Immunohistochemical demonstration of placental alkaline phosphatase in various states of testicular development and in germ cell tumours

Abstract

Immunohistochemical localization of placental alkaline phosphatase (PlAP) has been performed on eighty-two samples of normal (embryonic, fetal, infantile or adult), cryptorchid or tumorous testicular tissue. The isoenzyme could be demonstrated at the cell membrane of primitive, embryonic germ cells but not in other normal tissues. In-situ carcinomas and seminomas were positively stained in 93% and 94% of cases respectively. The percentage of positivity decreased with tumour differentiation. It is suggested that PlAP is a marker of primitive germ cells and that it reappears in germ cell neoplasms by gene derepression.

Lack of p19INK4d in human testicular germ-cell tumours contrasts with high expression during normal spermatogenesis

“…As the ®rst step, an immunohistochemical analysis of six prenatal testis specimens (obtained from abortions or upon deaths due to premature birth) from human foetuses between 15 weeks of gestation and birth was performed using either single-antibody staining with DCS-100 against p19 INK4d , or double staining with DCS-100 and an antibody against placental alkaline phosphatase (PIAP). The latter antibody was chosen based on its established value as a marker of a signi®cant subset of human foetal germ cells, and the characteristic localization of this enzyme in the cytoplasm at the cell periphery (Hustin et al, 1987;Jùrgensen et al, 1995), thereby allowing any potential nuclear staining for p19 INK4d to be detected in such cells. No p19 INK4d protein was detected with either method, and examples of results obtained with either the double-staining approach (showing a cytoplasmic ring of PIAP positivity with antibody NCL-PLAP-8A9 from Novocastra Laboratories in a subset of foetal germ cells yet no detectable nuclear staining with the DCS-100 antibody) or the single-antibody staining for p19 INK4d are shown in Figure 2a and b, respectively.…”

The human VASA gene is specifically expressed in the germ cell lineage

“…As such, it appears to be a marker of totipotent cells rather than the germ cell lineage per se. Alkaline phosphatase, a marker used in classic studies of germ cell migration, is not reliably expressed in postmigratory germ cells and is not specific for the germ cell lineage (25). Many genes are expressed either during spermatogenesis or oogenesis, such as the mouse DEAD box PL10 gene, which is expressed only in the male germ line and appears to be involved in translational control during spermatogenesis (26).…”

Glutathione S-transferase expression in the human testis and testicular germ cell neoplasia

“…This is consistent with its expression in preneoplasia in other organs (Sato, 1989) and it shows a striking parallel with expression of placental alkaline phosphatase (PLAP). This latter enzyme is expressed in fetal germ cells, ITGCN (Hustin et al, 1987) and seminoma and is used as a marker in routine diagnosis. GST Pi appears to reliably distinguish ITGCN from normal spermatogonia but is not such a specific marker.…”