Rabbit Anti-Human PAK1 (a.a. 14-65) Polyclonal antibody

Background/Aims: p21-activated Ser/Thr kinase 1 (PAK1) is essential for the genesis and development of many cancers. The purpose of this study was to investigate the role of the PAK1-cyclic AMP response element-binding (CREB) axis in non-small cell lung cancer (NSCLC) tumorigenesis and its related mechanisms. Methods: Western blot assay and immunohistochemical staining were employed to investigate the PAK1 and CREB expression in the tissue microarray of human squamous NSCLC. Co-immunoprecipitation and immunofluorescence confocal assays were performed to determine the link between PAK1 and CREB. NSCLC xenograft models were used to study oncogenic function of PAK1 in vivo. Results: We observed that PAK1 and CREB expression levels were significantly elevated in human squamous NSCLC-tissue specimens, compared with those in adjacent normal bronchial or bronchiolar epithelial-tissue specimens, as well as their phosphorylated forms, based on western blotting. We showed in vitro that PAK1 knockdown by small-interfering RNA (siRNA) blocked CREB phosphorylation, whereas plasmid-based PAK1 overexpression resulted in CREB phosphorylation at Ser133, based on western blotting. In addition, PAK1 interacted with CREB in co-immunoprecipitation assays. Additionally, our in vitro findings detected by flow cytometry revealed that PAK1 silencing attenuated cell cycle progression, inducing apoptosis. Inhibition of PAK1 expression reduced tumor sizes and masses by modulating CREB expression and activation in xenograft models. Conclusion: These results suggest a novel mechanism whereby the PAK1-CREB axis drives carcinogenesis of squamous-cell carcinomas, and have important implications in the development of targeted therapeutics for squamous-cell lung cancer.

P21-activated kinase 1 (Pak1) is known to be involved in a plethora of functions including cell growth, survival and can lead to cell transformation and tumor progression especially in breast tissue. Multiple studies have shown Pak1 dysregulation as a change in DNA copy number as well as gene expression levels, suggesting many regulatory mechanisms at transcriptional and translational level. However, very little is known about the transcriptional regulation of the human Pak1 promoter. Here, we focus on Pak1 promoter regulation by steroid hormones along with their respective receptors that are also crucial players in breast tissue function and tumorigenesis. Our results show high Pak1 expression in breast cancer cell lines and in breast tumor tissue. It also suggests that Pak1 is hormone responsive, whose expression can be modulated by steroid hormones namely, estrogen in the form of 17 beta-estradiol (E2) and progesterone (P4). Sequence analysis of a 3.2 kb Pak1 proximal promoter region shows the presence of PRE (progesterone response element) and ERE (estrogen response element) half sites, that were further cloned and characterized. Results from promoter analysis showed that Pak1 promoter activity is mediated by PR via its binding to PRE present on the Pak1 promoter that was further reaffirmed in vitro by electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation assay (ChIP). Our results together suggest that it is the PR isoform B regulates Pak1 promoter. To our knowledge, this is the first study to report the detailed characterization and transcriptional regulation of the human Pak1 promoter by steroid hormones.