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Conventional type 1 dendritic cells (cDC1s) play a crucial role in antitumor immunity through the induction and activation of tumor‐specific CD8+ cytotoxic T cells (CTLs). The chemokine XCL1 is a major chemotactic factor for cDC1s and its receptor XCR1 is selectively expressed on cDC1s. Here, we investigated the effect of intratumoral delivery of a highly active form of murine XCL1 (mXCL1‐V21C/A59C) on cDC1‐mediated antitumor immunity using a hydrophilic gel patch. The hydrophilic gel patch containing mXCL1‐V21C/A59C increased cDC1 accumulation in the tumor masses and promoted their migration to the regional lymph nodes, resulting in enhanced induction of tumor‐specific CTLs. Tumor‐infiltrating cDC1s not only expressed XCR1 but also produced CXCL9, a ligand for CXCR3 which is highly expressed on CTLs and NK cells. Consequently, CTLs and NK cells were increased in the tumor masses of mice treated with mXCL1‐V21C/A59C, while immunosuppressive cells such as monocyte‐derived suppressive cells and regulatory T cells were decreased. We also confirmed that anti‐CXCL9 treatment decreased the tumor infiltration of CTLs. The intratumoral delivery of mXCL1‐V21C/A59C significantly decreased tumor growth and prolonged survival in E.G7‐OVA and B16‐F10 tumor‐bearing mice. Furthermore, the antitumor effect of mXCL1‐V21CA59C was enhanced in combination with anti‐programmed cell death protein 1 treatment. Finally, using The Cancer Genome Atlas database, we found that XCL1 expression was positively correlated with tumor‐infiltrating cDC1s and a better prognosis in melanoma patients. Collectively, our findings provide a novel therapeutic approach to enhance tumor‐specific CTL responses through the selective recruitment of CXCL9‐expressing cDC1s into the tumor masses. [ABSTRACT FROM AUTHOR]

Ice-breeding seals use vocal communication mainly during breeding season. The vocal function of aquatic mating, ice-associated ribbon seals (Histriophoca fasciata) has been unknown since they produce sounds in both breeding and non-breeding seasons. We examined the timing of their vocal presence in relation to environmental factors to infer the function of their calls in the Nemuro Strait, northern Japan, since this area is the possible southern limit of their breeding range. Vocalizations of ribbon seals were irregularly sampled from November 2012 to March 2014 in the Nemuro Strait and were compared with sea ice presence, time of day, and tidal currents. Ribbon seal downsweeps were detected in February 2013 and March 2014 only when sea ice was present along the Shiretoko Peninsula in the strait, with more detections in March leading up to the spring breeding season. Downsweep detections decreased in the middle of the day, indicating that ribbon seals were likely to be hauled out during this time. Vocalizing at night and early morning would probably reflect the increased opportunity for attracting females underwater. Our study suggests that the seal vocalizations in concurrence with sea ice presence in the Nemuro Strait could function as underwater communication for breeding. [ABSTRACT FROM AUTHOR]