Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
Department of Biology, Spelman College, Atlanta, Georgia.
Cancer Prev Res (Phila). 2020 Aug;13(8):661-672. doi: 10.1158/1940-6207.CAPR-20-0054. Epub 2020 May 20.
Prostate cancer chemoprevention by sulforaphane, which is a metabolic by-product of glucoraphanin found in broccoli, in preclinical models is associated with induction of both apoptosis and autophagy. However, the molecular mechanism underlying sulforaphane-mediated autophagy, which is protective against apoptotic cell death by this phytochemical, is still poorly understood. This study demonstrates a role for lysosome-associated membrane protein 2 (LAMP2) in sulforaphane-mediated autophagy and apoptosis. Western blotting revealed dose-dependent induction of LAMP2 protein after treatment with sulforaphane as well as its naturally occurring analogs in PC-3 and 22Rv1 human prostate cancer cell lines that was confirmed by microscopy (sulforaphane). The mRNA level of was also increased upon treatment with sulforaphane in both cell lines. Sulforaphane-mediated increase in the level of autophagy marker microtubule-associated protein light-chain 3B was augmented by RNAi of LAMP2 in PC-3 and 22Rv1 cells. Apoptosis induction by sulforaphane treatment was also increased significantly by knockdown of the LAMP2 protein in PC-3 and 22Rv1 cells. Augmentation of sulforaphane-mediated apoptosis by RNAi of LAMP2 was accompanied by induction and activation of proapoptotic protein Bak. Oral administration of sulforaphane to TRAMP mice also resulted in induction of LAMP2 protein expression. Targeted microarray in sulforaphane-treated PC-3 cells revealed induction of many autophagy-related genes (e.g., ) and their expression positively correlated with that of in prostate cancer The Cancer Genome Atlas. In conclusion, this study reveals that induction of LAMP2 by sulforaphane inhibits its ability to induce apoptotic cell death at least in human prostate cancer cells.
西兰花中发现的萝卜硫素的代谢产物——硫代葡萄糖苷，可预防前列腺癌，其在临床前模型中与细胞凋亡和自噬的诱导有关。然而，这种植物化学物质诱导自噬的分子机制，即通过自噬来防止细胞凋亡，仍知之甚少。本研究表明溶酶体相关膜蛋白 2（LAMP2）在萝卜硫素介导的自噬和凋亡中的作用。Western blot 显示，在 PC-3 和 22Rv1 人前列腺癌细胞系中，萝卜硫素及其天然类似物处理后，LAMP2 蛋白呈剂量依赖性诱导，显微镜观察也证实了这一点（萝卜硫素）。在用萝卜硫素处理这两种细胞系后，的 mRNA 水平也增加了。在 PC-3 和 22Rv1 细胞中，用 RNAi 敲低 LAMP2 可增强萝卜硫素介导的自噬标志物微管相关蛋白轻链 3B 的水平。用萝卜硫素处理诱导细胞凋亡，也可显著增加 PC-3 和 22Rv1 细胞中 LAMP2 蛋白的敲低。用 RNAi 敲低 LAMP2 增强萝卜硫素介导的细胞凋亡，同时诱导和激活促凋亡蛋白 Bak。TRAMP 小鼠口服萝卜硫素也导致 LAMP2 蛋白表达的诱导。在萝卜硫素处理的 PC-3 细胞中进行的靶向微阵列显示，许多自噬相关基因（如）被诱导，其表达与前列腺癌 The Cancer Genome Atlas 中 LAMP2 的表达呈正相关。总之，本研究表明，萝卜硫素诱导 LAMP2 的表达，至少在人前列腺癌细胞中抑制了其诱导细胞凋亡的能力。
