A grade of compounds that has been known to provide pain relief and reduce the inflammation of arthritis can be helpful in the prevention and treatment of skin, bladder and colon cancer, according to researchers at the National Cancer Institute (NCI).
The potential cancer-fighting attributes of a new class of drugs called “COX-2 inhibitors” (COX-2 stands for the enzyme cyclooxygenase-2) was discussed in the July 21 issue of the “Journal of the National Cancer Institute” (JNCI). The COX-2 inhibitors are able to restrain the development of tumors in animal tests, giving hope that they may soon become another weapon in the struggle against cancer.
Researchers first began their studies when elevated levels of the enzyme, COX-2, were found in tumors. Experiments were then designed to see if reducing the levels of this enzyme would reduce the size of such tumors. It was known that commonly used anti-arthritis drugs and pain relievers, such as aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs), actually did lower levels of COX-2. Therefore, scientists used NSAIDs in trials to evaluate the possible anti-tumor effect of lowering COX-2 levels.
Many trials are under way in order to evaluate the cancer-fighting potential of COX-2 inhibitors. Among them is one led by Dr. Raymond DuBois. Dr. DuBois is the principal investigator of the first program to receive a grant from the NCI in support of research studying the effect of drugs intended to prevent, rather than to treat, cancer. This concept is embodied in the term “chemoprevention.” Dr. DuBois commented on recent trials of his program, “The use of COX-2 inhibitors for chemoprevention in humans is still in the experimental stages, but results have been encouraging.”
Blocking this enzyme interferes with production of fatty acids (prostaglandins) that are widely distributed in the body. In trials involving the COX-2 inhibitors, researchers monitor the amount of this enzyme, as well as other markers indicative of the presence of a tumor. Participants in the studies include those who have had tumors removed as well as those who are carriers of certain genetic defects responsible for specific cancers.
Since these recent developments, the producers of the two leading COX-2 inhibitor drugs, rofecoxib and celecoxib, (Searle and Merck & Co., respectively) have begun preparations to expand the testing of the drugs into cancer-related research. While long-term use of NSAIDs sometimes comes at the price of ulcers and other gastrointestinal problems, COX-2 inhibitors are promising because studies have shown that they are less likely to cause these serious adverse health effects.
Past research seems to suggest that after years of therapy with COX-2 inhibitors, reduction of tumor recurrence is possible, but there still remains the question of primary prevention. Also, still to be explored is the question of whether the inhibitor drugs would be used for any tumor that is found to have high levels of the enzyme COX-2, or only a specific class of tumors. We must keep in mind Dr. DuBois? cautious optimism in expectations of what future studies will reveal. He notes that “Without more data, it is too early to recommend the use of COX-2 inhibitors as a treatment to fight cancer.”
What is apparent is that we have come to the beginning of a new era in the fight against cancer. Up until now, medicine has only been able to offer slow gains in cancer death rates, due to gradually improving surgical techniques, and more effective chemotherapy. But with the new data on COX-2 inhibitors and the more extensive results from breast cancer trials using tamoxifen, the era of chemoprevention of cancer may be close at hand.