Inhibition of gastric cancer by a new controlled releasing compound of TLR-7/8 agonist via immune activation in a gastric cancer xenograft mice model.

Abstract

420 Background: TLR-7/8 agonist has been suggested to be an effective immunotherapeutic agent, possible systemic side effect has forbid its clinical usage. A new controlled-releasing compound of TLR-7/8 agonist was developed to overcome the limitations, and this study aimed to evaluate efficacy and safety of this new compound in xenograft mouse model using cell-lines derived from triple conditional (Tcon) mouse which develop gastric cancer spontaneously. Methods: A cell line was established by tumor tissue in Tcon mouse which was developed by activation of Kras and suppression of E-cadherin and P53. Tcon cell line was evaluated its growth rate, sensitivity to anticancer agents and in vivo tumorigenicity. Tcon cell line was subcutaneously injected to the flank of the syngeneic mice, and 5-FU and/or TLR-7/8 agonist were administered into 4 groups of mice (control group, 5-FU alone, TLR-7/8 agonist alone, and combination of 5-FU and TLR-7/8). 5-FU was administered i.p(intra-peritoneal) in once a week and TLR-7/8 agonist was injected i.t(intra-tumoral) 3 times a week. Tumor size and mouse weight were measured for drug efficacy and safety. Immune profile of the tumor was analyzed by fluorescence-activated cell sorting. Results: Tcon cell-line show a rapid growth with 24 hours of doubling time, and good in vivo tumorigenicity in syngeneic mice. Cell-line showed moderate sensitivity to 5-FU and paclitaxel but resistance to oxaliplatin. Tumors in 5-FU alone group showed slight decrease in size compared with that in control group, However, TLR-7/8 agonist alone and combination significantly inhibited tumor growth. Weight loss or any significant side effect was not observed in any group. In immune profiling, TLR-7/8 mono or combination group showed increased levels of infiltrating CD4, CD8 T cells, and recruited NK cell as well as significantly increase M1/M2 ratio of macrophages compared to 5-FU alone or control group. Conclusions: A new controlled releasing system of TLR-7/8 agonist with or without 5-FU showed a excellent tumor inhibition efficacy with low toxicity in gastric cancer xenograft model. The effect seemed to be through multiple immune activations including cell-mediated immune response, M1 macrophage polarization as well as innate NK cells.