Microarray analysis of ApcMin/+ and D6(ACKR2)-/-ApcMin/+ tumors

Mast cells have been suggested to either promote or suppress tumor progression but the mechanisms underlying these outcomes are unclear. Here, we show that mice with a heterozygous mutation in the adenomatous polyposis coli gene (ApcMin/+) displayed reduced intestinal tumor burden and increased survival in the background of the chemokine decoy receptor ACKR2 deficiency (ACKR2-/-). The ACKR2-/-ApcMin/+ tumors showed increased infiltration of mast cells. In mast cell-deficient Sash (c-kitW-sh/W-sh) ACKR2-/-ApcMin/+ mice the survival advantage was lost as the tumors grew rapidly and adoptive transfer of mast cells reduced the tumor burden in these mice. The tumor burden is also increased in Rag2-/-ACKR2-/-ApcMin/+ mice and the protection is reconstituted by adoptively transferred CD8+ T-lymphocytes. Mast cells from ACKR2-/- mice expressed elevated levels of chemokine receptors CCR2 and CCR5 and are also efficient in antigen presentation and activation of CD8+ T-cells. Mast cell-derived leukotriene B4 is a critical mediator of CD8+ T-lymphocyte recruitment as the BLT1-/-ACKR2-/-ApcMin/+ mice are highly susceptible to intestinal tumor induced mortality. Taken together, these data demonstrate that chemokine mediated mast cell recruitment is essential for initiating LTB4/BLT1 regulated CD8+ T-cell homing and generation of effective anti-tumor immunity against intestinal tumor development.

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