Kristina Hoelig

Kinetics of CXCR-4 and adhesion molecule expression during autologous stem cell mobilisation with G-CSF plus AMD3100 in patients with multiple myeloma

AMD3100, a competitive antagonist of CXCR-4, disrupts the binding of its ligand, stromal cell-derived factor-1 (SDF-1), and facilitates stem cell mobilisation in patients with haematological malignancies. This study investigated the differential kinetics of CXCR-4 and adhesion molecule expression and their impact on stem cell yield during mobilisation with granulocyte-colony stimulating factor (G-CSF) (days 1–4) followed by AMD3100 in 10 patients with multiple myeloma. A four-colour flow cytometry-based determination of CXCR-4, VLA-4, l-selectin, PECAM, LFA-1 and CD44 expression on CD34+ cells and measurement of SDF-1 concentration were performed at different time points. After G-CSF alone, CXCR-4 expression on patients’ blood and marrow CD34+ cells was significantly lower than in the healthy controls (p < 0.001), but allowed no prediction of stem cell yield. Except in the single poorly mobilising patient, AMD3100 led to a further significant decrease of CXCR4 (p = 0.001), which inversely correlated with the CD34+ counts in the blood (p = 0.005). SDF-1 level in patients’ marrow was positively correlated with CXCR-4 expression on CD34+ cells (p = 0.011). It is interesting to note that the expression of adhesion molecules remained unaffected by AMD3100 administration. Further studies will define the possible prognostic role of AMD3100 mediated changes in CXCR-4 expression for the prediction of stem cell yield attainable with this new mobilisation regimen.

HPC enumeration with the Sysmex XE-2100 can guide further flow cytometric CD34 measurements and timing of leukaphereses

BACKGROUND The aim of this study was to evaluate whether HPC counts measured with the hematology analyzer can predict CD34+ levels in peripheral blood and in the apheresis product, as detected by standard flow cytometry. The main focus was the evaluation of HPC counts in poor mobilizers. METHODS Progenitor cell quantification was performed measuring HPC counts provided by the Sysmex XE-2100 hematology analyzer and CD34+ counts obtained in parallel by flow cytometry. Peripheral blood of patients who had received chemotherapy and G-CSF (142 measurements) and healthy donors mobilized with G-CSF alone (106 measurements) was investigated HPC counts in peripheral blood were also correlated with apheresis yield. RESULTS HPC counts were significantly higher than CD34+ counts (3.5 fold inpatients and 1.7 fold in healthy donors, p= 0.0015). Our data indicate that HPC counts < or = 10/microL in pretreated patients predict a low probability of adequate CD34+ counts in peripheral blood and yields < 2 x 10(6)/kg in subsequent aphereses. Furthermore, repetitive low HPC enumerations in an individual were followed by insufficientCD34+ counts in peripheral blood or aphereses in 81% of investigations. In healthy donors low HPC counts (< or = 10/microL; 12/106 measurements) did not exclusively predict low CD34+ counts (median 23/microL). DISCUSSION HPC counts can be used to schedule the start of CD34+ measurements(threshold > 10 HPC/microL) in patients mobilized after chemotherapy for autologous donation. Thus, expensive and time-consuming CD34+ enumerations can perhaps be minimized HPC measurements cannot completely replace flow cytometric CD34+ enumeration. In particular healthy stem-cell donors should be monitored with both methods to exclude false negative HPC measurements.

VACCINATION OF HORMONE-REFRACTORY PROSTATE CANCER PATIENTS WITH PEPTIDE COCKTAIL-LOADED DENDRITIC CELLS: RESULTS OF A PHASE I CLINICAL TRIAL

2551 Background: For patients with hormone-refractory prostate cancer (HRPC) treatment options are limited. Immunotherapies based on dendritic cells (DCs) might represent promising alternatives. In a Phase I clinical trial, we evaluated the safety and feasibility of a vaccination with monocyte-derived DCs loaded with a cocktail consisting of HLA-A*0201-restricted peptides derived from prostate cancer-associated antigens (PSA, PSMA, survivin, prostein, trp-p8). METHODS Eight HRPC patients were enrolled in this study (Table). Each patient underwent two leukaphereses, for the isolation of monocytes and subsequent generation of mature DCs. Patients received a total of four vaccinations each with peptide cocktail-loaded DCs at a dose of 1 x 107 cells both intradermally and intravenously every other week. Clinical response was monitored by the determination of the PSA level. The induction of a peptide-specific T-cell response was assessed by ELISPOT analysis. RESULTS Apart from local erythema and edema at the site of intradermal administration no side effects were noted. Four of eight patients showed a temporary PSA decline. One patient displayed a partial response with a PSA decrease > 50% for seven weeks and further stabilization for five weeks. Stable PSA values or decelerated PSA increases were observed in the three remaining patients. In ELISPOT analyses, three of four PSA responders also showed antigen-specific CD8+ T-cell activation against prostein, survivin and PSMA. CONCLUSIONS The described protocol represents a safe and feasible concept for the induction of clinical and immunological responses. The application of a peptide cocktail derived from different antigens as a novel treatment modality is supposed to allow for the genetic and biologic heterogeneity of PCa. [Table: see text] [Table: see text].