Ovarian tumor cells grown in microgravity conditions in NASA's rotating wall vessel are three-dimensional, more like the tumors found in cancer patients. The multicellular clusters reach diameters of 0.4 centimeters. Photo: University of South Florida Health Sciences Center

When the space shuttle Discovery blasts off on its next mission, it will take ovarian cancer into space for the first time.

Part of a joint project between University of South Florida College of Medicine and the National Aeronautics and Space Administration, the ovarian cancer cells are headed to the International Space Station to grow for two weeks in a near-gravity-free environment. The goal is to develop three- dimensional cancer cell clusters that function more like cancer in humans than the two-dimensional cell cultures traditionally grown in petri dishes.

For the last nine years, USF cell biologist Jeanne Becker, PhD, has used NASA technology to grow human ovarian cancer cells in a chamber simulating low gravity at her Tampa General Hospital laboratory. The breakthrough 3-D model allows her to study how the tumor cells grow and differentiate, and, more recently, to test the effectiveness of antihormonal therapies in combating ovarian cancer.

Now Dr. Becker will have the chance to see the effect of the true near-zero gravity of space on the study of ovarian cancer growth.

"I believe," Dr. Becker said, "that space-based technology offers an incredibly exciting and extremely unique approach to understanding the biology of this devastating women's disease."

In addition to the ovarian cancer cell line provided by Dr. Becker, experiments with kidney epithelial cells, colon cancer cells and neuroendocrine cells, supplied by three other investigators, will be conducted in space. This will be the first set of cell culture studies to be performed aboard the International Space Station.

Once the ovarian cancer tissue is preserved and flown back to earth, the experimental results will be analyzed by Dr. Becker in her lab at Tampa General and by NASA researchers at the Johnson Space Center in Houston. Scientists hope the new knowledge will help them define mechanisms in tumor cell development that can be targeted for treatment in patients with ovarian cancer -- a disease typically not detected until reaching advanced, often incurable stages.

In 1992, Dr. Becker was one of a dozen researchers to begin studies using a revolutionary tissue culture chamber designed at NASA's Johnson Space Center. The chamber, known commercially as the rotating wall vessel (RWV) bioreactor, is used today by more than 120 scientists across the country in NASA-sponsored projects.

The RWV was developed to grow cells with minimal influence of the earth's gravity so that cells could be transported into space without being subjected to destructive forces during launch and landing. This low gravity, or microgravity, environment produces three-dimensional tumors that look and behave more like tumors found inside the body than the flat, two-dimensional layers of tumor cells grown in petri dishes and flasks.

Dr. Becker uses the RWV to create three-dimensional tissue models for ovarian and breast tumors -- two cancers extremely difficult to grow outside the human body. She not only wants to better understand how tumors develop, but also to discover ways genes might be altered to kill the cancers. She is also measuring tumor sensitivity to chemotherapy and antihormonal therapy.

The response of cells to a drug can be changed dramatically by the way those cells are grown. Tumor cells grown three dimensionally in the RWV are more drug resistant than when grown on a flat surface. For example, the same dose of anti-cancer agent taxol that kills ovarian cancer cells grown in a plastic dish will not kill all the cancerous cells in the more complex 3-D model. "The remaining cells continue to grow, mirroring what happens in patients who fail chemotherapy," Dr. Becker said.

The challenge is finding ways to overcome persistent drug resistance -- the main problem of chemotherapy. "Ultimately," Dr. Becker said, "I'd like to use 3-D models for ovarian and breast cancer to more reliably test new drugs and hormone therapies before they are administered to patients. It could give physicians a better first shot at predicting which treatments will work."

In space researchers can grow larger, more advanced 3-D cell masses and actually determine whether there is a difference in cell function between microgravity on earth and the real thing. "We eventually need to apply what we learn from microgravity studies at the cellular level to animals and humans," Dr. Becker said. "This can only be accomplished by scientists on long space missions.