Study On Abnormal Expression Of The P73, DCC, Nm23-H1, And E2A-PBX1 Genes In Childhood Acute Lymphoblastic Leukemia And Cell Lines

We investigated the levels of p73, DCC, nm23-H1, -H2 and E2A-PBX1 transcripts in 63 acute lymphoblastic leukemia (ALL) cell lines and 53 childhood patients with ALL using reverse transcriptase-polymerase chain reaction (RT-PCR) and quantitative RT-PCR analysis, and analyzed the association with the clinicopathological characteristics. We also analyzed methylation status of p73 exon 1 by restriction-enzyme related PCR (REP), methylation-specific PCR (MSP) and bisulfite genomic sequencing (BGS) analysis in 63 ALL cell lines. Of the 63 ALL cell lines. 42 showed expression of p73 mRNA, with the positive and negative rate 66.7%. 33.3% respectively. DCC transcripts were not detected in 29 of 63 ALL cell lines, with the negative rate 46.0%. The expression of the nm23-H1,-H2 in ALL cell lines was significantly higher than that in normal blood cells. Chimeric E2A-PBX1 transcript was found in 11.1 %(7/63) of ALL cell lines, and in 19.0%(7/37) of ALL cell lines with markers of early B-cell progenitors respectively. Of the 53 primary childhood ALL samples, 39 showed expression of p73 mRNA. with the positive and negative rate 73.6%, 26.4% respectively. DCC transcripts were not detected in 21 of 53 cases of ALL, with the negative rate 39.6%. The expression of the nm23-H1,-H2 in primary ALL samples was significantly higher than that in normal blood cells. Chimeric E2A-PBX1 transcript was found in 7.5 %(4/53) cases of ALL. An analysis of the correlation between p73 expression and clinic parameters showed loss of p73 expression was significantly associated with the reduced disease free survival (DFS) and the overall survival (OS) of ALL. Leukemias that express chimeric E2A-PBX1 transcript were also indicated to have a poor prognosis. As to the examination of methylation, it was found that 38.1 % (24/63) of ALL cell lines have hypermethylation in p73 exon 1. The results obtained by REP and MSP showed that normal lymphocytes and most cell lines that express detectable p73 mRNA were not hypermethylated. In contrast, cell lines lacking p73 mRNA expression were hypermethylated.Our results suggest that there were higher incidence of negative expression of p73 mRNA in childhood ALL. The main mechanism of loss expression, herein, would be the hypermethylation of p73 gene. p73 gene inactivation may play an important role in the development and/or progression of ALL. The examination of p73 mRNA may have clinical significance for predicting prognosis of childhood ALL. Our results also suggest that there were higher incidence...