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News — In an unexpected result, human cancer cells injected into a new animal model act in a manner similar to the way they do in humans, and may represent a new method for understanding and treating virtually all tumors.

"It's a model for studying the mechanisms for how cancer cells evade the immune system, and for developing new diagnostic and therapeutic methods," says senior author John VandeBerg, PhD, chief scientific officer at the Southwest Foundation for Biomedical Research (SFBR) in San Antonio.

The new animal model, the newborn opossum, represents an advance over other animals, such as the mouse that has a different immune system from humans and in which cancers do not spread in the same way. The new model is described in a paper appearing in the February issue of the International Journal of Clinical and Experimental Pathology. The research was supported by a grant from The Robert J. Kleberg, Jr. and Helen C. Kleberg Foundation.

In the study, researchers injected human melanoma, colon cancer and prostate cancer cells into newborn opossums. The resulting tumors grew, invaded, spread and eventually regressed. Further studies found that as early as 11 days following injections with colon cancer cells, tumors grew and spread, and induced immune responses. The pattern showed how the cancerous cell first escapes the normal regulatory mechanisms by not appearing to be foreign to the immune system, and later is distinguished from normal cells, thus making the model capable of predicting activity in humans.

When developed, a test might allow physicians to assess the effect of a wide variety of treatments, including chemotherapy, gene therapy, and immunotherapy, for virtually all cancers. Typically, patients are administered several drugs which may appear to be effective but eventually decrease in efficacy. With a new testing tool, physicians might be able to gauge the efficacy of both standard and experimental cancer treatments before giving them to patients by injecting a patient's cancer cells into several groups of newborn opossums and comparing the efficacy of different treatments among groups. VandeBerg emphasizes that such a test might take 10 years to develop.

Collaborators on the study included Zhiqiang Wang, MD, PhD, of Methodist Hospital in Houston, Gene Hubbard, DVM, MS, of SFBR, and Fred Clubb Jr., DVM, PhD, of the Texas Heart Institute in Houston. Wang conducted most of the work on this project as a staff scientist in VandeBerg's laboratory before moving to Houston.

SFBR is one of the world's leading independent biomedical research institutions dedicated to advancing health worldwide through innovative biomedical research. Located on a 332-acre campus on the northwest side of San Antonio, Texas, SFBR partners with hundreds of researchers and institutions around the world, targeting advances in the fight against cardiovascular disease, diabetes, obesity, cancer, psychiatric disorders, problems of pregnancy, AIDS, hepatitis, malaria, parasitic infections and a host of other infectious diseases. For more on SFBR, go to .