Endothelial progenitor cells (EPCs) are mobilized from either bone marrow or arterial walls to restore blood perfusion to ischemic organs and establish the vascular network within growing tumors [1]. The Ca2+ machinery plays a key role in EPC activation and might serve a molecular target for novel therapies of highly angiogenic tumors, such as renal cell carcinoma (RCC) [1]. The Ca2+ toolkit is remodelled in EPCs isolated from RCC patients (RCC-EPCs) as respect to healthy donors [2]. The present study was undertaken to evaluate for the first time the functional properties of EPCs isolated from tumor patients by focusing on RCC-EPCs. We extended our analysis at microscopic level by monitoring the sub-cellular structure of RCC-EPCs relative to their Ca2+ signalling fingerprint. Our results showed a striking functional and ultrastructural difference between RCC-EPCs and their normal counterparts, which might be the basis for designing novel, more specific anti-angiogenic treatments
