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Dissolved in peanut oil, the promine and retine preparations are injected into mice to observe the effect on the animals' cancers. Dr. Szent-Gyorgyi's mouse house is across the yard from the lab building. There he has tested promine and retine on hundreds of tumors. Two of the three types of tumor he works with are favorites of researchers: transplanted from one animal to another, they grow fast, and give a quick indication of a drug's effects. Promine speeds the growth of these cancers; retine makes them grow more slowly and actually causes some tumors, already well grown, to shrink. Perhaps most important, retine also works in cancers that certain mice develop naturally, which makes them more nearly comparable to the human disease. And neither pro-mine nor retine seems to have any harmful incidental effects—in sharp contrast with virtually all anticancer drugs now in use.
Double the Retine? Nothing quite like promine and retine has been discovered before, although sex hormones and chemically related compounds are used in treating some forms of cancer. The commonest of the many kinds of cancer, Szent-Gyorgyi notes, are the types that usually develop in middle life. "We have some evidence from ani mals," he says, "that the body's output of both promine and retine may decline with advancing age. But what seems to be more important is that the ratio of the two substances changes. Later in life, the body makes proportionately less of the retarding retine. From our experiments so far, it looks as though changing the ratio back, by doubling the amount of retine, is necessary to make cancer regress."
Cancer researchers have had their hopes raised and then dashed so many times that they are jumping to no optimistic conclusions about Szent-Gyorgyi's latest work. Neither is he. "We have made only a preliminary report," he says. "We hope other laboratories will test our theory and help to prove or disprove it. I am already getting letters from all over, asking me to send 'the cancer cure.' There is no such thing, and I have not enough material even for other laboratories. The urgent thing is for other researchers to make and test these substances.
"Cancer is such a cruel disease," says Dr. Szent-Gyorgyi. He knows. Fortnight ago, his wife died of cancer, after a lingering, painful illness that began when he was in the midst of his retine research.
* In 1937, for demonstrating that the anti-scurvy vitamin is ascorbic acid, which he extracted by the pound from peppers.