Zhang Qi-Cheng, Pan Zhen-Hua, Liu Bo-Ning, Meng Zhao-Wei, Wu Xiang, Zhou Qing-Hua, Xu Ke
Tianjin Key Laboratory of Lung Cancer Metastasis and Tumor Microenvironment, Tianjin Lung Cancer Institute, Tianjin Medical University General Hospital, Tianjin 300052, China.
Department of Nuclear Medicine, Tianjin Medical University General Hospital, Tianjin 300052, China.
Acta Pharmacol Sin. 2017 Apr;38(4):539-550. doi: 10.1038/aps.2016.146. Epub 2017 Jan 23.
Isothiocyanates, such as allyl isothiocya¬nate (AITC), benzyl isothiocyanate (BITC), phenethyl isothio¬cyanate (PEITC) and sulforaphane (SFN), are natural compounds abundant in cruciferous vegetables, which have substantial chemopreventive activities against various human malignancies. However, the mechanisms underlying the inhibition of tumor cell growth by isothiocyanates are not fully understood. Since autophagy has dual functions in cancer, in the present study we investigated the effects of BITC on autophagy induction in human lung cancer cells in vitro and in vivo. BITC (1-100 μmol/L) dose-dependently inhibited the growth of 3 different human lung cancer cell lines A549 (adenocarcinoma), H661 (large cell carcinoma) and SK-MES-1 (squamous cell carcinoma) with IC values of 30.7±0.14, 15.9±0.22 and 23.4±0.11 μmol/L, respectively. BITC (10-40 μmol/L) induced autophagy in the lung cancer cells, evidenced by the formation of acidic vesicular organelles (AVOs), the accumulation of LC3-II, the punctate pattern of LC3, and the expression of Atg5. Pretreatment with the autophagy inhibitor 3-MA (5 mmol/L) significantly enhanced the BITC-caused growth inhibition in the lung cancer cells. Furthermore, BITC (20-40 μmol/L) activated ER stress, as shown by the increased cytosolic Ca level and the phosphorylation of the ER stress marker proteins PERK and eIF2α in the lung cancer cells. Pretreatment with the ER stress inhibitor 4-PBA (5 mmol/L) attenuated the autophagy induction and potentiated the BITC-induced cell growth inhibition. In nude mice bearing A549 xenografts, administration of BITC (100 mg·kg·d, ip) for 8 weeks markedly suppressed the lung tumor growth, and significantly enhanced both autophagy and ER stress in the tumor tissues. Our results demonstrate that BITC inhibits human lung cancer cell growth in vitro and in vivo. In addition, BITC induces autophagy in the lung cancer cells, which protects the cancer cells against the inhibitory action of BITC; the autophagy induction is mediated by the ER stress response.
异硫氰酸酯，如烯丙基异硫氰酸酯（AITC）、苄基异硫氰酸酯（BITC）、苯乙基异硫氰酸酯（PEITC）和萝卜硫素（SFN），是十字花科蔬菜中富含的天然化合物，对多种人类恶性肿瘤具有显著的化学预防活性。然而，异硫氰酸酯抑制肿瘤细胞生长的机制尚未完全明确。由于自噬在癌症中具有双重作用，在本研究中，我们研究了BITC在体外和体内对人肺癌细胞自噬诱导的影响。BITC（1-100μmol/L）以剂量依赖性方式抑制3种不同的人肺癌细胞系A549（腺癌）、H661（大细胞癌）和SK-MES-1（鳞状细胞癌）的生长，IC值分别为30.7±0.14、15.9±0.22和23.4±0.11μmol/L。BITC（10-40μmol/L）诱导肺癌细胞自噬，酸性囊泡细胞器（AVO）的形成、LC3-II的积累、LC3的点状模式以及Atg5的表达均证明了这一点。用自噬抑制剂3-MA（5mmol/L）预处理可显著增强BITC对肺癌细胞生长的抑制作用。此外，BITC（20-40μmol/L）激活内质网应激，肺癌细胞中胞质Ca水平升高以及内质网应激标记蛋白PERK和eIF2α的磷酸化表明了这一点。用内质网应激抑制剂4-PBA（5mmol/L）预处理可减弱自噬诱导并增强BITC诱导的细胞生长抑制作用。在携带A549异种移植瘤的裸鼠中，给予BITC（100mg·kg·d，腹腔注射）8周可显著抑制肺肿瘤生长，并显著增强肿瘤组织中的自噬和内质网应激。我们的结果表明，BITC在体外和体内均能抑制人肺癌细胞生长。此外，BITC诱导肺癌细胞自噬，这保护癌细胞免受BITC的抑制作用；自噬诱导是由内质网应激反应介导的。
