Dietary Vitamin D And Calcium Intake On Prostate Tumor Progression In Athymic Mice: High Calcium Intake Does Not Enhance Prostate Tumor Growth

The purpose of this study is to investigate the concern that increasing calcium and vitamin D intake may increase risk and progression of prostate cancer. Nu/nu male athymic mice were fed either 1) low (L) calcium (Ca) (0.02%) and vitamin D 3 (5,000 IU/kg) (+D), 2) normal (N) Ca (0.9%) + D, 3) a high (H) Ca (2%) + D, 4) NCa and no vitamin D, (‐D) or 5)H Ca ‐D. After one week, DU145 cells were injected subcutaneously in mice. Tumor growth rates were measured at the first appearance of tumor at day ~ 42 and followed for four weeks. Tumor growth rate for mice on a NCa ‐D diet was 627 ± 211% compared to mice on a NCa +D diet 184 ± 49% (P = 0.01). Tumors in mice on a HCa ‐D diet had as growth rate of 276 ± 93% while animals on a NCa +D diet had a growth rate of 298 ± 97%. For mice on a LCa +D diet, the tumor growth rate was 192 ± 59%. Serum Ca determinations revealed that mice fed a LCa +D or NCa +D diet had serum calciums of 10.5 ± 0.5 and 9.41 ± 0.5 mg/dl respectively (P= 0.32). Mice fed a NCa ‐D or HCa ‐D diet had serum calcium levels of 8.0 ± 0.4 and 8.0 ± 0.3 mg/dl respectively. (P= 0.44). Mice fed a LCa +D, NCa+D and HCa+D diet had 25(OH)D levels of 42.6 ± 3.4, 24.9 ± 3 and 24.9 ± 1.6 ng/ml respectively. Vitamin D deficiency promoted prostate tumor growth. Furthermore, a HCa ‐D diet limited tumor progression compared to the mice fed a NCa ‐D diet. This model may provide an insight into the role of dietary calcium and vitamin D in the progression of prostate cancer.