Abstract 2571: Sustained induction of TRAIL and granzyme B as well as intratumor infiltration of cytotoxic T lymphocytes (CTL) by a novel TLR7 agonist, DSR-6434, after systemic administration
Authors: Inagaki Ryosaku , Aoki Mikio , Kimura Toru , Hirose Yuko , Umehara Hiroki , Koga Erina , Murata Masashi , Wilkinson Robert W. , Robinson David T. , Jewsbury Philip J. , Li Chiang J. 
Published: May 2015

Although immediate responses after treatment of TLR7 agonist have been extensively characterized the genes that are directly responsible for the antitumor activity of TLR7 agonists have not been well identified. Moreover, the immediate responses to TLR7 agonist stimulation, such as induction of interferon-alpha, IP-10 and IL-1RA, generally diminish rapidly, and therefore, cannot be used as optimal pharmacodynamic (PD) biomarkers to monitor longer term PD effects. This study was undertaken to investigate the antitumor mechanism of TLR7 agonists and to identify novel PD biomarkers. To identify PD biomarkers, mice were inoculated with mouse renal carcinoma cell line, Renca, and were administered intravenously with DSR-6434 at 0.1 mg/kg once a week, 3 times. Total RNA samples were collected 2 hours or 5 days after final dose from tumor or blood. Global gene expression profiles in tumor or blood were analyzed using GeneChip Mouse Genome 430 2.0 array (Affymetrix). Differentially expressed genes by DSR-6434 were selected compared to vehicle, and pathway analysis was performed using the genes. Expression of TRAIL and granzyme B and its time course after the administration was investigated in peripheral blood leukocytes. In tumor of mouse model, 312 and 53 genes were upregulated and downregulated, respectively, more than 2 fold at 2 hours after DSR-6434 administration. The upregulated genes included those related to immune cell activation and apoptosis pathways. The upregulated immune-related genes included T-cell marker genes (Cd3g, Cd3e), marker genes of cytotoxic T-cells (CTL) (Cd8a), lymphocyte activation (Cd69), dendritic cells activation (Cd83 and Cd86) and cytotoxic factors against tumor (TRAIL and granzyme B). These results suggested that DSR-6434 induced infiltration and activation of CTL and production of cytotoxic factors at tumor site. At 5 days after the administration of TLR7 agonist DSR-6434, 4 genes, including TRAIL, remained upregulated in tumor. Surprisingly, upregulation of TRAIL and granzyme B in blood sustained for 3 or 6 days, respectively.

In conclusion, unbiased gene expression profiling has revealed that TLR7 agonist DSR-6434 triggers CD8+ cells infiltration into tumor and sustained increase of TRAIL and granzyme B in blood for at least 3 days, thus offering novel PD biomarkers that could potentially predict antitumor activity of TLR7 agonists.

Citation Format: Ryosaku Inagaki, Mikio Aoki, Toru Kimura, Yuko Hirose, Hiroki Umehara, Erina Koga, Masashi Murata, Robert W. Wilkinson, David T. Robinson, Philip J. Jewsbury, Chiang J. Li. Sustained induction of TRAIL and granzyme B as well as intratumor infiltration of cytotoxic T lymphocytes (CTL) by a novel TLR7 agonist, DSR-6434, after systemic administration. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2571. doi:10.1158/1538-7445.AM2014-2571