Coenzyme Q10
Laboratory work on coenzyme Q10 has focused primarily on its structure and its function in cell respiration. Studies in animals have demonstrated that coenzyme Q10 is capable of stimulating the immune system, with treated animals showing increased resistance to protozoal infections [1,2] and to viral and chemically induced neoplasia.[1-3] Reviewed in [4] Early studies of coenzyme Q10 showed increased hematopoiesis (the formation of new blood cells) in monkeys, Reviewed in [4,5] rabbits,[6] and poultry. Reviewed in [5] Coenzyme Q10 demonstrated a protective effect on the heart muscle of mice, rats, and rabbits given the anthracycline anticancer drug doxorubicin.[7-12] Although another study confirmed this protective effect with intraperitoneal administration of doxorubicin in mice, it failed to demonstrate a protective effect when the anthracycline was given intravenously, which is the route of administration in humans.[13] Researchers in one study sounded a cautionary note when they found that coadministration of coenzyme Q10 and radiation therapy decreased the effectiveness of the radiotherapy.[14] In this study, mice inoculated with human small cell lung cancer cells (a xenograft study), and then given coenzyme Q10 and single-dose radiation therapy, showed substantially less inhibition of tumor growth than mice in the control group that were treated with radiation therapy alone. Since radiation leads to the production of free radicals, and since antioxidants protect against free radical damage, the effect in this study might be explained by coenzyme Q10 acting as an antioxidant. As noted previously (General Information), there is some evidence from laboratory and animal studies that analogs of coenzyme Q10 may have direct anticancer activity.[15,16] References
The use of coenzyme Q10 as a treatment for cancer in humans has been investigated in only a limited manner. With the exception of a single randomized trial,[1] which involved 20 patients and tested the ability of coenzyme Q10 to reduce the cardiotoxicity caused by anthracycline drugs, the studies that have been published consist of anecdotal reports, case reports, case series, and uncontrolled clinical studies.[2-7] Reviewed in [8-11] In view of the promising results from animal studies, coenzyme Q10 was tested as a protective agent against the cardiac toxicity observed in cancer patients treated with the anthracycline drug doxorubicin. It has been postulated that doxorubicin interferes with energy-generating biochemical reactions that involve coenzyme Q10 in heart muscle mitochondria and that this interference can be overcome by coenzyme Q10 supplementation.[3,12,13] Studies with adults and children, including the aforementioned randomized trial, have confirmed the decrease in cardiac toxicity observed in animal studies.[1-4] The potential of coenzyme Q10 as an adjuvant therapy for cancer has also been explored. In view of observations that blood levels of coenzyme Q10 are frequently reduced in cancer patients,[14,15] Reviewed in [7,9,10] supplementation with this compound has been tested in patients undergoing conventional treatment. An open-label (nonblinded), uncontrolled clinical study in Denmark followed 32 breast cancer patients for 18 months.[5] The disease in these patients had spread to the axillary lymph nodes, and an unreported number had distant metastases. The patients received antioxidant supplementation (vitamin C, vitamin E, and beta carotene), other vitamins and trace minerals, essential fatty acids, and coenzyme Q10 (at a dose of 90 mg/day), in addition to standard therapy (surgery, radiation therapy, and chemotherapy, with or without tamoxifen). The patients were seen every 3 months to monitor disease status (progressive disease or recurrence), and, if there was a suspicion of recurrence, mammography, bone scan, x-ray, or biopsy was performed. The survival rate for the study period was 100% (4 deaths were expected). Six patients were reported to show some evidence of remission; however, incomplete clinical data were provided, and information suggestive of remission was presented for only 3 of the 6 patients. None of the 6 patients had evidence of further metastases. For all 32 patients, decreased use of painkillers, improved quality of life, and an absence of weight loss were reported. Whether painkiller use and quality of life were measured objectively (e.g., from pharmacy records and validated questionnaires, respectively) or subjectively (from patient self-reports) was not specified. In a follow-up study, 1 of the 6 patients with a reported remission and a new patient were treated for several months with higher doses of coenzyme Q10 (390 and 300 mg/day, respectively).[6] Surgical removal of the primary breast tumor in both patients had been incomplete. After 3 to 4 months of high-level coenzyme Q10 supplementation, both patients appeared to experience complete regression of their residual breast tumors (assessed by clinical examination and mammography). It should be noted that a different patient identifier was used in the follow-up study for the patient who had participated in the original study. Therefore, it is impossible to determine which of the 6 patients with a reported remission took part in the follow-up study. In the follow-up study report, the researchers noted that all 32 patients from the original study remained alive at 24 months of observation, whereas 6 deaths had been expected.[6] In another report by the same investigators, 3 breast cancer patients were followed for a total of 3 to 5 years on high-dose coenzyme Q10 (390 mg/day).[7] One patient had complete remission of liver metastases (determined by clinical examination and ultrasonography), another had remission of a tumor that had spread to the chest wall (determined by clinical examination and chest x-ray), and the third patient had no microscopic evidence of remaining tumor after a mastectomy (determined by biopsy of the tumor bed). All 3 of the above-mentioned human studies [5-7] had important design flaws that could have influenced their outcome. Study weaknesses include the absence of a control group (i.e., all patients received coenzyme Q10), possible selection bias in the follow-up investigations, and multiple confounding variables (i.e., the patients received a variety of supplements in addition to coenzyme Q10, and they received standard therapy either during or immediately before supplementation with coenzyme Q10). Thus, it is impossible to determine whether any of the beneficial results was directly related to coenzyme Q10 therapy. Anecdotal reports of coenzyme Q10 lengthening the survival of patients with pancreatic, lung, rectal, laryngeal, colon, and prostate cancers also exist in the peer-reviewed, scientific literature.[4] The patients described in these reports also received therapies other than coenzyme Q10, including chemotherapy, radiation therapy, and surgery.
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