Introduction: Adipose-derived mesenchymal stem cells (A-MSCs) are known to be a preeminent contributor to tumor microenvironments. Their role in renal cell carcinoma (RCC) has not been entirely investigated. This study aimed to clarify the significance of A-MSCs in RCC.
Methods: Human A-MSCs were isolated from the perirenal fat in RCC patients (RCC-MSC) and kidney transplantation donors (Donor-MSC) for use as controls. Several RCC cell lines were co-cultured with the A-MSCs, then analyzed for their migration and invasive ability. Molecular pathways activated in the RCC-MSCs and isolated RCC cultures were assessed. Beta-catenin in perirenal fat from surgical specimens from RCC patients was stained by immunohistochemistry (IHC).
Results: RCC-MSCs expressed higher levels of mRNAs encoding Hes1, Hey1, and Twist, higher protein levels of beta-catenin, and reduced protein levels of phospho-Akt (Ser473) and phospho-p38 MAPK relative to Donor-MSCs (Figure 1A and B). These results suggest that RCC-MSC stemness is reduced compared with Donor-MSCs in terms of stemness associated molecular pathways. This finding was confirmed by the aldehyde dehydrogenase enzymatic activity (ALDH) assays, in which fewer RCC-MSCs were ALDH+ than Donor-MSCs (Figure 1C). We next analyzed cell function by co-culturing with RCC cell lines. Tumor cell migration was significantly elevated in RCC-MSC cultures compared with RCC cell lines cultured alone (Figure 2A and B). Pathway screening using the RCC cell line revealed elevated urokinase-type plasminogen activator (uPA) mRNA expression in RCC-MSCs than cultured alone (Figure 2C). In RCC surgical specimens, IHC of perirenal stromal tissue for beta-catenin showed a high positive correlation with tumor aggressiveness (Figure 2D).
Conclusions: Co-culturing of RCC-MSCs with RCC cell lines exacerbated tumor invasiveness. Interaction between A-MSCs and tumors may promote A-MSC differentiation from pluripotent stem cells, and facilitate RCC migration and invasion by increasing expression of uPA in tumor cells.