Pressure in colonic tumours may increase during constipation, obstruction or peri‐operatively. Pressure enhances colonocyte adhesion by a c‐Src‐ and actin‐cytoskeleton‐dependent PKC‐independent pathway. We hypothesized that pressure activates mitogenic signals.

Methods.  Malignant colonocytes on a collagen I matrix were subjected to 15 mmHg pressure. ERK, p38, c‐Src and Akt phosphorylation and PKCα redistribution were assessed by western blot after 30 min and PKC activation by ELISA. Cells were counted after 24 h and after inhibition of each signal, tyrosine phosphorylation or actin depolymerization.

Results.  Pressure time‐dependently increased SW620 and HCT‐116 cell counts on collagen or fibronectin (P < 0.01). Pressure increased the SW620 S‐phase fraction from 28 ± 1 to 47 ± 1% (P = 0.0002). Pressure activated p38, ERK, and c‐Src (P < 0.05 each) but not Akt/PKB. Pressure decreased cytosolic PKC activity, and translocated PKCα to a membrane fraction. Blockade of p38, ERK, c‐Src or PI‐3‐K or actin depolymerization did not inhibit pressure‐stimulated proliferation. However, global tyrosine kinase blockade (genistein) and PKC blockade (calphostin C) negated pressure‐induced proliferation.

Conclusions.  Extracellular pressure stimulates cell proliferation and activates several signals. However, the mitogenic effect of pressure requires only tyrosine kinase and PKCα activation. Pressure may modulate colon cancer growth and implantation by two distinct pathways, one stimulating proliferation and the other promoting adhesion.