Messana, Joseph M., Rocher, Leslie L., Ellis, Charles N., Fradin, Mark S., VanGurp, John R., Cantu-Gonzalez, Graciella, Parish, Thomas G., Wheeler, Suzanne M., and Voorhees, John J.
The effects of cyclosporine on the immune system are discussed. This immunosuppressive drug is thought to work by inhibiting the proliferation of some types of T cells (a cell type of the immune system), while leaving the proliferation of other types unaffected. Conventional immunosuppressive drugs kill T cells that are proliferating, an action that can lead to permanent depletion of immunological memory. Cyclosporine, though, does not kill these cells (although it limits their rate of proliferation), and the patient's immunologic repertoire returns to normal if the drug is stopped. Immunosuppressive drugs are associated with an increased risk of cancer, perhaps because they activate latent oncogenic viruses (viruses that promote malignant change) or because they inhibit immunologic responses that arrest tumor growth. The experimental evidence for these hypotheses is reviewed. The effects of cyclosporine on cancer risk have been difficult to evaluate, since the drug has been most often given to transplant patients. Such patients receive so many immunosuppressive agents that the effects of any one drug cannot be determined. However, some studies implicate cyclosporine in elevating the risk for certain malignancies in these patients. When taken by patients with certain skin disorders (skin cancer, psoriasis), the drug appears to promote tumor development in cases of prior exposure to carcinogens. A discussion is presented of the effects on the immune system when cyclosporine is used to treat psoriasis, an increasingly common use of the drug. Whether cyclosporine will become the drug of choice for that disease depends on results from long-term studies that can assess the cancer risk. (Consumer Summary produced by Reliance Medical Information, Inc.)