Stem Cells and Malignant Mesothelioma: An In-Depth Look

Malignant mesothelioma is a rare and aggressive cancer that kills as many as 2,500 people in the United States every year. Closely associated with long-term asbestos exposure, mesothelioma typically affects the lining in the lungs, heart, abdominal cavity or, in very rare cases, the testes. Mesothelioma has a long latency period of latency. This means people are seldom diagnosed until years after their initial asbestos exposure. Recent research has shown a connection between this devastating disease and stem cells—a connection worth examining more closely.

What are stem cells?

We hear about advances in stem cell research almost every time we turn on the evening news. It seems each day, new scientific discoveries are made in the realm of stem cell research. But what are stem cells? Stem cells are a cell type present in the human body that have the ability to become any bodily cell type. These unique cells are almost a blank template or the building blocks upon which all other cell types can be written.

Cancer stem cells

Cancer stem cells (sometimes referred to as “CSCs”) are a special type of stem cell found in some forms of cancer, including malignant mesothelioma. Like all stem cells, CSCs have the potential to become various other cell types. However, the types of cells CSCs can become is limited in a grim way. CSCs can become any type of tumor-specific cell in the human body. So, just as healthy stem cells from bone marrow can develop into healthy skin or muscle tissue, CSCs can become any cell types contained in a tumor.

The role of CSCs in relapse post-treatment

Recent results from Swiss researchers in the Division of General Thoracic Surgery at University Hospital Berne were published in the International Journal of Oncology. These findings suggest CSCs may play a role in recurrence of cancer after treatment. Some tumors thought to be completely eradicated with chemotherapy or surgery, often return after completion of treatment. Researchers believe this may be due to CSCs remaining in the body even after the tumor itself has been eliminated.

The other side of the coin: systemic stem cells as a treatment option?

Although CSCs can turn a remission upside down, research shows innovative stem cell treatment could be promising for cancer patients. For example, a recent study by British researchers at University College London indicates systemic treatment with stem cells programmed to cause apoptosis or cell death could be effective for eradicating mesothelioma tumors. By targeting and destroying the tumor cells, the stem cells can “clear up” the cancerous cells without causing damage to surrounding healthy cells.

Attacking Mesothelioma Stem Cells

With the stem cell theory of cancer in mind, some researchers are working to develop new treatments to specifically target the stem cells responsible for tumor growth. One drug that was developed to attack mesothelioma stem cells made it into clinical trials. Unfortunately the trial was halted because the drug did not seem to be working.

The drug, called defactinib, showed promising results in phase I clinical trials. However, phase II, which involved more participants, was not as successful. Patients tolerated the drug well, but efficacy was low in the 372 patients involved. Results for patients receiving the drug were no better than for patients receiving a placebo. The trial was stopped due to these disappointing results.

Because this one drug did not kill mesothelioma stem cells does mean the end of this line of research. More drugs are being developed and tested. In fact, defactinib may be tested again in combination with different chemotherapy drugs.

Mesenchymal Stem Cell Treatment

Another type of stem cell treatment under study for mesothelioma is called mesenchymal stem cell treatment. Mesenchymal stem cells are stem cells that were discovered in the stroma, which is connective tissue found throughout the body. These cells are able to differentiate into bone, cartilage, fat, and muscle cells. They also may have the ability to moderate the immune system, although exactly how they work is still not completely understood. Researchers are investigating how these stem cells could be used to treat a range of diseases.

At the Pacific Mesothelioma Center, researchers are using mesenchymal stem cells to develop new treatments for mesothelioma. These stem cells are being tested as vectors for delivering drugs to tumors and for use as supplements to immunotherapy treatments. Mesenchymal stem cells may be able to enhance the body’s immune system to help it target and kill cancer cells.

Implications for the future

Although recent research findings for therapeutic usage of systemically-delivered stem cells show promise, these findings are only preliminary. More research is necessary to determine the validity and efficacy of the initial findings.

However, if further trials prove successful, stem cell therapy could be a safe treatment option with fewer side effects and less recovery time than traditional treatment methods. These innovative treatment methods could prove more effective, increasing overall quality and length of life for patients.

Can I opt for stem cell treatment of my mesothelioma?

If you or someone you know has been diagnosed with malignant mesothelioma and is interested in exploring the possibilities of stem cell treatment, talk to your doctor about clinical trials.

While treatments offered by clinical trials are limited to those who qualify, you may be able to participate. There are several trials studying the effects of stem cell treatment for mesothelioma in human subjects. Speak with your physician to find out which studies may be right for you.