Abstract A066: TUSC2 immunogene therapy enhances checkpoint blockade through increased cytotoxic immune activation in chemo-resistant small cell lung cancer (SCLC) in humanized mice
Authors: Meraz Ismail M , Majidi Mourad , Song Renduo , Meng Feng , Gao Lihui , Wang Qi , Wang Jing , Shpall Elizabeth , Berger Mark , Kumar Hemant , Roth Jack A 
Published: December 2023

Immunotherapy has been effective but has had limited effect in clinical trials for SCLC. We identified TUSC2, a potent tumor suppressor gene, as a novel immunogene, which mediates both apoptosis and induces a strong antitumor immune response. TUSC2 expression is reduced in almost all SCLC tumors and absent in 41%.  We investigated the antitumor immune response to TUSC2 gene therapy in combination with immune checkpoint blockade (ICB) against a chemo-resistant inflamed SCLC tumors in humanized mice. Colony formation was markedly reduced in platinum resistant inflamed H841 cells transfected with TUSC2. Humanized mice were generated by transplanting fresh human cord blood derived CD34 stem cells into sub-lethally irradiated NSG mice(hu-NSG). The level of engraftment of human CD45, CD3 T, CD19 B, NK cells was verified before tumor implantation at &gt; 25%. Subcutaneous tumors were developed in hu-NSG mice and treated with intravenous injections of TUSC2 loaded cationic lipid nanoparticles (quaratusugene ozeplasmid abbreviated quar oze) with or without pembrolizumab (pembro; anti-PD1). A dramatic antitumor effect was mediated by quar oze, whereas pembro remained ineffective. A synergistic antitumor effect was found when quar oze was combined with pembro. The antitumor effect of the quar oze + pembro was associated with increased infiltration of human TILs, CD3 T, cytotoxic T, and NK cells, and a decreased number of human regulatory T (Treg) cells, and PD1 expressing exhausted CD8 T cells in the tumor microenvironment. Quar oze was also combined with atezolizumab (atezo; anti-PD-L1) and the antitumor effect on H841 lung metastases in hu-NSG mice was tested. Metastases were treated with quar oze and atezo alone or in combination. Although quar oze alone and atezo alone showed a strong antitumor effect in controlling metastases, a greater antitumor effect was found when quar oze was combined with atezo.  Infiltration of human CD45, CD3 T, CD8 T and NK cells increased in the quar oze and quar oze +atezo treated groups compared with others. A significantly higher number of CD8 T effector memory and lower number of naïve T cells were found in the quar oze +atezo which were associated with increased activated CD8 T cells (CD69+, PD1+ CD8 T cells). HLA-DR+ dendritic cells were increased, whereas myeloid derived suppressor cells were strongly inhibited by the combination. Quar oze was also combined with carboplatin+atezo which showed enhanced antitumor efficacy compared with carbo+atezo or quar oze alone. When quar oze was combined with carboplatin, a greater effect was found in inhibiting H841 cell growth, colony formation, and induction of apoptosis. Quar oze was combined with NPRL2, another tumor suppressor gene, in H841 tumors in humanized mice. Synergistic antitumor efficacy of the dual gene therapy occurred with the quar oze +NPRL2 treatment. Taken together, these data suggest that TUSC2 gene therapy in combination with ICB induces strong antitumor activity on a chemo-resistant inflamed SCLC through cytotoxic CD8 T and NK cell activation.

Citation Format: Ismail M Meraz, Mourad Majidi, Renduo Song, Feng Meng, Lihui Gao, Qi Wang, Jing Wang, Elizabeth Shpall, Mark Berger, Hemant Kumar, Jack A Roth. TUSC2 immunogene therapy enhances checkpoint blockade through increased cytotoxic immune activation in chemo-resistant small cell lung cancer (SCLC) in humanized mice [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A066.