Abstract 2028: Spatially resolved proteomic profiling identifies tumor cell CD44 as a novel indicative biomarker of sensitivity to PD-1 axis blockade in advanced non-small cell lung cancer (NSCLC)
Authors: Moutafi Myrto , Molero Magdalena , Martinez-Morilla Sandra , Baena Javier , Vathiotis Ioannis , Gavrielatou Niki , Castro Laura , Ruiz de Garibay Gorka , Adradas Vera , Orive Daniel , Valencia Karmele , Galvo Alfonso , Montuenga Luis M. , Ponce Santiago , Schalper Kurt , Paz-Ares Luis , Rimm David L. , Zugazagoitia Jon 
Published: June 2022

Abstract
Introduction: Most patients with advanced NSCLC fail to develop durable responses from PD-1 axis blockade, and more robust predictive biomarkers are needed. In this study, we aimed to discover and validate spatially resolved protein markers associated with sensitivity to PD-1 axis inhibition across multiple NSCLC cohorts.
Methods: We first used the GeoMx Digital Spatial Profiling (DSP) system in a discovery cohort of 56 NSCLC patients treated with PD-1 axis inhibitors at Yale (USA). Pre-treatment tumors were represented in a tissue microarray (YTMA471) and analyzed using a 71-plex primary antibody panel. Proteins were measured from three molecularly defined tissue compartments: tumor (CK+), leukocytes (CD45+/CD68-), and macrophages (CD68+). We used quantitative immunofluorescence (QIF) to orthogonally validate candidate biomarkers. For external validation of identified predictors, we assessed pre-treatment whole tissue sections from a cohort of 128 NSCLC patients treated with single-agent PD-1 axis inhibitors at the Hospital 12 de Octubre (Madrid, Spain) using DSP (39-plex protein panel, measured from CK+ and CD45+ compartments). In addition, we analyzed two immunotherapy untreated cohorts to address prognostic significance: YTMA423 (Yale, USA; n = 252) and CIMA-CUN (UNAV, Spain; n = 124), using QIF and DSP respectively.
Results: Using continuous log-scaled data, we found 5 markers independently associated with progression-free survival (PFS) in the tumor compartment (including PD-L1, p = 0.002). Among the novel candidate predictors, tumor cell CD44, a marker of pluripotency and stemness, was associated with longer PFS (multivariate HR = 0.63, p= 0.002). Using QIF, we orthogonally validated that CD44 expression in the tumor compartment was associated with longer PFS (p &lt;0.001) and overall survival (OS) (p = 0.03). In the external validation cohort, CD44 expressed in the tumor compartment, but not in the immune compartment, was predictive of clinical benefit (OR 1.22, p = 0.018), and was significantly associated with longer PFS (first tertile cutpoint: HR 0.62, p = 0.03). In contrast, high CD44 expression was not associated with survival in the two untreated cohorts. Using DSP data from two cohorts, regions of interest with elevated expression of CD44 in tumor cells consistently showed prominent (Fold Change&gt;1.5, p&lt;0.05) upregulation of TIM-3, and PD-L1 and multiple co-stimulatory molecules (including CD40, ICOS, CD27).
Conclusion: This work highlights CD44 as a novel indicative biomarker of sensitivity to PD-1 axis blockade in NSCLC. NSCLCs with high CD44 expression in epithelial cells may be associated with an immune contexture primed for higher response to immune checkpoint blockade. Further studies are needed to understand the interplay between CD44+ cancer stem cell phenotype and mechanisms of immune evasion.
Citation Format: Myrto Moutafi, Magdalena Molero, Sandra Martinez-Morilla, Javier Baena, Ioannis Vathiotis, Niki Gavrielatou, Laura Castro, Gorka Ruiz de Garibay, Vera Adradas, Daniel Orive, Karmele Valencia, Alfonso Galvo, Luis M. Montuenga, Santiago Ponce, Kurt Schalper, Luis Paz-Ares, David L. Rimm, Jon Zugazagoitia. Spatially resolved proteomic profiling identifies tumor cell CD44 as a novel indicative biomarker of sensitivity to PD-1 axis blockade in advanced non-small cell lung cancer (NSCLC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2028.