A Distinct p53 Protein Isoform Signature Reflects the Onset of Induction Chemotherapy for Acute Myeloid Leukemia

Abstract

Purpose: The antioncogene protein product p53 has not been studied previously in cancer patients during in vivo chemotherapy.This study examined the early p53 protein and gene expression during induction chemotherapy in acute myeloid leukemia (AML). Experimental Design: Leukemic cells were collected from five AML patients during their first 18 hours of induction chemotherapy and examined for p53 protein and gene expression by one-and two-dimensional gel immunoblot and high-density gene expression arrays. Results: Up-regulation of p53 protein expression was detected in AML patients posttreatment in vivo. One-and two-dimensional gel immunoblots showed two main forms of p53, denominated ap53 and Dp53, both recognized by various NH 2 -terminal directed antibodies. As a response to treatment, we detected rapid accumulation of ap53, with significantly altered protein expression levels already after 2 hours.The accumulation of ap53 was accompanied by increased transcription of putative p53 target genes and subsequent cytopenia in the patients. Conclusion: Up-regulation of the p53 protein and target genes seems to be a prominent feature in induction chemotherapy of AML.The rapid shift from a shorter p53 protein form (D) toward the full-length protein (a) underscores the complexity of p53 protein modulation in patients undergoing chemotherapy.

Flt3 Y591 duplication and Bcl-2 overexpression are detected in acute myeloid leukemia cells with high levels of phosphorylated wild-type p53

“…We did not examine in detail p53 transcriptional activity in primary AML blast cells here; however, studies by our group have shown that expression of p53 target genes, including p21 and Bax, can be detected in AML blasts during in vivo therapy. 30 Typically, the p53 response of malignant cells is disabled by loss of heterozygosity of p53 or by loss of p53 pathway effectors. 6,31 The finding that wild-type p53 in AML blast cells was phosphorylated following DNA damage caused by a common chemotherapeutic agent is particularly striking (Figure 3).…”

Release of angiopoietin-1 by primary human acute myelogenous leukemia cells is associated with mutations of nucleophosmin, increased by bone marrow stromal cells and possibly antagonized by high systemic angiopoietin-2 levels

“…15 Features were extracted using Agilent Microarray ScannerBundle v7.5.1 and were processed using J-Express Pro v2.7 (www.molmine.com) to filter and normalize data from each hybridization and compile gene expression profile matrix data sets. 15 Analysis was restricted to patients with normal cytogenetics and FLT3-ITDs, and Significance Analysis of Microarrays (SAM) in J-Express Pro 2.7 was used to examine the correlation of gene expression data between AML cells with (10 patients) and without (nine patients) NPM1 mutations. SAM used 400 permutations of the sample sets to estimate the false discovery rate.…”

“…Real-time quantitative PCR was performed as previously described. 15 Dilution series of pooled samples were used for the generation of standard curves for each TaqMan assay including the endogenous control, glyceraldehyde-3-phosphate dehydrogenase. Samples were tested in duplicates.…”

Differential forms of p53 in medulloblastoma primary tumors, cell lines and xenografts

“…The human p53 gene can encode at least nine different p53 protein isoforms: p53, p53ß, p53Á, Δ133p53, Δ133p53ß and Δ133p53Á are produced by alternative splicing of the intron 9, and alternative usage of the alternative promoter in intron 4, and Δ40p53 (p47), Δ40p53ß and Δ40p53Á -produced by alternative splicing of intron 9, and alternative intitiation of translation or alternative splicing of intron 2 (14). p53 isoforms have been described in breast cancer, acute myeloid leukemia, neuroblastoma, and in squamous cell carcinoma of the head and neck (17)(18)(19)(20)(21). In leukemia the appearance of a low molecular weight form of p53 is inversely correlated with the response to induction chemotherapy (17).…”

“…p53 isoforms have been described in breast cancer, acute myeloid leukemia, neuroblastoma, and in squamous cell carcinoma of the head and neck (17)(18)(19)(20)(21). In leukemia the appearance of a low molecular weight form of p53 is inversely correlated with the response to induction chemotherapy (17). Despite all the experimental evidence showing the importance of p53 in preventing carcinogenesis, it is difficult in clinical studies to link p53 status to cancer treatment and clinical outcome.…”