PIK3CA and colorectal neoplasm: However, mutations in the K-Ras, B-Raf or PIK3CA genes, common in colorectal tumours, result in structural changes in the corresponding proteins, altered effector binding and permanent activation of downstream signalling pathways, independent of EGFR blockade (McCubrey et al, 2006; Scaltriti and Baselga, 2006).