Epigenetics Compound Library Introduction Multipotent stroma
Introduction Multipotent stromal cells, also referred to as mesenchymal stem Epigenetics Compound Library (MSCs), are an heterogeneous subset of stromal cells present in several tissues including bone marrow, bone, adipose tissue, skin, kidney, umbilical cord and placenta (Friedenstein et al., 1968). The minimal criteria for defining MSCs are adherence to plastic surface; proliferation under the stimulus of fetal bovine serum; no expression of hematopoietic markers; expression of CD73, CD90, CD105, and differentiation into mesodermal cells (adipocytes, chondrocytes and osteocytes) (Dominici et al., 2006). MSCs are envisioned as an ideal tool for cell therapy since they home into injured tissues whereas they could differentiate into tissue-specific cells (Ezquer et al., 2011), manage oxidative stress (Valle-Prieto and Conget, 2010), release trophic factors (Caplan and Dennis, 2006), promote neovascularization (Ball et al., 2007) or trigger an anti-inflammatory response (Uccelli and Prockop, 2010). It has been shown that donor MSCs also home into stablished tumors where they interact with cancer stem cells, regulate neovascularization and modulate the immune response (Al Moustafa et al., 2002; Bolontrade et al., 2012). Currently, the role of MSCs in carcinogenesis is a matter of controversy. It has been reported that they favor tumor growth due to the immunosuppression (Djouad et al., 2003). Also, MSCs could enhance tumor metastatic potential since they can induce epithelia to mesenchyme transition (Huang et al., 2013). In contrast, it has been shown that MSCs inhibit tumorigenesis (Balasenthil et al., 2002a). The mechanisms apparently related to the antitumor effect could be: i) induction of cancer cell apoptosis (Ho et al., 2013), ii) avoidance of epithelium dedifferentiation (Ho et al., 2013), iii) inhibition of vascular network formation or apoptosis of vascular endothelial cells (Otsu et al., 2009; Secchiero et al., 2010), and iv) stimulation of anti-tumor immune response (Madrigal et al., 2014). Worldwide oral squamous cell carcinoma (OSCC) is the fifth most common epithelial cancer, its annual incidence is over 300,000 diagnosed cases and its annual mortality is about 145,000 deaths (Rivera, 2015). Despite advances in its detection and treatment the mortality of OSCC remains high and its five-year survival rate is among the lowest of the major cancers (Rivera, 2015). OSCC goes from normal keratinocyte transformation to random mutations linked to epigenetic processes that deregulate DNA repair mechanisms, cell cycle, cell differentiation and apoptosis (Rivera, 2015). Thus, normal tissue evolves progressively through hyperplasia, dysplasia and carcinoma in situ until reaching the stage of invasive carcinoma (Rivera, 2015; Dvorak et al., 2011; Nishimura et al., 2012; Choi and Chen, 2005; Mendez et al., 2002; Arora et al., 2005). The disease developed in the Syrian golden hamster using the mutagen 7.12-dimethylbenz-alpha-anthracene (DMBA) is a widely accepted animal model of OSCC (Chen et al., 2002; Nagini et al., 2009). It shares morphological, histological and molecular markers with human OSCC progression (Hasina et al., 2009; Ezquer et al., 2015; Aromando et al., 2014; Brandwein-Gensler et al., 2005). The aim of this work was to determine whether MSC administration at precancerous stage modifies the natural progression of OSCC. For this, OSCC was induced in hamsters by topical application of DMBA in the buccal pouch. At papilloma stage, the vehicle or 3×106 allogenic bone marrow-derived MSCs were locally administered. Four weeks later, the lesions were studied according to their: volume (macroscopy), histology (H&E staining), rate of proliferation (immunohistofluorescence for Ki67), rate of apoptosis (TUNEL), density of vasculature (immunohistofluorescence for ASMA), degree of inflammation (H&E and Toluidine blue staining), degree of differentiation (CK1 and CK4 immunohistofluorescence) and gene expression profile (RT-qPCR) (Supplementary Fig. 1).