PURGING AND HEMATOPOIETIC PROGENITOR-CELL SELECTION BY CD34(-SEPARATION() CELL)

Tumour cell contamination of autologous peripheral blood stem cell sam ples (PBSC) and bone marrow (BM) is frequent, Enrichment of CD34(+) st em cells is a promising approach to purging tumour cells from autograf ts without damaging progenitor cells, Breast cancer cells were seeded (10(-3)-10(-7)) into mononuclear cells from G-CSF-mobilised PBSC and B M harvests from patients without breast cancer, CD34(+) cells were enr iched from mixtures either by immunomagnetic separation (Isolex-50, an d MininMACS) or by biotin-streptavidin immunoaffinity columns (Ceprate -LC), CD34(+) cell fractions were determined by FAGS, cancer cells wer e detected immunocytochemically with an anti-pancytokeratin antibody, The CD34(+) cells ci ere enriched with a median purity of 92.2% (43.5- 96.1) (n = 17) (Isolex-50), 96.5% (66.6-99.2) (n = 17) (MiniMACS) and 77.9% (31.4-93.6) (n = 15) (Ceprate-LC) from PBSC and BM harvests, The percentages of median recovery of CD34(+) cells were 30.8% (18.6-71.8 ) (Isolex-50), 69.9% (39.1-100) (MiniMACS) and 42.9% (23.7-100) (Cepra te-LC). The median tumour cell reductions in log steps were 3.7 (2.9-4 .3) (n = 13) (Isolex-50), 3.5 (2.6-4.3) (n = 13) (MiniMACS) and 1.5 (0 .9-2.9) (n = 17) (Ceprate-LC), Results were compared statistically by univariate analysis, Purity was significantly (P < 0.05) better after MiniMACS selection, Recovery rates were significantly different betwee n all devices tested, Tumour cell purging was superior after immunomag netic separation (P < 0.001), Tumour cell purging is a main objective of CD34(+) selection in the autologous setting, Our in vitro data clea rly indicate that immunomagnetic separation is more efficient in the p revention of accidental reinfusion of contaminating tumour cells compa red to immunoaffinity, However, it is not Set known if the same result s can be obtained with fresh contaminating tumour cells.