BACKGROUND Renal cell carcinoma (RCC) is a highly vascular tumor and patients with low risk metastatic RCC of clear-cell histological sub-type (mccRCC) are treated with tyrosine-kinase inhibitors (TKIs), sunitinib, as the first-line of treatment. Unfortunately, TKI resistance eventually develops, and the underlying molecular mechanism is not well understood. METHODS RCC cell-line with metastatic clear-cell histology (Caki-1), and patient samples were analysed to identify the role of Y-box binding protein 1 (YB-1) and ATP-binding cassette sub-family B member 1 (ABCB-1) in acquired sunitinib-resistance development. Caki-1 was conditioned with increasing sunitinib doses to recapitulate acquired resistance development in clinics. Sunitinib-conditioned and wild-type Caki-1 were subjected to cell viability assay, scratch assay, chicken embryo chorioallantoic membrane engraftment and proteomics analysis. Classical biochemical assays like flow cytometry, immunofluorescent staining, immunohistochemical staining, optical coherence tomography imaging, Western Blot and RT-PCR assays were applied to determine the possible mechanism of sunitinib-resistance development and the effect of drug treatments. Publicly available data was also used to determine the role of YB-1 upregulation in ccRCC and the patients' overall survival. RESULTS We demonstrate that YB-1 and ABCB-1 are upregulated in sunitinib-resistant in vitro, ex vivo, in vivo and patient samples compared to the sensitive samples. This provides evidence to a mechanism of acquired sunitinib-resistance development in mccRCC. Furthermore, our results establish that inhibiting ABCB-1 with elacridar, in addition to sunitinib, has a positive impact on reverting sunitinib-resistance development in in vitro, ex vivo and in vivo models. CONCLUSION This work proposes a targeted therapy (elacridar and sunitinib) to re-sensitize sunitinib-resistant mccRCC and, possibly, slow disease progression.

中文翻译：

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Y-box结合蛋白1在转移性透明细胞肾细胞癌的获得性耐药发展中至关重要。

背景技术肾细胞癌（RCC）是一种高度血管性肿瘤，将酪氨酸激酶抑制剂（TKIs）舒尼替尼作为治疗的一线药物，对具有透明细胞组织学亚型（mccRCC）的低风险转移性RCC的患者进行治疗。不幸的是，TKI耐药性最终得以发展，其潜在的分子机制还没有被很好地理解。方法对具有转移性透明细胞组织学的RCC细胞系（Caki-1）和患者样品进行分析，以鉴定Y盒结合蛋白1（YB-1）和ATP结合盒B亚家族B成员1（ ABCB-1）在获得性舒尼替尼耐药性研究中。用增加的舒尼替尼剂量调节Caki-1，以概括临床中获得性耐药性的发展。将以舒尼替尼为条件的野生型Caki-1进行细胞生存力测定，刮擦测定，鸡胚绒膜尿囊膜的植入和蛋白质组学分析。应用流式细胞术，免疫荧光染色，免疫组织化学染色，光学相干断层扫描成像，Western Blot和RT-PCR等经典生化分析来确定舒尼替尼耐药性发展的可能机制和药物治疗的效果。公开可用的数据还用于确定YB-1上调在ccRCC中的作用和患者的整体生存率。结果我们证明，与敏感样品相比，在耐舒尼替尼的体外，离体，体内和患者样品中，YB-1和ABCB-1上调。这为mccRCC中获得性舒尼替尼耐药性发展的机制提供了证据。此外，我们的结果表明，用elacridar抑制ABCB-1，除舒尼替尼外，在体外，离体和体内模型中对舒尼替尼耐药性的恢复都有积极作用。结论这项工作提出了一种靶向治疗药物（艾来达和舒尼替尼），以使耐舒尼替尼的mccRCC重新敏感，并可能减慢疾病的进程。