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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 expression of AR isoforms in castration resistant prostate tumor metastases.(A) Androgen levels were measured by mass spectrometry in 1–3 soft tissue metastases obtained from each of 8 patients via rapid autopsy. The graph depicts the absolute androgenicity index in each tumor, calculated using a 5∶1 ratio for the relative potency of DHT to T (e.g (5×DHT)+(1×T)). The portion of the total androgenicity contributed by T or DHT is represented by the stacked black and gray bars, respectively. The gray line represents a hypothetical cut point in the androgenicity index between tumors with relatively higher vs. relatively lower tissue androgenicity. Data for T and DHT in LuCaP35 and LuCaP96 tumors from intact mice (No Cx) or recurring after combined hormonal therapy (castration + dutasteride, Cx+D) is presented for comparison. (B) IHC staining scores for AR and PSA expression in 4–5 separate tumor metastases from five of the patients presented in panel A (as indicated by arrows). The % of each patient’s tumors demonstrating no, faint, weak or strong staining for the indicated antibody is presented. AR stains were separately performed using either N or C terminal antibodies to identify N+ but C– tumors consistent with the presence of C terminal truncated AR variants.
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pone-0111545-g005: Androgen levels and expression of AR isoforms in castration resistant prostate tumor metastases.(A) Androgen levels were measured by mass spectrometry in 1–3 soft tissue metastases obtained from each of 8 patients via rapid autopsy. The graph depicts the absolute androgenicity index in each tumor, calculated using a 5∶1 ratio for the relative potency of DHT to T (e.g (5×DHT)+(1×T)). The portion of the total androgenicity contributed by T or DHT is represented by the stacked black and gray bars, respectively. The gray line represents a hypothetical cut point in the androgenicity index between tumors with relatively higher vs. relatively lower tissue androgenicity. Data for T and DHT in LuCaP35 and LuCaP96 tumors from intact mice (No Cx) or recurring after combined hormonal therapy (castration + dutasteride, Cx+D) is presented for comparison. (B) IHC staining scores for AR and PSA expression in 4–5 separate tumor metastases from five of the patients presented in panel A (as indicated by arrows). The % of each patient’s tumors demonstrating no, faint, weak or strong staining for the indicated antibody is presented. AR stains were separately performed using either N or C terminal antibodies to identify N+ but C– tumors consistent with the presence of C terminal truncated AR variants.

Mentions: Notably, patients could be grouped into subsets whose metastases had a relatively high vs. relatively low androgenicity index, similar to that observed for treatment-recurrent LuCaP35 and LuCaP96 tumors (above or below an arbitrary cutpoint derived from visual inspection; Figure 5A). Moreover, patients 1 and 3 whose metastases were characterized by a higher androgenicity index with a relatively larger contribution of DHT (similar to castration recurrent LuCaP35) demonstrated primarily ARN+ and ARC+ staining, consistent with detection of ARFL, and were consistently PSA positive (Figure 5B). In contrast, patients 5, 7, and 8 whose metastases were characterized by a lower androgenicity index with a relatively lower contribution of DHT (and more similar to castration recurrent LuCaP96), demonstrated loss of AR C-terminal staining and more variable PSA staining, consistent with the expression of truncated ARsv.


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 expression of AR isoforms in castration resistant prostate tumor metastases.(A) Androgen levels were measured by mass spectrometry in 1–3 soft tissue metastases obtained from each of 8 patients via rapid autopsy. The graph depicts the absolute androgenicity index in each tumor, calculated using a 5∶1 ratio for the relative potency of DHT to T (e.g (5×DHT)+(1×T)). The portion of the total androgenicity contributed by T or DHT is represented by the stacked black and gray bars, respectively. The gray line represents a hypothetical cut point in the androgenicity index between tumors with relatively higher vs. relatively lower tissue androgenicity. Data for T and DHT in LuCaP35 and LuCaP96 tumors from intact mice (No Cx) or recurring after combined hormonal therapy (castration + dutasteride, Cx+D) is presented for comparison. (B) IHC staining scores for AR and PSA expression in 4–5 separate tumor metastases from five of the patients presented in panel A (as indicated by arrows). The % of each patient’s tumors demonstrating no, faint, weak or strong staining for the indicated antibody is presented. AR stains were separately performed using either N or C terminal antibodies to identify N+ but C– tumors consistent with the presence of C terminal truncated AR variants.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0111545-g005: Androgen levels and expression of AR isoforms in castration resistant prostate tumor metastases.(A) Androgen levels were measured by mass spectrometry in 1–3 soft tissue metastases obtained from each of 8 patients via rapid autopsy. The graph depicts the absolute androgenicity index in each tumor, calculated using a 5∶1 ratio for the relative potency of DHT to T (e.g (5×DHT)+(1×T)). The portion of the total androgenicity contributed by T or DHT is represented by the stacked black and gray bars, respectively. The gray line represents a hypothetical cut point in the androgenicity index between tumors with relatively higher vs. relatively lower tissue androgenicity. Data for T and DHT in LuCaP35 and LuCaP96 tumors from intact mice (No Cx) or recurring after combined hormonal therapy (castration + dutasteride, Cx+D) is presented for comparison. (B) IHC staining scores for AR and PSA expression in 4–5 separate tumor metastases from five of the patients presented in panel A (as indicated by arrows). The % of each patient’s tumors demonstrating no, faint, weak or strong staining for the indicated antibody is presented. AR stains were separately performed using either N or C terminal antibodies to identify N+ but C– tumors consistent with the presence of C terminal truncated AR variants.
Mentions: Notably, patients could be grouped into subsets whose metastases had a relatively high vs. relatively low androgenicity index, similar to that observed for treatment-recurrent LuCaP35 and LuCaP96 tumors (above or below an arbitrary cutpoint derived from visual inspection; Figure 5A). Moreover, patients 1 and 3 whose metastases were characterized by a higher androgenicity index with a relatively larger contribution of DHT (similar to castration recurrent LuCaP35) demonstrated primarily ARN+ and ARC+ staining, consistent with detection of ARFL, and were consistently PSA positive (Figure 5B). In contrast, patients 5, 7, and 8 whose metastases were characterized by a lower androgenicity index with a relatively lower contribution of DHT (and more similar to castration recurrent LuCaP96), demonstrated loss of AR C-terminal staining and more variable PSA staining, consistent with the expression of truncated ARsv.

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