Assessment of Androgen Receptor Splice Variant-7 as a Biomarker of Clinical Response in Castration-Sensitive Prostate Cancer.

PURPOSE: Therapies targeting the androgen receptor (AR) have improved the outcome for patients with castration-sensitive prostate cancer (CSPC). Expression of the constitutively active AR splice variant-7 (AR-V7) has shown clinical utility as a predictive biomarker of AR-targeted therapy resistance in castration-resistant prostate cancer (CRPC), but its importance in CSPC remains understudied. EXPERIMENTAL DESIGN: We assessed different approaches to quantify AR-V7 mRNA and protein in prostate cancer cell lines, patient-derived xenograft (PDX) models, publicly available cohorts, and independent institutional clinical cohorts, to identify reliable approaches for detecting AR-V7 mRNA and protein and its association with clinical outcome. RESULTS: In CSPC and CRPC cohorts, AR-V7 mRNA was much less abundant when detected using reads across splice boundaries than when considering isoform-specific exonic reads. The RM7 AR-V7 antibody had increased sensitivity and specificity for AR-V7 protein detection by immunohistochemistry (IHC) in CRPC cohorts but rarely identified AR-V7 protein reactivity in CSPC cohorts, when compared with the EPR15656 AR-V7 antibody. Using multiple CRPC PDX models, we demonstrated that AR-V7 expression was exquisitely sensitive to hormonal manipulation. In CSPC institutional cohorts, AR-V7 protein quantification by either assay was associated neither with time to development of castration resistance nor with overall survival, and intense neoadjuvant androgen-deprivation therapy did not lead to significant AR-V7 mRNA or staining following treatment. Neither pre- nor posttreatment AR-V7 levels were associated with volumes of residual disease after therapy. CONCLUSIONS: This study demonstrates that further analytical validation and clinical qualification are required before AR-V7 can be considered for clinical use in CSPC as a predictive biomarker

Assessment of Androgen Receptor Splice Variant-7 as a Biomarker of Clinical Response in Castration-Sensitive Prostate Cancer.

PURPOSE: Therapies targeting the androgen receptor (AR) have improved the outcome for patients with castration-sensitive prostate cancer (CSPC). Expression of the constitutively active AR splice variant-7 (AR-V7) has shown clinical utility as a predictive biomarker of AR-targeted therapy resistance in castration-resistant prostate cancer (CRPC), but its importance in CSPC remains understudied. EXPERIMENTAL DESIGN: We assessed different approaches to quantify AR-V7 mRNA and protein in prostate cancer cell lines, patient-derived xenograft (PDX) models, publicly available cohorts, and independent institutional clinical cohorts, to identify reliable approaches for detecting AR-V7 mRNA and protein and its association with clinical outcome. RESULTS: In CSPC and CRPC cohorts, AR-V7 mRNA was much less abundant when detected using reads across splice boundaries than when considering isoform-specific exonic reads. The RM7 AR-V7 antibody had increased sensitivity and specificity for AR-V7 protein detection by immunohistochemistry (IHC) in CRPC cohorts but rarely identified AR-V7 protein reactivity in CSPC cohorts, when compared with the EPR15656 AR-V7 antibody. Using multiple CRPC PDX models, we demonstrated that AR-V7 expression was exquisitely sensitive to hormonal manipulation. In CSPC institutional cohorts, AR-V7 protein quantification by either assay was associated neither with time to development of castration resistance nor with overall survival, and intense neoadjuvant androgen-deprivation therapy did not lead to significant AR-V7 mRNA or staining following treatment. Neither pre- nor posttreatment AR-V7 levels were associated with volumes of residual disease after therapy. CONCLUSIONS: This study demonstrates that further analytical validation and clinical qualification are required before AR-V7 can be considered for clinical use in CSPC as a predictive biomarker

Highly efficient sorghum transformation

A highly efficient microprojectile transformation system for sorghum (Sorghum bicolor L.) has been developed by using immature embryos (IEs) of inbred line Tx430. Co-bombardment was performed with the neomycin phosphotransferase II (nptII) gene and the green fluorescent protein (gfp) gene, both under the control of the maize ubiquitin1 (ubi1) promoter. After optimization of both tissue culture media and parameters of microprojectile transformation, 25 independent transgenic events were obtained from 121 bombarded IEs. The average transformation frequency (the total number of independent transgenic events divided by the total number of bombarded IEs) was 20.7% in three independent experiments. Transgenic events were confirmed by both PCR screening and Southern hybridization of genomic DNA from primary transgenics (T ). More than 90% of transformants were fertile and displayed normal morphology in a containment glasshouse. Co-transformation rate of the nptII and gfp genes was 72% in these experiments. The segregation of nptII and gfp in T progenies was observed utilizing fluorescence microscopy and geneticin selection of seedlings indicating both were inherited in the T generation. The transformation procedure, from initiating IEs to planting putative transgenic plantlets in the glasshouse, was completed within 11-16 weeks, and was approximately threefold more efficient than the previously reported best sorghum transformation system

NXP800 Activates the Unfolded Protein Response, Altering AR and E2F Function to Impact Castration-Resistant Prostate Cancer Growth.

PURPOSE: Advanced prostate cancer is invariably fatal, with the androgen receptor (AR) being a major therapeutic target. AR signaling inhibitors have improved overall survival for men with advanced prostate cancer, but treatment resistance is inevitable and includes reactivation of AR signaling. Novel therapeutic approaches targeting these mechanisms to block tumor growth is an urgent unmet clinical need. One attractive strategy is to target heat shock proteins (HSP) critical to AR functional activity. EXPERIMENTAL DESIGN: We first did transcriptome analysis on multiple castration-resistant prostate cancer (CRPC) cohorts to correlate the association between the Gene Ontology cellular response to heat gene expression signature and overall survival. Next, we analyzed the impact of targeting the heat shock factor 1 (HSF1) pathway, with an inhibitor in clinical development, namely, NXP800 (formerly CCT361814), in models of treatment-resistant prostate cancer. Finally, we confirmed our mechanistic and phenotypic findings using an NXP800-resistant model and an in vivo model of CRPC. RESULTS: We report that in multiple CRPC transcriptome cohorts, the Gene Ontology cellular response to heat gene expression signature associates with AR signaling and worse clinical outcome. We demonstrate the effects of targeting the HSF1 pathway, central to cellular stress, with an inhibitor in clinical development, namely, NXP800, in prostate cancer. Targeting the HSF1 pathway with the inhibitor NXP800 decreases HSP72 expression, activates the unfolded protein response, and inhibits AR- and E2F-mediated activity, inhibiting the growth of treatment-resistant prostate cancer models. CONCLUSIONS: Overall, NXP800 has antitumor activity against treatment-resistant prostate cancer models, including molecular subtypes with limited treatment options, supporting its consideration for prostate cancer-specific clinical development