乳腺癌是女性最常见的癌症。人表皮生长因子受体2（HER2）过表达亚型与侵袭性表型伴有不良预后相关，并且被报道为最常见的亚型之一。曲妥珠单抗是治疗HER2阳性乳腺癌的流行方法，然而，治疗后通常会发生对该药物的耐药性。微小RNA（miRNAs）是19-23核苷酸长的小RNA，能在转录后水平调节基因表达，研究显示在药物敏感和耐药组之间存在差异表达的miRNAs，表明它们可能在药物效果中起到重要作用。本研究的目标是了解miR-216b-5p在曲妥珠单抗耐药性中的作用。SK-BR-3细胞在连续6个月以递增浓度的药物处理后对曲妥珠单抗产生了耐药性。为了研究miR-216b-5p对耐药状态下癌细胞行为的影响，使用xCELLigence实时细胞分析仪分析了这些耐药细胞的增殖、运动和侵袭力。为了进一步理解miR-216b-5p调节耐药性SK-BR-3细胞的分子机制，进行了微阵列分析。由于路径富集分析指出细胞死亡相关途径，因此还进行了凋亡分析。miR-216b-5p转染的耐药细胞相比敏感细胞的增殖、运动和侵袭能力减弱。我们通过微阵列和路径富集分析识别了坏死调节信号通路作为结果。STAT1、IRF9和PKR被验证为该通路的重要元素，同时也是miR-216b-5p的潜在靶点。我们的凋亡分析显示，miR-216b-5p过表达后，大量曲妥珠单抗耐药性SK-BR-3细胞进入晚期凋亡/坏死阶段，因此可以得出结论，miR-216b-5p的再表达通过坏死调节作用在乳腺癌中增强曲妥珠单抗的敏感性。©TÜBİTAK。

Breast cancer is the most common cancer in women. The human epidermal growth factor receptor 2 (HER2) overexpressing subtype is related to poor prognosis with an aggressive phenotype and is reported as one of the most commonly seen subtypes. Trastuzumab is prevalently used as a treatment method for HER2+ breast cancer however, resistance to the drug frequently occurs following the treatment. MicroRNAs (miRNAs) are 19-23 nucleotide long small RNAs, which regulate gene expression at post-transcriptional level and studies show that there are differentially expressed miRNAs between drug sensitive and resistant groups, indicating that they might have some key roles in drug effectiveness. In this study, the aim is to find out the role of miR-216b-5p in trastuzumab resistance. SK-BR-3 cells developed resistance to trastuzumab after continuous treatment with increasing concentrations of the drug for 6 months. To investigate the effect of miR-216b-5p on cancer cell behavior in resistance state, proliferation, motility, and invasion capacities of these resistant cells were analyzed by xCELLigence real-time cell analyzer. To further understand the molecular mechanisms underlying the regulation of resistant SK-BR-3 cells by miR-216b-5p, microarray analysis was performed. Apoptosis analysis was also performed since the pathway enrichment analysis pointed out cell death related pathways. The proliferation, motility, and invasion capacities of the miR-216b-5p transfected resistant cells were diminished compared to sensitive cells. We identified the necroptosis signaling pathway as the result of microarray and pathway enrichment analyses. STAT1, IRF9, and PKR were validated as the significant elements of the pathway, which are also the putative targets of miR-216b-5p. Our apoptosis analysis showed that a significant amount of trastuzumab resistant SK-BR-3 cells entered to late apoptosis/necrosis stage upon miR-216b-5p overexpression, it could be concluded that reexpression of miR-216b-5p sensitizes trastuzumab resistance through necroptosis in breast cancer.© TÜBİTAK.