Tamoxifen, a medication that blocks the effects of estrogen, worked to prevent the growth of malignant pleural mesothelioma cells cultured in the lab, and to improve the cells’ sensitivity to chemotherapy.
Interestingly, the study, “Tamoxifen Suppresses the Growth of Malignant Pleural Mesothelioma Cells,” published in the journal Anticancer Research, demonstrated that the effects of the drugs were not caused by blocking the estrogen receptor.
Recent studies have shown that estrogen receptor modulators can help to suppress mesothelioma tumors, leading researchers at the Beaumont Hospital in Ireland to investigate whether tamoxifen could also improve the effectiveness of chemotherapy in mesothelioma.
Tamoxifen, sold in the U.S. as Nolvadex or Soltamox, is commonly used to treat, or sometimes prevent, breast cancer. It has complex effects on the estrogen receptor, and is referred to as an estrogen modulator.
Researchers treated four different mesothelioma cells types, grown in the lab, with tamoxifen, or with a sequential treatment of tamoxifen and Platinol (cisplatin) — a platinum chemotherapy commonly used to treat mesothelioma.
They noted that tamoxifen prevented the growth of the four cell types to varying degrees, and the drug combination also affected the tumor cells’ growth.
While the treatment helped to block the growth of cancer cells and improved their responsiveness to chemotherapy, further analysis revealed these effects were not linked to the estrogen receptor. The receptor was indeed present on the cancer cells, but blocking the receptors with another compound did not prevent tamoxifen from working, suggesting that its effects came through another mechanism.
To further examine the treatment’s molecular actions, the team focused on the cell types with the strongest response.
This analyses showed that tamoxifen prevented the production of molecules called cyclins by the tumor cells. Cyclins control the ability of cells to divide, and are found in high levels in many cancer types.
The loss of cyclin production prevented the cells from further multiplying, and initiated self-destruction molecular pathway signaling, known as apoptosis, to help kill the cells.
Although the results suggest a possible role of tamoxifen in treating mesothelioma, the researchers caution that its use in combination with platinum-based chemotherapy — which require cancer cells to divide rapidly — may be compromised, as this drug actually slows cancer cell division.