Figure 1.

Growth kinetics and histological features of MC38 tumours. (A) Growth kinetics of MC38 tumours in vivo. Syngeneic C57BL/6 mice were inoculated with indicated numbers of MC38 cells by subcutaneous injection at the right hind flank (n = 10 per group). Growth curves depict the mean and standard error of the mean (SEM, error bars). (B) Study design to characterise T cell infiltration. MC38 tumours were resected 7-, 14- and 21-days post-inoculation and processed for histology, immunohistochemistry, or flow cytometry. (C) Histological features in haematoxylin and eosin (H&E) stained MC38 tumour sections. Arrows indicate characteristics of high-grade neoplasms, including hyperchromatic nuclei containing multiple, prominent nucleoli (PN; arrow, top left inset), mitotic figures (MF; arrows, bottom left and top right insets) and pleomorphism (PM; arrows, bottom right inset). (D) H&E images depicting structural changes in the outer (top row) and inner (middle row) regions of MC38 tumours during outgrowth (D7, D14 and D21) and high magnification images of adjacent stroma at the tumour margin (bottom row, ROI shown in top row). Arrows indicate stromal cells with morphological features typical of normal fibroblasts in D14 tumours (thin, wavy, spindle-shaped cells), and cancer-associated fibroblasts (CAFs) in D21 tumours (large cells with plump nuclei). Asterisks (*) denote the side of the tumour in images of the tumour margin. Scale bar dimensions are shown at the right of each row (10, 20, 50 and 100 μm).