Helicase-like transcription factor confers radiation resistance in cervical cancer through enhancing the DNA damage repair capacity

The fork remodeler helicase-like transcription factor in cancer development: all at once

The Helicase-like Transcription Factor (HLTF) is a member of the SNF2-family of fork remodelers, primarily studied for its capacity to provide DNA Damage Tolerance (DDT) and to induce replication fork reversal (RFR). HLTF is recruited at stalled forks where both its ATPase motor and HIP116 Rad5p N-terminal (HIRAN) domains are necessary for regulating its interaction with DNA. HIRAN bestows specificity to ssDNA 3'-end and imparts branch migration as well as DNA remodeling capabilities facilitating damage repair. Both expression regulation and mutation rate affect HLTF activity. Gene hypermethylation induces loss of HLTF function, in particular in colorectal cancer (CRC), implying a tumour suppressor role. Surprisingly, a correlation between hypermethylation and HLTF mRNA upregulation has also been observed, even within the same cancer type. In many cancers, both complex mutation patterns and the presence of gene Copy Number Variations (CNVs) have been reported. These conditions affect the amount of functional HLTF and question the physiological role of this fork remodeler. This review offers a systematic collection of the presently strewed information regarding HLTF, its structural and functional characteristics, the multiple roles in DDT and the regulation in cancer progression highlighting new research perspectives.

DTX2 promotes glioma development via regulation of HLTF

BACKGROUND

Human Deltex 2 (DTX2) is a ubiquitin E3 ligase that functions as an oncogene and has been shown to participate in many human cancers. However, the role of DTX2 in glioma progression has remained obscure. In this study, we explore the mechanism underlying the function of DTX2 in glioma progression.

METHODS

The associations between DTX2 expression and clinical characteristics of glioma were determined by bioinformatic analysis of data from The Cancer Genome Atlas and Human Protein Atlas. The expression of DTX2 in glioma tissues was detected using immunohistochemistry and western blotting. Lentivirus-mediated gene knockdown and overexpression were used to determine the effects of DTX2 and helicase-like transcription element (HLTF) on glioma cell proliferation and migration with CCK-8, cell colony formation, transwell, and wound healing assays; flow cytometry in vitro; and animal models in vivo. The interaction of the DTX2 and HLTF proteins was verified by immunoprecipitation assay and confocal microscopy.

RESULTS

DTX2 was highly expressed in glioma samples, and this was correlated with worse overall survival. Silencing of DTX2 suppressed glioma cell viability, colony formation, and migration and induced cell apoptosis. In vitro ubiquitination assays confirmed that DTX2 could downregulate HLTF protein levels by increasing ubiquitination of the HLTF protein. We also observed that HLTF inhibited proliferation and migration of glioma cells. Subcutaneous xenografts with DTX2-overexpressing U87 cells showed significantly increased tumor volumes and weights.

CONCLUSIONS

We have identified DTX2/HLTF as a new axis in the development of glioma that could serve as a prognostic or therapeutic marker.

New insights for gynecological cancer therapies: from molecular mechanisms and clinical evidence to future directions

Advanced and recurrent gynecological cancers lack effective treatment and have poor prognosis. Besides, there is urgent need for conservative treatment for fertility protection of young patients. Therefore, continued efforts are needed to further define underlying therapeutic targets and explore novel targeted strategies. Considerable advancements have been made with new insights into molecular mechanisms on cancer progression and breakthroughs in novel treatment strategies. Herein, we review the research that holds unique novelty and potential translational power to alter the current landscape of gynecological cancers and improve effective treatments. We outline the advent of promising therapies with their targeted biomolecules, including hormone receptor-targeted agents, inhibitors targeting epigenetic regulators, antiangiogenic agents, inhibitors of abnormal signaling pathways, poly (ADP-ribose) polymerase (PARP) inhibitors, agents targeting immune-suppressive regulators, and repurposed existing drugs. We particularly highlight clinical evidence and trace the ongoing clinical trials to investigate the translational value. Taken together, we conduct a thorough review on emerging agents for gynecological cancer treatment and further discuss their potential challenges and future opportunities.

Arginine shortage induces replication stress and confers genotoxic resistance by inhibiting histone H4 translation and promoting PCNA ubiquitination

The arginine dependency of cancer cells creates metabolic vulnerability. In this study, we examine the impact of arginine availability on DNA replication and genotoxicity resistance. Using DNA combing assays, we find that limiting extracellular arginine results in the arrest of cancer cells at S phase and a slowing or stalling of DNA replication. The translation of new histone H4 is arginine dependent and influences DNA replication. Increased proliferating cell nuclear antigen (PCNA) occupancy and helicase-like transcription factor (HLTF)-catalyzed PCNA K63-linked polyubiquitination protect arginine-starved cells from DNA damage. Arginine-deprived cancer cells display tolerance to genotoxicity in a PCNA K63-linked polyubiquitination-dependent manner. Our findings highlight the crucial role of extracellular arginine in nutrient-regulated DNA replication and provide potential avenues for the development of cancer treatments.

Arginine shortage induces replication stress and confers genotoxic resistance by inhibiting histone H4 translation and promoting PCNA polyubiquitination

The unique arginine dependencies of cancer cell proliferation and survival creates metabolic vulnerability. Here, we investigate the impact of extracellular arginine availability on DNA replication and genotoxic resistance. Using DNA combing assays, we find that when extracellular arginine is limited, cancer cells are arrested at S-phase and DNA replication forks slow or stall instantly until arginine is re-supplied. The translation of new histone H4 is arginine-dependent and impacts DNA replication and the expression of newly synthesized histone H4 is reduced in the avascular nutrient-poor breast cancer xenograft tumor cores. Furthermore, we demonstrate that increased PCNA occupancy and HLTF-catalyzed PCNA K63-linked polyubiquitination protects arginine-starved cells from hydroxyurea-induced, DNA2-catalyzed nascent strand degradation. Finally, arginine-deprived cancer cells are tolerant to genotoxic insults in a PCNA K63-linked polyubiquitination-dependent manner. Together, these findings reveal that extracellular arginine is the "linchpin" for nutrient-regulated DNA replication. Such information could be leveraged to expand current modalities or design new drug targets against cancer.

HLTF promotes hepatocellular carcinoma progression by enhancing SRSF1 stability and activating ERK/MAPK pathway

Helicase-like transcription factor (HLTF) has been found to be involved in the progression of several tumors, but the role of HLTF in hepatocellular carcinoma (HCC) progression has not been studied. Here, our study explored the underlying mechanism of HLTF in HCC progression for the first time. Database analysis and clinical sample examination indicated that HLTF was upregulated in HCC tissues and was related to poor clinicopathological features in patients. Upregulation of HLTF accelerated the growth and metastasis of HCC cells both in vitro and in vivo. Bioinformatics analysis and subsequent experiments revealed that ERK/MAPK signaling pathway activation was vital to HLTF-mediated proliferation and metastasis in HCC cells. Moreover, HLTF was demonstrated to interact with SRSF1 and contribute to its protein stability to activate the ERK/MAPK signaling pathway and enhance HCC growth and metastasis. In addition, miR-511-5p was expressed at a low level in HCC tissues, was negatively correlated HLTF, and regulated HLTF expression. Our study shows that HLTF plays an oncogenic role in HCC progression and provides a novel biomarker and therapeutic target for the diagnosis and treatment of HCC.

Identification of Key Pathways and Establishment of a Seven-Gene Prognostic Signature in Cervical Cancer

Cervical cancer (CC) remains high morbidity and mortality. We aimed to identify critical pathways underlying cervical carcinogenesis and establish a prognostic signature. Six datasets from the gene expression omnibus (GEO) database were used to screen the differentially expressed genes (DEGs) between CC and normal tissues. We used the unions of the DEGs to perform functional analysis. The 108 overlapped DEGs were analyzed to determine a prognostic signature by Cox regression and Lasso analysis based on The Cancer Genome Atlas (TCGA) database. Gene Set Enrichment Analysis (GSEA) and Immune Cell Abundance Identifier (ImmuCellAI) were used to determine the relationships between the signature and biological functions. The PI3K-Akt signaling pathway, the Ras signaling pathway, and the viral carcinogenesis pathway may be critical for CC development. We identified seven genes (PLOD2, DSG2, SPP1, CXCL8, MCM5, HLTF, and KLF4) to construct a risk score formula. Survival analysis showed that the high-risk group indicated a worse prognosis than the low-risk group $\left(p<0.0001\right)$ . The AUC of the prognostic signature was 0.7449, 0.7641, and 0.8146 at 1, 3, and 5 years. We also identified that the signature is an independent prognostic factor. GSEA showed five pathways were relevant to the signature, such as the adherens junction pathway. The signature also affected the abundances of various types of immune cells, such as B cell, CD4+ T cell, and CD8+ T cell. Further, we found that SPP1 was co-expressed with HK3, CD163, CCL3, CLEC5A, MMP8, TREM1, OLR1, and TREM2. The results of Gene Ontology analysis showed that SPP1 and its co-expressed related proteins mainly affected metabolic process, multicellular organismal process, cell communication, cell proliferation, protein binding, and transporter activity. In conclusion, the present study explored the key pathways for CC development and the seven-gene signature can effectively make the prognosis evaluation of CC patients.

microRNAs identified in prostate cancer: Correlative studies on response to ionizing radiation

As the most frequently diagnosed non-skin cancer in men and a leading cause of cancer-related death, understanding the molecular mechanisms that drive treatment resistance in prostate cancer poses a significant clinical need. Radiotherapy is one of the most widely used treatments for prostate cancer, along with surgery, hormone therapy, and chemotherapy. However, inherent radioresistance of tumor cells can reduce local control and ultimately lead to poor patient outcomes, such as recurrence, metastasis and death. The underlying mechanisms of radioresistance have not been fully elucidated, but it has been suggested that miRNAs play a critical role. miRNAs are small non-coding RNAs that regulate gene expression in every signaling pathway of the cell, with one miRNA often having multiple targets. By fine-tuning gene expression, miRNAs are important players in modulating DNA damage response, cell death, tumor aggression and the tumor microenvironment, and can ultimately affect a tumor’s response to radiotherapy. Furthermore, much interest has focused on miRNAs found in biofluids and their potential utility in various clinical applications. In this review, we summarize the current knowledge on miRNA deregulation after irradiation and the associated functional outcomes, with a focus on prostate cancer. In addition, we discuss the utility of circulating miRNAs as non-invasive biomarkers to diagnose, predict response to treatment, and prognosticate patient outcomes.

Prediction of Poor Response to Neoadjuvant Chemoradiation in Patients With Rectal Cancer Using a DNA Repair Deregulation Score: Picking the Losers Instead of the Winners

BACKGROUND

Patients with rectal cancer may undergo neoadjuvant chemoradiation even in early stages in an attempt to achieve complete clinical response and undergo organ preservation. However, prediction of tumor response is unavailable. In this setting, accurate identification of poor responders could spare patients with early stage disease from potentially unnecessary chemoradiation.

OBJECTIVE

This study focused on development/test of a score based on DNA repair gene expression to predict response to neoadjuvant chemoradiation in patients with rectal cancer.

DESIGN

Pretreatment biopsy samples from patients with rectal cancer undergoing neoadjuvant chemoradiation were collected and underwent gene expression analysis using RNA-Seq (test cohort). A score was constructed using 8 differentially expressed DNA repair genes between good (complete clinical) and poor responders (incomplete clinical) to treatment. The score was validated in 2 independent cohorts of patients undergoing similar treatment strategies and using quantitative polymerase chain reaction and microarray gene expression data.

SETTINGS

This was a retrospective analysis of gene expression data from 3 independent institutions.

PATIENTS

Patients with rectal cancer undergoing neoadjuvant chemoradiation (50.4-54.0 Gy and 5-fluorouracil-based chemotherapy) were eligible. Patients with complete clinical response, complete pathological response, or ≤10% residual cancer cells were considered good responders. Patients with >10% residual cancer cells were considered poor responders. The test cohort included 25 patients (16 poor responders). Validation cohort 1 included 28 patients (18 poor responders), and validation cohort 2 included 46 patients (22 poor responders).

MAIN OUTCOMES MEASURES

Response was correlated with the DNA repair score calculated using the expression levels of 8 DNA repair genes. DNA repair score sensitivity, specificity, and positive and negative predictive values were determined in test and validation cohorts.

RESULTS

Poor responders had significantly lower DNA repair scores when compared with good responders across all 3 cohorts, regardless of the gene expression platform used. A low score correctly predicted poor response in 93%, 90%, and 71% in test, validation 1, and validation 2 cohorts.

LIMITATIONS

This study was limited by its small sample size, different gene expression platforms, and treatment regimens across different cohorts used.

CONCLUSIONS

A DNA repair gene score may predict patients likely to have poor response to chemoradiation. This score may be a relevant tool to be investigated in future studies focused on chemoradiation used in the context of organ preservation. See Video Abstract at http://links.lww.com/DCR/B104. PREDICCIÓN DE RESPUESTA DEFICIENTE A LA RADIO-QUIMIOTERAPIA NEOADYUVANTE EN PACIENTES CON CÁNCER RECTAL UTILIZANDO UNA PUNTUACIÓN DE DESREGULACIÓN DE REPARACIÓN DE ADN: ESCOGER LOS PERDEDORES EN LUGAR DE LOS GANADORES: Los pacientes con cáncer rectal pueden someterse a radio-quimioterapia neoadyuvante incluso en estadios tempranos en el intento por lograr una respuesta clínica completa y permitir una preservación de órgano. Sin embargo, aun no existen herramientas disponible para la prediccion de la respuesta tumoral al tratamiento. En este contexto, la identificación precisa de los tumores con mala respuesta al tratamiento podría evitar que los pacientes con enfermedad en estadio temprano sean sometidos a radio-quimioterapia potencialmente innecesaria.Desarrollo / testeo de una puntuación basada en la expresión genes reparadores del ADN para predecir la respuesta a la nCRT en pacientes con cáncer rectal.Se recogieron muestras de biopsia de pre-tratamiento de pacientes con cáncer rectal sometidos a radio-quimioterapia neoadyuvante y se les realizó un análisis de expresión génica utilizando RNAseq (cohorte de prueba). Se construyó una puntuación utilizando 8 genes de reparación de ADN expresados diferencialmente entre buenos (respuesta clinica completa) y pobres respondedores (respuesta clinica incompleta) al tratamiento. La puntuación se validó en 2 cohortes independientes de pacientes sometidos a estrategias de tratamiento similares y utilizando qPCR y datos de expresión de genes en chips ADN (biotecnología -microarrays).Análisis retrospectivo de los datos de expresión génica de 3 instituciones independientes.Fueron incluidos aquellos pacientes con cáncer rectal sometidos a radio-quimioterapia neoadyuvante (50,4-54 Gy y quimioterapia basada en 5FU). Los pacientes con respuesta clínica completa, respuesta patológica completa o ≤10% de células cancerosas residuales se consideraron buenos respondedores. Los pacientes con> 10% de células cancerosas residuales se consideraron de respuesta deficiente. La cohorte de prueba incluyó a 25 pacientes (16 respondedores pobres). La cohorte de validación n. ° 1 incluyó a 28 pacientes (18 respondedores pobres) y la cohorte de validación n. ° 2 incluyó a 46 pacientes (22 respondedores pobres).La respuesta se correlacionó con la puntuación de reparación de ADN calculada utilizando los niveles de expresión de 8 genes de reparación de ADN. La sensibilidad del puntaje de reparación del ADN, la especificidad, los valores predictivos positivos y negativos se determinaron en las cohortes de prueba y validación.Los malos respondedores tuvieron puntuaciones de reparación de ADN significativamente más bajas en comparación con los buenos respondedores en las 3 cohortes, independientemente de la plataforma de expresión génica utilizada. Una puntuación baja predijo correctamente una respuesta pobre en el 93%, 90% y 71% en las cohortes de prueba, validación n. ° 1 y validación n. ° 2, respectivamente.Pequeño tamaño de la muestra, diferentes plataformas de expresión génica y regímenes de tratamiento en diferentes cohortes utilizadas.La puntuacion basada en genes de reparación del ADN puede predecir los pacientes con respuesta pobre a la radio-quimioterapia. Esta puntuación puede ser una herramienta relevante para investigar en futuros estudios centrados en la radio-quimioterapia utilizada en el contexto de la preservación de órganos. Consulte Video Resumen en http://links.lww.com/DCR/B104. (Traducción-Dr. Xavier Delgadillo and Dr. Laura Melina Fernandez).

TRIAP1 knockdown sensitizes non-small cell lung cancer to ionizing radiation by disrupting redox homeostasis

Background

Radioresistance of some non‐small cell lung cancer (NSCLC) types increases the risk of recurrence or metastasis in afflicted patients, following radiotherapy. As such, further improvements to NSCLC radiotherapy are needed. The expression of oncogene TP53‐regulated inhibitor of apoptosis 1 (TRIAP1) in NSCLC is increased following irradiation. Furthermore, gene set enrichment analysis (GSEA) has suggested that TRIAP1 might be involved in maintaining redox homeostasis. This in turn might enhance cell radioresistance.

Methods

In this study we irradiated human NSCLC cell lines (A549 and H460), while knocking down TRIAP1, to determine whether a disrupted redox homeostasis could attenuate radioresistance.

Results

Irradiation notably increased both mRNA and protein levels of TRIAP1. In addition, TRIAP1 knockdown decreased the expression of several antioxidant proteins, including thioredoxin‐related transmembrane protein (TMX) 1, TMX2, thioredoxin (TXN), glutaredoxin (GLRX) 2, GLRX3, peroxiredoxin (PRDX) 3, PRDX4, and PRDX6 in A549 and H460 cells. In addition, silencing TRIAP1 impaired the radiation‐induced increase of the aforementioned proteins. Continuing along this line, we observed a radiation‐induced reduction of cell viability and invasion, as well as increased apoptosis and intracellular reactive oxygen species following TRIAP1 knockdown.

Conclusions

In summary, we identified TRIAP1 as a key contributor to the radioresistance of NSCLC by maintaining redox homeostasis.

miRNA‑30a‑3p inhibits metastasis and enhances radiosensitivity in esophageal carcinoma by targeting insulin‑like growth factor 1 receptor

It has been demonstrated that microRNAs (miRNAs) serve important roles in various biological processes, such as tumorigenesis. In the present study, the role of miR‑30a‑3p in the pathogenesis of esophageal carcinoma (EC) was investigated. Reverse transcription‑quantitative polymerase chain reaction was performed to determine the levels of miR‑30a‑3p expression in EC tissues and cell lines. Then, the effects of miR‑30a‑3p on the migration, invasion and radiosensitivity of EC cells were investigated using scratch‑wound, Transwell and radiosensitivity assays, respectively. A dual‑luciferase reporter assay was performed to determine potential interactions between miR‑30a‑3p and the 3'‑untranslated region (3'‑UTR) of insulin‑like growth factor 1 receptor (IGF‑1R). The results demonstrated that the levels of miR‑30a‑3p expression in EC tissues and cell lines were significantly decreased compared with those in paired healthy tissues and a human esophageal epithelial cell line. Upregulation of miR‑30a‑3p expression significantly suppressed migration, invasion and epithelial‑mesenchymal transition (EMT), and enhanced radiosensitivity in EC cells. Analysis of luciferase activity demonstrated that miR‑30a‑3p interacted with the 3'‑UTR of IGF‑1R, and knockdown of IGF‑1R induced similar effects on the migration, invasion, EMT and radiosensitivity of EC cells. The results indicated that miR‑30a‑3p suppressed metastasis and enhanced the radiosensitivity of EC cells via downregulation IGF‑1R, suggesting that miR‑30a‑3p may be a potential therapeutic target in the treatment of EC.

Alternative splicing of helicase-like transcription factor (Hltf): Intron retention-dependent activation of immune tolerance at the feto-maternal interface

Hltf is regulated by intron retention, and global Hltf-deletion causes perinatal lethality from hypoglycemia. In heart, full-length Hltf is a transcriptional regulator of Hif-1α that controls transport systems. Thus, we tested the hypothesis that Hltf deletion from placenta caused or exacerbated neonatal hypoglycemia via Hif-1α regulation of nutrient transporters. RNA-seq data analyses identified significant changes in transcript expression and alternative splicing (AS) in E18.5 placentome. iPathwayGuide was used for gene ontology (GO) analysis of biological processes, molecular functions and cellular components. Elim pruning algorithm identified hierarchical relationships. The methylome was interrogated by Methyl-MiniSeq Epiquest analysis. GO analysis identified gene enrichment within biological processes. Protein expression was visualized with immunohistochemistry. Although two Hltf mRNA isoforms are quantifiable in most murine tissues, only the truncated Hltf isoform is expressed in placenta. The responsible intron retention event occurs in the absence of DNA methylation. iPathwayGuide analysis identified 157 target genes of 11,538 total genes with measured expression. These were obtained using a threshold of 0.05 for statistical significance (p-value) and a long fold change of expression with absolute value of at least 0.6. Hltf deletion altered transcription of trophoblast lineage-specific genes, and increased transcription of the Cxcr7 (p = 0.004) gene whose protein product is a co-receptor for human and simian immunodeficiency viruses. Concomitant increased Cxcr7 protein was identified with immunolabeling. Hltf deletion had no effect on transcription or site-specific methylation patterns of Hif-1α, the major glucose transporters, or System A amino acid transporters. There was no measureable evidence of uteroplacental dysfunction or fetal compromise. iPathGuide analysis revealed Hltf suppresses cytolysis (10/21 genes; p-value 1.900e-12; p-value correction: Elim pruning; GO:019835) including the perforin-granzyme pathway in uterine natural killer cells. Our findings 1) prove the truncated Hltf protein isoform is a transcription factor, 2) establish a functional link between AS of Hltf and immunosuppression at the feto-maternal interface, 3) correlate intron retention with the absence of DNA methylation, and 4) underscore the importance of differential splicing analysis to identify Hltf's functional diversity.

Identification of strong intron enhancer in the heparanase gene: effect of functional rs4693608 variant on HPSE enhancer activity in hematological and solid malignancies

Heparanase is an endo-β-glucuronidase that specifically cleaves the saccharide chains of heparan sulfate (HS) proteoglycans and releases HS-bound cytokines, chemokines, and bioactive growth-promoting factors. Heparanase plays an important role in the nucleus as part of an active chromatin complex. Our previous studies revealed that rs4693608 correlates with heparanase levels and increased risk of acute and extensive chronic graft vs. host disease (GVHD). Discrepancy between recipient and donor in this SNP significantly affected the risk of acute GVHD. In the present study, we analyzed the HPSE gene region, including rs4693608, and demonstrated that this region exhibits SNPs-dependent enhancer activity. Analysis of nuclear proteins from normal leukocytes revealed their binding to DNA probe of both alleles with higher affinity to allele G. All malignant cell lines and leukemia samples disclosed a shift of the main bands in comparison to normal leukocytes. At least five additional shifted bands were bound to allele A while allele G probe was bound to only one main DNA/protein complex. Additional SNPs rs4693083, rs4693084, and rs4693609 were found in strong linkage disequilibrium (LD) with rs11099592 (exon 7). Only rs4693084 affected protein binding to DNA in cell lines and leukemia samples. As a result of the short distance between rs4693608 and rs4693084, both SNPs may be included in a common DNA/protein complex. DNA pull-down assay revealed that heparanase is involved in self-regulation by negative feedback in rs4693608-dependent manner. During carcinogenesis, heparanase self-regulation is discontinued and the helicase-like transcription factor begins to regulate this enhancer region. Altogether, our study elucidates conceivable mechanism(s) by which rs4693608 SNP regulates HPSE gene expression and the associated disease outcome.

The role of SMARCAL1 in replication fork stability and telomere maintenance

SMARCAL1 (SWI/SNF Related, Matrix Associated, Actin Dependent Regulator Of Chromatin, Subfamily A-Like 1), also known as HARP, is an ATP-dependent annealing helicase that stabilizes replication forks during DNA damage. Mutations in this gene are the cause of Schimke immune-osseous dysplasia (SIOD), an autosomal recessive disorder characterized by T-cell immunodeficiency and growth dysfunctions. In this review, we summarize the main roles of SMARCAL1 in DNA repair, telomere maintenance and replication fork stability in response to DNA replication stress.

The helicase-like transcription factor (HLTF) in cancer: loss of function or oncomorphic conversion of a tumor suppressor?

The Helicase-like Transcription Factor (HLTF) belongs to the SWI/SNF family of proteins involved in chromatin remodeling. In addition to its role in gene transcription, HLTF has been implicated in DNA repair, which suggests that this protein acts as a tumor suppressor. Accumulating evidence indicates that HLTF expression is altered in various cancers via two mechanisms: gene silencing through promoter hypermethylation or alternative mRNA splicing, which leads to the expression of truncated proteins that lack DNA repair domains. In either case, the alteration of HLTF expression in cancer has a poor prognosis. In this review, we gathered published clinical and molecular data on HLTF. Our purposes are (a) to address whether HLTF alterations could be considered as cancer drivers or passengers and (b) to determine whether its different functions (transcription or DNA repair) could be diverted in clonal selection during cancer progression.

Rad5 template switch pathway of DNA damage tolerance determines synergism between cisplatin and NSC109268 in Saccharomyces cerevisiae

The success of cisplatin (CP) based therapy is often hindered by acquisition of CP resistance. We isolated NSC109268 as a compound altering cellular sensitivity to DNA damaging agents. Previous investigation revealed an enhancement of CP sensitivity by NSC109268 in wild-type Saccharomyces cerevisiae and CP-sensitive and -resistant cancer cell lines that correlated with a slower S phase traversal. Here, we extended these studies to determine the target pathway(s) of NSC109268 in mediating CP sensitization, using yeast as a model. We reasoned that mutants defective in the relevant target of NSC109268 should be hypersensitive to CP and the sensitization effect by NSC109268 should be absent or strongly reduced. A survey of various yeast deletion mutants converged on the Rad5 pathway of DNA damage tolerance by template switching as the likely target pathway of NSC109268 in mediating cellular sensitization to CP. Additionally, cell cycle delays following CP treatment were not synergistically influenced by NSC109268 in the CP hypersensitive rad5Δ mutant. The involvement of the known inhibitory activities of NSC109268 on 20S proteasome and phosphatases 2Cα and 2A was tested. In the CP hypersensitive ptc2Δptc3Δpph3Δ yeast strain, deficient for 2C and 2A-type phosphatases, cellular sensitization to CP by NSC109268 was greatly reduced. It is therefore suggested that NSC109268 affects CP sensitivity by inhibiting the activity of unknown protein(s) whose dephosphorylation is required for the template switch pathway.

Network motifs in the transcriptional regulation network of cervical carcinoma cells respond to EGF

PURPOSE

Cervical carcinoma is the second most prevalent and the fifth most deadly malignancy seen in women worldwide. Dysregulated activation of EGF ErbB system has been implicated in diverse types of human cancer; however, it is elusive how it is regulated in human cervical cancer cells. We herein aimed to explore the mechanisms of cervical carcinoma response to epidermal growth factor (EGF), with a view of the pathways activated by EGF.

METHODS

Using the GSE6783 affymetrix microarray data accessible from gene expression omnibus database, we first identified the differentially expressed genes between EGF-stimulated and -unstimulated samples. Then we constructed a regulation network and identified the network motifs. We also performed biological process and pathway enrichment analyses to functionally classify the genes in the regulation network.

RESULTS

A total of 11 network motifs were identified in the regulation network. EGF treatment could increase the risk of cancer via dysregulation of cancer-related pathways and immune response pathways.

CONCLUSIONS

Network motif analysis is useful in mining the useful information underlying the network. We hope our work could serve as a basis for further experimentation.