Unlocking The Mysteries Of Cancer And The Immune System

March 01, 2014


Peter A. Sieling, PhDIt may seem as if bacterial infections, such as pneumonia, would have little to do with melanoma or breast cancer. But Peter A. Sieling, PhD, a cellular immunologist, has spent his career making a connection between the two seemingly disparate fields. Now he appears to be in just the right place at the right time, as scientific evidence mounts suggesting the body’s own natural system for fighting infections may be the key to preventing or treating some types of cancers.

The role of the immune system is to recognize and eliminate challenges from harmful substances, like germs, and cancerous cells. “The immune system in relationship to cancer has similar but also different questions,” he says. “The types of cells in our body that fight against tumors – the immune cells – are almost identical to the cells that fight microbial infections.”

Dr. Sieling earned his PhD studying bacterial infections and went on to investigate how the immune system responds to bacterial infections, an area he has worked in for 20 years. During that time, something interesting was brewing in cancer research: the notion that the immune system plays an important role in the development of at least some types of cancer. He was intrigued with applying his expertise to cancer. For almost three years, he has been working in the field of tumor immunology at the John Wayne Cancer Institute. “I thought this was a wonderful place to apply all of these principles,” he says.

His work is performed at the Institute’s Dirks/Dougherty Laboratory for Cancer Research. “He has a vast expertise in immunology,” says his colleague, Delphine J. Lee, MD, PhD, director of translational immunology at the Institute. “He’s very focused. He’s a stable force. He has great integrity. I just like to work with good people, and he’s good in all ways: brilliant in his knowledge, brilliant in the technical aspects and an overall good person.”

Dr. Sieling’s projects include studies on Bacille Calmette-Guérin (BCG). In some melanoma patients, administering doses of BCG stimulates the immune system to fight the cancer.

“We don’t know all of the reasons why it works. But we are hypothesizing that it’s because the immune system recognizes mycobacteria,” he explains.

He hopes to elucidate how BCG works against melanoma in order to refine the therapy. For example, it may be possible to give patients components of some type of bacterium that fights melanoma while removing the dangerous or unnecessary parts of the microbe.

He is also exploring evidence that the immune response has a role in recognizing and eliminating breast cancer. Breast cancer is a disease with many sub-types. Studies are needed to identify which sub-types of breast cancer would respond best to immune system therapies.

Much of Dr. Sieling’s research explores the behavior of immune-system cells called lymphocytes. These cells – T cells, T helper cells and cytotoxic T cells – all have specific roles. One of his studies involves isolating cells in several areas: in the breast cancer tumor, near the tumor and far from the tumor. That information could explain how the various lymphocytes are functioning in relation to the cancer.

“We’re studying the mechanisms to try to understand them better because these therapies don’t work in 100% of cases,” he says. “The immune system is so complex. Some therapies may work in some patients but not others.”

Immunotherapies hold great promise because they target the molecular underpinnings of the cancer and would be unlikely to carry the kinds of side effects associated with less-targeted treatments, such as chemotherapy. One immune system therapy is already approved for melanoma – an immunomodulator called ipilimumab.

“We’re convinced in the case of melanoma that the immune system is vital to recognize and eliminate the tumors,” he says. “In some other cancers, the jury is still out. But it’s clear that the immune system functions to eliminate and prevent many types of cancer.”