Tumor-Associated Antigen in Human Pancreatic Cancer2

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Abstract
New Zealand White rabbits were immunized with saline extracts of 1) a human pancreatic cancer cell line (MIA PaCa-2) 2) human pancreatic tumors excised from Swiss nu/nu mice, or 3) human pancreatic cancer tissue. Solid-phase immunoadsorbents rendered the resulting antisera specific. The antisera, tested by double immunodiffusion and counterimmunoelectrophoresis (CEP), detected the pancreatic antigen in saline extracts of human pancreatic carcinoma, human fetal pancreas, MIA PaCa-2 cells, a second human pancreatic cancer cell line (PANC-1), and nude mouse pancreatic tumors, but not in saline extracts of normal human pancreas and a number of other normal tissues, in normal human sera, or in sera from patients with active inflammatory disease. The antisera did not react with alpha-fetoprotein and carcinoembryonlc antigen. Sera of patients with pancreatic cancer and other neoplastic and nonneoplastic disorders were tested in CEP with two antisera: rabbit anti-MIA PaCa-2 and rabbit anti-human pancreatic carcinoma. Although both antisera detected the pancreatic antigen in 65–70% of the patients with biopsy-confirmed pancreatic carcinoma, the antihuman pancreatic carcinoma serum was less reactive with sera from patients having disorders not involving the pancreas. Rabbit anti-MIA PaCa-2 serum added to 5-day-old washed and fixed MIA PaCa-2 cells, followed by fluorescein-labeled goat antlrabblt serum, resulted in strong fluorescence located on the nuclear membranes. Additional antigen was released from saline-extracted cell membranes after treatment with Triton X-100. The estimated molecular weight of the tumor-associated pancreatic antigen was between 900×103 and 1,000×103 daltons. The antigen migrated in the β1 to α2 regions in agarose electrophoresis and was destroyed by 10% perchloric acid or by boiling.