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br Conclusion The number of colonies at the first isolation
Conclusion
The number of colonies at the first isolation step could only represent a more or less rich ECFC content of the donor but we demonstrated that the initial clonogenicity was also related to distinctive intrinsic stemness, proliferative and functional features. Moreover, our results enabled linking ECFC stemness and their further functionality since the most immature cells, defined by a highly clonogenic and proliferative potential associated with the expression of specific stemness genes, were also the most angiogenic and released significantly more NO. The next step of our investigations will be to determine the significance of this profile in in vivo models of angiogenesis. Moreover, it is important to define more precisely the molecular mechanisms involved in ECFC immaturity through the study of the role of DNMT3b, GDF3 and SOX2 in these cells.
Finally, this study demonstrated the functional heterogeneity of CB-ECFCs and thus the need to identify criteria for selecting, first, the most functional neurokinin receptor antagonist and then, the blood units containing the most active progenitors, as for cord blood hematopoietic stem cell therapies. With the aim to investigate CB-ECFCs in the context of clinical studies, the establishment of a functional hierarchy of these cells should fit into a global optimization strategy in terms of isolation, culture and expansion. This also involves cryopreservation and serum replacement issues. Moreover, a recent report on the low immunogenicity of CB-ECFCs, demonstrated by their tolerance and preserved angiogenic potential in immunocompetent mice (Flex et al., 2016), could help to revive interest for allogenic grafts of cord blood EPCs which is for long neglected for autologous approaches.
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Acknowledgments
Introduction
Adenoid cystic carcinoma (ACC) is a deadly cancer: with a prevalence rate of 1224 cases, 918 patients die from ACC in the U.S. every year (http://www.accoi.org/faq/acc-statistics/). ACC is treated by surgery with or without radiation, but only 40% of patients survive 15years owing to intrinsic radiation resistance of ACC cells and their propensity to metastasize, relapse, and spread along nerves (Singh et al., 2015; Oplatek et al., 2010). The recurrence rate is high (53%) owing mostly to neural invasion, radio-resistance, and hematologic metastases (Shingaki et al., 1986).
Aggressive ACC behavior suggests that it may be driven by cancer stem cells (CSC). CSC possess properties of normal stem cells and are widely associated with invasion, recurrence, metastases, and resistance to cytotoxic therapies (Beck and Blanpain, 2013; Tysnes, 2010; Pattabiraman and Weinberg, 2014). Their identification in ACC will advance understanding of molecular etiology and cell of origin, improving diagnostics, predicting disease outcome, and developing effective therapies.
However, characterization of CSC is controversial when it is based solely on CD markers, whose expression is not stem cell-selective (Jaggupilli and Elkord, 2012). In addition, CSC isolated from cell cultures are often not representative of tumor tissue and therefore lack clinical value (Liu et al., 2014; Madjd et al., 2016; Leon et al., 2016). With the goal to identify clinically relevant CSC in ACC, we performed gene expression profiling of surgically resected tumor specimens to identify stem cell signaling and associated selective markers. This analysis demonstrated that most of ACC specimens selectively express SOX10, a marker of neural crest cells and oligonedroglial progenitors (Nonaka et al., 2008; Gorris et al., 2015), providing a clue to how CSC can be identified and isolated from ACC tissue. Indeed, in line with a special role of SOX10 in this cancer, we identified in the majority of ACC the expression of a highly conserved SOX10 gene signature that contained a cluster of neural stem cell drivers and markers, such as NOTCH1, MAP2, GPM6B, and FABP7, as well as genes/proteins involved in WNT and NOTCH signaling (Ivanov et al., 2013a; Ivanov et al., 2013b). These findings suggested that SOX10 expression delineates activation of a neural stem cell program in ACC and marks a previously unrecognized population of cells with neural stem cell properties.