Abstract 5718: miRNA-629: A circulating exosomal biomarker of NK cell function
Authors: Lazdun Yelena , Greenlees Lydia M. , Pilataxi Fernanda , Rayanki Radhika , Streicher Katie 
Published: September 2020

Abstract
Antibody-dependent cell-mediated cytotoxicity (ADCC) of tumor cells is utilized in the treatment of various cancers, such as B cell lymphoma, breast cancer, colorectal cancer, and others; therefore, it is important to characterize biomarkers that identify patients who may respond better or worse to ADCC-based therapies. To do this, we used preclinical models to explore differences between those that are sensitive to in vitro ADCC and those that are not.
Multiple microRNAs were highly differentially expressed between cell lines of high sensitivity (n = 4) versus low sensitivity (n = 3) to in vitro ADCC with Inebilizumab; these microRNAs were pre-specified for testing in a Phase 1 trial of Inebilizumab in DLBCL. Of the microRNAs tested, only miR-629 displayed consistent results between in vitro and in vivo experiments. In vitro, there was a 12-fold (p &lt; 0.001) lower median expression in cell lines highly sensitive to in vitro ADCC with Inebilizumab. Importantly, diffuse large B cell lymphoma (DLBCL) patients who responded to Inebilizumab (CR/PR, N = 5) had significantly lower (7-fold; p &lt; 0.0001) median miR-629 expression compared to patients who did not respond (PD, N = 10).
To investigate the mechanism driving this clinical association, immune cell subsets were sorted from blood of DLBCL patients (n = 10) and normal donors. The greatest differential expression of miR-629 was found in the NK cell subset from DLBCL patients compared to normal (26-fold; p &lt; 0.01). Additionally, an effect on NK cell function was demonstrated by altering miR-629 levels in NK cell lines. Multiple genes important for NK activation (CD226, CTSD, TRADD, TNFa) were down-regulated (FC = 0.53 – 0.60) due to overexpression of miR-629, and up-regulated (FC = 1.6 – 2.5) following inhibition of miR-629. Inhibition of miR-629 also increased interferon-gamma and granzyme-b levels (30-40%; p &lt;0.05), ultimately leading to increased in vitro ADCC activity. Previous literature identified miR-629 in circulating exosomes from prostate cancer mouse models; therefore, we evaluated plasma from DLBCL (n = 20), as well as colon (n = 12) and breast cancer (n = 12), which are indications where ADCC therapeutics are part of the treatment paradigm. Results showed a range of miR-629 expression across all three tumor types (FC = 0 to ~500+), similar to that found in the Ph 1 DLBCL clinical trial. NK cells over-expressing miR-629 also showed a decreased killing capacity in ADCC assays with cetuximab and trastuzumab, as shown with Inebilizumab.
Together, this work reveals a role for miR-629 in altering NK function and highlights the potential to use miR-629 as a biomarker of response to ADCC-mediated therapeutics across multiple cancer indications. More detailed analyses of clinical outcome with miR-629 expression in larger trials will be necessary to confirm these results.
Citation Format: Yelena Lazdun, Lydia M. Greenlees, Fernanda Pilataxi, Radhika Rayanki, Katie Streicher. miRNA-629: A circulating exosomal biomarker of NK cell function [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5718.