Clinical use of streptolysin-O to facilitate antisense oligodeoxyribonucleotide delivery for purging autografts in chronic myeloid leukaemia

Antisense oligodeoxyribonucleotides (ODN) targeted against the breakpoint in BCR-ABL mRNA will specifically decrease BCR-ABL mRNA, provided cells are first permeabilised with streptolysin-O (SL-O). We used 18-mer chimeric methylphosphonodiester: phosphodiester linked (4-9-4) ODN complementary to 9 bases either side of the BCR-ABL junction to purge harvests ex vivo in three CML patients who remained completely Ph positive after multiple chemotherapy courses. After CD34+ cell selection and SL-O permeabilisation, harvests were purged with 20 microM ODN. After purging, all individual CFU-GM colonies grown from the two b3a2 breakpoint cases remained positive for BCR-ABL mRNA. In contrast, all 24 colonies grown from the b2a2 breakpoint case were BCR-ABL mRNA negative. Patients were conditioned with busulphan 16 mg/kg. The initial post-transplant course was uneventful, although the time to return to 0.5 x 10(9)/l neutrophils was slow at 25-51 days. Both chronic phase patients remain in haematological remission at +724 and +610 days, although each has cytogenetic evidence of relapse. The b2a2 accelerated phase patient died of myeloid blast transformation at day +91. The present SL-O-facilitated ODN purging strategy appears to be without significant toxicity, and offers considerable improvements in ODN delivery to the cytosol.

Molecular status of individual CFU-GM colonies derived from chemotherapy-mobilised peripheral blood stem cells in chronic myeloid leukaemia

Following chemotherapy in chronic myeloid leukaemia (CML), some peripheral blood (PB) cells may be Philadelphia (Ph) chromosome negative. The BCR-ABL mRNA status of residual Ph+ progenitors is not known. We examined the BCR-ABL mRNA status of individual colony-forming-unit granulocyte-macrophage (CFU-GM) colonies derived from PB harvested following chemotherapy. Seven patients were treated with 200 mg/m2/day cytarabine and 20 mg/m2/day Idarubicin and followed by Lenograstim. PB collections commenced daily when the white blood cell count reached 0.6 x 10(9)/l and continued until at least 5 x 10(8)/kg nucleated cells were obtained. CD34+ cells, Ph status, and CFU-GM were estimated at each harvest. For each patient, up to 24 individual CFU-GM colonies were analysed for BCR-ABL status. Two cases were BCR-ABL negative on all colonies and completely Ph-, and another case was BCR-ABL positive in all colonies and completely Ph+. In contrast, in two patients all colonies were BCR-ABL negative, despite virtually complete Ph+ metaphases. The final assessible case had five of nine BCR-ABL negative colonies, despite 94% Ph+ metaphases. After chemotherapy priming, the PB may contain Ph+ CFU-GM that do not express BCR-ABL.