887 The chromosome 19 microRNA cluster facilitates TIL-based immune evasion in human melanoma

• DOI: 10.1136/jitc-2024-sitc2024.0887
• Publication Date: 2024-11-05T14:58:49Z
• Authors: Marian Smallin; MacLean Hall; John H Lockhart; Matthew Beatty; Varsha Devrapalli; Shari Pilon-Thomas; Andrew S Brohl
• Keywords: Evasion (ethics)

<h3>Background</h3> The Chromosome 19 MicroRNA Cluster (C19MC) is a group of 46 microRNAs that span approximately 100 Kb the human genome. C19MC exclusively expressed in placenta, regulating trophoblast migration and acting as an antiviral mechanism, but can become overexpressed cancers.¹ Additionally, has been hypothesized to suppress maternal immunity protect developing fetus.² We hypothesize cancer cells overexpress exploit this function evade anti-tumor immunity. Therefore, we are investigating how C19MC-overexpression facilitate immune evasion bolster oncologic fitness. <h3>Methods</h3> A tri-lentiviral infection CRISPRa ('Activation') system was used develop overexpressing melanoma cell line (526-C19), well nontargeted matched control (526-NT). parent 526 specifically due availability HLA-A-matched (MCC15781) tumor infiltrating lymphocytes (TILs) reactive line. overexpression confirmed using TaqMan RT-PCR panel. Immune killing assays were analyzed on Incucyte SX5. Antigen presentation rates lines identified flow panel HLA class I II pan-antibodies transcriptional analysis these performed SYBR RT-PCR. No-contact co-cultures 0.6 um Transwell plates or exosome-only media. TIL proliferation CellTrace Violet, survival Caspase GLO reagent, activation read through quantitative ELLA. <h3>Results</h3> 526-C19 exhibited reduced cytotoxic activity compared 526-NT direct co-culture experiments (80% vs. 60%, p = 0.0380) showed no difference when cultured alone. produced miRNAs found greater abundance exosomes than control. In no-contact experiments, observed increased intracellular levels co-cultured with relative those cells, suggesting transference C19 between via exosomes. directly indirectly demonstrated less proliferative activated phenotype. <h3>Conclusions</h3> leads decreased T cell-mediated death diminished fitness HLA-matched TIL, microRNA cluster may contribute tolerance cancer. <h3>References</h3> Setty BA, Jinesh GG, Arnold M,<i> et al</i>. genomic landscape undifferentiated embryonal sarcoma liver typified by structural rearrangement combined TP53 mutation loss. <i>PLoS Genet</i> 2020;<b>16</b>(4):e1008642. Bullerdiek J, Flor I. Exosome-delivered 'chromosome cluster' immunomodulators pregnancy tumorigenesis.<i> Mol Cytogenet</i> 2012;<b>5</b>(1):27. <h3>Ethics Approval</h3> MCC15781 approved USF IRB approval number Ame5_107905.