Role of the p38 MAPK pathway in cisplatin-based therapy Javier Herna´ndez Losa 1 , Carlos Parada Cobo 1 , Juan Guinea Viniegra 1 , Victor Javier Sa´nchez- Arevalo Lobo 1 , Santiago Ramo´n y Cajal 1 and Ricardo Sa´nchez-Prieto* ,1 1 Unidad de Patologı´a Molecular, Hospital Universitario Puerta de Hierro, C/San Martin de Porres 4, 28035 Madrid, Spain p38 MAPK has been implicated in the response to cancer therapy. To determine whether the activation of p38 MAPK could be specific to cancer therapy, we investi- gated the activation of p38 MAPK in response to several chemotherapeutic agents, such as cisplatin, doxorubicin and taxol in several human cell lines. Activation of p38 MAPK was measured after exposure to several che- motherapeutic agents, using specific phosphoantibodies. Only cisplatin was able to activate p38 MAPK in all the cell lines tested. Furthermore, other platinum compounds such as transplatin and platinum (IV) chloride can induce activation of p38 MAPK. The kinetics of this activation is a key event in the biological role of p38 MAPK in response to cisplatin, as we conclude from the differences observed after treatment with transplatin and cisplatin. The p38 MAPK activation is independent of the origin or genetic alterations of the cell lines and seems to be mediated through both upstream activators MKK6 and MKK3. Although the isoforms a/b are mainly activated, we also demonstrated that other members of the p38 MAPK family were susceptible to activation by cisplatin when they were overexpressed in 293 T. Finally, pretreat- ment with specific inhibitors (SB 203580 and SKF 86002) induces a resistant phenotype in response to cisplatin. Furthermore, low activation of this SAPK pathway correlates with a resistant phenotype as demonstrated in our experimental model of head and neck cancer. There- fore, we conclude that the p38 MAPK pathway is a specific target for cisplatin-based therapy with clinical implications. Oncogene (2003) 22, 3998–4006.doi:10.1038/sj.onc.1206608 Keywords: p38 MAPK; cisplatin; phosphorylation resistance; p38 MAPK g/ERK6; p38 MAPK d/SAPK4 Introduction Although the signalling events induced by chemo and radiotherapy are one of the most active fields in cancer research, it is still not fully understood how the cells respond to cancer therapy. It is very well established that proteins like Abl (Kharbanda et al., 1998), DNA- PK (Smith and Jackson, 1999), ATM (Khanna and Jackson, 2001) and p53 (Lakin and Jackson, 1999) are implicated in the response to chemo- and radiotherapy. Most of these proteins have been linked to the stress- activated protein kinase family (SAPK), as their activators (Kharbanda et al., 1995; Pandey et al., 1996; Yu et al., 2000). The c-Jun N-terminal kinase (JNK) and the p38 mitogen-activated protein kinase (MAPK)mainlycomprisetheSAPKfamily.Inthecase ofJNK,itsroleincancertherapyisverywellestablished (Sanchez-Perez et al., 1998; Verheij et al., 1998). p38 MAPK has been implicated in inflammation, osmotic stress, cell cycle regulation, differentiation and many otherbiologicalprocesses(forareview,seeNebredaand Porras,2000;KyriakisandAvruch,2001).However,the implicationofp38MAPKincancertherapyisnotclear. Recently, a growing body of evidence suggests that p38 MAPK is able to control the p53-mediated response to severalgenotoxicstimuli,suchasUVlightandcisplatin (CDDP) (Bulavin et al., 1999; Sanchez-Prieto et al., 2000). Indeed, c-Abl has been shown to control p38 MAPK activation after CDDP exposure (Pandey et al., 1996) and also the activation seems to be mediated by ASK1 (Chen et al., 1999). However, most of these studies have been performed using experimental models such as NIH 3T3 or 293 cells and no comparison with otherantitumourtreatmentshasbeencarriedoutsofar. Furthermore, no study has been performed with nontransformed human cell lines, which indicates that there is still no definitive clue about the role of p38 MAPK in response to chemo or radiotherapy. Among the several antitumour drugs, some of the mostrepresentativeandbettercharacterizedareCDDP, doxorubicin (DOX) and taxol (TAX). CDDP is a typical DNA-damaging agent with the ability to induce crosslinking between inter and intra DNA strands (Trimmer and Essigmann, 1999). CDDP is known for itsabilitytoinduceapoptosis,althoughitisnottheonly waytoinducecelldeath(forareviewseeGonzalez et al., 2001).CDDPisusedinseveraltypesoftumourssuchas head and neck, ovary or lung cancer. DOX, an antitumourantibioticusedinseveraltumours,hasbeen demonstratedtobeapotentintercalatingagentwiththe ability to induce the production of free radicals that generate single and double-strand breaks and also to blockDNAmodifyingenzymes,suchastopoisomerases and helicases (Cummings and Smyth, 1993). TAX Received10June2002;revised21March2003;accepted21March2003 *Correspondence: R Sa´nchez-Prieto; E-mail: rsanchez@hpth.insalud.es Oncogene (2003) 22, 3998–4006 & 2003 Nature Publishing Group All rights reserved 0950-9232/03 $25.00 www.nature.com/onc