Synergistic activation of p70S6 kinase associated with stem cell factor in MO7e cells

Stem cell factor (SCF) is an early-acting cytokine inducing proliferative synergy with other cytokines in hematopoietic cells. We earlier showed that p21 was synergistically induced in SCF synergy and the p44/42 MAPK pathway was essential for the transcriptional control of p21. SCF synergy accompanies protein synthesis. p70S6K implicated in translational control in many other systems has not been shown in SCF synergy induced system. GM-CSF dependent human cell line MO7e was stimulated with GM-CSF with SCF, and investigated activation of p70S6K by using phospho-specific antibody. A possible contribution of p70S6K to SCF synergy was examined by measuring p21 induction as a model system. p70S6K was slightly activated by GM-CSF alone and markedly activated by SCF alone. Combined stimulation with these two cytokines synergistically activated p70S6K resulting in persistent activation. Addition of the pathway- specific inhibitors for PI3K or FRAP/TOR, two upstream pathways of p70S6K resulted in abolishment of p70S6K phosphorylation and also significant reduction of p21 protein level. These data suggest that synergistically activated p70S6K by GM-CSF plus SCF involves, at least in part, protein translational control including regulation of p21 protein.

Prognostic significance of myeloperoxidase containing blast cells in acute myelogenous leukaemia.

Fifty three newly diagnosed patients of de novo acute myelogenous leukaemia (AML) received treatment consisting of remission induction with daunorubicin 60 mg/m2 on day one and continuous infusion of cytosine arabinoside 200 mg/m2/day over 24 h from day one to 7. Thereafter patients in complete remission received consolidation chemotherapy with two identical courses. Complete remission (CR) could be achieved in 40 patients (75.5%). Seven patients (13.2%) died with complications during aplasia phase following remission induction therapy while six patients (11.3%) had resistant disease. Twenty seven patients (67.5%) developed relapse while eight patients (15.1%) continue to remain in complete remission ranging from 51 to 68 months (median 62.5). The projected event free survival and disease free survival at 60 months is 15 per cent (SE + 11.9%) and 21 per cent (+6%) respectively. Evaluation of the prognostic significance of pretherapy characteristics showed that infection at presentation and low number of myeloperoxidase (MPO) containing blasts affected the achievement of complete remission adversely on univariate analysis. Similarly age at diagnosis, of more than 45 yr, total leucocyte count of 50,000/cumm or more and low number of MPO containing blasts affected the remission duration (disease free survival) adversely on univariate analysis. On multivariate analysis, MPO positivity of blast cells, remained the only significant independent characteristic. High MPO positivity affected the remission duration favourably (P < 0.01). Patients with high MPO positivity also achieved CR with one induction cycle in 32 out of 40 instances while only 2 out of 5 patients with low MPO positivity, achieved CR with one chemotherapy cycle (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)