Sulindac reverses aberrant expression and localization of beta-catenin in papillary thyroid cancer cells with the BRAFV600E mutation.
BACKGROUND
Activation of the Wnt/beta-catenin signaling pathway is implicated in thyroid tumorigenesis, and up to 90% of papillary thyroid cancer (PTC) demonstrate aberrant expression of beta-catenin. Nonsteroidal antiinflammatory drugs reverse aberrant beta-catenin expression and localization in colon cancer. In this study, we tested the hypothesis that the nonsteroidal antiinflammatory drug sulindac would reverse aberrant beta-catenin activity in thyroid cancer cells.


METHODS
beta-catenin protein levels were determined in thyroidectomy specimens from six consecutive patients and in three different thyroid cancer cells lines (8505-C, KTC-1, and TPC-1) by immunoblotting. Cells of 8505-C and KTC-1 harbor the BRAF(V600E) mutation, and TPC-1 has the RET/PTC rearrangement. All cell lines were treated with sulindac (100 microM for up to 72 hours). Protein levels of c-myc and cyclin D1 were detected by immunoblotting, and beta-catenin localization was determined by immunocytochemistry in the PTC cell lines. PCCL3 rat thyroid cells that conditionally overexpress either BRAF(V600E) or RET/PTC were also treated with sulindac.


RESULTS
All PTC specimens and cell lines expressed high levels of beta-catenin protein and displayed aberrant nuclear and cytoplasmic localization of beta-catenin. Exposure to sulindac for 48 hours reduced beta-catenin expression in 8505-C and KTC-1 cells, but not in TPC-1 cells. Further, sulindac treatment reduced c-myc and cyclin D1 levels in 8505-C and KTC-1 cells, but had no effect in TPC-1 cells. Immunocytochemistry demonstrated that sulindac treatment redistributed beta-catenin from the nucleus to the membrane in 8505-C and KTC-1 cells. However, sulindac did not affect beta-catenin localization in TPC-1 cells. Finally, sulindac was effective in decreasing beta-catenin expression and cellular proliferation in BRAF(V600E)-overexpressing cells, but not in RET/PTC3-overexpressing cells.


CONCLUSIONS
Taken together, our findings demonstrate that sulindac treatment reverses beta-catenin activity in 8505-C and KTC-1 cell lines with the BRAF(V600E), but not in TPC-1 cells with the RET/PTC mutation. Future studies should investigate the potential for beta-catenin-directed therapy for patients with advanced thyroid cancers.
Cho
Nancy L
NL
Department of Surgery, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
Lin
Chi-Iou
CI
Whang
Edward E
EE
Carothers
Adelaide M
AM
Moore
Francis D
FD
Ruan
Daniel T
DT
D000231:Adenocarcinoma, Papillary / Q000235:genetics / Q000378:metabolism; D000818:Animals; D045744:Cell Line, Tumor; D006801:Humans; D009154:Mutation; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D051381:Rats; D013467:Sulindac / Q000494:pharmacology*; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000235:genetics / Q000378:metabolism*; D051176:beta Catenin / Q000096:biosynthesis / Q000235:genetics*
D051176:beta Catenin; D013467:Sulindac; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf