Niche-Driven Overgrowth of KPC Figure 3. Increased expression of IL-6 and IL-17 in keloids. A, Cytokine expression profiling of keloid and matched normal skin tissue lysates by human cytokine antibody array. B, Determination of IL-17 levels in keloid and normal skin tissue lysates by ELISA (mean6SEM). * P,0.05. C, Immunohistochemical studies of IL-6 and IL-17 expression in keloid and matched normal skin tissues. Scale bars, 50 mm. D, Confocal immunofluorescence studies show co-localization of IL-17 around CD3+ cells as determined by dual-color staining. Scale bars, 100 mm. E and F, Western analysis of IL-17 (E) and IL-6 expression (F) in keloid tissues and matched normal skins. G and H, Expression of IL-6 and IL-6 receptor (IL-6R) in precursor cells derived from different keloid samples (K1, K2) and matched normal skins (N1, N2) as determined by Western blot (G) and RT-PCR analyses (H). I, Expression of IL-17 receptor (IL-17R) in precursor cells derived from different keloid samples (K1, K2) and matched normal skins (N1, N2) as determined by western blot and RT-PCR analyses. Data are representative of at least five independent experiments using KPCs and matched SKPs from different patient donors (n = 5). doi:10.1371/journal.pone.0007798.g003 Most recently, studies have shown that IL-6 participates in the lineage commitment of pathogenic IL-17-producing T helper cells (TH17 cells) from na¨ıve T cells [67–69]. On the other hand, IL-17 induces the secretion of IL-6 in a variety of cells including fibroblasts [44,50] and epithelial cells [51]. We then explored the interaction between IL-6 and IL-17 and determine whether the IL-17/IL-6 axis contributes to the regulation of the keloid niche. Our results showed that incubation with IL-17 enhanced IL-6 expression in both SKPs and KPCs (Figure 5A). However, exposure of KPCs to exogenous IL-6 failed to stimulate IL-17 secretion (data not shown). Similar to IL-6, IL-17 enhanced hTERT and Oct-4 expression in both SKPs and KPCs (Figure 5B). Treatment with IL-6 neutralizing antibody decreased the basal level of hTERT and Oct-4, and in conjunction with IL-17 antibody only slightly augmented the blockade of hTERT and Oct-4 expression in both SKPs and KPCs (Figure 5C). To further delineate the relationship of IL-6 and IL-17 in the regulation of hTERT and Oct-4 expression in SKPs and KPCs, we pretreated cells with neutralizing antibody for either IL-17, or IL-6, or both followed by IL-17 exposure. Our results indicated that IL-17- induced hTERT and Oct-4 expression was abolished by pretreatment with neutralizing antibody for either IL-17, or IL- PLoS ONE | www.plosone.org 8 November 2009 | Volume 4 | Issue 11 | e7798