Mesothelioma and the Immune System

The presence of an immune cell is associated with better prognosis for patients undergoing extrapleural pneumonectomy for malignant pleural mesothelioma is the conclusion of a recent article published in the Journal of Thoracic Cardiovascular Surgery.1

Canadian researchers tested mesothelioma samples removed from 32 patients (28 men and 4 women). The patients ranged in age from 21 to 74 (median age was 59). The researchers were looking for the numbers of specific types of immune cells. They then compared this data to the survival of the patients to see if these cell counts had any relationship with survival. They found that one specific type of immune cell called CD8+ was associated with better prognosis. The study found that higher levels of CD8+ cells coorelated with good clinical outcome after induction chemotherapy followed by EPP, better overall survival and progression-free survival, and lower incidence of mediastinal lymph node metastases.

What are CD8+ cells ?

CD8+ cells are a type of cell-killing T-lymphocyte that can search out and kill specific types of virus-infected and cancer cells. When these cells find their target cells they induce the target cells to secrete proteins that attract nearby macrophages (a type of white blood cells). These macrophages then surround and destroy the infected cells.

Can Natural Approaches Increase CD8+ Counts?

This study lends further support to the theory that malignant pleural mesothelioma may be sensitive to immune-based therapies. In fact, several immune-based clinical trials using interferon or interleukin have reported improvements in the median survival times seen with purely conventional therapies (like chemo and surgery alone). But, if mesothelioma has an immunogenic component, it would suggest that natural approaches that affect immune response may also benefit the patient.

CD8+ Cells and the Immune System

There have been studies that have looked at the impact of various natural products like vitamins, mushrooms, and tea on CD8+ cell counts. For example:

• Substances isolated from the medicinal mushroom Agaricus blazei were tested on mice with lung cancer. One of the substances increased the numbers of CD8+ invading the tumors.2

• In a Harvard Study, pregnant women with HIV were given vitamin A (preformed vitamin A and beta carotene) and multivitamins (vitamins B, C, and E). The vitamin administration led to fewer deaths and also resulted in significantly higher CD4+ and CD8+ cell counts and significantly lower viral loads.3

• In another study mice were fed extracts from Green Tea (green tea polyphenols or GTP’s), exposed to ultra violet radiation and then compared to mice that were also radiated but did not receive GTP’s. The researchers found that administration of GTP’s reduced skin tumor incidence by 35%, reduced tumor multiplicity by 63%, and reduced tumor growth by 55%. The researchers also found that the GTP mice demonstrated a number of biological differences from the other mice including more cytotoxic CD8+ cells in their tumors.4

No Clinical Studies at Present

Unfortunately, there have been no clinical studies in which mesothelioma patients were administered immune boosting natural products like medicinal mushrooms, vitamins, or herbs to determine their potential impact on survival or quality of life. The current paradigm of using cytotoxic (cell killing therapies) and the monetary incentive to create easily patentable drugs are two disincentives to engage in such a study. (It is easy to understand why a drug company would not invest the estimated $500 million to bring a new treatment to market when the treatment is a natural product and can be purchased in a vitamin store or grown in one’s backyard for a few dollars.) Nonetheless, emerging science does suggest that the immune system can recognize and eliminate malignant tumors and that certain natural products can have a dramatic effect on immune competence. These two critical revelations may ultimately provide the intellectual rationale for the National Cancer Institute to use some of their $5 billion budget to sponsor clinical studies to determine if natural products are of value to mesothelioma patients in either prolonging or improving their quality of life.