A strong evidence suggests the role of BRAFV600E mutation in determining the aggressiveness of thyroid cancer. To detect how the association of BRAF mutation could influence the aggressiveness of particular subtypes of thyroid tumors, we analysed a possible correlation between BRAFV600E and metalloproteinase (MMPs) activity, as its enhanced production could be an important determinant of tumor invasion. For this purpose, we investigated the activity and the expression of different MMPs in anaplastic thyroid cell lines, such as FRO, ARO and KAT-18, by means of zymography and real time-polymerase chain reaction (RT-PCR). FRO and ARO cell lines are homozygote and heterozygote respectively for BRAFV600E, while KAT-18 cells are negative for BRAF mutation.
Analysis of the enzymatic activity in the different cell supernatants showed that the activity of MMP-2 and MMP-9 was absent in ARO cell line and low in FRO cell lines. In KAT-18 we have found a higher MMP-2 activity, instead MMP-9 resulted absent.
Real-time PCR revealed that MMP3 and MMP-2 were higher in KAT-18 than FRO, while it was absent in ARO cells. The MMP-9 was absent in ARO and KAT-18 and low expressed in FRO. In summary, BRAFWT/MUT ARO cell line was negative for all MMPs, while BRAFMUT/MUT FRO was faintly positive. BRAFWT/WT KAT-18 cell line was strongly positive for MMP2 and MMP3 and negative for MMP9.
Our results show that no complete association between BRAFV600E and MMPs activity seems to exist. Our findings could be explained by the fact that not all the MMPs genes have an AP-1 site in promoter region regulated by BRAF-dependent ERK pathway. Several other transcription factors, such as ETS, NF-kB, and STAT, may modulate differently the expression of each MMP gene. In conclusion, BRAF could be involved in tumor progression through other mechanisms independently from MMPs pathway.
03 - 07 May 2008
European Society of Endocrinology