Effect of cytotoxic chemotherapy on stroma and tumor cells in tissues from lung cancer patients. Tumor tissue slices from 16 patients with primary lung cancer were incubated with or without cisplatinum for 72 hours, then fixed in formalin and analyzed for proliferation and cell death using KI67 and TUNEL immunohistochemistry. (a) Representative examples of KI67 and TUNEL stained sections from tissues with cellular response (left panel) and non-response (right panel). Scale bar, 50 μm. (b) Percentage of KI67 (left histograms) and TUNEL (right histograms) positive cells of both the tumor (upper panel) and the stromal compartment (middle panel) was assessed using a ×40 objective. Three to 7 randomly selected fields were examined for each section. The correlation of tumor and stromal response to cisplatinum regarding changes in proliferation and cell death is shown in the lower panels of the figure. Response to cisplatinum was defined as a reduction of KI67 positive cells by more than 10% or induction of TUNEL positive cells by more than 20%.