Human prostate epithelium lacks Wee1A-mediated DNA damage-induced checkpoint enforcement

Abstract

Cellular DNA damage triggers the DNA damage response pathway and leads to enforcement of cell cycle checkpoints, which are essential for the maintenance of genomic integrity and are activated in early stages of tumorigenesis. A special feature of prostate cancer is its high incidence and multifocality. To address the functionality of DNA damage checkpoints in the prostate, we analyzed the responses of human primary prostate epithelial cells (HPECs) and freshly isolated human prostate tissues to ␥-irradiation. We find that ␥-irradiation activates the ataxia telangiectasia mutated-associated DNA damage response pathway in the HPECs but that the clearance of phosphorylated histone H2AX (␥H2AX) foci is delayed. Surprisingly, ␥-irradiated HPECs were unable to enforce cell cycle checkpoint arrest and had sustained cyclin-dependent kinase 2 (Cdk2)-associated kinase activity because of a lack of inhibitory Cdk phosphorylation by Wee1A tyrosine kinase. We further show that HPECs express low levels of Wee1A and that ectopic Wee1A efficiently rescues the checkpoints. We recapitulate the absence of checkpoint responses in epithelium of ex vivo irradiated human prostate tissue despite robust induction of ␥H2AX. The findings show that prostate epithelium has a surprising inability to control checkpoint arrest, the lack of which may predispose to accrual of DNA lesions.p53 ͉ irradiation ͉ cyclin-dependent kinase

Latexin exhibits tumor suppressor potential in hepatocellular carcinoma

“…Cyclin D1, cyclin E, CDK4 and CDK6 are also critical regulators of G1 progression and G1-S transition (33). Inhibition of cyclin D1, cyclin E and CDK4 activation blocks G1-S transition in the cell cycle (32)(33)(34)(35).…”

“…The INK4 families can bind to CDK4 and/or to CDK6 and inhibit the catalytic activity of the CDK/cyclin D complex (28)(29)(30)(31). Cyclin D1, cyclin E, CDK4 and CDK6 are also critical regulators of G1 progression and G1-S transition (33). Inhibition of cyclin D1, cyclin E and CDK4 activation blocks G1-S transition in the cell cycle (32)(33)(34)(35).…”

Proteasome inhibitors induce nucleolar aggregation of proteasome target proteins and polyadenylated RNA by altering ubiquitin availability

“…In addition, analysis of normal and malignant cell lines in their propensity to undergo p53 and MDM2 nucleolar localization following proteasome inhibition showed that the response was irrespective of tissue type or pathological status of the cells (Supplementary Table S1). Furthermore, treatment of ex vivo cultured human prostate tissues (Kiviharju-af Ha¨llstro¨m et al, 2007) with MG132 led to the formation of p53 aggregates in epithelial cells of the prostate gland, indicating that the aggregate formation is not only an artifact of cells cultured in monolayer, but is also observed in the context of normal tissue architecture (Supplementary Figure S1d).…”

Faithful DNA Replication Requires Regulation of CDK Activity by Checkpoint Kinases

“…Downregulation of the WEE1 protein was also observed in pituitary adenomas, and this was also associated with miRNA expression (Butz et al, 2010). Moreover, prostate epithelium, which is prone to prostate cancer development, also expressed very low levels of WEE1 (Kiviharju-af Hallstrom et al, 2007). Based on our studies (Beck et al, 2010), low levels of WEE1 during human tumorigenesis would likely lead to deregulated replication with subsequent spontaneous DNA damage in S phase.…”