www.impactjournals.com/oncotarget/ Oncotarget, 2017, Vol. 8, (No. 13), pp: 22034-22047 Research Paper Tetraspanin 8 (TSPAN 8) as a potential target for radio- immunotherapy of colorectal cancer Aurelie Maisonial-Besset1,2,*,**, Tiffany Witkowski1,2,*,**, Isabelle Navarro-Teulon3,4,5, Odile Berthier-Vergnes6,7, Giovanna Fois2,8, Yingying Zhu9,10,11, Sophie Besse1,2, Olivia Bawa12, Arnaud Briat1,2, Mercedes Quintana1,2, Alexandre Pichard3,4,5, Mathilde Bonnet2,13, Eric Rubinstein9,10,11, Jean-Pierre Pouget3,4,5, Paule Opolon12, Lydia Maigne2,8, Elisabeth Miot-Noirault1,2, Jean-Michel Chezal1,2, Claude Boucheix9,10,11,*, Françoise Degoul1,2,* 1INSERM, U 1240, Clermont-Ferrand, France 2Université Clermont Auvergne, Imagerie Moléculaire et Thérapie Vectorisée, Clermont-Ferrand, France 3IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, France 4INSERM, U896, Montpellier, France 5Université Montpellier 1, Montpellier, France 6Université de Lyon 1, Lyon, France 7CNRS, UMR5534, Centre de Génétique et de Physiologie Moléculaires et Cellulaires, Villeurbanne, France 8CNRS/IN2P3, UMR6533, Laboratoire de Physique Corpusculaire (LPC), Clermont-Ferrand, France 9INSERM, UMR-S 935, Villejuif, France 10Université Paris-Sud 11, Orsay, France, 11Université Paris Saclay, Saint-Aubin, France, 12Gustave Roussy, Laboratoire de Pathologie Expérimentale, Villejuif, France 13INSERM U1071, Faculté de Médecine, Clermont Ferrand, France *These authors have contributed equally to this work **First co-authors Correspondence to: Françoise Degoul, email: [email protected] Keywords: TSPAN8, radioimmunotherapy, colorectal cancer, dosimetry Abbreviations: DOTA: 2,2’,2’’-(10-(2-((2,5-dioxopyrrolidin-1-yl)oxy)-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetic acid Received: December 12, 2016 Accepted: January 24, 2017 Published: February 28, 2017 ABSTRACT Tetraspanin 8 (TSPAN8) overexpression is correlated with poor prognosis in human colorectal cancer (CRC). A murine mAb Ts29.2 specific for human TSPAN8 provided significant efficiency for immunotherapy in CRC pre-clinical models. We therefore evaluate the feasability of targeting TSPAN8 in CRC with radiolabeled Ts29.2. Staining of tissue micro-arrays with Ts29.2 revealed that TSPAN8 espression was restricted to a few human healthy tissues. DOTA-Ts29.2 was radiolabeled with 111In or 177Lu with radiochemical purities >95%, specific activity ranging from 300 to 600 MBq/mg, and radioimmunoreactive fractions >80%. The biodistribution of [111In]DOTA-Ts29.2 in nude mice bearing HT29 or SW480 CRC xenografts showed a high specificity of tumor localization with high tumor/blood ratios (HT29: 4.3; SW480-TSPAN8: 3.9 at 72h and 120h post injection respectively). Tumor-specific absorbed dose calculations for [177Lu]DOTA-Ts29.2 was 1.89 Gy/MBq, establishing the feasibility of using radioimmunotherapy of CRC with this radiolabeled antibody. A significant inhibition of tumor growth in HT29 tumor-bearing mice treated with [177Lu]DOTA-Ts29.2 was observed compared to control groups. Ex vivo experiments revealed specific DNA double strand breaks associated with cell apoptosis in [177Lu]DOTA-Ts29.2 treated tumors www.impactjournals.com/oncotarget 22034 Oncotarget compared to controls. Overall, we provide a proof-of-concept for the use of [111In/177Lu] DOTA-Ts29.2 that specifically target in vivo aggressive TSPAN8-positive cells in CRC. INTRODUCTION receptors (e.g. small kinase inhibitors) [1]. Immunotherapy is an alternative approach relying on the use of monoclonal Communication between cells by direct or indirect antibodies that can specifically recognize and target antigens contact is a key process regulating tissue development and expressed on tumor cells. This interesting strategy has been homeostasis as well as recognition signals noticeably for successfully developed to target mainly EGFR and VEGF cells involved in innate and adaptative immune responses. in CRC with substantial responses [21,22]. Other antibodies Tetraspanins, a family of membrane proteins with 4 were developed against IGFR (ganitumab) or acting as transmembrane domains, are important actors in this process agonists of DR5 receptors (conatumumab) and tested in since these proteins can be found in both plasma membranes clinical trials without observed benefit [23]. Recently, a and exosomes [1]. Recent crystallographic structure of mouse monoclonal antibody Ts29.2 specific for human tetraspanin CD81 revealed a unique cone-like structure TSPAN8 was tested in preclinical models of CRC with with an intramembrane pocket filled with a cholesterol cell lines expressing different levels of TSPAN8 [19]. A molecule [2]. Remarkably, tetraspanins can control the significant slowdown of the tumor growth was observed but function of some cell surface proteins including integrins the molecular mechanisms involved in this process are not and a variety of other proteins involved in cell-cell and cell- yet fully elucidated. matrix interactions [3]. These intrinsic properties correlate The main drawback of immunotherapy is the poor with the involvement of Tetraspanins in several pathologies penetration of antibodies into solid tumors including CRC. such as cancers and exogenous infections [4]. Among the To circumvent this problem, conjugation of monoclonal 33 mammalian members of the Tetraspanins family, at least antibodies to α or β−-emitting radionuclides can significantly five of them, CD9, CD37, CD82, CD151 and TSPAN8, improve their therapeutic effects. Indeed, local irradiation are reported to display altered expression in cancers when of tumor cells in the range of the emitted particles can also compared to normal tissues [1,5]. The pro- or anti- cancer destroy neighboring cells exhibiting low antigen expression properties of CD9 is still controversial, while CD151 and or non-accessible to antibodies. Typically, antibodies can − TSPAN8 are assumed to display oncogenic activities. On the be radiolabeled with iodine-131 (β , Emax=606 KeV, 8.03 contrary, CD82 acts as a unique metastasis suppressor [1,5]. days) on their tyrosine residues. Nevertheless, in the case of Interestingly, CD37 protects against the development of B internalizing antibodies, this strategy can lead to a significant cell lymphoma by associating SOCS3 with IL-6 receptor and decreased dosimetry, due to metabolism generating then blocking IL-6 pathway [6]. TSPAN8 also named Co- free radioactive iodine or tyrosine radiometabolites that 029 is expressed on epithelial cells of some healthy tissues are easily excreted from cells [24]. Another interesting (mainly stomach, ileum/jejunum, colon/rectum and liver) [7]. strategy to create more metabolically stable entities is the It is expressed at high level in tumor tissues like esophagus labeling of antibodies with radiometals such as yttrium-90 − − [8], stomach [9], colon [10], liver [11], pancreas [12], ovary (β , Emax=2290 KeV, 2.67 days) or lutetium-177 (β , [13], and neo-expressed in invasive cutaneous melanomas Emax=490 KeV, 6.73 days). In these cases, the radionuclide [14]. TSPAN8 is known to be positively correlated with the is introduced into the protein scaffold via conjugation occurrence of metastases and bad prognosis [8,10,11]. Based of lysine or cysteine residues with chelating agents like on experimental data, several mechanisms were suggested DOTA. Such radioimmunotherapy (RIT) approaches have to explain the protumoral properties of TSPAN8. Indeed, it been largely developed with a radiolabeled anti-CD20 has been shown to be involved in cell adhesion and motility antibody (Zevalin®, [90Y]ibritumomab, tiuxetan) which is due to its interaction with cell adhesion molecules [10,15- currently available for the treatment of lymphomas resistant 18], in invasiveness by increasing ADAM12m expression to classical chemotherapy [25]. Despite [90Y]ibritumomab [8]. TSPAN8 also interferes with EGF signaling [9], induces good efficiency, clinicians do not favor this approach diffuse coagulopathy [15] and promotes angiogenesis due to practical issues such as nuclear department center through exosomes secretion [12]. Furthermore,TSPAN8- availability, price, some bone marrow toxicity and also specific antibodies reduce cell motility, angiogenesis, the development of other active treatments in lymphomas xenografted-tumor growth in nude mice and metastasis [26]. Interestingly, a CD37 antibody radiolabeled with incidence [10,12,13,19]. TSPAN8 mRNA has been also lutetium-177 ([177Lu]betalutin) is currently under clinical recently identified as a highly sensitive and specific blood evaluation (NCT01796171) for the management of patient biomarker for colorectal cancer (CRC) detection [20]. with relapsed CD37+ non-Hodgkin lymphomas [27]. Overall, these data argue that TSPAN8 could be viewed as a Although combination strategies recently developed promising therapeutic target in human carcinomas. in colon carcinomas allow substantial improvement in One strategy to counteract the pro-metastatic role clinical outcome, there is an urgent need to discover new of Tetraspanins can be the targeting of signaling pathways tumor-associated antigens as potential therapeutic targets. downstream Tetraspanin partners like integrins or other RIT approaches have also been tested in preclinical studies www.impactjournals.com/oncotarget 22035 Oncotarget on CRC with significant effect alone or in association with to 14 as determined by MALDI-TOF MS analyses. Further either antibodies usually targeting transmembrane proteins labeling of DOTA-Ts29.2