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Retinol-binding Protein in the Urine of Cancer Patients¹

Department of Immunology Research, Roswell Park Memorial Institute,³ Buffalo, New York 14263

Large quantities of retinol-binding protein (RBP) were found in the urine of cancer patients with acquired Fanconi syndrome associated with Bence Jones proteinuria. The RBP concentrations in the urine specimens of three patients were 0.305, 0.274, and 0.217 mg of urine per ml while the amounts per 24-hr urine volume were 360, 343, and 329 mg, respectively. Immunological analysis of the urine specimens of these cancer patients showed that most of the RBP in the urine exists as free RBP. The RBP was isolated from the urine by a relatively simple procedure, and its chemical and immunological properties were studied. The molecular weight of RBP was 21,000, and its amino-terminal amino acid sequence for the first 18 positions was Glu-Arg-Asp-Cys-Arg-Val-Ser-Ser-Phe-Arg-Val-Lys-Glu-Asx-Phe-Asp-Lys-Ala. The polarity of the composition of this sequence is unusually high, i.e., 66.7%. The result suggests that this portion of the molecule is not directly involved in the interaction of RBP with retinol in view of the highly hydrophobic nature of retinol. The amino-terminal amino acid sequence of the urinary RBP was compared with 1065 reported sequences of proteins and peptides other than RBP by use of a computer, and no significant sequence homology was found with any of these sequences.

In immunological analysis, in which RBP was tested against antisera specific to 46 different serum and urinary protein components, the only antiserum that reacted was that to serum RBP (Behring Diagnostic).

Rabbit antiserum was prepared with the purified urinary RBP, and the antiserum was shown to be specific to RBP in the urine and serum without any prior absorption. Using the specific anti-RBP antiserum in the micro Ouchterlony immunodiffusion, we compared RBP in the sera of healthy donors and in the 24-hr urine specimens of several cancer patients with various malignant diseases. A complete coalescence was observed among the immunoprecipitin lines for the RBP in the normal sera and in the different cancer urine specimens, indicating an immunological identity among RBP's in these serum and urine specimens.

The quantity of RBP in the 24-hr urine decreased from 70.5 mg in the pretreatment specimen to 5.0 mg in the remission specimen for a plasma cell leukemia patient and similarly from 342.5 to 13.2 mg for a patient with acquired Fanconi syndrome associated with Bence Jones proteinuria.

¹ This investigation was supported by Grant No. AI08899 awarded by the National Institute of Allergy and Infectious Diseases and Grants CA17609 and CA19304 awarded by the National Cancer Institute, Department of Health, Education, and Welfare.

² To whom requests for reprints should be addressed, at Department of Immunology Research, Roswell Park Memorial Institute, 666 Elm Street, Buffalo, N. Y. 14263.

³ A unit of the New York State Department of Health.

Received 7/24/78. Accepted 8/ 8/79.