Dying breast cancer cells killed with 3-bromopyruvate stimulates dendritic cell activation mediated through Toll-like receptor 4 signaling
Kevin Lang1, Rachel Berrie1, Luis Quintero1, and James Hartmann1
1Florida Atlantic University, Boca Raton, Florida
Radiotherapy and some conventional chemotherapy cancer treatments in addition to directly eliminating cancer cells stimulate anti-tumoral immunity as dying cells activate dendritic cells (DCs). While this phenomenon has been shown for multiple chemotherapies, to our knowledge it is unknown if novel drugs that target abnormal cancer metabolism will induce similar cell death and stimulate DCs. Here we are the first to demonstrate that 3-bromopyruvate (3-BP), a molecule that inhibits glycolysis, has the capacity to elicit immunogenic death (ICD) that stimulate DCs.
We demonstrated that 3-BP-induced apoptosis in breast cancer cells stimulated immature DCs to produce high levels of the pro-inflammatory cytokine IL-12, increase expression of co-stimulatory molecules CD80 and CD86, and increased phagocytosis. DC activation was commensurate to that induced by mitoxantrone-treated breast cancer cells as mitoxantrone is a member of a class of anthracyclines known to induce immunogenic cell death and activate DCs. Treatment with 3-BP increased expression of calreticulin an “Eat me” signal on breast cancer cells and the extracellular release of the “danger signal” high mobility group box 1 protein (HMGB1), and both correlate with DC activation capacity in dying tumor cells. Concordantly, when toll-like receptor 4 (TLR4), a receptor for HMGB1 and initiator of one of the main pro-inflammatory signaling pathways, was blocked, 3-BP treated breast cancer cells were unable to stimulate DC activation.
Collectively, these results demonstrate that not only can chemotherapies elicit ICD in cancer, but additionally 3-BP can induce dying breast cancer cells to stimulate DC activation. We believe this is the first demonstrated by drugs that target abnormal tumor metabolism, and many such as 2-deoxyglucose are currently being investigated as therapies for cancer, further study of their immune activation capacities is merited.