Inhibition of ZL55 cell proliferation by ADP via PKC‐dependent signalling pathway

Abstract

Extracellular nucleotides can regulate cell proliferation in both normal and tumorigenic tissues. Here, we studied how extracellular nucleotides regulate the proliferation of ZL55 cells, a mesothelioma-derived cell line obtained from bioptic samples of asbestos-exposed patients. ADP and 2-MeS-ADP inhibited ZL55 cell proliferation, whereas ATP, UTP, and UDP were inactive. The nucleotide potency profile and the blockade of the ADP-mediated inhibitory effect by the phospholipase C inhibitor U-73122 suggest that P2Y1 receptor controls ZL55 cell proliferation. The activation of P2Y1 receptor by ADP leads to activation of intracellular transduction pathways involving [Ca ] , PKC-δ/PKC-α, and MAPKs, ERK1/2 and JNK1/2. Cell treatment with ADP or 2-MeS-ADP also provokes the activation of p53, causing an accumulation of the G1 cyclin-dependent kinase inhibitors p21 and p27 . Inhibition of ZL55 cell proliferation by ADP was completely reversed by inhibiting MEK1/2, or JNK1/2, or PKC-δ, and PKC-α. Through the inhibition of ADP-activated transductional kinases it was found that PKC-δ was responsible for JNK1/2 activation. JNK1/2 has a role in transcriptional up-regulation of p53, p21 , and p27 . Conversely, the ADP-activated PKC-α provoked ERK1/2 phosphorylation. ERK1/2 increased p53 stabilization, required to G1 arrest of ZL55 cells. Concluding, the importance of the study is twofold: first, results shed light on the mechanism of cell cycle inhibition by ADP; second, results suggest that extracellular ADP may inhibit mesothelioma progression.

Adenosine diphosphate regulates MMP2 and MMP9 activity in malignant mesothelioma cells

“…We demonstrated previously that ADP induces a dose‐ and time‐dependent activation of ERK1/2 in ZL55 cells …”

“…Our results demonstrate for the first time that the P2Y1 receptor, following ADP (or 2‐MeS‐ADP) stimulation, increases the expression of MMP2/9 and induces their nuclear localization in human epithelioid ZL55 mesothelioma cells. Previously, we showed the expression in ZL55 cells of the P2Y1, P2Y4, P2Y6, and P2Y11 subtypes of nucleotide receptors, and that the inhibition of ZL55 cell proliferation occurred through activation of P2Y1 receptors …”

“…MMP expression is primarily regulated at the transcriptional level. Some of the key transcription factor binding sites involved in this regulation are the activator proteins (AP)‐1 and AP‐2 sites, the cAMP response element‐binding protein (CREB) site, the NF‐κB site, and the STAT site . The NF‐κB pathway is involved in the transcription of MMP2/9 upon activation by a number of growth factors and cytokines in pathological conditions, such as arthritis, muscular disorders, and cancer .…”

“…These results are consistent with results obtained in thrombin‐stimulated rat brain astrocytes, TNF‐α–stimulated human airway smooth muscle cells, and CCL20‐stimulated normal and tumor breast cells, where MMP2/9 expression is mediated through a PI3K/Akt cascade The kinase c‐Src also appears to be important in the transduction pathway linking ADP to MMP2/9 modulation, since its inhibition decreased both the nuclear translocation of NF‐κB and the upregulation/secretion of MMP2/9. In this regard, it has been demonstrated that the Src family kinases play a key role in G protein‐coupled receptor and growth factor receptor signaling, which are involved in the expression of inflammatory genes, such as MMP2/9, in various cells …”

Adenosine diphosphate–sensitive P2Y11 receptor inhibits endothelial cell proliferation by induction of cell cycle arrest in the S phase and induces the expression of inflammatory mediators

“…37,38 Different signal transduction pathways transduce the control of inflammation by P2Y receptors, including the mitogen-activated protein kinases, ERK1/2, p38, and JNK. 11 P2Y activation has been showed to induce the downstream increase in phosphorylation of ERK and induce the release of proinflammatory cytokines such as IL-6, IL-8, MCP-1, IL-1β. 39,40 In our study, we found that ADP at high concentrations significantly induced the mRNA expression of VCAM-1 and ICAM-1, and induced a time-dependent increase in ERK1/2 phosphorylation.…”