Faculty Bibliography

BACKGROUND:In myeloma patients resistance to both melphalan- and doxorubicin-containing regimens has been related to very short survival (approximately 6 months). The development of effective regimens combined with a low toxicity rate is mandatory in this patient subgroup. METHODS:Fourteen resistant myeloma patients were treated with cyclophosphamide (a total of 3.6 g/m2 was delivered in 2 doses on days 1 and 3) and prednisone (2 mg/kg, days 1-4) every month for 4 cycles. G-CSF support was administered to reduce myelosuppression. RESULTS:This combination was well tolerated. Granulocyte levels fell below 0.1 x 10(9)/L in all patients after a median of 9 days (range 8-11), followed by recovery to 0.5 x 10(9)/L after a median of 12 days from the start of treatment (range 10-13 days). Platelets never fell below 50 x 10(9)/L. All patients were treated on an outpatient basis and only 2 required hospitalization for major complications (pneumonia and heart failure). Response to cyclophosphamide was observed in 6/14 patients: 2 achieved complete remission, 4 showed a 50% or greater reduction of the M-component. Five patients are still in remission after 2, 6, 7, 9 and 10 months; 1 relapsed after 10 months. All patients except one are alive 4-16 months from the start of treatment. CONCLUSIONS:This schedule may represent a new approach for resistant myeloma, and its very low toxicity allows it to be delivered on an outpatient basis.

T cells in multiple myeloma (MM) patients are highly susceptible to activation with the anti-CD3 monoclonal antibody (mAb) OKT3. When short-term OKT3 stimulation is carried out on bone marrow mononuclear cells (BMMC), large numbers of CD3+ CD25+ HLA-DR+ cells are rapidly generated and autologous malignant plasma cells are killed. OKT3 may thus be exploited in autologous bone marrow transplantation (ABMT) to purge residual plasma cells and simultaneously activate T cells to induce graft-versus-leukemia-like (GVL-like) activity upon reinfusion. However, the possible impact of ex-vivo short-term OKT3 stimulation on haematological recovery is unknown. The aim of this work was to investigate the effect of OKT3 stimulation in vitro on autologous haemopoietic progenitor cells (HPC) of MM patients. Colony formation by granulocyte-macrophage progenitor cells (granulocyte-macrophage colony-forming units, CFU-GM) was highly suppressed, although supernatants of OKT3-activated T cells contained up to 2,500 pg/ml of granulocyte-macrophage colony-stimulating factor (GM-CSF). T cell depletion completely prevented this suppression. Neutralizing antibodies against TNF-alpha, TNF-beta and IFN-gamma (which are also produced by OKT3-activated MM T cells) did not prevent it, and Transwell cultures showed that cell-to-cell contact was the main mechanism involved. OKT3-activated T cells also suppressed erythroid burst-forming units (BFU-E) and CFU-GM generation from HPC responsible for long-term maintenance of in vitro myelopoiesis. When tested on normal allogeneic BM, MM supernatants of OKT3-stimulated BMMC partially suppressed the generation of day 7 CFU-GM, but had no effect on day 14 CFU-GM. These data indicate that short-term stimulation of BMMC with OKT3 can be used to generate anti-tumour effector T cells for autologous adoptive immunotherapy. It is not a feasable approach for ex-vivo purging and activation procedures in ABMT because of its potent inhibition of autologous haemopoiesis.