Figure 4

Proliferation and apoptosis in colorectal tumour biopsies following acute Selumetinib treatment. (a–d) Tumour biopsies from 23 colorectal cancer patients were treated with 0, 0.1 or 3 µM Selumetinib for 1 h as detailed in Fig. 2a. Immunohistochemistry was performed on formalin fixed, paraffin embedded tissue with antibodies to active caspase-3 (marker for apoptotic cells) and Ki-67 (marker for proliferating cells). The percentage of positive cells was quantified in five independent areas of tumour for each sample and each treatment point (as in Fig. 2). Significance was determined by comparing the five data points for the treated sample to the five data points for the non-treated sample using a two tailed Student’s t-test. (a and d) Graphs showing fold change in proliferation (a) and apoptosis (d) for all tumours at both doses (compared to 0 µM). *P < 0.05 when significance was determined from raw data as described above. Those tumours mutant for KRAS or BRAF are highlighted in bold (see Fig. 5). (b,c) Graphs showing the mean percentage of proliferating (b) or apoptosing (c) cells in the 5 independent fields (+/− s.e.m) for representative sensitive and resistant tumours.