Researchers at Hopkins and Harvard have found that men using the cardiac drug digoxin had a 24 percent lower risk of developing prostate cancer. The group believes further studies may lead its use in treatment of the disease, which is the second largest cause of cancer-related deaths in U.S. men.
Made from the foxglove plant, digoxin has been used for hundreds of years in folk medicine and as a treatment for congestive heart failure and heart rhythm abnormalities. According to the scientists, digoxin was also a leading candidate among the 3,000 drugs they screened for their ability to restrict prostate cancer growth.
In the initial stages of the project, Hopkins researchers screened approximately 38 compounds that have proven effective in reducing prostate tumors in laboratory conditions, and have also been approved by the FDA for other uses. Although not as effective as other compounds, digoxin was ultimately chosen by the group for its widespread use, thus making it suitable for an epidemiological study. The study was published last month in Cancer Discovery.
With 47,000 male subjects involved in the study, researchers found that those who took digoxin for heart disease had a significantly lower risk of developing prostate cancer. However, the findings have not yet proven that digoxin definitely prevents prostate cancer and do not support the use of the drug in a such a manner. Addtionally, its serious side effects, including heart rythem irregularity and nausea-related symptoms, have been found among patients who have been prescribed digoxin for heart problems.
The scientists set about trying to find a link between digoxin and prostate cancer in men. Subjects who were included in this study ranged in age from 40 to 75 and participated in Harvard’s Health Professionals Follow-up Study between 1986 and 2006. None of these subjects were diagnosed with cancer prior to the start of the study. The researchers examined the medical records and pathology reports of subjects who reported prostate cancer diagnosis.
The study’s participants reported 5,002 cases of prostate cancer. Two percent of all participants reported regular use of digoxin at the beginning of the study. Those who did had a 24 percent lower risk of getting prostate cancer compared with men who did not use the drug. Those who used digoxin for more than 10 years had about 50 percent the risk of developing prostate cancer of those who did not.
Researchers ruled out factors such as Prostate-Specific Antigen (PSA) screening, family history of prostate cancer and the use of other heart drugs, but the lower risk of prostate cancer among digoxin users was still significant.
The exact mechanism by which digoxin affects prostate cancer cells is yet to be determined. In heart cells (myocytes), digoxin decreases the sodium concentration gradient and the resulting outflow of calcium, thereby increasing calcium concentration in myocardiocytes and pacemaker cells. The researchers believe it may have an effect on the same or different sodium and potassium pathways in prostate cancer cells.
