Megakaryocyte potentiation factor cleaved from mesothelin precursor is a useful tumor marker in the serum of patients with mesothelioma.
OBJECTIVE
To establish monoclonal antibodies (mAb) against megakaryocyte potentiation factor (MPF) and detect MPF in the blood of patients with mesothelioma.


METHODS
Mice were immunized with a purified recombinant human MPF-rabbit-Fc fusion protein and with MPF. Several hybridomas producing mAbs to MPF were established. A double-determinant (sandwich) ELISA was constructed using mAbs to two different epitopes and used to determine if MPF is present in the serum of patients with mesothelioma.


RESULTS
We established seven anti-MPF mAbs whose topographical epitopes were classified into three nonoverlapping groups. All the mAbs reacted with recombinant MPF protein by ELISA. One of the mAbs detected MPF and the mesothelin precursor protein containing MPF in cell lysates on Western blotting. A sandwich ELISA using mAbs to two different epitopes was constructed and used to measure the presence of MPF in the media of various mesothelin-expressing cancer cell lines and in human serum. The ELISA showed that MPF levels were elevated in 91% (51 of 56) of patients with mesothelioma compared with healthy controls. Furthermore, serum MPF fell to normal levels in two patients after surgery for their peritoneal mesothelioma.


CONCLUSIONS
Using new mAbs to MPF, we showed that MPF is secreted by several mesothelioma cell lines and is frequently elevated in the blood of patients with mesothelioma. Measurement of MPF may be useful in following the response of mesothelioma to treatment.
Onda
Masanori
M
Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland 20892-4264, USA.
Nagata
Satoshi
S
Ho
Mitchell
M
Bera
Tapan K
TK
Hassan
Raffit
R
Alexander
Richard H
RH
Pastan
Ira
I
D000368:Aged; D000911:Antibodies, Monoclonal / Q000737:chemistry; D014408:Biomarkers, Tumor; D015153:Blotting, Western; D002469:Cell Separation; D004797:Enzyme-Linked Immunosorbent Assay; D018604:Epitope Mapping; D000939:Epitopes / Q000737:chemistry; D005260:Female; D058851:GPI-Linked Proteins; D006801:Humans; D006825:Hybridomas; D008175:Lung Neoplasms / Q000097:blood / Q000175:diagnosis* / Q000378:metabolism*; D008297:Male; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000502:physiology*; D000090204:Mesothelin; D008654:Mesothelioma / Q000097:blood / Q000175:diagnosis* / Q000378:metabolism*; D008875:Middle Aged
D000911:Antibodies, Monoclonal; D014408:Biomarkers, Tumor; D000939:Epitopes; D058851:GPI-Linked Proteins; D008562:Membrane Glycoproteins; C000715528:Msln protein, mouse; D000090204:Mesothelin