Abstract 4353: Cycloxygenase-2 inhibitor regulates p73 isoform expression pattern, inhibit growth, and induce apoptosis in NHL cell line model with 1p36 chromosomal disruption.

Abstract

Abstract Diclofenac is a cycloxynase-2 (COX-2) inhibitor that is used in clinics as an analgesic anti-inflammatory drug and has been shown to increase TP73 gene signature in multiple tumor cell lines. TP73, a gene at 1p36 locus, is controlled by a balance between two isoforms with opposing functions, the full length TAp73 protein (pro-apoptotic) and the NH2-terminally truncated ΔNp73 protein (anti-apoptotic through antagonizing both TAp73 and p53). Our previous work has shown a differential ΔNp73 up-regulation among NHL cases with 1p36 chromosomal disruption correlates with decreased apoptosis, increased cellular proliferation and increased angiogenesis. Modulation of ΔNp73:TAp73 ratio using TAp73 expression vector in Granta-519 (NHL cell line model that harbor disrupted 1p36 and express high levels of ΔNp73) resulted in growth inhibition and increased response to chemotherapy. In this study, we hypothesized that diclofenac treatment will modulate the expression profile of p73 isoforms and alter the behavior of the NHL cells with 1p36 disruption. Diclofenac treatment of Granta-519 cells resulted in a decrease in ΔNp73, increase in TAp73 mRNA expression. MTT assay showed a concentration- and duration-dependent cell growth inhibition. Decreased expression of the proliferation marker ki-67 and cell cycle arrest as indicated by flow cytometric cell cycle analysis; were evident following diclofenac treatment. Furthermore, Annexin-V-Flous flow cytometric analysis showed increased number of apoptotic cells that was associated with increased cleaved caspase-3 following diclofenec treatment. Moreover, pro-apoptotic target genes expression was induced by diclofenac treatment including p21, PUMA, NOXA, and BIM. Next we tested the effect of diclofenac treatment on standard CHOP-resistant Granta-519 sub-clones, that resulted in down-regulation of ΔNp73 mRNA expression and a significant dose-dependent growth inhibitory effect. Together, our data demonstrate that diclofenac treatment caused p73 isoforms reconstitution (↑TAp73 and/or ↓ΔNp73), inhibited growth of NHL cells with 1p36 abnormality and highlights the potential of diclofenac as a potential new adjuvant therapy in NHL with disrupted TP73 gene region. Citation Format: Hesham M. Hassan, Michelle Varney, Shantaram S. Joshi, Rakesh K. Singh, Bhavana J. Dave. Cycloxygenase-2 inhibitor regulates p73 isoform expression pattern, inhibit growth, and induce apoptosis in NHL cell line model with 1p36 chromosomal disruption. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4353. doi:10.1158/1538-7445.AM2013-4353