Abstract
AGAP2 (Arf GAP with GTP-binding protein-like domain, Ankyrin repeat and PH domain 2) isoform 2 is considered a proto-oncogene, but not much is known about AGAP2 gene expression regulation. To get some insight into this process, AGAP2 proximal promoter was cloned and characterised using reporter assays. We have identified SP1 as a transcription factor bound to AGAP2 promoter and required for AGAP2 expression in two different types of cancer cells (KU812, a chronic myeloid leukaemia cell line; and DU145, a prostate cancer cell line): silencing SP1 decreased AGAP2 protein levels. We have also found that all-trans retinoic acid (ATRA) treatment increased AGAP2 protein levels in both cell lines whilst curcumin treatment reduced ATRA-mediated AGAP2 increase. Furthermore, chromatin immunoprecipitation studies revealed the presence of RARα, RXRα and the lysine acetyl transferase PCAF in AGAP2 promoter. Our results provide a novel understanding of AGAP2 expression regulation that could be beneficial to those patients with cancers where AGAP2 is overexpressed.
Highlights
AGAP2 (Arf GAP with GTP-binding protein-like domain, Ankyrin repeat and PH domain 2) is a protein that belongs to the Arf GAP (Arf GTPase activating protein) family of proteins
It has been suggested that AGAP2 overexpression is, in some cases, linked to the amplification of the CDK4 amplicon that occurs in several cancers[14]: AGAP2 gene is located in chromosome 12 adjunct to the CDK4 gene and, recently, it has been established that AGAP2 and CDK4 increased co-expression drives glioblastoma progression[15]
AGAP2 mRNA has been found in human peripheral blood lymphocytes[17] and human polymorphonuclear neutrophils[18], there are no reports to date studying AGAP2 expression and its role in chronic myeloid leukaemia (CML)
Summary
We found the treatment was able to induce AGAP2 protein expression (Fig. 4e) These results demonstrate for the first time that ATRA can mediate AGAP2 expression in different cancer cell lines. The different effects of ATRA treatment can be better understood when considering the work of Hammond et al.[36] They showed that RAR agonists and RAR antagonists affected prostate cancer cell lines, suggesting that cell survival might depend on a balance of RAR-mediated transcriptional activity. Chromatin immunoprecipitation studies were performed in the presence of serum in DU145 cells and confirmed that RARα, RXRα and PCAF were all found in AGAP2 promoter (Fig. 6a) These findings provide a possible mechanism for AGAP2 regulation, where, in the presence of Figure 3. Our results provide a novel understanding of AGAP2 expression regulation that could be beneficial to those patients with cancers where AGAP2 is overexpressed
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