Inactivation of the tumour suppressor gene adenomatous polyposis coli (APC) is the most common event in CRC (~70–80%), with co-occurring activation of oncogenic KRAS (40–50%), and/or mutations in other tumour suppressor genes (for example, PTEN or TP53) or oncogenes (for example, PIK3CA) being frequently observed (Fig. 1a)2. Here, KRAS is linked to colorectal carcinoma.