Silencing of APAF‐1 in B‐CLL results in poor prognosis in the case of concomitant p53 mutation

Abstract

Apoptosis protease‐activating factor 1 (APAF‐1), a transcriptional target of p53, is a cytosolic adaptor protein that links the mitochondrial apoptosis pathway to the caspase cascade. Here, we aimed to study the impact of APAF‐1 expression levels on cell death induced by anticancer drugs or ionizing irradiation (IR) and disease prognosis in B‐type chronic lymphocytic leukemia (B‐CLL) patients. Samples from 138 patients with B‐CLL were investigated for APAF‐1 expression and p53 mutations. The results were related to survival data, in vitro cytotoxicity of various cytotoxic drugs and IR and clinico‐pathological data. Variable APAF‐1 expression was observed in all investigated B‐CLL samples. Reduction in APAF‐1 expression was observed at both mRNA and protein level indicating transcriptional silencing whereas mutation of p53 or the immunoglobulin heavy chain variable genes (IgHV) had no impact on APAF‐1 expression. Surprisingly, APAF‐1 loss did not result in resistance to cytotoxic therapies. Likewise, APAF‐1 downregulation on its own showed no impact on disease prognosis. Nevertheless, a poor prognosis was observed in patients with loss of APAF‐1 expression and additional p53 mutation. Thus, loss of APAF‐1 may become relevant when additional core apoptosis signaling components are disrupted. © 2005 Wiley‐Liss, Inc.

Requirement of Apoptotic Protease-Activating Factor-1 for Bortezomib-Induced Apoptosis but Not for Fas-Mediated Apoptosis in Human Leukemic Cells

“…Indeed, silencing of Apaf-1 protein expression by hypermethylation of the gene promoter has been reported in several human tumors, including malignant melanoma and acute leukemia (Fu et al, 2003). Silencing of Apaf-1 expression in B-cell chronic lymphoblastic leukemia (B-CLL) constitutes a negative prognostic marker in the case of concomitant p53 mutations (Sturm et al, 2006). Jia et al, (2001) reported that Apaf-1 deficiency constitutes a significant mode of resistance to cytochrome c-dependent apoptosis in human leukemia cells.…”

Low expression of APAF-1XL in acute myeloid leukemia may be associated with the failure of remission induction therapy

“…Several studies have demonstrated a strong relationship between APAF-1 expression and response to chemotherapy and progression or prognosis of many neoplastic diseases such as melanoma, Burkitt lymphoma, chronic lymphoid leukemia, colorectal cancer, and cervical cancer (31)(32)(33)(34)(35). Moreover, hypermethylation of the APAF-1 gene may be an independent prognostic factor in acute lymphoblastic leukemia (36).…”

“…The relative amounts of APAF-1 cDNAs with or without the additional COOH-terminal WDR were determined using the specific primers C1, 5'-CAGCTGAT GGAACCTTAAAGC-3' and C2, 5'-GTCTGGTCATCA GAAGATGTC-3' (12), and the following PCR conditions: 33 denaturation cycles of 30 s at 94°C, 50-s annealing at 58°C, and 50-s extension at 72°C, followed by a 5-min APAF-1 isoforms in acute myeloid leukemia www.bjournal.com.br extension at 72°C. In order to ensure that the RT-PCR signal was linear with respect to RNA input, we performed kinetic analysis by varying the number of amplification cycles (25,30,33,35,38) and the amount of cDNA input (0.25, 0.5, 0.75, 1.0, 1.25 µg), considering that the same amount of RNA was reverse-transcribed for each sample (Figure 1). On the basis of this analysis, we used 33 cycles for both pairs of primers and 1 µg cDNA.…”

Loss of Proapoptotic Gene Apaf-1 Expression in Pancreatic Cancer

“…APAF-1 geno raiška buvo vertinta iRNR lygmenyje, kadangi tyrimais įrodyta teigiama koreliacija tarp APAF-1 iRNR ir baltymo kiekio audinyje [8]. Mūsų tyrimas parodė reikšmingus APAF-1 geno raiškos skirtumus tarp navikinio audinio ir jį supančio sveiko audinio.…”