Abstract 2907: Therapeutic targeting miR-146a and miR-21 induce malignant cell death and regulate CD8+ T-cell function in mycosis fungoides with large-cell transformation

Abstract Large cell transformation of mycosis fungoides (LCT-MF) occurs in 20-50% of advanced MF and is associated with an aggressive clinical course and poor survival not to overcome by any standard treatment regimen. We have previously identified a distinct miRNA expression profile in LCT-MF from that of non-transformed MF with significant upregulation of miR-21 and miR-146a. Our analyses demonstrated the involvement of genes for immune checkpoint pathways such as ICOS-ICOSL and PD1-PDL1 signaling (Di Raimondo C et al. Cancers 2021). Here, we aimed to investigate the efficacy of antagomiR-146a and -21 (amiR-146a, and -21) on the tumor growth and CD8+ tumor infiltrating lymphocyte exhaustion in LCT-MF. The amiR-146a, and -21 were synthesized in our DNA/RNA Synthesis Core by linking CpG-D19. In vitro, CTCL cell lines (Myla and HH) were treated with amiR-146a and -21, the cell viability was assessed by the 2,5-diphenyl-2H-tetrazolium bromide assay and cell apoptosis was evaluated using apoptosis assay. We found that amiR-146a, and -21 synergistically inhibited the proliferation of MyLa and HH cells due to the activation of apoptosis through Caspase3/7 pathways and inducing cell cycle arrest by blocking STAT3/CDK1/Cyclin B1 pathway. Our RNA-seq data indicated that the exhausted CD8+ T cells express elevated amounts of STAT3, IRF4, and BATF in LCT-MF compared with non-LCT MF. To evaluate the functional importance of amiR-146a, and -21 on CD8+ T cell exhaustion, we induced an exhausted state of CD8+ T cells with high level of immune checkpoints and dysfunctional cytokine production by continues anti-CD3/DC28 beads and culture supernatant (MyLa or HH cell) exposure. Our data revealed that amiR-146a and -21 attenuated the CD8+ T cell exhaustion by blockade of immune checkpoints and STAT3/IRF4/BATF pathway to trigger the cytotoxic immune response. Collectively, the findings of our study suggest that targeting miR-146a and -21 is a promising and novel therapeutic strategy for LCT-MF. Citation Format: Zhen Han, Piotr Swiderski, Xiwei Wu, Yate-Ching Yuan, Jun Wu, Chingyu Su, Hanjun Qin, Steven Rosen, Christiane Querfeld. Therapeutic targeting miR-146a and miR-21 induce malignant cell death and regulate CD8+ T-cell function in mycosis fungoides with large-cell transformation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2907.