BRAF V600E maintains proliferation, transformation, and tumorigenicity of BRAF-mutant papillary thyroid cancer cells.
BACKGROUND
Although the BRAF V600E mutant can initiate the formation of papillary thyroid cancer (PTC), it is unclear whether it is required to maintain cell proliferation, transformation, and tumor growth of BRAF mutation-harboring PTC.


OBJECTIVE
The aim of the study was to investigate whether BRAF V600E is required for the proliferation, transformation, and tumorigenicity of BRAF mutation-harboring PTC cells.


METHODS
We addressed this issue using BRAF small interference RNA (siRNA) to transfect stably several BRAF mutation-harboring PTC cell lines, isolated clones with stable suppression of BRAF, and assessed their ability to proliferate, transform, and grow xenograft tumors in nude mice.


RESULTS
PTC cell proliferation and transformation were suppressed in specific BRAF siRNA clones, but not in control scrambled siRNA clones. Specifically, taking the advantage of stable BRAF knockdown, we were able to show continued suppression of PTC cell proliferation and transformation, or anchorage-independent colony formation in soft agar, after long-term culture. Moreover, we also demonstrated that in vivo tumorigenicity and growth of tumors from the specific BRAF siRNA cell clones in nude mice were suppressed compared with control clones.


CONCLUSIONS
BRAF V600E is not only an initiator of PTC as demonstrated previously but is also a maintainer of proliferation, transformation, and tumorigenicity of PTC cells harboring BRAF mutation, and growth of tumors derived from such cells continues to depend on BRAF V600E. These results provide further support for potentially effective therapy targeted at BRAF for BRAF mutation-harboring PTC.
Liu
Dingxie
D
Division of Endocrinology and Metabolism, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
Liu
Zhi
Z
Condouris
Stephen
S
Xing
Mingzhao
M
D000818:Animals; D002291:Carcinoma, Papillary / Q000235:genetics / Q000473:pathology* / Q000628:therapy*; D002455:Cell Division; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic; D015972:Gene Expression Regulation, Neoplastic; D015316:Genetic Therapy / Q000379:methods*; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D017354:Point Mutation; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics* / Q000378:metabolism; D034741:RNA, Small Interfering; D013964:Thyroid Neoplasms / Q000235:genetics / Q000473:pathology* / Q000628:therapy*; D014162:Transfection; D014183:Transplantation, Heterologous
D034741:RNA, Small Interfering; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf