Statins inhibit Akt/PKB signaling via P2X7 receptor in pancreatic cancer cells

Abstract

To cite this version:Oras Mistafa, Ulla Stenius. Statins inhibit Akt/PKB signaling via P2X7 receptor in pancreatic cancer cells. Biochemical Pharmacology, Elsevier, 2009, 78 (9) This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Page 1 of 37A c c e p t e d M a n u s c r i p t Abbreviations: 3-Hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase inhibitors, 5-fluorouracil (5-Fu), phosphatidylinositol 3-kinase (PI3K), glycogen synthase kinase 3 beta (GSK3β), small interference RNA (siRNA), phosphorylation of Akt on residue Ser473 (pAkt Ser473), phosphorylation of Akt on residue Thr308 (pAkt Thr308), GSK3 on residue Ser9 (pGSK3β Ser9), nuclear factor kappa-B-(NF-B), mitogen-activated protein kinas (MAPK), Purinergic receptor (P2X), ligand-gated ion channel 7 (P2X7), Human embryonic kidney (HEK), adenosine 5′-triphosphate periodate oxidized sodium salt (o-ATP), Poly (ADP-ribose) polymerase (PARP).Key words: atorvastatin, P2X7, Akt, chemotherapy, pancreatic cancer * ManuscriptPage 2 of 37 A c c e p t e d M a n u s c r i p t 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 Thus, experiments employing P2X7 siRNA and inhibitors supported an involvement of P2X7. In Capan-2 cells, which expressed P2X7 in low levels, statins did not reduce pAkt levels nor did statins sensitize them to cytostatic drugs. However, statin inhibited the growth of Capan-2 cells and this correlated to inhibition of NFB and Raf/MEK pathways. As shown previously, these latter effects can be explained by an inhibited protein prenylation. Our data suggest that statins primarily target a functional P2X7-Akt signaling in pancreatic cancer cells. By targeting the P2X7-Akt axis, statins can sensitize pancreatic cancer cells to chemotherapeutic drugs. Our data are also in line with a role for P2X7 in the chemopreventive effect of statins on pancreatic cancer.

Statins exhibit anticancer effects through modifications of the pAkt signaling pathway

“…We also find that the downstream signaling of Akt is attenuated, and that the selection process resulted in an apparently stable cell phenotype exhibiting a reduced or absent nuclear pAkt response to insulin. These alterations confirm our previous results indicating that statins target the P2X7-Akt axis in cultured cells (13)(14)(15). Our present results also suggest that this axis is an important cell signaling pathway that might be critical for statin toxicity and that can modify insulin signaling.…”

“…Different types of statins have been reported to decrease the levels of phosphorylated Akt in several cell lines, and our group has shown that pravastatin, simvastatin and atorvastatin lower the insulininduced nuclear pAkt accumulation without affecting the total Akt levels in A549 cells (15). This effect is mediated by P2X7, and is associated with altered phosphorylations of downstream targets of pAkt, including GSK3β and cyclin D1 (13,14).…”

“…Here we investigated the cellular effects of the long-term treatment with atorvastatin to gain insight into their mode of action in the prevention of cancer. Atorvastatin-induced selection of A549 cells was studied as the short-term effects on Akt/P2X7 signaling are best characterized in this cell model (13)(14)(15)22).…”

“…For example, we have previously shown that short-term statin-treatment sensitize cells to cytostatic drugs (13,15,22). Therefore we checked the responsiveness of long-term atorvastatin-selected cells to cytostatic drugs.…”

“…We previously demonstrated that statins rapidly activate the purinergic receptor P2X7 and affect Akt signaling, which may have important anti-cancer effects (13)(14)(15): these effects were observed within few minutes, and were not prevented by pre-incubation with mevalonate. The Akt pathway is one of the major anti-apoptotic factors in cells (16): it is activated by growth factors and cellular stress and is commonly overexpressed in different tumors, but is also often induced by cytostatic treatment (17,18).…”