'Helper' white blood cells trigger cancer-killing immune response
US scientists have discovered that a specific form of a white blood cell, called a T helper cell, can set off a chain of events that produce custom-made immune cells designed to destroy cancer cells.
Th17 cells are one of four known types of T helper cell, which play a vital role in the body's immune response by stimulating the production of "killer" T cells.
"Killer" T cells are responsible for actively destroying bacteria and other invaders.
According to new research from scientists at the University of Texas MD Anderson Cancer Centre, Th17 cells can alert the body to the presence of cancer cells and initiate an attack on these cells by custom-made "killer" T cells.
The team, whose findings are published in the journal Immunity, found that Th17 cells were capable of recognising metastatic melanoma tumours in the lungs of mice.
It is hoped that understanding more about how this specific type of T helper cell works may lead to new ways of treating or preventing cancer.
The team's previous studies had shown that Th17 cells secrete a protein called interleukin-17 (IL-17), too much of which can promote autoimmune and inflammatory diseases.
They had also found Th17 cells inside tumours in several different types of cancer, and set out to determine exactly what it was doing.
In order to test this, they used mice which lacked the ability to produce IL-17, and first injected them with a form of melanoma that tends to grow in the lungs.
The cancers in these mice were more aggressive than those in normal mice.
They then gave a new set of mice both Th17 cells that had been exposed to melanoma, and melanoma cells.
After 16 days, mice with Th17 had very low levels of cancer growth, while the normal mice - which had not been injected with Th17 cells - showed high levels of tumour growth in their lungs.
Finally, a third experiment revealed that mice which already had melanoma in their lungs and were subsequently injected with Th17 cells typically benefited from a 75 per cent reduction in tumour size compared with control mice, showing that the T helper cells may have the capacity to treat existing cancer.
Study author Professor Chen Dong, from MD Anderson Cancer Centre's department of immunology, commented: "While there is much work to be done, these preclinical findings imply the possibility of taking a patient's Th17 cells, expanding them in the lab and then re-infusing them as treatment."
Dr Caetano Reis e Sousa, head of Cancer Research UK's Immunobiology lab at its London Research Institute, said: "These scientists have made progress in showing that Th17 cells could, in principle, be used to boost the immune response to cancer.
"Although exciting, this research is at an early stage, so we can't predict the long-term effect of using these cells in cancer treatment. The results need to be validated and extended before scientists know if a treatment based on this approach could one day be used to help cancer patients."
Martin-Orozco, N., Muranski, P., Chung, Y., Yang, X., Yamazaki, T., Lu, S., Hwu, P., Restifo, N., Overwijk, W., & Dong, C. (2009). T Helper 17 Cells Promote Cytotoxic T Cell Activation in Tumor Immunity Immunity DOI: 10.1016/j.immuni.2009.09.014