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Identification of Androgen Receptor Splice Variants in the Pten Deficient Murine Prostate Cancer Model.

Liang M, Adisetiyo H, Liu X, Liu R, Gill P, Roy-Burman P, Jones JO, Mulholland DJ - PLoS ONE (2015)

Bottom Line: Variants appear not only conserved throughout progression but are correlated with nearly complete loss of full length AR (AR-FL) at castrate androgen levels.The overexpression of variants leads to enhanced transcriptional activity of AR while knock down studies show reduced transcriptional output.Collectively, the identification of truncated AR variants in the conditional PTEN deletion model supports a role for maintaining the CRPC phenotype and provides further therapeutic applications of this preclinical model.

View Article: PubMed Central - PubMed

Affiliation: Icahn School of Medicine at Mount Sinai, New York, New York, United States of America.

ABSTRACT
Androgen receptor (AR) variants are associated with resistance to anti androgen therapy both in human prostate cancer cell lines and clinical samples. These observations support the hypothesis that AR isoform accumulation is a consequence of selective therapeutic pressure on the full length AR. The Pten deficient prostate cancer model proceeds with well-defined kinetics including progression to castration resistant prostate cancer (CRPC). While surgical castration and enzalutamide treatments yield an initial therapeutic response, Pten-/-epithelia continue to proliferate yielding locally invasive primary tumor pathology. That most epithelium remains AR positive, but ligand independent, suggests the presence of oncogenic AR variants. To address this hypothesis, we have used a panel of recently described Pten-/- tumor cell lines derived from both from hormone intact (E4, E8) and castrated Pten mutants (cE1, cE2) followed by RACE PCR to identify and characterize three novel truncated, amino terminus containing AR variants (mAR-Va, b, c). Variants appear not only conserved throughout progression but are correlated with nearly complete loss of full length AR (AR-FL) at castrate androgen levels. The overexpression of variants leads to enhanced transcriptional activity of AR while knock down studies show reduced transcriptional output. Collectively, the identification of truncated AR variants in the conditional PTEN deletion model supports a role for maintaining the CRPC phenotype and provides further therapeutic applications of this preclinical model.

No MeSH data available.


Related in: MedlinePlus

Knock down of androgen receptor variants regulates AR transcriptional activity in Pten deficient murine prostate cancer cell lines.a) E8 cells were transfected with siRNAs targeting either mAR-Va or c and evaluated for PSA-luc reporter activity 48 hours later (control siRNA vs. mAR-Va siRNA = comparisons 1–3; control siRNA vs. mAR-Vc siRNA = comparisons 4–7). b) Validation of siRNA knockdown of mAR-Vc as measured by q-PCR (*, p<0.05, **, p<0.01).
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pone.0131232.g004: Knock down of androgen receptor variants regulates AR transcriptional activity in Pten deficient murine prostate cancer cell lines.a) E8 cells were transfected with siRNAs targeting either mAR-Va or c and evaluated for PSA-luc reporter activity 48 hours later (control siRNA vs. mAR-Va siRNA = comparisons 1–3; control siRNA vs. mAR-Vc siRNA = comparisons 4–7). b) Validation of siRNA knockdown of mAR-Vc as measured by q-PCR (*, p<0.05, **, p<0.01).

Mentions: We then considered the effects of variant inhibition on PSA transcriptional reporter output. To do this we designed DICER substrate siRNAs (DsiRNAs) that would specifically target mAR-Va or c, but not full length AR. Through transfection of these siRNAs into E8 or cE1 cells along with the luciferase reporter plasmids, it was observed that knockdown of either mAR-Va and Vc reduced AR transcriptional activity in both cell lines (Fig 4a). Variant siRNAs were equally potent in E8 cells while in cE1 cells, knockdown of mAR-Vc yielded the most robust effect (data not shown). The efficiency of variant knock down is exemplified by q-PCR measurement of mAR-Vc levels in control and mAR-Vc-siRNA treated E8 cells (Fig 4b).


Identification of Androgen Receptor Splice Variants in the Pten Deficient Murine Prostate Cancer Model.

Liang M, Adisetiyo H, Liu X, Liu R, Gill P, Roy-Burman P, Jones JO, Mulholland DJ - PLoS ONE (2015)

Knock down of androgen receptor variants regulates AR transcriptional activity in Pten deficient murine prostate cancer cell lines.a) E8 cells were transfected with siRNAs targeting either mAR-Va or c and evaluated for PSA-luc reporter activity 48 hours later (control siRNA vs. mAR-Va siRNA = comparisons 1–3; control siRNA vs. mAR-Vc siRNA = comparisons 4–7). b) Validation of siRNA knockdown of mAR-Vc as measured by q-PCR (*, p<0.05, **, p<0.01).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4510390&req=5

pone.0131232.g004: Knock down of androgen receptor variants regulates AR transcriptional activity in Pten deficient murine prostate cancer cell lines.a) E8 cells were transfected with siRNAs targeting either mAR-Va or c and evaluated for PSA-luc reporter activity 48 hours later (control siRNA vs. mAR-Va siRNA = comparisons 1–3; control siRNA vs. mAR-Vc siRNA = comparisons 4–7). b) Validation of siRNA knockdown of mAR-Vc as measured by q-PCR (*, p<0.05, **, p<0.01).
Mentions: We then considered the effects of variant inhibition on PSA transcriptional reporter output. To do this we designed DICER substrate siRNAs (DsiRNAs) that would specifically target mAR-Va or c, but not full length AR. Through transfection of these siRNAs into E8 or cE1 cells along with the luciferase reporter plasmids, it was observed that knockdown of either mAR-Va and Vc reduced AR transcriptional activity in both cell lines (Fig 4a). Variant siRNAs were equally potent in E8 cells while in cE1 cells, knockdown of mAR-Vc yielded the most robust effect (data not shown). The efficiency of variant knock down is exemplified by q-PCR measurement of mAR-Vc levels in control and mAR-Vc-siRNA treated E8 cells (Fig 4b).

Bottom Line: Variants appear not only conserved throughout progression but are correlated with nearly complete loss of full length AR (AR-FL) at castrate androgen levels.The overexpression of variants leads to enhanced transcriptional activity of AR while knock down studies show reduced transcriptional output.Collectively, the identification of truncated AR variants in the conditional PTEN deletion model supports a role for maintaining the CRPC phenotype and provides further therapeutic applications of this preclinical model.

View Article: PubMed Central - PubMed

Affiliation: Icahn School of Medicine at Mount Sinai, New York, New York, United States of America.

ABSTRACT
Androgen receptor (AR) variants are associated with resistance to anti androgen therapy both in human prostate cancer cell lines and clinical samples. These observations support the hypothesis that AR isoform accumulation is a consequence of selective therapeutic pressure on the full length AR. The Pten deficient prostate cancer model proceeds with well-defined kinetics including progression to castration resistant prostate cancer (CRPC). While surgical castration and enzalutamide treatments yield an initial therapeutic response, Pten-/-epithelia continue to proliferate yielding locally invasive primary tumor pathology. That most epithelium remains AR positive, but ligand independent, suggests the presence of oncogenic AR variants. To address this hypothesis, we have used a panel of recently described Pten-/- tumor cell lines derived from both from hormone intact (E4, E8) and castrated Pten mutants (cE1, cE2) followed by RACE PCR to identify and characterize three novel truncated, amino terminus containing AR variants (mAR-Va, b, c). Variants appear not only conserved throughout progression but are correlated with nearly complete loss of full length AR (AR-FL) at castrate androgen levels. The overexpression of variants leads to enhanced transcriptional activity of AR while knock down studies show reduced transcriptional output. Collectively, the identification of truncated AR variants in the conditional PTEN deletion model supports a role for maintaining the CRPC phenotype and provides further therapeutic applications of this preclinical model.

No MeSH data available.


Related in: MedlinePlus