International Journal of Cell Cloning, Vol 7, 223-231, Copyright © 1989 by AlphaMed Press
Limiting dilution analysis for detection of residual leukemic cells after bone marrow combined decontamination with mafosfamide followed by merocyanine-540-mediated photosensitization
A Porcellini, MT Rossi, A Manna, G Sparaventi and C Pazzaglia
Servizio di Ematologia, Medicina II, Centro Trapianto Midollo Osseo, Cremona, Italy.
Human acute myelogenous or lymphoblastic leukemia cells of the K-562 and
CCRF-SB lines were mixed with an excess of normal human bone marrow cells
to simulate a leukemia remission marrow. The cell mixtures were then
incubated in vitro with mafosfamide (AZ) followed by the photoreactive dye
merocyanine-540 (MC). Treated cells (1 x 10(4] were seeded in microwell
plates, and increasing numbers of the line used to contaminate the normal
marrow were added. Treatment with AZ alone produced total elimination
(i.e., 6 logs) of CCRF-SB cells, while addition of merocyanine-540
increased the cloning efficiency from 22% to 24.4%. After treatment of the
K-562-contaminated cell mixtures with AZ, nearly 1.6 logs of K-562 acute
myelogenous blasts were still present, whereas AZ purging followed by
MC-mediated photosensitization resulted in 100% elimination of clonogenic
cells. Moreover, the combined treatment caused an increase of the cloning
efficiency from 37.3% to 62%, clearly indicating that cleansing by the two
agents combined was more effective than treatment with one agent alone.
