Increased PAK6 expression in prostate cancer and identification of PAK6 associated proteins.
ABSTRACT PAK6 is a member of the p21-activated kinase (PAK) family of serine/threonine kinases that was originally cloned from prostate cancer (PCa) cells as an androgen receptor interacting protein, but its cellular distribution and functions have not been established.
An affinity purified rabbit anti-PAK6 antiserum was generated to assess PAK6 protein expression. PAK6 associated proteins were identified by immunopurification of 3xFlag-tagged PAK6 followed by LC/MS/MS.
We confirmed that PAK6 protein is expressed in prostate and breast cancer cell lines. PAK6 expression in LNCaP PCa cells was not directly androgen regulated, but was markedly increased when the cells were cultured for 6-8 weeks in steroid hormone depleted medium. By immunohistochemistry, PAK6 was weakly expressed in normal prostate epithelium. Its expression was increased in primary and metastatic PCa, and was further increased in tumors that relapsed after androgen deprivation therapy. LC/MS/MS identified IQ motif containing GTPase activating protein 1 (IQGAP1) and protein phosphatase 1B (PP1B) as candidate PAK6 interacting proteins, and these findings were confirmed by coimmunoprecipitation.
These results indicate that PAK6 contributes to PCa development and progression after androgen deprivation therapy, and that it may play roles in the regulation of motility and in stress responses.
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ABSTRACT: The present study analyzed the expression by immunochemistry of the novel markers P21-activated protein kinase 6 (PAK6) and proteasome beta-4 subunit (PSMB4) in men with localized prostate cancer (PC) who were treated with dose-escalation radiotherapy (RT) and androgen deprivation therapy.Urologic Oncology 06/2014; · 3.36 Impact Factor
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ABSTRACT: BackgroundINPP4B and PTEN dual specificity phosphatases are frequently lost during progression of prostate cancer to metastatic disease. We and others have previously shown that loss of INPP4B expression correlates with poor prognosis in multiple malignancies and with metastatic spread in prostate cancer.ResultsWe demonstrate that de novo expression of INPP4B in highly invasive human prostate carcinoma PC-3 cells suppresses their invasion both in vitro and in vivo. Using global gene expression analysis, we found that INPP4B regulates a number of genes associated with cell adhesion, the extracellular matrix, and the cytoskeleton. Importantly, de novo expressed INPP4B suppressed the proinflammatory chemokine IL-8 and induced PAK6. These genes were regulated in a reciprocal manner following downregulation of INPP4B in the independently derived INPP4B-positive LNCaP prostate cancer cell line. Inhibition of PI3K/Akt pathway, which is highly active in both PC-3 and LNCaP cells, did not reproduce INPP4B mediated suppression of IL-8 mRNA expression in either cell type. In contrast, inhibition of PKC signaling phenocopied INPP4B-mediated inhibitory effect on IL-8 in either prostate cancer cell lines. In PC-3 cells, INPP4B overexpression caused a decline in the level of metastases associated BIRC5 protein, phosphorylation of PKC, and expression of the common PKC and IL-8 downstream target, COX-2. Reciprocally, COX-2 expression was increased in LNCaP cells following depletion of endogenous INPP4B.Conclusion Taken together, we discovered that INPP4B is a novel suppressor of oncogenic PKC signaling, further emphasizing the role of INPP4B in maintaining normal physiology of prostate epithelium and suppressing metastatic potential of prostate tumors.Cell Communication and Signaling 09/2014; 12(1):61. · 4.67 Impact Factor
- Frontiers in Bioscience 01/2011; 16(1):849. · 4.25 Impact Factor