B-cell chronic lymphocytic leukaemia cells express and release transforming growth factor-β.

Transforming growth factor-β (TGF-β) has been described as a potent inhibitor of various cell types, among others of primitive haematopoietic progenitors in vitro, and as a negative autocrine regulator of normal B lymphocyte growth and differentiation. In the present study we investigated TGF-β gene expression in peripheral blood mononuclear cells (PBMC) and in B cells from patients with B-cell chronic lymphocytic leukaemia (B-CLL) and from normal controls. Monocyte depleted B-CLL cells expressed constitutively mRNA for TGF-β1 and secreted low amounts of TGF-β activity into the culture medium. Stimulation of cells by phorbol ester noticeably enhanced mRNA levels as well as protein secretion in most cases. TGF-β activity was of the same magnitude as in normal controls. We next analysed TGF-β in highly enriched B lymphocytes from B-CLL (95-100% CD19+), and found that TGF-β secretion was up to 3 times higher than in the original PBMC population. It is discussed that B-CLL cells might escape from negative regulation by TGF-β and, on the other hand, inhibit normal haematopoietic cell proliferation and thereby achieve a growth advantage in the haematopoietic tissues

Clinical importance of P-glycoprotein-related resistance in leukemia and myelodysplastic syndromes - First experience with their reversal.

P-glycoprotein (P-gp) expression in mononuclear bone marrow cells was analyzed in 119 patients, including 60 with chronic myelogenous leukemia (CML), 48 with myelodysplastic syndromes (MDS), and 11 with acute myelogenous leukemia (AML). For P-gp measurement an immunocytological method using monoclonal antibodies C219, 4E3, and MRK 16 and the reverse transcription-polymerase chain reaction technique were applied. According to our results obtained in healthy volunteers using the immunocytological method, the limit for P-gp overexpression was set at ≥ 10% P-gp-positive mononuclear bone marrow cells and at ≥ 30% P-gp-positive mononuclear peripheral blood cells. All 42 CML patients in chronic phase had normal P-gp expression. P-gp overexpression was demonstrated in four of six patients in accelerated myelogenous blast cell phase and in four of 12 CML-BC patients. Of eight CML patients in blast crisis (BC) with normal P-gp expression, partial remission was achieved in three and minor response in five after prednisone/vindesine therapy. All four of the 12 CML-BC patients with P-gp overexpression did not respond to this therapy. Normal P-gp expression was seen in 41 (85.4%) of 48 untreated MDS patients. While P-gp overexpression did not develop during therapy in any of the myelodysplastic syndrome patients treated with low-dose ara-C alone, four of eight treated with low-dose ara-C plus GM-CSF and four of 11 treated with low-dose ara-C and IL-3 developed P-gp overexpression after therapy. Furthermore, 11 AML patients at primary diagnosis, including five AML patients with P-gp overexpression, who were treated with idarubicin, vepesid, and cytarabine V (ara-C) showed a complete remission. Additionally, one daunorubicin-cytarabine-pretreated refractory AML patient was treated with the oral form of the P-gp modulator drug dexniguldipine and achieved complete remission for a duration of 7 months. Our results suggest that in CML patients in BC, P-gp expression influences outcome after therapy. Further more, studies in a larger series of patients are necessary to prove the efficacy and toxicity of idarubicin/vepesid and cytarabine - or dexniguldipine-containing - therapy in relation to P-gp expression of AML patients