Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska.
The Fred and Pamela Buffett Cancer Center, Omaha, Nebraska.
Mol Cancer Res. 2023 Sep 1;21(9):958-974. doi: 10.1158/1541-7786.MCR-23-0108.
Prostate cancer progression to the lethal metastatic castration-resistant phenotype (mCRPC) is driven by αv integrins and is associated with Golgi disorganization and activation of the ATF6 branch of unfolded protein response (UPR). Overexpression of integrins requires N-acetylglucosaminyltransferase-V (MGAT5)-mediated glycosylation and subsequent cluster formation with Galectin-3 (Gal-3). However, the mechanism underlying this altered glycosylation is missing. For the first time, using HALO analysis of IHC, we found a strong association of integrin αv and Gal-3 at the plasma membrane (PM) in primary prostate cancer and mCRPC samples. We discovered that MGAT5 activation is caused by Golgi fragmentation and mislocalization of its competitor, N-acetylglucosaminyltransferase-III, MGAT3, from Golgi to the endoplasmic reticulum (ER). This was validated in an ethanol-induced model of ER stress, where alcohol treatment in androgen-refractory PC-3 and DU145 cells or alcohol consumption in patient with prostate cancer samples aggravates Golgi scattering, activates MGAT5, and enhances integrin expression at PM. This explains known link between alcohol consumption and prostate cancer mortality. ATF6 depletion significantly blocks UPR and reduces the number of Golgi fragments in both PC-3 and DU145 cells. Inhibition of autophagy by hydroxychloroquine (HCQ) restores compact Golgi, rescues MGAT3 intra-Golgi localization, blocks glycan modification via MGAT5, and abrogates delivery of Gal-3 to the cell surface. Importantly, the loss of Gal-3 leads to reduced integrins at PM and their accelerated internalization. ATF6 depletion and HCQ treatment synergistically decrease integrin αv and Gal-3 expression and temper orthotopic tumor growth and metastasis.
Combined ablation of ATF6 and autophagy can serve as new mCRPC therapeutic.
前列腺癌向致命转移性去势抵抗型（mCRPC）的进展是由αv 整联蛋白驱动的，与高尔基体解体和未折叠蛋白反应（UPR）的 ATF6 分支的激活有关。整联蛋白的过表达需要 N-乙酰氨基葡萄糖转移酶-V（MGAT5）介导的糖基化和随后与半乳糖凝集素-3（Gal-3）的簇形成。然而，这种改变的糖基化的机制尚不清楚。我们首次使用 HALO 分析免疫组化，在原发性前列腺癌和 mCRPC 样本中发现整合素αv 和 Gal-3 在质膜（PM）上有很强的相关性。我们发现，MGAT5 的激活是由高尔基体片段化和其竞争物 N-乙酰氨基葡萄糖转移酶-III（MGAT3）从高尔基体向内质网（ER）的错误定位引起的。在乙醇诱导的 ER 应激模型中得到了验证，在该模型中，酒精处理去势抵抗型 PC-3 和 DU145 细胞或酒精摄入前列腺癌患者样本会加重高尔基体散射，激活 MGAT5，并增强 PM 处的整合素表达。这解释了已知的饮酒与前列腺癌死亡率之间的联系。ATF6 的耗竭显著阻断 UPR 并减少 PC-3 和 DU145 细胞中高尔基体片段的数量。通过羟氯喹（HCQ）抑制自噬可恢复紧凑的高尔基体，挽救 MGAT3 在高尔基体内部的定位，阻断通过 MGAT5 的糖基化修饰，并阻止 Gal-3 递送到细胞表面。重要的是，Gal-3 的缺失导致 PM 处的整合素减少及其加速内化。ATF6 的耗竭和 HCQ 处理协同降低整合素αv 和 Gal-3 的表达，并缓和原位肿瘤生长和转移。
联合消融 ATF6 和自噬可以作为新的 mCRPC 治疗方法。
