, γ and natural or recombinant) than did KS cells, as measured by cell colony formation ability, proliferation rates, and [ 3 H]deoxythymidine incorporation levels into acid‐insoluble cell materials. The sensitivity of KT cells to UV and HuIFN was greater than that of human RSa cells, a cell line with high sensitivity to both agents. KT cells had more capacity for UV‐induced DNA‐repair replication synthesis than did RSa cells, the capacity being much the same as that of KS cells. There was no significant difference in levels of antiviral activity induced by HuIFN and binding capacity for 125 I‐labeled IFN‐αA between KT and KS cells. KT cells appeared refractory to cell proliferation inhibition by tumor necrosis factor (TNF) preparations.