RESUMEN
The presence of p53-pathway dysfunction in chronic lymphocytic leukemia (CLL) can be used to identify patients with chemotherapy-refractory disease. Therapeutic responses are known to vary between patients with chemosensitive CLL and may relate to differences in p53-pathway activity. We hypothesized that the magnitude or type of p53-pathway protein expression is heterogeneous in patients with chemosensitive disease and could associate with white cell responses. In this pilot study, changes in p53 and its transcriptional targets, p21/waf1 and MDM2 were analyzed by immunoblotting and densitometry in CLL cells from 10 patients immediately prior to the start of chemotherapy, and after culture for 24 hours (h) with fludarabine (n=7) or chlorambucil (n=3). The in vitro response was also compared to that in vivo in circulating cells pre-treatment, and at 24h and 96h of chemotherapy. Disease responses were evident in all patients after the first treatment-cycle. Significant p53 induction was observed in CLL cells treated in vitro and in vivo. Greater heterogeneity in the expression-intensity was observed in vivo (σ2=45.15) than in vitro (σ2=1.33) and the results failed to correlate (r(2)=0.18, p=0.22). p21/waf1 and MDM2 expression-profiles were also dissimilar in vitro and in vivo. Higher in vivo (but not in vitro) responses associated with changes in white cell count (p=0.026). Thus, heterogeneity of p53-pathway activity exists in chemosensitive CLL; in unselected patients, in vivo changes do not correlate with those in vitro, but may associate with post-treatment white cell responses.
RESUMEN
An autoimmune mechanism in the pathogenesis of myelodysplastic syndrome (MDS) is suggested by response to immunosuppression, with CD8+ T-lymphocytes implicated in the haematopoietic suppression. We therefore sought evidence for human leucocyte antigen (HLA) restriction and variant frequency differences in selected polymorphisms at the loci for the immunomodulatory cytokines, tumour necrosis factor alpha (TNF-alpha), lymphotoxin-alpha (LT-alpha) and interleukin 10 (IL-10) in patients with MDS and acute myeloid leukaemia (AML) compared with normal controls. DNA from 150 MDS/AML patients [24 AML, 53 refractory anaemia (RA), 25 RA with excess blasts (RAEB), four RAEB in transformation (RAEBt), 21 sideroblastic leukaemia, 22 chronic myelomonocytic leukaemia] was screened. Control data was from Scottish blood donors (HLA class I/II), healthy General Practitioner-based subjects (TNF-alpha/LT-alpha) and published values (IL-10). HLA class I/II haplotypes were determined using sequence-specific primers. Polymorphisms were assayed at TNF-alpha -308, LT-alpha +252 and IL10 -824, -597 and -1082 loci. Variant frequencies of common haplotypes at HLA class I and II, high-/low-producer TNF-alpha/LT-alpha and IL-10 loci were not different between patients and controls or within the French-American-British, International Prognostic Scoring System or cytogenetic subgroups and were not associated with altered survival for MDS/AML patients. TNF2 allele frequency was greater in the MDS/AML cohort (chi2 = 6.593, P < 0.05) but the biological significance was uncertain in the absence of an increased high-producer TNF-alpha/LT-alpha haplotype frequency. We can find no genetic influence for these polymorphisms in HLA class I/II, TNF-alpha/LT-alpha and IL-10 loci on either predisposition or disease progression in MDS/AML.
