Phenotypic and molecular comparative analysis of in vitro and in vivo behavior of stem cells populations from head and neck cancer

Abstract

The growth of solid tumors, as for normal tissues, appears to depend ultimately on a sub-population of self-renewing stem cells. Many cancer therapies rely on induction of cell death through DNA damage but increasing evidence indicates that cancer stem cells (CSCs) resist therapeutic killing based on this principle. Currently, however, there is very little information about differential effects of existing therapeutic modalities on CSCs and little is known about mechanisms that might enable CSCs elimination. Development and validation of effective in vitro model systems is therefore urgently required, both to avoid increasing animal usage and to facilitate research progress. Then, the present study purposes the comparison, at phenotypical and molecular level, of the in vivo and in vitro behaviour of CSC derived from fresh human head and neck squamous cell carcinomas, as well as in vivo transplanted tumors and their cells of origin grown in vitro as spheres or adherent culture. In view of that, cells supposed to be CSCs will be identified on these samples through their high levels of staining for CD44, as well as co-expression of CD133, CD29 and ESA. After, gene expression profile of identified CSCs from the four above-mentioned ways will be compared by cDNA microarray assay. Some differentially expressed genes will be selected for validation and correlation with the expression of a set of CSC markers, searching for specific patterns of CSC populations and its possible association with tumoral expansion and epithelial-mesenchymal transition. We expect that in vitro assays can be shown to provide rapid and reliable methods with broad applicability for assessing CSC responses. Further, we expect this to result in their adoption to replace currently proposed animal assays whose use is predicted to increase markedly unless suitable surrogate in vitro assays can be developed. Regarding gene expression studies, we believe that diagnostic and therapeutic conduct may be possible through the discovery of potential molecular targets of CSCs from head and neck cancer. (AU)