IL6 and neoplasm: blood biomarkers related to i) hypoxia: Osteopontin (OPN), carbonic anhydrase IX (CA-9), and lactate dehydrogenase (LDH); ii) inflammation - interleukin 6 (IL-6), IL-8, and C-reactive protein (CRP), and α-2-macroglobulin (α-2M); and iii) tumor load: Carcinoembryonic antigen (CEA) and cytokeratin fragment (CYFRA 21-1); 4.