Published OnlineFirst August 8, 2012; DOI: 10.1158/2159-8290.CD-12-0237 RESEARCH ARTICLE Rescue Screens with Secreted Proteins Reveal Compensatory Potential of Receptor Tyrosine Kinases in Driving Cancer Growth Fred Harbinski 1 , Vanessa J. Craig 3 , Sneha Sanghavi 1 , Douglas Jeffery 1 , Lijuan Liu 1 , Kelly Ann Sheppard 1 , Sabrina Wagner 3 , Christelle Stamm 3 , Andreas Buness 3 , Christian Chatenay-Rivauday3 , Ya o Ya o 5 , Feng He 6 , Chris X. Lu 7 , Vito Guagnano 4 , Thomas Metz 8 , Peter M. Finan 1 , Francesco Hofmann 3 , William R. Sellers 2 , Jeffrey A. Porter 1 , Vic E. Myer1 , Diana Graus-Porta 3 , Christopher J. Wilson1 , Alan Buckler 1 , and Ralph Tiedt 3 Downloaded from cancerdiscovery.aacrjournals.org on September 28, 2021. © 2012 American Association for Cancer Research. Published OnlineFirst August 8, 2012; DOI: 10.1158/2159-8290.CD-12-0237 ABSTRACT The overall power of kinase inhibitors is substantially overshadowed by the acqui- sition of drug resistance. To address this issue, we systematically assessed the potential of secreted proteins to induce resistance to kinase inhibitors. To this end, we developed a high-throughput platform for screening a cDNA library encoding 3,432 secreted proteins in cellular assays. Using cancer cells originally dependent on either MET , FGFR2 , or FGFR3 , we observed a bypass of dependence through ligand-mediated activation of alternative receptor tyrosine kinases (RTK). Our fi ndings indicate a broad and versatile potential for RTKs from the HER and FGFR families as well as MET to compensate for loss of each other. We further provide evidence that combined inhibition of simultaneously active RTKs can lead to an added anticancer effect. SIGNIFICANCE: Although initial tumor responses to kinase inhibitors can be signifi cant, therapeutic ben- efi t is often limited by the emergence of resistance (e.g., as a consequence of mutations in the drug target or through activation of alternative pathways to bypass dependence on the original target). Because the activation of alternative growth-promoting kinases by stimulation with their cognate ligands can consti- tute such a bypass mechanism, the identifi cation of growth factors as possible mediators of resistance to kinase inhibitors is of clinical interest. Cancer Discov; 2(10); 1–12. ©2012 AACR. INTRODUCTION A well-characterized example representing both types of mechanisms is acquired resistance to the EGF receptor Genetic alterations, including point mutations, gene (EGFR) inhibitors gefi tinib and erlotinib in non–small cell amplifi cations, and chromosomal translocations, can render lung cancers carrying activating EGFR mutations ( 5, 6 ). In the kinases oncogenic ( 1, 2 ). The term “oncogene addiction” has majority of patients, this occurs either by emergence of the been used to describe the phenomenon in which growth and secondary resistance mutation T790M in EGFR or by loss of survival of cancer cells becomes dependent on an aberrantly EGFR dependence through activation of the receptor tyro- activated protein, for example, a kinase ( 3, 4 ). Oncogene sine kinase (RTK) MET ( 7–11 ). Although the EGFR-T790M addiction has been validated for several oncogenic “driver” mutation interferes with binding of EGFR inhibitors like kinases in preclinical models and in cancer patients using gefi tinib or erlotinib ( 12 ), MET activation can compensate selective kinase inhibitors. Despite striking initial clinical for loss of EGFR activity by activating an overlapping set activity, the emergence of resistance is becoming a common of downstream signaling molecules including HER3 that problem. One mechanism of resistance involves mutation continue to provide growth-promoting signals ( 8 ). Inter- of the target, thereby compromising binding and activity estingly, MET-driven resistance can occur because of MET of the therapeutic agent. Efforts to understand the specifi c gene amplifi cation ( 8 ) as well as activation by its ligand mechanisms of resistance to imatinib in chronic myelog- hepatocyte growth factor (HGF; refs. 10 , 13 ). On the other enous leukemia have led to second-generation inhibitors hand, it has been shown that MET-amplifi ed cancer cell (e.g., nilotinib) that treat and prevent resistance through lines that are sensitive to MET inhibitors can be rescued increased potency. However, the discovery of parallel or by ligand-induced EGFR activation ( 14 ). EGFR and MET downstream bypass mechanisms of resistance are motivat- are, therefore, considered to be alternative driver kinases ing novel combination therapies as a means to prevent such in the same cancer cells because dependence on one can be bypass events. compensated by activation of the other. In such a setting, simultaneous inhibition of both kinases or intervention at Authors’ Affi liations: 1 Developmental and Molecular Pathways and 2 Dis- a common downstream node is thus required for effective ease Area Oncology, Novartis Institutes for BioMedical Research, Cam- anticancer therapy. bridge, Massachusetts; 3 Disease Area Oncology and 4 Global Discovery Preclinical studies of resistance mechanisms have been Chemistry, Novartis Institutes for BioMedical Research, Basel, Switzerland; conducted using several experimental approaches, including 5 Oncology Translational Medicine, 6 Global Discovery Chemistry, and 7 Devel- opmental and Molecular Pathways, China Novartis Institutes for BioMedical random mutagenesis ( 15–17 ), prolonged drug exposure of sen- Research, Shanghai, PR China; and 8 Oncotest GmbH, Freiburg, Germany sitive cancer models to evoke outgrowth of resistant subclones Note: Supplementary data for this article are available at Cancer Discovery ( 18, 19 ), and expression of potential compensatory proteins in Online (http://www.cancerdiscovery.aacrjournals.org/). drug-exposed cancer cells using cDNA libraries ( 20 ). Prolonged F. Harbinski and V.J. Craig contributed equally to this work. drug-exposure experiments have successfully been used to Corresponding Author: Ralph Tiedt, Novartis Institutes for BioMedical recapitulate autocrine ligand–mediated resistance mechanisms Research, Klybeckstrasse 141, 4057 Basel, Switzerland. Phone: 41-61- that were previously found by hypothesis-driven testing ( 19 , 21 ). 696-1981; Fax: 41-61-696-5511; E-mail: [email protected] However, the potential role of the tumor microenvironment in doi: 10.1158/2159-8290.CD-12-0237 providing paracrine stimuli is not adequately modeled in such © 2012 American Association for Cancer Research. an experimental setup. The rationale for expressing cDNA OCTOBER 2012CANCER DISCOVERY | OF2 Downloaded from cancerdiscovery.aacrjournals.org on September 28, 2021. © 2012 American Association for Cancer Research. Published OnlineFirst August 8, 2012; DOI: 10.1158/2159-8290.CD-12-0237 RESEARCH ARTICLE Harbinski et al. libraries in drug-exposed cancer cells is that resistance to RTK growth compared to a neutral control (vector only). However, inhibitors can occur because of ligand-mediated activation of a small subset of supernatants was able to partially rescue the compensatory kinases. Such rescue ligands can be produced effect of MET inhibition and promote growth of MKN-45 by cancer cells themselves, leading to autocrine stimulation, in the presence of JAA120 ( Fig. 1B ). In line with previously or by stromal cells in the cancer microenvironment, leading to described concepts, members of the EGF family were among paracrine stimulation. the ligands that mediated MET inhibitor rescue ( Fig. 1B and To systematically assess the capability of secreted proteins Supplementary Table S2). In addition, we found that several to drive resistance to kinase inhibitors, we established a members of the fi broblast growth factor (FGF) family could high-throughput “secretome” screening platform. Secreted rescue MKN-45 cells. Among this family, FGF7-mediated proteins are produced in cell media supernatants by transfec- rescue was most pronounced ( Fig. 1B ). tion of a library encompassing 3,432 cDNAs. The resulting Similarly, secretome resistance screening was then carried supernatants are then screened for their potential to rescue out in 4 additional cancer cell lines in which MET activity kinase-dependent cancer cells that are simultaneously treated was known to be a major driver of cell growth. Also in these with a relevant kinase inhibitor. Specifi cally, supernatants additional lines, we observed that members of the EGF and/ leading to the reversal of inhibitor-mediated proliferation in or FGF families could suppress the growth effects of JAA120 MET-dependent and FGFR-dependent cancer cell lines were (Supplementary Table S2). These data suggest that down- discovered. Although the specifi c ligands of each inhibited stream signals emerging from either HER or FGFR family RTK were not capable of reversing growth inhibition, a sur- members that promote cell growth and survival are to some prisingly high degree of fl exibility was observed in bypassing extent qualitatively redundant with signals triggered by MET. oncogene addiction through activation of alternative RTKs. In particular, activation of HER family members could com- Secretome Screening Reveals Broad pensate for inhibition of either MET or FGFRs and activation Compensatory Potential of HER, FGFR, of FGFR or MET could cross-rescue HER inhibition. These and MET RTKs results suggest a specifi c and complementary role of these 3 Next, cancer cell lines that are dependent on a member growth factor pathways and suggest at least partial overlap of of the FGFR family