EUROPLUS ANCA BIOCHIP mosaic: PR3 and MPO antigen microdots improve the laboratory diagnostics of ANCA-associated vasculitis.

INTRODUCTION: The consensus on anti-neutrophil cytoplasmic antibody (ANCA) testing requires screening with indirect immunofluorescence (IIF) and confirmation in MPO- and PR3-ANCA specific assays. The EUROPLUS system combines in one incubation the conventional cell substrates with microdots of single antigens, i.e., MPO and PR3. We evaluated the diagnostic applicability of this new system for ANCA-associated vasculitis (AAV). METHODS: To assess the diagnostic performance of the EUROPLUS Granulocyte Mosaic, sera from 249 AAV patients, 85 disease controls and 27 healthy controls were analysed. Results were compared with a reference multi-testing algorithm based on IIF with ethanol-fixed granulocytes, direct and capture ELISAs for both MPO- and PR3-ANCA. RESULTS: Based on the reference multi-testing algorithm 123 AAV patients were defined as having PR3-ANCA and 68 AAV patients as having MPO-ANCA (diagnostic sensitivity: 76.7%). For the EUROPLUS MPO and PR3 microdots the diagnostic sensitivity was 77.1% in the same AAV cohort. The concordance between both methods for PR3- and MPO-ANCA was 96.8% and 99.2%, respectively. In the control cohort the diagnostic specificity was 99.1% for the multi-testing algorithm and 98.2% for the EUROPLUS microdots. CONCLUSIONS: The combination of conventional cell substrates and single MPO and PR3 antigen microdots greatly facilitates the identification of ANCA reactivity clinically relevant for AAV. Since our results obtained after a single incubation in the EUROPLUS system are highly concordant with the reference multi-testing algorithm (based on IIF, direct and capture ELISAs) the EUROPLUS system is advocated as an efficient test system.

p53-independent regulation of p21Waf1/Cip1 expression and senescence by Chk2.

The Chk2 kinase is a tumor suppressor and key component of the DNA damage checkpoint response that encompasses cell cycle arrest, apoptosis, and DNA repair. It has also been shown to have a role in replicative senescence resulting from dysfunctional telomeres. Some of these functions are at least partially exerted through activation of the p53 transcription factor. High-level expression of virally transduced Chk2 in A549 human lung carcinoma cells led to arrested proliferation, apoptosis, and senescence. These were accompanied by various molecular events, including p21(Waf1/Cip1) (p21) transcriptional induction, consistent with p53 activation. However, Chk2-dependent senescence and p21 transcriptional induction also occurred in p53-defective SK-BR-3 (breast carcinoma) and HaCaT (immortalized keratinocyte) cells. Small interfering RNA-mediated knockdown of p21 in p53-defective cells expressing Chk2 resulted in a decrease in senescent cells. These results revealed a p53-independent role for Chk2 in p21 induction and senescence that may contribute to tumor suppression and genotoxic treatment outcome.

Inhibition of histone deacetylases by chlamydocin induces apoptosis and proteasome-mediated degradation of survivin.

The naturally occurring cyclic tetrapeptide chlamydocin is a very potent inhibitor of cell proliferation. Here we show that chlamydocin is a highly potent histone deacetylase (HDAC) inhibitor, inhibiting HDAC activity in vitro with an IC(50) of 1.3 nM. Like other HDAC inhibitors, chlamydocin induces the accumulation of hyperacetylated histones H3 and H4 in A2780 ovarian cancer cells, increases the expression of p21(cip1/waf1), and causes an accumulation of cells in G(2)/M phase of the cell cycle. In addition, chlamydocin induces apoptosis by activating caspase-3, which in turn leads to the cleavage of p21(cip1/waf1) into a 15-kDa breakdown product and drives cells from growth arrest into apoptosis. Concomitant with the activation of caspase-3 and cleavage of p21(cip1/waf1), chlamydocin decreases the protein level of survivin, a member of the inhibitor of apoptosis protein family that is selectively expressed in tumors. Although our data indicate a potential link between degradation of survivin and activation of the apoptotic pathway induced by HDAC inhibitors, stable overexpression of survivin does not suppress the activation of caspase-3 or cleavage of p21(cip1/waf1) induced by chlamydocin treatment. The decrease of survivin protein level is mediated by degradation via proteasomes since it can be inhibited by specific proteasome inhibitors. Taken together, our results show that induction of apoptosis by chlamydocin involves caspase-dependent cleavage of p21(cip1/waf1), which is strikingly associated with proteasome-mediated degradation of survivin.