Minimal residual disease in bone marrow transplant recipients with chronic myeloid leukemia.

Bone marrow samples of 70 transplant recipients with CML were studied by Southern blot analysis and RT-PCR using a two-step procedure with nested primers. Twenty-two patients were studied once and 48 were assessed on multiple occasions. All patients remained in a hematological remission during the study. The time of follow-up after the transplant ranged from 2 to 144 months with a median of 42 months. Thirty-nine patients (56%) were negative by RT-PCR and Southern blot studies at the time of their last evaluation. The proportion of RT-PCR negative patients increased with the duration of follow-up after the transplant; 36% of patients were RT-PCR negative after 1 year compared with 60% after 2 years and 78% after > or = 5 years. Patients maintained on immunosuppression had a higher probability of remaining RT-PCR positive. Age, sex, time from diagnosis to BMT, as well as acute and chronic GVHD did not influence the RT-PCR status. The majority of patients studied on multiple occasions demonstrated a stable RT-PCR and Southern blot pattern. Some showed uni- or multi-directional transitions. However, none of the patients studied progressed to a hematological relapse. RT-PCR studies on colonies grown from RT-PCR positive. Southern blot negative patients confirmed that some of the clonogenic progenitors are able to produce BCR/ABL transcripts.

The preliminary observation on immunosuppressive effect of norcantharidin in mice.

Norcantharidin (NCTD) is a synthetic analog of cantharidin. It has potent antitumor properties without obvious side effect that Cantharidin has on urinary organs. It has been reported that NCTD is an immunological stimulator to NK, LAK, neutrophil and lymphocyte. In our experiment, however, we observed that NCTD can markedly inhibit lymphocyte proliferation stimulated by mitogen ConA or LPS in vitro, and the mixed lymphocyte reaction (MLR) of mice, in a dose-related manner. This occurred even when the drug was added 40 hours (for lymphocyte proliferation) or 72 hours (for MLR) after the cultures were initiated. On the other hand, NCTD has no effect on inactive lymphocytes that were cultured as control in medium without mitogens, suggesting that NCTD selectively acts on activated lymphocyte.

Monoclonal antibody 55 (CD10) and complement used for purging autologous bone marrow in common acute lymphoblastic leukemia.

A CD10 monoclonal antibody 55 (McAb55) was intended for purging residual common acute lymphoblastic leukemia antigen (CALLA) positive leukemic cells from autotransplants of common acute lymphoblastic leukemia (C-ALL) patients. It was found that after two rounds of McAb55 and complement treatment, 4-5 logs of CALLA+ cells were removed from bone marrow detected by clonogenic assay. The standardization of separation, purgation and preservation of bone marrow for C-ALL patients' autotransplants was then set as follows: Following the carboxymethyl starch sedimentation and Ficoll-Hypaque gradient separation, the isolated mononuclear cells (MNCs) were treated with McAb55 and complement twice and kept in room temperature for 48-72 hours prior to infusion. This procedure resulted in the removal of more than 99% of CALLA+ cells, recovery of 10-30% MNCs, and leaving the hematopoiesis stem cells intact. After the intensive cytoreductive therapy, 4 patients with C-ALL received the purged autotransplants giving timely recovery of the hematopoietic function. The patients were all remaining in remission status for more than 40-250 days so far.