Abstract 5182: CD47 is a promising therapeutic target in non-small cell lung cancer
Authors: Lau Asa P. , Kubli Shawn P. , Wakeham Andrew , Mak Tak W. , Thu Kelsie L. 
Published: April 2023

Introduction: Immune checkpoint inhibitors can elicit remarkable tumor regressions in non-small cell lung cancer (NSCLC), but not all patients are eligible for these drugs and only a small fraction of those who are respond. Thus, additional immunotherapies (IO) for NSCLC patients are needed. CD47 is an immunosuppressive protein frequently overexpressed in NSCLC. When bound to its receptor, SIRPα, the phagocytic function of antigen presenting cells (APCs) is impaired which dampens the innate immune response and anti-tumor immunity. CD47-SIRPα-targeted IOs are under investigation in clinical trials but little efficacy has been seen in solid tumours, suggesting further preclinical knowledge is needed to guide effective use in NSCLC. To address this need, we aim to decipher immune-mediated and cell-intrinsic mechanisms governing NSCLC response to CD47 inhibition.

Methods: CRISPR/Cas9 was used to generate mixed and clonal Cd47 knockout (KO) populations in two murine, syngeneic NSCLC models (LLC and CMT167). The effect of Cd47 inactivation on tumor cell fitness was assessed by multicolour competition assays conducted in vitro and in orthotopic tumors grown in immunocompetent C57BL/6 mice. Survival studies were also done in immune competent (C57BL/6) and deficient (NCG) mice to provide insights into cell-intrinsic versus immune-mediated effects of Cd47 KO on tumor growth. Immunophenotyping of tumours grown in syngeneic hosts was done using flow cytometry to compare immune cell infiltration in wildtype (WT) versus Cd47 KO tumors.

Results: Multicolour competition assays revealed that Cd47 LOF reduced the fitness of LLC and CMT167 cells grown in mice but not in cells grown in vitro, suggesting Cd47 KO does not compromise cell proliferation. Consistent with these results, survival studies conducted in immune competent hosts showed prolonged survival of mice with Cd47 KO compared to WT tumors in both models. An increase in activated Cd8+ cytotoxic T cells and M1-polarized macrophages was observed in Cd47 KO tumors relative to WT controls. Interestingly, the same survival studies conducted in immune compromised mice also showed a significant survival benefit for mice with Cd47 KO tumors, suggesting immune- and proliferation-independent, cell-intrinsic functions of Cd47 may also regulate NSCLC growth and progression.

Conclusions: Our results confirm the therapeutic potential of Cd47-targeted IO in NSCLC. The increased infiltration of anti-tumor lymphocytes and myeloid cells in Cd47 KO tumours supports a role for the immune system in mediating enhanced survival. However, because immune deficient mice with Cd47 KO tumors also exhibited a survival benefit, additional studies are required to deduce how Cd47-regulated cell-intrinsic mechanisms promote NSCLC biology. Our findings warrant further preclinical research to define effective anti-CD47 strategies for NSCLC.

Citation Format: Asa P. Lau, Shawn P. Kubli, Andrew Wakeham, Tak W. Mak, Kelsie L. Thu. CD47 is a promising therapeutic target in non-small cell lung cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5182.