Prostate cancer specific integrin αvβ3 modulates bone metastatic growth and tissue remodeling

The management of pain and morbidity due to the spreading and growth of cancer within bone remains to be a paramount problem in clinical care. Cancer cells actively transform bone, however, the molecular requirements and mechanisms of this process remain unclear. This study shows that functional modulation of the alpha v beta 3 integrin receptor in prostate cancer cells is required for progression within bone and determines tumor-induced bone tissue transformation. Using histology and quantitative microCT analysis, we show that avb3 integrin is required not only for tumor growth within the bone but for tumor-induced bone gain, a response resembling bone lesions in prostate cancer patients. Expression of normal, fully functional avb3 enabled tumor growth in bone ( incidence: 4/4), whereas avb3 (-), inactive or constitutively active mutants of alpha v beta 3 did not ( incidence: 0/4, 0/6 and 1/7, respectively) within a 35-day-period. This response appeared to be bone-specific in comparison to the subcutis where tumor incidence was greater than 60% for all groups. Interestingly, bone residing prostate cancer cells expressing normal or dis-regulated alpha v beta 3 ( either inactive of constitutively active), but not those lacking beta 3 promoted bone gain or afforded protection from bone loss in the presence or absence of histologically detectable tumor 35 days following implantation. As bone is replete with ligands for beta 3 integrin, we next demonstrated that avb3 integrin activation on tumor cells is essential for the recognition of key bone-specific matrix proteins. As a result, prostate cancer cells expressing fully functional but not dis-regulated avb3 integrin are able to control their own adherence and migration to bone matrix, functions that facilitate tumor growth and control bone lesion development.