Scientists at Bio-Rad Pty. Ltd. in Victoria, Australia, andcollaborators showed that a porphyrin compound can sensitizeotherwise incurable brain cancer to radiation andchemotherapy.
Brain tumors called high-grade gliomas kill 10,000 Americansannually. In lab mice, the Australians and colleagues at theUniversity of California, San Francisco, combined twosensitizing treatments, light sensitization by porphyrin (PDT)and neutron capture by boron.
The boronated protoporphyrin selectively localized in tumor atratios as high as 400-1 relative to normal brain tissues.
Light activates porphyrin to generate a toxic substance,probably reactive oxygen, the researchers wrote in the March 1Proceedings of the National Academy of Sciences. Incombination, a beam of thermal neutrons are able to activateboron-10, even deep within the brain, with highly localizedgeneration of reactive particles.
The problem with porphyrin alone has been that light cannotpenetrate to deep tumors. And for boron, previously availablecarriers have not localized in tissues. But linked to porphyrin,boron accumulated in the mitochondria of the tumor cells, theresearchers reported.
The selectivity of uptake suggests that the new compound,BOPP, can be a "dual-mode sensitizer ... as adjuvants toconventional surgery in the control of intractable tumors," thescientists wrote.
The Australian company is a unit of Bio-Rad Laboratories(AMEX:BIOA) of Hercules, Calif. Quadra Logic Technologies Inc.(NASDAQ:QLTIF) of Vancouver, British Columbia, and Tokyo-based Nippon Oil Co. Ltd. are developing porphyrin-basedcompounds for cancer therapy.
-- Roberta Friedman, Ph.D. Special to BioWorld
(c) 1997 American Health Consultants. All rights reserved.