Table 2.
Evidence for immune surveillance against the development of cancer and for the control of existing cancer.
| Observation | Implication | Referencea |
|---|---|---|
| Immunodeficient animals and humans developing more cancers; immunosuppression causing an increase in cancer incidence | Control of cancer development by the immune system | (8, 40, 42, 123) |
| Increased risk for cancer in people with lower natural cytotoxic activity in their peripheral blood | Control of cancer development by the immune system | (57, 58) |
| A high percentage of occult cancers in autopsy studies | Control of cancer at the preclinical stage by the immune system (equilibrium) | (44–50) |
| Decades long time taken by pancreas cancer to become clinically overt | Control of cancer at the preclinical stage by the immune system | (53) |
| Control of occult cancer at the equilibrium phase by adaptive immune system | Control of cancer at the preclinical stage by the immune system | (124, 125) |
| Development of donor-derived malignancies that have been kept under control in immunosuppressed transplant recipients | Control of cancer at the preclinical stage by the immune system | (43) |
| More immunogenic tumors developing in more immunodeficient animals | Elimination of immunogenic tumors by immune competent hosts | (17, 124, 126) |
| Cancer patients with antibodies against antigens of their tumors (e.g., carcinoembryonic antigen, mucin 1) having a better clinical outcome and even spontaneous regression | Existent antitumor immunity exerting a favorable effect on the outcome | (27, 31, 127) |
| Successful chemopreventive agents (aspirin, metformin, tamoxifen, bisphosphonate) having immune enhancing effects | Contribution of the immune system to the preventive effects | (32, 66) |
| Successful cancer chemotherapeutic agents having immune modulatory effects favorable for anticancer immunity | Contribution of the immune system to the therapeutic effects | (27, 31, 32, 68) |
| The composition of tumor-infiltrating immune cells and indicators of immune system activity correlate with the clinical outcome | Existent antitumor immunity exerting a favorable effect on the outcome | (14, 16, 21, 27–32) |
aIn some instances, review papers rather than primary references are cited.