The Role of the Different CD34 Epitopes in Detection and Positive Selection of CD34+ Bone Marrow and Peripheral Blood Stem Cells

Positive selection of CD34⁺ cells is an attractive approach to reduce tumour cell contamination in bone marrow (BM) and peripheral blood progenitor cell (PBPC) autografts in malignancies not expressing CD34. All current selection methods use monoclonal antibodies (MoAbs) specific for the class I or class II CD34 epitopes, while for detection most investigators use class III MoAbs. Since the distribution of the different CD34 epitopes on haematopoietic progenitors differs, we studied their significance in CD34⁺ selection procedures. Testing MoAbs against class I, II and III CD34 epitopes on normal BM we observed that ± 23% of class III positive cells was class I negative. A higher expression of the class III epitope compared with classes I or II was observed on the KG1 cell line, whereas no differences in binding capability were found. The class III epitope anti-CD34, 561, was compared with the class I epitope anti-CD34, BI-3C5, both coupled to M450 Dynabeads. The yield of CD34⁺ cells obtained with the 561 beads was 1.7% of the mononuclear cells versus 0.95% using the class I epitope, a 1.95-fold increase (1.3–2.7), whereas the purity was similar (96% in both cases). The absolute number of CD34⁺ cells was therefore twofold higher after 561 selection, including cells with a more mature phenotype. In single cell assay comparable numbers of highly proliferative progenitors but higher numbers of differentiated colonies per phenotypic subfraction were measured. In conclusion, M450 beads coated with the 561 anti-class III CD34 epitope are more efficient in isolating CD34⁺ cells from bone marrow, probably due to a broader distribution of the class III epitope.     

Maturation of dendritic cells is a prerequisite for inducing immune responses in advanced melanoma patients.

PURPOSE: We have investigated the capacity of immature and mature monocyte-derived DCs pulsed with melanoma-associated peptides (gp100 and tyrosinase) to induce a primary cytotoxic T-lymphocyte response in vivo. EXPERIMENTAL DESIGN: Advanced HLA-A2.1(+) melanoma patients were vaccinated with peptide- and keyhole limpet hemocyanin (KLH)-pulsed DCs, either immature (9 patients) or matured by monocyte-conditioned medium/tumor necrosis factor alpha/prostaglandin E(2) (10 patients). RESULTS: All patients vaccinated with mature DCs showed a pronounced proliferative T-cell and humoral response against KLH. By contrast, KLH responses were absent in most of the patients vaccinated with immature DCs. Delayed-type hypersensitivity (DTH) reactions against antigen-pulsed DCs were only observed in patients vaccinated with mature DCs and not in patients vaccinated with immature DCs. MHC-peptide tetramer staining of DTH-derived T cells revealed the presence of specific T cells recognizing the melanoma-associated peptides in 1 patient. In a second patient, DTH-derived T cells showed specific lysis of tumor cells expressing the antigens used for DC pulsing. Only patients vaccinated with mature DCs showed objective clinical responses. Interestingly, both patients with long-term progression-free survival (22 and >40 months) were both vaccinated with mature DCs and demonstrated antigen-specific T-cell reactivity of DTH-derived T cells. CONCLUSIONS: We conclude that mature DC are superior to immature DC in the induction of immunological responses in melanoma patients, which may translate into improved clinical results.     

Role of radiography, MRI and FDG-PET/CT in diagnosing, staging and therapeutical evaluation of patients with multiple myeloma

Multiple myeloma is a malignant B-cell neoplasm that involves the skeleton in approximately 80% of the patients. With an average age of 60 years and a 5-years survival of nearly 45% Brenner et al. (Blood 111:2516–2520, 35) the onset is to be classified as occurring still early in life while the disease can be very aggressive and debilitating. In the last decades, several new imaging techniques were introduced. The aim of this review is to compare the different techniques such as radiographic survey, multidetector computed tomography (MDCT), whole-body magnetic resonance imaging (WB-MRI), fluorodeoxyglucose positron emission tomography- (FDG-PET) with or without computed tomography (CT), and ^99mTc-methoxyisobutylisonitrile (^99mTc-MIBI) scintigraphy. We conclude that both FDG-PET in combination with low-dose CT and whole-body MRI are more sensitive than skeleton X-ray in screening and diagnosing multiple myeloma. WB-MRI allows assessment of bone marrow involvement but cannot detect bone destruction, which might result in overstaging. Moreover, WB-MRI is less suitable in assessing response to therapy than FDG-PET. The combination of PET with low-dose CT can replace the golden standard, conventional skeletal survey. In the clinical practise, this will result in upstaging, due to the higher sensitivity.     

CD34 selections from myeloma peripheral blood cell autografts contain residual tumour cells due to impurity, not to CD34+ myeloma cells

Malignant cells in haemopoietic autografts can contribute to post-transplant relapse. Engraftment of myeloma patients with CD34⁺ peripheral blood progenitors selected from total autografts reduces the number of tumour cells infused by 2.7–4.5 logs. Residual tumour cells detected in CD34⁺ selected cells may be due to selection impurity or the existence of malignant CD34⁺ progenitors. In three patients we evaluated the CD34 purity and tumour load of total autografts, CD34⁺ progenitors selected with immunomagnetic beads and highly purified CD34⁺ progenitors obtained in two rounds of selection (combining magnetic with flow cytometry activated cell sorting) to determine the cause of residual tumour cells in CD34 selections. Using allele-specific oligonucleotides (ASO) complementary to the unique Ig heavy chain sequence (CDRIII region) of the malignant clone, semi-quantitative ASO-PCR was capable of detecting one malignant cell in 10⁴–10⁵ normal white blood cells. Selection of CD34⁺ cells from bone marrow (BM) with approximately 20% malignant plasma cells resulted in a 1.4 log reduction of tumour burden. Using two-colour flow-cytometry we observed CD34^?, BB4⁺ malignant plasma cells contaminating this CD34 selection. Prior to sorting, peripheral blood cell autografts (PBCA) contained approximately 0.1% malignant cells. Selection of >99% pure CD34⁺ cells using immunomagnetic beads (Dynal) resulted in an approximate 2 log reduction of malignant cells, but residual tumour cells were still detectable. ASO-PCR detected no malignant cells in >99.9% pure CD34⁺ peripheral blood progenitors obtained with two rounds of selection (combining magnetic with flow cytometry activated cell sorting). We conclude that CD34⁺ malignant cells are not detectable in myeloma PBCA and that residual tumour cells in CD34 selections are due to contaminating CD34-negative cells.     

Oral fluoropyrimidines registered for the treatment of metastatic colorectal carcinoma: a possible gain

Up until now the standard treatment for metastasized colorectal carcinoma has been fluorouracil (5-FU) in combination with folonic acid in low doses administered intravenously, even after the recent registration of a number of new intravenously administered cytostatics, such as irinotecan and oxaliplatin. Meanwhile there are oral alternatives for 5-FU: capecitabine and the combination of tegafur and uracil with folonic acid. In four randomised studies it was shown that these drugs were globally just as effective as the combination of 5-FU with folonic acid (in accordance with the 'Mayo Clinic' scheme). There was no survival advantage for the oral drugs compared to 5-FU with folonic acid. Compared to 5-FU and folonic acid the use of capecitabine or tegafur-uracil-folonic acid was associated with less toxic effects; however, there were differences in the side effects profile between the oral drugs and 5-FU (more hand-foot syndrome for capecitabine and less (symptomatic) leucopenia for tegafur-uracil-folonic acid). An examination of the serious side effects (grade 3 and 4) revealed that the total incidence was generally comparable. These data, together with the ease of oral administration, form the basis for the registration of capecitabine and tegafur-uracil-folonic acid. The definitive place of these drugs in the treatment of metastasized colorectal carcinoma is not yet clear.