Patient-Derived Xenografts and Organoids Recapitulate Castration-Resistant Prostate Cancer with Sustained Androgen Receptor Signaling

Castration-resistant prostate cancer (CRPC) remains an incurable and lethal malignancy. The development of new CRPC treatment strategies is strongly impeded by the scarcity of representative, scalable and transferable preclinical models of advanced, androgen receptor (AR)-driven CRPC. Here, we present contemporary patient-derived xenografts (PDXs) and matching PDX-derived organoids (PDXOs) from CRPC patients who had undergone multiple lines of treatment. These models were comprehensively profiled at the morphologic, genomic (n = 8) and transcriptomic levels (n = 81). All are high-grade adenocarcinomas that exhibit copy number alterations and transcriptomic features representative of CRPC patient cohorts. We identified losses of PTEN and RB1, MYC amplifications, as well as genomic alterations in TP53 and in members of clinically actionable pathways such as AR, PI3K and DNA repair pathways. Importantly, the clinically observed continued reliance of CRPC tumors on AR signaling is preserved across the entire set of models, with AR amplification identified in four PDXs. We demonstrate that PDXs and PDXOs faithfully reflect donor tumors and mimic matching patient drug responses. In particular, our models predicted patient responses to subsequent treatments and captured sensitivities to previously received therapies. Collectively, these PDX-PDXO pairs constitute a reliable new resource for in-depth studies of treatment-induced, AR-driven resistance mechanisms. Moreover, PDXOs can be leveraged for large-scale tumor-specific drug response profiling critical for accelerating therapeutic advances in CRPC.

Clinical outcome comparison of Grade Group 1 and Grade Group 2 prostate cancer with and without cribriform architecture at the time of radical prostatectomy

Aims

Invasive cribriform and intraductal carcinoma are associated with aggressive disease in Grade Group 2 (GG2) prostate cancer patients. However, the characteristics and clinical outcome of patients with GG2 prostate cancer without cribriform architecture (GG2−) as compared with those with Grade Group 1 (GG1) prostate cancer are unknown. The aim of this study was to investigate the clinical and pathological characteristics of GG1 and GG2− prostate cancer in radical prostatectomy specimens.

Methods and results

We reviewed 835 radical prostatectomy specimens for Grade Group, pT stage, surgical margin status, and the presence of cribriform architecture. Biochemical recurrence‐free survival and metastasis were used as clinical outcomes. GG1 prostate cancer was seen in 207 patients, and GG2 prostate cancer was seen in 420 patients, of whom 228 (54%) showed cribriform architecture (GG2+) and 192 (46%) did not. GG2− patients had higher prostate‐specific antigen levels (9.4 ng/ml versus 7.0 ng/ml; P < 0.001), more often had extraprostatic extension (36% versus 11%; P < 0.001) and had more positive surgical margins (27% versus 17%; P = 0.01) than GG1 patients. GG2− patients had shorter biochemical recurrence‐free survival (hazard ratio 2.7, 95% confidence interval 1.4–4.9; P = 0.002) than GG1 patients. Lymph node and distant metastasis were observed neither in GG2− nor in GG1 patients, but occurred in 22 of 228 (10%) GG2+ patients.

Conclusion

In conclusion, patients with GG2− prostate cancer at radical prostatectomy have more advanced disease and shorter biochemical recurrence‐free survival than those with GG1 prostate cancer, but both groups have a very low risk of developing metastasis.

Cribriform architecture in radical prostatectomies predicts oncological outcome in Gleason score 8 prostate cancer patients

The Gleason score is an important parameter for clinical outcome in prostate cancer patients. Gleason score 8 is a heterogeneous disease including Gleason score 3 + 5, 4 + 4, and 5 + 3 tumors, and encompasses a broad range of tumor growth patterns. Our objective was to characterize individual growth patterns and identify prognostic parameters in Gleason score 8 prostate cancer patients. We reviewed 1064 radical prostatectomy specimens, recorded individual Gleason 4 and 5 growth patterns as well as presence of intraductal carcinoma, and evaluated biochemical recurrence- and metastasis-free survival. Gleason score 8 disease was identified in 140 (13%) patients, of whom 76 (54%) had Gleason score 3 + 5, 46 (33%) 4 + 4, and 18 (13%) 5 + 3 disease. Invasive cribriform and/or intraductal carcinoma (n = 87, 62%) was observed more frequently in Gleason score 4 + 4 (93%) than 3 + 5 (47%; P < 0.001) and 5 + 3 (44%; P < 0.001) patients. Gleason pattern 5 was present in 110 (79%) men: as single cells and/or cords in 99 (90%) and solid fields in 32 (29%) cases. Solid field pattern 5 coexisted with cribriform architecture (23/32, 72%) more frequently than nonsolid pattern 5 cases (36/78, 46%, P = 0.02). In multivariable analysis including age, prostate-specific antigen, pT-stage, surgical margin status, and lymph node metastases, presence of cribriform architecture was an independent parameter for biochemical recurrence-free (hazard ratio (HR) 2.0, 95% confidence interval (CI) 1.0-3.7; P = 0.04) and metastasis-free (HR 3.5, 95% CI 1.0-12.3; P = 0.05) survival. In conclusion, invasive cribriform and/or intraductal carcinoma occurs more frequently in Gleason score 4 + 4 prostate cancer patients than in Gleason score 3 + 5 and 5 + 3, and is an independent parameter for biochemical recurrence and metastasis. Therefore, cribriform architecture has added value in risk stratification of Gleason score 8 prostate cancer patients.

Combined transmission, dark field and fluorescence microscopy for intact, 3D tissue analysis of biopsies

SIGNIFICANCE

Currently, tissue biopsies are sectioned into 3- to 5-μm-thick slices that are used for conventional pathology analysis. Previous work by confocal microscopy and light-sheet microscopy has shown that analyzing biopsies intact in three-dimensions (3D) is possible and may lead to a better understanding of cancer growth patterns. Although accurate, these methods require fluorescent staining of the tissue, in addition to tissue clearing. If the 3D biopsy analysis could be done sufficiently swiftly, this approach may be used for on-site assessment of the adequacy of a biopsy taken.

AIM

We aim to show that, by transmission microscopy of optically cleared tissue punches, the tissue architecture can be determined without the need for fluorescent staining.

APPROACH

Transmission microscopy is used by combining bright field microscopy with dark field and epifluorescent microscopy to compare samples that have also been analyzed by fluorescent confocal microscopy.

RESULTS

With increasing distance to the focal plane, the higher-frequency part of the spatial frequency spectrum of transmitted light is attenuated increasingly. This property is exploited for tissue segmentation, detecting whether tissue is present at a certain position in the focal plane image. Using this approach, we show that a 3D rendering of the internal cavity or tubules structure of punch biopsies, which are up to 1-mm thick, can be acquired in ≈1 min scan time per imaging modality. The images of the overall tissue architecture that are obtained are similar to those from the confocal microscopy benchmark, without requiring fluorescent staining.

CONCLUSIONS

Images of the overall tissue architecture can be obtained from transmission microcopy; they are similar to those from the confocal microscopy benchmark without requiring fluorescent staining. Tissue clearing is still needed. The total scan time of the present method is significantly shorter at a fraction of the device costs.

Prostate cancer growth patterns beyond the Gleason score: entering a new era of comprehensive tumour grading

The Gleason grading system is one of the most important factors in clinical decision‐making for prostate cancer patients, and is entirely based on the classification of tumour growth patterns. In recent years it has become clear that some individual growth patterns themselves have independent prognostic value, and could be used for better personalised risk stratification. In this review we summarise recent literature on the clinicopathological value and molecular characteristics of individual prostate cancer growth patterns, and show how these, most particularly cribriform architecture, could alter treatment decisions for prostate cancer patients.

Comparison of Tumor Volume Parameters on Prostate Cancer Biopsies

CONTEXT.—

Prostate biopsy reports require an indication of prostate cancer volume. No consensus exists on the methodology of tumor volume reporting.

OBJECTIVE.—

To compare the prognostic value of different biopsy prostate cancer volume parameters.

DESIGN.—

Prostate biopsies of the European Randomized Study of Screening for Prostate Cancer were reviewed (n = 1031). Tumor volume was quantified in 6 ways: average estimated tumor percentage, measured total tumor length, average calculated tumor percentage, greatest tumor length, greatest tumor percentage, and average tumor percentage of all biopsies. Their prognostic value was determined by using either logistic regression for extraprostatic expansion (EPE) and surgical margin status after radical prostatectomy (RP), or Cox regression for biochemical recurrence-free survival (BCRFS) and disease-specific survival (DSS) after RP (n = 406) and radiation therapy (RT) (n = 508).

RESULTS.—

All tumor volume parameters were significantly mutually correlated (R2 > 0.500, P < .001). None were predictive for EPE, surgical margin, or BCRFS after RP in multivariable analysis, including age, prostate-specific antigen, number of positive biopsies, and grade group. In contrast, all tumor volume parameters were significant predictors for BCRFS (all P < .05) and DSS (all P < .05) after RT, except greatest tumor length. In multivariable analysis including only all tumor volume parameters as covariates, calculated tumor length was the only predictor for EPE after RP (P = .02) and DSS after RT (P = .02).

CONCLUSIONS.—

All tumor volume parameters had comparable prognostic value and could be used in clinical practice. If tumor volume quantification is a threshold for treatment decision, calculated tumor length seems preferential, slightly outperforming the other parameters.

Improved Prostate Cancer Biopsy Grading by Incorporation of Invasive Cribriform and Intraductal Carcinoma in the 2014 Grade Groups

BACKGROUND

Grade groups (GGs) are an important parameter for therapeutic decision making in prostate cancer (Pca) patients. Invasive cribriform and/or intraductal carcinoma (CR/IDC) has an independent prognostic value for disease outcome, but are not included in the GG limiting their clinical use.

OBJECTIVE

To perform a proof-of-principle study incorporating CR/IDC in the current GG.

DESIGN, SETTING, AND PARTICIPANTS

All prostate biopsies of 1031 men with screen-detected Pca between 1993 and 2000 were reviewed for the current GG (ranging from 1 to 5) and CR/IDC. The cribriform grade (cGrade) was equal to the GG if CR/IDC was present and GG minus 1 if not. GG1 was cGrade1 if intraductal carcinoma was absent.

INTERVENTION

Biopsy review for GG and CR/IDC. A total of 406 patients had received radical prostatectomy (RP), 508 radiotherapy (RT), 108 surveillance, and eight hormonal therapy, and the treatment was unknown for one patient. Outcome measurements and statistical analysis disease-specific survival (DSS), metastasis-free survival (MFS), and biochemical recurrence-free survival (BCRFS) after 15.1 yr (interquartile range 10.9-19.7 yr) follow-up were compared using Harrell's C-statistic.

RESULTS AND LIMITATIONS

The biopsy GGs were 486 GG1, 310 GG2, 104 GG3, 64 GG4, and 67 GG5; cGrade distributions were 738 cGrade1, 102 cGrade2, 91 cGrade3, 58 cGrade4, and 42 cGrade5. The cGrade had a better discriminative value than the GG for DSS (C-index 0.79; 95% confidence interval 0.74-0.83 vs 0.76; 0.71-0.82) and MFS (0.79; 0.74-0.84 vs 0.77; 0.72-0.82). The discriminative value for BCRFS after RP and RT was similar for both models. Different diagnostic, such as use of sextant biopsies, and therapeutic strategies in the 1990s are the limitations of this study.

CONCLUSIONS

The cGrade is a simple Pca grade modification with better discriminative values for DSS and MFS than the GG, particularly impacting decision making in men with current GG2 Pca.

PATIENT SUMMARY

Microscopic grading is an important factor for decision making in prostate cancer (Pca) patients. We show that a simple grade modification better predicts Pca outcome and might improve treatment choices.

Concordance of cribriform architecture in matched prostate cancer biopsy and radical prostatectomy specimens

Aims

Invasive cribriform and/or intraductal carcinoma have been identified as independent adverse parameters for prostate cancer outcome. Little is known on biopsy undersampling of cribriform architecture. Our aim was to determine the extent of cribriform architecture undersampling and to find predictive factors for identifying false cribriform‐negative cases.

Methods and results

We reviewed 186 matched prostate biopsies and radical prostatectomy specimens. Of 97 biopsy grade group 2 (Gleason score 3 + 4 = 7) patients, 22 (23%) had true cribriform‐negative (TN), 39 (40%) false‐negative (FN) and 36 (37%) true‐positive (TP) biopsies. Patients with FN biopsies had higher, although not statistically significant (P = 0.06), median PSA levels than patients with TP biopsies (12 versus 8 ng/ml). A PI‐RADS 5 lesion was present in nine of 16 (54%) FN and three of 11 (27%) TN biopsies (P = 0.05). Positive biopsy rate (P = 0.47), percentage Gleason pattern 4 (P = 0.55) and glomeruloid architecture (P = 1.0) were not different. Logistic regression identified PSA as an independent predictor (odds ratio = 3.5; 95% confidence interval = 1.2–9.4, P = 0.02) for cribriform architecture on radical prostatectomy, but not PI‐RADS score. The FN rate for large cribriform architecture at radical prostatectomy was 27%, which was lower than for any cribriform architecture (P = 0.01). During follow‐up (median 27 months), biochemical recurrence‐free survival of patients with TP biopsies was significantly shorter than that of those with FN biopsies (P = 0.03).

Conclusion

In conclusion, 40% of grade group 2 prostate cancer biopsies were FN for cribriform architecture. These patients had higher PSA levels and more frequent PI‐RADS score 5 lesions than men with TN biopsies.

Differential tissue expression of extracellular vesicle-derived proteins in prostate cancer

BACKGROUND

Proteomic profiling of extracellular vesicles (EVs) from prostate cancer (PCa) and normal prostate cell lines, led to the identification of new candidate PCa markers. These proteins included the nuclear exportin proteins XPO1 (also known as CRM1), the EV-associated PDCD6IP (also known as ALIX), and the previously published fatty acid synthase FASN. In this study, we investigated differences in expression of XPO1 and PDCD6IP on well-characterized prostate cancer cohorts using mass spectrometry and tissue microarray (TMA) immunohistochemistry to determine their diagnostic and prognostic value.

METHODS

Protein fractions from 67 tissue samples (n = 33 normal adjacent prostate [NAP] and n = 34 PCa) were analyzed by mass spectrometry (nano-LC-MS-MS). Label-free quantification of EVs was performed to identify differentially expressed proteins between PCa and NAP. Prognostic evaluation of the candidate markers was performed with a TMA, containing 481 radical prostatectomy samples. Samples were stained for the candidate markers and correlated with patient information and clinicopathological outcome.

RESULTS

XPO1 was higher expressed in PCa compared to NAP in the MS data analysis (P > 0.0001). PDCD6IP was not significantly higher expressed (P = 0.0501). High cytoplasmic XPO1 staining in the TMA immunohistochemistry, correlated in a multivariable model with high Gleason scores (P = 0.002) and PCa-related death (P = 0.009).

CONCLUSION

High expression of cytoplasmic XPO1 shows correlation with prostate cancer and has added clinical value in tissue samples. Furthermore, as an extracellular vesicles-associated protein, it might be a novel relevant liquid biomarker.

PIK3CA mutations in ductal carcinoma in situ and adjacent invasive breast cancer

PIK3CA is one of the most frequently mutated genes in invasive breast cancer (IBC). These mutations are generally associated with hyper-activation of the phosphatidylinositol 3-kinase signaling pathway, which involves increased phosphorylation of AKT (p-AKT). This pathway is negatively regulated by the tumor suppressor PTEN. Data are limited regarding the variant allele frequency (VAF) of PIK3CA, PTEN and p-AKT expression during various stages of breast carcinogenesis. Therefore, the aim of this study was to gain insight into PIK3CA VAF and associated PTEN and p-AKT expression during the progression from ductal carcinoma in situ (DCIS) to IBC. We isolated DNA from DCIS tissue, synchronous IBC and metastasis when present. These samples were pre-screened for PIK3CA hotspot mutations using the SNaPshot assay and, if positive, validated and quantified by digital PCR. PTEN and p-AKT expression was evaluated by immunohistochemistry using the Histo-score (H-score). Differences in PIK3CA VAF, PTEN and p-AKT H-scores between DCIS and IBC were analyzed. PIK3CA mutations were detected in 17 out of 73 DCIS samples, 16 out of 73 IBC samples and 3 out of 23 lymph node metastasis. We detected a significantly higher VAF of PIK3CA in the DCIS component compared to the adjacent IBC component (P = 0.007). The expression of PTEN was significantly higher in DCIS compared to the IBC component in cases with a wild-type (WT) PIK3CA status (P = 0.007), while it remained similar in both components when PIK3CA was mutated. There was no difference in p-AKT expression between DCIS and the IBC component. In conclusion, our data suggest that PIK3CA mutations could be essential specifically in early stages of breast carcinogenesis. In addition, these mutations do not co-occur with PTEN expression during DCIS progression to IBC in the majority of patients. These results may contribute to further unraveling the process of breast carcinogenesis, and this could aid in the development of patient-specific treatment.

Three-dimensional architecture of common benign and precancerous prostate epithelial lesions

Aims

Many glandular lesions can mimic prostate cancer microscopically, including atrophic glands, adenosis and prostatic intraepithelial neoplasia. While the characteristic histopathological and immunohistochemical features of these lesions have been well established, little is known about their three‐dimensional architecture. Our objective was to evaluate the three‐dimensional organisation of common prostate epithelial lesions.

Methods and results

500 μm‐thick punches (n = 42) were taken from radical prostatectomy specimens, and stained with antibodies targeting keratin 8–18 and keratin 5 for identification of luminal and basal cells, respectively. Tissue samples were optically cleared in benzyl alcohol:benzyl benzoate and imaged using a confocal laser scanning microscope. The three‐dimensional architecture of peripheral and transition zone glands was acinar, composed of interconnecting and blind‐ending saccular tubules. In simple atrophy, partial atrophy and post‐atrophic hyperplasia, the acinar structure was attenuated with branching blind‐ending tubules from parental tubular structures. Three‐dimensional imaging revealed a novel variant of prostate atrophy characterised by large Golgi‐like atrophic spaces parallel to the prostate surface, which were represented by thin, elongated tubular structures on haematoxylin and eosin (H&E) slides. Conversely, adenosis lacked acinar organisation, so that it closely mimicked low‐grade prostate cancer. High‐grade prostatic intraepithelial neoplasia displayed prominent papillary intraluminal protrusions but retained an acinar organisation, whereas intraductal carcinoma predominantly consisted of cribriform proliferations with either spheroid, ellipsoid or complex interconnecting lumens.

Conclusions

While various prostate epithelial lesions might mimic malignancy on H&E slides, their three‐dimensional architecture is acinar and clearly different from the tubular structure of prostate cancer, with adenosis as an exception.

Three-dimensional analysis reveals two major architectural subgroups of prostate cancer growth patterns

The Gleason score is one of the most important parameters for therapeutic decision-making in prostate cancer patients. Gleason growth patterns are defined by their histological features on 4- to 5-µm cross sections, and little is known about their three-dimensional architecture. Our objective was to characterize the three-dimensional architecture of prostate cancer growth patterns. Intact tissue punches (n = 46) of representative Gleason growth patterns from radical prostatectomy specimens were fluorescently stained with antibodies targeting Keratin 8/18 and Keratin 5 for the detection of luminal and basal epithelial cells, respectively. Punches were optically cleared in benzyl alcohol-benzyl benzoate and imaged using a confocal laser scanning microscope up to a depth of 500 µm. Gleason pattern 3, poorly formed pattern 4, and cords pattern 5 all formed a continuum of interconnecting tubules in which the diameter of the structures and the lumen size decreased with higher grades. In fused pattern 4, the interconnections between the tubules were markedly closer together. In these patterns, all tumor cells were in direct contact with the surrounding stroma. In contrast, cribriform Gleason pattern 4 and solid pattern 5 demonstrated a three-dimensional continuum of contiguous tumor cells, in which the vast majority of cells had no contact with the surrounding stroma. Transitions between cribriform pattern 4 and solid pattern 5 were seen. There was a decrease in the number and size of intercellular lumens from cribriform to solid growth pattern. Glomeruloid pattern 4 formed an intermediate structure consisting of a tubular network with intraluminal epithelial protrusions close to the tubule splitting points. In conclusion, three-dimensional microscopy revealed two major architectural subgroups of prostate cancer growth patterns: (1) a tubular interconnecting network including Gleason pattern 3, poorly formed and fused Gleason pattern 4, and cords Gleason pattern 5, and (2) serpentine contiguous epithelial proliferations including cribriform Gleason pattern 4 and solid Gleason pattern 5.

Large cribriform growth pattern identifies ISUP grade 2 prostate cancer at high risk for recurrence and metastasis

Invasive cribriform and intraductal carcinoma are associated with adverse clinical outcome in patients with Gleason score 7 prostate cancer. It is yet unclear whether invasive cribriform and intraductal carcinoma of the prostate both have independent prognostic value, or whether field size of invasive cribriform carcinoma has impact on disease outcome. Our objective was to determine the prognostic impact of intraductal and invasive cribriform prostate cancer histological subtypes in radical prostatectomies. We reviewed 420 prostatectomy specimens with ISUP grade 2 prostate cancer, assessed the percentages of Gleason grade 4 and tertiary 5, and performed immunohistochemistry for basal cells to discriminate intraductal from invasive cribriform growth. Small and large invasive cribriform fields were distinguished based on a diameter of at least twice the size of adjacent pre-existent normal glands. Clinicopathological parameters and biochemical recurrence-free survival were used as endpoints. Cribriform architecture was observed in 228 (54.3%) men, 103 (24.5%) of whom had intraductal, 194 (46.2%) small invasive, and 34 (8.1%) large invasive cribriform growth. Large invasive cribriform architecture was associated with older age (P < 0.001), higher percentage Gleason grade 4 (P = 0.001), extraprostatic expansion (P < 0.001), and more frequent lymph node metastases (P = 0.002), when compared with small invasive cribriform and/or intraductal carcinoma. Univariate analysis identified PSA, pT-stage, surgical margin status, and intraductal and invasive cribriform growth as significant predictors for biochemical recurrence-free survival. In multivariable Cox regression analysis, pT-stage (hazard ratio = 1.64, 95% CI: 1.02-2.63, P = 0.04), positive surgical margins (hazard ratio = 3.28, 95% CI: 2.06-5.23, P < 0.001), and large cribriform growth (hazard ratio = 4.36, 95% CI: 2.08-9.17, P < 0.001) were independent predictors for biochemical recurrence-free survival, while intraductal carcinoma, small cribriform growth, and percentage of Gleason grade 4 were not. In conclusion, large cribriform fields represent an aggressive subpattern of invasive cribriform prostate cancer and are an independent predictive factor for biochemical recurrence-free survival in ISUP grade 2 prostate cancer patients.

Tissue proteomics outlines AGR2 AND LOX5 as markers for biochemical recurrence of prostate cancer

Although many patients are cured from prostate cancer (PCa) by surgery only, there are still patients who will experience rising prostate-specific antigen (PSA) levels after surgery, a condition known as biochemical recurrence (BCR). Novel protein prognostic markers in PCa tissue might enable finding better treatment for those patients experiencing BCR with a high chance of metastasis. In this study, we aimed to identify altered proteins in prostate cancer tissue, and to evaluate their potential role as prognostic markers. We used two proteomics strategies to analyse 34 prostate tumours (PCa) and 33 normal adjacent prostate (NAP) tissues. An independent cohort of 481 samples was used to evaluate the expression of three proteins: AGR2, FASN and LOX5 as prognostic markers of the disease. Tissue microarray immunohistochemical staining indicated that a low percentage of positive tumour cells for AGR2 (HR (95% CI) = 0.61 (0.43-0.93)), and a low percentage of positive tumour cells for LOX5 expression (HR (95% CI) = 2.53 (1.23-5.22)) are predictors of BCR after RP. In contrast, FASN expression had no prognostic value for PCa.

Epithelial-Mesenchymal Transition in Human Prostate Cancer Demonstrates Enhanced Immune Evasion Marked by IDO1 Expression

Cancer invasion and metastasis are driven by epithelial-mesenchymal transition (EMT), yet the exact mechanisms that account for EMT in clinical prostate cancer are not fully understood. Expression of N-cadherin is considered a hallmark of EMT in clinical prostate cancer. In this study, we determined the molecular mechanisms associated with N-cadherin expression in patients with prostate cancer. We performed laser capture microdissection of matched N-cadherin-positive and -negative prostate cancer areas from patient samples (n = 8), followed by RNA sequencing. N-cadherin expression was significantly associated with an immune-regulatory signature including profound upregulation of indoleamine 2,3-dioxygenase (IDO1; log₂-fold change = 5.1; P = 2.98E-04). Fluorescent immunostainings of patient samples confirmed expression of IDO1 protein and also its metabolite kynurenine in primarily N-cadherin-positive areas. N-cadherin-positive areas also exhibited a local decrease of intraepithelial cytotoxic (CD8⁺) T cells and an increase of immunosuppressive regulatory T cells (CD4⁺/FOXP3⁺). In conclusion, EMT in clinical prostate cancer is accompanied by upregulated expression of IDO1 and an increased number of regulatory T cells. These data indicate that EMT, which is an important step in tumor progression, can be protected from effective immune control in patients with prostate cancer.Significance: These findings demonstrate EMT is linked to an immunosuppressive environment in clinical prostate cancer, suggesting that patients with prostate cancer can potentially benefit from combinatorial drug therapy. Cancer Res; 78(16); 4671-9. ©2018 AACR.

Human PDE4D isoform composition is deregulated in primary prostate cancer and indicative for disease progression and development of distant metastases

Phosphodiesterase 4D7 was recently shown to be specifically over-expressed in localized prostate cancer, raising the question as to which regulatory mechanisms are involved and whether other isoforms of this gene family (PDE4D) are affected under the same conditions.We investigated PDE4D isoform composition in prostatic tissues using a total of seven independent expression datasets and also included data on DNA methylation, copy number and AR and ERG binding in PDE4D promoters to gain insight into their effect on PDE4D transcription.We show that expression of PDE4D isoforms is consistently altered in primary human prostate cancer compared to benign tissue, with PDE4D7 being up-regulated while PDE4D5 and PDE4D9 are down-regulated. Disease progression is marked by an overall down-regulation of long PDE4D isoforms, while short isoforms (PDE4D1/2) appear to be relatively unaffected. While these alterations seem to be independent of copy number alterations in the PDE4D locus and driven by AR and ERG binding, we also observed increased DNA methylation in the promoter region of PDE4D5, indicating a long lasting alteration of the isoform composition in prostate cancer tissues.We propose two independent metrics that may serve as diagnostic and prognostic markers for prostate disease: (PDE4D7 - PDE4D5) provides an effective means for distinguishing PCa from normal adjacent prostate, whereas PDE4D1/2 - (PDE4D5 + PDE4D7 + PDE4D9) offers strong prognostic potential to detect aggressive forms of PCa and is associated with metastasis free survival. Overall, our findings highlight the relevance of PDE4D as prostate cancer biomarker and potential drug target.

MET expression during prostate cancer progression

Tyrosine-kinase inhibitors of the hepatocyte growth factor receptor MET are under investigation for the treatment of hormone-refractory prostate cancer (HRPC) metastasis. Analysis of MET protein expression and genetic alterations might contribute to therapeutic stratification of prostate cancer patients. Our objective was to investigate MET on protein, DNA and RNA level in clinical prostate cancer at various stages of progression.

Expression of MET was analyzed in hormone-naive primary prostate cancers (N=481), lymph node (N=40) and bone (N=8) metastases, as well as HRPC (N=54) and bone metastases (N=15). MET protein expression was analyzed by immunohistochemistry (D1C2 C-terminal antibody). MET mRNA levels and MET DNA copy numbers were determined by in situ hybridization.

None of the hormone-naive primary prostate cancer or lymph node metastases demonstrated MET protein or mRNA expression. In contrast, MET protein was expressed in 12/52 (23%) evaluable HRPC resections. RNA in situ demonstrated cytoplasmic signals in 14/54 (26%) of the HRPC patients, and was associated with MET protein expression (p=0.025, χ²), in absence of MET amplification or polysomy. MET protein expression was present in 7/8 (88%) hormone-naive and 10/15 (67%) HRPC bone metastases, without association of HRPC (p=0.37; χ²), with MET polysomy in 8/13 (61%) evaluable cases.

In conclusion, MET was almost exclusively expressed in HRPC and prostate cancer bone metastasis, but was not related to MET amplification or polysomy. Evaluation of MET status could be relevant for therapeutic stratification of late stage prostate cancer.

Morphological and immunohistochemical identification of epithelial-to-mesenchymal transition in clinical prostate cancer

Epithelial-to-mesenchymal transition (EMT) is a process known to be associated with aggressive tumor behavior, metastasis and treatment resistance. It is characterized by coincidental upregulation of mesenchymal markers such as vimentin, fibronectin and N-cadherin concurrent with E-cadherin downregulation. Studies on EMT are generally performed in cell lines and mouse models, while the histopathological and phenotypical properties in clinical prostate cancer (PCa) are still unclear.

The objective of this study was to identify EMT in PCa patients. We demonstrated that N-cadherin, vimentin and fibronectin were generally not co-expressed in corresponding tumor regions. Immunofluorescent double stainings confirmed that co-expression of mesenchymal markers was uncommon, as we found no prostate cancer cells that co-expressed N-cadherin with fibronectin and only rare (<1%) cells that co-expressed N-cadherin with vimentin. Downregulation of E-cadherin was demonstrated in all N-cadherin positive tumor cells, but not in vimentin or fibronectin positive tumor cells. We further analyzed N-cadherin expression in morphologically distinct PCa growth patterns in a radical prostatectomy cohort (n = 77) and found that N-cadherin is preferentially expressed in ill-defined Gleason grade 4 PCa. In conclusion, we demonstrate that N-cadherin is the most reliable marker for EMT in clinical PCa and is preferentially expressed in ill-defined Gleason grade 4 growth pattern.

Abstract 1590: N-cadherin is a key marker for epithelial-to-mesenchymal transition in clinical prostate cancer

Purpose of the study: Epithelial-to-mesenchymal transition (EMT) is characterized by E cadherin downregulation and simultaneous upregulation of mesenchymal markers such as vimentin, fibronectin and N cadherin. Studies on EMT are generally performed in cell lines and mouse models, while the histopathological and phenotypical properties in clinical prostate cancer (PCa) are still unclear. Our objective was to analyze the expression of various EMT markers in clinical PCa samples.

Experimental procedures: We performed immunofluorescent double stainings with E cadherin and the mesenchymal markers N cadherin, vimentin or fibronectin, Zeb1, Twist1, and β catenin on fresh frozen radical prostatectomies.

Summary: Immunofluorescent double stainings with E cadherin and the mesenchymal markers N cadherin, vimentin or fibronectin demonstrate that E cadherin was consistently downregulated in N cadherin positive PCa cells, but not vimentin or fibronectin positive PCa cells. Moreover, co expression of mesenchymal markers was uncommon, as PCa cells did not co express N-cadherin with fibronectin and only rarely (&lt;1%) cells with vimentin. Membranous expression of β-catenin was unaltered in N cadherin positive PCa cells, while nuclear staining could not detected. Zeb1 was expressed in the nuclei of surrounding fibroblasts, but not in PCa cells. Twist1 was localized to the nucleus of some N-cadherin negative PCa cells, but not in N-cadherin positive cells.

Conclusions: We demonstrated that N cadherin was the most reliable marker for EMT in clinical PCa as compared to vimentin and fibronectin, and that these mesenchymal markers were generally not expressed within the same cell population. The expression of N-cadherin was not associated with Twist1, Zeb1 or β-catenin expression. Despite extensive knowledge of EMT in PCa cell lines, the molecular mechanisms involved in EMT in clinical PCa is still unknown.

Citation Format: Kimberley Kolijn, Esther I. Verhoef, Geert J.L.H. van Leenders. N-cadherin is a key marker for epithelial-to-mesenchymal transition in clinical prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1590.

Disease-specific survival of patients with invasive cribriform and intraductal prostate cancer at diagnostic biopsy

Invasive cribriform and intraductal carcinoma in radical prostatectomy specimens have been associated with an adverse clinical outcome. Our objective was to determine the prognostic value of invasive cribriform and intraductal carcinoma in pre-treatment biopsies on time to disease-specific death. We pathologically revised the diagnostic biopsies of 1031 patients from the first screening round of the European Randomized Study of Screening for Prostate Cancer (1993-2000). Ninety percent of all patients (n=923) had received active treatment, whereas 10% (n=108) had been followed by watchful waiting. The median follow-up was 13 years. Patients who either had invasive cribriform growth pattern or intraductal carcinoma were categorized as CR/IDC+. The outcome was disease-specific survival. Relationships with outcome were analyzed using multivariable Cox regression and log-rank analysis. In total, 486 patients had Gleason score 6 (47%) and 545 had ≥7 (53%). The 15-year disease-specific-survival probabilities were 99% in Gleason score 6 (n=486), 94% in CR/IDC- Gleason score ≥7 (n=356) and 67% in CR/IDC+ Gleason score ≥7 (n=189). CR/IDC- Gleason score 3+4=7 patients did not have statistically different survival probabilities from those with Gleason score 6 (P=0.30), while CR/IDC+ Gleason score 3+4=7 patients did (P<0.001). In multivariable analysis, CR/IDC+ status was independently associated with a poorer disease-specific survival (HR 2.6, 95% CI 1.4-4.8, P=0.002). We conclude that CR/IDC+ status in prostate cancer biopsies is associated with a worse disease-specific survival. Our findings indicate that men with biopsy CR/IDC- Gleason score 3+4=7 prostate cancer could be candidates for active surveillance, as these patients have similar survival probabilities to those with Gleason score 6.

Novel long non-coding RNAs are specific diagnostic and prognostic markers for prostate cancer

Current prostate cancer (PCa) biomarkers such as PSA are not optimal in distinguishing cancer from benign prostate diseases and predicting disease outcome. To discover additional biomarkers, we investigated PCa-specific expression of novel unannotated transcripts. Using the unique probe design of Affymetrix Human Exon Arrays, we identified 334 candidates (EPCATs), of which 15 were validated by RT-PCR. Combined into a diagnostic panel, 11 EPCATs classified 80% of PCa samples correctly, while maintaining 100% specificity. High specificity was confirmed by in situ hybridization for EPCAT4R966 and EPCAT2F176 (SChLAP1) on extensive tissue microarrays. Besides being diagnostic, EPCAT2F176 and EPCAT4R966 showed significant association with pT-stage and were present in PIN lesions. We also found EPCAT2F176 and EPCAT2R709 to be associated with development of metastases and PCa-related death, and EPCAT2F176 to be enriched in lymph node metastases. Functional significance of expression of 9 EPCATs was investigated by siRNA transfection, revealing that knockdown of 5 different EPCATs impaired growth of LNCaP and 22RV1 PCa cells. Only the minority of EPCATs appear to be controlled by androgen receptor or ERG. Although the underlying transcriptional regulation is not fully understood, the novel PCa-associated transcripts are new diagnostic and prognostic markers with functional relevance to prostate cancer growth.

SYK is a candidate kinase target for the treatment of advanced prostate cancer

Improved targeted therapies are needed to combat metastatic prostate cancer. Here, we report the identification of the spleen kinase SYK as a mediator of metastatic dissemination in zebrafish and mouse xenograft models of human prostate cancer. Although SYK has not been implicated previously in this disease, we found that its expression is upregulated in human prostate cancers and associated with malignant progression. RNAi-mediated silencing prevented invasive outgrowth in vitro and bone colonization in vivo, effects that were reversed by wild-type but not kinase-dead SYK expression. In the absence of SYK expression, cell surface levels of the progression-associated adhesion receptors integrin α2β1 and CD44 were diminished. RNAi-mediated silencing of α2β1 phenocopied SYK depletion in vitro and in vivo, suggesting an effector role for α2β1 in this setting. Notably, pharmacologic inhibitors of SYK kinase currently in phase I-II trials for other indications interfered similarly with the invasive growth and dissemination of prostate cancer cells. Our findings offer a mechanistic rationale to reposition SYK kinase inhibitors for evaluation in patients with metastatic prostate cancer.

Validation of stem cell markers in clinical prostate cancer: α6-integrin is predictive for non-aggressive disease

BACKGROUND

Stem cells are postulated to mediate prostate cancer progression, and represent a small fraction of the entire tumor. Various proteins (α2-integrin, α6-integrin, CD117, CD133, EZH2, OCT3/4) are associated with a prostate cancer stem cell phenotype in cell lines and xenografts. Our objective was to investigate expression of stem cell markers in clinical prostate cancer in relation to outcome.

METHODS

We validated immunohistochemical expression of stem cell markers in 481 prostate cancer patients and correlated expression with clinicopathologic parameters.

RESULTS

Sporadic expression of α2-integrin was present in a fraction of tumor cells (<5%) in 94.7% of tumors and associated with PSA > 10 ng/ml (P = 0.04). α6-Integrin expression (<5%) occurred in 28.4% patients, while ≥5% α6-integrin expression was associated with PSA≤10 ng/ml (P = 0.01), Gleason score <7 (P < 0.01) and pT2-disease (P = 0.02). α6-integrin was predictive for biochemical recurrence (P < 0.01), local recurrence (P = 0.03) and disease specific death (P = 0.03). EZH2 expression was generally low with 2.6% of tumors showing ≥1% positive cells. EZH2 was associated with Gleason score ≥7 (P = 0.01) and biochemical recurrence (P = 0.01). We did not identify expression of CD117, CD133, and OCT3/4 in prostate cancer samples.

CONCLUSIONS

Expression of α2-integrin and EZH2 in a small fraction of prostate cancer cells is supportive for their role as stem cell marker. Although α6-integrin was not a unique stem cell marker, it was predictive for prostate cancer biochemical and local recurrence, and disease specific death. The validity of CD117, CD133, and OCT3/4 as prostate cancer stem cell marker is questionable since these proteins were not expressed in clinical prostate cancer.