Nuclear Localized LSR: A Novel Regulator of Breast Cancer Behavior and Tumorigenesis.
Nuclear Localized LSR: A Novel Regulator of Breast Cancer Behavior and Tumorigenesis.
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DOI：
10.1158/1541-7786.mcr-16-0085-t
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发表时间：
2017-02
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影响因子：
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通讯作者：
Fleming JM
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作者：
Reaves DK;Hoadley KA;Fagan-Solis KD;Jima DD;Bereman M;Thorpe L;Hicks J;McDonald D;Troester MA;Perou CM;Fleming JM
脂解刺激脂蛋白受体 (LSR) 已在质膜中发现，并被认为在脂蛋白内吞作用和紧密连接中发挥作用。鉴于细胞代谢和连接信号通路对肿瘤表型和患者结果的影响，了解 LSR 细胞定位如何介导其功能非常重要。我们进行了定位研究，评估了 DNA 结合，并检查了核 LSR 在细胞、异种移植物和临床标本中的影响。我们在代表多种内在亚型的乳腺癌细胞的膜、细胞质和细胞核中发现了 LSR。染色质免疫沉淀 (ChIP) 显示 LSR 与 DNA 直接结合，序列分析鉴定了 LSR 蛋白的假定功能基序和翻译后修饰。虽然转录变体的过度表达和翻译后修饰的药理学操作都没有显着改变定位，但核输出的抑制增强了核定位，这表明了核保留的机制。免疫共沉淀和近端连接测定表明 LSR-中心周蛋白相互作用，提出了核定位 LSR 的潜在机制。使用 1,100 多个原发性乳腺肿瘤的数据评估了 LSR 的临床意义，这些数据显示基底样肿瘤和非裔美国人的肿瘤中 LSR 水平较高。在肿瘤组织切片中，核定位与不良结果显着相关。最后，体内异种移植研究表明，过度表达 LSR 的基底样乳腺癌细胞表现出膜和核定位，并以 100% 外显率形成肿瘤，而缺乏 LSR 的对照细胞则未形成肿瘤。这些结果表明核 LSR 改变基因表达并可能促进侵袭性癌症表型。
Lipolysis Stimulated Lipoprotein Receptor (LSR) has been found in the plasma membrane and is believed to function in lipoprotein endocytosis and tight junctions. Given the impact of cellular metabolism and junction signaling pathways on tumor phenotypes and patient outcome, it is important to understand how LSR cellular localization mediates its functions. We conducted localization studies, evaluated DNA binding, and examined the effects of nuclear LSR in cells, xenografts, and clinical specimens. We found LSR within the membrane, cytoplasm, and the nucleus of breast cancer cells representing multiple intrinsic subtypes. Chromatin immunoprecipitation (ChIP) showed direct binding of LSR to DNA, and sequence analysis identified putative functional motifs and post-translational modifications of the LSR protein. While neither overexpression of transcript variants, nor pharmacological manipulation of post-translational modification significantly altered localization, inhibition of nuclear export enhanced nuclear localization, suggesting a mechanism for nuclear retention. Co-immunoprecipitation and proximal ligation assays indicated LSR-pericentrin interactions, presenting potential mechanisms for nuclear-localized LSR. The clinical significance of LSR was evaluated using data from over 1,100 primary breast tumors, which showed high LSR levels in basal-like tumors and tumors from African-Americans. In tumors histosections, nuclear localization was significantly associated with poor outcomes. Finally, in vivo xenograft studies revealed that basal-like breast cancer cells that over-express LSR exhibited both membrane and nuclear localization, and developed tumors with 100% penetrance, while control cells lacking LSR developed no tumors. These results show that nuclear LSR alters gene expression and may promote aggressive cancer phenotypes.