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Ex vivo bone marrow purging using BPD-mediated photodynamic therapy Yip, Stephen
Abstract
Photodynamic therapy (PDT) using the second generation photosensitiser benzoporphyrin derivative monoacid ring- A (BPD, Verteporfin®) offers an attractive alternative to purging of contaminating neoplastic cells during autologous haematopoietic stem cell transplantation. Enhancement of PDT cytotoxicity was attempted using two independent approaches: combination treatment with doxorubicin (Dox) and selective protection of normal haematopoietic cells using the tetrapeptide N-AcSDKP. The murine leukaemic cell line L1210 was 45 x more susceptible to the sequenced combination regimen of 1 h 2.5 μM Dox incubation followed by PDT mediated by 5.0 ng/ml BPD and 15 J/cm² red light (Dox -> PDT) than normal murine haematopoietic cells. The significant enhancement in cytotoxicity was dependent on the concentration of BPD used as well as on the sequence of treatment. Specifically, it was observed with 5.0 ng/ml but not with 2.5 ng/ml BPD and only when Dox was used before PDT. The reverse sequence of PDT -> Dox and simultaneous Dox/PDT treatment were not associated with enhanced killing. Interestingly, L1210 cells were much more susceptible to the combination therapy than normal DBA /2 haematopoietic progenitor cells which offered interesting therapeutic implications. BPD uptake and cellular GSH content, appeared not to be responsible for the potentiation of L1210 killing in the Dox-> PDT sequence. Next, the potential of selective stem cell protection in BPD - mediated PDT was investigated. Preincubation of DBA /2 bone marrow cells with 100 nM N-AcSDKP for 1.5 h significantly protected resultant colony formation from PDT by a factor of 1.5- 2 over cells that were incubated with control peptides or with tissue culture medium. Interestingly, L1210 cells were not protected by N-AcSDKP and the control peptides. However, N-AcSDKP mediated photoprotection did not appear to extend to earlier murine haematopoietic cells and stem cells as demonstrated by the long- term bone marrow culture (LTBMC ) assay. The same findings of differential photoprotection were also demonstrated in human haematopoietic cells. The mechanism of protection appeared to be mediated by inhibition of progression to S phase of the cell cycle since depletion of cycling DBA /2 bone marrow cells with 50 μM cytosine arabinoside (ara- C) resulted in cells more tolerant to subsequent PDT cytotoxicity. The above two approaches enhanced selective BPD- mediated PDT cytotoxicity and therefore maybe of merit in the clinical use of PDT in purging.
Item Metadata
Title |
Ex vivo bone marrow purging using BPD-mediated photodynamic therapy
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1998
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Description |
Photodynamic therapy (PDT) using the second generation photosensitiser
benzoporphyrin derivative monoacid ring- A (BPD, Verteporfin®) offers an attractive
alternative to purging of contaminating neoplastic cells during autologous haematopoietic
stem cell transplantation. Enhancement of PDT cytotoxicity was attempted using two
independent approaches: combination treatment with doxorubicin (Dox) and selective
protection of normal haematopoietic cells using the tetrapeptide N-AcSDKP.
The murine leukaemic cell line L1210 was 45 x more susceptible to the sequenced
combination regimen of 1 h 2.5 μM Dox incubation followed by PDT mediated by 5.0 ng/ml
BPD and 15 J/cm² red light (Dox -> PDT) than normal murine haematopoietic cells. The
significant enhancement in cytotoxicity was dependent on the concentration of BPD used as
well as on the sequence of treatment. Specifically, it was observed with 5.0 ng/ml but not
with 2.5 ng/ml BPD and only when Dox was used before PDT. The reverse sequence of
PDT -> Dox and simultaneous Dox/PDT treatment were not associated with enhanced killing.
Interestingly, L1210 cells were much more susceptible to the combination therapy than
normal DBA /2 haematopoietic progenitor cells which offered interesting therapeutic
implications. BPD uptake and cellular GSH content, appeared not to be responsible for the
potentiation of L1210 killing in the Dox-> PDT sequence.
Next, the potential of selective stem cell protection in BPD - mediated PDT was
investigated. Preincubation of DBA /2 bone marrow cells with 100 nM N-AcSDKP for 1.5 h
significantly protected resultant colony formation from PDT by a factor of 1.5- 2 over cells
that were incubated with control peptides or with tissue culture medium. Interestingly, L1210
cells were not protected by N-AcSDKP and the control peptides. However, N-AcSDKP mediated
photoprotection did not appear to extend to earlier murine haematopoietic cells and
stem cells as demonstrated by the long- term bone marrow culture (LTBMC ) assay. The
same findings of differential photoprotection were also demonstrated in human
haematopoietic cells. The mechanism of protection appeared to be mediated by inhibition of
progression to S phase of the cell cycle since depletion of cycling DBA /2 bone marrow cells
with 50 μM cytosine arabinoside (ara- C) resulted in cells more tolerant to subsequent PDT
cytotoxicity. The above two approaches enhanced selective BPD- mediated PDT cytotoxicity
and therefore maybe of merit in the clinical use of PDT in purging.
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Extent |
11543961 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-06-25
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0099325
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1998-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.