Deficiencies in Chfr and Mlh1 synergistically enhance tumor susceptibility in mice

Differential gene expression and network analysis in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is a prevalent malignancy with a poor prognosis, whose biomarkers have not been studied in great detail. We have collected genomic data of HNSCC patients from The Cancer Genome Atlas (TCGA) and analyzed them to get deeper insights into the gene expression pattern. Initially, 793 differentially expressed genes (DEGs) were categorized, and their enrichment analysis was performed. Later, a protein-protein interaction network for the DEGs was constructed using the STRING plugin in Cytoscape to study their interactions. A set of 10 hub genes was selected based on Maximal Clique Centrality score, and later their survival analysis was studied. The elucidated set of 10 genes, i.e., PRAME, MAGEC2, MAGEA12, LHX1, MAGEA3, CSAG1, MAGEA6, LCE6A, LCE2D, LCE2C, referred to as potential candidates to be explored as HNSCC biomarkers. The Kaplan-Meier overall survival of the selected genes suggested that the alterations in the candidate genes were linked to the decreased survival of the HNSCC patients. Altogether, the results of this study signify that the genomic alterations and differential expression of the selected genes can be explored in therapeutic interpolations of HNSCC, exploiting early diagnosis and target-propelled therapy.

Deciphering CHFR Role in Pancreatic Ductal Adenocarcinoma

Checkpoint with forkhead-associated and ring finger domains (CHFR) has been proposed as a predictive and prognosis biomarker for different tumor types, but its role in pancreatic ductal adenocarcinoma (PDAC) remains unknown. The aim of this study was two-pronged: to review the role of CHFR in PDAC and evaluating CHFR as a potential predictive biomarker in this disease. For this purpose, we first explored the CHFR messenger (m)RNA expression and promoter methylation through the TCGA database. Secondly, the CHFR expression and promoter methylation were prospectively evaluated in a cohort of patients diagnosed with borderline (n = 19) or resectable (n = 16) PDAC by immunohistochemistry (IHC), methylation specific-PCR (MSP), and pyrosequencing. The results from the TCGA database showed significant differences in terms of progression-free survival (PFS) and overall survival (OS) based on the CHFR mRNA expression, which was likely independent from the promoter methylation. Importantly, our results showed that in primarily resected patients and also the entire cohort, a higher CHFR expression as indicated by the higher IHC staining intensity might identify patients with longer disease-free survival (DFS) and OS, respectively. Similarly, in the same cohorts, patients with lower methylation levels by pyrosequencing showed significantly longer OS than patients without this pattern. Both, the CHFR expression intensity and its promoter methylation were established as independent prognostic factors for PFS and OS in the entire cohort. In contrast, no significant differences were found between different methylation patterns for CHFR and the response to taxane-based neoadjuvant treatment. These results suggest the potential role of the higher expression of CHFR and the methylation pattern of its promoter as potential prognostic biomarkers in PDAC, thus warranting further comprehensive studies to extend and confirm our preliminary findings.

CHFR and Paclitaxel Sensitivity of Ovarian Cancer

The poly(ADP-ribose) binding protein CHFR regulates cellular responses to mitotic stress. The deubiquitinase UBC13, which regulates CHFR levels, has been associated with better overall survival in paclitaxel-treated ovarian cancer. Despite the extensive use of taxanes in the treatment of ovarian cancer, little is known about expression of CHFR itself in this disease. In the present study, tissue microarrays containing ovarian carcinoma samples from 417 women who underwent initial surgical debulking were stained with anti-CHFR antibody and scored in a blinded fashion. CHFR levels, expressed as a modified H-score, were examined for association with histology, grade, time to progression (TTP) and overall survival (OS). In addition, patient-derived xenografts from 69 ovarian carcinoma patients were examined for CHFR expression and sensitivity to paclitaxel monotherapy. In clinical ovarian cancer specimens, CHFR expression was positively associated with serous histology (p = 0.0048), higher grade (p = 0.000014) and higher stage (p = 0.016). After correction for stage and debulking, there was no significant association between CHFR staining and overall survival (p = 0.62) or time to progression (p = 0.91) in patients with high grade serous cancers treated with platinum/taxane chemotherapy (N = 249). Likewise, no association between CHFR expression and paclitaxel sensitivity was observed in ovarian cancer PDXs treated with paclitaxel monotherapy. Accordingly, differences in CHFR expression are unlikely to play a major role in paclitaxel sensitivity of high grade serous ovarian cancer.

Polo-like kinase 1 induces epithelial-to-mesenchymal transition and promotes epithelial cell motility by activating CRAF/ERK signaling

Polo-like kinase 1 (PLK1) is a key cell cycle regulator implicated in the development of various cancers, including prostate cancer. However, the functions of PLK1 beyond cell cycle regulation remain poorly characterized. Here, we report that PLK1 overexpression in prostate epithelial cells triggers oncogenic transformation. It also results in dramatic transcriptional reprogramming of the cells, leading to epithelial-to-mesenchymal transition (EMT) and stimulation of cell migration and invasion. Consistently, PLK1 downregulation in metastatic prostate cancer cells enhances epithelial characteristics and inhibits cell motility. The signaling mechanisms underlying the observed cellular effects of PLK1 involve direct PLK1-dependent phosphorylation of CRAF with subsequent stimulation of the MEK1/2-ERK1/2-Fra1-ZEB1/2 signaling pathway. Our findings highlight novel non-canonical functions of PLK1 as a key regulator of EMT and cell motility in normal prostate epithelium and prostate cancer. This study also uncovers a previously unanticipated role of PLK1 as a potent activator of MAPK signaling.

High-definition CpG methylation of novel genes in gastric carcinogenesis identified by next-generation sequencing

Gastric cancers are the most frequent gastric malignancy and usually arise in the sequence of Helicobacter pylori-associated chronic gastritis. CpG methylation is a central mechanism of epigenetic gene regulation affecting cancer-related genes, and occurs early in gastric carcinogenesis. DNA samples from non-metaplastic gastric mucosa with variable levels of gastritis (non-metaplastic mucosa), intestinal metaplasia, or gastric cancer were screened with methylation arrays for CpG methylation of cancer-related genes and 30 gene targets were further characterized by high-definition bisulfite next-generation sequencing. In addition, data from The Cancer Genome Atlas were analyzed for correlation of methylation with gene expression. Overall, 13 genes had significantly increased CpG methylation in gastric cancer vs non-metaplastic mucosa (BRINP1, CDH11, CHFR, EPHA5, EPHA7, FGF2, FLI1, GALR1, HS3ST2, PDGFRA, SEZ6L, SGCE, and SNRPN). Further, most of these genes had corresponding reduced expression levels in gastric cancer compared with intestinal metaplasia, including novel hypermethylated genes in gastric cancer (FLI1, GALR1, SGCE, and SNRPN), suggesting that they may regulate neoplastic transformation from non-malignant intestinal metaplasia to cancer. Our data suggest a tumor-suppressor role for FLI1 in gastric cancer, consistent with recently reported data in breast cancer. For the genes with strongest methylation/expression correlation, namely FLI1, the expression was lowest in microsatellite-unstable tumors compared with other gastric cancer molecular subtypes. Importantly, reduced expression of hypermethylated BRINP1 and SGCE was significantly associated with favorable survival in gastric cancer. In summary, we report novel methylation gene targets that may have functional roles in discrete stages of gastric carcinogenesis and may serve as biomarkers for diagnosis and prognosis of gastric cancer.

Emerging evidence for CHFR as a cancer biomarker: from tumor biology to precision medicine

Novel insights in the biology of cancer have switched the paradigm of a “one-size-fits-all” cancer treatment to an individualized biology-driven treatment approach. In recent years, a diversity of biomarkers and targeted therapies has been discovered. Although these examples accentuate the promise of personalized cancer treatment, for most cancers and cancer subgroups no biomarkers and effective targeted therapy are available. The great majority of patients still receive unselected standard therapies with no use of their individual molecular characteristics. Better knowledge about the underlying tumor biology will lead the way toward personalized cancer treatment. In this review, we summarize the evidence for a promising cancer biomarker: checkpoint with forkhead and ring finger domains (CHFR). CHFR is a mitotic checkpoint and tumor suppressor gene, which is inactivated in a diverse group of solid malignancies, mostly by promoter CpG island methylation. CHFR inactivation has shown to be an indicator of poor prognosis and sensitivity to taxane-based chemotherapy. Here we summarize the current knowledge of altered CHFR expression in cancer, the impact on tumor biology and implications for personalized cancer treatment.

Aurora kinase A in gastrointestinal cancers: time to target

Gastrointestinal (GI) cancers are a major cause of cancer-related deaths. During the last two decades, several studies have shown amplification and overexpression of Aurora kinase A (AURKA) in several GI malignancies. These studies demonstrated that AURKA not only plays a role in regulating cell cycle and mitosis, but also regulates a number of key oncogenic signaling pathways. Although AURKA inhibitors have moved to phase III clinical trials in lymphomas, there has been slower progress in GI cancers and solid tumors. Ongoing clinical trials testing AURKA inhibitors as a single agent or in combination with conventional chemotherapies are expected to provide important clinical information for targeting AURKA in GI cancers. It is, therefore, imperative to consider investigations of molecular determinants of response and resistance to this class of inhibitors. This will improve evaluation of the efficacy of these drugs and establish biomarker based strategies for enrollment into clinical trials, which hold the future direction for personalized cancer therapy. In this review, we will discuss the available data on AURKA in GI cancers. We will also summarize the major AURKA inhibitors that have been developed and tested in pre-clinical and clinical settings.

Mismatch repair system in endometriotic tissue and eutopic endometrium of unaffected women

OBJECTIVE

To test the immunohistochemical staining pattern of some mismatch repair (MMR) system proteins in endometriotic tissue (ET) and eutopic endometrium.

METHODS

This was a retrospective study conducted at the Pathology and Obstetrics and Gynecology Departments of the Udine University Hospital. We analyzed 528 samples obtained from 246 patients affected by endometriosis and 71 samples from 71 patients with normal endometrium. A tissue microarray model was used to analyze the immunohistochemical expression of MMR system proteins.

RESULTS

Significant loss of MMR proteins was found in the stromal component of ETs. We found MSH2 to be expressed at a higher level than any other MMR system proteins in eutopic endometrium and ETs, to be significantly correlated to Ki-67 expression in both stromal and glandular components of ETs, and to be expressed at a significantly higher level in ETs than in eutopic endometrium. When considering the subgroup of endometriosis with high recurrence rate and glandular cytoplasmic staining for aurora A kinase, we found MMR proteins expressed at a significantly higher level in these ETs than in other ETs and eutopic endometrium of unaffected women.

CONCLUSIONS

We found significant loss of MMR proteins (known to be associated with microsatellite instability) in the stromal component of ETs. The group of ETs with glandular cytoplasmic staining for aurora A kinase had higher MMR protein expression, suggesting an increased activity of this system. Our result suggests a novel role of increased MSH2 expression in cellular proliferation of endometriosis.

Chromosome missegregation rate predicts whether aneuploidy will promote or suppress tumors

Aneuploidy, a chromosome content other than a multiple of the haploid number, is a common feature of cancer cells. Whole chromosomal aneuploidy accompanying ongoing chromosomal instability in mice resulting from reduced levels of the centromere-linked motor protein CENP-E has been reported to increase the incidence of spleen and lung tumors, but to suppress tumors in three other contexts. Exacerbating chromosome missegregation in CENP-E(+/-) mice by reducing levels of another mitotic checkpoint component, Mad2, is now shown to result in elevated cell death and decreased tumor formation compared with reduction of either protein alone. Furthermore, we determine that the additional contexts in which increased whole-chromosome missegregation resulting from reduced CENP-E suppresses tumor formation have a preexisting, elevated basal level of chromosome missegregation that is exacerbated by reduction of CENP-E. Tumors arising from primary causes that do not generate chromosomal instability, including loss of the INK4a tumor suppressor and microsatellite instability from reduction of the DNA mismatch repair protein MLH1, are unaffected by CENP-E-dependent chromosome missegregation. These findings support a model in which low rates of chromosome missegregation can promote tumorigenesis, whereas missegregation of high numbers of chromosomes leads to cell death and tumor suppression.

Transcriptome analysis of a rotenone model of parkinsonism reveals complex I-tied and -untied toxicity mechanisms common to neurodegenerative diseases

The pesticide rotenone, a neurotoxin that inhibits the mitochondrial complex I, and destabilizes microtubules (MT) has been linked to Parkinson disease (PD) etiology and is often used to model this neurodegenerative disease (ND). Many of the mechanisms of action of rotenone are posited mechanisms of neurodegeneration; however, they are not fully understood. Therefore, the study of rotenone-affected functional pathways is pertinent to the understanding of NDs pathogenesis. This report describes the transcriptome analysis of a neuroblastoma (NB) cell line chronically exposed to marginally toxic and moderately toxic doses of rotenone. The results revealed a complex pleiotropic response to rotenone that impacts a variety of cellular events, including cell cycle, DNA damage response, proliferation, differentiation, senescence and cell death, which could lead to survival or neurodegeneration depending on the dose and time of exposure and cell phenotype. The response encompasses an array of physiological pathways, modulated by transcriptional and epigenetic regulatory networks, likely activated by homeostatic alterations. Pathways that incorporate the contribution of MT destabilization to rotenone toxicity are suggested to explain complex I-independent rotenone-induced alterations of metabolism and redox homeostasis. The postulated mechanisms involve the blockage of mitochondrial voltage-dependent anions channels (VDACs) by tubulin, which coupled with other rotenone-induced organelle dysfunctions may underlie many presumed neurodegeneration mechanisms associated with pathophysiological aspects of various NDs including PD, AD and their variant forms. Thus, further investigation of such pathways may help identify novel therapeutic paths for these NDs.

SINE retrotransposons cause epigenetic reprogramming of adjacent gene promoters

Almost half of the human genome and as much as 40% of the mouse genome is composed of repetitive DNA sequences. The majority of these repeats are retrotransposons of the SINE and LINE families, and such repeats are generally repressed by epigenetic mechanisms. It has been proposed that these elements can act as methylation centers from which DNA methylation spreads into gene promoters in cancer. Contradictory to a methylation center function, we have found that retrotransposons are enriched near promoter CpG islands that stay methylation-free in cancer. Clearly, it is important to determine which influence, if any, these repetitive elements have on nearby gene promoters. Using an in vitro system, we confirm here that SINE B1 elements can influence the activity of downstream gene promoters, with acquisition of DNA methylation and loss of activating histone marks, thus resulting in a repressed state. SINE sequences themselves did not immediately acquire DNA methylation but were marked by H3K9me2 and H3K27me3. Moreover, our bisulfite sequencing data did not support that gain of DNA methylation in gene promoters occurred by methylation spreading from SINE B1 repeats. Genome-wide analysis of SINE repeats distribution showed that their enrichment is directly correlated with the presence of USF1, USF2, and CTCF binding, proteins with insulator function. In summary, our work supports the concept that SINE repeats interfere negatively with gene expression and that their presence near gene promoters is counter-selected, except when the promoter is protected by an insulator element.

CHFR: a key checkpoint component implicated in a wide range of cancers

CHFR (Checkpoint with Forkhead-associated and RING finger domains) has been implicated in a checkpoint regulating entry into mitosis. However, the details underlying its roles and regulation are unclear due to conflicting lines of evidence supporting different notions of its functions. We provide here an overview of how CHFR is thought to contribute towards regulating mitotic entry and present possible explanations for contradictory observations published on the functions and regulation of CHFR. Furthermore, we survey key data showing correlations between promoter hypermethylation or down-regulation of CHFR and cancers, with a view on the likely reasons why different extents of correlations have been reported. Lastly, we explore the possibilities of exploiting CHFR promoter hypermethylation status in diagnostics and therapeutics for cancer patients. With keen interest currently focused on the association between hypermethylation of CHFR and cancers, details of how CHFR functions require further study to reveal how its absence might possibly contribute to tumorigenesis.

Acute sensitization of colon cancer cells to inflammatory cytokines by prophase arrest

Understanding how colon cancer cells survive within the inflammatory milieu of a tumor, and developing approaches that increase their sensitivity to inflammatory cytokines, may ultimately lead to novel approaches for colon cancer therapy and prevention. Analysis of a number of chemopreventive and therapeutic agents reveal that HDAC inhibitors are particularly adept at sensitizing colon cancer cells TNF or TRAIL mediated apoptosis. In vivo data are consistent with an interaction between SAHA and TNF in inducing apoptosis, as AOM-induced colon tumors express elevated levels of TNF and are more sensitive to SAHA administration. Cell cycle analysis and time-lapse imaging indicated a close correspondence between SAHA-induced prophase arrest and TNF or TRAIL-induced apoptosis. Prophase arrest induced by the Aurora kinase inhibitor VX680 likewise sensitized cells to TNF and TRAIL, with siRNA analysis pointing to Aurora kinase A (and not Aurora kinase B) as being the relevant target for this sensitization. We propose that agents that promote prophase arrest may help sensitize cancer cells to TNF and other inflammatory cytokines. We also discuss how circumvention of an early mitotic checkpoint may facilitate cancer cell survival in the inflammatory micro-environment of the tumor.