Our results indicate that lysates derived from heat-shocked tumor cells are an optimal source of tumor-associated Ags, which are crucial for the generation of DCs with improved Ag cross-presentation capacity and clinically effective immunogenicity.

Background:The regulation of gap junction protein connexin 43 (Cx43), involved in natural killer (NK) cell-mediated tumor killing, is still elusive. Results: Hypoxia-induced autophagy selectively degrades gap junctional Cx43 from immune synapses and impairs NK-mediated melanoma cell lysis. Conclusion: A hypoxic microenvironment induces melanoma resistance to NK cells via modulation of Cx43 channels. Significance: Targeting autophagy prevents gap-junctional Cx43 degradation and potentiates NK-based tumor immunotherapies.

Gap junction (GJ) mediate intercellular communication through linked hemichannels from each of two adjacent cells. Using human and mouse models we show that connexin 43 (Cx43), the main GJ protein in the immune system, was recruited to the immunological synapse during T cell priming as both GJs and stand-alone hemichannels. Cx43 accumulation at the synapse was antigen-specific and time-dependent, and required an intact actin cytoskeleton. Fluorescence recovery after photobleaching and Cx43-specific inhibitors were used to prove that intercellular communication between T cells and DCs is bidirectional and specifically mediated by Cx43. Moreover, this intercellular crosstalk contributed to T cell activation as silencing of Cx43 with an antisense or inhibition of GJ docking impaired intracellular Ca2+ responses and cytokine release by T cells. These findings identify Cx43 as an important functional component of the immunological synapse and reveal a crucial role for GJs and hemichannels as coordinators of the DC-T cell signaling machinery that regulates T cell activation.