{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,6,8]],"date-time":"2026-06-08T15:59:34Z","timestamp":1780934374855,"version":"3.54.1"},"posted":{"date-parts":[[2026,6,4]]},"group-title":"Cancer Biology","reference-count":55,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,6,4]],"date-time":"2026-06-04T00:00:00Z","timestamp":1780531200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"funder":[{"name":"National Cancer Institute","award":["P30CA023074"],"award-info":[{"award-number":["P30CA023074"]}]},{"name":"National Cancer Institute","award":["P01CA229112"],"award-info":[{"award-number":["P01CA229112"]}]},{"name":"National Cancer Institute","award":["UG3CA290443"],"award-info":[{"award-number":["UG3CA290443"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,6,4]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                <jats:p>\n                  Cutaneous squamous cell carcinoma (cSCC) represents a growing public health burden, with incidence projected to increase 23\u201329% over the coming decade. Topical immunoprevention strategies targeting the\n                  <jats:monospace>PD-L1<\/jats:monospace>\n                  \/\n                  <jats:monospace>PD-1<\/jats:monospace>\n                  and\n                  <jats:monospace>TLR4<\/jats:monospace>\n                  axes have demonstrated preclinical efficacy, yet optimal intervention timing in humans remains undefined. To address this gap, single-cell RNA sequencing was performed on matched sun-protected (SP), sun-damaged (SD), and actinic keratosis (AK) biopsies from the same individuals, along with independent cSCC cases. Immune checkpoint and innate inflammatory signals were detectable as early as SD skin, prior to histologically confirmed dysplasia. Monotonically increasing expression of\n                  <jats:monospace>CD274<\/jats:monospace>\n                  (\n                  <jats:monospace>PD-L1<\/jats:monospace>\n                  ),\n                  <jats:monospace>CTLA4<\/jats:monospace>\n                  ,\n                  <jats:monospace>PDCD1<\/jats:monospace>\n                  ,\n                  <jats:monospace>CD27<\/jats:monospace>\n                  , and\n                  <jats:monospace>STAT1<\/jats:monospace>\n                  , alongside progressive\n                  <jats:monospace>TLR4<\/jats:monospace>\n                  \u2013\n                  <jats:monospace>MYD88<\/jats:monospace>\n                  innate immune signaling, was revealed through pseudobulk data analysis, with earliest upregulation at the SD stage. Fuzzy c-means trajectory clustering identified cell-typespecific programs across dendritic cells, macrophages, T cells, fibroblasts, endothelial cells, and keratinocytes. Dendritic cells shifted from early inflammatory antigen-presenting programs toward late\n                  <jats:monospace>PD-L1<\/jats:monospace>\n                  \/\n                  <jats:monospace>IFN<\/jats:monospace>\n                  -regulatory states; macrophages showed monotonically increasing\n                  <jats:monospace>TLR4<\/jats:monospace>\n                  -associated myeloid activation; and T cells defined a \u201chot but exhausted\u201d microenvironment in established cSCC. These findings identify SD and AK as biologically active stages for topical immunoprevention and provide a cellular roadmap for\n                  <jats:monospace>PD-L1<\/jats:monospace>\n                  \/\n                  <jats:monospace>PD-1<\/jats:monospace>\n                  and\n                  <jats:monospace>TLR4<\/jats:monospace>\n                  blockade strategies.\n                <\/jats:p>","DOI":"10.64898\/2026.06.01.729458","type":"posted-content","created":{"date-parts":[[2026,6,5]],"date-time":"2026-06-05T05:00:59Z","timestamp":1780635659000},"source":"Crossref","is-referenced-by-count":0,"title":["Single-Cell Transcriptomic Mapping of PD-L1\/TLR4 Remodeling Informs Topical Immunoprevention Timing in Skin Carcinogenesis"],"prefix":"10.64898","author":[{"ORCID":"https:\/\/orcid.org\/0009-0006-9196-2927","authenticated-orcid":false,"given":"Ran","family":"Wei","sequence":"first","affiliation":[{"name":"Department of Epidemiology and Biostatistics, Mel and Enid Zuckerman College of Public Health, The University of Arizona, Tucson, Arizona, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7208-0420","authenticated-orcid":false,"given":"Rudramani","family":"Pokhrel","sequence":"additional","affiliation":[{"name":"The University of Arizona Cancer Center, The University of Arizona, Tucson, Arizona, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3285-345X","authenticated-orcid":false,"given":"Delaney","family":"Stratton","sequence":"additional","affiliation":[{"name":"The University of Arizona Cancer Center, The University of Arizona, Tucson, Arizona, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0004-3619-4203","authenticated-orcid":false,"given":"Sara","family":"Centuori","sequence":"additional","affiliation":[{"name":"The University of Arizona Cancer Center, The University of Arizona, Tucson, Arizona, USA"},{"name":"College of Medicine Tucson, The University of Arizona, Tucson, Arizona, USA"},{"name":"Skin Cancer Institute, The University of Arizona, Tucson, Arizona, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8982-6252","authenticated-orcid":false,"given":"Clara","family":"Curiel-Lewandrowski","sequence":"additional","affiliation":[{"name":"The University of Arizona Cancer Center, The University of Arizona, Tucson, Arizona, USA"},{"name":"College of Medicine Tucson, The University of Arizona, Tucson, Arizona, USA"},{"name":"Skin Cancer Institute, The University of Arizona, Tucson, Arizona, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4799-8608","authenticated-orcid":false,"given":"Georg T.","family":"Wondrak","sequence":"additional","affiliation":[{"name":"The University of Arizona Cancer Center, The University of Arizona, Tucson, Arizona, USA"},{"name":"R. Ken Coit College of Pharmacy, The University of Arizona, Tucson, Arizona, USA"},{"name":"Skin Cancer Institute, The University of Arizona, Tucson, Arizona, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2049-543X","authenticated-orcid":false,"given":"Sally E.","family":"Dickinson","sequence":"additional","affiliation":[{"name":"The University of Arizona Cancer Center, The University of Arizona, Tucson, Arizona, USA"},{"name":"College of Medicine Tucson, The University of Arizona, Tucson, Arizona, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4939-9337","authenticated-orcid":false,"given":"Bonnie J.","family":"LaFleur","sequence":"additional","affiliation":[{"name":"The University of Arizona Cancer Center, The University of Arizona, Tucson, Arizona, USA"},{"name":"R. 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