Boyle J O, Langenfeld J, Lonardo F, Sekula D, Reczek P, Rusch V, Dawson M I, Dmitrovsky E
Laboratory of Molecular Medicine and Head and Neck Service, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
J Natl Cancer Inst. 1999 Feb 17;91(4):373-9. doi: 10.1093/jnci/91.4.373.
Retinoids (derivatives of vitamin A) are reported to reduce the occurrence of some second primary cancers, including aerodigestive tract tumors. In contrast, beta-carotene does not reduce the occurrence of primary aerodigestive tract cancers. Mechanisms explaining these effective retinoid and ineffective carotenoid chemoprevention results are poorly defined. Recently, the all-trans-retinoic acid (RA)-induced proteolysis of cyclin D1 that leads to the arrest of cells in G1 phase of the cell cycle was described in human bronchial epithelial cells and is a promising candidate for such a mechanism. In this study, we have investigated this proteolysis as a common signal used by carotenoids or receptor-selective and receptor-nonselective retinoids.
We treated cultured normal human bronchial epithelial cells, immortalized human bronchial epithelial cells (BEAS-2B), and transformed human bronchial epithelial cells (BEAS-2BNNK) with receptor-selective or receptor-nonselective retinoids or with carotenoids and studied the effects on cell proliferation by means of tritiated thymidine incorporation and on cyclin D1 expression by means of immunoblot analysis. We also examined whether calpain inhibitor I, an inhibitor of the 26S proteasome degradation pathway, affected the decline (i.e., proteolysis) of cyclin D1.
Receptor-nonselective retinoids were superior to the carotenoids studied in mediating the decline in cyclin D1 expression and in suppressing the growth of bronchial epithelial cells. Retinoids that activated retinoic acid receptor beta or retinoid X receptor pathways preferentially led to a decrease in the amount of cyclin D1 protein and a corresponding decline in growth. The retinoid-mediated degradation of cyclin D1 was blocked by cotreatment with calpain inhibitor I.
Retinoid-dependent cyclin D1 proteolysis is a common chemoprevention signal in normal and neoplastic human bronchial epithelial cells. In contrast, carotenoids did not affect cyclin D1 expression. Thus, the degradation of cyclin D1 is a candidate intermediate marker for effective retinoid-mediated cancer chemoprevention in the aerodigestive tract.
据报道，类视黄醇（维生素A的衍生物）可降低某些第二原发性癌症的发生率，包括气消化道肿瘤。相比之下，β-胡萝卜素并不能降低原发性气消化道癌症的发生率。解释这些有效的类视黄醇和无效的类胡萝卜素化学预防结果的机制尚不清楚。最近，在人支气管上皮细胞中描述了全反式维甲酸（RA）诱导的细胞周期蛋白D1的蛋白水解，这导致细胞在细胞周期的G1期停滞，并且是这种机制的一个有希望的候选者。在本研究中，我们研究了这种蛋白水解作为类胡萝卜素或受体选择性和受体非选择性类视黄醇使用的共同信号。
我们用受体选择性或受体非选择性类视黄醇或类胡萝卜素处理培养的正常人支气管上皮细胞、永生化人支气管上皮细胞（BEAS-2B）和转化的人支气管上皮细胞（BEAS-2BNNK），并通过氚标记胸腺嘧啶掺入法研究对细胞增殖的影响，通过免疫印迹分析研究对细胞周期蛋白D1表达的影响。我们还检查了26S蛋白酶体降解途径的抑制剂钙蛋白酶抑制剂I是否影响细胞周期蛋白D1的下降（即蛋白水解）。
受体非选择性类视黄醇在介导细胞周期蛋白D1表达下降和抑制支气管上皮细胞生长方面优于所研究的类胡萝卜素。激活维甲酸受体β或类视黄醇X受体途径的类视黄醇优先导致细胞周期蛋白D1蛋白量的减少和相应的生长下降。钙蛋白酶抑制剂I共处理可阻断类视黄醇介导的细胞周期蛋白D1降解。
类视黄醇依赖性细胞周期蛋白D1蛋白水解是正常和肿瘤性人支气管上皮细胞中的一种常见化学预防信号。相比之下，类胡萝卜素不影响细胞周期蛋白D1表达。因此，细胞周期蛋白D1的降解是气消化道中有效类视黄醇介导的癌症化学预防的候选中间标志物。
