In vitro response of human small‐cell lung‐cancer cell lines to chemotherapeutic drugs; no correlation with clinical data

Three cell lines derived from small‐cell lung carcinoma (SCLC) tumors of patients who had no clinical response after treatment with a multi‐drug regimen were compared to 3 cell lines derived from tumors of patients who, upon treatment, showed a complete clinical response. These 2 groups of cell lines were considered to represent the in vitro counterparts of the 2 extremes of the clinical spectrum of sensitivity for chemotherapeutic drugs in small‐cell lung cancer. To assess whether the in vivo (in)sensitivity of a tumor to a certain drug regimen is retained in vitro, the cell lines were tested for drug sensitivity using the microtiter‐well tetrazolium assay and the results were compared with the in vivo data. No correlation was found. Since in vitro models using cell lines are based on the assumption that a cell line reflects the properties of the tumor from which it is derived, several additional parameters such as MAb staining against different SCLC‐associated antigens and DNA content were analyzed in the biopsies and the cell lines. The results showed that selection of discrete tumor‐cell populations in vitro occurs. Results of in vitro chemosensitivity testing for individual SCLC patients should be interpreted with caution.