Lymphatic metastasis is the leading cause responsible for recurrence and progression in papillary thyroid cancer (PTC), where dysregulation of long non-coding RNAs (lncRNAs) has been extensively demonstrated to be implicated. However, the specific lymphatic node metastatsis-related lncRNAs remain not identified in PTC yet. Lymphatic node metastatsis-related lncRNA, MFSD4A-AS1, was explored in the PTC dataset from The Cancer Genome Atlas and our clinical samples. The roles of MFSD4A-AS1 in lymphatic metastasis were investigated in vitro and in vivo. Bioinformatic analysis, luciferase assay and RNA immunoprecipitation assay were performed to identify the potential targets and the underlying pathway of MFSD4A-AS1 in lymphatic metastasis of PTC. MFSD4A-AS1 was specifically upregulated in PTC tissues with lymphatic metastasis. Upregulating MFSD4A-AS1 promoted mesh formation and migration of human umbilical vein endothelial cells and invasion and migration of PTC cells. Importantly and consistently, MFSD4A-AS1 promoted lymphatic metastasis of PTC cells in vivo by inducing the lymphangiogenic formation and enhancing the invasive capability of PTC cells. Mechanistic dissection further revealed that MFSD4A-AS1 functioned as competing endogenous RNA to sequester miR-30c-2-3p, miR-145-3p and miR-139-5p to disrupt the miRNA-mediated inhibition of vascular endothelial growth factors A and C, and further activated transforming growth factor (TGF)-β signaling by sponging miR-30c-2-3p that targeted TGFBR2 and USP15, both of which synergistically promoted lymphangiogenesis and lymphatic metastasis of PTC. Our results unravel novel dual mechanisms by which MFSD4A-AS1 promotes lymphatic metastasis of PTC, which will facilitate the development of anti-lymphatic metastatic therapeutic strategy in PTC.

淋巴转移是导致甲状腺乳头状癌 (PTC) 复发和进展的主要原因，其中长链非编码 RNA (lncRNA) 的失调已被广泛证明与此有关。然而，PTC 中与淋巴结转移相关的特定 lncRNA 尚未确定。淋巴结转移相关的 lncRNA，MFSD4A-AS1，在癌症基因组图谱的 PTC 数据集中和我们的临床样本中进行了探索。体外和体内研究了MFSD4A-AS1在淋巴转移中的作用。通过生物信息学分析、荧光素酶测定和RNA免疫沉淀测定来确定MFSD4A-AS1在PTC淋巴转移中的潜在靶点和潜在通路。MFSD4A-AS1 在有淋巴转移的 PTC 组织中特异性上调。上调MFSD4A-AS1促进人脐静脉内皮细胞的网状形成和迁移以及PTC细胞的侵袭和迁移。重要且一致的是，MFSD4A-AS1通过诱导淋巴管生成并增强PTC细胞的侵袭能力，促进PTC细胞体内淋巴转移。机制解剖进一步揭示，MFSD4A-AS1 作为竞争性内源性 RNA 来隔离 miR-30c-2-3p、miR-145-3p 和 miR-139-5p，从而破坏 miRNA 介导的血管内皮生长因子 A 和 C 抑制，并通过海绵靶向TGFBR2和USP15的miR-30c-2-3p进一步激活转化生长因子（TGF）-β信号，两者协同促进PTC的淋巴管生成和淋巴转移。我们的研究结果揭示了MFSD4A-AS1促进PTC淋巴转移的新双重机制，这将有助于PTC抗淋巴转移治疗策略的发展。