Extract

To the Editor:

Immunoreactive prostate-specific antigen (PSA) has been detected in the sera of female and male renal cell carcinoma (RCC) patients in several studies (1)(2)(3). These measurements were attributed to the tumor because PSA reverted to undetectable concentrations after nephrectomy. However, attempts to definitively ascribe this increase to PSA were not successful either by immunohistochemistry with PSA monoclonal antibodies (1)(2) or by amplification of PSA by reverse transcription-PCR (RT-PCR) (3), suggesting cross-reaction with a PSA-like protein. Prostaglandin D synthase (PGDS) in amniotic fluid has been found to cross-react with a PSA polyclonal antibody, but not with PSA monoclonal antibodies (4). PGDS is present in the kidney (5) and is increased in the serum of patients with renal failure (6)(7). Because the Chiron PSA immunoassay (ACS:180) used in our original study (3) utilizes a polyclonal antibody, albeit immunopurified, we investigated whether PGDS could be responsible for the increased concentrations of PSA detected in RCC patients.

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