Good and poor mobilizing patients differ in mobilized CD34+ cell adhesion molecule profiles

CD44, Hyaluronan, the Hematopoietic Stem Cell, and Leukemia-Initiating Cells

CD44 is an adhesion molecule that varies in size due to glycosylation and insertion of so-called variant exon products. The CD44 standard isoform (CD44s) is highly expressed in many cells and most abundantly in cells of the hematopoietic system, whereas expression of CD44 variant isoforms (CD44v) is more restricted. CD44s and CD44v are known as stem cell markers, first described for hematopoietic stem cells and later on confirmed for cancer- and leukemia-initiating cells. Importantly, both abundantly expressed CD44s as well as CD44v actively contribute to the maintenance of stem cell features, like generating and embedding in a niche, homing into the niche, maintenance of quiescence, and relative apoptosis resistance. This is surprising, as CD44 is not a master stem cell gene. I here will discuss that the functional contribution of CD44 relies on its particular communication skills with neighboring molecules, adjacent cells and, last not least, the surrounding matrix. In fact, it is the interaction of the hyaluronan receptor CD44 with its prime ligand, which strongly assists stem cells to fulfill their special and demanding tasks. Recent fundamental progress in support of this “old” hypothesis, which may soon pave the way for most promising new therapeutics, is presented for both hematopoietic stem cell and leukemia-initiating cell. The contribution of CD44 to the generation of a stem cell niche, to homing of stem cells in their niche, to stem cell quiescence and apoptosis resistance will be in focus.

Risk factors for a poor hematopoietic stem cell mobilization

Poor mobilization is an important problem in autologous stem cell transplantation. We retrospectively reviewed the data of 165 mobilized patients to identify possible risk factors for a poor stem cell mobilization. 27 patients (16.4%) were categorized as poorly mobilized. The poor mobilization ratio differed according to diagnosis (lymphoma: 25.4%, acute leukemia: 15.4%, amyloidosis: 14.3%, and multiple myeloma: 9.6%). Being diagnosed as lymphoma (odds ratio [OR]=6.02, p=0.001), advanced age (OR=1.05, p=0.007) and increased weight (OR=1.03, p=0.03) were found as possible risk factors. Being diagnosed as lymphoma was shown to be the most important risk factor for a poor mobilization. Leukapheresis staff should be aware of the increased risk of a poor mobilization in lymphoma patients and remobilization methods should be considered from the beginning.

Predictive factors for inadequate stem cell mobilization in Chinese patients with NHL and HL: 14-year experience of a single-center study

BACKGROUND

Factors affecting progenitor cell mobilization in patients with non-Hodgkin's lymphoma (NHL) and Hodgkin's lymphoma (HL) are incompletely understood. The aim of this retrospective study was to determine which factors are crucial for effective mobilization and collection of autologous peripheral blood stem cells (PBSC) prior to transplantation in Chinese patients.

PATIENTS AND METHODS

A total of 239 patients with lymphoma (198 NHL and 41 HL patients) underwent PBSC collection after mobilization with granulocyte-colony-stimulating factor (G-CSF) or G-CSF plus chemotherapy priming.

RESULTS

Patient characteristics at diagnosis and transplant, including low Eastern Cooperative Oncology Group score (P = 0.013), lack of extranodal invasion (P = 0.034), previously administered radiotherapy regimens (P = 0.040), treatment with platinum prior to mobilization (P = 0.042), previous chemotherapy regimens (P = 0.001) and cycles (P < 0.001), and chemotherapy regimens (P < 0.001) were statistically significant for successful mobilization in multivariate analysis. Premobilization factors, including previous radiotherapy (P = 0.009), previous chemotherapy regimens (P = 0.043) and cycles (P = 0.039), low platelet count prior to mobilization (P = 0.042), and lower CD34+ cells in peripheral blood (PB) (P = 0.050) or bone marrow (BM) (P = 0.007) were considered possibly predictive of poor mobilization. We found the patients who had chemosensitive lymphoma had worse progress-free survival (PFS) than the patients with initial treatment and high risks (P = 0.017).

CONCLUSION

Our analysis showed that high amounts of chemotherapy, radiotherapy, low platelet count, chemosensitive recurrent patients, combination chemotherapy plus G-CSF and low CD34+ cells in BM prior to mobilization could emerged as important predictive factors for mobilization failure in Chinese patients with NHL and HL.

Adhesion of human haematopoietic (CD34+) stem cells to human liver compartments is integrin and CD44 dependent and modulated by CXCR3 and CXCR4

BACKGROUND/AIMS

Haematopoietic stem cells (HSC) have previously been shown in some studies to migrate to damaged and diseased liver where a small proportion will engraft. Such cells can promote liver repair in rodent models of liver injury and lead to improved liver function in uncontrolled clinical studies. In order to maximize the engraftment of cells for clinical applications it is necessary to understand the molecular mechanisms that regulate stem cell recruitment and retention. Our aim therefore was to determine which factors where involved in adhesion of circulating HSC to liver endothelium and sequestration around epithelial cells within the liver.

METHODS

We examined the ability of CD34+ populations from peripheral and mobilized blood and the CD34-expressing cell line KG1a to bind to human hepatic sinusoidal endothelial (HSEC) and biliary epithelial cells (BEC) in vitro.

RESULTS

We report that all CD34(+) populations express alpha4beta1, beta2 integrins and CD44. Liver tissue sections and primary liver cells expressed the corresponding ligands VCAM-1/fibronectin, ICAM-1 and CD44. Pertussis toxin was shown to decrease binding of CD34(+) cells and the cells migrated to CXCR3 and CXCR4 ligands.

CONCLUSIONS

CD34(+) populations use alpha4beta1, beta2 integrins and CD44 receptors to bind to the ligands VCAM-1/fibronectin, ICAM-1, and hyaluronic acid expressed on sinusoidal vessels in tissue sections and to primary human HSEC. Binding to BEC was mediated by the interaction of beta1 and beta2 integrins with VCAM-1 and ICAM-1 respectively. A role for chemokines is supported by our finding that pertussis toxin inhibits CD34(+) cell adhesion to BEC and HSEC and by the ability of CD34(+) cells to migrate to CXCR3 and CXCR4 ligands.

Hematopoietic progenitor cells (HPC) from mobilized peripheral blood display enhanced migration and marrow homing compared to steady-state bone marrow HPC

OBJECTIVE

Faster engraftment of G-CSF-mobilized peripheral blood (MPB) transplants compared to steady-state bone marrow (ssBM) is well documented and clinically relevant. A number of different factors likely contribute to this outcome. In the present study we explored whether independent of cell number there are intrinsic differences in the efficiency of progenitor cell homing to marrow between MPB and ssBM.

METHODS

Mobilization was achieved by continuous infusion of G-CSF alone or in combination with other mobilizing agents. In vivo homing assays, in vitro migration assays, gene expression analysis, and flow cytometry were utilized to compare homing-related in vivo and in vitro properties of MPB and ssBM HPC.

RESULTS

Marrow homing of murine MPB HPC, generated by different mobilizing schemes, was reproducibly significantly superior to that of ssBM, in lethally irradiated as well as in nonirradiated hosts. This phenotype was independent of MMP9, selectins, and beta2- and alpha4-integrins. Superior homing was also observed for human MPB HPC transplanted into NOD/SCIDbeta2microglobulin(-/-) recipients. Inhibition of HPC migration abrogated the homing advantage of MPB but did not affect homing of ssBM HPC, whereas enhancement of motility by CD26 inhibition improved marrow homing only of ssBM HPC. Enhanced SDF-1-dependent chemotaxis and low CD26 expression on MPB HPC were identified as potential contributing factors. Significant contributions of the putative alternative SDF-1 receptor, RDC1, were unlikely based on gene expression data.

CONCLUSION

The data suggest increased motility as a converging endpoint of complex changes seen in MPB HPC which is likely responsible for their favorable homing.