Human Breast Milk Kills Cancer Cells
June 30, 1999
(Discover Magazine) - When Catharina Svanborg and her research associates began mixing mothers' milk and cancer cells together seven years ago, she wasn't looking for a cure for cancer; she was after a way to fight germs.
Nevertheless, the physician and immunologist at Lund University in Sweden has discovered that a previously taken-for-granted component of ordinary human breast milk compels cancer cells — every type of cancer cell tested — to die.
Now Svanborg must prove her discovery, demonstrating to wary scientists that her surprising find is for real. So far, it hasn't been easy.
"It's an extremely important observation, interesting and provocative," says breast cancer researcher David Salomon of the National Cancer Institute. "But it's novel, and novelty always runs the risk of challenging the current dogma. A lot of times you run up against a brick wall of people who have tunnel vision."
It all began seven years ago, when her student Anders Hakansson rushed into Svanborg's office with perplexing news. He had been experimenting with human cancer cells, microbes and mothers' milk. (Cancer cells make popular experimental models because they come in standardized lab strains. In many important respects they behave just like other human cells in lab dishes.)
The idea was to pinpoint how the milk blocks bacteria from infecting other cells. But the cancer cells in this experiment were acting up.
"Their volume was decreasing," Hakansson recalls. "Their nuclei were shrinking. Something was wrong."
When Svanborg sat down at the microscope, she diagnosed the problem immediately. "The cancer cells are committing suicide."
Cells commit suicide all the time, a phenomenon called apoptosis, in which the body rids itself of old or unnecessary cells. They simply fall apart and are recycled.
For cancer cells, however, suicide is rare indeed. Their defining characteristic is uncontrolled reproduction. Yet somehow, the breast milk induced these cancer cells to take their own lives.
Could the discovery be developed into a cancer cure? Fortunately, much of Svanborg's work has prepared her for this specific research. She and her group had studied the nature and function of epithelial cells, the gut-lining cells that come into contact with breast milk in nursing infants. And they had experimented with mother's milk many times.
They had shown that it does a terrific job of blocking infection by pneumococcus bacteria, the cause of pneumonia, and that breast-fed children suffer significantly fewer ear and upper respiratory tract infections than babies who don't nurse.
And her team had already done much of the homework that would be needed. They had tracked down studies showing that breast milk also protects against cancer. She wondered what accounted for that discrepancy. Now she had at hand the results that might provide an answer.
It took more than two years before her team felt ready to share its discovery with the rest of the world. In August 1995 they announced that breast milk kills cancer cells and pinpointed the killer, which turned out to be the protein alpha-lactalbumin (alpha-lac for short). It helps produce lactose, the sugar found in milk.
Svanborg and her colleagues discovered that the protein was performing the decidedly unprotein-like trick of changing its shape — and that it was persuading cancer cells to commit suicide.
The discovery also suggested a possible explanation of how breast milk protects against cancer. Perhaps, Svanborg reasoned, the errant cells that give rise to malignancies first show up in infants. The key is breakneck reproduction, a characteristic of the cells lining an infant's gut. Some of these cells may proliferate out of control. That's called cancer. Or they may never fully mature or stabilize, lurking in the system like time bombs, ever ready to burst forth into tumors.
Transformed alpha-lac "targets not only cancer cells but all kinds of immature, rapidly growing cells, and leaves mature, stable cells alone," Svanborg says.
Alpha-lac, then, may be conducting surveillance missions within the nursing child, rooting out potentially malignant cells and encouraging properly growing cells to mature. Because the lining of the gut, a prime meeting point between the inside of the body and the hazards of the outside world, is a headquarters of the immune system, the vigilance may help the child's immune defenses develop.
John Stevens, a vice president of grants at the American Cancer Society, took notice. After reading the Svanborg team's research paper, he made a journey to Sweden.
"I had not known of Lund University before, but we found Catharina and her team to be very talented researchers, very dedicated, and their work fascinating."
A $200,000 grant made Svanborg's the only non-American lab with ACS support. So she got back to work with renewed enthusiasm.
"The grant gave us recognition," Svanborg says. "We came into this from nowhere, and the cancer society gave us the stamp of quality. Now the weight was on us to prove that this is real and reproducible."
That effort has taken another four years. In January, Svanborg released the team's most recent findings, bolstered by the work of new collaborators, including researchers from the renowned Karolinska Institute in Stockholm and Oxford University in England.
The studies explain how transformed alpha-lac snuffs out cancer and other risky cells, and characterizes the protein down to the molecular level. And they announced that not only does it kill cells, it eliminates pneumococcus bacteria, too. Svanborg, with her longstanding interest in infectious disease, is as excited about this finding as any. She envisions using alpha-lac as a tonic to stop infections before they begin.
The team has given the new protein a name: HAMLET for Human Alpha-lactalbumin Made LEthal to Tumor cells.
They now know just how the protein changes into a cancer assassin. One key is the acid content of its surroundings. When Svanborg initially prepared milk to pour over cells, she added acid to the solution, hoping to separate out the microbe blockers. Little did she know that this acid bath, like some magic potion, would transform the well-mannered alpha-lac into HAMLET.
But acid alone wasn't enough. Another mysterious factor was needed. That, too, turned out to be a component of the milk itself. (The lab has not yet made its identity public).
Now that the team can generate genetically engineered HAMLET, they can make changes in it, helping them learn the function of its structural parts.
The first step is to test HAMLET as a tumor killer in animals. Svanborg and her team hope that because HAMLET is a naturally occurring substance, it might not be toxic like so many other cancer drugs. They've already tried it in mice, who tolerate very high doses with no side effects.
If animal tests go well, the next trials will be with humans. That can take years. And then, says Svanborg, "A major pharmaceutical company must become convinced that this is worth their investment. But if we can demonstrate that HAMLET works, I think no major company would be able to refuse."
Copyright 1999 Discover Magazine. All rights reserved.