Abstract 76: TUSC2 immunogene therapy enhances efficacy of chemo-immune combination therapy and induces robust antitumor immunity in KRAS-LKB1 mutant NSCLC in humanized mice
Authors: Meraz Ismail M. , Majidi Mourad , Shao RuPing , Meng Feng , Ha Min Jin , Shpall Elizabeth , Roth Jack A. 
Published: July 2021

Abstract
Oncogenic KRAS-LKB1 (KL)-mutant NSCLC lung cancers are resistant to immune checkpoint blockade (ICB) therapy due to impaired immunogenicity. Carboplatin plus ICB, the first line of treatment for NSCLC, showed limited efficacy on KL subtypes. TUSC2, a novel immunogene delivered systemically via nanovesicles, induces apoptosis in tumor cells and promotes a variety of innate and adaptive immune responses. We recently developed an improved humanized mouse that reconstitutes a human immune system in NSG mice by transplanting fresh human cord blood derived CD34+ stem cells (Hu-mice). In this study, we evaluated the antitumor immune response of a chemo-immunotherapy combination with TUSC2 on highly metastatic KL-mutant human lung cancer in Hu-mice. Hu-mice were challenged with A549 cells (Krasmt/LKB1-) and lung metastases were treated with TUSC2, nivolumab, or the combination. The results showed a synergistic antitumor effect with the combination. When TUSC2 was combined with pembrolizumab (pembro), a significant antitumor effect was also found, which was correlated with significantly higher levels of T, CD69+ active T, NK and CD69+ active NK and significantly lower levels of MDSC and Treg. Pembro alone significantly reduced tumor burden as compared with control whereas no antitumor effect was observed in non-Hu-mice. The chemo-immune (carbo+pembro) combination significantly reduced tumor burden over chemo or ICB alone. When TUSC2 was added to the chemo+immune combination, metastases regression was significantly greater than either TUSC2, TUSC2+pembro or carbo+pembro treatments. The triple combination in Hu-mice showed significant infiltration of cytotoxic T cells, NK cells and less infiltration of Treg into lung metastasis. The triple treatment also induced an antigen-specific T cell response, which was as shown by the presence of a significantly higher percentage of IFN-γ+ T cells in a co-culture with A549 cells. No IFN-γ+ T cells were found in a co-culture with control lung epithelial cells. Downregulation of PD-1 in TILs and upregulation of matured DC (MHCIIhi CD86+) was found in triple treatment. Significant enrichment of central memory (CM;CCR7+CD45RA-) and effector memory (EM;CCR7-CD45RA-) T cells in triple combination was observed. The EM and CM T cells were functionally active, and showed significantly higher capacity of releasing IFN-γ when stimulated with PMA. Similarly, TUSC2 also showed enhanced efficacy with carbo+aPD1 in highly metastatic KRASmt CMT167 in syngeneic mice. The antitumor effect was linked with increased infiltration of CD8+T, CD3+CD44+ and CD8+CD44+ memory T, NK cells and significantly less Treg cells in the tumor. In conclusion, the triple combination showed strong antitumor efficacy and induced robust antitumor immunity in KL-mutant NSCLC in clinically relevant Hu-mice supporting a clinical trial
Citation Format: Ismail M. Meraz, Mourad Majidi, RuPing Shao, Feng Meng, Min Jin Ha, Elizabeth Shpall, Jack A. Roth. TUSC2 immunogene therapy enhances efficacy of chemo-immune combination therapy and induces robust antitumor immunity in KRAS-LKB1 mutant NSCLC in humanized mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 76.