Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: TUESDAY, March 27, 1990 TAG: 9003270337
SECTION: NATIONAL/INTERNATIONAL PAGE: A/4 EDITION: EVENING
SOURCE: Associated Press
DATELINE: DAYTONA BEACH, FLA. LENGTH: Medium
While it is too soon to tell if the strategy is working, some early signs give encouragement, said Eugenie Kleinerman of the M.D. Anderson Cancer Center in Houston.
The approach may also help some day with other forms of cancer, she said Monday at a seminar for science writers sponsored by the American Cancer Society.
The patients in her study have osteosarcoma, a childhood bone cancer that produces some 700 cases a year in the United States.
The cancer is treated with surgery to remove the bone tumor, plus chemotherapy to attack cancer cells that have spread elsewhere in the body.
Nonetheless, some 30 to 40 percent of patients die from cancer that had spread to their lungs before surgery, Kleinerman said.
Her therapy is aimed at destroying microscopic tumors in the lung by activating white cells called monocytes in the blood and others called macrophages in lung tissue. When activated, these cells kill cancerous cells, she said.
The white cells can be turned on by a drug called muramyl tripeptide phosphatidylethanolamine, abbreviated as MTP-PE, she said.
The drug is enclosed in the tiny fat bubbles because monocytes and macrophages readily digest them. Once devoured, a bubble spills its load of MTP-PE, activating the cell to fight cancer.
In this fashion, the drug can be delivered only to the desired cells, which cuts down on side effects, Kleinerman said.
The bubbles, called liposomes, are about the size of red blood cells, she said.
In mice, the strategy was able to eliminate cancer that had spread to the lung, she said. It also worked in dogs, even without help from chemotherapy.
The current study has so far enrolled 14 children for whom chemotherapy has failed and whose cancers have spread to the lung.
Participants have been getting liposomes bearing MTP-PE intravenously twice a week as outpatients for three months or six months. An earlier study showed that side effects are minimal, including fever and chills.
Kleinerman said it is too early to see if the strategy is working in the new study. But participants' lungs show dead cancer cells and scar tissue around tumors, indicating that the treatment is having some kind of effect, she said.
If the liposome strategy does work, she hopes it will be combined with chemotherapy after the initial bone tumor is removed. The idea is that the activated monocytes and macrophages would kill cancer cells that resist the chemotherapy.
She also said the strategy may pay off for other cancers that spread to the lung, such as the skin cancer melanoma, or which spread to the liver, such as colon cancer. Liposomes are taken up by the liver and spleen as well as the lung, she said.
Asked about prospects for treating lung cancer, she said she knew of no studies of that possibility.
John Weinstein of the National Cancer Institute, who has studied liposomes, said previous studies give "a good rationale for going forward" with the work Kleinerman is doing.
by CNB