Abstract 2609: Vesicular LGALS3BP is a neuroblastoma biomarker and a therapeutic target for combination therapy with antibody-drug conjugate and checkpoint inhibitors

Abstract We have recently shown that targeting circulating LGALS3BP with a maytansinoid-based non-internalizing antibody-drug conjugate (ADC) resulted in tumor eradication of high-risk NMYC-amplified neuroblastoma patient-derived xenografts. LGALS3BP is a high molecular weight, hyperglycosylated and secreted protein which is enriched at the surface of cancer-derived extracellular vesicles (EVs). Here, using a neuroblastoma pseudometastatic preclinical model, we extended our previous work demonstrating that EVs-associated LGALS3BP strictly correlates with disease progression and dissemination. Moreover, to investigate whether LGALS3BP ADC, named 1959sss/DM4, possesses immune-modulating properties, we analyzed DM4 ability to induce immunogenic cell death (ICD). Interestingly, using NXS2 murine neuroblastoma cells, we found that DM4 induced a time-dependent surface expression of three different ICD marker, i.e. calreticulin, HSP70 and HSP90. As it was recently demonstrated that to limit immune surveillance NXS2 cells increase PD-L1 expression in response to IFNγ production in the tumor immune infiltrate, we evaluated potential synergism between LGALS3BP targeting ADC and an anti-PD1 immune check-point inhibitor. To this aim, we genetically manipulated NXS2 cells which resulted nearly negative for murine LGALS3BP expression. Therefore, using a lentivirus-based gene transduction system, we obtained NXS2 cells producing large amounts of vesicular human LGALS3BP. Of note, the vesicular LGALS3BP could be quantified by ELISA and imaged by confocal microscopy using 1959 antibody. Strikingly, while single agent treatment showed a limited antitumor activity in NXS2-LGALS3BP syngeneic model, the LGALS3BP ADC/anti-PD1 combination resulted in a marked inhibition of tumor growth, which was followed by a prolonged survival. In conclusion, our findings establish that vesicular LGALS3BP is a potential biomarker for liquid biopsy and reveals this protein as a suitable target for therapeutic strategy that combines 1959sss/DM4 ADC with immune checkpoint blockade for the treatment of LGALS3BP expressing neuroblastoma. Citation Format: Gianluca Sala, Emily Capone, Ilaria Cela, Giulio Lovato, Alessia Lamolinara, Manuela Iezzi, Cosmo Rossi, Vincenzo De Laurenzi, Rodolfo Ippoliti, Stefano Iacobelli. Vesicular LGALS3BP is a neuroblastoma biomarker and a therapeutic target for combination therapy with antibody-drug conjugate and checkpoint inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2609.