Comparative Analysis of Cytokines Released by Bone Marrow Stromal Cells from Normal Donors and B-cell Chronic Lymphocytic Leukemic Patients

Abstract

We studied the production of cytokines (G-CSF, GM-CSF, IL-6, LIF and IL-10) by bone marrow stromal cells of five untreated patients with B-CLL, in Rai stage 0,1 and II, and of 8 healthy subjects. The production of G-CSF, GM-CSF, LIF and IL-10 did not differ significantly between controls and B-CLL patients. However, the ability of stromal cells to release IL-6 in response to LPS was decreased in all patients: 36 5 ng/ml versus 123 47 ng/ml for normal controls (P < 0.004). Moreover, a soluble activity that inhibited hematopoietic colony formation was detected in B-CLL stromal cell conditioned media. Some potential inhibitors were envisaged and the results indicated an increased production of TGF-P by B-CLL stromal cells compared to normal stromal cells (respectively 53 10 versus 15 4 ng/ml, P < 0.03). The reduced capacity of B-CLL stromal cells to produce IL-6 was associated with this excessive release of TGF-bT; indeed, addition of anti-TGF-bT neutralizing antibody to B-CLL stromal cells, before LPS stimulation, totally normalized the production of IL-6.

TGF-bT and IL-6 were also measured in serum samples from normal subjects and B-CLL patients. No significant difference was seen in the production of total TGF-bT (bioactive and latent forms) between normal and B-CLL sera but the mean level of bioactive protein in B-CLL sera was increased in comparison with normal sera (1.74 0.44 versus 0.67 0.2 ng/ml, P < 0.04). Furthermore, low serum levels of IL-6 were found in normal and B-CLL sera but detectable levels of IL-6 were less frequent in B-CLL sera. In conclusion, in B-CLL, decreased IL-6 production by stromal cells and inhibiting activity on hematopoietic progenitors are attributable to increased production of TGF-bT. This increased amount of TGF-bT is also seen in sera of B-CLL patients. Our report supports the hypothesis that overproduction of TGF-bT could play a pathogenic role in some manifestations of this disease such as bone marrow failure, deficiency in platelet and Ig production.

Key Words:

• cytokines
• stromal cells
• B-CLL
• TGF-bT
• IL-6