Poster abstracts

Poster number 69 submitted by Sung-Suk Suh

Regulation of expreesion of multiple miRNAs defines the cellular response to non genotoxic p53 activation in multiple myeloma cells

Flavia Pichiorri (Comprehesive Cancer Center), Cristian Taccioli (Comprehesive Cancer Center), Luciana De Luca (Comprehesive Cancer Center), Craig Hofmeister (Comprehesive Cancer Center)

Abstract:
Multiple myeloma (MM) is an incurable neoplastic disease of B cell origin, affecting 50,000 patients in the United States, occurring in approximately 16,000 new individuals each year. In MM, mutation or deletion of p53 is rarely detected at diagnosis, although both become more frequent in advanced disease. Therapeutic activation of p53 might therefore be particularly suitable for the treatment of MM. Now we have used nutlin-3a, a recently developed small-molecule activator of p53, which efficiently disrupts the p53-MDM2 interaction, to profile a p53 miRNA activation pathway in the MM1s cell line. Furthermore we confirmed our data by qRT-PCR in primary MM cells. Results of the analysis have shown differential expression of 72 individual miRNAs after p53 activation, 32 showing up-regulation and 40 showing downregulation. Our results confirm published results; after p53 stabilization we found up-regulation of the miR-34 family, but we also detected strong up-regulation of several other miRNAs. We found consistent up-regulation after Nutlin-3a treatment, of miR-192-194 cluster and miR-215. To better understand the activation or down-regulation of these miRNAs after p53 non-genotoxic activation, we performed a real-time PCR experiment to check Myc level after the treatment. We found strong down-regulation of Myc mRNA (~5 times), probably through an indirect effect of p53 activation in MM cells. We did not find direct p53 activation of the promoters of miRNAs which were up-regulated after p53 expression, but observed several Myc consensus sequences, as in the case of miR-192-194 promoter. This is the first study to identify p53 regulated miRNAs in MM cells. Our data suggest that downstream signaling in the p53 pathway is functional in MM cells and can regulate miRNAs that are involved in the multi step process leading to malignant transformation of PCs.

Keywords: Multiple myeloma, miRNA, p53