An ATP-activated channel is involved in mitogenic stimulation of human T lymphocytes

We investigated the effect of pharmacologic modulation of the ATP receptor on intracellular ion changes and proliferative response of human peripheral blood lymphocytes (PBLs) and purified T lymphocytes. Extracellular ATP (ATPe) triggered in these cells an increase in the cytoplasmic Ca2+ concentration ([Ca2+]i) and plasma membrane depolarization. Whereas both Ca2+ release from intracellular stores and influx across the plasma membrane were detected in the whole PBL population, only Ca2+ influx was observed in T cells. In the presence of near physiologic extracellular Na+ concentrations (125 mmol/L), Ca2+ permeability through the ATPe-gated channel was very low, suggesting a higher selectivity for monovalent over divalent cations. The selective P2Z agonist benzoylbenzoic ATP (BzATP) increased [Ca2+]i in the presence but not the absence of extracellular Ca2+ and also caused plasma membrane depolarization. The covalent blocker oxidized ATP (oATP), an inhibitor of P2X and P2Z receptors, prevented Ca2+ influx and plasma membrane depolarization, but had no effect on Ca2+ release from stores. Stimulation with ATPe alone had no significant effects on PBL 3H-thymidine incorporation. On the contrary, ATPe or BzATP had a synergistic effect on DNA synthesis stimulated by selective T-cell mitogens such as phytohemagglutinin, anti-CD3 monoclonal antibody, or allogenic PBLs (mixed lymphocyte cultures). Treatment with oATP inhibited mitogenic stimulation by these receptor-directed agents but not by the combined application of the Ca2+ ionophore ionomycin and phorbol myristate acetate. Interleukin-2 partially relieved inhibition by oATP. These results suggest that human T lymphocytes express a plasma membrane channel gated by ATPe that is involved in mitogenic stimulation.     

Blood donation leads to a decrease in natural killer cell activity: a study in normal blood donors and cancer patients

Transfusion-induced immunosuppression has long been known to be beneficial for organ transplantation patients, but recent retrospective studies suggest that blood transfusions may be detrimental for patients with cancer. If autologous blood is used to avoid immunosuppression, the assumption is that the procedure, involving blood donation, is immunologically neutral. In the present study, this assumption was evaluated by monitoring 33 normal blood donors and 16 colorectal cancer patients before and after donation of 1 (500 mL) and 2 units of blood, respectively. The cancer patients belonged to the autologous arm of a randomized trial in which the effects of allogeneic versus autologous blood on cancer prognosis were studied. The patients donated 2 units of blood with an interval of 3 to 4 days between donations. Flow cytometric analysis revealed that blood donation by normal donors and cancer patients had no effect on the proportion of B, T, and natural killer (NK) cells. Only the total number of lymphocytes was significantly decreased in the normal donors on Day 12 after donation. Blood donation had no significant effect on T-cell function assessed by phytohemagglutinin stimulation in normal donors or in cancer patients donating 2 units of blood. A significant depression of NK cell function (88% and 74% of predonation levels) was observed in normal donors on Days 2 and 5 after donation; on Day 12, the activity was again normal. Colorectal cancer patients had a significantly depressed NK cell activity (54% of predonation activity) on Day 12 after the first donation.(ABSTRACT TRUNCATED AT 250 WORDS)     

NOTCH1 activation clinically antagonizes the unfavorable effect of PTEN inactivation in BFM-treated children with precursor T-cell acute lymphoblastic leukemia

Despite improvements in treatment results for pediatric T-cell acute lymphoblastic leukemia, approximately 20% of patients relapse with dismal prognosis. PTEN inactivation and NOTCH1 activation are known frequent leukemogenic events but their effect on outcome is still controversial. We analyzed the effect of PTEN inactivation and its interaction with NOTCH1 activation on treatment response and long-term outcome in 301 ALL-BFM treated children with T-cell acute lymphoblastic leukemia. We identified PTEN mutations in 52 of 301 (17.3%) of patients. In univariate analyses this was significantly associated with increased resistance to induction chemotherapy and a trend towards poor long-term outcome. By contrast, patients with inactivating PTEN and activating NOTCH1 mutations showed marked sensitivity to induction treatment and excellent long-term outcome, which was similar to patients with NOTCH1 mutations only, and more favorable than in patients with PTEN mutations only. Notably, in the subgroup of patients with a prednisone- and minimal residual disease (MRD)-response based medium risk profile, PTEN-mutations without co-existing NOTCH1-mutations represented an MRD-independent highly significant high-risk biomarker. Mutations of PTEN highly significantly indicate a poor prognosis in T-ALL patients who have been stratified to the medium risk group of the BFM-protocol. This effect is clinically neutralized by NOTCH1 mutations. Although these results have not yet been explained by an obvious molecular mechanism, they contribute to the development of new molecularly defined stratification algorithms. Furthermore, these data have unexpected potential implications for the development of NOTCH1 inhibitors in the treatment of T-cell acute lymphoblastic leukemia in general, and in those with a combination of PTEN and NOTCH1 mutations in particular.