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Abstract：
Background: Breast cancer is the second most common cause of cancer-related mortality globally. Apolipoprotein L3 (APOL3), a member of the apolipoprotein family, has been implicated in the pathogenesis of cardiovascular diseases. Nevertheless, the functions and underlying mechanisms of APOL3 in breast cancer have yet to be elucidated. Methods: The patient data were sourced from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) database. Quantitative real-time PCR (qRT-PCR), western blotting, and immunohistochemistry (IHC) assays were used to assess expression of APOL3. Cell proliferation rates were determined by Cell Counting Kit-8 (CCK-8) and colony formation assays. Flow cytometry was used to examine cell cycle distribution. Western blotting was conducted to investigate the expression of cell cycle related proteins. A xenograft model was used to evaluate the effect of APOL3 in vivo. APOL3-binding proteins were identified through mass spectrometry, co-immunoprecipitation (CO-IP) assay and immunofluorescence assay. Results: APOL3 expression was significantly downregulated in breast cancer, and its low expression was correlated with poor prognostic outcomes. Overexpression of APOL3 suppressed breast cancer cell proliferation, induced cell cycle disruption. Conversely, knockdown of APOL3 promoted cell proliferation. In vivo animal experiments demonstrated that APOL3 overexpression can inhibit tumor proliferation. Mass spectrometry, CO-IP and immunofluorescence assay confirmed the interaction between APOL3 and Y-box binding protein 1 (YBX1). Furthermore, YBX1 knockdown following APOL3 knockdown mitigated the enhanced proliferation. These results provide new ideas for clinically targeting APOL3 to inhibit proliferation in breast cancer. Conclusions: Our findings indicate that APOL3 inhibits breast cancer cell proliferation and cell cycle modulating P53 pathway through the interaction of YBX1.
摘要：
背景：乳腺癌是全球癌症相关死亡的第二大常见原因。载脂蛋白L3（APOL3），载脂蛋白家族的一员,与心血管疾病的发病机制有关。然而，APOL3在乳腺癌中的功能和潜在机制尚未阐明。方法：患者数据来自癌症基因组图谱（TCGA）和基因表达综合（GEO）数据库。实时定量PCR(qRT-PCR),西方印迹,和免疫组织化学（IHC）测定用于评估APOL3的表达。通过细胞计数试剂盒-8(CCK-8)和集落形成测定确定细胞增殖速率。流式细胞术用于检测细胞周期分布。免疫印迹法检测细胞周期相关蛋白的表达。使用异种移植模型来评价APOL3在体内的作用。通过质谱鉴定APOL3结合蛋白，免疫共沉淀(CO-IP)测定和免疫荧光测定。结果:APOL3在乳腺癌中表达明显下调,其低表达与预后不良相关。过表达APOL3抑制乳腺癌细胞增殖，诱导细胞周期破坏。相反，敲除APOL3促进细胞增殖。体内动物实验证明APOL3过表达可抑制肿瘤增殖。质谱,CO-IP和免疫荧光测定证实了APOL3和Y-box结合蛋白1(YBX1)之间的相互作用。此外，APOL3敲低后的YBX1敲低减轻了增强的增殖。这些结果为临床靶向APOL3抑制乳腺癌增殖提供了新思路。结论：我们的发现表明APOL3通过YBX1的相互作用抑制乳腺癌细胞增殖和细胞周期调节P53通路。
