2-Methyl 2-butanol suppresses human retinoblastoma cells through cell cycle arrest and autophagy

2-Methyl-2-butanol (MBT) is a chemical compound from the group of alcohols more specifically pentanols, which has shown an excellent anti-cancer activity in our previous study. However, its mechanism of action remains unclear. The present study was designed to investigate the anti-cancer effect of MBT on human retinoblastoma cells. The results showed that the use of MBT leads to HXO-RB44 cell death but is cytotoxic to normal cells at higher concentrations. It showed a dose- as well as a time-dependent inhibition of HXO-RB44 cells. P27 is a cell cycle inhibitory protein, which plays an important role in cell cycle regulation whereas cyclin-B1 is a regulatory protein involved in mitosis. MBT increased the cell cycle arrest in a dose-dependent manner by augmenting p27 and reducing cyclin B1 expression. Moreover, it also accelerated apoptosis, increased light chain-3 (LC-3) conversion in a dose-dependent manner, and helped to debulk cancerous cells. LC3 is a soluble protein, which helps to engulf cytoplasmic components, including cytosolic proteins and organelles during autophagy from autophagosomes. In order to verify the effect of MBT, bafilomycin A1, an autophagy inhibitor, was used to block the MTB-induced apoptosis and necrosis. Additionally, a specific Akt agonist, SC-79, reversed the MBT-induced cell cycle arrest and autophagy. Thus, from the present study, it was concluded that MBT induced cell cycle arrest, apoptosis and autophagy through the PI3K/Akt pathway in HXO-RB44 cells.

2-甲基-2-丁醇（2-Methyl-2-butanol, MBT）是一类醇类化合物，更具体地属于戊醇类。既往研究已证实其具有优异的抗癌活性，但其具体作用机制仍未阐明。本研究旨在探究MBT对人视网膜母细胞瘤细胞的抗癌效应。实验结果显示，MBT可诱导HXO-RB44细胞死亡，但在高浓度下会对正常细胞产生细胞毒性；其对HXO-RB44细胞的抑制作用呈现剂量依赖性与时间依赖性。P27是一种细胞周期抑制蛋白，在细胞周期调控中发挥关键作用；而细胞周期蛋白B1（cyclin-B1）是参与有丝分裂的调控蛋白。MBT可通过上调p27蛋白表达、下调细胞周期蛋白B1表达，以剂量依赖性方式诱导细胞周期阻滞。此外，MBT还可加速细胞凋亡，以剂量依赖性方式增强轻链3（LC-3）的转化，并有助于减轻肿瘤负荷。LC3是一种可溶性蛋白，在自噬过程中可参与包裹胞质组分（包括胞质蛋白与细胞器）以形成自噬体。为验证MBT的上述效应，本研究使用自噬抑制剂巴弗洛霉素A1（bafilomycin A1）阻断MBT诱导的细胞凋亡与坏死。此外，特异性Akt激动剂SC-79可逆转MBT引发的细胞周期阻滞与自噬。综上，本研究结果表明，MBT可通过PI3K/Akt通路诱导HXO-RB44细胞发生细胞周期阻滞、凋亡及自噬。