Jemmerson R, Shah N, Takeya M, Fishman W H
Cancer Res. 1985 Jan;45(1):282-7.
A431 human epidermoid carcinoma cells monophenotypically express the placental alkaline phosphatase (PLAP)-like enzyme shown by its catalytic and antigenic characteristics, properties which are shared by the Nagao isozyme. More specifically, it is L-leucine sensitive just as is the rare placental D-variant of PLAP and the testicular heat-stable enzyme. Collectively, these are all referred to as PLAP-like enzymes. The enzyme was localized to the surface of the plasma membrane since it was released in an active form by bromelain treatment of cells. The number of molecules per A431 cell was estimated by radioimmunoassay at 7.5 X 10(5), a value significantly higher than that observed for HeLa TCRC-1 cells (5 X 10(4) which express the S-variant of PLAP, also referred to as the Regan isozyme. The quantity of the enzyme was increased significantly (10-fold) by treating the cells with modulating agents including sodium butyrate, prednisolone, and hyperosmolar sodium chloride. The identification of a cell line such as A431 with enhanced expression in the amount of the PLAP-like enzyme and which can be further enhanced by modulating agents will facilitate studies of the differences and the similarities between this protein and other variants of PLAP. The A431 cell line now takes its place with other cell lines which are phenotypically restricted in their expression of alkaline phosphatase. Finally, the A431 cell line is also shown here to be a suitable model system for in vivo tumor studies such as immunolocalization.
A431人表皮样癌细胞单表型表达胎盘碱性磷酸酶（PLAP）样酶，其催化和抗原特性表明了这一点，这些特性与长野同工酶相同。更具体地说，它对L-亮氨酸敏感，就像PLAP罕见的胎盘D变体和睾丸热稳定酶一样。总的来说，这些都被称为PLAP样酶。该酶定位于质膜表面，因为通过菠萝蛋白酶处理细胞可使其以活性形式释放。通过放射免疫测定法估计每个A431细胞的分子数为7.5×10⁵，该值显著高于表达PLAP的S变体（也称为里根同工酶）的HeLa TCRC-1细胞（5×10⁴）。用包括丁酸钠、泼尼松龙和高渗氯化钠在内的调节剂处理细胞后，该酶的量显著增加（10倍）。鉴定出如A431这样的细胞系，其PLAP样酶的表达量增加，并且可以通过调节剂进一步增强，这将有助于研究该蛋白与PLAP其他变体之间的差异和相似性。A431细胞系现在与其他在碱性磷酸酶表达上受表型限制的细胞系并列。最后，这里还表明A431细胞系是体内肿瘤研究（如免疫定位）的合适模型系统。
