(162c) Enhancing Anti-PD-L1 Efficacy Against Murine Colon Cancer with Bilberry Anthocyanin Extracts

Through targeting immune checkpoints to unleash the power of adaptive immune response, immune checkpoint inhibitors (ICIs), such as anti-PD-1 and anti-PD-L1, are finding unprecedented applications in cancer treatment. Modulation of gut microbiota has been explored to improve the low response rate of ICIs in some cancer types. Here we report that the oral administration of bilberry anthocyanins extracts (BAE) helps to improve the anti-PD-L1 antibody efficacy against murine colon cancer. It is observed that the administration of BAE has enhanced intratumoral CD8⁺ T cell infiltrations and achieved the best control of tumor growth compared with the PD-L1 blockade alone. The application of BAE has increased the gut community diversity and enhanced the abundance of some beneficial bacteria, such as Lactobacillus johnsonii and Lachnospiraceae NK4A136 group. The significantly decreased proportion of aerobic bacteria and the obviously increased obligate anaerobes Clostridia when the anti-PD-L1 antibody was combined with bilberry anthocyanins, have suggested an improved intestinal anaerobic environment, which may be one of mechanisms for the modulation of the gut microbiome by anthocyanins. Whereas further study is needed to consolidate the prebiotic effects of anthocyanin and explore the underpinning mechanisms of enhanced tumor immune infiltration and the antitumor efficiency, above results reveal the opportunities of modulating gut microbiome by dietary intervention to augment the therapeutic efficiency of ICIs.