One of the obstacles for cancer immunotherapy is the inefficiency of CD8+ T cell recruitment to tumors. STAT3 has been shown to suppress CD8+ T cells antitumor functions in various cancer models, in part by restricting accumulation of CD8+ T cells. However, the underlying molecular mechanism by which STAT3 in CD8+ T cells inhibits their accumulation in tumors remains to be defined. Here, we show that STAT3 signaling in CD8+ T cells inhibits chemokine CXCL10 production by tumor-associated myeloid cells via reducing IFNγ expression by T cells. We further demonstrate that ablating STAT3 in T cells allows expression of CXCR3, the receptor of CXCL10, on CD8+ T cells, resulting in efficient accumulation of CD8+ T cells at tumor sites. Blocking IFNγ or CXCR3 impairs STAT3-deficient CD8+ T cells' accumulation in tumor and their antitumor effects. Together, our study reveals a negative regulation by STAT3 signaling in T cells on myeloid cell-T cell crosstalk through IFNγ/CXCR3/CXCL10, which is important for CD8+ T cells homing to tumors. Our results thus provide new insights applicable to cancer immunotherapy and adoptive T cell strategies.
- Received January 14, 2015.
- Revision received May 11, 2015.
- Accepted May 20, 2015.
- Copyright © 2015, American Association for Cancer Research.