1,N(6)-Etheno-2-aza-adenosine was synthesized by treating 1,N(6)-etheno-adenosine with alkali, followed by nitrosation. The mechanism of formation of this novel nucleoside was elucidated using adenosine tritiated at C-8 and C-2, and was found to deformylate exclusively at C-2. This new 2-aza nucleoside fluoresces at 494 nm when excited at 358 nm. Toxicity study showed the compound is active in a rat mammary tumor tissue culture line, but inactive in HeLa and Glioma 26 tissue culture lines. It was also found to selectively inhibit the thymidine incorporation into DNA in a rat mammary tumor, but exhibits no ill effect on normal proliferative tissue. The reactive intermediate 3-beta-D-ribofuranosyl-4-amino-5-(imidazol-2-yl) imidazole was identified and was found to be an active agent in tissue culture.

2,131 coded sera were obtained and tested according to the new 5'-NPDase-V isozyme test. On decoding, 99/126 (79%) samples of primary hepatoma, from the United States and other countries, were positive. In the U. S. group, 51/58 (88%) were positive, 23/58 (40%) had AFP higher than 20 ng/ml. In the non-U. S. group, 48/68 (71%) were positive for 5'-NPDase-V, as compared with AFP elevation in 45/68 (66%). 236/268 (88%) cases of cancer with known liver metastases were positive for 5'-NPDase-V. Of 1,040 cancer patients without liver scan or biopsy evidence of metastasis, 316 were positive. In a follow-up of this group of 316 cases, 109 underlying liver metastases were demonstrated by repeat scan or at autopsy within 3--6 months. All 166 sera from normal healthy persons were negative for 5'-NADase-V. Based on this large panel, 5'-NPDase-V test is a sensitive and an important diagnostic aid for cancer patients, both as an early predictor for liver metastases, and a useful marker for primary hepatoma when no other primary sites are found and when there is no evidence of severe chronic liver disease such as cirrhosis.

An abnormal, fast-moving 5'-nucleotide phosphodiesterase isozyme was found in 90.0% of 20 Malaysian patients with primary hepatoma and in 23.5% of 391 Malaysian patients with various malignant diseases; it was also discovered in 42.9% of 14 Malaysian and American patients with clinically active hepatitis B infection; in 16.7% of 18 healthy American blood bank donors who were positive for hepatitis B surface antigen (HBsAg); in 13.9% of 287 healthy Malaysian blood bank donors, some positive for HBsAg; and in none of 160 healthy American donors who were negative for HBsAg. A correlation of this abnormal isozyme with hepatoma and with infectious hepatitis B is clearly evident.

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