VISUALIZATION OF HEAD AND NECK CANCER MODELS WITH A TRIPLE FUSION REPORTER GENE

The development of experimental animal models for head and neck tumors generally rely on the biol uminescence imaging to achieve the dynamic monitoring of the tumor growth and metastasis due to the complicated anatomical structures.Since the bioluminescence imaging is largely affected by the intracellular luciferase expression level and external D-luciferin concentrations,its imaging accuracy requires further confirmation.Here,a new triple fusion reportelr gene,which consists of a herpes simplex virus type 1 thymidine kinase(TK)gene for radioactive imaging,a far-red fuorescent protein(mLumin)gene for fuorescent imaging,and a firefly luciferase gene for bioluminescence imaging,was introduced for in vrivo observation of the head and neck tumors through multi-modality imaging.Results show that fuorescence and bioluminescence signals from mLumin and luciferase,respectively,were clearly observed in tumor cells,and TK could activate suicide pathway of the cells in the presence of nucleotide analog-ganciclovir(GCV),demonstrating the effecti veness of individual functions of each gene.Moreover,subcutaneous and metastasis animal models for head and neck tumors using the fusion reporter gene-expressing cell lines were established,allowing multi-modality imaging in vio.Together,the established tumor models of head and neck cancer based on the newly developed triple fusion reporter gene are ideal for monitoring tumor growth,assessing the drug therapeutic efficacy and verifying the effec-tiveness of new treatments.

Aberrant DNA methylation reprogramming during induced pluripotent stem cell generation is dependent on the choice of reprogramming factors

The conversion of somatic cells into pluripotent stem cells via overexpression of reprogramming factors involvesepigenetic remodeling. DNA methylation at a significant proportion of CpG sites in induced pluripotent stem cells(iPSCs) differs from that of embryonic stem cells (ESCs). Whether different sets of reprogramming factors influencethe type and extent of aberrant DNA methylation in iPSCs differently remains unknown. In order to help resolvethis critical question, we generated human iPSCs from a common fibroblast cell source using either the Yamanakafactors (OCT4, SOX2, KLF4 and cMYC) or the Thomson factors (OCT4, SOX2, NANOG and LIN28), and determinedtheir genome-wide DNA methylation profiles. In addition to shared DNA methylation aberrations present in all ouriPSCs, we identified Yamanaka-iPSC (Y-iPSC)-specific and Thomson-iPSC (T-iPSC)-specific recurrent aberrations.Strikingly, not only were the genomic locations of the aberrations different but also their types: reprogrammingwith Yamanaka factors mainly resulted in failure to demethylate CpGs, whereas reprogramming with Thomsonfactors mainly resulted in failure to methylate CpGs. Differences in the level of transcripts encoding DNMT3b andTET3 between Y-iPSCs and T-iPSCs may contribute partially to the distinct types of aberrations. Finally, de novoaberrantly methylated genes in Y-iPSCs were enriched for NANOG targets that are also aberrantly methylated insome cancers. Our study thus reveals that the choice of reprogramming factors influences the amount, location,and class of DNA methylation aberrations in iPSCs. These findings may provide clues into how to produce humaniPSCs with fewer DNA methylation abnormalities.