Researchers from Roswell Park Cancer Institute conducted both in vitro (outside the body) and in vivo (inside the body) studies to determine the effects of calcitriol and the analogs, QW-1624-F2-2 and paricalcitol, on the prevention of prostate cancer.
Calcitriol is the active metabolite of vitamin D, and is used clinically to treat a variety of disorders, including recent clinical trials for established cancer. A major obstacle to clinical use of calcitriol is dose-limiting hypercalcemia (abnormally high concentration of calcium in the blood). QW, developed at Johns Hopkins University and paricalcitol (Zemplar) have been shown to reduce parathyroid hormone levels (which regulate the metabolism of calcium and phosphorus in the body).
The researchers then studied the effects of calcitriol and QW on the prevention of androgen-dependent prostate cancer in the transgenic adenocarcinoma of mouse prostate (TRAMP) model, which develops prostate cancer as the mice age. Both calcitriol and QW slowed the progression of prostate cancer in intact TRAMP mice after 14 weeks of treatment as indicated by decreased reproductive tract and prostate weight. In addition, chronic treatment of mice with calcitriol markedly reduced tumor burden, although side effects were seen in some mice.
The effect of calcitriol and QW on hormone refractory prostate cancer was also investigated, using castrated TRAMP mice. Results showed that vitamin D had no effect on disease progression in castrated mice as measured by reproductive tract and prostate weight.