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Prostate cancer characteristics associated with response to pre-receptor targeting of the androgen axis.

Mostaghel EA, Morgan A, Zhang X, Marck BT, Xia J, Hunter-Merrill R, Gulati R, Plymate S, Vessella RL, Corey E, Higano CS, Matsumoto AM, Montgomery RB, Nelson PS - PLoS ONE (2014)

Bottom Line: In LuCaP96 tumors (T:DHT 10:1), survival was not improved despite similar DHT reduction (0.02 ng/gm).Intrinsic differences in basal steroidogenesis, as well as variable expression of full length and splice-variant AR, associate with response and resistance to pre-receptor AR ligand suppression.Expression of steroidogenic enzymes and AR isoforms may serve as potential biomarkers of sensitivity to potent AR-axis inhibition and should be validated in additional models.

View Article: PubMed Central - PubMed

Affiliation: Division of Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America; Department of Medicine, University of Washington School of Medicine, Seattle, Washington, United States of America.

ABSTRACT

Background: Factors influencing differential responses of prostate tumors to androgen receptor (AR) axis-directed therapeutics are poorly understood, and predictors of treatment efficacy are needed. We hypothesized that the efficacy of inhibiting DHT ligand synthesis would associate with intra-tumoral androgen ratios indicative of relative dependence on DHT-mediated growth.

Methods: We characterized two androgen-sensitive prostate cancer xenograft models after androgen suppression by castration in combination with the SRD5A inhibitor, dutasteride, as well as a panel of castration resistant metastases obtained via rapid autopsy.

Results: In LuCaP35 tumors (intra-tumoral T:DHT ratio 2:1) dutasteride suppressed DHT to 0.02 ng/gm and prolonged survival vs. castration alone (337 vs.152 days, HR 2.8, p = 0.0015). In LuCaP96 tumors (T:DHT 10:1), survival was not improved despite similar DHT reduction (0.02 ng/gm). LuCaP35 demonstrated higher expression of steroid biosynthetic enzymes maintaining DHT levels (5-fold higher SRD5A1, 41 fold higher, 99-fold higher RL-HSD, p<0.0001 for both), reconstitution of intra-tumoral DHT (to ∼30% of untreated tumors), and ∼2 fold increased expression of full length AR. In contrast, LuCaP96 demonstrated higher levels of steroid catabolizing enzymes (6.9-fold higher AKR1C2, 3000-fold higher UGT2B15, p = 0.002 and p<0.0001 respectively), persistent suppression of intra-tumoral DHT, and 6-8 fold induction of full length AR and the ligand independent V7 AR splice variant. Human metastases demonstrated bio-active androgen levels and AR full length and AR splice-variant expression consistent with the range observed in xenografts.

Conclusions: Intrinsic differences in basal steroidogenesis, as well as variable expression of full length and splice-variant AR, associate with response and resistance to pre-receptor AR ligand suppression. Expression of steroidogenic enzymes and AR isoforms may serve as potential biomarkers of sensitivity to potent AR-axis inhibition and should be validated in additional models.

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Androgen levels and AR expression in prostate cancer xenografts treated with castration and dutasteride.Tissue testosterone (T, black bars) and DHT (gray bars) levels were measured by mass spectrometry in LuCaP35 (A) and LuCap96 (B) tumors resected from intact mice (No Cx), and from mice treated with castration alone (Cx) or castration + dutasteride (Cx+Dut) at early time points (d3-21, while still on therapy, indicated by double-headed arrows), or at castration-resistant re-growth (defined as >750 mm3). P values computed from Welch’s two sample t test (p<0.05 were considered significant). Single stars indicate a statistically significant difference in DHT levels between Cx vs. Cx+Dut treated samples at d3-21 of treatment. Double stars indicate a significant difference in DHT levels between Cx vs. Cx+Dut treated samples even after castration-recurrent re-growth. No other comparisons between Cx vs. Cx + Dut treated groups were significant. Expression of full length (FL) AR and the AR variant 7 (ARV7) truncated splice variant was measured in LuCaP35 (C) and LuCaP96 (D) at the time of tumor re-growth to 750 mm3. Transcript expression was measured by qRT-PCR and normalized to expression of the housekeeping gene RPL13A within each sample to yield the delta cycle threshold (dCt). The relative difference in expression between the indicated treatment groups was calculated using the delta dCt method (fold change = 2∧ddCt). P values computed from Welch’s two sample t test (p<0.05 were considered significant).
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pone-0111545-g004: Androgen levels and AR expression in prostate cancer xenografts treated with castration and dutasteride.Tissue testosterone (T, black bars) and DHT (gray bars) levels were measured by mass spectrometry in LuCaP35 (A) and LuCap96 (B) tumors resected from intact mice (No Cx), and from mice treated with castration alone (Cx) or castration + dutasteride (Cx+Dut) at early time points (d3-21, while still on therapy, indicated by double-headed arrows), or at castration-resistant re-growth (defined as >750 mm3). P values computed from Welch’s two sample t test (p<0.05 were considered significant). Single stars indicate a statistically significant difference in DHT levels between Cx vs. Cx+Dut treated samples at d3-21 of treatment. Double stars indicate a significant difference in DHT levels between Cx vs. Cx+Dut treated samples even after castration-recurrent re-growth. No other comparisons between Cx vs. Cx + Dut treated groups were significant. Expression of full length (FL) AR and the AR variant 7 (ARV7) truncated splice variant was measured in LuCaP35 (C) and LuCaP96 (D) at the time of tumor re-growth to 750 mm3. Transcript expression was measured by qRT-PCR and normalized to expression of the housekeeping gene RPL13A within each sample to yield the delta cycle threshold (dCt). The relative difference in expression between the indicated treatment groups was calculated using the delta dCt method (fold change = 2∧ddCt). P values computed from Welch’s two sample t test (p<0.05 were considered significant).

Mentions: To determine whether the differential impact of SRD5A inhibition on tumor growth reflected a difference in suppression of intratumoral androgens, we measured T and DHT levels in tumors resected after treatment. In both LuCaP35 and LuCaP96 tumor types, mean tumor DHT levels measured at 3–21 days (indicated by two-headed arrows in Figure 4A and 4B) were substantially lower in castration plus dutasteride vs. the castration alone groups, with values in LuCaP35 suppressed from 0.40±0.56 ng/gm to 0.02±0.04, p = 0.007 and in LuCaP96 from 0.10±0.08 ng/gm to 0.02±0.01, p = 0.005 (summarized in Table S1).


Prostate cancer characteristics associated with response to pre-receptor targeting of the androgen axis.

Mostaghel EA, Morgan A, Zhang X, Marck BT, Xia J, Hunter-Merrill R, Gulati R, Plymate S, Vessella RL, Corey E, Higano CS, Matsumoto AM, Montgomery RB, Nelson PS - PLoS ONE (2014)

Androgen levels and AR expression in prostate cancer xenografts treated with castration and dutasteride.Tissue testosterone (T, black bars) and DHT (gray bars) levels were measured by mass spectrometry in LuCaP35 (A) and LuCap96 (B) tumors resected from intact mice (No Cx), and from mice treated with castration alone (Cx) or castration + dutasteride (Cx+Dut) at early time points (d3-21, while still on therapy, indicated by double-headed arrows), or at castration-resistant re-growth (defined as >750 mm3). P values computed from Welch’s two sample t test (p<0.05 were considered significant). Single stars indicate a statistically significant difference in DHT levels between Cx vs. Cx+Dut treated samples at d3-21 of treatment. Double stars indicate a significant difference in DHT levels between Cx vs. Cx+Dut treated samples even after castration-recurrent re-growth. No other comparisons between Cx vs. Cx + Dut treated groups were significant. Expression of full length (FL) AR and the AR variant 7 (ARV7) truncated splice variant was measured in LuCaP35 (C) and LuCaP96 (D) at the time of tumor re-growth to 750 mm3. Transcript expression was measured by qRT-PCR and normalized to expression of the housekeeping gene RPL13A within each sample to yield the delta cycle threshold (dCt). The relative difference in expression between the indicated treatment groups was calculated using the delta dCt method (fold change = 2∧ddCt). P values computed from Welch’s two sample t test (p<0.05 were considered significant).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4214744&req=5

pone-0111545-g004: Androgen levels and AR expression in prostate cancer xenografts treated with castration and dutasteride.Tissue testosterone (T, black bars) and DHT (gray bars) levels were measured by mass spectrometry in LuCaP35 (A) and LuCap96 (B) tumors resected from intact mice (No Cx), and from mice treated with castration alone (Cx) or castration + dutasteride (Cx+Dut) at early time points (d3-21, while still on therapy, indicated by double-headed arrows), or at castration-resistant re-growth (defined as >750 mm3). P values computed from Welch’s two sample t test (p<0.05 were considered significant). Single stars indicate a statistically significant difference in DHT levels between Cx vs. Cx+Dut treated samples at d3-21 of treatment. Double stars indicate a significant difference in DHT levels between Cx vs. Cx+Dut treated samples even after castration-recurrent re-growth. No other comparisons between Cx vs. Cx + Dut treated groups were significant. Expression of full length (FL) AR and the AR variant 7 (ARV7) truncated splice variant was measured in LuCaP35 (C) and LuCaP96 (D) at the time of tumor re-growth to 750 mm3. Transcript expression was measured by qRT-PCR and normalized to expression of the housekeeping gene RPL13A within each sample to yield the delta cycle threshold (dCt). The relative difference in expression between the indicated treatment groups was calculated using the delta dCt method (fold change = 2∧ddCt). P values computed from Welch’s two sample t test (p<0.05 were considered significant).
Mentions: To determine whether the differential impact of SRD5A inhibition on tumor growth reflected a difference in suppression of intratumoral androgens, we measured T and DHT levels in tumors resected after treatment. In both LuCaP35 and LuCaP96 tumor types, mean tumor DHT levels measured at 3–21 days (indicated by two-headed arrows in Figure 4A and 4B) were substantially lower in castration plus dutasteride vs. the castration alone groups, with values in LuCaP35 suppressed from 0.40±0.56 ng/gm to 0.02±0.04, p = 0.007 and in LuCaP96 from 0.10±0.08 ng/gm to 0.02±0.01, p = 0.005 (summarized in Table S1).

Bottom Line: In LuCaP96 tumors (T:DHT 10:1), survival was not improved despite similar DHT reduction (0.02 ng/gm).Intrinsic differences in basal steroidogenesis, as well as variable expression of full length and splice-variant AR, associate with response and resistance to pre-receptor AR ligand suppression.Expression of steroidogenic enzymes and AR isoforms may serve as potential biomarkers of sensitivity to potent AR-axis inhibition and should be validated in additional models.

View Article: PubMed Central - PubMed

Affiliation: Division of Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America; Department of Medicine, University of Washington School of Medicine, Seattle, Washington, United States of America.

ABSTRACT

Background: Factors influencing differential responses of prostate tumors to androgen receptor (AR) axis-directed therapeutics are poorly understood, and predictors of treatment efficacy are needed. We hypothesized that the efficacy of inhibiting DHT ligand synthesis would associate with intra-tumoral androgen ratios indicative of relative dependence on DHT-mediated growth.

Methods: We characterized two androgen-sensitive prostate cancer xenograft models after androgen suppression by castration in combination with the SRD5A inhibitor, dutasteride, as well as a panel of castration resistant metastases obtained via rapid autopsy.

Results: In LuCaP35 tumors (intra-tumoral T:DHT ratio 2:1) dutasteride suppressed DHT to 0.02 ng/gm and prolonged survival vs. castration alone (337 vs.152 days, HR 2.8, p = 0.0015). In LuCaP96 tumors (T:DHT 10:1), survival was not improved despite similar DHT reduction (0.02 ng/gm). LuCaP35 demonstrated higher expression of steroid biosynthetic enzymes maintaining DHT levels (5-fold higher SRD5A1, 41 fold higher, 99-fold higher RL-HSD, p<0.0001 for both), reconstitution of intra-tumoral DHT (to ∼30% of untreated tumors), and ∼2 fold increased expression of full length AR. In contrast, LuCaP96 demonstrated higher levels of steroid catabolizing enzymes (6.9-fold higher AKR1C2, 3000-fold higher UGT2B15, p = 0.002 and p<0.0001 respectively), persistent suppression of intra-tumoral DHT, and 6-8 fold induction of full length AR and the ligand independent V7 AR splice variant. Human metastases demonstrated bio-active androgen levels and AR full length and AR splice-variant expression consistent with the range observed in xenografts.

Conclusions: Intrinsic differences in basal steroidogenesis, as well as variable expression of full length and splice-variant AR, associate with response and resistance to pre-receptor AR ligand suppression. Expression of steroidogenic enzymes and AR isoforms may serve as potential biomarkers of sensitivity to potent AR-axis inhibition and should be validated in additional models.

Show MeSH
Related in: MedlinePlus