Development of a multigenomic liquid biopsy (PROSTest) for prostate cancer in whole blood

INTRODUCTION

We describe the development of a molecular assay from publicly available tumor tissue mRNA databases using machine learning and present preliminary evidence of functionality as a diagnostic and monitoring tool for prostate cancer (PCa) in whole blood.

MATERIALS AND METHODS

We assessed 1055 PCas (public microarray data sets) to identify putative mRNA biomarkers. Specificity was confirmed against 32 different solid and hematological cancers from The Cancer Genome Atlas (n = 10,990). This defined a 27-gene panel which was validated by qPCR in 50 histologically confirmed PCa surgical specimens and matched blood. An ensemble classifier (Random Forest, Support Vector Machines, XGBoost) was trained in age-matched PCas (n = 294), and in 72 controls and 64 BPH. Classifier performance was validated in two independent sets (n = 263 PCas; n = 99 controls). We assessed the panel as a postoperative disease monitor in a radical prostatectomy cohort (RPC: n = 47).

RESULTS

A PCa-specific 27-gene panel was identified. Matched blood and tumor gene expression levels were concordant (r = 0.72, p < 0.0001). The ensemble classifier ("PROSTest") was scaled 0%-100% and the industry-standard operating point of ≥50% used to define a PCa. Using this, the PROSTest exhibited an 85% sensitivity and 95% specificity for PCa versus controls. In two independent sets, the metrics were 92%-95% sensitivity and 100% specificity. In the RPCs (n = 47), PROSTest scores decreased from 72% ± 7% to 33% ± 16% (p < 0.0001, Mann-Whitney test). PROSTest was 26% ± 8% in 37 with normal postoperative PSA levels (<0.1 ng/mL). In 10 with elevated postoperative PSA, PROSTest was 60% ± 4%.

CONCLUSION

A 27-gene whole blood signature for PCa is concordant with tissue mRNA levels. Measuring blood expression provides a minimally invasive genomic tool that may facilitate prostate cancer management.

Establishment of primary prostate epithelial and tumorigenic cell lines using a non-viral immortalization approach

BACKGROUND

Research on prostate cancer is mostly performed using cell lines derived from metastatic disease, not reflecting stages of tumor initiation or early progression. Establishment of cancer cell lines derived from the primary tumor site has not been described so far. By definition, cancer cells are able to be cultured indefinitely, whereas normal epithelial cells undergo senescence in vitro. Epithelial cells can be immortalized, accomplished by using viral integration of immortalization factors. Viral approaches, however, might be impaired by regulatory and safety issues as well as random integration into regulatory genetic elements, modifying precise gene expression. We intend to use surgical specimen of prostate cancer patients to (i) prove for establishment of cancer cell lines, and (ii) perform non-viral, Sleeping Beauty (SB) transposase-based immortalization of prostate epithelial cells.

METHODS

Radical prostatectomy samples of prostate cancer patients (n = 4) were dissociated and cultured in vitro. Cells were cultivated either without or after non-viral, Sleeping-Beauty transposase-based stable transfection with immortalization factors SV40LT and hTERT. Established cell lines were analyzed in vitro and in vivo for characteristics of prostate (cancer) cells.

RESULTS

Initial cell cultures without genetic manipulation underwent senescence within ≤ 15 passages, demonstrating inability to successfully derive primary prostate cancer cell lines. By using SB transposase-based integration of immortalization factors, we were able to establish primary prostate cell lines. Three out of four cell lines displayed epithelial characteristics, however without expression of prostate (cancer) characteristics, e.g., androgen receptor. In vivo, one cell line exhibited tumorigenic potential, yet characteristics of prostate adenocarcinoma were absent.

CONCLUSION

Whereas no primary prostate cancer cell line could be established, we provide for the first-time immortalization of primary prostate cells using the SB transposase system, thereby preventing regulatory and molecular issues based on viral immortalization approaches. Although, none of the newly derived cell lines demonstrated prostate cancer characteristics, tumor formation was observed in one cell line. Given the non-prostate adenocarcinoma properties of the tumor, cells have presumably undergone oncogenic transformation rather than prostate cancer differentiation. Still, these cell lines might be used as a tool for research on prostate cancer initiation and early cancer progression.

New advances of the androgen receptor in prostate cancer: report from the 1st International Androgen Receptor Symposium

The androgen receptor (AR) is a crucial player in various aspects of male reproduction and has been associated with the development and progression of prostate cancer (PCa). Therefore, the protein is the linchpin of current PCa therapies. Despite great research efforts, the AR signaling pathway has still not been deciphered, and the emergence of resistance is still the biggest problem in PCa treatment. To discuss the latest developments in AR research, the "1st International Androgen Receptor Symposium" offered a forum for the exchange of clinical and scientific innovations around the role of the AR in prostate cancer (PCa) and to stimulate new collaborative interactions among leading scientists from basic, translational, and clinical research. The symposium included three sessions covering preclinical studies, prognostic and diagnostic biomarkers, and ongoing prostate cancer clinical trials. In addition, a panel discussion about the future direction of androgen deprivation therapy and anti-AR therapy in PCa was conducted. Therefore, the newest insights and developments in therapeutic strategies and biomarkers are discussed in this report.

Immunohistochemical expression of TROP‑2 (TACSTD2) on the urothelial carcinoma of the urinary bladder and other types of cancer

In metastatic or locally advanced urothelial carcinoma (UC), therapeutic options have been limited to chemotherapy and immune checkpoint inhibitors. Novel targets and drugs such as antibody drug conjugates have been developed, and enfortumab vedotin targeting nectin-4 and sacituzumab govitecan (SG) targeting trophoblast cell surface antigen 2 (TROP-2), the protein product of the TACSTD2 gene, have been approved. The expression of TROP-2 was investigated within UC and other types of carcinomas, and within the tissue of different healthy organs to understand treatment responses and toxicities. The expression of TROP-2 in the tissues of 42 patients with UC, 13 patients with other types of cancer and in the normal tissues of 11 patients was retrospectively analyzed. Immunohistochemical staining of the TROP-2 protein was performed on a BenchMark ULTRA IHC/ISH System (Roche Tissue Diagnostics; Roche Diagnostics, Ltd.) according to accredited staining protocols in a routine immunohistochemistry accredited and certified facility of the laboratory of immunohistochemistry at the Institute of Pathology (Gerhard-Domagk Institute)- University Hospital Muenster (UKM)-Muenster-Germany]. Different expression levels of TROP-2 were observed, and the highest expression rate of TROP-2 was observed in UC, independent of the tumor stage. However, normal urothelial cells had similar expression levels. Except for ductal carcinoma in situ, the expression of TROP-2 was reduced in other types of cancer and in the healthy tissues from other organs, including pancreas, gall bladder, colon and prostate. Given the treatment response based on the expression level of TROP-2, SG would be effective in almost all cases of UC. However, it would also have an effect on the normal urothelium.

Co-expression and clinical utility of AR-FL and AR splice variants AR-V3, AR-V7 and AR-V9 in prostate cancer

BACKGROUND

Androgen receptor (AR) splice variants (AR-Vs) have been discussed as a biomarker in prostate cancer (PC). However, some reports question the predictive property of AR-Vs. From a mechanistic perspective, the connection between AR full length (AR-FL) and AR-Vs is not fully understood. Here, we aimed to investigate the dependence of AR-FL and AR-V expression levels on AR gene activity. Additionally, we intended to comprehensively analyze presence of AR-FL and three clinically relevant AR-Vs (AR-V3, AR-V7 and AR-V9) in different stages of disease, especially with respect to clinical utility in PC patients undergoing AR targeted agent (ARTA) treatment.

METHODS

AR-FL and AR-V levels were analyzed in PC and non-PC cell lines upon artificial increase of AR pre-mRNA using either drug treatment or AR gene activation. Furthermore, expression of AR-FL and AR-Vs was determined in PC specimen at distinct stages of disease (primary (n = 10) and metastatic tissues (n = 20), liquid biopsy samples (n = 422), mCRPC liquid biopsy samples of n = 96 patients starting novel treatment). Finally, baseline AR-FL and AR-V status was correlated with clinical outcome in a defined cohort of n = 65 mCRPC patients undergoing ARTA treatment.

RESULTS

We revealed rising levels of AR-FL accompanied with appearance and increase of AR-Vs in dependence of elevated AR pre-mRNA levels. We also noticed increase in AR-FL and AR-V levels throughout disease progression. AR-V expression was always associated with high AR-FL levels without any sample being solely AR-V positive. In patients undergoing ARTA treatment, AR-FL did show prognostic, yet not predictive validity. Additionally, we observed a substantial clinical response to ARTA treatment even in AR-V positive patients. Accordingly, multivariate analysis did not demonstrate independent significance of AR-Vs in neither predictive nor prognostic clinical utility.

CONCLUSION

We demonstrate a correlation between AR-FL and AR-V expression during PC progression; with AR-V expression being a side-effect of elevated AR pre-mRNA levels. Clinically, AR-V positivity relies on high levels of AR-FL, making cells still vulnerable to ARTA treatment, as demonstrated by AR-FL and AR-V positive patients responding to ARTA treatment. Thus, AR-FL and AR-V might be considered as a prognostic, yet not predictive biomarker in mCRPC patients.

Development and validation of a multigenomic liquid biopsy (PROSTest) for prostate cancer detection

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Background: A crucial requirement in prostate cancer (PCa) management is an accurate, easily measurable, liquid biopsy that can define the molecular pathology of an individual PCa. We report the development and clinical validation of a novel PCa-specific, multi-genomic biomarker. Methods: We identified candidate mRNA biomarkers in PCa-Adeno transcriptomes ( n=1,159) using several strategies: co-expression networks, differential expression, and functional enrichment. mRNA transcripts were screened in an independent tumor tissue ( n=50) set and validated as biomarkers in the TCGA-PRAD ( n=500) dataset. An amalgam of Random Forest, Gradient Boosted Machines and Support Vector Machines, all standard machine learning classifiers, was used to develop a classification algorithm and probability score in a peripheral blood gene expression test cohort ( n=430). This multigene biomarker was validated in two independent clinical blood sample sets (Set I: PCa n=77, controls n=54; Set II: PCa n=132, controls/BPH n=99) to determine as PCa-specificity and diagnostic efficacy Clinical utility was evaluated versus Gleason scores, T-staging and PSA ( n=209) and in a prostatectomy cohort ( n=47). Results: The pipeline identified 27 of PCa gene markers in the tumor tissue set and TCGA-PRAD dataset. Gene expression was significantly correlated ( r=0.72, p<0.0001) in matched tissue/blood samples. The PROSTest (scale: 0-100) ensemble algorithm (developed in blood) had a sensitivity for PCa of 92.2% (95% CI: 83.8-97.1%; Set I) and 95.0% (95% CI: 89.9-98%. Set II). The specificity was 100% for Set I (95% CI: 93.4-100%) and 100% for Set II (95% CI: 96.3-100%). PCa scores were significantly ( p<0.0001) lower for controls (Set I: 17±4; Set II: 18±4) and BPH (19±6) to PCa; 82±19 (Set I) and 80±19 (Set II). The AUROC was 0.98±0.01. PROSTest scores were elevated ( p<0.05) in T2-4 and were significantly correlated with Gleason ( r=0.93, p<0.02). In contrast, PSA from matched samples was not associated ( p=NS) with clinically significant disease (Gleason 7-10 or T2-4 tumors). In head-to-head comparisons, the PROSTest was considerably more accurate than PSA for detecting significant disease (z-statistic: 2.43, p=0.015). In the R0 prostatectomy cohort, all scores were elevated (72±7) and significantly decreased post-surgery (26±8, p<0.0001, n=37). Individuals with residual disease ( n=10) exhibited elevated (60±4) post-surgical scores. Conclusions: The PROSTEst is a multigenomic blood-based PCR tool that accurately (>90%) identifies prostate cancer. It is significantly more accurate than PSA for the detection and stratification of clinically significant prostate disease. A multigenomic liquid biopsy for PCA provides a real-time, non-invasive method for detection of a PCa and may facilitate the early identification of residual/recurrent disease.

Presence of CTCs and its prognostic potential compared to AR-V7 expression in mCRPC undergoing androgen-deprivation therapy

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Background: Biomarkers predicting response to mCRPC treatment are rare. CTCs and AR-V7 status have been discussed as potential prognosticators. Methods: We evaluated 64 patients (pts.) treated with abiraterone (n=47) or enzalutamide (n=17), determined CTCs and analyzed AR-V7 status in correlation with survival using Kaplan-Meier-estimates and Cox-regression-models. Results: For PSA response, CTC- vs. CTC+ were not different (p=0.25) whereas AR-V7 status was predictive (68.2% AR-V7- and 33.3% AR-V7+ pts. (p=0.01)). Median PSA PFS was 17 mo. (CI 9.5-24.5) for CTC- and 6 (CI 5.2-6.9) for CTC+ pts. (p<0.01) with 9 mo. (CI 4.2-13.8) for CTC+/AR-V7- and 5 (CI 3.0–7.0) for CTC+/AR-V7+ pts. (p=0.04). In univariate cox regression analysis (UV), prior abiraterone or enzalutamide (A/E) (p=0.01), bone metastases (p=0.03), CTC+ (p=0.01), AR-V7+ (p=0.01), Hb ≤12 g/dl (p=0.01) and PSA decline ≥50% (p<0.01) were significant prognosticators. Within the CTC+ subgroup, AR-V7+ (p=0.02) and PSA decline ≥50% (p=0.03) showed a relevant difference. In multivariate analysis (MV), for CTC+ pts, AR-V7+ (p=0.02), PSA decline ≥50% (p=0.02) and visceral metastases (p=0.02) remained independent prognosticators. The analysis for PFS resulted in 22 mo. (CI NA) for CTC- compared to 9 (CI 7.7-10.3) for CTC+ (p=0.01) and 10 mo. (CI 8.2-11.8) for CTC+/AR-V7- vs. 6 (CI 1.9-10.1) for CTC+/AR-V7+ (p=0.07). Performing UV, prior A/E (p<0.01), CTC+ (p=0.01), AR-V7+ (p=0.01), Hb ≤12 (p<0.01), PSA decline ≥50% (p<0.01) and ALP elevated at baseline (p=0.03) showed statistically significant differences. Within the CTC+ subgroup, prior A/E (p=0.01), visceral metastases (p=0.02), Hb ≤12 (p=0.01) and PSA decline ≥50% (p=0.03) were significant prognosticators, whereas AR-V7+ was not. In MV of CTC+ pts, visceral metastases (p=0.02), PSA decline ≥50% (p=0.02) and Hb ≤12 (p=0.05) remained independent prognosticators. Median OS was not reached for CTC- and 17 mo. (CI 9.8–24.2) for CTC+ (p<0.01) with 27 (CI 10.6-43.4) vs. 14 (CI 10.4-17.7) mo. for AR-V7- and AR-V7+, respectively (p=0.06). UV resulted in statistically relevant differences for prior docetaxel (p=0.01), prior A/E (p<0.01), visceral metastases (p=0.02), CTC+ (p=0.01), AR-V7+ (p<0.01) and Hb ≤12 (p< 0.01). Within CTC+, prior docetaxel (p<0.01), prior A/E (p=0.01), visceral metastases (p<0.01) and Hb ≤12 (p<0.01) were statistically relevant parameters. UV for AR-V7 status did not result in a significant difference for OS either. In MV, CTC status as well as Hb ≤12 remained independent prognosticators (p=0.04 and p<0.01, respectively). For MV of CTC+, visceral metastases (p=0.01), Hb ≤12 (p<0.01) and prior docetaxel (p=0.01) were independent prognosticators of OS. Conclusions: Presence of CTCs seems to prognosticate PFS and OS in mCRPC patients undergoing Androgen-deprivation while presence of AR-V7 does not despite its predictive potential.

Abstract 3389: A multi-gene prostate cancer liquid biopsy with &gt; 92% accuracy in diagnosis and assessment of disease status

Background: There are a paucity of blood-based biomarkers with clinical utility for prostate cancer (PCa). We examined a circulating-free mRNA (27-gene) prostate cancer signature to diagnose PCa. Clinical utility of the assay was then assessed in surgical patients.

Methods: Gene identification and validation: Publicly available PCa transcriptome sets (n=5) (E-GEOD-46691, E-GEOD-46602, E-GEOD-62116, E-GEOD-62667, E-GEOD-72220: n=1,159 samples); PCA cell lines (n=7) gene expression in 22Rv1 and E006AA-hT (localized); VCaP; PC-3; LNCaP; DU145 and MDA PCa2b (all metastatic) from two normal prostate epithelial lines: PWR-1E and RWPE-1 and validated in PCa tumor tissue (n=50). Transcriptome analyses: tumor compared with normal blood-based transcriptomes using gene co-expression network enrichment, differential expression and functional enrichment analyses to identify candidate markers. Blood gene expression: PCa set #I: n=132, PCA set #II: n=50 (biochemical recurrence [BCR]), BPH: n=44, controls n=55. We then constructed an artificial intelligence PCa model using classification algorithm analyses. Scoring: normalized algorithmically analyzed gene expression (0 to 100), positive score ≥20. Matched tumor/ blood samples: n=50. PSA: BPH (n=44) and PCa (n=132). Clinical score assessment: Score utility was assessed in surgical cohorts: Surgical: (n=47), scores =pre-surgical and post: 1 week - 14 months. Statistics: Non-parametric (Kruskal-Wallis), Pearson-correlation, Fisher's and AUROC analyses (Mean±SEM).

Results: Transcriptomic analysis identified a 27 gene blood signature for PCa. Expression levels were significantly elevated (p&lt;0.001, 2.1-35.8-fold) in cell lines and PCA tumors. The matched tissue/blood correlation was r: 0.56 (p=0.0023). In PCa #I, levels were 47±2 (p&lt;0.0001) compared to BPH (19±1) and controls (18±0.5); AUROC: 0.92 (BPH) and 0.94 (controls), with an accuracy of 85-88%, a sensitivity of 86% and specificities 82 & 93% respectively. For PSA the AUROC (PCa vs. BPH) was 0.51 (p=0.88). PSA was positive in 86% of BPH and was &gt;10ng/ml in 30%. PSA was positive in 83% of PCa and &gt;10ng/ml in 40% (Fisher's exact: p=0.28). PSA accuracy (&gt;10ng/ml) was 48%. Levels in PCA #II (BCR) were 44±3. ProstaTest-was positive in 48 (96%). Surgical cohort (n=47): PCa Prostatest accuracy 100% pre-surgery. Resection significantly decreased levels (KW-statistic: 57.4, p&lt;0.0001) from 52±1 to 23.5±2.

Conclusion: The diagnostic accuracy of a PCa molecular blood-signature was 92%; significantly better than PSA (48%, p&lt;0.0001). Surgical resection significantly (p&lt;0.0001) decreased levels. Biochemical recurrence was accurately detected (96%). A multi-gene prostate cancer liquid biopsy seems likely to have clinical utility in the diagnosis and monitoring management of PCa.

Citation Format: Kambiz Rahbar, Mark Kidd, Ignat Drozdov, Alexandra Kitz, Anna Malczewska, Pawel Rajwa, Christof Bernemann, Lisa Bodei, Irvin Modlin. A multi-gene prostate cancer liquid biopsy with &gt; 92% accuracy in diagnosis and assessment of disease status [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3389.

Abstract 1999: Diagnostic utility of the NETest in neuroendocrine transformed prostate cancer

Background: Neuroendocrine differentiation and the development of an aggressive phenotype are key features of castration-resistant prostate cancer (CRPC) disease. Current blood-based biomarkers cannot detect these treatment-refractory cancer variants.

Aims: Evaluate the utility of the NETest, a blood-based 51-marker gene neuroendocrine detection tool, as a CRPC diagnostic and examine which functional gene clusters (hallmarks) differentiate CRPC from PCa.

Methods: NETest gene identification in CRPC: Publicly available CRPC RNAseq dataset (cBIO Portal: dbGap phs000909.v.p1, tissue samples: n=47, including 15 neuroendocrine CRPC). Blood gene expression: Prostate cancers (PCa): (n=50) CRPC, (n=40) hormone-sensitive PCa (n=75), and benign prostatic hyperplasia (BPH) (n=41). NETest assay: PCR (51 genes): Expression normalized and categorized into functional classifiers. 51 markers algorithmically assessed and scored: 0-100. Cut-off 40 for progressive disease. PSA: ECLIA diagnostic assay: cut-off 4ng/L, &gt;10ng/ml=critical value. Statistics: ANOVA, AUROC analyses and sensitivity/specificity metrics. Data is mean±SEM.

Results: RNA tissue seq: Captured all 51 NETest genes (100%). Thirty-three (65%) genes were detected as upregulated in CRPC tumors (1.09-1425 fold elevated over normal tissue). Blood-PCR: In CRPC, detected in 49/51 (96%) NETest genes. Gene expression was significantly upregulated (p&lt;0.01) in CRPC vs. PCa for somatostatin receptors (2-fold), inflammasome and fibrosome (1.9-fold), proliferome (1.6-fold) and RAF-RAS signaling (1.4-fold). NETest scores were elevated in CRPC (80±2.4) (ANOVA, p&lt;0.0001) vs. PCa (36±2) and BPH (36±3). The AUC differentiating CRPC from PCa was 0.92 (p&lt;0.0001). The cut-off of 40 imparted diagnostic sensitivities and specificities of 94% and 87%, respectively. PSA: PSA was elevated in CRPC (27±59ng/ml). This was not different to PCa (8.1±8ng/ml, p=0.43) but was increased vs. BPH (6.8±1.2ng/ml, p&lt;0.005). The AUC for CRPC vs. PCA was 0.60 (p=0.10). PSA&gt;10ng/ml occurred in 63% of CRPC, 55% of PCA (p=NS) and 24% of BPH (p&lt;0.05). The AUC for NETest (0.92) was significantly better (p&lt;0.0001) than PSA (0.6).

Conclusion: The NETest detects neuroendocrine neoplasia genes in the blood and accurately identifies genomic hallmarks of castration-resistant prostate cancer. It performs significantly better than PSA. This multi-gene NETest liquid biopsy is likely to have clinical utility in the diagnosis of CRPC and provide a basis to stratify patients for CRPC-based therapies.

Citation Format: Kambiz Rahbar, Mark Kidd, Ignat Drozdov, Alexandra Kitz, Anna Malczewska, Lisa Bodei, Pawel Rajwa, Christof Bernemann, Irvin Modlin. Diagnostic utility of the NETest in neuroendocrine transformed prostate cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1999.

Antibody selection influences the detection of AR-V7 in primary prostate cancer

BACKGROUND

The androgen receptor (AR) splice variant V7 (AR-V7) is an emerging marker to aid clinical decision-making in patients with castration-resistant prostate cancer (CRPC). A number of studies have shown that a subset of patients also express AR-V7 in the primary tumor. These findings have recently been challenged by a study showing that AR-V7 becomes only detectable in CRPC but is virtually absent in castration-naïve prostate cancer.

METHODS

Herein, we directly compare the two relevant antibodies used for the immunodetection of AR-V7 in the conflicting studies (clones AG10008 and RM7) in a predominantly high-risk prostate cancer patient cohort with primary tumor specimens assembled in a tissue microarray (TMA).

RESULTS

The overall rate of AR-V7 positive TMA cores was comparable (AG10008, 24.9%; RM7, 21%). However, the percentage agreement of identical staining intensities of positive cores was only 7%. In contrast, the percentage agreement of negative cores was 62.8%. In approximately 30% of the cores, the antibodies produced discordant staining intensities. Only one of the two antibody stainings (AG10008) conveyed prognostic information and was associated with a shorter progression-free patient survival.

CONCLUSIONS

Our study underscores that nuclear AR-V7 expression can be detected in primary prostate cancer prior to long-term androgen deprivation and castration resistance. There are staining differences between the two antibodies in tumor tissue, for which we currently have no explanation. Clearly, improvements in the detection of functional AR-V7 in prostate cancer are urgently needed.

Molecular analysis of circulating tumor cells of metastatic castration-resistant Prostate Cancer Patients receiving 177Lu-PSMA-617 Radioligand Therapy

Rationale: Lu-177-PSMA-617 radioligand therapy (RLT) is currently under approval for treatment of metastatic castration resistant prostate cancer (mCRPC) patients with late stage disease. However, previous studies demonstrated both heterogeneity of prostate specific membrane antigen (PSMA) expression, as well as response to PSMA treatment among mCRPC patients. Thus, there is an unmet need for identifying predictive parametres prior or under PSMA-RLT treatment. We therefore aimed to correlate several clinical and molecular parameters with response to PSMA treatment in a cohort of mCRPC patients undergoing PSMA RLT followed by a detailed analysis of promising candidates.

Methods: Nineteen patients, median age 68.8 years (range: 56.9 - 83.3) with mCRPC were included in this study. We performed baseline analysis of clinical parameters based on PSMA PET/CT, (metabolic tumor volume (MTV), total tumor volume (TTV)), serum PSA, ALP, LDH and gene expression analysis of circulating tumor cells (expression of AR full length (AR-FL), AR splice variant 7 (AR-V7), PSA and PSMA) as well as common markers for neuroendocrine differentiation (NED).

Results: Patients presented with bone, lymph node, and visceral metastases (89%, 68%, and 21%, respectively). All patients were pretreated with docetaxel, either abiraterone or enzalutamide, or both. Biochemical response in terms of PSA decline ≥50 or ≥30% was observed in 42% and 63%, respectively. There were significant correlations between PSA and PSMA mRNA expression, as well as tumor volumes (both MTV and TTV), AR-FL and AR-V7 mRNA expression. However, there was no correlation with response to PSMA treatment. Furthermore, none of these parameters was significantly correlated with baseline serum PSA values. Common NED markers were shown to be specifically high expressed and revealed impact on OS independent from AR-V7 gene expression.

Conclusion: We demonstrate that AR-FL and its splice variant AR-V7 might serve as prognostic biomarkers displaying high tumor burden in mCRPC patient prior to PSMA-RLT. Contrary, PSMA, which has been discussed as a biomarker for PSMA targeted treatment, does not display strong prognostic ability - at least on the mRNA level. Surprisingly, none of these parameters correlates to response to PSMA treatment. In contrast, commom NED markers such as SYP and ENO2 as well as FOXA1 expression level seem to predict OS, but not PFS, more reliably. We admit that a limitation of our study is the focus on mRNA expression of potential biomarkers only. Further investigations analyzing the potential role of protein expression of these markers are therefore warranted.

Combinatorial expression of androgen receptor splice variants: No predictive value in castration-resistant prostate cancer patients treated with enzalutamide (enza) or abiraterone (abi)

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Background: Playing an important role in prostate cancer, androgen receptor (AR) signaling is a common therapeutic target. Novel hormonal treatment (NHT) using enza or abi prolongs overall survival in men with metastatic castration-resistant prostate cancer (mCRPC). However, biomarkers predicting therapy response are limited. AR-V7, as the most abundant AR splice variant, has gained clinical interest. Nonetheless, current discussions on its predictive power are diverse. Given that AR-V7 as a sole biomarker is not efficient in predicting response to NHT, we aimed to increase the predictive potential by analysis of combinatorial AR splice variant (AR-V) expression in mCRPC patients undergoing NHT. Methods: We prospectively enrolled 60 patients who started on either abi or enza. Presence of circulating tumor cells (CTC) as well as expression of AR-V3, -7 and -9 were assessed. Outcomes in CTC-, CTC+/AR-V- and CTC+/AR-V+ patients were analyzed considering PSA reduction, PSA-PFS, PFS and OS. Results: PSA reduction of 50% was predominantly found in CTC- patients (78.5%) compared to CTC+/AR-V- (55.5%) and CTC+/AR-V+ (39.3%) without statistical significance (P = 0.059). When taking co-expression of two or more AR-V into account there was no difference in PSA response either (one AR-V 42.9%, two AR-V 33.3%, three AR-V 41.6%, P = 0.154). Median PSA-PFS was 17 months (95%CI 15.7 – 18.3), 13 months (95%CI 6.8 – 19.2) and 5 months (95%CI 3.6 – 6.4) for CTC- pts, CTC+/AR-V- pts and CTC+/AR-V+ pts, respectively (P = 0.005). However, comparing CTC- and CTC+ pts, differences become even more apparent (P = 0.004), CTC+/AR-V- and AR-V+ pts showed less statistically significant differences (P = 0.029). Median PFS and OS were not reached for CTC- pts. PFS was 10 months (95%CI 6.2 – 13.8) for CTC+/AR-V- pts and 9 months (95%CI 1.1 – 16.9) for CTC+/AR-V+ pts (P = 0.004, only CTC- vs. CTC+ P = 0.002). OS was 28 months (95%CI 16.8 – 39.2) for CTC+/AR-V- pts and 15 months (95%CI 7.9 – 22.1) for CTC+/AR-V+ pts (P = 0.014, only CTC- vs. CTC+ P = 0.006). Regarding PFS and OS, there was no difference comparing only CTC+/AR-V- and AR-V+ pts (P = 0.356 and P = 0.244). Conclusions: AR splice variants have prognostic power in stratifying mCRPC patients suffering from a more advanced stage of disease. Nonetheless, our study clearly demonstrates the lack of predictive power of AR splice variants for response to NHT. Additionally, we prove the importance of CTC analysis rather than AR-V expression being more valuable in mCRPC.

A genomic blood test (NETest) identifies neuroendocrine transformation of prostate cancer

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Background: Neuroendocrine-like differentiation (NELD) and an aggressive phenotype are key features of castration-resistant prostate cancer (CRPC). Current blood-based biomarkers cannot detect these treatment-refractory variants. Our aim was to evaluate the NETest, a blood-based 51-marker gene neuroendocrine detection tool, as a CRPC-diagnostic versus prostate cancer (PCA). Methods: In silico evaluation: NETest gene identification in the TCGA-PRAD ( n= 500 PCA) and CRPC RNAseq datasets (cBIOPortal: dbGap-phs000909.v.p1, tissue samples: n= 47, including 15 CRPC). Blood gene expression: PCA: n= 50, CRPC: n= 40, hormone-sensitive PCA: n= 75 and benign prostatic hyperplasia (BPH: n= 41). NETest assay: Normalized gene expression, algorithmically assessed and scored: 0-100. Cut-off 20. PSA: ECLIA diagnostic assay: cut-off 4ng/L, > 10ng/ml = actionable value. Statistics: ANOVA, AUROC analyses and sensitivity/specificity metrics. Data is mean±SEM. Results: RNAseq: Two (4%) of the 51 NETest genes were identified in TCGA-PCA. In contrast, all 51 NETest genes (100%) were identified in CRPC tumors. Thirty-three (65%) were detected as upregulated (1.09-1425-fold vs. normal tissue). Blood-PCR: 49/51 (96%) NETest genes detected in CRPC blood. NELD-gene expression was significantly upregulated ( > 2-fold, p< 0.01) in CRPC vs. PCA ( TPH1, PNMA2, SSTR etc). NETest scores were elevated in CRPC (79±2.8) (ANOVA, p< 0.0001) vs. PCA (22±2) and BPH (23±3). The AUC differentiating CRPC from PCA was 0.93 ( p< 0.0001). NETest was elevated in 94% of CRPC vs. 13% PCA and 15% BPH (both p< 0.001). The diagnostic sensitivities and specificities were 94% and 87%, respectively. PSA: PSA was elevated in CRPC (220±372ng/ml). This was different to PCA (14±20ng/ml, p< 0.0001) and BPH (10.3±5.7ng/ml, p< 0.003). The AUC for CRPC vs. PCA/BPH was 0.70 ( p= 0.10). PSA > 10ng/ml occurred in 70% of CRPC, 60% of PCA ( p= NS) and 39% of BPH ( p< 0.05). The AUC for NETest (0.93) was significantly better than PSA (z-statistic: 4.63, p< 0.0001). Conclusions: The NETest is a liquid biopsy that detects neuroendocrine neoplasia genes in the blood and accurately identifies NELD in castration-resistant prostate cancer. We anticipate that the NETest could be used to provide real-time information relevant to the evolving neuroendocrine status of a PCA during therapy.

A blood-based multi-mRNA liquid biopsy with >90% accuracy for diagnosis and assessment of prostate cancers

5574

Background: There are a paucity of blood-based biomarkers with clinical utility for prostate cancer (PCa). We developed a circulating mRNA (27-gene) prostate cancer signature to diagnose and manage PCa. Methods: Gene identification: Publicly available PCa transcriptome sets ( n= 1,159 samples) were evaluated and compared with normal blood-based transcriptomes using gene co-expression network enrichment, differential expression and functional enrichment analyses to identify candidate markers. Gene expression evaluation: Seven PCA cell lines and two normal prostate epithelial lines were used to assess candidate genes. Marker genes were determined in PCa tumor tissue ( n= 50) and validated in the TCGA-PRAD ( n= 500) dataset. Blood gene expression: Set #I: PCA: n= 132, BPH: n= 44, controls n= 55. Set #II: n= 50 (biochemical recurrence [BCR]). We constructed an artificial intelligence PCa model using classification algorithm analyses. Scoring: normalized algorithmically analyzed gene expression (0 to 100), positive score >20. PSA: BPH ( n= 44) and PCa ( n= 132). Clinical score assessment: Surgical cohort: ( n= 47), samples: pre-surgical and post: 1 week - 14 months. Statistics: Kruskal-Wallis, Pearson-correlation, Fisher’s and AUROC analyses (Mean±SEM). Results: Transcriptomic analysis identified 27 candidates. Cell lines/tissue: Expression levels were significantly elevated ( p< 0.001, 2.1-35.8-fold) in cell lines and PCa surgical samples. All 27 markers were confirmed in TCGA-PRAD samples (average TPM: 58 to 10,366). Blood: In Set#I, levels in PCa were 47±2 ( p< 0.0001) compared to BPH (19±1) and controls (18±0.5); AUROC: 0.92 (BPH) and 0.94 (controls), with an accuracy of 85-88%, a sensitivity of 86% and specificities 82 and 93%. For PSA, the AUROC (PCa vs. BPH) was 0.51 ( p= 0.88). PSA was positive in 86% of BPH and was > 10ng/ml in 30%. PSA was positive in 83% of PCa and > 10ng/ml in 40% (Fisher’s p= 0.28). PSA accuracy ( > 10ng/ml) was 48%. Levels in Set#II (BCR) were 44±3. ProstaTest-was positive in 48 (96%). Surgical cohort ( n= 47): Prostatest accuracy 100% pre-surgery. Resection decreased levels (KW-statistic: 57.4, p< 0.0001) from 52±1 to 23.5±2. Conclusions: A 27-gene blood signature was developed for PCa that exhibited a diagnostic accuracy of 92%; significantly better than PSA (48%, p< 0.0001). Surgical resection significantly ( p< 0.0001) decreased levels. Biochemical recurrence was accurately detected (96%). A multi-gene prostate cancer liquid biopsy is likely to have clinical utility in both diagnosis and monitoring of PCa.

Correlation between SFRP1 expression and clinicopathological parameters in patients with triple-negative breast cancer

Aim: Breast cancer is a heterogeneous disease with distinct molecular and clinical behavior demanding reliable biomarkers, especially in triple-negative breast cancer (TNBC). This study seeks to improve the understanding of SFRP1 as a potential biomarker in breast cancer focusing on TNBC. Materials & methods: SFRP1 expression was investigated via immunohistochemistry with two anti-SFRP1-antibodies on tissue-microarrays of 376 invasive breast cancers. Results: Statistical analysis revealed a highly significant association between TNBC (n = 36) and SFRP1 expression (p < 0.001). SFRP1 expression was significantly associated with younger age, higher tumor stage, size and grade. Conclusion: SFRP1 expression is strongly correlated with TNBC on protein level. Associations with age and tumor grade support the role of SFRP1 as a biomarker for chemotherapy response in TNBC.

Performance comparison of two androgen receptor splice variant 7 (AR-V7) detection methods

OBJECTIVES

To compare the performance of two established androgen receptor splice variant 7 (AR-V7) mRNA detection systems, as paradoxical responses to next-generation androgen-deprivation therapy in AR-V7 mRNA-positive circulating tumour cells (CTC) of patients with castration-resistant prostate cancer (CRPC) could be related to false-positive classification using detection systems with different sensitivities.

MATERIALS AND METHODS

We compared the performance of two established mRNA-based AR-V7 detection technologies using either SYBR Green or TaqMan chemistries. We assessed in vitro performance using eight genitourinary cancer cell lines and serial dilutions in three AR-V7-positive prostate cancer cell lines, as well as in 32 blood samples from patients with CRPC.

RESULTS

Both assays performed identically in the cell lines and serial dilutions showed identical diagnostic thresholds. Performance comparison in 32 clinical patient samples showed perfect concordance between the assays. In particular, both assays determined AR-V7 mRNA-positive CTCs in three patients with unexpected responses to next-generation anti-androgen therapy. Thus, technical differences between the assays can be excluded as the underlying reason for the unexpected responses to next-generation anti-androgen therapy in a subset of AR-V7 patients.

CONCLUSIONS

Irrespective of the method used, patients with AR-V7 mRNA-positive CRPC should not be systematically precluded from an otherwise safe treatment option.

Comparison of isolation platforms for detection of circulating renal cell carcinoma cells

Background

Analysis of circulating tumor cells (CTCs) has progressed in several tumor entities. However, little is known about CTCs in clear cell renal cell carcinoma (ccRCC) patients. Aim of our studies was to build a stable in vitro fundament for isolation of CTCs in ccRCC.

Methods

We compared the analytical performance of different CTC isolation methods with regard to yield and purity: EpCAM based enrichment, leukocyte depletion and size based enrichment. EpCAM and cytokeratin 8 (KRT8) as biomarker for CTCs expression were evaluated in ccRCC cell lines as well as clinical samples.

Results

While the EpCAM based approach failed to successfully isolate tumor cells, CD45 based approaches showed intermediate recovery rates. The cell-size based Parsortix system showed highest recovery rates. EpCAM expression was low or absent in most cell lines as well as in clinical samples, whereas KRT8 was detected as a potential biomarker in ccRCC.

Conclusion

EpCAM based approaches might miss a high number of CTCs due to low or absent expression of EpCAM in ccRCC, as shown in cell lines as well as in patient samples. We identified the cell-sized based, label independent Parsortix system to be the most effective recovery system for ccRCC CTCs.

Abstract LB-045: Cogency of AR-V7 unexpected responders determined by using distinct detection technologies

Background: The validity of AR-V7 in CTC’s as a predictive marker for non-response to next generation ADT (abiraterone or enzalutamide) has recently been questioned. Specifically, a subset of AR-V7 positive patients showed responses to abiraterone or enzalutamide and assay performance differences could contribute to these unexpected findings. [[Unsupported Character - Codename &shy;]]To our knowledge a direct performance comparison has not been performed. Here we present comparative head to head analysis of different AR-V7 detection technologies with respect to specificity, accuracy and clinical sensitivity.

Methods: We performed comparison of two different AR-V7 detection technologies using either SYBR Green or TaqMan chemistry. Both assays were tested on identical in vitro samples consisting of genitourinary cancer cell lines as well as dilution series of AR-V7 positive cDNA samples. Finally, clinical samples with previously determined CTC and AR-V7 status using TaqMan chemistry were re-analyzed using SYBR Green chemistry.

Results: Both assays performed identical in detection of AR-V7 in different genitourinary cancer cell lines. Additionally, by performing dilution series analyses we observed the same diagnostic threshold of both assays. When re-analysis of clinical samples was performed, both assays performed undistinguishable in determination of the AR-V7 status of mCRPC patients, including 3 patients exhibiting unexpected response to NHT despite AR-V7 positive CTCs. Finally, loss of AR-V7 positive CTCs in serial CTC analysis of one patient during abiraterone treatment was observed using both detection assays.

Conclusion: By demonstrating nearly identical performance metrics, we excluded assay design differences as an underlying reason for the unexpected responses in a subset of AR-V7 patients. Interestingly, for the first time, we detected an AR-V7 positive mCRPC patient displaying a loss of AR-V7 positive CTCs during NHT therapy. These findings underscore that - irrespective of the method used - AR-V7 positive patients should not systematically be precluded from an otherwise safe treatment attempt.

Citation Format: Christof Bernemann, Verena Humberg, Martin Bögemann, Andres J. Schrader, Julie Steinestel, Jochen K. Lennerz. Cogency of AR-V7 unexpected responders determined by using distinct detection technologies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-045. doi:10.1158/1538-7445.AM2017-LB-045

Abstract 2760: Proof of principle studies for detection of circulating renal cancer cells from blood samples using diverse technologies

Background: During the past years, much progress has been made in detection and analysis of circulating tumor cells (CTCs) in several tumor entities, including prostate cancer, breast cancer or lung cancer. However, little is known about circulating tumor cells in patients suffering from clear cell renal cell carcinomas. The majority of technologies detecting CTCs is based on expression of epithelial markers on the surface of these cells, e.g. EpCAM. Additionally, biophysical approaches have been invented to detect CTCs based on size, invasive capacity or density. In order to be able to detect CTCs in patient samples, in vitro establishment of the most accurate isolation procedure followed by precise detection techniques has to be performed. Aim of our studies was to build a stable in vitro fundament of isolation and subsequent detection of CTCs in ccRCC patients. Methods: We made use of 4 different technologies, all of which have been approved for detection of CTCs in distinctive tumor entities. We used EpCAM based positive enrichment of CTCs, Ficoll densitiy centrifugation followed by CD45-positive cell depletion, rosette formation followed by CD45 positive cell depletion as well as size and deformability based enrichment technologies by using the Parsortix system. Furthermore, by using 4 phenotypically distinct ccRCC cell lines, we tried to detect markers unique for tumor cells in demarcation to blood cells. Results: By performing spiking experiments of renal cancer cells, we found the highest recovery rates by using the size based Parsortix system. Interestingly, the most established technique of EpCAM based isolation failed in three out of four cell lines to recover more than 40%. Expression of well-established markers for ccRCC, like carboanhydrase (CA)-9, could be detected in renal cancer cell lines. However, expression was also found in blood samples of healthy donors. Another marker used for immunohistochemical diagnosis of ccRCC, PAX8, showed weak to absent expression in established renal cancer cell lines. The highest specificity to detect renal cancer cells in blood samples was found when analyzing KRT8 or KRT 19 expression. Conclusion: Our results demonstrate that firstly, using the EpCAM based CTC enrichment, which is the basis of the CellSearch system, which up to now is the only methodology approved by the FDA, the majority of renal cancer cells will presumably not be detected in blood samples. This seems largely due to low or absent expression of EpCAM on renal cancer cells. The usage of the size based Parsortix system showed the highest recovery rates and should therefore be analyzed in more detail on samples of ccRCC patients. Secondly, an exclusive marker for defining a renal CTC is still missing. Some well-established ccRCC markers, like CA-9, failed to specifically detect renal cancer cells in blood samples, as they were either present also in healthy blood samples or absent in renal cancer cell lines.

Citation Format: Yvonne Maertens, Verena Humberg, Julie Steinestel, Martin Boegemann, Andres J. Schrader, Christof Bernemann. Proof of principle studies for detection of circulating renal cancer cells from blood samples using diverse technologies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2760. doi:10.1158/1538-7445.AM2017-2760

Resistenzentwicklung und prädiktive Marker beim metastasierten Prostatakarzinom

Anders als bei vielen anderen Krebserkrankungen gab es beim Prostatakarzinom lange Zeit keinen Ansatz für eine individualisierte Therapie. Seit der Zulassung von mehreren modernen Wirkstoffen für die Therapie des fortgeschrittenen Stadiums ändert sich dies allmählich. Zunächst galt die Androgenrezeptor-Splice-Variante AR-V7 als vielversprechender Biomarker für die Therapiesteuerung, woran sich zunehmend Zweifel mehren. Inzwischen gibt es jedoch eine Reihe von weiteren neuen, noch nicht zugelassenen und nicht (nur) auf den Androgenrezeptor fokussierenden Therapieansätzen, die auch beim fortgeschrittenen Prostatakarzinom eine personalisierte Medizin wahrscheinlicher machen.

Expression of AR-V7 in Circulating Tumour Cells Does Not Preclude Response to Next Generation Androgen Deprivation Therapy in Patients with Castration Resistant Prostate Cancer

The androgen receptor splice variant AR-V7 has recently been discussed as a predictive biomarker for nonresponse to next-generation androgen deprivation therapy (ADT) in patients with castration-resistant prostate cancer. However, we recently identified one patient showing a response from abiraterone despite expression of AR-V7 in his circulating tumour cells (CTC). Therefore, we precisely assessed the response in a cohort of 21 AR-V7 positive castration-resistant prostate cancer patients who had received therapy with abiraterone or enzalutamide. We detected a subgroup of six AR-V7 positive patients showing benefit from either abiraterone or enzalutamide. Their progression free survival was 26 d (censored) to 188 d. Four patients displayed a prostate-specific antigen decrease of >50%. When analysing prior therapies, we noticed that only one of the six patients had received next-generation ADT prior to CTC collection. As a result, we conclude that AR-V7 status in CTC cannot entirely predict nonresponse to next generation ADT and AR-V7-positive patients should not be systematically denied abiraterone or enzalutamide treatment, especially as effective alternative treatment options are still limited.

PATIENT SUMMARY

A subgroup of patients can benefit from abiraterone and/or enzalutamide despite detection of AR-V7 splice variants in their circulating tumour cells.

Abstract 3496: Improvement of response to chemotherapy in breast cancer cells by the use of the non-oncologic drug minocycline

Introduction

The majority of breast cancer patients receive (neo-) adjuvant chemotherapy. Although a high percentage of patients show good response - as shown by pathologic complete response - another high number of patients does not profit from chemotherapeutic treatments. Therefore, there is a high demand for improvement of chemotherapeutic treatments.

It has been proposed that non-oncologic drugs, which are used in treatment of other diseases, might represent a valid novel therapeutic approach, as these drugs have already been tested for side effects, etc. Nonetheless, a dramatic breakthrough by using non-oncologic drugs as single treatment agents has not been published so far.

However, we hypothesized that a combinatorial treatment using oncologic drugs as well as non-oncologic drugs might improve the response to classical cancer treating agents, e.g. chemotherapeutic agents.

Recently, we could show a sensitization of triple negative breast cancer cells to chemotherapy by using the anti-androgenic drug dutasteride in combination with either cisplatinum as well as paclitaxel (von Wahlde et al., 2014).

Currently, we deeply analyze the effect of another non-oncologic drug - minocycline - in the treatment of breast cancer cells. Minocycline has been described as a broad-spectrum tetracycline antibiotic. It has already been proposed that it might also improve chemotherapeutic treatments as well as radiation treatments (Sotomayor et al. 1992). However, an improvement of chemotherapy in breast cancer patients has not been described so far.

Methods

Breast cancer cells were treated with increasing concentrations of minocycline. Subsequently, cells were treated with minocycline in combination with different cytotoxic agents. Cell viability was measured using MTT assays. Molecular biological analyses were performed in order to dissect the mechanisms resulting in altered chemotherapeutic responses.

Results

When treated in the presence of minocycline alone, some breast cancer cells showed reduced viability only at high concentrations. The combinatorial treatment using minocycline plus cytotoxic agents however, greatly improved the response to the cytotoxic agents, as viabilitiy drastically decreased.

Conclusion

We conclude that the use of non-oncologic drugs might greatly improve the response to standard chemotherapeutic agents in the treatment of breast cancer. Thus, patients suffering from breast cancer might profit from a combinatorial application of both minocycline as well as standard chemotherapeutic agents.

As minocycline targets several distinct cellular components, a deeply analysis is needed in order to evaluate the mechanisms underlying the improved response to cytotoxic agents.

Citation Format: Christof Bernemann, Ludwig Kiesel. Improvement of response to chemotherapy in breast cancer cells by the use of the non-oncologic drug minocycline. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3496. doi:10.1158/1538-7445.AM2015-3496

The anti-androgen drug dutasteride renders triple negative breast cancer cells more sensitive to chemotherapy via inhibition of HIF-1α-/VEGF-signaling

BACKGROUND

Triple negative breast cancer (TNBC) is characterized by lack of expression of both estrogen and progesterone receptor as well as lack of amplification of HER2. Patients with TNBC carry an unfavorable prognosis compared to other breast cancer subtypes given that endocrine or HER2 targeted therapies are not effective, rendering chemotherapy the sole effective treatment option to date. Therefore, there is a high demand for additional novel treatment options.

FINDINGS

We previously published a list of genes showing both higher gene expression rates in TNBC and, in addition, are known to encode targets of non-oncologic drugs. SRD5A1, which encodes the type-1 isoform of the steroid-5alpha-reductase, which is involved in androgen metabolism, was found to be one of these genes. Dutasteride is a dual blocker of both the type-1 and type-2 isoform of SRD5A1 and is indicated in the treatment of benign prostate hyperplasia. Treatment of TNBC cell lines with dutasteride was associated with a dose-dependent decrease in cell viability, altered protein expression of VEGF and HIF-1α and increased chemosensitivity.

CONCLUSION

Our results demonstrate that the SRD5A1-corresponding anti-androgenic drug dutasteride might act as a combinatorial therapeutic option besides standard chemotherapy in highly aggressive TNBC.

Abstract 2634: Direct reprogramming of tumor cells: a basis for novel therapeutic approaches

Introduction

Direct reprogramming describes a process by which differentiated cells can be converted into virtually any other cell type, including terminal differentiated cells. This breakthrough offers a chance for regenerative medicine in order to treat patients suffering from degenerative diseases like Parkinson disease or tissue damages.

We believe that direct reprogramming of tumor cells provides a basis for novel targeted therapies of aggressive tumors. These tumors could be reprogrammed into tumors of another, less aggressive subtype, that could potentially be treated more easily than the parental tumor does.

We used the most aggressive breast cancer subtype - triple negative breast cancer - as research model. Its missing expression of both hormone receptors (HR) as well as HER2 renders this subtype more aggressive compared to HR or HER2 positive tumors. It also implies its poorer prognosis compared to other breast cancer subtypes, for which targeted therapies are available, e.g. anti-HER2 therapies that drastically improved formerly poor prognosis of HER2 positive cancer to a much better prognostic subtype nowadays.

We suggest that by use of direct reprogramming of triple negative breast cancer cells into HER2 positive cancer cells, these cells are susceptible to anti-HER2 targeted therapies, shifting its poor prognosis into better prognosis.

Methods

Triple negative breast cancer cell lines were transduced using HER2 expressing lentiviral particles. Molecular biological analyses were performed to investigate the functionality of the transgene. Subsequently, targeted therapies against HER2 followed by molecular analyses of effects were performed.

Results

The expression of HER2 could be shown by both mRNA (using qPCR) as well as protein (Western Blot) approaches. Additionally, immunofluorescence analysis confirmed membrane localization of HER2.

Furthermore, preliminary results using targeted anti-HER2 therapies showed reduction of proliferative capacity of formerly triple negative breast cancer cells.

Conclusion

We conclude that direct reprogramming might become a tool of converting aggressive tumor types into cells susceptible to targeted therapies. Its current system describes a proof-of-principal whether reprogramming approaches might find a way into clinical settings someday. Nevertheless, strong hurdles have to be taken to make such approaches valuable for (breast) cancer patients.

Citation Format: Lena Bluemel, Carolin Huelsewig, Holm Zaehres, Hans Schoeler, Ludwig Kiesel, Christof Bernemann. Direct reprogramming of tumor cells: a basis for novel therapeutic approaches. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2634. doi:10.1158/1538-7445.AM2014-2634

Abstract 920: Secreted frizzled related protein 1 (SFRP1) as potential regulator of chemotherapy response for patients with triple negative breast cancer (TNBC)

Background: Triple negative breast cancer (TNBC) is associated with an unfavorable prognosis and increased response to chemotherapy. While proliferation rate and tumor grade are determining factors, we have recently suggested additional molecular structures to have significant impact.

Based on differential gene expression analysis we identified SFRP1 (secreted frizzled related protein 1) to be a potential molecular marker for response to chemotherapy and potential prognostic marker.

Methods: Differential gene expression analysis was performed between TNBC (n=27) versus non-TNBC (n=106) using AffymetrixU133A gene chips from breast cancers of patients treated with neoadjuvant taxane/anthracycline chemotherapy at MDACC (Hess et al. 2006). Differentially expressed genes were validated using profiles of 286 patients with breast cancer who did not receive systemic therapy (Wang et al. 2006). SFRP1 knockdown experiments with the TNBC cell line MDA-MB 468 were performed via siRNA transfection and carried out using assays for proliferation, chemo- and radioresistance. Results: SFRP1 was identified as differentially overexpressed gene in TNBC and successfully validated in the independent dataset. Protein and mRNA quantification of SFRP1 (TNBC vs. non-TNBC cell lines) confirm that. While in TNBC, SFRP1 expression showed no association with recurrence-free survival, it is significantly correlated with an increased sensitivity to neoadjuvant chemotherapy. siRNA-mediated knockdown of SFRP1 expression in MDA-MB 468 was associated with increased G2-arrested cells and importantly increased resistance to paclitaxel, doxorubicin and cis-platinum. Furthermore, radioresistance of MDA-MB 468 cells was significantly increased after SFRP1 knockdown. Interestingly, sensitivity to salinomycin was slightly increased after SFRP1 knockdown. Salinomycin is known to kill cancer stem cells (Gupta et al. 2009). Additionally, cancerous characteristics (invasion and migration) were increased after SFRP1 knockdown while target gene expression analysis revealed an association between loss of SFRP1 and activation of mTOR/PI3K signaling.

Conclusion: We suggest SFRP1 as a novel predictive marker of chemotherapy sensitivity to taxane, anthracycline and platinum-containing chemotherapy independent of Ki67 expression. Further on, we have shown the influence of SFRP1 on cancerous characteristics thus, suggesting SFRP1 as potential prognostic marker. Molecular role of SFRP1 may be the influence on enrichment of cancer stem cell population which are known to be resistant against chemotherapeutics and radiation and are usually slow proliferating. Interestingly, the mTOR/PI3K signaling might be activated via loss of SFRP1 which could display an opportunity for patients with TNBC resistant to current chemotherapeutics.

Citation Format: Carolin Huelsewig, Christof Bernemann, Christian Ruckert, Ludwig Kiesel, Martin Goette, Achim Rody, Lajos Pusztai, Georg Hempel, Cornelia Liedtke. Secreted frizzled related protein 1 (SFRP1) as potential regulator of chemotherapy response for patients with triple negative breast cancer (TNBC). [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 920. doi:10.1158/1538-7445.AM2014-920

Abstract LB-101: The antiandrogen drug dutasteride sensitizes triple negative breast cancer cells to chemotherapy via HIF-1α / VEGF-signaling

Background: Triple negative breast cancer is characterized by a lack of expression of both estrogen and progesterone receptor as well as lack of amplification of HER2. Patients with triple negative breast cancer carry an unfavorable prognosis compared to other breast cancer subtypes given that endocrine or HER-2 targeted therapies are not effective, rendering chemotherapy the sole effective treatment option to date.

In a previous work by Liedtke et al. ((Liedtke et al., Cancer Res 2009) we generated a list of genes, which showed higher expression in triple negative breast cancer and, in addition, are known to encode targets for known non-oncologic drugs. These gene products might represent targets for future therapies of triple negative breast cancer.

Results: We could identify SRD5A1, which encodes the type-1 isoform of the steroid-5-alpha-reductase, showing a higher expression in triple negative breast cancer both in vivo and in vitro. Dutasteride is a dual blocker of both the type-1 and type-2 isoform of SRD5A1 and is indicated in the treatment of benign prostate hyperplasia. Treatment of triple negative breast cancer cell lines with dutasteride was associated with a dose-dependent decrease in cell viability, altered protein expression of VEGF and HIF-1α and increased chemosensitivity.

Conclusion: Our results demonstrate that firstly, using differential gene expression analysis in clinically relevant breast cancer subtypes, potential new drug targets can be generated. Secondly, we identified the SRD5A1-corresponding anti androgenic drug dutasteride as a combinatorial therapeutic option besides standard chemotherapy in highly aggressive triple negative breast cancer.

Citation Format: Marie-Kristin von Wahlde, Carolin Huelsewig, Christian Ruckert, Martin Götte, Ludwig Kiesel, Cornelia Liedtke, Christof Bernemann. The antiandrogen drug dutasteride sensitizes triple negative breast cancer cells to chemotherapy via HIF-1α / VEGF-signaling. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-101. doi:10.1158/1538-7445.AM2014-LB-101

Influence of secreted frizzled receptor protein 1 (SFRP1) on neoadjuvant chemotherapy in triple negative breast cancer does not rely on WNT signaling

BACKGROUND

Triple negative breast cancer (TNBC) is characterized by lack of expression of both estrogen and progesterone receptor as well as lack of overexpression or amplification of HER2. Despite an increased probability of response to chemotherapy, many patients resistant to current chemotherapy regimens suffer from a worse prognosis compared to other breast cancer subtypes. However, molecular determinants of response to chemotherapy specific to TNBC remain largely unknown. Thus, there is a high demand for biomarkers potentially stratifying triple negative breast cancer patients for neoadjuvant chemotherapies or alternative therapies.

METHODS

In order to identify genes correlating with both the triple negative breast cancer subtype as well as response to neoadjuvant chemotherapy we employed publicly available gene expression profiles of patients, which had received neoadjuvant chemotherapy. Analysis of tissue microarrays as well as breast cancer cell lines revealed correlation to the triple negative breast cancer subtype. Subsequently, effects of siRNA-mediated knockdown on response to standard chemotherapeutic agents as well as radiation therapy were analyzed. Additionally, we evaluated the molecular mechanisms by which SFRP1 alters the carcinogenic properties of breast cancer cells.

RESULTS

SFRP1 was identified as being significantly overexpressed in TNBC compared to other breast cancer subtypes. Additionally, SFRP1 expression is significantly correlated with an increased probability of positive response to neoadjuvant chemotherapy. Knockdown of SFRP1 in triple negative breast cancer cells renders the cells more resistant to standard chemotherapy. Moreover, tumorigenic properties of the cells are modified by knockdown, as shown by both migration or invasion capacity as well reduced apoptotic events. Surprisingly, we found that these effects do not rely on Wnt signaling. Furthermore, we show that pro-apoptotic as well as migratory pathways are differentially regulated after SFRP1 knockdown.

CONCLUSION

We could firstly show that SFRP1 strongly correlates with the triple negative breast cancer subtype and secondly, that SFRP1 might be used as a marker stratifying patients to positively respond to neoadjuvant chemotherapy. The mechanisms by which tumor suppressor SFRP1 influences carcinogenic properties of cancer cells do not rely on Wnt signaling, thereby demonstrating the complexity of tumor associated signaling pathways.

Genomic profiling in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is defined by a lack of hormone receptor expression as well as lack of overexpression/amplification of HER2/neu. Patients with TNBC show a significantly worse prognosis compared to patients with other breast cancer subtypes. TNBC, however, is a heterogeneous entity both with regard to clinical/pathological characteristics and molecular biology. This review summarizes the current data on TNBC with a particular focus on mutational and gene expression profiling and the association between TNBC and breast cancer stem cells.

Abstract LB-211: Targeting triple negative breast cancer by using non-oncologic drug targets

Background:

Triple negative breast cancer (TNBC) is defined by the lack of estrogen-receptor alpha (ERα) and pro-gesterone receptor (PGR) expression as well as absence of human epidermal growth factor receptor2 (HER2/neu) overexpression. This type of breast cancer is characterized by a poor prognosis and sig-nificantly reduced survival rate compared to other breast cancer subtypes. This is mostly due to the lack of targeted agents like endocrine or anti HER2 targets.

Gene expression analysis revealed that different molecular targets are overexpressed in triple nega-tive breast cancer compared to other breast cancer subtypes. Therefore, these drug targets hold great potential for newly personalized therapeutic approaches in TNBC as well as other cancer types.

Methods:

Based on a list previously published (Liedtke et al., Cancer Res 2009) we defined the enzyme ALOX5 (arachidonate 5-lipoxygenase) as being a prominent new potential drug target. By using a set of known inhibitors of ALOX5 we deeply analyzed the effect on triple negative breast cancer cells as well as other breast cancer subtypes.

Results:

We firstly could show, that expression of ALOX5 correlates with the subtype of triple negative breast cancer, by trend. Treatment with meclofenamic acid additionally, showed significant decrease of proliferative capacity in at least some triple negative breast cancer cell lines.

Conclusion:

We could show that - in case of ALOX5 - its expression correlates with the triple negative breast cancer subtype by trend. Therefore, an inhibition of this molecular target might provoke anti prolife-rative effects on triple negative breast cancer cells. Actually, treatment with meclofenamic acid - a drug already used for joint, arthritis, muscular pain - showed reduction of proliferation in triplen negative breast cancer cells. Whether this effect relies on inhibition of ALOX5 or its function has to be analyzed further.

Citation Format: Christof Bernemann, Carolin Huelsewig, Marie-Kristin von Wahlde, Ludwig Kiesel, Cornelia Liedtke. Targeting triple negative breast cancer by using non-oncologic drug targets. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-211. doi:10.1158/1538-7445.AM2013-LB-211

Targeting triple-negative breast cancer by conversion into HER2-positive cancer: A novel therapeutic approach

e11534

Background: Triple negative breast cancer (TNBC) is defined by the lack of estrogen-receptor alpha (ERα) and progesterone receptor (PGR) expression as well as absence of human epidermal growth factor receptor2 (HER2/neu) overexpression. This type of breast cancer is characterized by a poor prognosis and significantly reduced survival rate compared to other BC subtypes. This is mostly due to the lack of targeted agents like endocrine or anti HER2 targets. Breast cancers which overexpress HER2 are usually treated by chemicals targeting HER2; either by blocking the extracellular domain through trastuzumab or the intracellular domain through the small molecule lapatinib. Both therapeutics lead to inhibition of downstream pathways like MAPK and PI3K, resulting in increased apoptosis as well as reduced proliferation. Methods: We hypothesize that downstream effects might be induced in TNBC cells when HER2 is artificially overexpressed and cells get treated as HER2 positive cells. Therefore, triple negative breast cancer cell lines were transfected with HER2. These cells were treated with anti-HER2 agents. Molecular analyses will demonstrate whether transfection with HER2 will yield a HER2 positive breast cancer phenotype in that all downstream signaling mechanisms act similarly to a priori HER2 positive cells. Results: Preliminary experiments suggest that proliferation of TNBC cells transfected with HER2 does not change significantly. Treatment with HER2-blocking antibody trastuzumab leads to significant decrease of proliferation in HER2 transfected, initially triple negative MDA-MB-231 breast cancer cells. Only a moderate decrease in proliferation was observed when lapatinib, a molecule directed against both EGFR and HER2, was used in both MDA-MB-231 wildtype and HER2-transfected cell lines. Conclusions: We surmise that firstly, conversion of cancer might become a clinical tool to treat cancer of poor prognosis and secondly that our results might shed light on future therapeutic approaches e.g. small molecule compound screening for endogenous HER2 reactivation / overexpression and subsequent targeted treatment of triple negative breast cancers.

Abstract 1198: Conversion of triple negative breast cancer cells into HER2 positive cells - a novel therapeutic approach

Introduction: Triple negative breast cancer (TNBC) is defined by the lack of estrogen-receptor alpha (ERα) and progesterone receptor (PGR) expression as well as absence of human epidermal growth factor receptor2 (HER2/neu) overexpression. This type of breast cancer is characterized by a poor prognosis and significantly reduced survival rate compared to other breast cancer subtypes. This is mostly due to the lack of targeted agents like endocrine or anti HER2 targets. Breast cancers which express HER2 are usually treated by chemicals targeting the human epidermal growth factor receptor; either by blocking the extracellular domain of HER2 through trastuzumab or the intracellular domain of HER2 through the small molecule lapatinib. Both therapeutics lead to inhibition of downstream signaling pathways like MAPK and PI3K signaling, resulting in increased apoptosis as well as reduced proliferation. Methods: We hypothesize that downstream effects e.g. reduced proliferation or apoptosis might be induced in triple negative breast cancer cells when HER2 is artificially overexpressed by transfection and cells get treated as HER2 positive cells. Therefore, triple negative breast cancer cell lines were stably transfected with HER2. These cells will be treated with anti-HER2 agents. Molecular analyses will demonstrate whether transfection with HER2 will yield a HER2 positive breast cancer phenotype in that all downstream signaling mechanisms act similarly to a priori HER2 positive cells. Results: Preliminary experiments suggest that proliferation of breast cancer cells transfected with HER2 does not change significantly. Treatment with HER2-specifically blocking antibody trastuzumab leads to significant decrease of proliferation in HER2 transfected, initially triple negative MDA-MB-231 breast cancer cells. Only a moderate decrease in proliferation was observed when lapatinib, a small molecule directed against both EGFR and HER2, was used in both MDA-MB-231 wildtype and HER2-transfected cell lines. Additional results will be presented. Conclusion: We surmise that firstly, transdifferentiation of cancer might become a clinical tool to treat cancer of poor prognosis and secondly that our results might shed light on future therapeutic approaches e.g. small molecule compound screening for endogenous HER2 reactivation / overexpression and subsequent targeted treatment of cancers.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1198. doi:1538-7445.AM2012-1198

Distinct developmental ground states of epiblast stem cell lines determine different pluripotency features

Epiblast stem cells (EpiSCs) are pluripotent stem cells derived from mouse postimplantation embryos at embryonic day (E) 5.5-E7.5 at the onset of gastrulation, which makes them a valuable tool for studying mammalian postimplantation development in vitro. EpiSCs can also be reprogrammed into a mouse embryonic stem cell (mESC)-like state. Some reports have shown that the reversion of EpiSCs requires transcription factor overexpression, whereas others have suggested that use of stringent mESC culture conditions alone is sufficient for the reversion of EpiSCs. To clarify these discrepancies, we systematically compared a panel of independent EpiSC lines. We found that--regardless of the embryonic day of derivation--the different EpiSC lines shared a number of defining characteristics such as the ability to form teratomas. However, despite use of standard EpiSC culture conditions, some lines exhibited elevated expression of genes associated with mesendodermal differentiation. Pluripotency (Oct4) and mesodermal (Brachyury) marker genes were coexpressed in this subset of lines. Interestingly, the expression of mesendodermal marker genes was negatively correlated with the cells' ability to efficiently undergo neural induction. Moreover, these mesodermal marker gene-expressing cell lines could not be efficiently reverted to an mESC-like state by using stringent mESC culture conditions. Conversely, Brachyury overexpression diminished the reversion efficiency in otherwise Brachyury-negative lines. Overall, our data suggest that different EpiSC lines may undergo self-renewal into distinct developmental states, a finding with important implications for functional readouts such as reversion of EpiSCs to an mESC-like state as well as directed differentiation.

An RNA interference phenotypic screen identifies a role for FGF signals in colon cancer progression

In tumor cells, stepwise oncogenic deregulation of signaling cascades induces alterations of cellular morphology and promotes the acquisition of malignant traits. Here, we identified a set of 21 genes, including FGF9, as determinants of tumor cell morphology by an RNA interference phenotypic screen in SW480 colon cancer cells. Using a panel of small molecular inhibitors, we subsequently established phenotypic effects, downstream signaling cascades, and associated gene expression signatures of FGF receptor signals. We found that inhibition of FGF signals induces epithelial cell adhesion and loss of motility in colon cancer cells. These effects are mediated via the mitogen-activated protein kinase (MAPK) and Rho GTPase cascades. In agreement with these findings, inhibition of the MEK1/2 or JNK cascades, but not of the PI3K-AKT signaling axis also induced epithelial cell morphology. Finally, we found that expression of FGF9 was strong in a subset of advanced colon cancers, and overexpression negatively correlated with patients' survival. Our functional and expression analyses suggest that FGF receptor signals can contribute to colon cancer progression.

Neural induction intermediates exhibit distinct roles of Fgf signaling

Formation of the neural plate is an intricate process in early mammalian embryonic development mediated by cells of the inner cell mass and involving a series of steps, including development of the epiblast. Here, we report on the creation of an embryonic stem (ES) cell-based system to isolate and identify neural induction intermediates with characteristics of epiblast cells and neural plate. We demonstrate that neural commitment requires prior differentiation of ES cells into epiblast cells that are indistinguishable from those derived from natural embryos. We also demonstrate that epiblast cells can be isolated and cultured as epiblast stem cell lines. Fgf signaling is shown to be required for the differentiation of ES cells into these epiblast cells. Fgf2, widely used for maintenance of both human ES cells and epiblast stem cells, inhibits formation of early neural cells by epiblast intermediates in a dose-dependent manner and is sufficient to promote transient self-renewal of epiblast stem cells. In contrast, Fgf8, the endogenous embryonic neural inducer, fails to promote epiblast self-renewal, but rather promotes more homogenous neural induction with transient self-renewal of early neural cells. Removal of Fgf signaling entirely from epiblast cells promotes rapid neural induction and subsequent neurogenesis. We conclude that Fgf signaling plays different roles during the differentiation of ES cells, with an initial requirement in epiblast formation and a subsequent role in self-renewal. Fgf2 and Fgf8 thus stimulate self-renewal in different cell types.

Epiblast stem cell subpopulations represent mouse embryos of distinct pregastrulation stages

Embryonic stem cells (ESCs) comprise at least two populations of cells with divergent states of pluripotency. Here, we show that epiblast stem cells (EpiSCs) also comprise two distinct cell populations that can be distinguished by the expression of a specific Oct4-GFP marker. These two subpopulations, Oct4-GFP positive and negative EpiSCs, are capable of converting into each other in vitro. Oct4-GFP positive and negative EpiSCs are distinct from ESCs with respect to global gene expression pattern, epigenetic profile, and Oct4 enhancer utilization. Oct4-GFP negative cells share features with cells of the late mouse epiblast and cannot form chimeras. However, Oct4-GFP positive EpiSCs, which only represent a minor EpiSC fraction, resemble cells of the early epiblast and can readily contribute to chimeras. Our findings suggest that the rare ability of EpiSCs to contribute to chimeras is due to the presence of the minor EpiSC fraction representing the early epiblast.

Conserved and divergent roles of FGF signaling in mouse epiblast stem cells and human embryonic stem cells

Mouse epiblast stem cells (EpiSCs) are cultured with FGF2 and Activin A, like human embryonic stem cells (hESCs), but the action of the associated pathways in EpiSCs has not been well characterized. Here, we show that activation of the Activin pathway promotes self-renewal of EpiSCs via direct activation of Nanog, whereas inhibition of this pathway induces neuroectodermal differentiation, like in hESCs. In contrast, the different roles of FGF signaling appear to be only partially conserved in the mouse. Our data suggest that FGF2 fails to cooperate with SMAD2/3 signaling in actively promoting EpiSC self-renewal through Nanog, in contrast to its role in hESCs. Rather, FGF appears to stabilize the epiblast state by dual inhibition of differentiation to neuroectoderm and of media-induced reversion to a mouse embryonic stem cell-like state. Our data extend the current model of cell fate decisions concerning EpiSCs by clarifying the distinct roles played by FGF signaling.