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Cellular alkaline phosphatases (ALP) are increasingly recognised as important markers for monitoring tumour cell behaviour in human malignancies. Colorimetric, flow-cytometric, and immunocytochemical assays were employed to assess the influence of activation on expression of cellular ALP in human tumour cell lines. The results showed the following: (1) Testis tumour biopsies (16/16) unlike bladder (0/14) and head and neck (0/16) tumours showed positive staining for ALP, particularly the placental type, i.e. PLAP, although this was not always present on all the cells of non-seminoma biopsies. (2) The intensity of ALP expression differed widely in tumour cell lines. Based on biochemical analysis, the profile of ALP fell into two categories: (a) low expressing (MW 70 kD, placental type ALP) like Hep2 and KB lines, and (b) those expressing both low and high molecular (MW 95 kD) bands like testis lines Tera II and Ep2102. In all cases treatment of tumour cell lysates with heat prior to biochemical analysis showed the disappearance of the higher and sharpening of the lower molecular weight ALP band. (3) Exposure of tumour cells to epidermal growth factor (EGF) expressing EGF receptor led to a decreased ALP expression by as much as 54% as assessed by biochemical or flow-cytometric techniques. These data demonstrated that testis tumour tissues and cell lines expressed ALP which were different from others. The data also showed that exposure of tumour cell lines expressing EGFr to EGF resulted in suppression of ALP expression. These observations are consistent with the notion that EGFr and PLAP expression may be taken as a marker of proliferation and differentiation in human malignancies, respectively.

Objective To establish the specificity and sensitivity of alkaline phosphatase activity in testicular tumours for the early detection of testicular germ cell tumours (GCTs). Materials and methods Samples from patients with GCTs of the testis were sectioned and stained using the nitroblue tetrazolium salt (NBT)/5 bromo-4-chloro-3-indolylphosphate (BCIP) Sigma Fast substrate technique (referred to as MEDC) and peroxidase anti-peroxidase (PAP) assay. Additionally, several cell lines from GCTs and other tumours were cultured using standard techniques and stained using both methods, and lysates from all samples were stained after gel electrophoresis. Results MEDC showed strong and specific staining of testicular tumours only. The activity on gel electrophoresis appeared as two bands, one at 75 and one at 95 kDa, which was a unique combination for testicular tumours and testis cell lines. Conclusion The MEDC method has extreme sensitivity and intensityfor testicular tumour tissue and has potential use as a powerful tool for the early detection of testicular GCTs by analysing semen samples, particularly in patients with equivocal findings on testicular ultrasonography.