Dual BRAF and PKC&; inhibition diminishes cell viability in thyroid cancer cells.

CAMPOS HAEDO, M.N.; DÍAZ FLAQUÉ, M.C.; DÍAZ ALBUJA, J.A.; PERONA, M; CAYROL, F.; DEBERNARDI, M; STERLE, H.A.; JUVENAL, G; CREMASCHI, G.A.; ROSEMBLIT, CINTHIA

Congreso; ICE 2021 Virtual:19th International Congress of Endocrinology, 4th Latin American Congress of Endocrinology and 13th Congress of the Argentine Federation of Endocrinology Societies.; 2021

Introduction: Thyroid carcinoma (TC) is the most common endocrine neoplasia. Its incidence has increased in the last 40years worldwide. About half of TC are driven by an acquired activating mutation in the BRAF oncogene. While targetedtherapies have improved outcomes in melanoma patients, most TC patients become resistant or recur suggesting thatnew or additive non-cross-reactive therapies are needed. We have previously shown that PKCα mediates TSH andthyroid hormones proliferative effects in TC. Recent evidence indicates that PKCα overexpression and BRAF mutationshould contribute together to tumorigenesis and resistance to anticancer therapies. Objectives: To analyze whether PKCα expression together with the presence of BRAFV600E confer an advantage overtumor growth.Methods: 8505C anaplastic and WRO follicular TC cell viability was evaluated by Cell Titter Blue (CTB) assay. Proteinmodulation 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 onPapillary 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 markerPCNA was observed in BRAF-depleted cells. To begin to study the combined inhibition of PKC and BRAF, CTB assayswere performed with increasing doses of PLX in presence or absence of the PKC inhibitor GF at a selectiveconcentration in TC cells carrying BRAF mutation. We found a decrease in cell viability in a dose-dependent manner withPLX (p