However, during necrotic and apoptotic cell death, CK18 and other cytokeratins are released into the blood in either their intact or their caspase-cleaved forms, where they remain relatively stable in the circulation of patients with cancer.35 CK18 is proposed as a surrogate measure of disease burden/drug-induced cell death,36,37 and it would appear that rising levels in this patient population is indicative of impending disease progression. The gene discussed is KRT18; the disease is cancer.