Side population cells in highly enriched CD34-positive cells from peripheral blood progenitor cells identify an immature subtype of hematopoietic progenitor cells but do not predict time to engraftment in patients treated with high-dose therapy.

OBJECTIVE: A Hoechst 33342 dye efflux assay can be used to define a population of immature hematopoietic progenitor cells (HPC) that are called side population (SP) cells. Previously, SP cells examined from bone marrow (BM) and peripheral blood progenitor cells (PBPC) were found to be predominantly CD34 negative. METHODS AND RESULTS: In this study, we show that the level of CD34+ cells within the SP fraction increases from 2% in BM to 15% in mobilized PBPC. Furthermore, SP cells are found in highly enriched CD34+ cells from both BM and PBPC, and these cells define an immature phenotype of HPC. We also observed a higher level of CD133+ cells within the SPCD34+ cell population. Moreover, the frequency of long-term culture-initiating cells (LTC-IC) was markedly increased in SPCD34+ cells. To further investigate whether variations in the level of SP cells in the CD34+ cell fraction influenced short-term engraftment, we studied 20 patients with Hodgkin lymphoma that were autotransplanted with highly enriched CD34+ cells from PB. The percentage of SP cells in the PBCD34+ cell fraction was highly variable, ranging from 0.3 to 22%. No correlation was found between the content of SP cells in the autotransplanted CD34+ cells and time to short-term engraftment. CONCLUSION: SPCD34+ cells in PBPC define an immature phenotype of HPC with increased numbers of LTC-IC, and they are more frequently found in PBPC than in BM. The number of SP cells does not predict time to engraftment.

Telomerase peptide vaccination: a phase I/II study in patients with non-small cell lung cancer.

PURPOSE: A phase I/II study was conducted to investigate the safety, tolerability and clinical response to vaccination with a combination of telomerase peptides GV1001 (hTERT: 611-626) and HR2822 (hTERT: 540-548) in patients with non-small cell lung cancer. EXPERIMENTAL DESIGN: Twenty-six patients with non-small cell lung cancer received intradermal administrations of either 60 nmole (112 microg) or 300 nmole (560 microg) GV1001 in combination with 60 nM (68.4 microg) HR2822 and granulocyte macrophage-colony stimulating factor. The treatment period was 10 weeks. Booster vaccinations with 300 nM GV1001 were offered as follow-up. Monitoring of blood samples, clinical examination and radiological staging were performed regularly. Immune responses were measured as delayed-type hypersensitivity skin reaction and in vitro T cell proliferation. Bone marrow function was monitored in long time survivors. RESULTS: The treatment was well tolerated with minor side effects. No bone marrow toxicities were observed in long time survivors with immune responses. Immune responses against GV1001 were detected in 11 of 24 evaluable patients during the primary regimen and in additional two patients following booster injections. Two patients responded to HR2822. Cloned GV1001-specific CD4+ T cells displayed a Th1 cytokine profile and recognized autologous antigen presenting cells pulsed with recombinant telomerase protein. A complete tumor response was observed in one patient who developed GV1001-specific cytotoxic T cells that could be cloned from peripheral blood. CONCLUSION: The results demonstrate that GV1001 and HR2822 are immunogenic and safe to use in patients with NSCLC. Induction of GV1001-specific immune responses may result in objective tumor responses. Based on these initial encouraging results, further clinical studies of GV1001 in NSCLC patients are warranted.