The potential use of the microgravity environment for inroads in cancer research is both important and promising. Research opportunities are broad and will include many areas of examination for investigators who are trained in both basic and clinical sciences. As one example, studies have shown that mammalian cell culture conducted in a manner that does not allow cell settling as a result of gravitational forces holds promise in the propagation of three-dimensional tissue cellular arrays much like those that normally comprise tissue specimens in the intact body. The space shuttle and the International Space Station have only a minute fraction of the gravitational force present on Earth. Culture of tissues with a three-dimensional architecture on these research platforms provides a unique and powerful opportunity for studies of anti-cancer drug action with a more complex and natural tissue ultrastructure than can be attained in terrestrial laboratories.
Even the production and analysis of new anticancer drugs may be conducted in a superior manner in microgravity. Studies already conducted on the space shuttle have shown that, in at least some instances, superior crystal growth can be achieved in microgravity when compared to crystals grown on Earth. This success primarily is the result of a lack of liquid convection currents in microgravity that subsequently leads to a quieter liquid environment for a gradual and more orderly growth of crystals. The quality of crystal products is an important feature in the determination of the three-dimensional structure of the molecules by X-ray diffraction analysis . Until the three-dimensional structure of new and existing anti-cancer compounds is established, the design of superior candidates for cancer treatment is severely hampered.
It is generally recognized that cancers arise in the body more often than clinically troublesome cancer diseases occur. In many cases the primary cancer growth is restricted in further development and the victim's immune system plays an important role in limiting cancer progression, sometimes even eradicating the cancer cells altogether. It seems that the mammalian immune system may not function as efficiently in the microgravity environment when compared to Earth.
On one hand, a weakened immune response to infectious diseases and cancer could present a serious obstacle for space travelers of the future. On the other hand, a compromised immune system in microgravity, and a subsequent increased efficiency of tumor progression, may provide a valuable test bed for research on the immune system with regard to cancer development. The microgravity environment, where immune function is less efficient, may also provide an excellent opportunity to develop and assess new chemotherapeutic measures that can strengthen the host's immune response. Of course, there are biomedical applications well beyond cancer research since the progression of many diseases may reflect a compromised immune function.
The life-threatening radiation exposure away from the protective atmosphere of Earth, and the ensuing increase in cancer cell development, is more than a casual concern for long-distance space travel. The means to protect space travelers from increased radiation will be necessary before such adventures are common.*
see also Aids Research (volume 1); Living in Space (volume 3); Made in Space (volume 1); Medicine (volume 3); Microgravity (volume 2).
Terry C. Johnson
Curtis, Anthony R., ed. Space Almanac, 2nd ed. Houston: Gulf Publishing Company,1992.
Mullane, R. Mike. Do Your Eyes Pop In Space? And 500 Other Surprising Questions About Space Travel. New York: John Wiley & Sons, 1997.
*In 2002 NASA announced an expanded 10-year program to study space radiation issues.