IL6 and cancer: Cancer cells, in turn, secrete prostaglandins, parathyroid hormone, parathyroid hormone-related peptide, activated vitamin D, interleukin-6 (IL-6), and TNF that may lead to an increase in RANKL expression on OBs and bone marrow stromal cells [3], which stimulates the OC number, survival, and activity, promoting osteolytic metastases.