Interferons

Encyclopedia of Cancer by Sally C. McFarlane-Parrott

Definition

Interferons are small, natural or synthetic protein and glycoprotein cytokines that are produced by leucocytes, T-lymphocytes, and fibroblasts in response to infection and other biological stimuli. In cancer treatment, they are used as immunotherapy against the proliferation of cancer cells.

Purpose

The goal of interferon use is to activate tumor-specific cytotoxic T-lymphocytes. T-lymphocytes are cells of the immune system that destroy foreign cells. Thus, tumor cells would be destroyed based on immunotherapy.

Description

Interferons attach to special receptors on the surface of cell membranes. They have a variety of functions, including enhancing or inhibiting enzymes, decreasing cell proliferation, or enhancing the activity of macrophages and T-lymphocytes. There are several different classes of interferons, including alpha, beta, gamma, tau, and omega. The classes can be further broken into subclasses and classified using Arabic numerals and letters. Cancer therapy research primarily focuses on alpha interferons.

In 1957 researchers discovered that the immune system produced a substance in response to a viral infection that acted as an anti-viral agent. They called that substance "interferon." Since then, recombinant DNA technology has provided a larger supply of interferons and has allowed extensive research regarding interferon's therapeutic properties against cancer.

Alpha interferons are used to treat cancers such as hairy cell leukemia, malignant melanoma, and Kaposi's sarcoma (an AIDS-related cancer). Off the label, alpha interferons are used to treat many other cancers including bladder cancer, chronic myelocytic leukemia, kidney cancer, carcinoid tumors, non-Hodgkin's lymphoma, ovarian cancer, and skin cancers. Alpha interferons can be combined with other chemotherapeutic drugs such as doxorubicin.

In the United States alpha interferons are sold under the brand names Roferon-A (Interferon Alfa-2a, recombinant) and Intron A (Interferon Alfa-2b, recombinant). There are no generic forms of these drugs.

Recommended dosage

Alpha interferons are only available by prescription and are given parenterally. A physician will determine dosage based on several factors such as what type of cancer is being treated, the patient's weight, and what other types of medications the patient is taking. Therefore, the dose will vary from patient to patient.

Patients can inject this drug themselves. Their physician may recommend that they drink extra water to avoid low blood pressure while on this medication. Since this drug can have flu-like side effects, it is recommended that patients inject the drug prior to bedtime so that they are sleeping during the worst part of the side effects.

Precautions

Alpha interferons have not been shown to cause problems in the fetus of pregnant women. Because it is not known whether this drug can cross over into breast milk, it is not recommended for use in women who are breast-feeding. Before this drug is given, patients should notify their doctors if they are allergic to immunoglobulins or egg whites.

There are several medical conditions that should be considered prior to deciding whether to use alpha interferons. There can be an increase in the following disorders: bleeding problems, mental problems, convulsions, diabetes mellitus, heart attack, heart disease, liver disease, kidney disease, and lung disease. People with an overactive immune system could also have this disorder exacerbated when using alpha interferons.

Caution should be taken when using alpha interferons because they can depress the number of white blood cells. This can make patients more susceptible to infection. Therefore, they should avoid contact with others who have infections and should contact their physician immediately if they think they are developing an infection. Patients should take care not to cut themselves, should not touch their eyes or inside of their nose with unwashed hands, and should take care when brushing their teeth so as not to cause bleeding.

The effects of alcohol can be exaggerated while taking alpha interferons. Alcohol should only be used by permission from a physician.

Side effects

Alpha interferons can have side effects that range from minor and irritating to major and severe, needing immediate attention. Some of the less serious side effects are muscle aches, unusual metallic taste in the mouth, fever and chills, and general flu-like symptoms such as headache, loss of appetite (anorexia), nausea and vomiting, and fatigue. To reduce the flu-like symptoms physicians may suggest that the patient take acetaminophen (e.g., Tylenol) before each dosage.

Other side effects may need medical attention. Any changes with the central nervous system such as confusion, trouble thinking and focusing, mental depression, nervousness, or numbness or tingling of fingers, toes and face require immediate medical attention.

The side effects are dependent on the dose. As a result, the physician may modify the dose if the side effects are severe.