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

研究环氧合酶-2(COX-2)和前列腺素E_2(PG-E_2)在皮肤鳞状细胞癌(HSC-5)和小汗腺癌(ECCA)中的表达。与非致瘤性角质形成细胞系HaCaT相比，癌细胞株中COX-2的表达和PGE_2的产量均显著增加。为了确定COX-2在HSC-5和ECCA细胞增殖中的作用，采用四甲基偶氮唑盐比色法比较了COX-2反义寡核苷酸对HSC-5和ECCA细胞生长的影响。反义寡核苷酸可抑制COX-2蛋白的表达，并显著抑制细胞生长。比较选择性COX-2抑制剂NS398和反义寡核苷酸的作用。NS398对COX-2表达无明显影响，但对细胞生长有一定的抑制作用。反义寡核苷酸对细胞生长的抑制程度大于NS398。基于这些发现，我们寻找了抑制COX-2表达的药物，并检测了它们对细胞生长的影响。鉴于维甲酸和抗氧化剂已被用于多种组织的癌症化学预防，我们研究了这些药物对皮肤鳞癌细胞COX-2表达和PGE2生物合成的影响。维甲酸[9-顺式维甲酸(9-cis-RA)]或抗氧化剂[吡咯烷二硫代氨基甲酸酯(PDTC)]以浓度依赖的方式抑制COX-2的表达和PGE_2的生物合成。9-cis-RA和PDTC对细胞生长有明显的抑制作用，提示9-cis-RA和PDTC可能具有预防皮肤癌生长的作用，COX-2可能参与了它们对皮肤癌发生的保护作用。

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.