Patients with tumors that contain increased numbers of T lymphocytes generally survive longer than those with tumors without T-cell involvement, suggesting that T cells with potent antitumor function naturally exist in cancer and control tumor progression. With the exception of melanoma, it has been difficult to identify and isolate the tumor-reactive T cells from common cancers, however, the ability to do so could be used to fight a patient's own cancer.
In a paper recently published in Clinical Cancer Research, investigators in the lab of Daniel Powell, PhD, at the Perelman School of Medicine, University of Pennsylvania, demonstrated for the first time that a T cell activation molecule can be used as a biomarker to identify rare antitumor T cells in human cancers. The molecule, CD137, is a protein that is not normally found on the surface of resting T cells but its expression is induced when the T cell is activated.
In their work, Powell and colleagues developed a rapid system to accurately isolate these cells directly from human tumor tissue. TILs, short for tumor-infiltrating lymphocytes - are white blood cells that have left the bloodstream and migrated into tumor tissue. They took human tumor samples that contained TILs, disrupted them to single cell suspensions, and cultured the mix of tumor cells and TILs overnight. The next morning they selectively captured the TILs that expressed the CD137 molecule.
In a test tube-based experiment, the team showed that the isolated CD137 T cells recognize cancers cells taken from the same patient. The T cells recognize proteins (called antigens, immunologically) presented by the tumor cells as small peptides derived from inside the cell.