Cancer is among the leading causes of morbidity and mortality in the Western world. Despite recent advances, most therapeutic approaches fail to eradicate the entire neoplastic clone. The remaining cells often develop metastasis and/or recurrences and therefore may represent attractive targets of therapy. A new exciting concept in this regard suggests that each neoplasm represents a heterogeneous population of cells that pertain to long‐term tumor growth both in vivo in the natural host and in experimental animals. This concept postulates the existence of small fractions of ‘tumor stem cells’ that exhibit a capacity for self‐renewal and unlimited growth and therefore are distinct from their progeny. Based on these hypotheses, the targeting of neoplastic stem cells is considered indispensable for eradication of the entire clone and for the development of curative treatment approaches. However, tumor stem cells often may be quiescent cells and may express a different profile of targets compared with ‘more mature’ tumor cells. Therefore, current efforts have attempted to characterize target expression profiles in cancer stem cells in various malignancies. In the this review, the authors have provided a brief summary of the current knowledge of neoplastic stem cells and the application of respective concepts in translational oncology with the ultimate objective of improving anticancer therapy. Cancer 2006. © 2006 American Cancer Society.

The immune recovery of 66 patients undergoing allogeneic stem cell transplantation with either conventional or non-myeloablative conditioning regimen was studied. Infections post-transplant were enumerated and quantitative immunoglobuilins (IgG, IgA, IgM) and lymphocyte sub-sets 3, 6 and 12 months post-transplant were measured. A significant difference was found in the immunologic recovery of non-myeloablative and conventional ASCT in the patient population. The T-helper cell reconstitution was significantly faster after NMA than conventional transplantation and the recovery of B cells was faster after conventional transplantation. Regarding immunoglobulin levels, a faster recovery of IgM levels after NMA-ASCT and a delayed recovery of IgA levels was observed in both groups. These were accompanied by a significant difference in the frequency and severity of infectious episodes.