P53 Protein Isoform Profiles in AML: Correlation with Distinct Differentiation Stages and Response to Epigenetic Differentiation Therapy.

Ingvild Haaland,Håkon Reikvam,Emmet Mccormack,Øystein Bruserud,Anita Ryningen,André Sulen,Sigrun M Hjelle,Bjørn Tore Gjertsen

doi:10.3390/cells10040833

Abstract

p53 protein isoform expression has been found to correlate with prognosis and chemotherapy response in acute myeloid leukemia (AML). We aimed to investigate how p53 protein isoforms are modulated during epigenetic differentiation therapy in AML, and if p53 isoform expression could be a potential biomarker for predicting a response to this treatment. p53 full-length (FL), p53β and p53γ protein isoforms were analyzed by 1D and 2D gel immunoblots in AML cell lines, primary AML cells from untreated patients and AML cells from patients before and after treatment with valproic acid (VPA), all-trans retinoic acid (ATRA) and theophylline. Furthermore, global gene expression profiling analysis was performed on samples from the clinical protocol. Correlation analyses were performed between p53 protein isoform expression and in vitro VPA sensitivity and FAB (French–American–British) class in primary AML cells. The results show downregulation of p53β/γ and upregulation of p53FL in AML cell lines treated with VPA, and in some of the patients treated with differentiation therapy. p53FL positively correlated with in vitro VPA sensitivity and the FAB class of AML, while p53β/γ isoforms negatively correlated with the same. Our results indicate that p53 protein isoforms are modulated by and may predict sensitivity to differentiation therapy in AML.

Highlights

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In order to investigate if p53 protein isoform expression could provide independent information regarding sensitivity to differentiation therapy in acute myeloid leukemia (AML) patients, we performed a correlation analysis between p53 protein isoform expression and in vitro sensitivity to valproic acid (VPA) in primary AML cells (PBMC with >95% AML blasts) (n = 21)
Primary AML cells were treated with 0.5 mM VPA for 48 h, followed by a determination of proliferation (3H-thymidine incorporation), while an analysis of p53 isoforms was performed in untreated samples

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. P53 isoforms have over the last decades emerged as promising potential biomarkers in cancer diagnosis and in therapy response prediction [1,2,3,4]. P53 isoforms have been found to predict prognosis in cancer types like esophageal squamous cell carcinoma, prostate cancer, ovarian cancer, renal cell carcinoma, breast cancer and acute myeloid leukemia (AML) [9,10,11,12,13,14,15,16]. AML patients with low levels of p53FL and high levels of p53β/γ protein isoforms seem to have a better prognosis and response to chemotherapy than patients with already high levels of p53FL and low levels of p53β/γ [16]. The main aim of this work was to investigate if p53 protein isoform expression could be a potential independent biomarker for predicting a response to differentiation therapy in AML. We used 2D gel immunoblots of p53FL and p53β/γ protein isoforms and an in-housedeveloped pixel-by-pixel correlation method, and showed that in vitro VPA sensitivity of primary AML cells positively correlated with the expression of p53FL and negatively correlated with the expression of p53β/γ protein isoforms

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