Viagra is best known as a treatment for erectile dysfunction, but scientists say the medicine may one day have another important role.
A new study suggests that sildenafil, the active ingredient in Viagra, may help slow the spread of cancer by reducing cancer cells’ access to cholesterol. The research was carried out at the Weizmann Institute of Science and published in Cancer Research.
Sildenafil was first developed to treat high blood pressure and chest pain caused by reduced blood flow to the heart.
During testing, researchers discovered that it improved blood flow to the penis, leading to its approval as a treatment for erectile dysfunction. Today it is one of the world’s best-known prescription medicines.
The new study focused on metastasis, the process in which cancer cells leave the original tumor and spread to other parts of the body.
Most cancer deaths are linked to metastasis rather than the original tumor, making it one of the biggest challenges in cancer treatment.
The researchers found that cancer cells need cholesterol to build healthy cell membranes and survive as they move through the body. Cholesterol also helps cells grow and divide, making it especially important for aggressive cancer cells.
The team discovered that sildenafil blocks an enzyme called PDE5. Blocking this enzyme increases the level of a signaling molecule called cGMP. The researchers found that cGMP also affects a protein that transports cholesterol inside cells, leaving less cholesterol available for cancer cells.
When cancer cells cannot obtain enough cholesterol, they appear to have greater difficulty spreading and forming new tumors in distant organs. This newly identified pathway was seen in laboratory experiments using cancer cells and animal models.
The scientists also explored combining sildenafil with statins, medicines commonly prescribed to lower cholesterol. Because statins reduce the body’s cholesterol production while sildenafil limits how cancer cells use cholesterol, the combination may produce a stronger anti-metastatic effect.
To strengthen their findings, the researchers analyzed information from nearly five million members of Israel’s Clalit Health Services collected over two decades. They found that cancer patients taking sildenafil, especially together with statins, appeared to have better survival than similar patients who did not.
The researchers stressed that these findings do not mean people should begin taking Viagra to treat cancer. The study included laboratory research, mouse experiments, and analysis of health records, but it did not include randomized clinical trials proving that sildenafil improves cancer outcomes.
This study is exciting because it identifies a completely new way that sildenafil may affect cancer biology.
The use of laboratory experiments together with large real-world health data makes the findings stronger, but observational data cannot prove cause and effect. Carefully designed clinical trials will now be needed before sildenafil can be recommended as part of standard cancer treatment.
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