[The impact of the androgen receptor splice variant AR-V7 on the prognosis and treatment of advanced prostate cancer]

A recently discovered mechanism enabling prostate cancer cells to escape the effects of endocrine therapies consists in the synthesis of C-terminally truncated, constitutively active androgen receptor (AR) splice variants (AR-V). Devoid of a functional C-terminal hormone/ligand binding domain, various AR-Vs are insensitive to therapies targeting the androgen/AR signalling axis. Preliminary studies suggest that AR-V7, the most common AR-V, is a promising predictive tumour marker and a relevant selection marker for the treatment of advanced prostate cancer. This review critically outlines recent advances in AR-V7 diagnostics and presents an overview of current AR-V7 targeted therapies.

Role of androgen receptor splice variants, their clinical relevance and treatment options

PURPOSE

In this review, we summarize the importance of AR variants with a particular focus on clinically relevant members of this family.

METHODS

A non-systematic literature review was performed based on Medline and PubMed.

RESULTS

Endocrine therapy represents the central paradigm for the management of prostate cancer. Eventually, in response to androgen ablation therapy, several resistance mechanisms against the endocrine therapy might develop that can circumvent the therapy approaches. One specific resistance mechanism that has gained increasing attention is the generation of alternatively spliced variants of the androgen receptor, with AR-V7 being the most prominent. More broadly, AR-V7 is one member of a group of alternatively spliced AR variants that share a common feature, the missing ligand-binding domain. These ΔLBD androgen receptor variants have shown the capability to induce androgen receptor-mediated gene transcription even under conditions of androgen deprivation and to drive cancer progression.

CONCLUSION

The methods used for detecting AR-Vs, at least on the mRNA level, are well-advanced and harbor the potential to be introduced into clinical diagnostics. It is important to note, that the testing, especially of AR-V7 has its limitations in predicting treatment response. More promising is the great number of active clinical trials aimed at reducing the AR-Vs, and using this to re-sensitize CRPC towards endocrine treatment might provide additional treatment options for CRPC patients in the future.

Neuropilin-2 and its ligand VEGF-C predict treatment response after transurethral resection and radiochemotherapy in bladder cancer patients

The standard treatment for invasive bladder cancer is radical cystectomy. In selected patients, bladder-sparing therapy can be performed by transurethral resection (TURBT) and radio-chemotherapy (RCT) or radiotherapy (RT). Our published in vitro data suggest that the Neuropilin-2 (NRP2)/VEGF-C axis plays a role in therapy resistance. Therefore, we studied the prognostic impact of NRP2 and VEGF-C in 247 bladder cancer patients (cN0M0) treated with TURBT and RCT (n = 198) or RT (n = 49) and a follow-up time up to 15 years. A tissue microarray was analyzed by immunohistochemistry. NRP2 expression emerged as a prognostic factor in overall survival (OS; HR: 3.42; 95% CI: 1.48 - 7.86; p = 0.004) and was associated with a 3.85-fold increased risk of an early cancer specific death (95% CI: 0.91 - 16.24; p = 0.066) in multivariate analyses. Cancer specific survival (CSS) dropped from 166 months to 85 months when NRP2 was highly expressed (p = 0.037). Patients with high VEGF-C expression have a 2.29-fold increased risk of shorter CSS (95% CI: 1.03-5.35; p = 0.043) in univariate analysis. CSS dropped from 170 months to 88 months in the case of high VEGF-C expression (p = 0.041). Additionally, NRP2 and VEGF-C coexpression is a prognostic marker for OS in multivariate models (HR: 7.54; 95% CI: 1.57-36.23; p = 0.012). Stratification for muscle invasiveness (T1 vs. T2-T4) confirmed the prognostic role of NRP2 and NRP2/VEGF-C co-expression in patients with T2-T4 but also with high risk T1 disease. In conclusion, immunohistochemistry for NRP2 and VEGF-C has been determined to predict therapy outcome in bladder cancer patients prior to TURBT and RCT.

Morphological and molecular characterization of an undifferentiated soft tissue sarcoma cell line and derivative clones

From an undifferentiated soft tissue sarcoma (STS) a cell line designated US8-93 has been established. At subcloning the cell line US8-93 three different lines (US8-93A, B and C) could be set up. In a subsequent study characteristics for ultrastructure, growth, cell cycle distribution, karyotype, protein overexpression detected by immunohistochemistry (IHC) and p53 mutational status were determined. The cell line US8-93 as well as subclones contain mainly bipolar spindle-shaped cells and additionally some polygonal and multinucleated cells. Cells possess the characteristics of primitive mesenchymal cells based on their positive reactions with anti-vimentin and negative reactions for desmin, cytokeratin, myoglobin, S100, and NSE, implying a classification as an undifferentiated STS. Cytogenetic analysis revealed nearly diploid cells with several structural and numerical aberrations for chromosomes 1, 3, 4, 6, 9, 10, 12, 13, 15 and 18. IHC positivity was found for the tumor suppressor proteins p53 and Rb, the oncogene products Bcl-2, K-ras, N-ras, P-glycoprotein Mdr-1 and MDM-2. In the p53 gene a nonsense mutation in exon 4 was detected, that was confirmed in the original primary tumor and in three derivative clonal lines. The described STS cell line represents a valuable supplementation to the relatively small number of human STS cell lines currently available and may also provide a good in vitro model for studies of STS tumorigenesis in respect to a mutated p53 gene.

Radiation induced G2/M block and apoptosis in two human sarcoma cell lines with different p53 gene status

We investigated a wild-type (wt) p53 rhabdomyosarcoma (A-204) and a mutated (mt p53) undifferentiated sarcoma cell line (US8-93) for their response to X-rays. The observation period was 0 to 96 h after irradiation. Both cell lines showed a strikingly delayed G2/M arrest and an induction of apoptosis after irradiation. Compared with the cell line A-204 (wt p53), the cell line US8-93 (mt p53) revealed a stronger G2/M arrest. In agreement with this, in terms of viability as well as the rate of apoptosis, A-204 (wt p53) showed a stronger response to irradiation than US8-93 (mt p53). We suggest that the different p53 gene status might be the cause for a different response to irradiation.

The tumor suppressor RASSF10 is upregulated upon contact inhibition and frequently epigenetically silenced in cancer

The Ras association domain family (RASSF) comprises a group of tumor suppressors that are frequently epigenetically inactivated in various tumor entities and linked to apoptosis, cell cycle control and microtubule stability. In this work, we concentrated on the newly identified putative tumor suppressor RASSF10. Methylation analysis reveals RASSF10 promoter hypermethylation in lung cancer, head and neck (HN) cancer, sarcoma and pancreatic cancer. An increase in RASSF10 methylation from normal tissues, primary tumors to cancer cell lines was observed. Methylation was reversed by 5-aza-2'-deoxycytidine treatment leading to reexpression of RASSF10. We further show that overexpression of RASSF10 suppresses colony formation in cancer cell lines. In addition, RASSF10 is upregulated by cell-cell contact and regulated on promoter level as well as endogenously by forskolin, protein kinase A (PKA) and activator Protein 1 (AP-1), linking RASSF10 to the cAMP signaling pathway. Knockdown of the AP-1 member JunD interfered with contact inhibition induced RASSF10 expression. In summary, we found RASSF10 to be epigenetically inactivated by hypermethylation of its CpG island promoter in lung, HN, sarcoma and pancreatic cancer. Furthermore, our novel findings suggest that tumor suppressor RASSF10 is upregulated by PKA and JunD signaling upon contact inhibition and that RASSF10 suppresses growth of cancer cells.

Correlation of expression of hypoxia-related proteins with prognosis in oral squamous cell carcinoma patients

INTRODUCTION

Hypoxia plays a major role in tumor progression, therapy resistance and for prognosis of oral squamous cell carcinoma (OSCC). The crucial step as a response to hypoxia is the activation and stabilization of the alpha subunit of hypoxia inducible factor 1 (HIF-1α). HIF-1: HIF-1 regulates the expression of different genes to adapt the tumor cells to reduced oxygenation. The HIF-1 system is intrinsic regulated by von Hippel-Lindau protein (pVHL). Main downstream proteins are the glucose transporter 1 (GLUT-1), carbonic anhydrase IX (CAIX), and vascular endothelial growth factor (VEGF). For therapeutical stratification in OSCC, it is important to understand the mechanism caused by hypoxic stress and to comprehend the resulting adaptive process in cancer cells. Therefore, an overview of HIF-1α-depending protein expression, focussed on the expression of GLUT-1, CAIX, and VEGF and their prognostic significance in OSCC is given.

CONCLUSION

Several unique roles of hypoxic pathway in the context of tumor progression are described in this review. As a consequence, a marker panel is proposed to allow a more individualized prognosis in OSCC patients. This marker panel should include beside HIF-1α, pVHL, and GLUT-1.

Expression of microRNA 210 associates with poor survival and age of tumor onset of soft-tissue sarcoma patients

Expression of microRNAs can affect age of tumor onset and prognosis of cancer patients. However, nothing is known about the effects of microRNAs on altered age of cancer onset and disease-specific survival of soft-tissue sarcoma (STS) patients. The levels of miR-210, also known as hypoxia-regulated microRNA, were analyzed by quantitative real-time (RT)-PCR in the tumors of 78 STS patients. The patients were stratified according to their microRNA levels with low, intermediate and high expression levels and the association of microRNA expression and patients' survival was analyzed using multivariate Cox's regression hazard analyses. A significant correlation between an intermediate miR-210 expression and disease-specific death of STS patients [relative risk (RR) = 3.19; p = 0.018] was observed compared with patients with high expression levels in their tumors. Interestingly, the association between an intermediate expression of miR-210 and a poor prognosis was only significant in female STS patients (RR = 11.28; p = 0.010), but not observed in male individuals. Furthermore, the expression of miR-210 showed a significant association with the age of tumor onset in a gender-specific manner. Specifically, male patients with an intermediate expression of miR-210 associated with a 9.6-year later age of tumor onset (p = 0.017) compared with males with a low expression of miR-210 in their tumors. However, no significant differences in the female patients were observed. This study provides the first evidence of a correlation of expression levels of a single microRNA (miR-210) with the prognosis and age of tumor onset in a gender-specific manner in STS patients.

Co-detection of members of the urokinase plasminogen activator system in tumour tissue and serum correlates with a poor prognosis for soft-tissue sarcoma patients

Background:

The urokinase plasminogen activator (uPA) system is one of the best-investigated protease systems, both under physiological and pathological conditions, including various types of cancer. However, effects of co-expression of members of the uPA system in soft-tissue sarcoma (STS) patients at the protein level in both tumour tissue and serum have not been investigated yet.

Methods:

We examined 82 STS patients for protein levels of uPA, PAI-1and uPAR in tumour tissue and serum by ELISA.

Results:

A significant correlation between high antigen levels of uPA, PAI-1 or uPAR in tumour tissue, and of uPAR in serum, with poor outcome of STS patients was found for the first time. Most strikingly, we observed an additive effect of combined uPA, PAI-1 or uPAR levels in tumour tissue extracts with uPAR levels in serum on patients’ prognosis. High uPA/uPAR, PAI-1/uPAR and uPAR/uPAR antigen levels in tumour tissue/serum were associated with a 5.9-fold, 5.8-fold and 6.2-fold increased risk of tumour-related death (P=0.003, 0.001 and 0.002, respectively) compared with those patients who displayed low levels of the respective marker combination.

Conclusion:

As expression of members of the uPA system in tumour tissue and serum is additively correlated with prognosis of STS patients, our results suggest that combinations of these biomarkers can identify STS patients with a higher risk of tumour-related death.

Co-expression of Hif1alpha and CAIX is associated with poor prognosis in oral squamous cell carcinoma patients

BACKGROUND

This study investigates the prognostic impact of the expression of hypoxia-inducible factor 1alpha (Hif1alpha) and carbonic anhydrase IX (CAIX) detected by immunohistochemistry in oral squamous cell carcinoma (OSCC).

METHODS

Statistical analysis of immunohistochemical results with clinical parameters including survival outcomes was performed for 80 OSCC patients.

RESULTS

Patients with a low expression of both proteins survived on average 54.8 months, whereas those with an increased expression of Hif1alpha in their tumors combined with a low expression of CAIX survived on average only 37.6 months (P = 0.026). In multivariate Cox's regression hazard analysis, again patients with a low expression of Hif1alpha/CAIX had the best prognosis, whereas patients with increased Hif1alpha and low CAIX expression carried a 4.97-fold increased risk of tumor-related death (P = 0.042).

CONCLUSION

A co-detection of low Hif1alpha/CAIX expression is significantly correlated with a better prognosis for OSCC patients, which may have implications for therapy options for these patients.

Expression of Glut-1 is a prognostic marker for oral squamous cell carcinoma patients

Oral squamous cell carcinoma (OSCC) is among the tenth most common human cancers worldwide with evidence of an increase in incidence rate and mortality. Despite advances in treatment modalities, the prognosis of this cancer is still very poor and has not changed over the past two decades. This study is based on samples collected from 42 patients with a primary OSCC. Immunohistochemical staining for Glut-1 was carried out and compared with the clinicopathological data. Thirty-two patients showed in their tumors a weak or undetectable Glut-1 expression, whereas in tumors of 10 patients a moderate to strong Glut-1 expression was detected. In multivariate Cox's regression hazard analysis, patients whose tumors had a moderate to strong Glut-1 expression possessed a 4.9-fold increased risk of tumor-related death compared to the other patients. Our results suggest that Glut-1 expression is an independent prognostic marker for routine assessment of OSCC.

The effects of knockdown of wild-type survivin, survivin-2B or survivin-delta3 on the radiosensitization in a soft tissue sarcoma cells in vitro under different oxygen conditions

The inhibitor of apoptosis wild-type survivin is a multifunctional protein that suppresses apoptosis and regulates cell cycle progression. An association between wild-type survivin expression and radiosensitivity has been described in different tumor cells. The effects of siRNA-induced knockdown of wild-type survivin and survivin-splice variants survivin-2B and survivin-Delta3 were investigated under normoxic and hypoxic conditions in the human sarcoma cell line US 8-93 (mutant p53). Inhibition of the survivin isoforms by siRNA resulted in a decrease of target mRNA down to 14-70% compared to cells treated with control siRNA independent of the oxygen level. The mRNA expression of survivin isoforms was decreased by the factor of 1-12 when the cells were cultivated under hypoxic conditions. Moreover, the knockdown of wild-type survivin reduced colony formation independent of oxygen concentration down to 70% and induced formation of polyploid cells. Less reduction of plating efficiency was observed after specific knockdown of survivin-2B and survivin-Delta3 under hypoxic or normoxic conditions. A knockdown of wild-type survivin, survivin-Delta3 and survivin-2B isoforms in combination with irradiation caused no radiosensitization in cell line US 8-93, neither under hypoxic nor under normoxic conditions tested in the colony-forming assay. However, knockdown of wild-type survivin caused radiosensitization in the megacolony assay.

Are overexpressed alternative survivin transcripts in human bladder cancer suitable targets for siRNA-mediated in vitro inhibition?

In order to reduce side effects of survivin-inhibiting anticancer therapies, we determined the expression of the survivin transcripts survivin-wild-type (survivin-wt), survivin-DeltaEx3 (DeltaEx3) and survivin-2B (2B) in cryo-preserved tumor and non-malignant bladder tissues (18 tumor and 22 non-malignant samples, including 17 autologous tissue pairs) by quantitative PCR. Furthermore, we investigated the biological effects following specific inhibition of the alternative transcripts DeltaEx3 and 2B in bladder cancer (BCa) cells. In BCa and non-malignant bladder tissues survivin-wt was the quantitatively dominant transcript followed by DeltaEx3 and 2B. The mean mRNA expression of DeltaEx3 (0.37 vs. 0.06 zmol/amol GAPDH, respectively) and 2B (0.13 vs. 0.01 zmol/amol GAPDH, respectively) was significantly higher in BCa compared to non-malignant bladder tissues, indicating their accessibility for an expression inhibition in BCa cells. Effective and long-lasting small interfering RNA-mediated inhibition of one alternative survivin transcript caused lower cell growth reduction effects (apoptosis induction, cell cycle arrest, colony formation) compared to simultaneous inhibition of multiple survivin transcripts including survivin-wt. Inhibition of one alternative survivin transcript increased the apoptosis rate by 11% vs. 33-46% when reducing several survivin transcripts. We observed no G2/M arrest or reduction of cell colony formation after inhibiting one alternative survivin transcript. Reduction of cell viability by the chemotherapeutics cisplatin, mitomycin C or gemcitabine was stronger in combination with inhibition of several survivin transcripts than in combination with the reduction of one alternative survivin splice variant. Furthermore, reducing one alternative transcript caused chemosensitization to only one chemotherapeutic agent in contrast to inhibition of several survivin transcripts. Therefore, the alternative survivin transcripts DeltaEx3 and 2B do not represent reasonable targets for anticancer, at least BCa, treatment.