Differential responses of human papillary thyroid cancer cell lines carrying the RET/PTC1 rearrangement or a BRAF mutation to MEK1/2 inhibitors.
OBJECTIVE
To examine the effects of 2 mitogen-activated protein kinase kinase (MEK1/2) inhibitors on papillary thyroid carcinoma (PTC) cell lines carrying the RET/PTC1 rearrangement or a BRAF mutation. In PTC, RET/PTC1 rearrangement or BRAF mutations results in constitutional activation of RET kinase or BRAF, respectively. Along the RET or BRAF signaling cascades, the activated RET kinase or BRAF activates MEK1/2, and then mitogen-activated protein kinases (extracellular signal-related kinase 1/2 [ERK1/2]) is activated. Activated ERK1/2 enters the nucleus and phosphorylates a variety of transcription factors, resulting in cancer cell proliferation. The MEK1/2 inhibitors, PD98059 and U0126, have been shown to inhibit cell growth in other cancers.


METHODS
In vitro study.


METHODS
Papillary thyroid carcinoma cell lines carrying the RET/PTC1 rearrangement (BHP2-7) or a BRAF mutation (BHP5-16).


METHODS
We treated PTC cells carrying the RET/PTC1 rearrangement or a BRAF mutation with 2 MEK1/2 inhibitors (PD98059 and U0126).


METHODS
Using Western blot analysis, we detected the expression of phosphorylated ERK1/2 and expression of cleaved poly(ADP-ribose) polymerase (PARP) in cells after treatment with either inhibitors. Growth inhibition was monitored by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.


RESULTS
Using Western blot analysis, we detected the dephosphorylation of ERK1/2 in PTC cells carrying the RET/PTC1 rearrangement or a BRAF mutation after treating the cells with 2 MEK1/2 inhibitors (PD98059 and U0126). In addition, both PD98059 and U0126 completely inhibited the growth of the PTC cells carrying a BRAF mutation but partially inhibited the growth of the PTC cells carrying the RET/PTC1 rearrangement. Finally, we observed PARP cleavage only in cells with a BRAF mutation in the Western blot analysis.


CONCLUSIONS
These data suggested that treatment with MEK1/2 inhibitors can be used as tools for inhibiting the growth of PTC cells.
Henderson
Ying C
YC
Department of Head and Neck Surgery, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
Fredrick
Mitchell J
MJ
Clayman
Gary L
GL
D002070:Butadienes / Q000494:pharmacology / Q000627:therapeutic use*; D002291:Carcinoma, Papillary / Q000188:drug therapy* / Q000235:genetics*; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D005419:Flavonoids / Q000494:pharmacology / Q000627:therapeutic use*; D015321:Gene Rearrangement; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors*; D009570:Nitriles / Q000494:pharmacology / Q000627:therapeutic use*; D010766:Phosphorylation; D017354:Point Mutation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D051096:Proto-Oncogene Proteins c-ret / Q000235:genetics*; D013964:Thyroid Neoplasms / Q000188:drug therapy* / Q000235:genetics*
D002070:Butadienes; D005419:Flavonoids; D009570:Nitriles; D047428:Protein Kinase Inhibitors; C113580:U 0126; D051096:Proto-Oncogene Proteins c-ret; C099282:RET protein, human; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D019950:Mitogen-Activated Protein Kinase 1; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one