Co-localization of PCNA, VCAM-1 and caspase-3 with nestin in xenografts derived from human anaplastic astrocytoma and glioblastoma multiforme tumor spheres

The cancer stem cell hypothesis proposes that tumors contain a small subset of cancer cells, the cancer stem cells, which constitute a reservoir of self-sustaining cells with the exclusive ability to self-renew and maintain the tumor. Markers that define cancer stem cells that are capable of recapitulating brain tumors as xenografts in mice has not been described. We investigated the relationship between expression of nestin and that of PCNA, VCAM-1 and caspase-3 in the xenografts developed from human anaplastic astrocytoma and glioblastoma tumor-derived spheres in the brain of nude mouse. Xenografts obtained from astrocytoma tumor stem cells (ATSC) and glioblastoma tumor stem cells (GTSC) have showed a large number of cells positive for both PCNA and the nestin, demonstrating that nestin expressing cells have a high rate of proliferation. Xenografts from GTSC showed heterogeneous staining pattern with cells that express both nestin and VCAM-1, whereas others cells remained complete negative. In this case it was noticed that most tumor cells with large or multinucleated nuclei coexpress nestin and VCAM-1. In xenografts from ATSC most cells positive for nestin express VCAM-1 and in this case the two proteins appear to occupy the same cytoplasmic region. Both GTSC and ATSC derived xenografts showed cells positive for both caspase-3 and for nestin detected mainly as single cells and as cell clusters located near or around a blood vessel.