TNFSF11 and cancer: Here, parathyroid hormone related protein, derived from cancer cells, stimulates the production of RANKL which is associated with increased osteoclast maturation and bone resorption, overcoming attempts at osteoblastic bone formation and repair.7,13 In some cancer types (eg, prostate cancer), an osteoblastic phenotype predominates where cancer cells secrete factors that stimulate aberrant osteoblastic bone formation.7 While osteolytic metastases predominate in breast cancer, mixed osteolytic and osteoblastic lesions are frequently seen.