STIP1 and renal cell carcinoma: In our previous proteome analysis of the total cellular protein from RCC tumor cells, STIP1 protein was found to be 4-fold more abundant in the bone-seeking cells than in the control parental cells [12], and STIP1 was observed to be translocated to the cell surface and secreted out of cells [13, 14], which may mediate extracellular tumor-niche interactions.