外泌体介导tRNA衍生片段tRF-TAMR促进乳腺癌他莫昔芬耐药及其机制研究

tRFs is a novel class of small non-coding RNAs derived from tRNA cleavage. It exists widely and is closely associated with human cancers. Through analyzing our high-sequencing data we have identified a function-unknown tRF named tRF-TAMR, which is significantly high expressed in Tamoxifen resistance breast cancer tissues. Preliminary experiments and bioinformatics analysis indicated that Tamoxifen-resistant breast cancer cells can induce resistance to Tamoxifen-sensitive cells in breast cancer by secreting exosomes containing tRF-TAMR. ERα and PTEN may be the potential downstream target genes. We therefore hypothesized that tRF-TAMR delivered by exosomes could regulate the expression of ERα and PTEN, which further promote Tamoxifen resistance. The current project aims to use exosomes as clues to assess the relationship between tRF-TAMR and Tamoxifen resistance in vitro and in vivo. Secondly, investigate the molecular mechanism that tRF-TAMR affects Tamoxifen resistance by regulating the expression of target genes such as ERα and PTEN. Finally, evaluate the relationship between Tamoxifen resistance and the expression of tRF-TAMR in breast cancer tissues and serum. This study is expected to provide new potential biomarkers for the prevention and treatment of Tamoxifen-resistant breast cancer.

tRF是一类由转运RNA产生、广泛存在并与肿瘤密切相关的新型调控性非编码RNA。tRF-TAMR是申请人通过高通量测序筛选出的高表达于乳腺癌他莫昔芬（TAM）耐药组织的tRF。前期结果表明：在TAM耐药的乳腺癌细胞中沉默tRF-TAMR可恢复药物敏感性；而TAM耐药的乳腺癌细胞可通过分泌含有tRF-TAMR的外泌体诱导药物敏感细胞发生耐药；机制实验提示ERα和PTEN是tRF-TAMR潜在的下游靶基因。因此我们提出外泌体介导的tRF-TAMR通过在乳腺癌细胞中下调靶基因的表达，促进TAM耐药的科学假说。本项目将以外泌体为线索，在体内外证实tRF-TAMR促进乳腺癌TAM耐药的作用，并探究tRF-TAMR调控ERα和PTEN等靶基因从而促进TAM耐药的分子机制，评价tRF-TAMR在肿瘤组织及血清中的表达与乳腺癌发生TAM耐药的关联，为tRF-TAMR作为乳腺癌TAM耐药的新靶标提供依据。

他莫昔芬耐药是激素受体阳性（HR+）乳腺癌患者临床治疗的一大挑战，近年来研究表明tRF作为一类由转运RNA产生的新型调控性非编码RNA，在多种肿瘤的发生发展中发挥重要作用。tRF-TAMR（tRF-16-K8J7K1B）是申请人通过高通量测序筛选出的高表达于乳腺癌他莫昔芬耐药组织的tRF，tRF-16-K8J7K1B高表达和HR+乳腺癌患者DFS缩短显著相关。过表达tRF-16-K8J7K1B可促进乳腺癌他莫昔芬耐药，此外胞外tRF-16-K8J7K1B可通过外泌体被敏感细胞摄取。机制研究表明，外泌体介导tRF-16-K8J7K1B通过降解受体细胞中的促凋亡蛋白TRAIL，抑制其下游caspase家族成员介导的细胞凋亡过程从而导致他莫昔芬耐药。动物实验的结果表明，抑制tRF-16-K8J7K1B可增加耐药细胞对他莫昔芬的敏感性。以上结果表明外泌体 tRF-16-K8J7K1B 可作为他莫昔芬耐药的新靶标，望为改善乳腺癌患者他莫昔芬耐药的发生提供新的思路。