CXCR4 in epidermal keratinocytes: crosstalk within the skin.

In this issue, Takekoshi et al. investigated the role of CXCR4 in IL-23-induced keratinocyte hyperproliferation using an epidermal-specific knockout mouse model and found that CXCR4 limited keratinocyte proliferation. Some reports in the literature support this idea, whereas others contradict it; this disparity may be related to the differential roles of CXCR4 in various cell types or to a recently identified second receptor (CXCR7). Nevertheless, CXCR4 and its ligand SDF-1 have been implicated in skin wound healing, systemic lupus erythematosus, and basal cell carcinoma tumor angiogenesis. Further study is merited.