BRAF Gene And Its Signaling Pathway In The Pathogenesis Of Papillary Thyroid Carcinoma

Aims:To invstigate the association and mechanism between activity of BRAF and RAS-BARF-MAPK signal pathway in papillary thyroid cancer.Methods:73cases of papillary thyroid cancer and16cases of thyroid gland benign with detailed clinical data were collected. Then we detected the expression of RAS, BRAF, MEK and ERK protein in all tumor specimens and thyroid benign tissues using immunohistochemistry and Western blot. The relation between the variation of the protein expression and diseases was established. We explored the effect of RAS-BRAF-MEK-ERK signaling pathway in papillary thyroid cancer.To explore the correlation bewteen BARF mutation and papillary thyroid cancer, BRAF gene mutations in papillary thyroid cancer and were detected by PCR and sequencing technology. At the same time, we selected2targeting sequences and designed2pairs SiRNA interference sequences, then transfected them into SW579cell line with liposome and detected interference effect using RT-PCR and immunofluorescence. The interfered successfully cell line was detected for cell proliferation, cell cycle and the RAS-BRAF-MEK-ERK signaling pathway. Results:The expression of RAS, BRAF, MEK and ERK protein in thyroid cancer tissues is higher than the benign thyroid tissue, p<0.05,. Phosphorylated ERK protein in thyroid cancer presents a significant nuclear distribution compared to benign thyroid tissues p<0.05.We screened42cases BARF V600D mutations in73cases of thyroid cancer. The mutation rate is57.5%. However, no mutation was found in benign thyroid.To investigate effect of BRAF in tumor development, we use2siRNA interference oligonucleotides to transfect into SW579cell line. Suggesting BRAF mRNA level and protein expression are significantly inhibited. Through analyzing the SW579cell line after successfully interfere, the results show that the growth of SW579proliferation is inhibited, cell cycle changes, G1/S phase increase, at the same time, RAS-BRAF-MEK-ERK signaling pathway is inhibited.Conclusions:1. The expression of RAS, BRAF and phosphorylated MEK, in papillary thyroid cancer is higher than benign tissues.2. The expression of phosphorylated ERK in nuclear was increased and the RAS-BRAF-MEK-ERK signaling pathway may be activated in papillary thyroid cancer3. The expression and mutation of BRAF was associated with lymph node metastasis and clinical stage of papillary thyroid cancer.4. Thyroid cancer cell growth and proliferation are inhibited through BRAF interference to inactivated RAS-BRAF-MEK-ERK signal pathway.