Breast cancer cells secrete different factors (parathyroid hormone-related protein, interleukins 6, 8, and 11, and prostaglandins) that stimulate the activity of osteoclasts (bone-lysing cells), leading to the subsequent degradation of bone (Guise et al, 2005; Yin et al, 2005). The gene discussed is PTHLH; the disease is breast carcinoma.