内吞和自噬相关miRNA在乳腺癌细胞膜DR4/5分布及抗癌药物TRAIL耐受中的作用研究

TRAIL therapy has obtained intense interest and attention as one of the most promising agents for breast cancer therapy, as it selectively induces apoptosis of tumor cells and has low toxicity to most normal cells. Nonetheless, TRAIL resistance which is caused by deficient expression of DR4 and DR5 on cell surface has an adverse effect on its clinical application. Decreased expression of DR4/5 on cell surface, which is caused by endocytosis and autophagy, is an important factor for TRAIL resistance of breast cancer cells. However, the molecular mechanism has yet to be characterized. To date, many researches have demonstrated that miRNAs not only are involved in regulation of endocytosis and autophagy pathways, but also modulated sensitive/resistant phenotypes of breast cancer cells to TRAIL at the same time. However, the role of miRNAs, which regulate endocytosis and autophagy, in TRAIL resistance of breast cancer cells remains to be elucidated. In this study, based on the miRNA microarray data of TRAIL resistant/sensitive breast cancer cells, potential miRNAs and their target genes, we aim to screen the specific miRNAs that modulate endocytosis and autophagy, and analyze their impact on cell surface expression of DR4/5 and their relevance to the TRAIL resistance. Ultimately, the novel molecular mechanism of "miRNA-endocytosis/autophagy-cell surface expression of DR4/5-TRAIL resistance" will be uncovered in breast cancer cells and be validated in clinical breast cancer specimens. This study will provide a novel target for therapy of TRAIL resistance in breast cancer cell caused by deficiency of DR4/5 on the cell surface due to endocytosis and autophagy, expand the range of application of TRAIL in clinical therapy and improve the therapeutic efficacy of TRAIL in breast cancer.

肿瘤坏死因子相关的细胞凋亡诱导配体(TRAIL)是一种极具应用前景的乳腺癌治疗新药。然而细胞膜表面DR4/5缺失导致的TRAIL耐药性会影响其临床应用。研究表明内吞和自噬引起的细胞膜表面DR4/5缺失是导致乳腺癌细胞对TRAIL耐受的重要因素。miRNA在肿瘤细胞内吞和自噬过程中及乳腺癌细胞对TRAIL耐受中发挥重要的调节作用，但内吞和自噬相关的miRNA在乳腺癌细胞TRAIL耐受中的作用尚不明确。本课题拟基于TRAIL相关的乳腺癌细胞miRNA芯片数据、相关候选miRNA及其靶基因筛选出内吞和自噬相关的miRNA，验证其与膜表面DR4/5分布及TRAIL耐受的相关性，进而揭示“miRNA调控内吞和自噬影响乳腺癌细胞膜表面DR4/5分布”在乳腺癌细胞TRAIL耐受中的作用新机制，并在临床样本中验证。本课题旨在为治疗TRAIL耐受乳腺癌提供新方法，扩大TRAIL的适用范围，增强其疗效。

乳腺癌已成为全球女性最常见的恶性肿瘤。肿瘤坏死因子相关的凋亡诱导配体(TRAIL)通过细胞表面死亡受体4和5(DR4/5)选择性诱导癌细胞凋亡。在多种癌症中，miRNAs可以调节细胞对TRAIL敏感或者耐药表型，但是其在耐药乳腺癌中的作用尚不清楚。通过低剂量TRAIL反复处理，建立耐受TRAIL的MDA-MB-231细胞系，进一步研究与TRAIL耐药相关的miRNAs (包括miR-130a、miR-181a和miR-221)。与亲代细胞相比，耐受TRAIL的MDA-MB-231细胞中miR-221过表达，细胞表面DR4/5下调。自噬抑制剂3-MA预处理后，MDA-MB-231/TR对TRAIL的敏感性增加，对TRAIL耐受性部分减弱。当在MDA-MB-231/TR中沉默miR-221时，细胞表面DR5轻度上调，特别是对TRAIL的耐药性部分逆转。我们的研究结果表明，miR-221可能通过调节内吞作用，下调细胞表面DR5的含量来调节乳腺癌细胞对TRAIL耐药。

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