Targeting BRAFV600E with PLX4720 Displays Potent Antimigratory and Anti-invasive Activity in Preclinical Models of Human Thyroid Cancer

Carmelo Nucera; Matthew A. Nehs; Sushruta S. Nagarkatti; Peter M. Sadow; Michal Mekel; Andrew H. Fischer; Paul S. Lin; Gideon E. Bollag; Jack Lawler; Richard A. Hodin; Sareh Parangi

doi:10.1634/theoncologist.2010-0317

Targeting BRAF^V600E with PLX4720 Displays Potent Antimigratory and Anti-invasive Activity in Preclinical Models of Human Thyroid Cancer

^aThyroid Cancer Research Laboratory, Endocrine Surgery Unit, and
^bDepartment of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA;
^cDepartment of Pathology, University of Massachusetts, Worcester, Massachusetts, USA;
^dPlexxikon Inc., Berkeley, California, USA;
^eDivision of Cancer Biology and Angiogenesis, Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA

Correspondence: Sareh Parangi, M.D., Harvard Medical School, Massachusetts General Hospital, Unit of Endocrine Surgery, Wang ACC 460, 15 Parkman Street, Boston, Massachusetts 02115, USA. Telephone: 617-643-4806; Fax: 617-643-4802; e-mail: sparangi{at}partners.org

Received September 19, 2010.
Accepted January 20, 2011.
First published online in THE ONCOLOGIST Express on February 25, 2011.

Disclosures: Carmelo Nucera: None; Matthew A. Nehs: None; Sushruta S. Nagarkatti: None; Peter M. Sadow: None; Michal Mekel: None; Andrew H. Fischer: None; Paul S. Lin: Employment/leadership position: Plexxikon Inc.; Ownership interest: Plexxikon Inc.; Gideon E. Bollag: Employment/leadership position: Plexxikon Inc.; Intellectual property rights/inventor/patent holder: filings through Plexxikon Inc.; Ownership interest: Plexxikon Inc.; Jack Lawler: None; Richard A. Hodin: None; Sareh Parangi: None.

The content of this article has been reviewed by independent peer reviewers to ensure that it is balanced, objective, and free from commercial bias. No financial relationships relevant to the content of this article have been disclosed by the independent peer reviewers.

Abstract

Purpose. B-Raf^V600E may play a role in the progression from papillary thyroid cancer to anaplastic thyroid cancer (ATC). We tested the effects of a highly selective B-Raf^V600E inhibitor, PLX4720, on proliferation, migration, and invasion both in human thyroid cancer cell lines (8505c^B-RafV600E and TPC-1^{RET/PTC-1 and wild-type B-Raf}) and in primary human normal thyroid (NT) follicular cells engineered with or without B-Raf^V600E.

Experimental Design. Large-scale genotyping analysis by mass spectrometry was performed in order to analyze >900 gene mutations. Cell proliferation and migration/invasion were performed upon PLX4720 treatment in 8505c, TPC-1, and NT cells. Orthotopic implantation of either 8505c or TPC-1 cells into the thyroid of severe combined immunodeficient mice was performed. Gene validations were performed by quantitative polymerase chain reaction and immunohistochemistry.

Results. We found that PLX4720 reduced in vitro cell proliferation and migration and invasion of 8505c cells, causing early downregulation of genes involved in tumor progression. PLX4720-treated NT cells overexpressing B-Raf^V600E (heterozygous wild-type B-Raf/B-Raf^V600E) showed significantly lower cell proliferation, migration, and invasion. PLX4720 treatment did not block cell invasion in TPC-1 cells with wild-type B-Raf, which showed very low and delayed in vivo tumor growth. In vivo, PLX4720 treatment of 8505c orthotopic thyroid tumors inhibited tumor aggressiveness and significantly upregulated the thyroid differentiation markers thyroid transcription factor 1 and paired box gene 8.

Conclusions. Here, we have shown that PLX4720 preferentially inhibits migration and invasion of B-Raf^V600E thyroid cancer cells and tumor aggressiveness. Normal thyroid cells were generated to be heterozygous for wild-type B-Raf/B-Raf^V600E, mimicking the condition found in most human thyroid cancers. PLX4720 was effective in reducing cell proliferation, migration, and invasion in this heterozygous model. PLX4720 therapy should be tested and considered for a phase I study for the treatment of patients with B-Raf^V600E ATC.