<p>Squamous cell carcinoma in situ (SCCIS) is a prevalent precancerous lesion that can progress to cutaneous squamous cell carcinoma (cSCC). Although SCCIS is common, its pathogenesis remains poorly understood. To better understand SCCIS development, we performed laser-captured microdissection of human SCCIS and adjacent epidermis to isolate genomic DNA and RNA for next generation sequencing. Whole exome sequencing (WES) identified UV-signature mutations in multiple genes including Notch 1-3 (<a href="https://www.ncbi.nlm.nih.gov/gene/?term=4851">GeneID:4851</a>, <a href="https://www.ncbi.nlm.nih.gov/gene/?term=4853">GeneID:4853</a>, <a href="https://www.ncbi.nlm.nih.gov/gene/?term=4854">GeneID:4854</a>) in the epidermis and SCCIS and oncogenic TP53 (<a href="https://www.ncbi.nlm.nih.gov/gene/?term=7157">GeneID:7157</a>) mutations in SCCIS. Novel gene families, including SCHLAFEN genes, contained UV/oxidative-signature disruptive (UVD) epidermal mutations that manifested positive selection in SCCIS. The frequency and distribution of NOTCH and TP53 mutations indicate that NOTCH mutations may precede TP53 mutations. </p> <p>RNA sequencing identified 1166 differentially expressed genes; the top 5 enriched GO biological processes included: 1) immune response, 2) epidermal development, 3) protein phosphorylation, 4) regulation of catalytic activity, and 5) cytoskeletal regulation. The NEURL1 ubiquitin ligase, which targets Notch ligands for degradation, was upregulated in SCCIS. Neuralized 1 protein was found to be elevated in SCCIS suggesting that increased levels could represent a novel mechanism for downregulating Notch during UV-induced carcinogenesis. The data from DNA and RNA sequencing of epidermis and SCCIS provide insights regarding SCCIS formation. </p>

WES and RNA-Seq Analysis in Paired Sun-Exposed Epidermis and SCCIS Samples