Vitamin D2 analog active against leukemia, myeloma, and colon cancer

Paricalcitol, a synthetic vitamin D2 analog approved by the U.S. Food and Drug Administration for the treatment of hyperparathyroidism secondary to chronic kidney failure, may slow the growth of a variety of tumors without causing hypercalcemia like its cousin, vitamin D3.

That’s according to a report in the June 18 issue of The Journal of the National Cancer Institute, from Dr. Takashi Kumagai of Cedars-Sinai Medical Center in Los Angeles and colleagues.In their experiments, paricalcitol inhibited proliferation of myeloid leukemia, myeloma, and colon cancer cell lines by modulating cell cycle progression, differentiation, and apoptosis, as well as inducing expression of several tumor suppressor genes including PTEN and E-cadherin. In addition, paricalcitol inhibited the in vivo growth of human colon cancer xenografts in nude mice. Tumors in paricalcitol-treated animals were smaller (P=0.03) and weighed less (P<0.001) than tumors in control-treated mice.Because paricalcitol has "very little" calcemic activity, it can be given at higher doses than vitamin D3 without toxicity, potentially leading to greater efficacy in the treatment of vitamin D3-sensitive cancers, the authors say. "Innovative clinical trials of this agent for preleukemia (myelodysplastic syndrome), maintenance therapy for acute myeloid leukemia and multiple myeloma, and adjuvant therapy for colon cancer are reasonable to consider," they conclude. (Source: J Natl Cancer Inst 2003;95:896-905: Reuters Health: June 23, 2003: Oncolink)