JAK2 and cancer: Since JAKs are upstream of STATs and therefore might also interfere with other mechanisms involved in cancer progression this could explain a perceived improved efficacy of JAK inhibitors and the popularity of Tofacitinib (JAK1/JAK3 inhibitor) and Baricitinib (JAK1/JAK2 inhibitor) for the treatment of inflammatory conditions (4, 8, 59, 60, 82, 253, 254).