Combined BRAFV600E- and SRC-inhibition induces apoptosis, evokes an immune response and reduces tumor growth in an immunocompetent orthotopic mouse model of anaplastic thyroid cancer

Abstract

Anaplastic (ATC) and refractory papillary thyroid cancer (PTC) lack effective treatments. Inhibition of either oncogenic BRAF or SRC has marked anti-tumor effects in mouse models of thyroid cancer, however, neither drug induces notable apoptosis. Here we report that the SRC-inhibitor dasatinib further sensitizes BRAFV600E-positive thyroid cancer cells to the BRAFV600E-inhibitor PLX4720. Combined treatment with PLX4720 and dasatinib synergistically inhibited proliferation and reduced migration in PTC and ATC cells. Whereas PLX4720 did not induce robust apoptosis in thyroid cancer cells, combined treatment with dasatinib induced apoptosis in 4 of 6 lines. In an immunocompetent orthotopic mouse model of ATC, combined PLX4720 and dasatinib treatment significantly reduced tumor volume relative to PLX4720 treatment alone. Immune cell infiltration was increased by PLX4720 treatment and this effect was maintained in mice treated with both PLX4720 and dasatinib. Further, combined treatment significantly increased caspase 3 cleavage in vivo relative to control or either treatment alone. In conclusion, combined PLX4720 and dasatinib treatment induces apoptosis, increases immune cell infiltration and reduces tumor volume in a preclinical model of ATC, suggesting that the combination of these FDA-approved drugs may have potential for the treatment of patients with ATC or refractory PTC.

The Mitogen-Activated Protein Kinase Pathway Facilitates Resistance to the Src Inhibitor Dasatinib in Thyroid Cancer

“…Furthermore, we show for the first time that combined Src inhibition with dasatinib and MEK1/2 inhibition with trametinib results in enhanced anti-tumor responses and increased survival (Fig. 6), similar to a previous study that evaluated BRAF inhibition with vemurafenib in combination with dasatinib (13). In support of this, recent data with a dual dimerization-breaking RAF inhibitor that also targets Src appears promising, and may be an effective new strategy to prevent or delay resistance to single agent therapy (48).…”

“…4 and 5). Additionally, we and others have shown enhanced anti-growth and pro-apoptotic responses over single agent therapy when Src and MAP Kinase pathway inhibitors are used in combination in vitro (13,47) (Fig. 6).…”

“…We and others have previously demonstrated that inhibition of the Src signaling pathway with the Src inhibitors, dasatinib (BMS-354825) or saracatinib (AZD0530) effectively inhibits thyroid cancer growth and metastasis, both in vitro and in vivo (10–13). Despite dasatinib being a multi-kinase inhibitor, we have further shown that c-Src is a key mediator of these responses (10).…”

Expression of angiogenic switch, cachexia and inflammation factors at the crossroad in undifferentiated thyroid carcinoma with BRAF

“…Diverse pathways are altered in ATC, including at least the RAS/RAF/MAPK and PI3K/AKT signaling cascades [8] [9] [7] [35] [36] [14] [37] [38; 39; 40]. We previously found that BRAF V600E regulates protein expression of extracellular matrix (ECM) molecules in human ATC cells which are required for tumor invasion and metastasis [12; 41; 42].…”

Combinatorial Therapies in Thyroid Cancer: An Overview of Preclinical and Clinical Progresses

“…As for the previous study described above, reduced tumor volume and increased immune cell infiltration, including cytotoxic T cells, B cells, and macrophages, were observed with the combination. These last results seem primordial in challenging the treatment of ATC and should deserve further investigations [61]. The antitumoral potential of the SRC inhibitor dasatinib has been also studied in the context of a combination with a MAPK inhibitor, trametinib.…”