ESTABLISHMENT OF VISIBLE ANIMAL METASTASIS MODELS FOR HUMAN NASOPHARYNGEAL CARCINOMA BASED ON A FAR-RED FLUORESCENT PROTEIN

Background and aims:The spectral properties of enhanced greenfluorescent protein(EGFP)used in current visualizable animal models for nasopharyngeal carcinoma(NPC)result in a limited imaging depth.Far-redfluorescent proteins have optimal spectral wavelengths that allow deep tissue penetration,thus are well-suited for the imaging of tumor growth and metastases in live animals.This study aims to establish an imageable animal model of NPC using far-redfluorescent proteins.Methods:Eukaryotic expression vectors of far-redfluorescent proteins,mLumin and Katushka S158A,were separately transfected into 5-8F NPC cells,and cell lines stably expressing the far-redfluorescent proteins were obtained.These cells were intraperitoneally or intravenously injected into mice,and their tumorigenic and metastatic potential were examined throughfluorescence imaging.Finally,factors affecting their tumorigenic ability were further assessed through testing side population(SP)cells proportion byflow cytometry.Results:NPC cell line with high tumorigenicity and metastasis(5-8F-mL2)was screened out,which stably expressed far-redfluorescent protein.Intraperitoneal and intravenous injection of 5-8F-mL2 cells resulted in an abdomen metastasis model and a lung metastasis model.In addition,NPC cell line without tumorigenicity(5-8F-Katushka S158A)was screened out.The percentage of SP cells between 5-8F-mL2 and 5-8F-Katushka S158A was found different,suggesting that the SP cell proportion may play a key role in the determination of cell tumorigenic ability.Conclusion:We successfully established animal models for NPC with high tumorigenicity and metastasis using a super-bright far-redfluorescent protein.Owing to the super-brightness and excellent wavelength parameters,these models may be applied as useful tools for intuitive and efficient monitoring of tumor growth and metastasis,as well as assessing the efficacy of nasopharyngeal cancer drugs.

Prediction of tumor biological characteristics in different colorectal cancer liver metastasis animal models using^(18)F-FDG and^(18)F-FLT

Background: Positron emission tomography(PET) is a noninvasive method to characterize different metabolic activities of tumors, providing information for staging, prognosis, and therapeutic response of patients with cancer. The aim of this study was to evaluate the feasibility of18F-fludeoxyglucose(18F-FDG) and 3’-deoxy-3’-18F-fluorothymidine(18F-FLT) PET in predicting tumor biological characteristics of colorectal cancer liver metastasis.Methods: The uptake rate of18F-FDG and18F-FLT in SW480 and SW620 cells was measured via an in vitro cell uptake assay. The region of interest was drawn over the tumor and liver to calculate the maximum standardized uptake value ratio(tumor/liver) from PET images in liver metastasis model. The correlation between tracer uptake in liver metastases and VEGF, Ki67 and CD44 expression was evaluated by linear regression.Results: Compared to SW620 tumor-bearing mice, SW480 tumor-bearing mice presented a higher rate of liver metastases. The uptake rate of18F-FDG in SW480 and SW620 cells was 6.07% ± 1.19% and2.82% ± 0.15%, respectively(t = 4.69, P = 0.04); that of18F-FLT was 24.81% ± 0.45% and 15.57% ± 0.66%, respectively(t = 19.99, P < 0.001). Micro-PET scan showed that all parameters of FLT were significantly higher in SW480 tumors than those in SW620 tumors. A moderate relationship was detected between metastases in the liver and18F-FLT uptake in primary tumors(r = 0.73, P = 0.0019).18F-FLT uptake was also positively correlated with the expression of CD44 in liver metastases(r = 0.81, P = 0.0049).Conclusions: The uptake of18F-FLT in metastatic tumor reflects different biological behaviors of colon cancer cells.18F-FLT can be used to evaluate the metastatic potential of colorectal cancer in nude mice.

Establishment of cervical lymph node metastasis model of squamous cell carcinoma in the oral cavity in mice

Background Oral squamous cell carcinoma （OSCC） is the most prevalent malignant tumor in the head and neck region, comprising more than 90% of all oral malignancies. A feasible approach for an animal model to study OSCC lymph node metastasis was established and biological behaviors of three oral squamous cell carcinoma cell lines were compared. Methods After implanting three kinds of cell lines （GDC185, Tca8113, Tca83） into three different anatomical sites in nude mice, namely the tongue, floor of the mouth, and axillary fossa, we observed the tumorigenicity and the metastatic capacity, which was confirmed by histopathology under a surgical microscope. Results The animal model injected with GDC185 cells into the floor of the mouth had the highest rate of neck lymph node metastasis （55.6%） and the cell lines had significantly different biological behaviors. Conclusions Nude mice injected with GDC185 cells into the floor of the mouth could be used as a feasible animal model to study neck metastasis of oral squamous cell carcinoma.

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.