Webber M M, Bello-DeOcampo D, Quader S, Deocampo N D, Metcalfe W S, Sharp R M
Department of Zoology, Michigan State University, East Lansing, 48824-1312, USA.
Clin Exp Metastasis. 1999 May;17(3):255-63. doi: 10.1023/a:1006665616932.
A long latent period of 20 to 30 years may be involved in the multistep process of carcinogenesis represented by prostatic intraepithelial neoplasia (PIN) in the prostate. It is, therefore, possible that progression to a malignant state could be blocked or reversed during this time. Retinoids not only have the ability to block steps in the process of carcinogenesis but they may also modulate or reverse some malignant characteristics of cancer cells. This study focuses on the ability of N-(4-hydroxyphenyl)-retinamide (4-HPR), a synthetic retinoid, to reverse malignant characteristics towards a normal phenotype, using the human prostate carcinoma cell line DU-145. These malignant characteristics include abnormal cell proliferation, intermediate filament expression, motility, invasion, and cell survival. Results show that 1 microM and 10 microM 4-HPR caused 31% and 96% inhibition of growth, while all-trains retinoic acid (ATRA) produced similar effects at 10 and 100 microM, making 4-HPR ten times more effective than ATRA. While DU-145 cells show strong immunostaining for vimentin, treatment with 1 microM 4-HPR for eight days caused a marked decrease in vimentin staining. This was accompanied by a change from an elongated to an epithelial cell morphology. Densitometric analysis of Western blots for vimentin showed a 53% decrease in vimentin expression in 1 microM 4-HPR treated cells. Concomitant with the decrease in vimentin expression, cell motility and invasive ability also decreased by 32% and 52%, respectively. Growth inhibition was accompanied by DNA fragmentation and apoptosis. Exposure of cells to 1 microM 4-HPR caused a marked upregulation of nuclear retinoid receptors RARalpha and a detectable expression of RARgamma. These results suggest that inhibition of growth and vimentin expression, and induction of apoptosis by 4-HPR in prostate cancer cells may occur via a receptor-mediated mechanism involving transrepression of AP-1 by retinoid receptors. We propose that vimentin may serve as a useful intermediate marker for early detection of prostate cancer in biopsy specimens and that 4-HPR may be effective in blocking several steps in prostate carcinogenesis as well as the progression of PIN to invasive carcinoma.
前列腺癌发生的多步骤过程可能涉及20至30年的漫长潜伏期，前列腺上皮内瘤变（PIN）即为其表现形式。因此，在此期间有可能阻止或逆转向恶性状态的进展。维甲酸不仅能够阻断致癌过程中的各个步骤，还可能调节或逆转癌细胞的某些恶性特征。本研究聚焦于合成维甲酸N-（4-羟苯基）维甲酰胺（4-HPR）使用人前列腺癌细胞系DU-145将恶性特征逆转为正常表型的能力。这些恶性特征包括异常细胞增殖、中间丝表达、运动性、侵袭能力和细胞存活能力。结果显示，1微摩尔和10微摩尔的4-HPR分别导致31%和96%的生长抑制，而全反式维甲酸（ATRA）在10微摩尔和100微摩尔时产生类似效果，使得4-HPR的效果比ATRA强十倍。虽然DU-145细胞对波形蛋白显示出强免疫染色，但用1微摩尔4-HPR处理八天导致波形蛋白染色显著减少。这伴随着细胞形态从细长形转变为上皮细胞形态。波形蛋白的蛋白质免疫印迹光密度分析显示，在1微摩尔4-HPR处理的细胞中波形蛋白表达减少了53%。与波形蛋白表达减少同时发生的是，细胞运动性和侵袭能力分别也降低了32%和52%。生长抑制伴随着DNA片段化和细胞凋亡。将细胞暴露于1微摩尔4-HPR导致核维甲酸受体RARα显著上调以及RARγ的可检测表达。这些结果表明，4-HPR对前列腺癌细胞生长和波形蛋白表达的抑制以及凋亡诱导可能通过一种受体介导的机制发生，该机制涉及维甲酸受体对AP-1的反式抑制。我们提出波形蛋白可能作为活检标本中前列腺癌早期检测的有用中间标志物，并且4-HPR可能有效地阻断前列腺癌发生的几个步骤以及PIN向浸润性癌的进展。
