Inflammatory chemokine CCL3 suppresses preferential tumor-associated accumulation of B cells and CD4 T cells in tumor-draining lymph nodes (P2017)

Abstract

Abstract We have previously demonstrated that CCL3 (MIP-1α) and CCL4 (MIP-1β) were important in orchestrating cellular contacts in vaccinated lymph nodes (LNs) and can enhance memory T cell generation (Castellino et al). We hypothesize that incorporating CCL3 and CCL4 into tumor vaccines can enhance anti-tumor immunity. Using colon tumor model CT26, we generated tumors that secret CCL3, CCL4 or both, and inoculate them live into the footpad of naïve recipients. CCL3-secreting tumors failed to grow in immunocompetent mice, and enhance antitumor immunity when used as a vaccine. Flow cytometric analysis of draining popliteal LNs 3 days after live cell injection revealed that while the total LN cell number increased by 2.03 fold after wild type (WT) tumor challenge relative to contralateral LN (conLN), CCL3-secreting tumor injection failed to do so despite the presence of tumor cells in the LNs. CD4 cells in the WT draining LN were 1.58 fold higher compared to conLN, but remained unchanged in CCL3-secreting tumors. Striking differences were seen in B cells where WT tumor resulted in a 7.04-fold increased, but CCL3-secreting tumors only caused a modest 2.04-fold change. Dynamic intravital 2-photon microscopy and tissue histology studies further revealed that tumors occupy the B cell follicle during early metastasis, and exogenous CCL3 gradient may potentially alter lymphocyte homeostasis in tumor draining LN, resulting in immune activation rather than tolerance against CT26.