Modulation of the expression of alkaline phosphatase genes in a human malignant cell line passaged through nude mice.

Hep 2/5 cells, a clone of HeLa which expresses both placental-type alkaline phosphatase and fetal intestinal alkaline phosphatase (ALP), were grown as solid tumors in nude mice. Analysis of ALP isozymes present in tumor specimens excised at intervals over a 52-day period showed that levels of placental-type ALP had dropped markedly, while levels of the intestinal ALP remained fairly constant. Cells re-cultured from two separate tumors regained most of the original placental ALP levels. However, levels of the fetal intestinal ALP in cells returned to culture rapidly increased to more than six times the levels in the original cultured cells, and these increased levels persisted. Passage through nude mice thus induced at least semi-permanent changes in the level of expression of fetal intestinal ALP in Hep 2/5 cells, and the nature of these changes may relate to the role of the isozyme locus in malignant cells.