Tamara L. Lotan

AR-V7 and Resistance to Enzalutamide and Abiraterone in Prostate Cancer

BACKGROUND The androgen-receptor isoform encoded by splice variant 7 lacks the ligand-binding domain, which is the target of enzalutamide and abiraterone, but remains constitutively active as a transcription factor. We hypothesized that detection of androgen-receptor splice variant 7 messenger RNA (AR-V7) in circulating tumor cells from men with advanced prostate cancer would be associated with resistance to enzalutamide and abiraterone. METHODS We used a quantitative reverse-transcriptase-polymerase-chain-reaction assay to evaluate AR-V7 in circulating tumor cells from prospectively enrolled patients with metastatic castration-resistant prostate cancer who were initiating treatment with either enzalutamide or abiraterone. We examined associations between AR-V7 status (positive vs. negative) and prostate-specific antigen (PSA) response rates (the primary end point), freedom from PSA progression (PSA progression-free survival), clinical or radiographic progression-free survival, and overall survival. RESULTS A total of 31 enzalutamide-treated patients and 31 abiraterone-treated patients were enrolled, of whom 39% and 19%, respectively, had detectable AR-V7 in circulating tumor cells. Among men receiving enzalutamide, AR-V7-positive patients had lower PSA response rates than AR-V7-negative patients (0% vs. 53%, P=0.004) and shorter PSA progression-free survival (median, 1.4 months vs. 6.0 months; P<0.001), clinical or radiographic progression-free survival (median, 2.1 months vs. 6.1 months; P<0.001), and overall survival (median, 5.5 months vs. not reached; P=0.002). Similarly, among men receiving abiraterone, AR-V7-positive patients had lower PSA response rates than AR-V7-negative patients (0% vs. 68%, P=0.004) and shorter PSA progression-free survival (median, 1.3 months vs. not reached; P<0.001), clinical or radiographic progression-free survival (median, 2.3 months vs. not reached; P<0.001), and overall survival (median, 10.6 months vs. not reached, P=0.006). The association between AR-V7 detection and therapeutic resistance was maintained after adjustment for expression of full-length androgen receptor messenger RNA. CONCLUSIONS Detection of AR-V7 in circulating tumor cells from patients with castration-resistant prostate cancer may be associated with resistance to enzalutamide and abiraterone. These findings require large-scale prospective validation. (Funded by the Prostate Cancer Foundation and others.).

Prevalence of the alternative lengthening of telomeres telomere maintenance mechanism in human cancer subtypes

Approximately 10% to 15% of human cancers lack detectable telomerase activity, and a subset of these maintain telomere lengths by the telomerase-independent telomere maintenance mechanism termed alternative lengthening of telomeres (ALT). The ALT phenotype, relatively common in subtypes of sarcomas and astrocytomas, has rarely been reported in epithelial malignancies. However, the prevalence of ALT has not been thoroughly assessed across all cancer types. We therefore comprehensively surveyed the ALT phenotype in a broad range of human cancers. In total, two independent sets comprising 6110 primary tumors from 94 different cancer subtypes, 541 benign neoplasms, and 264 normal tissue samples were assessed by combined telomere-specific fluorescence in situ hybridization and immunofluorescence labeling for PML protein. Overall, ALT was observed in 3.73% (228/6110) of all tumor specimens, but was not observed in benign neoplasms or normal tissues. This is the first report of ALT in carcinomas arising from the bladder, cervix, endometrium, esophagus, gallbladder, kidney, liver, and lung. Additionally, this is the first report of ALT in medulloblastomas, oligodendrogliomas, meningiomas, schwannomas, and pediatric glioblastoma multiformes. Previous studies have shown associations between ALT status and prognosis in some tumor types; thus, further studies are warranted to assess the potential prognostic significance and unique biology of ALT-positive tumors. These findings may have therapeutic consequences, because ALT-positive cancers are predicted to be resistant to anti-telomerase therapies.

PTEN Protein Loss by Immunostaining: Analytic Validation and Prognostic Indicator for a High Risk Surgical Cohort of Prostate Cancer Patients

Purpose: Analytically validated assays to interrogate biomarker status in clinical samples are crucial for personalized medicine. PTEN is a tumor suppressor commonly inactivated in prostate cancer that has been mechanistically linked to disease aggressiveness. Though deletion of PTEN, as detected by cumbersome FISH spot counting assays, is associated with poor prognosis, few studies have validated immunohistochemistry (IHC) assays to determine whether loss of PTEN protein is associated with unfavorable disease. Experimental Design: PTEN IHC was validated by employing formalin fixed and paraffin-embedded isogenic human cell lines containing or lacking intact PTEN alleles. PTEN IHC was 100% sensitive and 97.8% specific for detecting genomic alterations in 58 additional cell lines. PTEN protein loss was then assessed on 376 prostate tumor samples, and PTEN FISH or high resolution single nucleotide polymorphism microarray analysis was done on a subset of these cases. Results: PTEN protein loss, as assessed as a dichotomous IHC variable, was highly reproducible, correlated strongly with adverse pathologic features (e.g., Gleason score and pathologic stage), detected between 75% and 86% of cases with PTEN genomic loss, and was found at times in the absence of apparent genomic loss. In a cohort of 217 high risk surgically treated patients, PTEN protein loss was associated with decreased time to metastasis. Conclusion: These studies validate a simple method to interrogate PTEN status in clinical specimens and support the utility of this test in future multicenter studies, clinical trials, and ultimately perhaps for routine clinical care. Clin Cancer Res; 17(20); 6563–73. ©2011 AACR.

Proposed morphologic classification of prostate cancer with neuroendocrine differentiation.

On July 31, 2013, the Prostate Cancer Foundation assembled a working committee on the molecular biology and pathologic classification of neuroendocrine (NE) differentiation in prostate cancer. New clinical and molecular data emerging from prostate cancers treated by contemporary androgen deprivation therapies, as well as primary lesions, have highlighted the need for refinement of diagnostic terminology to encompass the full spectrum of NE differentiation. The classification system consists of: Usual prostate adenocarcinoma with NE differentiation; 2) Adenocarcinoma with Paneth cell NE differentiation; 3) Carcinoid tumor; 4) Small cell carcinoma; 5) Large cell NE carcinoma; and 5) Mixed NE carcinoma - acinar adenocarcinoma. The article also highlights “prostate carcinoma with overlapping features of small cell carcinoma and acinar adenocarcinoma” and “castrate-resistant prostate cancer with small cell cancer-like clinical presentation”. It is envisioned that specific criteria associated with the refined diagnostic terminology will lead to clinically relevant pathologic diagnoses that will stimulate further clinical and molecular investigation and identification of appropriate targeted therapies.

Botulinum toxin type A inhibits sensory neuropeptide release in rat bladder models of acute injury and chronic inflammation

To determine the effect of botulinum toxin type A (BTX‐A) on the release of the neuropeptides substance P (SP) and calcitonin gene‐related peptide (CGRP) from isolated bladder preparations after acute injury with HCl and the induction of cyclophosphamide (CYP)‐induced cystitis, as neurogenic inflammation has been increasingly identified in urological disorders such as interstitial cystitis.

Rb Loss Is Characteristic of Prostatic Small Cell Neuroendocrine Carcinoma

Purpose: Small cell neuroendocrine carcinoma of the prostate is likely to become increasingly common with recent advances in pharmacologic androgen suppression. Thus, developing molecular markers of small cell differentiation in prostate cancer will be important to guide the diagnosis and therapy of this aggressive tumor. Experimental Design: We examined the status of RB1, TP53, and PTEN in prostatic small cell and acinar carcinomas via immunohistochemistry (IHC), copy-number alteration analysis, and sequencing of formalin-fixed paraffin-embedded specimens. Results: We found retinoblastoma (Rb) protein loss in 90% of small cell carcinoma cases (26 of 29) with RB1 allelic loss in 85% of cases (11 of 13). Of acinar tumors occurring concurrently with prostatic small cell carcinoma, 43% (3 of 7) showed Rb protein loss. In contrast, only 7% of primary high-grade acinar carcinomas (10 of 150), 11% of primary acinar carcinomas with neuroendocrine differentiation (4 of 35), and 15% of metastatic castrate-resistant acinar carcinomas (2 of 13) showed Rb protein loss. Loss of PTEN protein was seen in 63% of small cell carcinomas (17 of 27), with 38% (5 of 13) showing allelic loss. By IHC, accumulation of p53 was observed in 56% of small cell carcinomas (14 of 25), with 60% of cases (6 of 10) showing TP53 mutation. Conclusions: Loss of RB1 by deletion is a common event in prostatic small cell carcinoma and can be detected by a validated IHC assay. As Rb protein loss rarely occurs in high-grade acinar tumors, these data suggest that Rb loss is a critical event in the development of small cell carcinomas and may be a useful diagnostic and potential therapeutic target. Clin Cancer Res; 20(4); 890–903. ©2013 AACR.

ERG gene rearrangements are common in prostatic small cell carcinomas

Small cell carcinoma of the prostate is a rare subtype with an aggressive clinical course. Despite the frequent occurrence of ERG gene rearrangements in acinar carcinoma, the incidence of these rearrangements in prostatic small cell carcinoma is unclear. In addition, molecular markers to distinguish prostatic small cell carcinomas from lung and bladder small cell carcinomas may be clinically useful. We examined the occurrence of ERG gene rearrangements by fluorescence in situ hybridization in prostatic, bladder and lung small cell carcinomas. We also examined the expression of ERG, androgen receptor (AR) and NKX3-1 by immunohistochemistry in prostatic cases. Overall, 45% (10/22) of prostatic small cell carcinoma cases harbored ERG rearrangements, whereas no cases of bladder or lung small cell carcinomas showed ERG rearrangement (0/12 and 0/13, respectively). Of prostatic small cell carcinoma cases, 80% (8/10) showed ERG deletion and 20% (2/10) showed ERG translocation. In 83% (5/6) of prostatic small cell carcinoma cases in which a concurrent conventional prostatic acinar carcinoma component was available for analysis, there was concordance for the presence/absence of ERG gene rearrangement between the different subtypes. ERG, AR and NKX3-1 protein expression was detected in a minority of prostatic small cell carcinoma cases (23, 27 and 18%, respectively), while these markers were positive in the majority of concurrent acinar carcinoma cases (66, 83 and 83%, respectively). The presence of ERG rearrangements in nearly half of the prostatic small cell carcinomas is a similar rate of rearrangement to that found in prostatic acinar carcinomas. Furthermore, the high concordance rate of ERG rearrangement between the small cell and acinar components in a given patient supports a common origin for these two subtypes of prostate cancer. Finally, the absence of ERG rearrangement in bladder or lung small cell carcinomas highlights the utility of detecting ERG rearrangement in small cell carcinomas of unknown primary for establishing prostatic origin.

MYC Overexpression Induces Prostatic Intraepithelial Neoplasia and Loss of Nkx3.1 in Mouse Luminal Epithelial Cells

Lo-MYC and Hi-MYC mice develop prostatic intraepithelial neoplasia (PIN) and prostatic adenocarcinoma as a result of MYC overexpression in the mouse prostate[1]. However, prior studies have not determined precisely when, and in which cell types, MYC is induced. Using immunohistochemistry (IHC) to localize MYC expression in Lo-MYC transgenic mice, we show that morphological and molecular alterations characteristic of high grade PIN arise in luminal epithelial cells as soon as MYC overexpression is detected. These changes include increased nuclear and nucleolar size and large scale chromatin remodeling. Mouse PIN cells retained a columnar architecture and abundant cytoplasm and appeared as either a single layer of neoplastic cells or as pseudo-stratified/multilayered structures with open glandular lumina—features highly analogous to human high grade PIN. Also using IHC, we show that the onset of MYC overexpression and PIN development coincided precisely with decreased expression of the homeodomain transcription factor and tumor suppressor, Nkx3.1. Virtually all normal appearing prostate luminal cells expressed high levels of Nkx3.1, but all cells expressing MYC in PIN lesions showed marked reductions in Nkx3.1, implicating MYC as a key factor that represses Nkx3.1 in PIN lesions. To determine the effects of less pronounced overexpression of MYC we generated a new line of mice expressing MYC in the prostate under the transcriptional control of the mouse Nkx3.1 control region. These “Super-Lo-MYC” mice also developed PIN, albeit a less aggressive form. We also identified a histologically defined intermediate step in the progression of mouse PIN into invasive adenocarcinoma. These lesions are characterized by a loss of cell polarity, multi-layering, and cribriform formation, and by a “paradoxical” increase in Nkx3.1 protein. Similar histopathological changes occurred in Hi-MYC mice, albeit with accelerated kinetics. Our results using IHC provide novel insights that support the contention that MYC overexpression is sufficient to transform prostate luminal epithelial cells into PIN cells in vivo. We also identified a novel histopathologically identifiable intermediate step prior to invasion that should facilitate studies of molecular pathway alterations occurring during early progression of prostatic adenocarcinomas.

Small Endoscopic Biopsies of the Ureter and Renal Pelvis: Pathologic Pitfalls

Technical advances in endoscopic equipment have led to increased ureteroscopic biopsies of the upper urinary tract, resulting in limited biopsy material. We retrospectively reviewed 76 consecutive mid-upper ureter and renal pelvis biopsies submitted for consultation from January 2004 to January 2009, where follow-up was obtainable. There were 49 (64.5%) males and 27 (35.5%) females. Thirty-nine (51.3%) of the biopsies were from the ureter with the remaining 37 (48.7%) from the renal pelvis. The mean age was 70 years for males and 71 for females (range: 24 to 89). At consultation, the most common diagnoses were benign urothelium (n=25, 32.9%); atypical (n=17, 22.4%); low-grade noninvasive papillary urothelial carcinoma (n=10, 13.2%); and high-grade noninvasive papillary urothelial carcinoma (n=8, 10.5%). In cases where a definitive diagnosis could not be reached on expert review, it was mainly because of the limited size of the biopsy, absence of papillary fronds, crush artifact, and distorted architecture. There were 7 major discrepancies between the outside and second opinion diagnosis, where all of the cases were initially diagnosed as an urothelial neoplasm, yet was non-neoplastic upon review. Strips of urothelium without well-developed fibrovascular cores, polypoid ureteritis/pyelitis, and reactive urothelium mimicked urothelial neoplasms. In 5 of these 7 cases, there was no gross lesion suspicious of a tumor present according to the urologist. Overall, 33 of the 44 (75%) cases with a mass noted by the urologist or by radiography was found to have a neoplasm at follow-up. Conversely, 24 of the 32 (75%) cases without a grossly suspected tumor had no neoplasm at follow-up. The association between the histologic presence of a neoplasm at follow-up and the presence of a clinically suspected tumor was highly significant (P<0.0001). Pathologists need to recognize that in almost 1 of the 4 renal pelvic/ureteral biopsies a definitive diagnosis cannot be made because of the inadequate tissue. Caution must be exercised in the evaluation of these limited specimens, especially in the absence of a clinically suspected tumor.

Cytoplasmic PTEN Protein Loss Distinguishes Intraductal Carcinoma of the Prostate from High Grade Prostatic Intraepithelial Neoplasia

Intraductal carcinoma of the prostate is a marker of aggressive disease. However, intraductal carcinoma exists on a morphologic continuum with high-grade prostatic intraepithelial neoplasia (PIN) and distinguishing intraductal carcinoma from PIN is a common diagnostic dilemma with significant clinical implications. We evaluated whether immunostains for PTEN and ERG can sensitively identify intraductal carcinoma and accurately distinguish it from high-grade PIN. A combined immunostain for PTEN, ERG, p63 and CK903 was developed and validated. Radical prostatectomy specimens with lesions meeting criteria for intraductal carcinoma (n=45), intraductal cribriform proliferations falling short of intraductal carcinoma (n=15), and PIN lesions (n=39) were retrospectively identified and assessed for PTEN and ERG. Cytoplasmic PTEN loss was identified in 84% (38/45) of the intraductal carcinoma and 100% (15/15) of intraductal cribriform proliferation cases. In contrast, cytoplasmic PTEN loss was never observed in PIN (0/39; P<0.0001). Of the 53 cases of intraductal carcinoma or intraductal cribriform proliferation with cytoplasmic PTEN loss, it was homogeneously lost in 42 cases (79%). Weak, focal nuclear positivity for PTEN was retained in 31 of these 42 cases (74%). ERG expression was identified in 58% (26/45) of intraductal carcinoma and 67% (10/15) of intraductal cribriform proliferations compared with 13% (5/39) of PIN. Concordance between the PTEN/ERG status of the intraductal carcinoma lesions and the concurrent invasive carcinoma was high (>95% and P<0.0001 for each), and substantially less for PIN and the concurrent invasive tumor (83% for PTEN and 67% for ERG; P=NS for each). Cytoplasmic PTEN loss occurs in the majority of intraductal carcinoma and intraductal cribriform proliferation cases. Cytoplasmic PTEN loss was never observed in PIN (100% specificity). Our study identifies PTEN loss as a potentially useful marker to distinguish intraductal carcinoma from PIN and provides a plausible molecular explanation for why intraductal carcinoma is associated with poor prognosis.