Signal antonymy unique to myelodysplastic marrows correlates with altered expression of E2F1

Myelodysplastic syndromes (MDS) have previously been reported to show compe titively high rates of apoptosis and proliferation in the bone marrow (BM). Using a double-labelling technique in the present study, we demonstrated t hat a significantly high number of S-phase cells were simultaneously apopto tic (signal antonymy; SA) in MDS (mean +/- s.e.m. 53.5 +/- 6.7%. n = 24, P < 0.001). In contrast, SA was negligible in all other specimens studied, in cluding normal control BM (n = 13) from non-Hodgkin's lymphoma (NHL) patien ts. BM from patients with de novo acute myelogenous leukaemia (1'AML: n = 5 ), or secondary AML that had transformed from MDS (2'AML: n = 10), or the s olid tumours from patients with NHL (n = 3) or head and neck squamous cell carcinoma (HNSCC: n = 10). Subsequently, the expression of a transcription factor, E2F1, was studied in density-separated BM aspirate mononuclear cell s from MDS patients (n = 9) and a normal control. Two separate sets of prim ers were used that recognized the regulatory retinoblastoma (Rb) protein-bi nding region and the functional DNA-binding region of E2F1. Interestingly a lthough the latter manifested the expected band (280 bp) in all samples, th e Rb-specific primers showed the expected band (380 bp) in the normal and i n 4/9 MDS specimens, Two other MDS specimens also showed a smaller band (si milar to 325 bp), whereas 3/9 MDS patients showed exclusively the smaller b and. The levels of SR were significantly higher in those MDS cases that sho wed the smaller Rb-specific band either alone or in addition to the expecte d band (median 19.5%, n = 4, P = 0.037) than in those showing exclusively t he expected band (median 0.4%, n = 3). Our present studies show Sn as a cha racteristic feature of MDS and, importantly, demonstrate its link, with an altered expression of E2F1 in some MDS patients.