First, a secondary improvement of the cancer stem cell sorting protocol is desirable to have reproducibility of the results obtained. For this, the use of a kit that removes debris from tumor xenografts would be a plus for the optimization of sorting. Identification of a marker for anti-angiogenic resistant cancer stem cells in clear cell renal cancer holds promise for targeting this population for tumor aggressiveness in therapy. For this, it is necessary to confirm and approve the results obtained in this project by characterizing troponin T 2 in cancer stem cells by in situ immunolabeling on frozen tumor xenograft sections, using a triple labeling targeting CXCR4, CD105 and TNNT2. Furthermore, it is desirable to look for a correlation of the expression of this protein with xenograft passages to see if it is responsible for the aggressiveness of cancer stem cells and subsequently determine its role, after creating knock out and knock in mouse models.