Defective ALC1 nucleosome remodeling confers PARPi sensitization and synthetic lethality with HRD.

Chromatin is a barrier to efficient DNA repair, as it hinders access and processing of certain DNA lesions. ALC1/CHD1L is a nucleosome-remodeling enzyme that responds to DNA damage, but its precise function in DNA repair remains unknown. Here we report that loss of ALC1 confers sensitivity to PARP inhibitors, methyl-methanesulfonate, and uracil misincorporation, which reflects the need to remodel nucleosomes following base excision by DNA glycosylases but prior to handover to APEX1. Using CRISPR screens, we establish that ALC1 loss is synthetic lethal with homologous recombination deficiency (HRD), which we attribute to chromosome instability caused by unrepaired DNA gaps at replication forks. In the absence of ALC1 or APEX1, incomplete processing of BER intermediates results in post-replicative DNA gaps and a critical dependence on HR for repair. Hence, targeting ALC1 alone or as a PARP inhibitor sensitizer could be employed to augment existing therapeutic strategies for HRD cancers.

Characterization of the AGR2 Interactome Uncovers New Players of Protein Disulfide Isomerase Network in Cancer Cells.

Anterior gradient 2 (AGR2) is an endoplasmic reticulum (ER)-resident protein disulfide isomerase (PDI) known to be overexpressed in many human epithelial cancers and is involved in cell migration, cellular transformation, angiogenesis, and metastasis. This protein inhibits the activity of the tumor suppressor p53, and its expression levels can be used to predict cancer patient outcome. However, the precise network of AGR2-interacting partners and clients remains to be fully characterized. Herein, we used label-free quantification and also stable isotope labeling with amino acids in cell culture-based LC-MS/MS analyses to identify proteins interacting with AGR2. Functional annotation confirmed that AGR2 and its interaction partners are associated with processes in the ER that maintain intracellular metabolic homeostasis and participate in the unfolded protein response, including those associated with changes in cellular metabolism, energy, and redox states in response to ER stress. As a proof of concept, the interaction between AGR2 and PDIA3, another ER-resident PDI, was studied in more detail. Pathway analysis revealed that AGR2 and PDIA3 play roles in protein folding in ER, including post-translational modification and in cellular response to stress. We confirmed the AGR2-PDIA3 complex formation in cancer cells, which was enhanced in response to ER stress. Accordingly, molecular docking characterized potential quaternary structure of this complex; however, it remains to be elucidated whether AGR2 rather contributes to PDIA3 maturation in ER, the complex directly acts in cellular signaling, or mediates AGR2 secretion. Our study provides a comprehensive insight into the protein-protein interaction network of AGR2 by identifying functionally relevant proteins and related cellular and biochemical pathways associated with the role of AGR2 in cancer cells.

Identification of AGR2 Gene-Specific Expression Patterns Associated with Epithelial-Mesenchymal Transition.

The TGF-ß signaling pathway is involved in numerous cellular processes, and its deregulation may result in cancer development. One of the key processes in tumor progression and metastasis is epithelial to mesenchymal transition (EMT), in which TGF-ß signaling plays important roles. Recently, AGR2 was identified as a crucial component of the cellular machinery responsible for maintaining the epithelial phenotype, thereby interfering with the induction of mesenchymal phenotype cells by TGF-ß effects in cancer. Here, we performed transcriptomic profiling of A549 lung cancer cells with CRISPR-Cas9 mediated AGR2 knockout with and without TGF-ß treatment. We identified significant changes in transcripts associated with focal adhesion and eicosanoid production, in particular arachidonic acid metabolism. Changes in transcripts associated with the focal adhesion pathway were validated by RT-qPCR of COL4A1, COL4A2, FLNA, VAV3, VEGFA, and VINC mRNAs. In addition, immunofluorescence showed the formation of stress fibers and vinculin foci in cells without AGR2 and in response to TGF-ß treatment, with synergistic effects observed. These findings imply that both AGR2 downregulation and TGF-ß have a role in focal adhesion formation and cancer cell migration and invasion. Transcripts associated with arachidonic acid metabolism were downregulated after both AGR2 knockout and TGF-ß treatment and were validated by RT-qPCR of GPX2, PTGS2, and PLA2G4A. Since PGE2 is a product of arachidonic acid metabolism, its lowered concentration in media from AGR2-knockout cells was confirmed by ELISA. Together, our results demonstrate that AGR2 downregulation and TGF-ß have an essential role in focal adhesion formation; moreover, we have identified AGR2 as an important component of the arachidonic acid metabolic pathway.

Regulation of AGR2 expression via 3'UTR shortening.

One recently discussed general mechanism affecting gene expression is 3'-untranslated region (3'UTR) length. Events such as shortening, translocation or loss of 3'UTRs are observed within oncogenes and are proposed to associate with increased expression. Thus, increased efforts are being made to understand constitutive and differential transcript 3'end formation. Investigation of AGR2 mRNA revealed a direct impact of its 3'UTR length on AGR2 expression. In silico analyses identified several regulatory sequences within the distal part of AGR2 mRNA that may regulate 3'UTR length and associated protein levels. Short 3'UTRs were observed in a panel of AGR2-positive cancer cell lines and in human breast cancer specimens, in which more extensive 3'UTR shortening correlated with increased AGR2 protein levels. AGR2 is an important member of PI3K/AKT signalling pathway, which along with the proposed involvement of mTOR in the regulation of alternative polyadenylation, prompted us to study the role of mTOR in relation to AGR2 mRNA 3'UTR shortening. A direct impact of mTOR signalling on AGR2 3'UTR shortening associated with increased protein synthesis was found, which led to the identification of a novel molecular mechanism involved in upregulation of AGR2 levels in mTOR-activated cells via modulating the 3'UTR length of AGR2 mRNA.

[New Approaches for Chemosensitivity Testing in Malignant Diseases]. / Nové moznosti testování chemosenzitivity u nádorových onemocnení.

BACKGROUND: Due to the irreplaceable role of chemotherapy in cancer treatment, research has focused on improving the efficacies of individual drugs and minimizing, or completely suppressing, their negative side effects. Based on long-term experience and the results of clinical trials, the selection of appropriate treatment is currently based on classical clinical diagnostic criteria, such as tumor size, grade, and the presence or absence of standard markers. However, complications arise due to variability between patients and tumor heterogeneity. Characterization of intratumoral heterogeneity and acquisition of more reliable drug performance indicators should improve personalized therapy. Development and selection of suitable models are therefore important issues in cancer research focused on predicting sensitivity to therapy. AIM: This work provides an overview of various chemosensitivity tests that have been previously employed and those that are currently used. Great emphasis is placed on comparing 2D and 3D cell culture models, since their importance and popularity are increasing. Particular attention is paid to in vivo systems, which have significantly improved recently and are tested in clinical trials to predict responses to therapy. CONCLUSION: This work provides a brief overview of chemosensitivity tests, focusing on the importance of individual tests and their application in decision-making and patient stratification to improve the clinical responses of patients and the development of targeted personalized therapy.Key words: cell culture techniques - personalized medicine - drug screening - biological models - tumor cell lines - carcinoma - cytotoxicity assays This work was supported by the project MEYSNPS I-LO1413 and GACR 17-05838S. The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers.Submitted: 21. 9. 2017Accepted: 20. 12. 2017.

Tamoxifen-Dependent Induction of AGR2 Is Associated with Increased Aggressiveness of Endometrial Cancer Cells.

Tamoxifen treatment in breast cancer patients is associated with increased risk of endometrial malignancies. Significantly, higher AGR2 expression was found in endometrial cancers that developed in women previously treated with tamoxifen compared to those who had not been exposed to tamoxifen. An association of elevated AGR2 level with myometrial invasion occurrence and invasion depth was also found. In vitro analyses identified a stimulatory effect of AGR2 on cellular proliferation. Although adverse tamoxifen effects on endometrial cells remain elusive, our work identifies elevated AGR2 as a candidate tamoxifen-dependent mechanism of action responsible for increased incidence of endometrial cancer.

Suppression of AGR2 in a TGF-ß-induced Smad regulatory pathway mediates epithelial-mesenchymal transition.

BACKGROUND: During cancer progression, epithelial cancer cells can be reprogrammed into mesenchymal-like cells with increased migratory potential through the process of epithelial-mesenchymal transition (EMT), representing an essential step of tumor progression towards metastatic state. AGR2 protein was shown to regulate several cancer-associated processes including cellular proliferation, survival and drug resistance. METHODS: The expression of AGR2 was analyzed in cancer cell lines exposed to TGF-ß alone or to combined treatment with TGF-ß and the Erk1/2 inhibitor PD98059 or the TGF-ß receptor specific inhibitor SB431542. The impact of AGR2 silencing by specific siRNAs or CRISPR/Cas9 technology on EMT was investigated by western blot analysis, quantitative PCR, immunofluorescence analysis, real-time invasion assay and adhesion assay. RESULTS: Induction of EMT was associated with decreased AGR2 along with changes in cellular morphology, actin reorganization, inhibition of E-cadherin and induction of the mesenchymal markers vimentin and N-cadherin in various cancer cell lines. Conversely, induction of AGR2 caused reversion of the mesenchymal phenotype back to the epithelial phenotype and re-acquisition of epithelial markers. Activated Smad and Erk signaling cascades were identified as mutually complementary pathways responsible for TGF-ß-mediated inhibition of AGR2. CONCLUSION: Taken together our results highlight a crucial role for AGR2 in maintaining the epithelial phenotype by preventing the activation of key factors involved in the process of EMT.

AGR2 associates with HER2 expression predicting poor outcome in subset of estrogen receptor negative breast cancer patients.

Expression of the AGR2 oncogene was shown to be associated with estrogen receptor positive tumors. This gene contributes to enhanced cellular proliferation, drug resistance, metastasis development and may also serve as a predictor of poor prognosis. However, our analysis of AGR2 expression in a subset of estrogen-receptor negative tumors revealed that AGR2 could also be upregulated in hormone-independent manner. AGR2 expression was shown to be significantly increased in HER2 positive breast tumors on both the mRNA and the protein level. Moreover, in a subset of estrogen- and progesterone-receptor negative and simultaneously HER2-positive cases, increased AGR2 expression significantly correlated with worse patient prognosis. Subsequent analysis of independent data sets either collected in our institute or obtained from Oncomine cancer microarray database confirmed all these findings.

AGR2-AGR3 hetero-oligomeric complexes: Identification and characterization.

In this paper we compare electrochemical behavior of two homolog proteins, namely anterior gradient 2 (AGR2) and anterior gradient 3 (AGR3), playing an important role in cancer cell biology. The slight variation in their protein structures has an impact on protein adsorption and orientation at charged surface and also enables AGR2 and AGR3 to form heterocomplexes. We confirm interaction between AGR2 and AGR3 (i) in vitro by immunochemical and constant current chronopotentiometric stripping (CPS) analysis and (ii) in vivo by bioluminescence resonance energy transfer (BRET) assay. Mutation of AGR2 in dimerization domain (E60A) prevents development of wild type AGR2 dimers and also negatively affects interaction with wild type AGR3 as shown by CPS analysis. Beside new information about AGR2 and AGR3 protein including their joint interaction, our work introduces possible applications of CPS in bioanalysis of protein complexes, including those relatively unstable, but important in the cancer research.

ZEB1/miR-200c/AGR2: A New Regulatory Loop Modulating the Epithelial-Mesenchymal Transition in Lung Adenocarcinomas.

Epithelial-mesenchymal transition (EMT) is a process involved not only in morphogenesis and embryonic development, but also in cancer progression, whereby tumor cells obtain a more aggressive metastatic phenotype. Anterior gradient protein 2 (AGR2) maintains the epithelial phenotype and blocks the induction of EMT, thus playing an undeniable role in tumor progression. However, the mechanism through which AGR2 expression is regulated, not only during EMT, but also in the early stages of cancer development, remains to be elucidated. In the present study, we show an inverse correlation of AGR2 with ZEB1 (zinc finger enhancer binding protein, δEF1) that was verified by analysis of several independent clinical data sets of lung adenocarcinomas. We also identified the ZEB1 binding site within the AGR2 promoter region and confirmed AGR2 as a novel molecular target of ZEB1. The overexpression of ZEB1 decreased the promoter activity of the AGR2 gene, which resulted in reduced AGR2 protein level and the acquisition of a more invasive phenotype of these lung cancer cells. Conversely, silencing of ZEB1 led not only to increased levels of AGR2 protein, but also attenuated the invasiveness of tumor cells. The AGR2 knockout, vice versa, increased ZEB1 expression, indicating that the ZEB1/AGR2 regulatory axis may function in a double negative feedback loop. In conclusion, we revealed for the first time that ZEB1 regulates AGR2 at the transcriptional level, while AGR2 presence contributes to ZEB1 mRNA degradation. Thus, our data identify a new regulatory mechanism between AGR2 and ZEB1, two rivals in the EMT process, tightly associated with the development of metastasis.

Ferrocenes as new anticancer drug candidates: Determination of the mechanism of action.

Chemotherapy plays an essential role in the management of cancer worldwide. However, it is a non-specific treatment limited by major drawbacks, thus identification and testing of new promising molecular structures representing potential drug candidates are urgently needed. In this work, ferrocene complexes as potential antitumor drugs that display cytotoxicity in low micromolar concentrations against ovarian cancer cells A2780 and SK-OV-3 were investigated to identify their mode of action. Their mechanism of cellular accumulation was studied using differential pulse voltammetry and inductively coupled plasma - mass spectrometry. Their mode of cell death induction was determined by changes in the mitochondrial membrane potential, production of reactive oxygen species and by Annexin V staining. Transferrin receptors were identified as key mediators of intracellular accumulation of ferrocenes and the extent of cellular uptake reflected the anticancer activity of individual compounds. Functional analysis revealed activation of intrinsic apoptosis as a dominant mechanism leading to regulated cell death induced in ovarian cancer cells by ferrocenes. Ferrocenes represent a group of promising sandwich organometallic complexes exerting cytotoxic activity. We suggest their application not only as standalone chemotherapeutics but also as modifying substituents of known drugs to improve their antitumor effects.

AGR2 silencing contributes to metformin-dependent sensitization of colorectal cancer cells to chemotherapy.

There is growing epidemiological evidence indicating an association between diabetes mellitus and the increased incidence of colorectal cancer (CRC). The preferred initial and most widely used pharmacological agent for the treatment of type 2 diabetes is metformin, which in parallel reduces the risk of CRC and improves patient prognosis. AMP-activated protein kinase (AMPK) appears to be tightly associated with the beneficial metabolic effects of metformin, serving as a cellular energy sensor activated in response to a variety of conditions that deplete cellular energy levels. Such conditions include nutrient starvation (particularly glucose), hypoxia and exposure to toxins that inhibit the mitochondrial respiratory chain complex. The aim of the present study was to determine the effect of metformin on CRC cell lines, with different levels of anterior gradient 2 (AGR2) expression, exposed to 5-fluorouracil (5-FU) and oxaliplatin, alone or in combination with metformin. AGR2 has recently emerged as a factor involved in colon carcinogenesis. In AGR2-knockout cells, markedly higher levels of phosphorylated-AMPK were observed in comparison with control cells transfected with GFP-scrambled guide RNA, which indicated that the presence of AGR2 may interfere with the metformin-dependent activation of AMPK. In addition, metformin in combination with 5-FU and oxaliplatin induced ROS production and attenuated autophagy. This effect was enhanced in AGR2-knockout cells.

The role of miR-409-3p in regulation of HPV16/18-E6 mRNA in human cervical high-grade squamous intraepithelial lesions.

Cervical cancer is one of the most common malignancies in women. MicroRNAs (miRNAs) are involved in a variety of fundamental cellular processes, including carcinogenesis. The potential utilization of aberrantly expressed miRNAs as novel biomarkers in cervical cancer diagnostics is growing. We investigated miRNA expression profiles during the progression of dysplasia in cervical epithelium to identify aberrantly expressed miRNAs. High-throughput miRNA profiling of high-grade precancerous lesions identified 79 miRNAs showing significant difference in expression values compared to normal cervical epithelium. Ten selected miRNAs were subsequently measured in an independent group of samples to validate them as promising biomarkers of cervical carcinogenesis. MicroRNAs miR-10b-5p, miR-34c-5p, miR-409-3p and miR-411-5p were confirmed as downregulated, while miR-10a-5p, miR-132-3p, miR-141-5p were significantly upregulated in dysplastic cervical tissues. Further investigation revealed an inverse correlation of miR-409-3p with E6 mRNA levels in precancerous cervical lesions. Subsequent in vitro analyses showed a direct involvement of this miRNA in the regulation of E6 oncogene levels, thus confirming a potential tumor suppressor function of miR-409-3p in cervical malignancies. Hence, miR-409-3p may represent a useful early marker and a potential therapeutic target for cervical cancer.

Extracellular AGR3 regulates breast cancer cells migration via Src signaling.

Human anterior gradient proteins AGR2 and AGR3 are overexpressed in a variety of adenocarcinomas and are often secreted in cancer patients' specimens, which suggests a role for AGR proteins in intra and extracellular compartments. Although these proteins exhibit high sequence homology, AGR2 is predominantly described as a pro-oncogene and a potential prognostic biomarker. However, little is known about the function of AGR3. Therefore, the aim of the present study was to investigate the role of AGR3 in breast cancer. The results demonstrated that breast cancer cells secrete AGR3. Furthermore, it was revealed that extracellular AGR3 (eAGR3) regulates tumor cell adhesion and migration. The current study indicated that the pharmacological and genetic perturbation of Src kinase signaling, through treatment with Dasatinib (protein kinase inhibitor) or investigating cells that express a dominant-negative form of Src, significantly abrogated eAGR3-mediated breast cancer cell migration. Therefore, the results indicated that eAGR3 may control tumor cell migration via activation of Src kinases. The results of the present study indicated that eAGR3 may serve as a microenvironmental signaling molecule in tumor-associated processes.

Control of anterior GRadient 2 (AGR2) dimerization links endoplasmic reticulum proteostasis to inflammation.

Anterior gradient 2 (AGR2) is a dimeric protein disulfide isomerase family member involved in the regulation of protein quality control in the endoplasmic reticulum (ER). Mouse AGR2 deletion increases intestinal inflammation and promotes the development of inflammatory bowel disease (IBD). Although these biological effects are well established, the underlying molecular mechanisms of AGR2 function toward inflammation remain poorly defined. Here, using a protein-protein interaction screen to identify cellular regulators of AGR2 dimerization, we unveiled specific enhancers, including TMED2, and inhibitors of AGR2 dimerization, that control AGR2 functions. We demonstrate that modulation of AGR2 dimer formation, whether enhancing or inhibiting the process, yields pro-inflammatory phenotypes, through either autophagy-dependent processes or secretion of AGR2, respectively. We also demonstrate that in IBD and specifically in Crohn's disease, the levels of AGR2 dimerization modulators are selectively deregulated, and this correlates with severity of disease. Our study demonstrates that AGR2 dimers act as sensors of ER homeostasis which are disrupted upon ER stress and promote the secretion of AGR2 monomers. The latter might represent systemic alarm signals for pro-inflammatory responses.

Expression and Functional Characterization of miR-34c in Cervical Cancer.

BACKGROUND: Cervical cancer is the fourth most common cancer in women and is usually associated with human papillomavirus infection. Viral infections are usually characterized by morphological changes of epithelial cells; however, it is difficult to determine using recently available screening methods whether the changes are caused by productive infection or by malignant disease. Thus, new efforts are required to find novel diagnostic biomarkers of cervical cancer, such as miRNAs, which are small non-coding RNAs involved in the regulation of gene expression. MATERIALS AND METHODS: miR-34c levels in cervical cancer cell lines were determined by the droplet-digital polymerase chain reaction. Changes in miR-34c expression in vitro were achieved by transient transfection with a specific miRNA mimic and inhibitor oligonucleotides. Cell proliferation was analyzed by crystal violet staining followed by spectrophotometric measurements. The effect on migratory properties was studied using a „scratch“ assay. Western blotting analysis was used to determine the expression of selected proteins. RESULTS: The downregulation of miR-34c expression was associated with a slight increase in cellular proliferation and a significant increase in cell migration. The analysis of miR-34c expression performed on a set of 39 dysplastic tissues and 35 samples of healthy controls subsequently revealed a significant difference (p < 0.01) in the level of this miRNA. CONCLUSION: Comparative expression analysis revealed lower expression of miR-34c in cervical precanceroses than in normal untransformed epithelium. in vitro modulation of miR-34c expression revealed its tumor suppressor role in cervical  malignancies. Key words: cervical cancer - HPV - miRNA - HSIL - hsa-miR-34c - precancerosis This work was supported by the projects MEYS - NPS I - LO1413, P206/12/G151 and MH CZ - DRO (MMCI, 00209805). The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study.  The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers. Accepted: 16. 7. 2018.