Changes in protein expression due to deleterious mutations in the FA/BRCA pathway

Inherited deleterious mutations in one of the Fanconi anemia genes lead to a disease, characterized by bone marrow failure, myeloid leukemia, and hypersensitivity to DNA damage. We identified proteins likely associated to the molecular signaling pathways involved in DNA repair of interstrand cross-link lesions and in mechanisms of genomic stability mediated by FA/BRCA pathways. We compared protein maps resolved by bidimensional electrophoresis and analyzed differentially expressed proteins, by mass spectrometry, between FA complementation group C (FANCC)-deficient cells, and their ectopically corrected counterpart in physiological conditions or after treatment with MMC. We found six differentially expressed proteins; among them, the checkpoint mediator protein MDC1 whose expression was disrupted in FANCC^−/− cells. The potential role of differentially expressed proteins in FA phenotype is discussed.     

A Protein Prioritization Approach Tailored for the FA/BRCA Pathway

Fanconi anemia (FA) is a heterogeneous recessive disorder associated with a markedly elevated risk to develop cancer. To date sixteen FA genes have been identified, three of which predispose heterozygous mutation carriers to breast cancer. The FA proteins work together in a genome maintenance pathway, the so-called FA/BRCA pathway which is important during the S phase of the cell cycle. Since not all FA patients can be linked to (one of) the sixteen known complementation groups, new FA genes remain to be identified. In addition the complex FA network remains to be further unravelled. One of the FA genes, FANCI, has been identified via a combination of bioinformatic techniques exploiting FA protein properties and genetic linkage. The aim of this study was to develop a prioritization approach for proteins of the entire human proteome that potentially interact with the FA/BRCA pathway or are novel candidate FA genes. To this end, we combined the original bioinformatics approach based on the properties of the first thirteen FA proteins identified with publicly available tools for protein-protein interactions, literature mining (Nermal) and a protein function prediction tool (FuncNet). Importantly, the three newest FA proteins FANCO/RAD51C, FANCP/SLX4, and XRCC2 displayed scores in the range of the already known FA proteins. Likewise, a prime candidate FA gene based on next generation sequencing and having a very low score was subsequently disproven by functional studies for the FA phenotype. Furthermore, the approach strongly enriches for GO terms such as DNA repair, response to DNA damage stimulus, and cell cycle-regulated genes. Additionally, overlaying the top 150 with a haploinsufficiency probability score, renders the approach more tailored for identifying breast cancer related genes. This approach may be useful for prioritization of putative novel FA or breast cancer genes from next generation sequencing efforts.     

Disruption of the TGF-beta pathway and modeling human cancer in mice

There is considerable complexity underlying the mechanisms through which the TGF-beta signaling pathway regulates the initiation and progression of cancer. Analysis of this pathway and the role that it plays in human malignancy continues to elucidate novel mechanisms through which various genetic and epigenetic events subvert the controls that TGF-beta exerts over cell growth, differentiation, and malignant transformation. Modeling these events in the mouse represents an important goal, as the relevant preclinical models are essential not only for improving our understanding of the role of the TGF-beta pathway in the molecular pathogenesis of cancer, but also as tools for evaluating the impact of novel therapeutics on TGF-beta signaling and the role they may play in the prevention and treatment of malignancies. Here, we consider highlights from a number of in vivo murine model systems and relate a few of the significant observations to what we know about TGF-beta signaling in human cancer.     

Wnt signalling pathway in bladder cancer

Bladder cancer (BC) is one of the most common tumours of the urinary system and is also known as a highly malignant tumour. In addition to conventional diagnosis and treatment methods, recent research has focused on studying the molecular mechanisms related to BC, in the hope that new, less toxic and effective targeted anticancer drugs and new diagnostic markers can be discovered. It is known that the Wingless (Wnt) signalling pathway and its related genes, proteins and other substances are involved in multiple biological processes of various tumours. Clarifying the contribution of the Wnt signalling pathway in bladder tumours will help establish early diagnosis indicators, develop new therapeutic drugs and evaluate the prognosis for BC. This review aims to summarise previous studies related to BC and the Wnt signalling pathway, with a focus on exploring the participating substances and their mechanisms in the regulation of the Wnt signalling pathway to better determine how to promote new chemotherapeutic drugs, potential therapeutic targets and diagnostic biomarkers.     

New Roads to FA/BRCA Pathway: H2AX

We have recently described an involvement of H2AX into the Fanconi anemia (FA) BRCA pathway through recruitment of FA protein FANCD2 to the sites of stalled replication forks. We showed that BRCA1 mediates the recruitment of FANCD2 by γH2AX to damaged chromatin and cells deficient or depleted of H2AX exhibit an FA-like phenotype, including an excess of chromatid-type chromosomal aberrations and hypersensitivity to MMC. Here, we discuss a model for the FA pathway and how it could partially explain the common phenotypes of H2AX, BRCA2 and FA deficiencies.     

The PATCHED/Sonic Hedgehog signalling pathway in superficial bladder cancer

Superficial bladder cancer shows a high frequency of total or partial chromosome 9 losses. Loss of heterozygosity at position 9q22.3 is one of the most frequent and is associated with highly recurrent tumours. The PATCHED gene, ortholog of a gene first described in the drosophila as a segment polarity gene, is located at 9q22.3. It is a member of a signal transduction pathway and a tumour suppressor gene (TSG), involved in basal cell carcinoma. We propose PATCHED as a TSG candidate in superficial bladder cancer.     

The Fanconi Anemia/BRCA Signaling Pathway: Disruption in Cisplatin-Sensitive Ovarian Cancers

Ovarian tumors often exhibit chromosome instability and hypersensitivity to the chemotherapeutic agent cisplatin. Recently, we have shown that this cellular phenotype may result from an acquired disruption of the Fanconi Anemia/BRCA (FA/BRCA) signaling pathway. Disruption results from methylation and silencing of one of the FA genes (FANCF), leading to cisplatin sensitivity. Restoration of this pathway is associated with demethylation of FANCF, leading to acquired cisplatinum resistance. The serial inactivation and reactivation of the FA/BRCA pathway has important implications for the diagnosis and treatment of ovarian cancers and related cancers.     

Emerging role of Hippo signalling pathway in bladder cancer

Bladder cancer (BC) is one of the most common cancers worldwide with a high progression rate and poor prognosis. The Hippo signalling pathway is a conserved pathway that plays a crucial role in cellular proliferation, differentiation and apoptosis. Furthermore, dysregulation and/or malfunction of the Hippo pathway is common in various human tumours, including BC. In this review, an overview of the Hippo pathway in BC and other cancers is presented. We focus on recent data regarding the Hippo pathway, its network and the regulation of the downstream co‐effectors YAP1/TAZ. The core components of the Hippo pathway, which induce BC stemness acquisition, metastasis and chemoresistance, will be emphasized. Additional research on the Hippo pathway will advance our understanding of the mechanism of BC as well as the development and progression of other cancers and may be exploited therapeutically.     

Assessing the Link between BACH1 and BRCA1 in the FA Pathway

The BACH1 helicase was initially identified by its direct binding to BRCA1 and, thus, was linked to hereditary breast cancer. More recently, BACH1 was identified as the gene defective in the J complementation group of Fanconi anemia (FA). FA is a multigenetic disorder characterized by cellular sensitivity to crosslinkers and chromosome instability. Because FANCD2 monoubiquitination is intact in BACH1 deficient cells, BACH1 appears to act downstream in the FA pathway akin to BRCA2/FANCD1. Interestingly, while BRCA1 has various interactions with FA proteins it has not been identified as an FA gene. As the race to uncover the last few unknown FA complementation groups comes to an end, future work will be required to uncover how these gene products function to combat the effects of DNA damage and maintain genomic stability. In particular, it remains elusive whether BRCA1 is functionally linked to the FA pathway through its interaction with BACH1/FANCJ. This review focuses on a model for the connection of BRCA1 to BACH1 in the FA pathway. We predict that BRCA1 regulates the BACH1 helicase activity to coordinate the timely displacement of Rad51 from nucleofilaments, promoting error free repair and ultimately maintaining chromosomal integrity.     

Three novel BRCA1/BRCA2 mutations in breast/ovarian cancer families in Croatia

BRCA1 and BRCA2 genes from 167 candidates (145 families) were scanned for mutations. We identified 14 pathogenic point mutations in 17 candidates, 9 in BRCA1 and 5 in BRCA2. Of those, 11 have been previously described and 3 were novel (c.5335C>T in BRCA1 and c.4139_4140dupTT and c.8175G>A in BRCA2). No large deletions or duplications involving BRCA1 and BRCA2 genes were identified. No founder mutations were detected for the Croatian population. Croatia shares most of the mutations with neighboring Slovenia and also with Germany, Austria and Poland. Two common sequence variants in BRCA1, c.2077G>A and c.4956G>A, were found more frequently in mutation carriers compared to healthy controls. No difference in BRCA2 variants was detected between the groups. Haplotype inference showed no difference in haplotype distributions between deleterious mutation carriers and non-carriers in neither BRCA1 nor BRCA2. In silico analyses identified one BRCA1 sequence variant (c.4039A>G) and two BRCA2 variants (c.5986G>A and c.6884G>C) as harmful with high probability, and inconclusive results were obtained for our novel BRCA2 variant c.3864_3866delTAA. Combination of QMPSF and HRMA methods provides high detection rate and complete coverage of BRCA1/2 genes. Benefit of BRCA1/2 mutation testing is clear, since we detected mutations in young unaffected women, who will be closely monitored for breast and ovarian cancer.     

RNA interferences targeting the Fanconi anemia/BRCA pathway upstream genes reverse cisplatin resistance in drug-resistant lung cancer cells

Background

Cisplatin is one of the most commonly used chemotherapy agent for lung cancer. The therapeutic efficacy of cisplatin is limited by the development of resistance.In this study, we test the effect of RNA interference (RNAi) targeting Fanconi anemia (FA)/BRCA pathway upstream genes on the sensitivity of cisplatin-sensitive (A549 and SK-MES-1) and -resistant (A549/DDP) lung cancer cells to cisplatin.

Result

Using small interfering RNA (siRNA), knockdown of FANCF, FANCL, or FANCD2 inhibited function of the FA/BRCA pathway in A549, A549/DDP and SK-MES-1 cells, and potentiated sensitivity of the three cells to cisplatin. The extent of proliferation inhibition induced by cisplatin after knockdown of FANCF and/or FANCL in A549/DDP cells was significantly greater than in A549 and SK-MES-1 cells, suggesting that depletion of FANCF and/or FANCL can reverse resistance of cisplatin-resistant lung cancer cells to cisplatin. Furthermore, knockdown of FANCL resulted in higher cisplatin sensitivity and dramatically elevated apoptosis rates compared with knockdown of FANCF in A549/DDP cells, indicating that FANCL play an important role in the repair of cisplatin-induced DNA damage.

Conclusion

Knockdown of FANCF, FANCL, or FANCD2 by RNAi could synergize the effect of cisplatin on suppressing cell proliferation in cisplatin-resistant lung cancer cells through inhibition of FA/BRCA pathway.     

Genetic variation in the base excision repair pathway and bladder cancer risk

Genetic polymorphisms in DNA repair genes may impact individual variation in DNA repair capacity and alter cancer risk. In order to examine the association of common genetic variation in the base-excision repair (BER) pathway with bladder cancer risk, we analyzed 43 single nucleotide polymorphisms (SNPs) in 12 BER genes (OGG1, MUTYH, APEX1, PARP1, PARP3, PARP4, XRCC1, POLB, POLD1, PCNA, LIG1, and LIG3). Using genotype data from 1,150 cases of urinary bladder transitional cell carcinomas and 1,149 controls from the Spanish Bladder Cancer Study we estimated odds ratios (ORs) and 95% confidence intervals (CIs) adjusting for age, gender, region and smoking status. SNPs in three genes showed significant associations with bladder cancer risk: the 8-oxoG DNA glycosylase gene (OGG1), the Poly (ADP-ribose) polymerase family member 1 (PARP1) and the major gap filling polymerase-β (POLB). Subjects who were heterozygous or homozygous variant for an OGG1 SNP in the promoter region (rs125701) had significantly decreased bladder cancer risk compared to common homozygous: OR (95%CI) 0.78 (0.63–0.96). Heterozygous or homozygous individuals for the functional SNP PARP1 rs1136410 (V762A) or for the intronic SNP POLB rs3136717 were at increased risk compared to those homozygous for the common alleles: 1.24 (1.02–1.51) and 1.30 (1.04–1.62), respectively. In summary, data from this large case-control study suggested bladder cancer risk associations with selected BER SNPs, which need to be confirmed in other study populations. Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Regulation of the prostaglandin pathway during development of invasive bladder cancer in mice

Prostaglandin E(2) (PGE(2)) is reported to play an important role in tumor development. We explored the differential expression of genes governing production of, and response to, PGE(2) during development of invasive bladder cancer. N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN) or vehicle-treated mice (n=4-5) were euthanized after 4-8 weeks (period 1, P1), 12-16 weeks (P2), and 20-23 weeks (P3). Half of each bladder was analyzed histologically and the other half extracted for mRNA analysis by quantitative real-time PCR. Bladders from BBN-treated mice showed progression from submucosal inflammation (P1) to squamous metaplasia/focal CIS (P2) to poorly differentiated, invasive cancer (P3). mRNA levels for the inducible cyclooxygenase, COX-2, were elevated three to fourfold at all time points in BBN-treated mice compared to controls. In contrast, mRNA levels for constitutive COX-1 and cytosolic phospholipase A(2) (cPLA(2)), which releases substrate for COX, were either unchanged or decreased in BBN-treated mice relative to controls. Downstream of COX, mRNA levels of membrane-bound PGE(2) synthase (mPGES-1) were increased 1.7-fold at P1 in BBN bladders but returned to control levels at P2 and P3. mRNA levels for 15-prostaglandin dehydrogenase (PGDH), which inactivates PGE(2), were reduced 50-80% in BBN-treated bladders at all time points. mRNA levels for EP2R and EP4R, receptors for PGE(2), were two to threefold increased at P1, but returned to control levels or below at P3. Hence, increased COX-2 and decreased PDGH expression occurred throughout tumor development, while mPGES-1, EP2R and EP4R were elevated only before development of invasive cancer. We compared expression of these genes in the malignant human urothelial cell lines, HTB-5 and HT-1376, with expression in a benign urothelial cell line, UROtsa. Neither malignant cell line reproduced the complete in vivo pattern, relative to benign cells, but each showed abnormal basal expression of several of the genes downstream of COX-2, but not COX-2 itself. We conclude that components involved in PGE(2) synthesis and activity are differentially regulated during bladder tumor development and the therapeutic efficacy of targeting the various components may vary with stage of tumor development.     

The Lin28/let-7a/c-Myc pathway plays a role in non-muscle invasive bladder cancer

We investigate the role of the Lin28/let-7a/c-Myc pathway in non-muscle invasive bladder cancer (NMIBC). Using RT-PCR, western blot and immunohistochemistry techniques, the levels of pre-let-7a, let-7a, Lin28 and c-Myc RNA and/or proteins were determined in samples of normal bladder tissue and bladder cancer. Expression of pre-let-7a was found to be negatively correlated with the pathological grade of bladder cancer, while let-7a showed a positive correlation with bladder cancer pathological grade. Expression of Lin28 RNA and protein was not significantly different between normal bladder tissue and low-grade transitional cell carcinoma of bladder (TCC) but the expression levels in high-grade TCC were remarkably increased. Expression of c-Myc RNA and protein was significantly higher in bladder cancer samples in comparison to normal bladder tissue without correlation with cancer differentiation. Expression of all the above RNAs and proteins showed no significant difference in Ta and T1 stages. The Lin28/let-7a/c-Myc pathway plays an important role in NMIBC. In particular, expression levels of let-7a correlate with the degree of cancer differentiation but not cancer stage.     

FAT10 promotes the progression of bladder cancer by upregulating HK2 through the EGFR/AKT pathway

The ubiquitin-like protein FAT10 and the hexokinase protein HK2 play vital regulatory roles in several cellular processes. However, the relationship between these two proteins and their role in the pathogenesis of bladder cancer are not well understood. Here, we found that FAT10 and HK2 protein levels were markedly higher in bladder cancer tissues than in normal adjacent tissues. In addition, RNAi-mediated silencing of FAT10 led to reduced HK2 levels and suppressed bladder cancer progression in vivo and in vitro. The results of our in vivo and in vitro experiments revealed that HK2 is critical for FAT10-mediated progression of bladder cancer. The current study demonstrated that FAT10 enhanced the progression of bladder cancer by positively regulating HK2 via the EGFR/AKT pathway. Based on our findings, FAT10 is believed to stabilize EGFR expression by modulating its degradation and ubiquitination. The results of the current study indicate that there is a correlation between FAT10 and HK2 in the progression of bladder cancer. In addition, we identified a new pathway that may be involved in the regulation of HK2. These findings implicate dysfunction of the FAT10, EGFR/AKT, and HK2 regulatory circuit in the progression of bladder cancer.     

DNA2 and EXO1 in replication-coupled,homology-directed repair and in the interplay between HDR and the FA/BRCA network

During DNA replication, stalled replication forks and DSBs arise when the replication fork encounters ICLs (interstrand crosslinks), covalent protein/DNA intermediates or other discontinuities in the template. Recently, homologous recombination proteins have been shown to function in replication-coupled repair of ICLs in conjunction with the Fanconi anemia (FA) regulatory factors FANCD2-FANCI, and, conversely, the FA gene products have been shown to play roles in stalled replication fork rescue even in the absence of ICLs, suggesting a broader role for the FA network than previously appreciated. Here we show that DNA2 helicase/nuclease participates in resection during replication-coupled repair of ICLs and other replication fork stresses. DNA2 knockdowns are deficient in HDR (homology-directed repair) and the S phase checkpoint and exhibit genome instability and sensitivity to agents that cause replication stress. DNA2 is partially redundant with EXO1 in these roles. DNA2 interacts with FANCD2, and cisplatin induces FANCD2 ubiquitylation even in the absence of DNA2. DNA2 and EXO1 deficiency leads to ICL sensitivity but does not increase ICL sensitivity in the absence of FANCD2. This is the first demonstration of the redundancy of human resection nucleases in the HDR step in replication-coupled repair, and suggests that DNA2 may represent a new mediator of the interplay between HDR and the FA/BRCA pathway.     

CCL17-CCR4 axis promotes metastasis via ERK/MMP13 pathway in bladder cancer

As an important chemokine receptor, the role of CCR4 in the progression of bladder cancer (BC) remains unknown. In this study, we have shown that CCR4 expression was upregulated in bladder carcinoma tissues compared with adjacent nontumor tissues. Kaplan-Meier survival analysis revealed that CCR4 expression was an independent prognostic risk factor in BC patients, and the addition of CCL17 induced CCR4 production and promoted migration and invasion of BC cells. In addition, CCR4 knockdown significantly attenuated the migratory and invasive capabilities of BC cells. Mechanistically, CCL17-CCR4 axis is involved in ERK1/2 signaling and could mediate the migration and invasion of BC cells by regulating MMP13 activation. This study suggests that CCR4 might represent a promising prognostic biomarker and a potential therapeutic option for BC.