Abstract 3395: Role of the activating protein 2 transcription factor in regulating cell invasion and migration in malignant glioma

Abstract

Abstract Background: Malignant gliomas (MG) or high-grade astrocytomas are highly infiltrative brain tumors. Our previous work has shown that brain fatty acid binding protein (B-FABP) regulates the migratory properties of MG cells. B-FABP expression can be controlled by transcription factors such as NF1 and AP2. AP2 is a family of transcription factors involved in the regulation of genes responsible for cellular growth and differentiation during early development. Five AP2 genes have been identified in mice and humans: AP2α, AP2β, AP2γ, AP2δ and AP2ε. AP2 transcription factors are predominantly localized in the nucleus where they bind as homodimers or heterodimers to the consensus sequence GCCNNNGGC. Recent studies have shown that AP2α expression is inversely correlated with astrocytoma grade and that there are higher levels of AP2α in the cytoplasm of high-grade astrocytomas compared to low-grade astrocytomas. Objective: To study the regulation of B-FABP expression in response to AP2 in MG. Methodology: A panel of 10 MG cell lines was used to examine AP2α protein levels. Five of these cell lines were B-FABP +ve and five were B-FABP-ve. The effect of AP2 expression on endogenous B-FABP was examined by transfecting AP2 expression constructs into the B-FABP +ve U251 MG cell line. B-FABP levels were examined by western blot analysis and the subcellular localization of AP2 was studied by immunofluorescence analysis. Results: Western blot analysis indicates that AP2α is expressed in four out of five B-FABP-ve MG cell lines but in only one of the five B-FABP +ve MG cell lines tested. AP2 overexpression studies indicate that B-FABP levels are significantly reduced upon overexpression of AP2α, AP2β or AP2ε. Immunofluorescence data suggest preferential localization of AP2β in the cytoplasm of B-FABP +ve U251 MG cells. Our preliminary result shows difference in affinity towards heterodimerization between AP2 family members. Conclusion and future directions: AP2 is a negative regulator of B-FABP expression. Exclusion of AP2 from the nucleus allows transcription of B-FABP in MG cells, which in turn leads to increased cell migration. Experiments will be carried out to see the effect of AP2 heterodimerization on regulation of B-FABP transcription. Phosphorylation studies will be carried out to see whether AP2 phosphorylation affects its subcellular localization. This study may lead to new approaches to reduce B-FABP expression in MG, thereby reducing or preventing cell migration and tumor infiltration. Citation Format: Saket Jain, Ho Yin Poon, Roseline Godbout. Role of the activating protein 2 transcription factor in regulating cell invasion and migration in malignant glioma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3395. doi:10.1158/1538-7445.AM2014-3395