Tumor-Like Stem Cells Derived from Human Keloid Are Governed by the Inflammatory Niche Driven by IL-17/IL-6 Axis Qunzhou Zhang1, Takayoshi Yamaza1, A. Paul Kelly2, Shihong Shi1, Songlin Wang3, Jimmy Brown4, Lina Wang5, Samuel W. French6, Songtao Shi1*, Anh D. Le1* 1 Center for Craniofacial Molecular Biology, School of Dentistry, University of Southern California, Los Angeles, California, United States of America, 2 Department of Dermatology, King-Harbor Medical Center, Los Angeles, California, United States of America, 3 Salivary Gland Disease Center and the Molecular Laboratory for Gene Therapy, Capital Medical University School of Stomatology, Beijing, China, 4 Department of Otolaryngology, Head & Neck Surgery, Stanford University School of Medicine, Stanford, California, United States of America, 5 Department of Pathology, Kenneth Norris Jr. Cancer Center, University of Southern California Keck School of Medicine, Los Angeles, California, United States of America, 6 Department of Pathology, Harbor-UCLA Medical Center, Torrance, California, United States of America Abstract Background: Alterations in the stem cell niche are likely to contribute to tumorigenesis; however, the concept of niche promoted benign tumor growth remains to be explored. Here we use keloid, an exuberant fibroproliferative dermal growth unique to human skin, as a model to characterize benign tumor-like stem cells and delineate the role of their ‘‘pathological’’ niche in the development of the benign tumor. Methods and Findings: Subclonal assay, flow cytometric and multipotent differentiation analyses demonstrate that keloid contains a new population of stem cells, named keloid derived precursor cells (KPCs), which exhibit clonogenicity, self- renewal, distinct embryonic and mesenchymal stem cell surface markers, and multipotent differentiation. KPCs display elevated telomerase activity and an inherently upregulated proliferation capability as compared to their peripheral normal skin counterparts. A robust elevation of IL-6 and IL-17 expression in keloid is confirmed by cytokine array, western blot and ELISA analyses. The altered biological functions are tightly regulated by the inflammatory niche mediated by an autocrine/ paracrine cytokine IL-17/IL-6 axis. Utilizing KPCs transplanted subcutaneously in immunocompromised mice we generate for the first time a human keloid-like tumor model that is driven by the in vivo inflammatory niche and allows testing of the anti-tumor therapeutic effect of antibodies targeting distinct niche components, specifically IL-6 and IL-17. Conclusions/Significance: These findings support our hypothesis that the altered niche in keloids, predominantly inflammatory, contributes to the acquirement of a benign tumor-like stem cell phenotype of KPCs characterized by the uncontrolled self-renewal and increased proliferation, supporting the rationale for in vivo modification of the ‘‘pathological’’ stem cell niche as a novel therapy for keloid and other mesenchymal benign tumors. Citation: Zhang Q, Yamaza T, Kelly AP, Shi S, Wang S, et al. (2009) Tumor-Like Stem Cells Derived from Human Keloid Are Governed by the Inflammatory Niche Driven by IL-17/IL-6 Axis. PLoS ONE 4(11): e7798. doi:10.1371/journal.pone.0007798 Editor: Benjamin Edward Rich, Harvard Institute of Medicine, United States of America Received May 12, 2009; Accepted October 13, 2009; Published November 11, 2009 Copyright: 2009 Zhang et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported in part by National Institute of Health Research Grant, AR47359 (A. Le), 2P20 RR011145 (Pilot-A.P. Kelly), Oral and Maxillofacial Surgery Foundation Research Support Grant, OMSF002894 (Q. Zhang), California Institute for Regenerative Medicine (RN1-00572 for S. Shi), and USC Institutional funding (A. Le and Songtao Shi). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: anhle@usc.edu (ADL); songtaos@usc.edu (SS) Introduction Keloid is an exuberant scar unique to human with highest incidence in African-Americans, resembles benign tumor behavior by its aggressive dermal growth that continues to expand beyond the boundaries of the original wound margins (Figure S1A), rarely regresses as observed in hypertrophic scars [1], and recurs at a high rate after surgical removal [2]. A more tolerable and effective modality for keloid treatment is intralesional steroid injection, however, not applicable to very large or multiple keloids [3]. These dermal growths, similar to other fibroid tumors, could potentially reach a grotesque size in the craniofacial region with tremendous esthetic, functional, and psychologically debilitating sequelae [1]. As a chronic inflammatory and fibro-proliferative disease (Figure S1A), keloids exhibit distinctive histological features including a high density of mesenchymal cells, an abundant ECM stroma characterized of whorls of irregularly oriented and thickened hyalinized collagen bundles that are classically described as keloidal collagen [4], a local infiltration of inflammatory cells including mast cells and lymphocytes, and a milieu of enriched cytokines, especially transforming growth factor-b1 (TGF-b1) and IL-6 [5,6]. Clinically, keloids have been correlated with some degree of inflammatory response associated with tissue injury and most often, manifested clinically as a tender, painful, pruritic or burning sensation. We postulate that the altered or ‘‘pathological niche’’ driven by the inflammatory cytokine IL-17/IL-6 axis potentially regulates the benign, yet aggressive growth behavior of the dermal tumor. A recent study suggests that the interaction PLoS ONE | www.plosone.org 1 November 2009 | Volume 4 | Issue 11 | e7798