Breast tumor contamination of PBSC harvests: tumor depletion by positive selection of CD34(+) cells

Long-term outcome of patients with metastatic breast cancer treated with high-dose chemotherapy and transplantation of purified autologous hematopoietic stem cells

Metastatic breast cancer remains a major treatment challenge. The use of high-dose chemotherapy (HDCT) with rescue by autologous mobilized peripheral blood (MPB) is controversial, in part because of contamination of MPB by circulating tumor cells. CD34(+)Thy-1(+) selected hematopoietic stem cells (HSC) represent a graft source with a greater than 250,000-fold reduction in cancer cells. Here, we present the long-term outcome of a pilot study to determine feasibility and engraftment using HDCT and purified HSC in patients with metastatic breast cancer. Twenty-two patients who had been treated with standard chemotherapy were enrolled into a phase I/II trial between December 1996 and February 1998, and underwent HDCT followed by rescue with CD34(+)Thy-1(+) HSC isolated from autologous MPB. More than 12 years after the end of the study, 23% (5 of 22) of HSC recipients are alive, and 18% (4 of 22) are free of recurrence with normal hematopoietic function. Median progression-free survival (PFS) was 16 months, and median overall survival (OS) was 60 months. Retrospective comparison with 74 patients transplanted between February 1995 and June 1999 with the identical HDCT regimen but rescue with unmanipulated MPB indicated that 9% of patients are alive, and 7% are without disease. Median PFS was 10 months, and median OS was 28 months. In conclusion, cancer-depleted HSC following HDCT resulted in better than expected 12- to 14-year PFS and OS in a cohort of metastatic breast cancer patients. These data prompt us to look once again at purified HSC transplantation in a protocol powered to test for efficacy in advanced-stage breast cancer patients.

Chimeric protein for selective cell attachment onto cellulosic substrates

We have developed a fusion protein (CBD-LG) incorporating a cellulose-binding domain and an antibody binding domain, protein LG, to provide an adaptor molecule for cell separation with regenerated cellulose hollow fiber arrays. A single hollow fiber cell adhesion assay utilizing a CD34+ cell line, KG1a, was used to investigate whether ligand affinity interactions were strong enough for cell attachment and separation. CBD-LG efficiently captured CD34+ cells labeled with the mouse IgG2a monoclonal antibody MHCD3400. However, it was not possible to bind CD34+ cells labeled with an IgG1 antibody (HPCA-2). The low affinity of HPCA-2 for LG was overcome by secondary antibodies: KG1a cells that were dual labeled with HPCA-2 followed by rat anti-mouse IgG1 adhered inside hollow fibers coated with CBD-LG. Alternatively, immobilized rabbit polyclonal anti-mouse IgG1 captured cells labeled with HPCA-2. The development of an adaptor molecule to display recombinant domains at the surface of hollow fibers will be an effective tool to investigate cellular ligand-receptor interactions, a necessary step in the development of hollow fiber bioreactors for manufacture of human cellular products.

The importance of National Blood Foundation funding

The research award that I received from the National Blood Foundation (NBF) was very important to me early in my career for several reasons. The funding itself was important for performing the experiments proposed, and the data obtained have played a role in much of the research that has been performed in my laboratory since that time. Also, receiving the award was a very important vote of confidence by the grant review committee at an early time in my career as an independent research scientist. Finally, because it is essential that a junior faculty member secure independent research funding, receiving this award from the NBF also represented a critical step in my career. The work that was funded by the NBF has led my laboratory down many new avenues of research, all of which have been exciting and rewarding.

Impaired stem cell function of CD34+ cells selected by two different immunomagnetic beads systems

We have been investigating the hematopoietic stem cell (HSC) activity of peripheral blood-derived CD34(+) cells selected by two different laboratory immunomagnetic beads systems (MiniMACS and Isolex 50). In this study, the quality of purified CD34(+) cells was directly compared using clonal cell culture, a cobblestone area-forming cell (CAFC) assay, and an in vivo severe combined immunodeficiency (SCID)-repopulating cell (SRC) assay. It was found that CD34(+) cells selected by these two immunomagnetic methods showed a reduced yield of colony-forming cells and CAFCs compared with cells enriched by the StemSep device (a negative selection method). However, these CD34(+) cells still showed significant SRC activity, including multilineage lymphomyeloid reconstitution. The percentage of human CD45(+) cells in murine bone marrow after transplanting 5 x 10(5) CD34(+) cells selected by the Isolex 50 was significantly lower than after transplanting cells selected by the MiniMACS or the StemSep. Our findings clearly demonstrated that CD34(+) cells selected by the MiniMACS system had superior HSC functions, including SRC activity, compared with cells separated by the Isolex 50 system. More detailed functional analysis of immunomagnetically separated CD34(+) cells may provide useful knowledge for basic research on HSCs as well as for clinical HSC transplantation.

Occult tumor cells detected in autologous blood stem cell harvests have no impact on 5 year outcomes for breast cancer patients with 4-9 positive nodes treated with adjuvant high-dose therapy and stem cell transplantation

Breast cancer cells have been detected in autologous blood stem cell collections of early stage breast cancer patients, but their clinical significance is undefined. From October 1993 to August 1998, 32 consecutive Stage II breast cancer patients with 4-9-positive nodes underwent stem cell apheresis. The patients were treated with cyclophosphamide 1.75 gm/m(2), etoposide 400 mg/m(2) and cisplatin 50 mg/m(2) daily for 3 days, followed by infusion of the autologous cells. Cytospins of cells from each apheresis collections and from an aliquot of three pooled collections were examined for cytokeratin expression using an immunocytochemical assay. The cells were considered positive for tumor if at least one cell with tumor morphology stained positively for cytokeratin. Negative aliquots were confirmed with RT-PCR. Six patients (19%) had positive collections. In total, 24 patients (75%) were disease free a median of 61 (30-86) months after transplant. Eight patients relapsed at a median of 17 (8-27) months after transplant. Four of the disease-free patients and two of the relapsed patients had positive apheresis collections. There was no significant correlation between the presence of detectable tumor cells in the graft product and outcome.