28.02.2013 Views

autologous blood and marrow transplantation - Blog Science ...

autologous blood and marrow transplantation - Blog Science ...

autologous blood and marrow transplantation - Blog Science ...

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

530 Chapter 10: Graft Manipulation<br />

are a number of unresolved problems in <strong>autologous</strong> <strong>transplantation</strong>. One of the most<br />

intriguing <strong>and</strong> relevant issues is the contribution of minimal residual disease to the<br />

development of relapse after high-dose chemotherapy. This refers to contaminating<br />

tumor cells within the <strong>autologous</strong> stem cell graft as well as to residual tumor cells<br />

within the patients who survive after myeloablative chemotherapy. Clinical trials 1<br />

' 2<br />

as well as gene marking studies 3,4<br />

have suggested that contaminating tumor cells<br />

within the autograft might contribute to relapse after high-dose chemotherapy.<br />

During the last 15 years, different purging strategies have been designed <strong>and</strong><br />

employed for the depletion of tumor cells from autografts. 5-7<br />

Apart from pharmacologic<br />

<strong>and</strong> other tumor cell purging techniques, in vitro manipulation of CD34 +<br />

hematopoietic progenitor cells recently has found widespread application in<br />

<strong>autologous</strong> <strong>transplantation</strong> because the procedure is simple, fast, <strong>and</strong> without any<br />

detrimental effect on graft quality. 8-10<br />

Furthermore, this approach leads to decreased<br />

infusional toxicity of the cryoprotectant dimethyl sulfoxide (DMSO) as a result of<br />

smaller infusion volume. 11<br />

Another advantage of this approach apart from the<br />

improved accessibility of CD34 cells for genetic manipulations, is the passive<br />

depletion of tumor cells. 8<br />

However, it has been demonstrated by different groups<br />

including ours that despite highly efficient CD34 selection, tumor cells can still be<br />

detected within the CD34 fraction. 1213<br />

CD34 enrichment, however, might be<br />

complicated by CD34 antigen expression on tumor cells, leading to a potential<br />

enrichment of tumor cells. Thus, it might be necessary to combine different purging<br />

techniques to obtain a tumor-free graft. Recently, efforts have been undertaken by a<br />

number of investigators to improve on CD34 selection-mediated depletion of<br />

nontarget cells (e.g., tumor cells or T cells). Different méthodologie approaches have<br />

been tried to design a more efficient purging procedure: CD34 enrichment using<br />

density Percoll gradient centrifugation, 14<br />

immunoaffinity selection followed by<br />

treatment with immunotoxins, 15<br />

complement-mediated lysis, 16<br />

immunomagnetic<br />

purging, 7<br />

<strong>and</strong> tetrameric antibody-complexes binding tumor cells <strong>and</strong> dextran. 17<br />

New<br />

strategies to enhance purging efficiency after positive selection of stem cells might<br />

rely on the functional impairment of tumor cells to engraft after <strong>transplantation</strong>, thus<br />

losing their tumorigenicity. The aim of this clinical pilot study was to evaluate a<br />

combined positive/negative purging system based on immunomagnetic cell selection<br />

with regard to feasibility <strong>and</strong> purging efficiency. An adenovirus-mediated suicide<br />

gene transfer method was also tested for purging efficiency in vitro <strong>and</strong> in vivo.<br />

MATERIALS AND METHODS<br />

Patients <strong>and</strong> treatment<br />

After patients gave informed consent, human CD34 +<br />

peripheral <strong>blood</strong><br />

progenitor cells were isolated by immunomagnetic selection from leukapheresis

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!