High-resolution array-based comparative genomic hybridization of bladder cancers identifies mouse double minute 4 (MDM4) as an amplification target exclusive of MDM2 and TP53

TNBC response to paclitaxel phenocopies interferon response which reveals cell cycle-associated resistance mechanisms

Paclitaxel is a standard of care neoadjuvant therapy for patients with triple negative breast cancer (TNBC); however, it shows limited benefit for locally advanced or metastatic disease. Here we used a coordinated experimental-computational approach to explore the influence of paclitaxel on the cellular and molecular responses of TNBC cells. We found that escalating doses of paclitaxel resulted in multinucleation, promotion of senescence, and initiation of DNA damage induced apoptosis. Single-cell RNA sequencing (scRNA-seq) of TNBC cells after paclitaxel treatment revealed upregulation of innate immune programs canonically associated with interferon response and downregulation of cell cycle progression programs. Systematic exploration of transcriptional responses to paclitaxel and cancer-associated microenvironmental factors revealed common gene programs induced by paclitaxel, IFNB, and IFNG. Transcription factor (TF) enrichment analysis identified 13 TFs that were both enriched based on activity of downstream targets and also significantly upregulated after paclitaxel treatment. Functional assessment with siRNA knockdown confirmed that the TFs FOSL1, NFE2L2 and ELF3 mediate cellular proliferation and also regulate nuclear structure. We further explored the influence of these TFs on paclitaxel-induced cell cycle behavior via live cell imaging, which revealed altered progression rates through G1, S/G2 and M phases. We found that ELF3 knockdown synergized with paclitaxel treatment to lock cells in a G1 state and prevent cell cycle progression. Analysis of publicly available breast cancer patient data showed that high ELF3 expression was associated with poor prognosis and enrichment in programs associated with cell cycle progression. Together these analyses disentangle the diverse aspects of paclitaxel response and identify ELF3 upregulation as a putative biomarker of paclitaxel resistance in TNBC.

Cellular, Structural Basis, and Recent Progress for Targeting Murine Double Minute X (MDMX) in Tumors

Murine double minute X (MDMX) is an oncoprotein that mainly has a negative regulatory effect on the tumor suppressor p53 to induce tumorigenesis. As MDMX is highly expressed in various types of tumor cells, targeting and inhibiting MDMX are becoming a promising strategy for treating cancers. However, the high degree of structural homology between MDMX and its homologous protein murine double minute 2 (MDM2) is a great challenge for the development of MDMX-targeted therapies. This review introduces the structure, distribution, and regulation of the MDMX, summarizes the structural features and structure-activity relationships (SARs) of MDMX ligands, and focuses on the differences between MDMX and MDM2 in these aspects. Our purpose of this work is to propose potential strategies to achieve the specific targeting of MDMX.

TNBC response to paclitaxel phenocopies interferon response which reveals cell cycle-associated resistance mechanisms

Paclitaxel is a standard of care neoadjuvant therapy for patients with triple negative breast cancer (TNBC); however, it shows limited benefit for locally advanced or metastatic disease. Here we used a coordinated experimental-computational approach to explore the influence of paclitaxel on the cellular and molecular responses of TNBC cells. We found that escalating doses of paclitaxel resulted in multinucleation, promotion of senescence, and initiation of DNA damage induced apoptosis. Single-cell RNA sequencing (scRNA-seq) of TNBC cells after paclitaxel treatment revealed upregulation of innate immune programs canonically associated with interferon response and downregulation of cell cycle progression programs. Systematic exploration of transcriptional responses to paclitaxel and cancer-associated microenvironmental factors revealed common gene programs induced by paclitaxel, IFNB, and IFNG. Transcription factor (TF) enrichment analysis identified 13 TFs that were both enriched based on activity of downstream targets and also significantly upregulated after paclitaxel treatment. Functional assessment with siRNA knockdown confirmed that the TFs FOSL1, NFE2L2 and ELF3 mediate cellular proliferation and also regulate nuclear structure. We further explored the influence of these TFs on paclitaxel-induced cell cycle behavior via live cell imaging, which revealed altered progression rates through G1, S/G2 and M phases. We found that ELF3 knockdown synergized with paclitaxel treatment to lock cells in a G1 state and prevent cell cycle progression. Analysis of publicly available breast cancer patient data showed that high ELF3 expression was associated with poor prognosis and enrichment programs associated with cell cycle progression. Together these analyses disentangle the diverse aspects of paclitaxel response and identify ELF3 upregulation as a putative biomarker of paclitaxel resistance in TNBC.

Single-cell RNA sequencing reveals the cellular and molecular characteristics of high-grade and metastatic bladder cancer

PURPOSE

Metastatic bladder cancer (BC) has the highest somatic mutation frequency and recurrence rate of all tumors. However, the cellular and molecular characteristics of BC remain unclear.

METHODS

We performed single-cell RNA sequencing (scRNA-seq) on the samples of paracancerous normal tissue (PNT), primary tumor (PT) and lymph node metastasis (LNM). The proportions and gene expression profiles of different cell types in the tumor microenvironment (TME) were investigated.

RESULTS

In total, 50,158 cells were classified into six populations. Malignant cells of PT and LNM exhibited large mutant DNA fragments, while the cell phenotypes and gene expression profiles differed during differentiation. Metastasis was associated with a poorer prognosis than PT. Tumor-associated stromal cells and inhibitory immune cells were the main cell populations in PT and LNM. Cell-cell communication analysis revealed the roles of signaling pathways of inflammatory cancer-associated fibroblast (iCAF) and tumor-associated macrophage (TAM) in exhaustion of T cells. In addition, iCAF may recruit TAM to promote formation of the TME earlier than the differentiation of tumor cells.

CONCLUSION

This study through scRNA-seq enhanced our understanding of new features about the cellular and molecular similarities and differences of high-grade and metastatic bladder cancer, which might provide potential therapeutic targets in future treatment.

Targeting MDMX for Cancer Therapy: Rationale, Strategies, and Challenges

The oncogene MDMX, also known as MDM4 is a critical negative regulator of the tumor suppressor p53 and has been implicated in the initiation and progression of human cancers. Increasing evidence indicates that MDMX is often amplified and highly expressed in human cancers, promotes cancer cell growth, and inhibits apoptosis by dampening p53-mediated transcription of its target genes. Inhibiting MDMX-p53 interaction has been found to be effective for restoring the tumor suppressor activity of p53. Therefore, MDMX is becoming one of the most promising molecular targets for developing anticancer therapeutics. In the present review, we mainly focus on the current MDMX-targeting strategies and known MDMX inhibitors, as well as their mechanisms of action and in vitro and in vivo anticancer activities. We also propose other potential targeting strategies for developing more specific and effective MDMX inhibitors for cancer therapy.

The Role of ISL1 and LHX5 LIM Homeobox Genes in Bladder Tumourigenesis

Introduction

Lin-11, Isl-1 and Mec-3 domains (LIM) homeobox genes are among the most important sub-families of homeobox genes. These genes are thought to play an important role in cancer. In this study, the protein expression of these genes was examined in urothelial carcinoma of the bladder. The expression pattern of Islet-1 (ISL1) and LIM homeobox 5 (LHX5) across different cancer stages and grades, as well as the association between the protein expression of these genes and patient demographics and clinicopathological features, were examined.

Methods

A total of 100 formalin-fixed paraffin-embedded urothelial carcinoma tissues were selected from the Department of Pathology, Hospital Kuala Lumpur and the protein expression of ISL1 and LHX5 was determined using immunohistochemistry.

Results

Positive expression of ISL1 and LHX5 was detected in 94% and 98% of the samples, respectively. There were no distinct LHX5 expression patterns associated with different cancer stages, but the proportion of high-expressing tumours was higher in high-grade tumours. In addition, there was a significant association between the expression of LHX5 and tumour grade. The proportion of tumours expressing high levels of ISL1 was found to be highest in later stage tumours.

Conclusion

The high percentage of tumours expressing both these genes suggests that ISL1 and LHX5 play an important role in bladder tumourigenesis across multiple stages.

Gene and protein analysis reveals that p53 pathway is functionally inactivated in cytogenetically normal Acute Myeloid Leukemia and Acute Promyelocytic Leukemia

Background

Mechanisms that inactivate the p53 pathway in Acute Myeloid Leukemia (AML), other than rare mutations, are still not well understood.

Methods

We performed a bioinformatics study of the p53 pathway function at the gene expression level on our collection of 1153 p53-pathway related genes. Publically available Affymetrix data of 607 de-novo AML patients at diagnosis were analyzed according to the patients cytogenetic, FAB and molecular mutations subtypes. We further investigated the functional status of the p53 pathway in cytogenetically normal AML (CN-AML) and Acute Promyelocytic Leukemia (APL) patients using bioinformatics, Real-Time PCR and immunohistochemistry.

Results

We revealed significant and differential alterations of p53 pathway-related gene expression in most of the AML subtypes. We found that p53 pathway-related gene expression was not correlated with the accepted grouping of AML subtypes such as by cytogenetically-based prognosis, morphological stage or by the type of molecular mutation. Our bioinformatic analysis revealed that p53 is not functional in CN-AML and APL blasts at inducing its most important functional outcomes: cell cycle arrest, apoptosis, DNA repair and oxidative stress defense. We revealed transcriptional downregulation of important p53 acetyltransferases in both CN-AML and APL, accompanied by increased Mdmx protein expression and inadequate Chk2 protein activation.

Conclusions

Our bioinformatic analysis demonstrated that p53 pathway is differentially inactivated in different AML subtypes. Focused gene and protein analysis of p53 pathway in CN-AML and APL patients imply that functional inactivation of p53 protein can be attributed to its impaired acetylation. Our analysis indicates the need in further accurate evaluation of p53 pathway functioning and regulation in distinct subtypes of AML.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-017-0249-2) contains supplementary material, which is available to authorized users.

Opposite regulation of MDM2 and MDMX expression in acquisition of mesenchymal phenotype in benign and cancer cells

Plasticity of cancer cells, manifested by transitions between epithelial and mesenchymal phenotypes, represents a challenging issue in the treatment of neoplasias. Both epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) are implicated in the processes of metastasis formation and acquisition of stem cell-like properties. Mouse double minute (MDM) 2 and MDMX are important players in cancer progression, as they act as regulators of p53, but their function in EMT and metastasis may be contradictory. Here, we show that the EMT phenotype in multiple cellular models and in clinical prostate and breast cancer samples is associated with a decrease in MDM2 and increase in MDMX expression. Modulation of EMT-accompanying changes in MDM2 expression in benign and transformed prostate epithelial cells influences their migration capacity and sensitivity to docetaxel. Analysis of putative mechanisms of MDM2 expression control demonstrates that in the context of defective p53 function, MDM2 expression is regulated by EMT-inducing transcription factors Slug and Twist. These results provide an alternative context-specific role of MDM2 in EMT, cell migration, metastasis, and therapy resistance.

The Roles of MDM2 and MDMX in Cancer

For more than 25 years, MDM2 and its homolog MDMX (also known as MDM4) have been shown to exert oncogenic activity. These two proteins are best understood as negative regulators of the p53 tumor suppressor, although they may have additional p53-independent roles. Understanding the dysregulation of MDM2 and MDMX in human cancers and how they function either together or separately in tumorigenesis may improve methods of diagnosis and for assessing prognosis. Targeting the proteins themselves, or their regulators, may be a promising therapeutic approach to treating some forms of cancer.

Association of the recurrence of vocal leukoplakia with MDM2-309 variants over a 2-year period: a prospective study

CONCLUSION

MDM2-309 polymorphism variant genotypes decrease the risk of recurrence in vocal leukoplakia.

OBJECTIVE

The results of a previous study 2 years ago showed the effect of mouse double minute 2 homolog (MDM2) SNP309 polymorphisms in people with laryngeal carcinoma and vocal leukoplakia (a pre-cancerous laryngeal carcinoma lesion). This prospective, clinical trial was performed to assess the relationship between MDM2-309 polymorphism variants and recurrence/cancerization rates in people with vocal leukoplakia over a 2-year period.

PARTICIPANTS AND METHOD

A total of 61 post-operative patients with vocal leukoplakia participated in this prospective, observational, 2-year, follow-up study, and were genotyped for the MDM2-309 gene using pyrosequencing. Recurrence and cancerization rates were used to assess the relationship between the clinical outcome and the genotype variants.

RESULTS

The recurrence rate in the GT genotypes group was lower than that in the normal TT genotype group (17.2% vs 50%, p = 0.05) and there was a significantly lower recurrence rate in the GG genotype group than in the normal TT genotype group (10% vs 50%, p = 0.03). However, there was no statistically significant difference in the cancerization rate between the MDM2-309 variant (GT + GG) genotypes group and the normal TT genotype group (12.2% vs 8.3%, p > 0.05) over the 2-year follow-up period.

The overexpression of SOX2 affects the migration of human teratocarcinoma cell line NT2/D1

The altered expression of the SOX2 transcription factor is associated with oncogenic or tumor suppressor functions in human cancers. This factor regulates the migration and invasion of different cancer cells. In this study we investigated the effect of constitutive SOX2 overexpression on the migration and adhesion capacity of embryonal teratocarcinoma NT2/D1 cells derived from a metastasis of a human testicular germ cell tumor. We detected that increased SOX2 expression changed the speed, mode and path of cell migration, but not the adhesion ability of NT2/D1 cells. Additionally, we demonstrated that SOX2 overexpression increased the expression of the tumor suppressor protein p53 and the HDM2 oncogene. Our results contribute to the better understanding of the effect of SOX2 on the behavior of tumor cells originating from a human testicular germ cell tumor. Considering that NT2/D1 cells resemble cancer stem cells in many features, our results could contribute to the elucidation of the role of SOX2 in cancer stem cells behavior and the process of metastasis.

Loss of expression of the tumour suppressor gene AIMP3 predicts survival following radiotherapy in muscle-invasive bladder cancer

The aim of this study was to test the utility of AIMP3, an upstream regulator of DNA damage response following genotoxic stress, as a clinical biomarker in muscle-invasive bladder cancer (MIBC). AIMP3 was identified from a meta-analysis of a global gene-expression dataset. AIMP3 protein expression was determined by immunohistochemistry on a customised bladder cancer tissue-microarray (TMA). The mechanism of gene silencing was probed using methylation-specific PCR. The association between AIMP3 expression, Tp53 transactivity and genomic stability was analysed. In vitro AIMP3 translocation to the nucleus in response to ionising radiation was demonstrated using immunofluorescence. Radiosensitisation effects of siRNA-mediated AIMP3-knockdown were measured using colony forming assays. TMAs derived from patients enrolled in BCON, a Phase III multicentre radiotherapy trial in bladder cancer (ISRCTN45938399) were used to evaluate the association between AIMP3 expression and survival. The prognostic value of AIMP3 expression was determined in a TMA derived from patients treated by radical cystectomy. Loss of AIMP3 expression was frequent in MIBC and associated with impaired Tp53 transactivity and genomic instability. AIMP3-knockdown was associated with an increase in radioresistance. Loss of AIMP3 expression was associated with survival in MIBC patients following radiotherapy (HR = 0.53; 95% CI: 0.36 to 0.78, p = 0.002) but was not prognostic in the cystectomy set. In conclusion, AIMP3 expression is lost in a subset of bladder cancers and is significantly predictive of survival following radiotherapy in MIBC patients.

Copy number analysis of 24 oncogenes: MDM4 identified as a putative marker for low recurrence risk in non muscle invasive bladder cancer

Patients with non-muscle invasive bladder cancer (NMIBC) generally have a high risk of relapsing locally after primary tumor resection. The search for new predictive markers of local recurrence thus represents an important goal for the management of this disease. We studied the copy number variations (CNVs) of 24 oncogenes (MDM4, MYCN, ALK, PDGFRA, KIT, KDR, DHFR, EGFR, MET, SMO, FGFR1, MYC, ABL1, RET, CCND1, CCND2, CDK4, MDM2, AURKB, ERBB2, TOP2A, AURKA, AR and BRAF) using multiplex ligation probe amplification technique to verify their role as predictive markers of recurrence. Formalin-fixed paraffin-embedded tissue samples from 43 patients who underwent transurethral resection of the bladder (TURB) were used; 23 patients had relapsed and 20 were disease-free after 5 years. Amplification frequencies were analyzed for all genes and MDM4 was the only gene that showed significantly higher amplification in non recurrent patients than in recurrent ones (0.65 vs. 0.3; Fisher’s test p = 0.023). Recurrence-free survival analysis confirmed the predictive role of MDM4 (log-rank test p = 0.041). Our preliminary results indicate a putative role for the MDM4 gene in predicting local recurrence of bladder cancer. Confirmation of this hypothesis is needed in a larger cohort of NMIBC patients.

Amplification of Mdmx and overexpression of MDM2 contribute to mammary carcinogenesis by substituting for p53 mutations

Background

The p53 tumor suppressor gene is mutated or deleted in nearly half of human cancers. The murine double minute 2 (Mdm2) and Mdmx represent two important cellular regulators of p53. The aim of this study was to evaluate the abnormalities of p53, Mdmx and Mdm2 genes in archived breast cancers.

Methods

We assessed the genetic instability at p53, Mdmx and Mdm2 using high resolution multi-color fluorescent in situ hybridization (FISH) protocol and detected the expression status of the tumor protein p53 (TP53), MDMx and MDM2 by immunohistochemistry in 115 archived samples of infiltrating ductal breast carcinomas with foci of ductal carcinoma in situ (DCIS) components.

Results

The presence of p53 allelic loss and/or TP53 overexpression was observed in 38% out of all patients, and was significantly more often in larger, high grade, ER negative and high ki67 tumors. Mdmx amplification with low-level increase of gene copy number is at high frequency while Mdm2 amplification is rare in primary breast cancer. Mdmx amplification was seen in more invasive carcinomas than preinvasive lesions. MDMx and MDM2 overexpression were detected in 65% and 38% of all cases respectively. Moreover it was showed that most tumors contained either p53 dysfunction or Mdm2 alteration, but not both. This distribution was significant (P < 0.05). Inverse correlation between Mdmx amplification/overexpression and p53 disfunction was also observed (P < 0.05).

Conclusions

Our results suggest the involvement of Mdm2 and Mdmx in p53-independent breast carcinogenesis and Mdmx may contribute to the regulation of p53 independently of Mdm2.

Virtual slides

The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1450529994118798.

Mdm2 and MdmX involvement in human cancer

Discovered in 1987 and 1997 respectively, Mdm2 and MdmX represent two critical cellular regulators of the p53 tumor suppressor. This chapter reviews each from initial discovery to our current understanding of their deregulation in human cancer with a focus on how each regulator impacts p53 function. While p53 independent activities of Mdm2 and MdmX are noted the reader is directed to other reviews on this topic. The chapter concludes with an examination of the various mechanisms of Mdm-deregulation and an assessment of the current therapeutic approaches to target Mdm2 and MdmX overexpression.

Mdm2 SNP309 G-variant is associated with invasive growth of human urinary bladder cancer

OBJECTIVE

Human mouse double minute 2 (Mdm2) is essential in degrading p53 by acting as an ubiquitin ligase and therefore plays a vital role in cell cycle and survival. The G-variant of the Mdm2 SNP309, which is located within the promoter of the Mdm2 gene, increases expression of Mdm2 and thereby inhibits the p53 pathway. Several studies have investigated the influence of this SNP on disease risk and onset of various malignancies. The impact of Mdm2 SNP309 on bladder cancer is still to be established due to inconsistent data.

METHODS

In a case-control study we determined the distribution of Mdm2 SNP309 genotypes in 111 patients with an early-onset bladder cancer (diagnosis <45 years of age), in 113 consecutive bladder cancer patients and in a control group consisting of 140 patients without any malignancy.

RESULTS

There was no significant association between the allelic distribution of the Mdm2 SNP309 and tumor risk, early onset, gender or grade of the tumor. According to tumor stage we found a significant difference in the distribution of the Mdm2 SNP309 between patients with noninvasive and invasive (≥pT1) tumor growth (p = 0.016). In patients with invasive tumors a significant increase of the G allele was found (T/T vs. T/G + G/G; p = 0.023; OR 2.203, 95% CI 1.111-4.369).

CONCLUSION

These data indicate that the G-variant of the Mdm2 SNP309 might influence the development of a more aggressive tumor phenotype in patients with bladder cancer without affecting the overall tumor risk.

Identification of nine genomic regions of amplification in urothelial carcinoma, correlation with stage, and potential prognostic and therapeutic value

We performed a genome wide analysis of 164 urothelial carcinoma samples and 27 bladder cancer cell lines to identify copy number changes associated with disease characteristics, and examined the association of amplification events with stage and grade of disease. Multiplex inversion probe (MIP) analysis, a recently developed genomic technique, was used to study 80 urothelial carcinomas to identify mutations and copy number changes. Selected amplification events were then analyzed in a validation cohort of 84 bladder cancers by multiplex ligation-dependent probe assay (MLPA). In the MIP analysis, 44 regions of significant copy number change were identified using GISTIC. Nine gene-containing regions of amplification were selected for validation in the second cohort by MLPA. Amplification events at these 9 genomic regions were found to correlate strongly with stage, being seen in only 2 of 23 (9%) Ta grade 1 or 1–2 cancers, in contrast to 31 of 61 (51%) Ta grade 3 and T2 grade 2 cancers, p<0.001. These observations suggest that analysis of genomic amplification of these 9 regions might help distinguish non-invasive from invasive urothelial carcinoma, although further study is required. Both MIP and MLPA methods perform well on formalin-fixed paraffin-embedded DNA, enhancing their potential clinical use. Furthermore several of the amplified genes identified here (ERBB2, MDM2, CCND1) are potential therapeutic targets.

Genetic and epigenetic alterations of myeloproliferative disorders

The classical BCR-ABL negative myeloproliferative neoplasms (MPN) polycythemia vera, essential thrombocythemia, and primary myelofibrosis are clonal hematopoietic disorders characterized by excessive production of terminally differentiated myeloid cells. In MPN patients, the disease can progress to secondary myelofibrosis or acute myeloid leukemia. Clonal hematopoiesis, disease phenotype, and progression are caused by somatically acquired genetic lesions of genes involved in cytokine signaling, RNA splicing, as well as epigenetic regulation. This review provides an overview of point mutations and cytogenetic lesions associated with MPN and addresses the role of these somatic lesions in MPN disease progression.

The p53 pathway in hematopoiesis: lessons from mouse models, implications for humans

Aberrations in the p53 tumor suppressor pathway are associated with hematologic malignancies. p53-dependent cell cycle control, senescence, and apoptosis functions are actively involved in maintaining hematopoietic homeostasis under normal and stress conditions. Whereas loss of p53 function promotes leukemia and lymphoma development in humans and mice, increased p53 activity inhibits hematopoietic stem cell function and results in myelodysplasia. Thus, exquisite regulation of p53 activity is critical for homeostasis. Most of our understanding of p53 function in hematopoiesis is derived from genetically engineered mice. Here we summarize some of these models, the various mechanisms that disrupt the regulation of p53 activity, and their relevance to human disease.

TP53 pathway analysis in paediatric Burkitt lymphoma reveals increased MDM4 expression as the only TP53 pathway abnormality detected in a subset of cases

The TP53 (p53) pathway can be inhibited by TP53 mutation or deletion or by MDM2 overexpression. Both occur in Burkitt lymphoma (BL), but many cases lack either abnormality. Expression patterns of the TP53 inhibitor MDM4 have not been reported in BL, and increased MDM4 could deregulate the TP53 pathway in cases without TP53 or MDM2 abnormalities. We investigated TP53 pathway disruption in paediatric BL patient samples (n = 30) by studying MDM4, MDM2, and CDKN1A (p21) protein and mRNA expression; TP53 mutations; TP53 protein expression; and gene copy number abnormalities. MDM4 protein was expressed in 30/30 tumours, and MDM2 protein was weakly expressed in 7/30 (23%). All cases were negative for CDKN1A protein, and CDKN1A mRNA levels were decreased. TP53 mutations were detected in 5/28 (18%) cases and confirmed by sequencing. TP53 protein was expressed in 15/30 (50%) cases, including 7/8 with TP53 genetic alterations. MDM2 protein and mRNA expression levels did not correlate with lack of TP53 genetic changes or TP53 protein expression; however, there was an inverse relationship between detectable TP53 protein expression and MDM4 copy number gains and mRNA expression. The TP53 pathway is deregulated in paediatric BL cases, and increased MDM4 expression may be the primary mechanism in some cases.

Evaluation of HER2 and p53 expression in predicting response to docetaxel-based first-line chemotherapy in advanced breast cancer

Background

The human epidermal growth factor receptor 2 (HER2) and p53 pathways may be involved in chemotherapy sensitivity and/or resistance. We explore the value of HER2 and p53 status to foretell docetaxel sensitivity in advanced breast cancer.

Methods

HER2 and p53 expression was analysed in 36 (median age 55 yrs; range 37-87) metastatic breast cancer patients receiving docetaxel-based first-line chemotherapy. HER2 was determined by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH), p53 was tested by IHC. We correlate the expression of study parameters with pathologic parameters, RECIST response and survival. The standard cut-off value of 2 was used to determine HER2 overexpression while p53 mean expression level was used to divide low/high expressors tumors.

Results

Median time to progression and overall survival were 9 (range 2 - 54) and 20 (range 3 - 101) months. Overall response rate was 41.6%. Nine cases showed HER2 overexpression. HER2 was more frequently overexpressed in less differentiated (p = 0.05) and higher stage (p = 0.003) disease. Mean FISH-HER2 values were significantly higher in responder than in non-responder pts (8.53 ± 10.21 vs 2.50 ± 4.12, p = 0.027). Moreover, HER2 overexpression correlates with treatment response at cross-tabulation analysis (p = 0.046). p53 expression was only associated with higher stage disease (p = 0.02) but lack of any significant association with HER status or docetaxel response. No significant relation with survival was observed for any parameter.

Conclusion

Our data seem to indicate that FISH-determined HER2 status but not p53 is associated with docetaxel sensitivity in metastatic breast cancer.

The biological, clinical and prognostic implications of p53 transcriptional pathways in breast cancers

We hypothesized that the functional status of p53 transcriptional pathways, rather than p53 protein expression alone, could accurately discriminate between low- and high-risk breast carcinoma (BC) and inform about individuals' tumour biological behaviour. To test this, we studied a well-characterized series of 990 BCs with long-term follow-up, immunohistochemically profiled for p53, its main regulators and downstream genes. Results were validated in an independent series of patients (n = 245) uniformly treated with adjuvant anthracycline-based chemotherapy. Eleven p53 transcriptional phenotypes were identified with just two main clinical outcomes. (a) Low risk/good prognosis group (active/partially inactive p53 pathways), defined as p53(+/-)/MDM4(+)/MDM2(+/-)/Bcl2(+/-)/p21(+/-), p53(-)/MDM4(-)/MDM2(+)/Bcl2(+)/p21(+/-) and p53(+/-)/MDM4(-)/MMD2(-)/Bcl2(+)/p21(+/-). These tumours had favourable clinicopathological characteristics, including ER(+) and long survival after systemic adjuvant-therapy (AT). (b) High risk/poor prognosis group (completely inactive p53 pathways), defined as p53(+/-)/MDM4(-) MDM2(-)/Bcl2(-)/p21(-), p53(-)/MDM4(-) MDM2(+)/Bcl2(-)/p21(-) and p53(+/-)/MDM4(-)/MDM2(-)/Bcl2(-)/p21(+). These tumours were characterized by aggressive clinicopathological characteristics and showed shortened survival when treated with AT. Completely inactive p53 pathways but intact p21 axis p53(+/-)/MDM4(-)/MDM2(-)/Bcl2(-)/p21(+) had the worst prognosis, particularly patients who received AT. Multivariate Cox regression models, including validated prognostic factors for both test and validation series, revealed that the functional status of p53 transcriptional pathways was an independent prognosticator for BC-specific survival (HR 2.64 and 4.5, p < 0.001, respectively) and disease-free survival (HR 1.93 and 2.5, p < 0.001, respectively). In conclusion, p53 functional status determined by assessment of p53 regulatory and downstream targets provides independent prognostic value and may help determine more adequate therapeutic regimens for specific subgroups of breast cancer patients.

Overexpression of the JmjC histone demethylase KDM5B in human carcinogenesis: involvement in the proliferation of cancer cells through the E2F/RB pathway

BACKGROUND

Although an increasing number of histone demethylases have been identified and biochemically characterized, their biological functions largely remain uncharacterized, particularly in the context of human diseases such as cancer. We investigated the role of KDM5B, a JmjC histone demethylase, in human carcinogenesis. Quantitative RT-PCR and microarray analyses were used to examine the expression profiles of histone demethylases in clinical tissue samples. We also examined the functional effects of KDM5B on the growth of cancer cell lines treated with small interfering RNAs (siRNAs). Downstream genes and signal cascades induced by KDM5B expression were identified from Affymetrix Gene Chip experiments, and validated by real-time PCR and reporter assays. Cell cycle-dependent characteristics of KDM5B were identified by immunofluorescence and FACS.

RESULTS

Quantitative RT-PCR analysis confirmed that expression levels of KDM5B are significantly higher in human bladder cancer tissues than in their corresponding non-neoplastic bladder tissues (P < 0.0001). The expression profile analysis of clinical tissues also revealed up-regulation of KDM5B in various kinds of malignancies. Transfection of KDM5B-specific siRNA into various bladder and lung cancer cell lines significantly suppressed the proliferation of cancer cells and increased the number of cells in sub-G1 phase. Microarray expression analysis indicated that E2F1 and E2F2 are downstream genes in the KDM5B pathway.

CONCLUSIONS

Inhibition of KDM5B may affect apoptosis and reduce growth of cancer cells. Further studies will explore the pan-cancer therapeutic potential of KDM5B inhibition.

Focal amplifications are associated with high grade and recurrences in stage Ta bladder carcinoma

Urinary bladder cancer is a heterogeneous disease with tumors ranging from papillary noninvasive (stage Ta) to solid muscle infiltrating tumors (stage T2+). The risk of progression and death for the most frequent diagnosed type, Ta, is low, but the high incidence of recurrences has a significant effect on the patients' quality of life and poses substantial costs for health care systems. Consequently, the purpose of this study was to search for predictive factors of recurrence on the basis of genetic profiling. A clinically well characterized cohort of Ta bladder carcinomas, selected by the presence or absence of recurrences, was evaluated by an integrated analysis of DNA copy number changes and gene expression (clone-based 32K, respectively, U133Plus2.0 arrays). Only a few chromosomal aberrations have previously been defined in superficial bladder cancer. Surprisingly, the profiling of Ta tumors with a high-resolution array showed that DNA copy alterations are relatively common in this tumor type. Furthermore, we observed an overrepresentation of focal amplifications within high-grade and recurrent cases. Known (FGFR3, CCND1, MYC, MDM2) and novel candidate genes were identified within the loci. For example, MYBL2, a nuclear transcription factor involved in cell-cycle progression; YWHAB, an antiapoptotic protein; and SDC4, an important component of focal adhesions represent interesting candidates detected within two amplicons on chromosome 20, for which DNA amplification correlated with transcript up-regulation. The observed overrepresentation of amplicons within high-grade and recurrent cases may be clinically useful for the identification of patients who will benefit from a more aggressive therapy.

Suppression of the mouse double minute 4 gene causes changes in cell cycle control in a human mesothelial cell line responsive to ultraviolet radiation exposure

The TP53 tumor suppressor gene is the most frequently inactivated gene in human cancer identified to date. However, TP53 mutations are rare in human mesotheliomas, as well as in many other types of cancer, suggesting that aberrant TP53 function may be due to alterations in its regulatory pathways. Mouse double minute 4 (MDM4) has been shown to be a key regulator of TP53 activity, both independently as well as in concert with its structural homolog, Mouse Double Minute 2 (MDM2). The purpose of this study was to characterize the effects of MDM4 suppression on TP53 and other proteins involved in cell cycle control before and after ultraviolet (UV) exposure in MeT5a cells, a nonmalignant human mesothelial line. Short hairpin RNA (shRNA) was used to investigate the impact of MDM4 on TP53 function and cellular transcription. Suppression of MDM4 was confirmed by Western blot. MDM4 suppressed cells were analyzed for cell cycle changes with and without exposure to UV. Changes in cell growth as well as differences in the regulation of direct transcriptional targets of TP53, CDKN1A (cyclin-dependent kinase 1alpha, p21) and BAX, suggest a shift from cell cycle arrest to apoptosis upon increasing UV exposure. These results demonstrate the importance of MDM4in cell cycle regulation as well as a possible role inthe pathogenesis of mesothelioma-type cancers.

Genome-wide profiling of chromosomal alterations in renal cell carcinoma using high-density single nucleotide polymorphism arrays

The identification of genetic aberrations may help understand the mechanisms of tumorigenesis and has important implications in diagnosis, prognosis and treatment. We applied Illumina's 317K high-density single nucleotide polymorphism (SNP) arrays to profile chromosomal aberrations in clear cell renal cell carcinoma (ccRCC) from 80 patients and analyzed the association of LOH/amplification events with clinicopathological characteristics and telomere length. The most common loss of heterozygosity (LOH) were 3p (69 cases) including 38 whole 3p arm losses, 30 large fragment LOH (spanning 3p21-36), and 1 interstitial LOH (spanning 3p12-14, 3p21-22, 3p24.1-24.2 and 3p24.3), followed by chromosome losses at 8p12-pter, 6q23.3-27, 14q24.1-qter, 9q32-qter, 10q22.3-qter, 9p13.3-pter, 4q28.3-qter and 13q12.1-21.1. We also found several smallest overlapping regions of LOH that contained tumor suppressor genes. One smallest LOH in 8p12 had a size of 0.29 Mb and only contained one gene (NRG1). The most frequent chromosome gains were at 5q (32 cases), including 10 whole 5q amplification, 21 large amplifications encompassing 5q32-ter and 1 focal amplification in 5q35.3 (0.42 Mb). The other common chromosome gains were 1q25.1-qter, 7q21.13-qter, 8q24.12-qter and whole 7p arm. Significant associations of LOH at 9p, 9q, 14q and 18q were observed with higher nuclear grade. Significant associations with tumor stage were observed for LOH at 14q, 18p and 21q. Finally, we found that tumors with LOH at 2q, 6p, 6q, 9p, 9q and 17p had significantly shorter telomere length than those without LOH. This is the first study to use Illumina's SNP-CGH array that provides a close estimate of the size and frequency of chromosome LOH and amplifications of ccRCC. The identified regions and genes may become diagnostic and prognostic biomarkers as well as potential targets of therapy.

Targeting Mdm2 and Mdmx in cancer therapy: better living through medicinal chemistry?

Genomic and proteomic profiling of human tumor samples and tumor-derived cell lines are essential for the realization of personalized therapy in oncology. Identification of the changes required for tumor initiation or maintenance will likely provide new targets for small-molecule and biological therapeutics. For example, inactivation of the p53 tumor suppressor pathway occurs in most human cancers. Although this can be due to frank p53 gene mutation, almost half of all cancers retain the wild-type p53 allele, indicating that the pathway is disabled by other means. Alternate mechanisms include deletion or epigenetic inactivation of the p53-positive regulator arf, methylation of the p53 promoter, or elevated expression of the p53 regulators Mdm2 and Mdmx. This review discusses current models of p53 regulation by Mdm2 and Mdmx and presents the rationale for design of future Mdmx-specific therapeutics based on our knowledge of its structure and biological functions.