Dragnev Konstantin H, Pitha-Rowe Ian, Ma Yan, Petty W Jeffrey, Sekula David, Murphy Bryan, Rendi Mara, Suh Nanjoo, Desai Neil B, Sporn Michael B, Freemantle Sarah J, Dmitrovsky Ethan
Norris Cotton Cancer Center, and Department of Medicine, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
Clin Cancer Res. 2004 Apr 1;10(7):2570-7. doi: 10.1158/1078-0432.ccr-03-0271.
There is a need to identify cancer chemoprevention mechanisms. We reported previously that all-trans-retinoic acid (RA) prevented carcinogenic transformation of BEAS-2B immortalized human bronchial epithelial cells by causing G(1) arrest, permitting repair of genomic DNA damage. G(1) arrest was triggered by cyclin D1 proteolysis via ubiquitin-dependent degradation. This study investigated which chemopreventive agents activated this degradation program and whether cyclin E was also degraded.
This study examined whether: (a) cyclin E protein was affected by RA treatment; (b) cyclin degradation occurred in derived BEAS-2B-R1 cells that were partially resistant to RA; and (c) other candidate chemopreventive agents caused cyclin degradation.
RA treatment triggered degradation of cyclin E protein, and ALLN, a proteasomal inhibitor, inhibited this degradation. Induction of the retinoic acid receptor beta, growth suppression, and cyclin degradation were each inhibited in BEAS-2B-R1 cells. Transfection experiments in BEAS-2B cells indicated that RA treatment repressed expression of wild-type cyclin D1 and cyclin E, but ALLN inhibited this degradation. Mutation of threonine 286 stabilized transfected cyclin D1, and mutations of threonines 62 and 380 stabilized transfected cyclin E, despite RA treatment. Specific chemopreventive agents triggered cyclin degradation. Nonclassical retinoids (fenretinide and retinoid X receptor agonists) and a synthetic triterpenoid (2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid) each suppressed BEAS-2B growth and activated this degradation program. However, a vitamin D3 analog (RO-24-5531), a cyclooxygenase inhibitor (indomethacin), and a peroxisome proliferator-activated receptor gamma agonist (rosiglitazone) each suppressed BEAS-2B growth, but did not cause cyclin degradation. BEAS-2B-R1 cells remained responsive to nonclassical retinoids and to 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid.
Specific chemopreventive agents activate cyclin proteolysis. Yet, broad resistance did not occur after acquired resistance to a single agent. This provides a therapeutic rationale for combination chemoprevention with agents activating non-cross-resistant pathways.
有必要确定癌症化学预防机制。我们之前报道过，全反式维甲酸（RA）通过导致G1期阻滞，使基因组DNA损伤得以修复，从而预防了BEAS - 2B永生化人支气管上皮细胞的致癌转化。G1期阻滞是由细胞周期蛋白D1通过泛素依赖性降解的蛋白水解作用触发的。本研究调查了哪些化学预防剂激活了这一降解程序，以及细胞周期蛋白E是否也会被降解。
本研究检测了：（a）RA处理是否影响细胞周期蛋白E蛋白；（b）在对RA有部分抗性的衍生BEAS - 2B - R1细胞中是否发生细胞周期蛋白降解；（c）其他候选化学预防剂是否导致细胞周期蛋白降解。
RA处理触发了细胞周期蛋白E蛋白的降解，蛋白酶体抑制剂ALLN抑制了这种降解。在BEAS - 2B - R1细胞中，视黄酸受体β的诱导、生长抑制和细胞周期蛋白降解均受到抑制。BEAS - 2B细胞中的转染实验表明，RA处理抑制了野生型细胞周期蛋白D1和细胞周期蛋白E的表达，但ALLN抑制了这种降解。苏氨酸286的突变使转染的细胞周期蛋白D1稳定，苏氨酸62和380的突变使转染的细胞周期蛋白E稳定，尽管进行了RA处理。特定的化学预防剂触发了细胞周期蛋白降解。非经典类视黄醇（芬维A胺和视黄酸X受体激动剂）和一种合成三萜（2 - 氰基 - 3,12 - 二氧代齐墩果 - 1,9 - 二烯 - 28 - 酸）均抑制了BEAS - 2B的生长并激活了这一降解程序。然而，一种维生素D3类似物（RO - 24 - 5531）、一种环氧化酶抑制剂（吲哚美辛）和一种过氧化物酶体增殖物激活受体γ激动剂（罗格列酮）均抑制了BEAS - 2B的生长，但未导致细胞周期蛋白降解。BEAS - 2B - R1细胞对非经典类视黄醇和2 - 氰基 - 3,12 - 二氧代齐墩果 - 1,9 - 二烯 - 28 - 酸仍有反应。
特定的化学预防剂激活细胞周期蛋白蛋白水解作用。然而，对单一药物获得性耐药后并未出现广泛耐药。这为联合使用激活非交叉耐药途径的药物进行化学预防提供了治疗依据。
