Resident Stem Cells and Renal Carcinoma

According to the cancer stem cell hypothesis tumors are maintained by a cancer stem cell population which is able to initiate and maintain tumors. Tumor-initiating stem cells display stem or progenitor cell properties such as self-renewal and capacity to re-establish tumors that recapitulate the tumor of origin. In this paper, we discuss data relative to the presence of cancer stem cells in human renal carcinoma and their possible origin from normal resident stem cells. The cancer stem cells identified in human renal carcinomas are not derived from the normal CD133+ progenitors of the kidney, but rather from a more undifferentiated population that retains a mesenchymal phenotype. This population is able to self-renewal, clonogenicity, and in vivo tumor initiation. Moreover, they retain pluripotent differentiation capability, as they can generate not only the epithelial component of the tumor, but also tumor endothelial cells. This suggests that renal cancer stem cells may contribute to the intratumor vasculogenesis

Coincubation as miR-Loading Strategy to Improve the Anti-Tumor Effect of Stem Cell-Derived EVs

Extracellular vesicles are considered a novel therapeutic tool, due to their ability to transfer their cargoes to target cells. Different strategies to directly load extracellular vesicles with RNA species have been proposed. Electroporation has been used for the loading of non-active vesicles; however, the engineering of vesicles already carrying a therapeutically active cargo is still under investigation. Here, we set up a coincubation method to increase the anti-tumor effect of extracellular vesicles isolated from human liver stem cells (HLSC-EVs). Using the coincubation protocol, vesicles were loaded with the anti-tumor miRNA-145, and their effect was evaluated on renal cancer stem cell invasion. Loaded HLSC-EVs maintained their integrity and miR transfer ability. Loaded miR-145, but not miR-145 alone, was protected by RNAse digestion, possibly due to its binding to RNA-binding proteins on HLSC-EV surface, such as Annexin A2. Moreover, miR-145 coincubated HLSC-EVs were more effective in inhibiting the invasive properties of cancer stem cells, in comparison to naïve vesicles. The protocol reported here exploits a well described property of extracellular vesicles to bind nucleic acids on their surface and protect them from degradation, in order to obtain an effective miRNA loading, thus increasing the activity of therapeutically active naïve extracellular vesicles

Role of CD133 Molecule in Wnt Response and Renal Repair

Renal repair after injury is dependent on clonal expansion of proliferation‐competent cells. In the human kidney, the expression of CD133 characterizes a population of resident scattered cells with resistance to damage and ability to proliferate. However, the biological function of the CD133 molecule is unknown. By RNA sequencing, we found that cells undergoing cisplatin damage lost the CD133 signature and acquired metanephric mesenchymal and regenerative genes such as SNAIL1, KLF4, SOX9, and WNT3. CD133 was reacquired in the recovery phase. In CD133‐Kd cells, lack of CD133 limited cell proliferation after injury and was specifically correlated with deregulation of Wnt signaling and E‐cadherin pathway. By immunoprecipitation, CD133 appeared to form a complex with E‐cadherin and β‐catenin. In parallel, CD133‐Kd cells showed lower β‐catenin levels in basal condition and after Wnt pathway activation and reduced TCF/LEF promoter activation in respect to CD133+ cells. Finally, the lack of CD133 impaired generation of nephrospheres while favoring senescence. These data indicate that CD133 may act as a permissive factor for β‐catenin signaling, preventing its degradation in the cytoplasm. Therefore, CD133 itself appears to play a functional role in renal tubular repair through maintenance of proliferative response and control of senescence

Sunitinib but not VEGF blockade inhibits cancer stem cell endothelial differentiation

Different mechanisms of angiogenesis and vasculogenesis are involved in the development of the tumor vasculature. Among them, cancer stem cells are known to contribute to tumor vasculogenesis through their direct endothelial differentiation. Here, we investigated the effect of anti-angiogenic therapy on vasculogenesis of cancer stem cells derived from breast and renal carcinomas. We found that all the anti-angiogenic approaches impaired proliferation and survival of cancer stem cells once differentiated into endothelial cells in vitro and reduced murine angiogenesis in vivo. At variance, only VEGF-receptor inhibition using the non-specific tyrosine kinase inhibitor Sunitinib or the anti-VEGF-receptor 2 neutralizing antibody, but not VEGF blockade using Bevacizumab, impaired the process of endothelial differentiation in vitro, suggesting a VEGF-independent mechanism. In addition, tyrosine kinase inhibition by Sunitinib but not VEGF blockade using the soluble VEGF trap sFlk1 inhibited the cancer stem cell-induced vasculogenesis in vivo. Accordingly, Sunitinib but not Bevacizumab inhibited the induction of hypoxia-inducible factor pathway occurring during endothelial differentiation under hypoxia. The present results highlight a differential effect of VEGF-receptor blockade versus VEGF inhibition in tumor vascularization. VEGFR blockade inhibits the process of tumor vasculogenesis occurring during tumor hypoxia whereas the effect of VEGF inhibition appears restricted to differentiated endothelial cells

extracellular vesicles from human liver stem cells inhibit renal cancer stem cell derived tumor growth in vitro and in vivo

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