Abstract LB139: The RNA signature of immune-related genes and distinct spatial distribution of immune cells are closely associated with the treatment outcomes in the malignant melanoma patients receiving immune checkpoint inhibitors
Authors: Kim Seoree , Jo Su In , Kim Sang-Yeob , Bae Dong-Jun , Kim Jeong-Oh , Shin Jeong-yeon , Kim Joo-re , Lee Cookjin , Chun Sang hoon , Park Gyeongsin , Kang Jin Hyoung 
Published: June 2022

Abstract
Introduction: The immune checkpoint inhibitors (ICIs) against CTLA-4 and PD-1/PD-L1, have improved survival with long-term durable response for advanced malignant melanomas. However, despite this success, only a minority of them respond to ICIs, with 10-40% objective response rate. The clinical experience with ICIs has identified several potential biomarkers associated with treatment efficacy, including tumor mutational burden, tumor-infiltrating lymphocytes, PD-L1 expression, and intestinal microbiota, but they still have not been useful in clinical practice. Our study aimed to investigate the influences of RNA gene signature and spatial distribution of immune cells on the treatment outcomes of malignant melanoma patients receiving ICIs.
Method Clinical: data were retrospectively collected malignant melanoma patients who had been treated with ICIs between Jan. 2016 and Dec. 2018 at Seoul St. Mary’s Hospitals. Among them, 23 cases with sufficient tumor tissue to examine RNA expression profile by NGS and the composition, and spatial distance of immune cells by multiplex immunofluorescent staining.
Results: The cell densities of T cells, cytotoxic T cells, Treg cells, CD8+Treg cells, and exhausted T cells in the good response group tended to be higher, which was clearer in the peritumoral (PT) area than the intratumoral (IT) area. Meanwhile, the cell densities of macrophage and activated M1 were significantly higher, which was more pronounced in the IT area than the PT area. For the good response group, M1/M2 ratio in the IT area was significantly higher compared to that of poor response group (p=0.045). The distribution (%) of cancer cells present at a close distance from T cells in the PT area was relatively higher in the good responders compared to that of the poor responders. In most cases, the distribution of cancer cells (%) present at a close distance from M1, M2, and NK cells tended to be higher in the IT area than PT area. For the cases with higher distribution of cancer cells at a close distance from M1 in the IT area, OS was significantly extended (p=0.036). For the cases with higher distribution of cancer cells at a close distance from NK cells in the IT area, PFS was significantly prolonged (p=0.057), but OS was not (p=0.324). The gene sets with relatively higher RNA expression in the good response group, were as follows; hematopoietic cell dedifferentiation gene, T-cell related adaptive immunity gene, interferon-related cytokine gene, and macrophage, NK, cell, T-cell innate immunity gene set. In the good response group, innate immune response (TLR7, PTPRC, CCL5), INFγ and JAK signaling molecules (CD8A, STAT1, CD86, IRF3, CXCL10, CXCL9, OAS1, IL10R α, IRF1, IFNAR2, CXCR3, PYHIN1, KIRK1, IFIH1) showed more than 2-folds increase of RNA expression. Meanwhile, in the poor response group, inflammatory immune response (CTSV, HMGB3, KIT, CDC4EP4, TRIM28), extracellular immune response (SPON1, SRPX, SOX10, SNAI2, LING01, LAMC3), fibrosis response genes (TGFβ2, TGFβ1) was increased.
Conclusion: Taken together, our results suggest that the distinguishing spatial distribution of T-cells, macrophages and NK cells and RNA signature of immune-related genes have close associations with therapeutic outcomes in malignant melanoma patients treated with ICIs.
Citation Format: Seoree Kim, Su In Jo, Sang-Yeob Kim, Dong-Jun Bae, Jeong-Oh Kim, Jeong-yeon Shin, Joo-re Kim, Cookjin Lee, Sang hoon Chun, Gyeongsin Park, Jin Hyoung Kang. The RNA signature of immune-related genes and distinct spatial distribution of immune cells are closely associated with the treatment outcomes in the malignant melanoma patients receiving immune checkpoint inhibitors [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 LB139.