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DALLAS - April 1, 1999 - Investigators at UT Southwestern Medical Center at Dallas have developed a new way to isolate purified cancer cells - an important advance that will help unravel the mysteries of tumor biology and cancer development.

A major obstacle for studying the molecular changes characteristic of tumor cells is the presence of large numbers of nonmalignant cells within tumors. Current methods for isolation of purified tumor cells are cumbersome or permit limited numbers of assays.

Now a new simple method of preparing tissue samples, developed by a research team led by Dr. Adi Gazdar, UT Southwestern professor of pathology and associate director of the Nancy B. and Jake L. Hamon Center for Therapeutic Oncology Research, will aid molecular studies by permitting isolation of enriched purified epithelial cell populations that can be used for a wide range of molecular analyses.

The new method - Epithelial Aggregate Separation and Isolation (EASI) - is described in the April issue of Nature Medicine, and is applicable to almost all epithelial tumors, which constitute about 80 percent of human cancers.

"The new method is rapid and simple and can be used by any surgical pathology service to prepare samples for molecular profiling," said Gazdar, holder of the W. Ray Wallace Distinguished Chair in Molecular Oncology Research. "Once samples have been prepared, they can be sent to a specialized laboratory for cell isolation and nucleic acid extraction and analyses."

Tumors are structures consisting of mixtures of several cell types. In some tumors the cancerous cells constitute a minority of the total cell population. The EASI Prep, as the preparation of epithelial specimens by the EASI method is called, allows researchers to distinguish and isolate subpopulations of tumor samples and to investigate the sequence of the multiple stages of cancer development.

EASI combines the use of a simple, rapid and inexpensive method of sample preparation with laser capture microdissection (LCM), a recent technological development that enables pure cells to be isolated from specific microscopic regions of mixed cell populations. Previously the use of LCM required biopsied material to be chemically fixed by formalin and embedded in paraffin or frozen. But the use of fixed and embedded samples to obtain high-quality material for molecular analysis was unsatisfactory. The use of frozen samples has its own drawbacks of requiring more material and the complications of the freezing procedure.

The current methods of tumor-cell enrichment all have drawbacks compared to EASI. Most often they are cumbersome, lengthy and expensive and/or the quality of the isolated nucleic acids (DNA, RNA) or protein is not as high as that obtained by the EASI method.

"We hope that this method will facilitate molecular studies on tumors and their precursor lesions, and even on normal cells," Gazdar said. "Such studies will advance our knowledge of normal and tumor cell biology and should eventually benefit the patient."

Other UT Southwestern investigators contributing to this study were Dr. Anirban Maitra, staff associate; Dr. Ignacio Wistuba, assistant instructor; Dr. Arvind Virmani, instructor; research fellows Dr. Masahiro Sakaguchi, Dr. Inwon Park and Dr. Amy Stucky, all from the Hamon Center; Dr. Sara Milchgrub, associate professor of pathology; Dr. David Gibbons, assistant professor of pathology; and Dr. John Minna, director of both the W.A. "Tex" and Deborah Moncrief Jr. Center for Cancer Genetics and the Hamon Center. This research was funded by a National Cancer Institute Specialized Program of Research Excellence in Lung Cancer grant.


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