The decreasedexpression of bone matrix marker genes seems to contradict previousresearch showing COL1A1 promoting breast cancer metastasisand SPP1 is involved in distant metastasis.69−71 This discrepancy,however, could originate from the short 7-day coculture, which doesnot fully mimic late-stage PCa bone metastasis. The gene discussed is SPP1; the disease is breast carcinoma.