Dataset Information

Co-inhibition of SMAD and MAPK signaling enhances 124I uptake in BRAF-mutant thyroid cancers.

ABSTRACT: Constitutive MAPK activation silences genes required for iodide uptake and thyroid hormone biosynthesis in thyroid follicular cells. Accordingly, most BRAFV600E papillary thyroid cancers (PTC) are refractory to radioiodide (RAI) therapy. MAPK pathway inhibitors rescue thyroid-differentiated properties and RAI responsiveness in mice and patient subsets with BRAFV600E-mutant PTC. TGFB1 also impairs thyroid differentiation and has been proposed to mediate the effects of mutant BRAF. We generated a mouse model of BRAFV600E-PTC with thyroid-specific knockout of the Tgfbr1 gene to investigate the role of TGFB1 on thyroid-differentiated gene expression and RAI uptake in vivo. Despite appropriate loss of Tgfbr1, pSMAD levels remained high, indicating that ligands other than TGFB1 were engaging in this pathway. The activin ligand subunits Inhba and Inhbb were found to be overexpressed in BRAFV600E-mutant thyroid cancers. Treatment with follistatin, a potent inhibitor of activin, or vactosertib, which inhibits both TGFBR1 and the activin type I receptor ALK4, induced a profound inhibition of pSMAD in BRAFV600E-PTCs. Blocking SMAD signaling alone was insufficient to enhance iodide uptake in the setting of constitutive MAPK activation. However, combination treatment with either follistatin or vactosertib and the MEK inhibitor CKI increased 124I uptake compared to CKI alone. In summary, activin family ligands converge to induce pSMAD in Braf-mutant PTCs. Dedifferentiation of BRAFV600E-PTCs cannot be ascribed primarily to activation of SMAD. However, targeting TGFβ/activin-induced pSMAD augmented MAPK inhibitor effects on iodine incorporation into BRAF tumor cells, indicating that these two pathways exert interdependent effects on the differentiation state of thyroid cancer cells.

SUBMITTER: Luckett KA

PROVIDER: S-EPMC8183640 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description:The aggressive clinical behavior of poorly differentiated and anaplastic thyroid cancers (PDTC and ATC) has proven challenging to treat, and survival beyond a few months from diagnosis is rare. Although 30%-60% of these tumors contain mutations in the BRAF gene, inhibitors designed specifically to target oncogenic BRAF have shown limited and only short-lasting therapeutic benefits as single agents, thus highlighting the need for improved treatment strategies, including novel combinations. Using a BRAFV600E-driven mouse model of ATC, we investigated the therapeutic efficacy of the combination of BRAF inhibition and oncolytic herpes simplex virus (oHSV). Analyses of samples from tumor-bearing mice were performed to immunologically characterize the effects of different treatments. These immune data were used to inform the incorporation of immune checkpoint inhibitors into triple combination therapies. We characterized the immune landscape in vivo following BRAF inhibitor treatment and detected only modest immune changes. We, therefore, hypothesized that the addition of oncolytic virotherapy to BRAF inhibition in thyroid cancer would create a more favorable tumor immune microenvironment, boost the inflammatory status of tumors and improve BRAF inhibitor therapy. First, we showed that thyroid cancer cells were susceptible to infection with oHSV and that this process was associated with activation of the immune tumor microenvironment in vivo. Next, we showed improved therapeutic responses when combining oHSV and BRAF inhibition in vivo, although no synergistic effects were seen in vitro, further confirming that the dominant effect of oHSV in this context was likely immune-mediated. Importantly, both gene and protein expression data revealed an increase in activation of T cells and natural killer (NK) cells in the tumor in combination-treated samples. The benefit of combination oHSV and BRAF inhibitor therapy was abrogated when T cells or NK cells were depleted in vivo. In addition, we showed upregulation of PD-L1 and CTLA-4 following combined treatment and demonstrated that blockade of the PD-1/PD-L1 axis or CTLA-4 further improved combination therapy. The combination of oHSV and BRAF inhibition significantly improved survival in a mouse model of ATC by enhancing immune-mediated antitumor effects, and triple combination therapies, including either PD-1 or CTLA-4 blockade, further improved therapy.

Dataset Information

Co-inhibition of SMAD and MAPK signaling enhances 124I uptake in BRAF-mutant thyroid cancers.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets