Prevention of second tumors by polyprenoic acid, a new retinoid -
Retinoids, both natural and synthetic, have figured in attempts
at the chemoprevention of cancer; in general, retinoids like all-
trans- or cis-retinoic acid have been more active than such
compounds as vitamin A and carotene. The Hepatoma Prevention
Study Group in Japan reported in the June 13, 1996 issue of the New
England Journal of Medicine on their trial of a new retinoid,
polyprenoic acid, in 89 patients who had liver cancer, but were
now free of disease. They were randomly assigned to 600 mg daily
of polyprenoic acid or to placebo for six months, and any
recurrent or new (second primary tumors) liver tumors were
detected by ultrasound. At the end of this time, 49% of the
placebo patients had tumors versus 27% in those receiving
polyprenoic acid. More strikingly, only seven (16%) of the
polyprenoic acid group had second tumors compared with 20 (44%)
of those given placebo. (Muto, NEJ Med 334:1561, 1996)
Editor's Comment: - Although polyprenoic acid behaves like a
retinoid, its chemical structure, an open 20-carbon-atom chain,
is different in lacking a ring structure. This might have
advantages over natural and ring-containing retinoids if it
should alter the metabolic pattern. Metabolism of retinoids may
lessen their anticancer action, as can be seen in this month's
Cancer Web Report article on lung cancer.
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