. Dual BRAF and PKCα inhibition diminishes cell viability in thyroid cancer cells.

CAMPOS HAEDO MN; DIAZ FLAQUÉ MC; DÍAZ ALBUJA JA; PERONA M; CAYROL MF; DEBERNARDI MM; STERLE HA; JUVENAL GJ; CREMASCHI GA; ROSEMBLIT C

Congreso; XIX Congreso Internacional de Endocrinología (ICE 2021); 2021

FASEN

Introduction: Thyroid carcinoma (TC) is the most common endocrine neoplasia. Its incidence has increased in the last 40 years worldwide. About half of TC are driven by an acquired activating mutation in the BRAF oncogene. While targeted therapies have improved outcomes in melanoma patients, most TC patients become resistant or recur suggesting that new or additive non-cross-reactive therapies are needed. We have previously shown that PKCα mediates TSH and thyroid hormones proliferative effects in TC. Recent evidence indicates that PKCα overexpression and BRAF mutation should contribute together to tumorigenesis and resistance to anticancer therapies.Objectives: To analyze whether PKCα expression together with the presence of BRAFV600E confer an advantage over tumor growth.Methods: 8505C anaplastic and WRO follicular TC cell viability was evaluated by Cell Titter Blue (CTB) assay. Protein modulation was measured by Western blot. RNAi transfection was used to knock down PKCα and BRAF expression. Vemurafenib (PLX) and GF109203X (GF) were used to inhibit BRAFV600E and PKCα, respectively. In silico analysis on Papillary Thyroid Carcinoma (TCGA, Cell 2014) was performed using CBioPortal.Results: We found that by inhibiting BRAF expression in TC cells with BRAF mutation, PKCα expression also decreases, suggesting that the latter is downstream of BRAF. Furthermore, a decrease in the expression of the proliferation marker PCNA was observed in BRAF-depleted cells. To begin to study the combined inhibition of PKC and BRAF, CTB assays were performed with increasing doses of PLX in presence or absence of the PKC inhibitor GF at a selective concentration in TC cells carrying BRAF mutation. We found a decrease in cell viability in a dose-dependent manner with PLX (p