Abstract 5733: Versican proteolytic fragments (matrikines) synergize with STING agonists to elicit robust anti-tumor CD8+ T cell responses
Authors: Papadas Athanasios , Flietner Evan , Morrow Zachary , Wiesner Joshua , Cicala Alexander , Pagenkopf Adam , Hope Chelsea , Emmerich Philip , Deming Dustin , Zhang Jing , Hematti Peiman , Callander Natalie , Rakhmilevich Alexander , Otto Mario , Capitini Christian , Asimakopoulos Fotis 
Published: September 2020

Abstract
The impact of tumor matrix remodeling to the generation of an “inflamed” microenvironment that modulates responses to immunotherapy is unclear. Versican (VCAN) is a chondroitin sulphate matrix proteoglycan that promotes tolerogenic polarization of intratumoral DC through Toll-like receptor 2 (TLR2). Proteolytic processing of VCAN releases a bioactive N-terminal fragment (matrikine), versikine. In contrast to the tolerogenic actions of parental VCAN, versikine triggers IRF8-dependent transcription in myeloid cells and promotes Batf3-dendritic cell (DC) generation from FLT3L-mobilized bone marrow progenitors in vitro. Consistent with the Batf3-promoting effects of versikine, VCAN proteolysis correlates with T-cell infiltration across multiple cancers.The aims were to 1. define the impact of versikine on the intratumoral myeloid repertoire in vivo and 2. to define the efficacy of versikine as a vaccine adjuvant.4T1 breast carcinoma and Lewis Lung Carcinoma (LLC) empty vector (EV)- and versikine-expressing cells were implanted subcutaneously in syngeneic recipients. 1000mm3 tumors were harvested and intratumoral DC subsets were enumerated. Versikine-expressing tumors were characterized by significantly enhanced Batf3-DC (CD11chigh,MHC IIhigh Ly6C-, CD64-, CD24high,CD11blow) (p =0.0079 for 4T1 model and &lt;0.0001 for LLC model), whereas cDC2 (CD11chigh,MHC IIhigh Ly6C-, CD64-, CD24low, CD11bhigh ) frequency was diminished (p= 0.0079 and &lt;0.0001 respectively). Monocytic-derived DC (Mo-DC: CD11chigh, MHC IIhigh, Ly6C+, CD64+) remained unchanged. To determine the impact of versikine on responses to in situ vaccination using STING agonists, EV- and versikine-replete tumors (B16 and 4T1; 150 mm3), were injected intratumorally (IT) with a single subtherapeutic dose (200 μg) of DMXAA (murine STING agonist) or vehicle. EV-tumors did not significantly respond to 200μg DMXAA, whereas many B16-versikine and 4T1-versikine tumors regressed or growth was inhibited (p&lt;0.001 and p=0.014 respectively). Necrosis was frequently observed in 4T1 versikine-secreting tumors (6/9 mice) within 24 hours after treatment. Versikine extended survival after subtherapeutic DMXAA treatment in 4T1; log rank=p=0.01. Versikine's effects were abrogated in Batf3-null mice. To quantitate antigen-specific responses in the presence or absence of versikine, EV- and versikine-replete LLC tumors were injected IT with 500 μg DMXAA (therapeutic dose) or vehicle. We observed a significant increase in the frequency of CD8+ MHCI:SIINFEKL tetramer+ splenocytes in LLC-versikine-bearing animals as well as a marked increase in central memory T splenocytes (TCM) (CD62LhighCD44high). VCAN matrikines may generate effective adjuvants for in situ vaccination strategies across diverse solid and hematopoietic tumor types.
Citation Format: Athanasios Papadas, Evan Flietner, Zachary Morrow, Joshua Wiesner, Alexander Cicala, Adam Pagenkopf, Chelsea Hope, Philip Emmerich, Dustin Deming, Jing Zhang, Peiman Hematti, Natalie Callander, Alexander Rakhmilevich, Mario Otto, Christian Capitini, Fotis Asimakopoulos. Versican proteolytic fragments (matrikines) synergize with STING agonists to elicit robust anti-tumor CD8+ T cell responses [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 5733.