A new highly specific monoclonal antibody against placental alkaline phosphatase: a potential marker for the early detection of testis tumour

Abstract

Objective To develop specific monoclonal antibodies (mAbs) against human germ cell tumours. Materials and methods A single‐cell suspension obtained from tumour tissue fragments (consisting of both tumour and normal compartments) from a patient with seminoma was used as an immunogen. Spleen cells from immunized mice were used to develop mAbs. Tissue specificity, biochemical characteristics and competitive studies were analysed using immunocytochemical staining, dot blots and a Western blot analysis, to identify target antigen(s). Results The immunization protocol led to the development of 107 hybridomas, 90 of which were negative against the original tissue biopsies. The remaining 17 showed positivity against various tissue compartments. One selected mAb (ATC2) showed specific staining on germ cell tumours but not on normal tissues, and positive staining with some human tumour cell lines. The target antigen for ATC2 was confirmed to be placental alkaline phosphatase (PLAP) based on: Western blot analysis compared with commercially available PLAP; comparison of the data with another well‐known anti‐PLAP mAb (H17E2, although the two mAbs recognized different antigenic epitopes); heat resistance characteristics; high‐performance liquid chromatography of the ATC2 target antigen and purified PLAP. Conclusion The selected mAb ATC2 has high specificity for human germ cell tumours, the target antigen for ATC2 being PLAP, although the antigenic epitope(s) differ from those recognized by H17E2. Thus ATC2 may be useful for monitoring serum levels of PLAP in patients with testis cancer and may be relevant for detecting cancer cells in the semen of individuals with suspected testis cancer, particularly in those with equivocal findings on ultrasonography.

Isoenzima de fosfatasa alcalina placental-like, importancia clínica como marcador en tumores de tipo germinal

“…En el primer caso y debido a la localización intracraneal profunda y vascularización intrínseca tumoral, la biopsia de este tipo de tumores puede ser de mayor riesgo que las biopsias estereotáxicas de otros tipos de tumores en otras regiones. Por tanto, el valor de la prueba de imagen (TC o RMN) e interpretación de marcadores tumorales asociados, es definitivo para comenzar el tratamiento de estos pacientes, al ser tumores radio y quimiosensibles 9,14,15 . En tumores de origen pineal, podemos encontrar ciertos marcadores, ␤HCG, CEA y AFP normales, como ocurre en este caso, mientras que ALP total y su isoenzima tumoral están elevadas (PALP-like 75% de actividad).…”

“…La expresión ectópica de la isoenzima PLAP-like puede estar asociada al cáncer de pulmón, ovario, útero y tumores de origen germinal como cán-cer testicular: neoplasia intratubular de células germinales sin clasificar (IGCNU), seminoma, carcinoma embrionario y coriocarcinoma 9 . Se han encontrado concentraciones séricas elevadas de PLAP y PLAP-like en el 25-65% de los pacientes con cáncer de ovario 10 , y en un 22-89% de los pacientes con neoplasias testiculares 7,11,12 .…”

“…La información que nos ofrecen las pruebas de imagen como tomografía computarizada (TC) o resonancia magnética nuclear (RMN) y una buena interpretación de los marcadores tumorales asociados, es de gran importancia al inicio del tratamiento de pacientes aquejados de tumores de células germinales (TCG), debido a la condición de éstos, de ser radio y quimiosensibles y presentar una buena respuesta 9,14,15 . Este tipo de tumores producen un aumento de marcadores como alfafetoproteína (AFP) en tumores del seno endodérmico, carcinoma embrionario y ocasionalmente en teratomas.…”

Placental Alkaline Phosphatase in Pediatric Adrenocortical Cancer

“…The fourth type is 50% identical to the other 3 types, is not specific to tissues and can be found in bone, liver, and kidney. 12,15 PLAP is a cell surface glycosylphosphatidylinositolanchored protein but is also often found in serum, fluids, and tumor tissue of patients with certain types of cancer. The release of this enzyme in the membranes may occur through the action of phosphatidylinositol-specific phospholipase C. 16,17 PLAP is a dimeric enzyme that catalyzes the hydrolysis of phosphomonoesters with the release of inorganic phosphate and alcohol.…”

“…Several estimations of the molecular mass of each PLAP subunit have been presented: 58 to 74 kD, 15,[45][46][47] which may be related to several glycoforms and/or oligomers of the enzyme. 47 Of considerable interest is the fact that human APs are abundantly expressed in tumor cells and that their serum levels are often used as tumor markers.…”