IL1R1 forms a tertiary complex with the IL-1 receptor accessory protein (IL1RaP, also called IL1R3), facilitating positive signaling, and recruiting downstream cell signaling proteins; however, IL1R1 has an antagonistic ligand IL1RN, also known as IL1RA, that is overexpressed in several cancers, including multiple myeloma, leukemia, cervical, ovarian, colorectal, pancreatic, and breast cancer [17,18,19,20,21,22], but it is downregulated in others [23]. Here, IL1RAP is linked to plasma cell myeloma.