BRAFV600E Transduction of SV40-immortalized Normal Human Thyroid Cell Line Induces Dedifferentiated Thyroid Carcinogenesis in a Mouse Xenograft Model.

Affiliation

Seoul National University Seoul Metropolitan Government Boramae Medical Center, 65633, Department of Surgery, Seoul, Korea (the Republic of); [Email]

Abstract

Background: Despite active studies of the clinical importance of BRAFV600E, a suitable research model to investigate the role of this mutation in the etiopathogenesis of human thyroid cancers has not been established. Thus, we xenografted Nthy/BRAFWT (Nthy/WT) and Nthy/BRAFV600E (Nthy/V600E), which are Nthy-ori 3-1 (Nthy) cell lines transduced with lentiviral vectors expressing either BRAFWT or BRAFV600E, into mice to evaluate the carcinogenic role of BRAFV600E and establish a new in vivo research model for human thyroid cancer with BRAFV600E. Methods: Each cell line was subcutaneously injected into NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ mice, and a pathological analysis was performed. The effects of the mutation were further verified using a BRAFV600E-selective inhibitor (PLX-4032, vemurafenib). The transcriptome was analyzed by RNA-sequencing and compared to data from The Cancer Cell Line Encyclopedia and Gene Expression Omnibus. Results: While Nthy/WT was not tumorigenic in vivo, Nthy/V600E formed tumors reaching 2784.343 mm3 in 4 weeks, on average. A pathological analysis indicated that Nthy/V600E tumors were dedifferentiated thyroid cancer. We found metastases in the lung, liver, and relevant lymph nodes. A transcriptomic analysis revealed 5512 differentially expressed genes (DEG) between the mutant and wild-type cell lines, and more DEGs were shared with anaplastic thyroid cancer than with papillary thyroid cancer. BRAFV600E activated the cell cycle mainly by regulating G1/S phases. PLX-4032 treatment significantly inhibited tumor growth and metastasis. Conclusions: Our data show that BRAFV600E plays a pivotal role in carcinogenesis of normal human thyroid cell line. This xenograft model is expected to contribute to studies of the etiopathogenesis and treatment of highly malignant thyroid cancers.

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