WASHINGTON - Special, high-dose formulations of vitamin D and common, over-the-counter painkillers can greatly slow the growth of prostate cancer tumors, U.S. researchers reported Thursday.

Combining the two slowed their growth by up to 70 percent in a laboratory dish, the team at the Stanford University School of Medicine found.

Dr. David Feldman and colleagues are so impressed by the results that they have started a clinical trial to see if the approach also works in men.

Vitamin D--promotes differentiation, inhibits angiogenesis, regulates cell division
Current recommendations to avoid natural sunrays to thwart the possibility of deadly melanoma may be allowing other endangerments. For more than 50 years, medical literature has affirmed that regular sun exposure is associated with a substantial decrease in death rates from certain types of cancers. It is estimated that moderate sun exposure without sunscreen - enough to stimulate vitamin D production but not enough to damage the skin - could prevent 30,000 cancer deaths in the United States each year (Ainsleigh 1993). The most damaging of the sun's rays occur between the hours of 10 a.m. and 3 p.m. and are thus the hours demanding the greatest watchfulness.

Evidence points to a prostate, breast, and colon cancer belt in the United States, which lies in northern latitudes under more cloud cover than other regions (Studzinski et al. 1995). Certain regions in the United States, such as the San Joaquin Valley cities and Tucson, AZ; Phoenix, AZ; Albuquerque, NM; El Paso, TX; Miami, FL; Jacksonville, FL; Tampa, FL; and Orlando, FL; have a lower incidence of breast and bowel cancers. Conversely, New York; Chicago; Boston; Philadelphia; New Haven, CT; Pittsburgh; and Cleveland, OH; have the highest rates of breast and intestinal cancer of the 29 major cites in the United States. The greater hours of year-round sunlight correlate to a lower rate of breast and intestinal cancer in the U.S.A.

Vitamin D is formed in the skin of animals and humans by the action of shortwave UV light, the so-called fast-tanning sunrays. Precursors of vitamin D in the skin are converted into cholecalciferol, a weak form of vitamin D3, which is then transported to the liver and kidneys where enzymes convert it to 1,25-dihydroxycholecalciferol, the more potent form of vitamin D3 (Sardi 2000). Although vitamin D exists in two molecular forms, vitamin D3 (cholecalciferol) found in animal skin and vitamin D2 (ergocalciferol) found in yeast, vitamin D3 is believed to exhibit more potent cancer-inhibiting properties and is therefore the preferred form.

Dark-skinned people require more sun exposure to produce vitamin D because the thickness of the skin layer (the stratum corneum) affects the absorption of UV radiation. Black human skin is thicker than white skin and thus transmits only about 40% of the UV rays needed for vitamin D production. Darkly pigmented individuals who live in sunny equatorial climates experience a higher mortality rate from breast and prostate cancer when they move to geographic areas that are deprived of sunlight exposure in winter months (Angwafo 1998; Sardi 2000).

Cancer Adjuvant Therapy

Women with polymorphisms (genetic variations) of the vitamin D receptor gene may be less able to benefit from the nutrient. There is some evidence that vitamin D receptor gene polymorphisms play a role in the breast cancer (Bretherton-Watt et al. 2001); however, recent studies do not support this evidence (Buyru et al. 2003).
Identifying the at-risk groups, through the assessment of genetic variations in the vitamin D receptor, appears to be a forthcoming tool for planning intervention strategies.

Human leukemia cells cultured in the presence of vitamin D exhibited a reduced rate of tumor growth when injected into mice. Cells grown in vitamin D3 failed to form detectable tumors in 11 of 12 inoculated mice (Wang et al. 1997). The anticarcinogenic properties of vitamin D, confronts multiple stages of cancer development, including apoptosis, differentiation, angiogenesis, and metastasis, as well as regulating the cell growth cycle (van den Bemd et al. 2002).

Since vitamin D can cause calcium to be released from bones (a condition referred to as hypercalcemia), large doses of vitamin D cannot be used in patients whose medical history or genetics puts them at increased risk. Using a combination of Vitamin D3 and vanadium (a metallic element) enables vitamin D to retain its anticancer activity and vanadium addresses the problem of hypercalcemia (Basak et al. 2000).

Rats were supplemented with vanadium or vitamin D3 or both vanadium and D3 four weeks prior to induced liver cancer and continued thereafter until the 20th week. After 20 weeks of supplementation, the vitamin D3-vanadium combination had significantly reduced the number and size of abnormal hepatic nodules. The combination also showed an additive effect, reducing the number and size of hyperplastic nodes from 83.3% to 37.5%. In addition, vanadium effectively blocked the entry of calcium into cells.

A modified form of vitamin D (referred to as a deltanoid) delays the onset and reduces the number of skin cancers in laboratory mice. The microscopically altered structure of vitamin D produced a potentially effective cancer therapeutic. The vitamin D analog retains its anticancer profile but diminishes the threat of hypercalcemia. The most effective of four analogs tested was a doubly modified hybrid compound containing fluorine (Posner 2000).

During one study, mice painted with a chemical substance, inducing cancerous tumors were concurrently the animals were given the deltanoid. After 20 weeks, the fluorine-containing analog had reduced the incidence of tumors more than 28%, while the actual number fell 63% (Kensler et al. 2000). Deltanoids are in the early stages of development and, unfortunately, it may take 10 years before they become available (Guyton et al 2003). It is possible that deltanoids could lessen the need for hormone treatments or aggressive chemotherapy. Patients could theoretically stay on the treatment for the remainder of their life to keep the cancer from advancing.

Studies indicate that moderate or severe hypovitaminosis D was present in 66% of patients taking daily vitamin D in amounts less than the recommended dosage for their age. Adults may need a minimum of 5 times the 200-IU RDA, (or 1000 IU daily), to protect against cancer (Vieth 1999). Therapeutic dosages of vitamin D typically range from 800-4000 IU a day. Monthly kidney function blood tests (creatine, BUN, etc.) should be performed if daily vitamin D intake exceeds 1400 IU. These tests are included in most standard blood chemistry tests that cancer patients regularly perform to guard against anemia and overt immunosuppression.

Food sources of vitamin D include egg yolks, organ meats, fortified dairy products, butter, cod liver oil, and cold-water fish, such as salmon, herring, and mackerel. Vitamin D enhancers are vitamins A and C, calcium, magnesium, phosphorus, and choline. Antagonists are mineral oil, phenobarbital, and laxatives.