Probes for INS

Abstract

Prostate cancer remains dependent on androgen receptor signaling even after castration. Aberrant androgen receptor signaling in castration resistant prostate cancer is mediated by mechanisms such as alterations in the androgen receptor and activation of interacting signaling pathways. Clinical evidence confirms that resistance to the next generation anti-androgen, enzalutamide, may be mediated to a large extent by alternative splicing of the androgen receptor to generate constitutively active splice variants such as AR-V7. The splice variants AR-V7 and Arv567es have been implicated in the resistance to not only enzalutamide, but also to abiraterone and other conventional therapeutics such as taxanes. Numerous studies including ours suggest that splicing factors such as hnRNPA1 promote the generation of AR-V7, thus contributing to enzalutamide resistance in prostate cancer cells. In the present study, we discovered that quercetin, a naturally occurring polyphenolic compound, reduces the expression of hnRNPA1, and consequently, that of AR-V7. The suppression of AR-V7 by quercetin resensitizes enzalutamide-resistant prostate cancer cells to treatment with enzalutamide. Our results indicate that quercetin downregulates hnRNPA1 expression, downregulates the expression of AR-V7, antagonizes androgen receptor signaling, and resensitizes enzalutamide-resistant prostate cancer cells to enzalutamide treatment in vivo in mouse xenografts. These findings demonstrate that suppressing the alternative splicing of the androgen receptor may have important implications in overcoming the resistance to next-generation anti-androgen therapy.

The favorable features of high-risk human papillomavirus (HPV) in the head and neck are limited to those harboring transcriptionally-active HPV, which occur predominantly in the oropharynx (OP). Factors rendering the OP susceptible to HPV oncogenesis are largely unexplored. The role of cytokeratin 7 (CK7) in predisposition to HPV and cancer in the cervix has been evaluated. However, its significance in the H&N is unknown. CK7 immunohistochemistry was performed on a tissue microarray cohort of OP and non-oropharyngeal (NOP) squamous cell carcinomas (SCC) with known clinical follow-up and HPV E6/7 mRNA status. Expression was graded based on the distribution (1 ≤ 33%, 2 = 33-66%, 3 ≥ 66%) and intensity (1 = weak, 2 = strong) with combined score of ≥ 2 considered positive. Survival analysis was performed. Seventy-four NOPSCCs and 204 OPSCCs were studied. HPV was positive in 2.7% of NOPSCCs and 70.9% of OPSCCs. CK7 was positive in 23.0% of OPSCCs and 14.8% of NOPSCCs (p = 0.2), and in 24.1% of HPV positive versus 17.2% of negative patients (p = 0.2). There was no correlation with age, race, gender, HPV status, histologic type, tumor subsite, treatment, stage, or co-morbidities, and CK7 expression was not significantly associated with overall or disease specific survival. In our series, CK7 is positive in ~ 25% of H&N SCCs, although usually only focally. While CK7 has been suspected to be overexpressed selectively in HPV-related OPSCCs due to their origination from tonsillar crypt epithelium, we did not find any significant difference by anatomic H&N subsite, nor by HPV status, for its expression and found no association with patient survival.

Androgen deprivation therapy (ADT) has been used to treat salivary duct carcinoma (SDC). The androgen receptor splice variant-7 (AR-V7) has been detected in castration-resistant prostate cancer (CRPC) and implicated in resistance to androgen receptor (AR)-targeted therapies. Given the potential role of AR/AR-V7 in SDC treatment, this study focuses on AR/AR-V7 expression in SDC specimens collected prior to ADT. RNA in situ hybridization (ISH) and immunohistochemistry (IHC) to detect total AR and AR-V7 were performed on formalin-fixed, paraffin-embedded SDC specimens from 23 patients. Full length AR (AR-FL) and AR-V7 transcripts were quantified in a subset of tumors by reverse transcription polymerase chain reaction (RT-PCR). Twenty SDCs were positive for total AR by ISH and IHC. Among AR positive SDCs, 70% (14/20) were positive for AR-V7 mRNA by ISH, while 15% (3/20) were positive for AR-V7 protein by IHC. The three SDCs which expressed the highest levels of AR-V7 were all from female patients; one of them expressed significant amount of AR-V7 and barely detectable AR-FL transcripts by RT-PCR. Immunohistochemistry expression of Forkhead box protein A1, prostate-specific antigen, prostatic acid phosphatase, NKX3.1 was observed in some SDCs regardless of patient gender. Five SDCs demonstrated strong human epidermal growth factor receptor 2 (HER2) expression. We conclude that treatment-naïve SDCs may express AR-V7 at levels comparable to or even exceeding the levels detected in CRPC. Our data support the feasibility to incorporate AR-V7 assessment via ISH and/or IHC in the ongoing clinical trials evaluating the therapeutic benefit of AR targeted therapies in SDC patients.

Treatment with androgen-targeted therapies can induce upregulation of epithelial plasticity pathways. Epithelial plasticity is known to be important for metastatic dissemination and therapeutic resistance. The goal of this study is to elucidate the functional consequence of induced epithelial plasticity on AR regulation during disease progression to identify factors important for treatment-resistant and metastatic prostate cancer. We pinpoint the epithelial plasticity transcription factor, Snail, at the nexus of enzalutamide resistance and prostate cancer metastasis both in preclinical models of prostate cancer and in patients. In patients, Snail expression is associated with Gleason 9-10 high-risk disease and is strongly overexpressed in metastases as compared to localized prostate cancer. Snail expression is also elevated in enzalutamide-resistant prostate cancer cells compared to enzalutamide-sensitive cells, and downregulation of Snail re-sensitizes enzalutamide-resistant cells to enzalutamide. While activation of Snail increases migration and invasion, it is also capable of promoting enzalutamide resistance in enzalutamide-sensitive cells. This Snail-mediated enzalutamide resistance is a consequence of increased full-length AR and AR-V7 expression and nuclear localization. Downregulation of either full-length AR or AR-V7 re-sensitizes cells to enzalutamide in the presence of Snail, thus connecting Snail-induced enzalutamide resistance directly to AR biology. Finally, we demonstrate that Snail is capable of mediating-resistance through AR even in the absence of AR-V7. These findings imply that increased Snail expressionduring progression to metastatic disease may prime cells for resistance to AR-targeted therapies by promoting AR activity in prostate cancer.

Primary carcinomas of the urethra are rare and poorly understood lesions, hence their clinical and pathologic spectrum is not completely defined. We analyzed a series of 130 primary urethral tumors and classified 106 of them as primary urethral carcinomas. The age at diagnosis of patients with primary urethral carcinomas ranged from 42-97years (mean: 69.4yrs.; median: 70yrs). There were 73 males and 33 female patients with a ratio of 2.2:1. In male patients the tumors most frequently developed in the bulbous-membranous segment of the urethra. In female patients the entire length of the urethra was typically involved. Microscopically, they were poorly differentiated carcinoma with hybrid squamous and urothelial features and developed from precursor intraepithelial conditions such as dysplasia and carcinoma in situ, which were frequently present in the adjacent urethral mucosa. High risk HPV infection could be documented in 31.6% of these tumors. Follow-up information was available for 95 patients. Twenty-three patients died of the disease with a mean and median survival of 39 and 21months respectively. Urethral carcinomas are aggressive tumors with high propensity for regional and distant metastases with mean and median survival of 39 and 21months respectively. Our observations have important implications for the management of patients with primary carcinoma of the urethra by defining them as a unique entity linked to HPV infection.

Abstract

BACKGROUND:

Androgen receptor splice variant 7 (AR-V7) has been implicated in resistance to abiraterone and enzalutamide treatment in men with metastatic castration-resistant prostate cancer (mCRPC). Tissue- or cell-based in situ detection of AR-V7, however, has been limited by lack of specificity.

OBJECTIVE:

To address current limitations in precision measurement of AR-V7 by developing a novel junction-specific AR-V7 RNA in situ hybridization (RISH) assay compatible with automated quantification.

DESIGN, SETTING, AND PARTICIPANTS:

We designed a RISH method to visualize single splice junctions in cells and tissue. Using the validated assay for junction-specific detection of the full-length AR (AR-FL) and AR-V7, we generated quantitative data, blinded to clinical data, for 63 prostate tumor biopsies.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS:

We evaluated clinical correlates of AR-FL/AR-V7 measurements, including association with prostate-specific antigen progression-free survival (PSA-PFS) and clinical and radiographic progression-free survival (PFS), in a subset of patients starting treatment with abiraterone or enzalutamide following biopsy.

RESULTS AND LIMITATIONS:

Quantitative AR-FL/AR-V7 data were generated from 56 of the 63 (88.9%) biopsy specimens examined, of which 44 were mCRPC biopsies. Positive AR-V7 signals were detected in 34.1% (15/44) mCRPC specimens, all of which also co-expressed AR-FL. The median AR-V7/AR-FL ratio was 11.9% (range 2.7-30.3%). Positive detection of AR-V7 was correlated with indicators of high disease burden at baseline. Among the 25 CRPC biopsies collected before treatment with abiraterone or enzalutamide, positive AR-V7 detection, but not higher AR-FL, was significantly associated with shorter PSA-PFS (hazard ratio 2.789, 95% confidence interval 1.12-6.95; p=0.0081).

CONCLUSIONS:

We report for the first time a RISH method for highly specific and quantifiable detection of splice junctions, allowing further characterization of AR-V7 and its clinical significance.

PATIENT SUMMARY:

Higher AR-V7 levels detected and quantified using a novel method were associated with poorer response to abiraterone or enzalutamide in prostate cancer.

Abstract

Background
The androgen receptor splice variant-7 (AR-V7) has been implicated in the development of castration-resistant prostate cancer (CRPC) and resistance to abiraterone and enzalutamide.

Objective
To develop a validated assay for detection of AR-V7 protein in tumour tissue and determine its expression and clinical significance as patients progress from hormone-sensitive prostate cancer (HSPC) to CRPC.

Design, setting, and participants
Following monoclonal antibody generation and validation, we retrospectively identified patients who had HSPC and CRPC tissue available for AR-V7 immunohistochemical (IHC) analysis.

Outcome measurements and statistical analysis
Nuclear AR-V7 expression was determined using IHC H score (HS) data. The change in nuclear AR-V7 expression from HSPC to CRPC and the association between nuclear AR-V7 expression and overall survival (OS) was determined.

Results and limitations
Nuclear AR-V7 expression was significantly lower in HSPC (median HS 50, interquartile range [IQR] 17.5–90) compared to CRPC (HS 135, IQR 80–157.5; p < 0.0001), and in biopsy tissue taken before (HS 80, IQR 30–136.3) compared to after (HS 140, IQR 105–167.5; p = 0.007) abiraterone or enzalutamide treatment. Lower nuclear AR-V7 expression at CRPC biopsy was associated with longer OS (hazard ratio 1.012, 95% confidence interval 1.004–1.020; p = 0.003). While this monoclonal antibody primarily binds to AR-V7 in PC biopsy tissue, it may also bind to other proteins.

Conclusions
We provide the first evidence that nuclear AR-V7 expression increases with emerging CRPC and is prognostic for OS, unlike antibody staining for the AR N-terminal domain. These data indicate that AR-V7 is important in CRPC disease biology; agents targeting AR splice variants are needed to test this hypothesis and further improve patient outcome from CRPC.

Patient summary
In this study we found that levels of the protein AR-V7 were higher in patients with advanced prostate cancer. A higher level of AR-V7 identifies a group of patients who respond less well to certain prostate cancer treatments and live for a shorter period of time.

The androgen receptor (AR) is a nuclear steroid receptor that binds to testosterone and dihydrotestosterone and regulates the transcription of genes leading to cell growth, differentiation and survival. AR serves as an important oncogenic signal in prostate cancers and apocrine breast cancers. Salivary duct carcinoma (SDC) is a rare subtype of head and neck cancer that is defined by an apocrine phenotype, with AR positivity by immunohistochemistry (IHC) in up to 98% of cases [1]. A recent clinical trial with leuprorelin acetate and bicalutamide has shown promising activity with an overall response rate of 42% in AR-positive salivary gland cancers, but further analyses of clinicopathological factors or biomarkers including AR expression intensity, HER2 expression, EGFR expression and HRAS mutation did not show any significant association with outcomes [2].