Inhibiting BRAF Oncogene-Mediated Radioresistance Effectively Radiosensitizes BRAF(V600E)-Mutant Thyroid Cancer Cells by Constraining DNA Double-Strand Break Repair.

Activating BRAF mutations, most commonly BRAFV600E, are a major oncogenic driver of many cancers. We explored whether BRAFV600E promotes radiation resistance and whether selectively targeting BRAFV600E with a BRAF inhibitor (vemurafenib, BRAFi) sensitizes BRAFV600E thyroid cancer cells to radiotherapy. Immunoblotting, neutral comet, immunocytochemistry, functional reporter, and clonogenic assays were used to analyze the outcome and molecular characteristics following radiotherapy with or without BRAFV600E or vemurafenib in thyroid cancer cells. BRAFV600E thyroid cancer cell lines were associated with resistance to ionizing radiation (IR), and expression of BRAFV600E into wild-type BRAF thyroid cancer cells led to IR resistance. BRAFi inhibited ERK signaling in BRAFV600E mutants, but not BRAF wild-type thyroid cancer cell lines. BRAFi selectively radiosensitized and delayed resolution of IR-induced γH2AX nuclear foci in BRAFV600E cells. Moreover, BRAFi impaired global DNA repair and altered the resolution of 53BP1 and RAD51 nuclear foci in BRAFV600E cells following IR. BRAFV600E mutants displayed enhanced nonhomologous end-joining (NHEJ) repair activity, which was abolished by BRAFi. Intriguingly, BRAFV600E mutation led to upregulation of XLF, a component of NHEJ, which was prevented by BRAFi. Importantly, BRAFi in combination with radiotherapy resulted in marked and sustained tumor regression of BRAFV600E thyroid tumor xenografts. BRAFV600E mutation promotes NHEJ activity leading to radioresistance and BRAFi selectively radiosensitizes BRAFV600E thyroid cancer cells through inhibiting NHEJ. Our findings suggest that combining BRAFi and radiation may improve the therapeutic outcome of patients with BRAFV600E-mutant thyroid cancer.

Robb R ，Yang L ，Shen C ，Wolfe AR ，Webb A ，Zhang X ，Vedaie M ，Saji M ，Jhiang S ，Ringel MD ，Williams TM ... -  《-》

Combination Treatment with the BRAF(V600E) Inhibitor Vemurafenib and the BH3 Mimetic Navitoclax for BRAF-Mutant Thyroid Carcinoma.

Jeong JH ，Oh JM ，Jeong SY ，Lee SW ，Lee J ，Ahn BC ... -  《-》

Fine-Tuning Lipid Metabolism by Targeting Mitochondria-Associated Acetyl-CoA-Carboxylase 2 in BRAF(V600E) Papillary Thyroid Carcinoma.

Valvo V ，Iesato A ，Kavanagh TR ，Priolo C ，Zsengeller Z ，Pontecorvi A ，Stillman IE ，Burke SD ，Liu X ，Nucera C ... -  《-》

Vemurafenib Drives Epithelial-to-Mesenchymal Transition Gene Expression in BRAF Inhibitor‒Resistant BRAF(V600E)/NRAS(Q61K) Melanoma Enhancing Tumor Growth and Metastasis in a Bioluminescent Murine Model.

BRAF inhibitor (BRAFi) resistance compromises long-term survivorship of patients with malignant melanoma, and mutant NRAS is a major mediator of BRAFi resistance. In this study, employing phenotypic and transcriptomic analysis of isogenic melanoma cells that differ only by NRAS mutational status (BRAFi-sensitive A375-BRAFV600E/NRASQ61 vs. BRAFi-resistant A375-BRAFV600E/NRASQ61K), we show that BRAFi (vemurafenib) treatment selectively targets BRAFV600E/NRASQ61K cells upregulating epithelial-to-mesenchymal transition (EMT) gene expression, paradoxically promoting invasiveness and metastasis in vitro and in vivo. First, NanoString nCounter transcriptomic analysis identified the upregulation of specific gene expression networks (EMT and EMT to metastasis) as a function of NRASQ61K status. Strikingly, BRAFi treatment further exacerbated the upregulation of genes promoting EMT in BRAFV600E/NRASQ61K cells (with opposing downregulation of EMT-driver genes in the BRAFV600E/NRASQ61 genotype) as detected by EMT-focused RT2 Profiler qPCR array analysis. In BRAFV600E/NRASQ61K cells, BRAFi treatment enhanced proliferation and invasiveness, together with activation of phosphorylated protein kinase B (Ser473), with opposing phenotypic effects observable in BRAFV600E/NRASQ61 cells displaying downregulation of phosphorylated protein kinase B and phosphorylated extracellular signal-regulated kinase 1/2. In a SCID mouse bioluminescent melanoma metastasis model, BRAFi treatment enhanced lung tumor burden imposed by BRAFV600E/NRASQ61K cells while blocking BRAFV600E/NRASQ61 metastasis. These preclinical data document the BRAFi-driven enhancement of tumorigenesis and metastasis in BRAFi-resistant human BRAFV600E/NRASQ61K melanoma, a finding with potential clinical implications for patients with NRAS-driven BRAFi-resistant tumors receiving BRAFi treatment.

Jandova J ，Wondrak GT 《-》

Upregulation of TRIB2 by Wnt/β-catenin activation in BRAF(V600E) papillary thyroid carcinoma cells confers resistance to BRAF inhibitor vemurafenib.

Wang N ，Wen J ，Ren W ，Wu Y ，Deng C ... -  《-》