Inecalcitol, an analog of 1α,25(OH)(2) D(3) , induces growth arrest of androgen-dependent prostate cancer cells

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Published on Wednesday, 05 February 2014

Abstract

19-nor-14-epi-23-yne-1,25(OH)(2) D(3) (inecalcitol) is a unique vitamin D(3) analog. We evaluated the activity of inecalcitol in a human prostate cancer model system.

The analog was 11-fold more potent than 1,25(OH)(2) D(3) in causing 50% clonal growth inhibition of androgen-sensitive human prostate cancer LNCaP cells.

Inecalcitol, more than 1,25(OH)(2) D(3), reduced in a dose-dependent manner the expression levels of the transcription factor ETS variant 1 and the serine/threonine protein kinase Pim-1, both of which are upregulated in prostate cancer.

Remarkably, dose challenge experiments revealed that inecalcitol maximal tolerated dose (MTD) by intraperitoneal (i.p.) administration was 30 μg/mouse (1,300 μg/kg) three times per week, while we previously found that the MTD of 1,25(OH)(2) D(3) is 0.0625 μg/mouse; therefore, inecalcitol is 480 times less hypercalcemic than 1,25(OH)(2) D(3). Pharmacokinetic studies showed that plasma half-life of inecalcitol were 18.3 min in mice.

A xenograft model of LNCaP cells was developed in immunodeficient mice treated with inecalcitol. The tumors of the diluent-treated control mice increased in size but those in the inecalcitol treatment group did not grow.

Our data suggest that inecalcitol inhibits androgen-responsive prostate cancer growth in vivo and should be examined either alone or with other chemotherapy in clinical trials in individuals with rising serum prostate-specific antigen after receiving either surgery or irradiation therapy with curative intent.

 

 

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