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    Senescent fibroblasts in melanoma initiation and progression: an integrated theoretical, experimental, and clinical approach. Kim Eunjung,Rebecca Vito,Fedorenko Inna V,Messina Jane L,Mathew Rahel,Maria-Engler Silvya S,Basanta David,Smalley Keiran S M,Anderson Alexander R A Cancer research We present an integrated study to understand the key role of senescent fibroblasts in driving melanoma progression. Based on the hybrid cellular automata paradigm, we developed an in silico model of normal skin. The model focuses on key cellular and microenvironmental variables that regulate interactions among keratinocytes, melanocytes, and fibroblasts, key components of the skin. The model recapitulates normal skin structure and is robust enough to withstand physical as well as biochemical perturbations. Furthermore, the model predicted the important role of the skin microenvironment in melanoma initiation and progression. Our in vitro experiments showed that dermal fibroblasts, which are an important source of growth factors in the skin, adopt a secretory phenotype that facilitates cancer cell growth and invasion when they become senescent. Our coculture experiments showed that the senescent fibroblasts promoted the growth of nontumorigenic melanoma cells and enhanced the invasion of advanced melanoma cells. Motivated by these experimental results, we incorporated senescent fibroblasts into our model and showed that senescent fibroblasts transform the skin microenvironment and subsequently change the skin architecture by enhancing the growth and invasion of normal melanocytes. The interaction between senescent fibroblasts and the early-stage melanoma cells leads to melanoma initiation and progression. Of microenvironmental factors that senescent fibroblasts produce, proteases are shown to be one of the key contributing factors that promoted melanoma development from our simulations. Although not a direct validation, we also observed increased proteolytic activity in stromal fields adjacent to melanoma lesions in human histology. This leads us to the conclusion that senescent fibroblasts may create a prooncogenic skin microenvironment that cooperates with mutant melanocytes to drive melanoma initiation and progression and should therefore be considered as a potential future therapeutic target. Interestingly, our simulations to test the effects of a stroma-targeting therapy that negates the influence of proteolytic activity showed that the treatment could be effective in delaying melanoma initiation and progression. 10.1158/0008-5472.CAN-13-1720
    Characterization of serotonin and N-acetylserotonin systems in the human epidermis and skin cells. Slominski Andrzej T,Kim Tae-Kang,Kleszczyński Konrad,Semak Igor,Janjetovic Zorica,Sweatman Trevor,Skobowiat Cezary,Steketee Jeffery D,Lin Zongtao,Postlethwaite Arnold,Li Wei,Reiter Russel J,Tobin Desmond J Journal of pineal research Tryptophan hydroxylase (TPH) activity was detected in cultured epidermal melanocytes and dermal fibroblasts with respective Km of 5.08 and 2.83 mM and Vmax of 80.5 and 108.0 µmol/min. Low but detectable TPH activity was also seen in cultured epidermal keratinocytes. Serotonin and/or its metabolite and precursor to melatonin, N-acetylserotonin (NAS), were identified by LC/MS in human epidermis and serum. Endogenous epidermal levels were 113.18 ± 13.34 and 43.41 ± 12.45 ng/mg protein for serotonin (n = 8/8) and NAS (n = 10/13), respectively. Their production was independent of race, gender, and age. NAS was also detected in human serum (n = 13/13) at a concentration 2.44 ± 0.45 ng/mL, while corresponding serotonin levels were 295.33 ± 17.17 ng/mL (n = 13/13). While there were no differences in serum serotonin levels, serum NAS levels were slightly higher in females. Immunocytochemistry studies showed localization of serotonin to epidermal and follicular keratinocytes, eccrine glands, mast cells, and dermal fibrocytes. Endogenous production of serotonin in cultured melanocytes, keratinocytes, and dermal fibroblasts was modulated by UVB. In conclusion, serotonin and NAS are produced endogenously in the epidermal, dermal, and adnexal compartments of human skin and in cultured skin cells. NAS is also detectable in human serum. Both serotonin and NAS inhibited melanogenesis in human melanotic melanoma at concentrations of 10 -10  M. They also inhibited growth of melanocytes. Melanoma cells were resistant to NAS inhibition, while serotonin inhibited cell growth only at 10  M. In summary, we characterized a serotonin-NAS system in human skin that is a part of local neuroendocrine system regulating skin homeostasis. 10.1111/jpi.12626
    So You Can Teach Old Fibroblasts New Tricks. Virós Amaya,Girotti Maria Romina,Marais Richard Cancer discovery New data show that as dermal fibroblasts grow old, they increase their secretion of the WNT antagonist sFRP2 to drive melanoma cell metastasis. sFRP2 suppresses β-catenin and MITF signaling in melanoma cells, downregulating the redox regulator APE1, making melanoma cells more sensitive to oxidative stress and driving resistance to BRAF inhibitors. Thus, the aging microenvironment in elderly patient skin activates a signaling pathway that drives more aggressive melanoma cell behavior. Cancer Discov; 6(6); 581-3. ©2016 AACR. 10.1158/2159-8290.CD-16-0503
    Skin fibrosis. Identification and isolation of a dermal lineage with intrinsic fibrogenic potential. Rinkevich Yuval,Walmsley Graham G,Hu Michael S,Maan Zeshaan N,Newman Aaron M,Drukker Micha,Januszyk Michael,Krampitz Geoffrey W,Gurtner Geoffrey C,Lorenz H Peter,Weissman Irving L,Longaker Michael T Science (New York, N.Y.) Dermal fibroblasts represent a heterogeneous population of cells with diverse features that remain largely undefined. We reveal the presence of at least two fibroblast lineages in murine dorsal skin. Lineage tracing and transplantation assays demonstrate that a single fibroblast lineage is responsible for the bulk of connective tissue deposition during embryonic development, cutaneous wound healing, radiation fibrosis, and cancer stroma formation. Lineage-specific cell ablation leads to diminished connective tissue deposition in wounds and reduces melanoma growth. Using flow cytometry, we identify CD26/DPP4 as a surface marker that allows isolation of this lineage. Small molecule-based inhibition of CD26/DPP4 enzymatic activity during wound healing results in diminished cutaneous scarring. Identification and isolation of these lineages hold promise for translational medicine aimed at in vivo modulation of fibrogenic behavior. 10.1126/science.aaa2151