Laboratory of Human Thyroid Cancers Preclinical and Translational Research, Division of Experimental Pathology, Cancer Research Institute (CRI), Cancer Center, Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
Department of Pathology, Center for Vascular Biology Research (CVBR), Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
Clin Cancer Res. 2018 Dec 1;24(23):6078-6097. doi: 10.1158/1078-0432.CCR-18-0693. Epub 2018 Aug 3.
The BRAF oncogene modulates the papillary thyroid carcinoma (PTC) microenvironment, in which pericytes are critical regulators of tyrosine-kinase (TK)-dependent signaling pathways. Although BRAF and TK inhibitors are available, their efficacy as bimodal therapeutic agents in BRAF-PTC is still unknown.
We assessed the effects of vemurafenib (BRAF inhibitor) and sorafenib (TKI) as single agents or in combination in BRAF-PTC and BRAF cells using cell-autonomous, pericyte coculture, and an orthotopic mouse model. We also used BRAF-PTC and BRAF-PTC clinical samples to identify differentially expressed genes fundamental to tumor microenvironment.
Combined therapy blocks tumor cell proliferation, increases cell death, and decreases motility via BRAF inhibition in thyroid tumor cells . Vemurafenib produces cytostatic effects in orthotopic tumors, whereas combined therapy (likely reflecting sorafenib activity) generates biological fluctuations with tumor inhibition alternating with tumor growth. We demonstrate that pericytes secrete TSP-1 and TGFβ1, and induce the rebound of pERK1/2, pAKT and pSMAD3 levels to overcome the inhibitory effects of the targeted therapy in PTC cells. This leads to increased BRAF-PTC cell survival and cell death refractoriness. We find that BRAF-PTC clinical samples are enriched in pericytes, and TSP1 and TGFβ1 expression evoke gene-regulatory networks and pathways (TGFβ signaling, metastasis, tumor growth, tumor microenvironment/ECM remodeling functions, inflammation, VEGF ligand-VEGF receptor interactions, immune modulation, etc.) in the microenvironment essential for BRAF-PTC cell survival. Critically, antagonism of the TSP-1/TGFβ1 axis reduces tumor cell growth and overcomes drug resistance.
Pericytes shield BRAF-PTC cells from targeted therapy via TSP-1 and TGFβ1, suggesting this axis as a new therapeutic target for overcoming resistance to BRAF and TK inhibitors.
BRAF 癌基因调节甲状腺乳头状癌（PTC）微环境，其中周细胞是酪氨酸激酶（TK）依赖性信号通路的关键调节因子。虽然 BRAF 和 TK 抑制剂已经上市，但它们作为 BRAF-PTC 的双模态治疗药物的疗效尚不清楚。
我们使用自主细胞、周细胞共培养和原位小鼠模型评估了 vemurafenib（BRAF 抑制剂）和 sorafenib（TKI）作为单一药物或联合治疗 BRAF-PTC 和 BRAF 细胞的效果。我们还使用 BRAF-PTC 和 BRAF-PTC 临床样本来鉴定对肿瘤微环境至关重要的差异表达基因。
联合治疗通过 BRAF 抑制阻断甲状腺肿瘤细胞的增殖，增加细胞死亡，并降低迁移率。vemurafenib 在原位肿瘤中产生细胞停滞作用，而联合治疗（可能反映 sorafenib 的活性）产生生物波动，肿瘤抑制与肿瘤生长交替。我们证明周细胞分泌 TSP-1 和 TGFβ1，并诱导 pERK1/2、pAKT 和 pSMAD3 水平的反弹，以克服靶向治疗对 PTC 细胞的抑制作用。这导致 BRAF-PTC 细胞的存活和细胞死亡抵抗增加。我们发现 BRAF-PTC 临床样本富含周细胞，TSP1 和 TGFβ1 的表达在微环境中引发基因调控网络和途径（TGFβ 信号转导、转移、肿瘤生长、肿瘤微环境/ECM 重塑功能、炎症、VEGF 配体-VEGF 受体相互作用、免疫调节等），这些途径对于 BRAF-PTC 细胞的存活至关重要。重要的是，TSP-1/TGFβ1 轴的拮抗作用可减少肿瘤细胞的生长并克服耐药性。
周细胞通过 TSP-1 和 TGFβ1 保护 BRAF-PTC 细胞免受靶向治疗，表明该轴作为克服 BRAF 和 TK 抑制剂耐药性的新治疗靶点。
