Harvested tumors were stained for Ki67 and subjected to steroid measurement by LC-MS.RESULTS: GnRHR2 was readily detectable in PC cells. AR transcriptional activity reported by PSA-Luc assay was modulated by both Leup and Deg. In LNCaP and C4-2B MDVR cells, 20µM Deg significantly reduced the cell viability (p<0.01). GnRH-antagonist (alone or in combination with AA or Enza) counteracted the transactivation activity of AR by reducing AR-FL and AR variants at the protein level. In C4-2BMDVR cells, Deg reduced AR-V7 protein expression by 26 to 40% alone or combined with AA and Enza compared to control. Leup, however, enhanced variant expression. Deg reduced AR-variant levels from 17 to 41% in monotherapy or combinations compared to control. In mice, Leup slightly suppressed tumor growth compared to controls (p>0.05). However, tumors in Deg-treated group were 1.5-fold smaller than Leup-treated group but 1.7-fold bigger than surgical castration-group. Ki67 IHC staining confirmed the difference in tumor proliferation among groups. Measurements of intratumoral steroids by LC-MS from tumors, serum samples or cell pellets confirmed that Deg decreased the levels of testosterone and steroidogenesis pathway intermediates, comparable to surgical castration; while Leup had no inhibitory effect.CONCLUSIONS: Our results suggest a selective mechanism of action of Deg against AR-variants. The present study provides additional molecular insights regarding the mechanism of Deg compared to GnRH agonist therapy which may have clinical implications.
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