Dendritic cells (DCs) stimulated with triiodothyronine (T3) enhances antitumor immunity in a murine colon cancer model

SOLER MF; ALAMINO VA; GIUSIANO L; DONADIO, AC; PELLIZAS CG; MONTESINOS, MM

Aachen

Simposio; 15th International Symposium on Dendritic Cells; 2018

We previously reported that mice DCs express thyroid hormone receptor β1 and that physiological levels of T3 stimulates their maturation and ability to direct adaptive responses towards a Th1-type profile in vitro, as well as T cytotoxic and antitumoral effects in an in vivo model of B16-OVA melanoma (Mascanfroni et al, Faseb J 2008; JBC 2010; Alamino et al, Cancer Research 2015; Oncoimmunology 2016). Antitumor vaccination based on the own patient DCs, loaded ex-vivo with tumor antigens, aims to reduce or eradicate tumor cells. However, protocols deserve optimization since tumor cell cargo and DCs? functional state induced by maturation signals influence their in vivo immunogenic potential. Our aim was to analyze the anti-tumor efficacy of tumor antigen-loaded DCs matured by T3 in a murine colon cancer model. Colon cancer MC38 cells were UV-irradiated and the frequency of apoptotic and necrotic (Apo/Nec-MC38) cells was analyzed by AnnexinV/7-AAD assay (flow cytometry). Immature DCs (iDCs, control) or T3-stimulated DCs (T3-DCs) were incubated with Apo/Nec-MC38 cells for 18 h. DC?s intracellular and secreted IL-12 production were assayed by flow cytometry and ELISA, respectively. MC38 cells were s.c. injected on the left flank of C57BL/6 mice (day 0). Control or T3-DCs cultured with Apo/Nec-MC38 cells were s.c. injected on the right flank at days 1, 3, 5, 7 after tumor cell inoculation. Tumor size was measured using calipers (tumor volume = L×W2/2, L = length, W = width). Lymphocyte T linage was determined in tumor infiltrating cells and in splenocytes by flow citometry. Results: T3-DCs cultured with Apo/Nec-MC38 cells which constituted ~50% of cells that underwent apoptosis, produced higher amount of IL-12 than iDCs (p<0.01). Mice immunized with T3-DCs cultured with Apo/Nec-MC38 cells showed a significant decrease in tumor size (day 22, p<0.05). An increased number of infiltrating intratumoral CD8+ T cells in mice receiving T3-DCs cultured with Apo/Nec-MC38 cells vs control was revealed (p<0.05). Moreover, the immunotherapy based on T3-DCs decreased the frequency of Treg cells from splenocytes, assessed by a reduction of CD4+CD25+FoxP3+ cells (p<0.05). These results reinforce the adjuvant properties of T3-conditioned DCs as an alternative approach to potentiate T-cell-mediated tumor immunity reported in other murine tumor model and highlight the profound implications for cancer immunotherapy.