Studies on the roles of the arachidonic acid cascade in the skin cancer development.

本文研究了人皮肤表皮癌细胞株HSC-5和小汗腺癌细胞株EcCa中考克斯-2的表达和前列腺素E_2（PG E_2）的产生。COX-2反义寡核苷酸转染人角质形成细胞系HaCaT后，考克斯-2表达和PGE_2的产生均明显高于正常人角质形成细胞系HaCaT，用MTT法比较考克斯-2反义寡核苷酸转染前后细胞生长情况，以探讨考克斯-2在HSC-5和EcCa增殖中的作用。转染反义寡核苷酸可抑制考克斯-2蛋白的表达，并显著抑制细胞生长。将考克斯-2的选择性抑制剂NS 398的作用与反义寡核苷酸的作用进行比较。NS 398处理后考克斯- 2表达无变化，而NS 398在一定程度上抑制细胞生长。反义寡核苷酸的生长抑制程度大于NS 398。基于这些发现，我们寻找抑制考克斯-2表达的药物，并检查它们对细胞生长的影响。由于类维生素A和抗氧化剂已被用于多种组织中的癌症的化学预防，因此研究了这些药物对皮肤鳞状细胞癌细胞中考克斯-2表达和PGE_2生物合成的影响。用维甲酸[9-cis-维甲酸（9-cis-RA）]或抗氧化剂[吡咯烷二硫代氨基甲酸酯（PDTC）]处理以浓度依赖性方式抑制考克斯-2表达和PGE_2生物合成。结果表明，9-cis-RA和PDTC对皮肤癌的生长有明显的抑制作用，而考克斯-2可能参与了它们对皮肤癌的保护作用。

The expression of COX-2 and prostaglandin (PG) E_2 production were investigated in two human skin epidermal cancer cell lines ; cutaneous squamous cell carcinoma, HSC-5 and eccrine carcinoma, EcCa. Both COX-2 expression and PGE_2 production were significantly enhanced in cancer cell lines compared to the nontumorigenic human keratinocyte cell line, HaCaT.In order to determine the role of COX-2 in the proliferation of HSC-5 and EcCa, the growth of untreated cells and cells transfected with COX-2 antisense oligonucleotide was compared by MTT proliferation assay. Transfection with the antisense oligonucleotide suppressed COX-2 protein expression and significantly inhibited cell growth. The effect of a selective inhibitor of COX-2, NS398, was compared with the effect of the antisense oligonucleotide. COX- 2 expression was unchanged by NS398 treatment, whereas NS398 inhibited cell growth to a certain extent. The degree of growth inhibition was greater with the antisense oligonucleotide than with NS398. Based on these findings, we searched for agents which suppress COX-2 expression and examine their effects on cell growth. Since retinoids and antioxidants have been used for chemoprevention of cancers in several tissues, the effects of these agents on COX-2 expression and PGE_2 biosynthesis in skin squamous carcinoma cells were investigated. Treatment with a retinoid [9-cis- retinoic acid (9-cis-RA)] or an antioxidant [pyrrolidinedithiocarbamate (PDTC)] suppressed COX-2 expression and PGE_2 biosynthesis in a concentration-dependent manner. Cell growth was significantly inhibited by 9-cis-RA and PDTC.These results suggest that 9-cis-RA and PDTC may be useful in preventing skin cancer growth and that COX-2 is involved in their protective effects on skin carcinogenesis.