Single nucleotide polymorphisms in matrix metalloproteinase 2 (MMP2) enhance BRAFV600E mutation-mediated oncogenicity and invasiveness of papillary thyroid cancer cells

Abstract

Thyroid cancer is a common endocrine neoplasm. Despite its good prognosis, it can lead to significant morbidity and mortality due to metastasis and recurrence. However, the factors involved in metastasis are not well studied. Therefore, we selected matrix metalloproteinases 2 (MMP2) and determined whether it has any role in thyroid cancer. We sequenced the exons of MMP2 in 211 samples including 16 multi-nodular goiters and 195 differentiated thyroid cancers. We identified four non-synonymous single nucleotide polymorphisms (SNPs) of the MMP2 gene in 3.06% (6/195) thyroid cancers. Of the four tumors harboring MMP2 SNPs, three (75%) concomitantly had BRAFV600E. Hence, we speculated that the MMP2 SNPs may cooperate with BRAFV600E in promoting tumor aggressiveness. Overexpression of two MMP2 SNPs (P38L and T458I) exhibited markedly enhanced gelatinase activity with an intact dimerization and induced strong cortactin foci formation in HEK293T cells. Stable expression of the two MMP2 SNPs in BRAFV600E positive BCPAP cells dramatically enhanced cell proliferation, colony formation, and focus formation. Analysis of the morphology of MMP2 SNP bearing BCPAPV600E cells exhibited highly invasive phenotypes characterized by a high rate of wound healing and enhanced cell invasion compared with parental BCPAPV600E cells bearing vector. We also determined that BCPAPV600E cells stably transfected with MMP2 SNPs were highly sensitive to the treatment of BRAF inhibitor, PLX4720. Our study demonstrates that MMP2 SNPs could cooperate with BRAFV600E to promote oncogenicity, migration, and invasiveness of PTC cells. These results suggest that a subset of papillary thyroid cancer with this genetic makeup may benefit from BRAF-mediated therapeutic interventions.