After induction of tumors in Zfp36fl/fl and Zfp36ΔEP mice, we sorted EpCAM+CD45-CD140a-CD31- epidermal cells from papillomas at the same stage of development (as depicted in Supplemental Figure 3; supplemental material available online with this article; https://doi.org/10.1172/jci.insight.140669DS1). This evidence concerns the gene PDGFRA and papilloma.