Dendritic cells engineered to express CD40L continuously produce IL12 and resist negative signals from Tr1/Th3 dominated tumors

TNF alpha-matured dendritic cells (DCs) pulsed with tumor antigens are being evaluated as cancer vaccines. It has been shown that DCs produce IL12 during a limited time span and subsequently enter a stage of IL12 exhaustion. If DCs are generated ex vivo, the patient could receive IL12-exhausted DCs which may be detrimental for stimulating anti-tumor Th1 responses. Furthermore, many cancer patients exhibit a cytokine profile skewed toward IL10 and TGF beta. This immunological profile, called the Tr1/Th3 response, is associated with the presence of regulatory T-cells. Tr1/Th3 responses potently inhibit DC maturation, thereby regulating Th1 responses. In the present study, we produced genetically engineered DCs that continuously express Th1-related cytokines such as IL12, and resist negative signals from Tr1/Th3-dominated bladder carcinoma cells. Human immature DCs were genetically engineered by adenoviral vectors to express CD40L, or were treated with TNF alpha as a positive control for maturation. The expression of different Th1/Th3 and inflammatory cytokines was monitored. IL12 and IFN gamma were expressed by CD40L-engineered DCs, while TNFa-matured DCs lacked IFN gamma and exhibited low IL12 expression. The addition of recombinant IL10 to genetically engineered DCs did not abolish their Th1 profile. Likewise, coculture with tumor cell lines expressing TGF beta with or without recombinant IL10 did not revert to the engineered DCs. We further demonstrate that the resistance of CD40L-expressing DCs to TGF beta and IL10 may be due to decreased levels of TGF beta and IL10 receptors. Thus, CD40L-engineered DCs are robust Th1-promoting ones that are resistant to Tr1/Th3-signaling via IL10 and TGF beta.