Overexpression of the novel human gene, UBE2Q2, in breast cancer

The crosstalk between ubiquitin-conjugating enzyme E2Q1 and p53 in colorectal cancer: An in vitro analysis

Colorectal cancer (CRC) is a prevalent gastrointestinal neoplasm that ranks fourth in terms of cancer-related deaths worldwide. In the process of CRC progression, multiple ubiquitin-conjugating enzymes (E2s) are involved; UBE2Q1 is one of those newly identified E2s that is markedly expressed in human colorectal tumors. Since p53 is a well-known tumor suppressor and defined as a key factor to be targeted by the ubiquitin-proteasome system, we hypothesized that UBE2Q1 might contribute to CRC progression through the modulation of p53. Using the lipofection method, the cultured SW480 and LS180 cells were transfected with the UBE2Q1 ORF-containing pCMV6-AN-GFP vector. Then, quantitative RT-PCR was used to assay the mRNA expression levels of p53's target genes, i.e., Mdm2, Bcl2, and Cyclin E. Moreover, Western blot analysis was performed to confirm the cellular overexpression of UBE2Q1 and assess the protein levels of p53, pre- and post-transfection. The expression of p53's target genes were cell line-dependent except for Mdm2 that was consistent with the findings of p53. The results of Western blotting demonstrated that the protein levels of p53 were greatly lower in UBE2Q1-transfected SW480 cells compared to the control SW480 cells. However, the reduced levels of p53 protein were not remarkable in the transfected LS180 cells compared to the control cells. The suppression of p53 is believed to be the result of UBE2Q1-dependent ubiquitination and its subsequent proteasomal degradation. Furthermore, the ubiquitination of p53 can act as a signal for degradation-independent functions, such as nuclear export and suppressing the p53's transcriptional activities. In this context, the decreased Mdm2 levels can moderate the proteasome-independent mono-ubiquitination of p53. The ubiquitinated p53 modulates the transcriptional levels of target genes. Therefore, the up-modulation of UBE2Q1 may influence the transcriptional activities depending on p53, and thereby contributes to CRC progression through regulating the p53.

Genetic and molecular biology of breast cancer among Iranian patients

Abstract

Background, Breast cancer (BC) is one of the leading causes of cancer related deaths in Iran. This high ratio of mortality had a rising trend during the recent years which is probably associated with late diagnosis.

Main body

Therefore it is critical to define a unique panel of genetic markers for the early detection among our population. In present review we summarized all of the reported significant genetic markers among Iranian BC patients for the first time, which are categorized based on their cellular functions.

Conclusions

This review paves the way of introducing a unique ethnic specific panel of diagnostic markers among Iranian BC patients. Indeed, this review can also clarify the genetic and molecular bases of BC progression among Iranians.

Upregulation of UBE2Q1 via gene copy number gain in hepatocellular carcinoma promotes cancer progression through β-catenin-EGFR-PI3K-Akt-mTOR signaling pathway

Hepatocellular carcinoma (HCC) is the most common type of liver cancer and represents a highly malignant tumor with a poor prognosis. Therapeutic modalities for HCC are limited and generally ineffective. UBE2Q1 is a putative E2 ubiquitin conjugating enzyme, and has been shown to be overexpressed in various types of cancers including HCC. How UBE2Q1 contributes to hepatocarcinogenesis remains unknown. Here, we show that UBE2Q1 is up-regulated in HCC cell lines and in a subset of human HCC tissues. Up-regulation of UBE2Q1 in primary HCC tumors was significantly correlated with shorter overall survival and disease-free survival. Mechanistically, we showed that the frequent up-regulation of UBE2Q1 in HCCs was attributed to the recurrent UBE2Q1 gene copy gain at chromosome 1q21. Functionally, we showed that knockdown of UBE2Q1 reduced HCC cell proliferation, promoted apoptosis via induction of GADD45α, and suppressed orthotopic tumorigenicity both in vitro and in vivo. Inactivation of UBE2Q1 also impeded HCC cell migration and invasion in vitro through regulating EMT process, and suppressed HCC metastasis in vivo. Interestingly, our data revealed a role of UBE2Q1 in the regulation of β-catenin-EGFR-PI3K-Akt-mTOR signaling pathway. Our findings indicate that UBE2Q1 is a candidate oncogene involved in HCC development and progression and therefore a potential therapeutic target in applicable HCC patients.

Screening for the optimal gene and functional gene sets related to breast cancer using differential co-expression and differential expression analysis

OBJECTIVE

To investigate novel gene sets related to breast cancer (BC) using differential co-expression and differential expression (DECODE).

METHODS

T statistics was used to quantify the degree of DE of each gene, and then Z was adopted to quantify the correlation difference between expression levels of two genes. Two optimal thresholds for defining substantial change in DE and DC were selected for each gene using chi-square maximization, and the corresponding gene was defined as the optimal gene. Based on the optimal thresholds, genes were categorized into four partitions with either high or low DC and DE characteristics. Finally, we evaluated the functional relevance of a gene partition with high DE and high DC, and the gene set with best association was considered as the optimal functional gene set.

RESULTS

The optimal thresholds for DC and DE were respective 2.254 and 1.616, and the optimal gene was UBE2Q2L. Based on the optimal thresholds, genes were divided into four partitions including HDE-HDC (875 genes), HED-LDC (8038 genes), LDE-HDC (678 genes), and LDE-LDC (10516 genes). The best associated gene set was ``fatty acid catabolic process'' with 34 HDC and HDE partitions. Among these partitions, UBE2Q2L attained the highest minimum FI gain of 18.973.

CONCLUSION

UBE2Q2L and fatty acid catabolic process might be potentially useful signatures in diagnostic purposes for BC.

Promoter Methylation Status of Two Novel Human Genes, UBE2Q1 and UBE2Q2, in Colorectal Cancer: a New Finding in Iranian Patients

BACKGROUND

The ubiquitin-proteasome system (UPS) degrades a variety of proteins which attach to specific signals. The ubiquitination pathway facilitates degradation of damaged proteins and regulates growth and stress responses. This pathway is altered in various cancers, including acute lymphoblastic leukemia, head and neck squamous cell carcinoma and breast cancer. Recently it has been reported that expression of newly characterized human genes, UBE2Q1 and UBE2Q2, putative members of ubiquitin-conjugating enzyme family (E2), has been also changed in colorectal cancer. Epigenetics is one of the fastest-growing areas of science and nowadays has become a central issue in biological studies of diseases. According to the lack of information about the role of epigenetic changes on gene expression profiling of UBE2Q1 and UBE2Q2, and the presence of CpG islands in the promoter of these two human genes, we decided to evaluate the promoter methylation status of these genes as a first step.

MATERIALS AND METHODS

The promoter methylation status of UBE2Q1 and UBE2Q2 was studied by methylation-specific PCR (MSP) in tumor samples of 60 colorectal cancer patients compared to adjacent normal tissues and 20 non-malignant controls. The frequency of the methylation for each gene was analyzed by chi-square method.

RESULTS

MSP results revealed that UBE2Q2 gene promoter were more unmethylated, while a higher level of methylated allele was observed for UBE2Q1 in tumor tissues compared to the adjacent normal tissues and the non malignant controls.

CONCLUSIONS

UBE2Q1 and UBE2Q2 genes show different methylation profiles in CRC cases.

Induction of cell proliferation, clonogenicity and cell accumulation in S phase as a consequence of human UBE2Q1 overexpression

Ubiquitination is an important cellular mechanism with a pivotal role in the degradation of abnormal or short-lived proteins and the regulation of cell cycle and cell growth. The ubiquitin-proteasome pathway is altered in multiple types of human malignancies, including colorectal cancer (CRC). The alteration in the expression of the novel human gene ubiquitin-conjugating enzyme E2 Q1 (UBE2Q1), as a putative member of the E2 ubiquitin-conjugating enzyme family, has been reported in several malignancies, including carcinoma of the breast, hepatocellular and colorectal cancer, and pediatric acute lymphoblastic leukemia. In the present study, the effect of UBE2Q1 overexpression on cell growth, clonogenicity, motility and cell cycle was investigated in a CRC cell line. The UBE2Q1 gene was cloned in the pCMV6-AN-GFP expression vector. A series of stable transfectants of SW1116 cells overexpressing UBE2Q1 protein were established and confirmed by fluorescence microscopy and western blotting. Using these cells, MTT assay was performed to evaluate cell growth and proliferation, while crystal violet staining was used for clonogenicity assay. Cell cycle analysis was also performed to survey the ratio of cells accumulated in different phases of the cell cycle upon transfection. The motility of these cells was also studied using wound healing assay. UBE2Q1 transfectants exhibited a faster growth in cell culture, increased colony formation capacity and enhanced motility compared with control non-transfected cells and cells transfected with empty vector (mock-transfected cells). UBE2Q1 overexpression also resulted in a significant decrease in the number of cells accumulated in the G0/G1 phase of the cell cycle. The present findings suggest that UBE2Q1 may function as an oncogene that induces proliferation of cancer cells, and could be a novel diagnostic tool and a potential therapeutic target for CRC.

Real-Time qPCR-Based Detection of Circulating Tumor Cells from Blood Samples of Adjuvant Breast Cancer Patients: A Preliminary Study

BACKGROUND

Circulating tumor cells (CTCs) are cells that detach from a primary tumor, circulate through the blood stream and lymphatic vessels, and are considered to be the main reason for remote metastasis. Due to their origin, tumor cells have different gene expression levels than the surrounding blood cells. Therefore, they might be detectable in blood samples from breast cancer patients by real-time quantitative polymerase chain reaction (RT-qPCR).

MATERIALS AND METHODS

Blood samples of healthy donors and adjuvant breast cancer patients were withdrawn and the cell fraction containing white blood cells and tumor cells was enriched by density gradient centrifugation. RNA was isolated and reverse transcribed to cDNA, which was then used in TaqMan real-time PCR against cytokeratin (CK)8, CK18 and CK19. 18S and GAPDH were used as controls.

RESULTS

All 3 CKs were, on average, found to be significantly higher expressed in adjuvant breast cancer samples compared to negative controls, probably due to the presence of CTCs. Unfortunately, gene expression levels could not be correlated to tumor characteristics.

CONCLUSIONS

RT-qPCR could make up a new approach for the detection of CTCs from blood samples of breast cancer patients, but a correlation of the PCR data to gold standard methods in CTC detection would help to further improve the informative value of the qPCR results.

UBE2Q1 in a Human Breast Carcinoma Cell Line: Overexpression and Interaction with p53

The p53 tumor suppressor protein is a principal mediator of growth arrest, senescence, and apoptosis in response to a broad array of cellular damage. p53 is a substrate for the ubiquitin-proteasome system, however, the ubiquitin-conjugating enzymes (E2s) involved in p53 ubiquitination have not been well studied. UBE2Q1 is a novel E2 ubiquitin conjugating enzyme gene. Here, we investigated the effect of UBE2Q1 overexpression on the level of p53 in the MDA-MB-468 breast cancer cell line as well as the interaction between UBE2Q1 and p53. By using a lipofection method, the p53 mutated breast cancer cell line, MDA-MB-468, was transfected with the vector pCMV6-AN-GFP, containing UBE2Q1 ORF. Western blot analysis was employed to verify the overexpression of UBE2Q1 in MDA-MB-468 cells and to evaluate the expression level of p53 before and after cell transfection. Immunoprecipitation and GST pull-down protocols were used to investigate the binding of UBE2Q1 to p53. We established MDA-MB-468 cells that transiently expressed a GFP fusion proteins containing UBE2Q1 (GFP-UBE2Q1). Western blot analysis revealed that levels of p53 were markedly lower in UBE2Q1 transfected MDA-MB-468 cells as compared with control MDA-MB-468 cells. Both in vivo and in vitro data showed that UBE2Q1 co-precipitated with p53 protein. Our data for the first time showed that overexpression of UBE2Q1can lead to the repression of p53 in MDA-MB-468 cells. This repression of p53 may be due to its UBE2Q1 mediated ubiquitination and subsequent proteasome degradation, a process that may involve direct interaction of UBE2Q1with p53.

Trial Watch: Proteasomal inhibitors for anticancer therapy

The so-called "ubiquitin-proteasome system" (UPS) is a multicomponent molecular apparatus that catalyzes the covalent attachment of several copies of the small protein ubiquitin to other proteins that are generally (but not always) destined to proteasomal degradation. This enzymatic cascade is crucial for the maintenance of intracellular protein homeostasis (both in physiological conditions and in the course of adaptive stress responses), and regulates a wide array of signaling pathways. In line with this notion, defects in the UPS have been associated with aging as well as with several pathological conditions including cardiac, neurodegenerative, and neoplastic disorders. As transformed cells often experience a constant state of stress (as a result of the hyperactivation of oncogenic signaling pathways and/or adverse microenvironmental conditions), their survival and proliferation are highly dependent on the integrity of the UPS. This rationale has driven an intense wave of preclinical and clinical investigation culminating in 2003 with the approval of the proteasomal inhibitor bortezomib by the US Food and Drug Administration for use in multiple myeloma patients. Another proteasomal inhibitor, carfilzomib, is now licensed by international regulatory agencies for use in multiple myeloma patients, and the approved indications for bortezomib have been extended to mantle cell lymphoma. This said, the clinical activity of bortezomib and carfilzomib is often limited by off-target effects, innate/acquired resistance, and the absence of validated predictive biomarkers. Moreover, the antineoplastic activity of proteasome inhibitors against solid tumors is poor. In this Trial Watch we discuss the contribution of the UPS to oncogenesis and tumor progression and summarize the design and/or results of recent clinical studies evaluating the therapeutic profile of proteasome inhibitors in cancer patients.

Upregulated expression of ubiquitin-conjugating enzyme E2Q1 (UBE2Q1) is associated with enhanced cell proliferation and poor prognosis in human hapatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer in the world. Ubiquitin-proteasome system has been shown to play a pivotal role in the pathophysiology of HCC and other malignancies. UBE2Q1 is a putative E2 ubiquitin conjugating enzyme, and may be involved in the regulation of cancer-related proteins. In this study, we investigated the expression pattern of UBE2Q1 in HCC cell lines and human HCC specimens, and its potential clinical and biological significance in HCC. Western blot and immunohistochemical analyses revealed that UBE2Q1 was significantly upregulated in HCC tumorous tissues compared with the adjacent noncancerous ones. Next, univariate and multivariate survival analyses were performed to determine the prognostic significance of UBE2Q1 in HCC. The results showed that upregulated expression of UBE2Q1 was positively correlated with high histological grades of HCC and predicted poor prognosis. In addition, the expression of UBE2Q1 was progressively increased in serum-refed HCC cells. UBE2Q1 depletion by small interfering RNA inhibited cell proliferation and led to G1 phase arrest in HepG2 and BEL-7404 cells. Furthermore, we showed that cells transfected with UBE2Q1-targeting siRNA resulted in significant increase in the levels of p53, p21 in HepG2 and BEL-7404 cells. These data imply that UBE2Q1 is upregulated in liver cancer cell lines and tumorous samples and may play a role in the development of HCC.

A complex regulatory network coordinating cell cycles during C. elegans development is revealed by a genome-wide RNAi screen

The development and homeostasis of multicellular animals requires precise coordination of cell division and differentiation. We performed a genome-wide RNA interference screen in Caenorhabditis elegans to reveal the components of a regulatory network that promotes developmentally programmed cell-cycle quiescence. The 107 identified genes are predicted to constitute regulatory networks that are conserved among higher animals because almost half of the genes are represented by clear human orthologs. Using a series of mutant backgrounds to assess their genetic activities, the RNA interference clones displaying similar properties were clustered to establish potential regulatory relationships within the network. This approach uncovered four distinct genetic pathways controlling cell-cycle entry during intestinal organogenesis. The enhanced phenotypes observed for animals carrying compound mutations attest to the collaboration between distinct mechanisms to ensure strict developmental regulation of cell cycles. Moreover, we characterized ubc-25, a gene encoding an E2 ubiquitin-conjugating enzyme whose human ortholog, UBE2Q2, is deregulated in several cancers. Our genetic analyses suggested that ubc-25 acts in a linear pathway with cul-1/Cul1, in parallel to pathways employing cki-1/p27 and lin-35/pRb to promote cell-cycle quiescence. Further investigation of the potential regulatory mechanism demonstrated that ubc-25 activity negatively regulates CYE-1/cyclin E protein abundance in vivo. Together, our results show that the ubc-25-mediated pathway acts within a complex network that integrates the actions of multiple molecular mechanisms to control cell cycles during development.

UBE2Q1 expression in human colorectal tumors and cell lines

Colorectal cancer is the third most common cancer in the world. Ubiquitin-proteasome system has shown to be activated in colorectal and other malignancies. UBE2Q1 is a novel human gene that encodes a putative E2 ubiquitin conjugating enzyme. Here, we investigated the expression pattern of UBE2Q1 gene in cell lines and tissues from human colorectal tumors. Quantitative (q) RT-PCR were employed to evaluate the expression levels of the mRNA for UBE2Q1 in colorectal cancer cell lines (HT29/219, LS180, SW742, Caco2, HTC116, SW48, SW480 and SW1116). Expression of UBE2Q1 at the protein levels were assessed by Western blotting in cell lines as well as in 43 human colorectal tumor tissues. All cell lines tested expressed UBE2Q1 gene at the level of both mRNA and protein, with the SW1116 line representing the lowest level of expression. The cell lines HT29/219 and SW742 showed the highest levels of UBE2Q1 protein and mRNA respectively. When compared to corresponding normal tissues, malignant parts of colorectal tumors showed increased levels of UBE2Q1 immunoreactivity in 32 (74.42 %) of cases. These data suggest that UBE2Q1 is differentially expressed in colorectal cell lines and shows overexpression in colorectal tumors.

Detection of Circulating Tumour Cells from Blood of Breast Cancer Patients via RT-qPCR

Breast cancer is still the most frequent cause of cancer-related death in women worldwide. Often death is not caused only by the primary tumour itself, but also by metastatic lesions. Today it is largely accepted, that these remote metastases arise out of cells, which detach from the primary tumour, enter circulation, settle down at secondary sites in the body and are called Circulating Tumour Cells (CTCs). The occurrence of such minimal residual diseases in the blood of breast cancer patients is mostly linked to a worse prognosis for therapy outcome and overall survival. Due to their very low frequency, the detection of CTCs is, still a technical challenge. RT-qPCR as a highly sensitive method could be an approach for CTC-detection from peripheral blood of breast cancer patients. This assumption is based on the fact that CTCs are of epithelial origin and therefore express a different gene panel than surrounding blood cells. For the technical approach it is necessary to identify appropriate marker genes and to correlate their gene expression levels to the number of tumour cells within a sample in an in vitro approach. After that, samples from adjuvant and metastatic patients can be analysed. This approach may lead to new concepts in diagnosis and treatment.

Detection of tumor cell-specific mRNA in the peripheral blood of patients with breast cancer—evaluation of several markers with real-time reverse transcription-PCR

It is widely known that cells from epithelial tumors, e.g., breast cancer, detach from their primary tissue and enter blood circulation. We show that the presence of circulating tumor cells (CTCs) in samples of patients with primary and metastatic breast cancer can be detected with an array of selected tumor-marker-genes by reverse transcription real-time PCR. The focus of the presented work is on detecting differences in gene expression between healthy individuals and adjuvant and metastatic breast cancer patients, not an accurate quantification of these differences. Therefore, total RNA was isolated from blood samples of healthy donors and patients with primary or metastatic breast cancer after enrichment of mononuclear cells by density gradient centrifugation. After reverse transcription real-time PCR was carried out with a set of marker genes (BCSP, CK8, Her2, MGL, CK18, CK19). B2M and GAPDH were used as reference genes. Blood samples from patients with metastatic disease revealed increased cytokine gene levels in comparison to normal blood samples. Detection of a single gene was not sufficient to detect CTCs by reverse transcription real-time PCR. Markers used here were selected based on a recent study detecting cancer cells on different protein levels. The combination of such a marker array leads to higher and more specific discovery rates, predominantly in metastatic patients. Identification of CTCs by PCR methods may lead to better diagnosis and prognosis and could help to choose an adequate therapy.

Ubiquitin- and ubiquitin-like proteins-conjugating enzymes (E2s) in breast cancer

Breast cancer is the most common malignancy in women and a significant cause of morbidity and mortality. Sub-types of breast cancer defined by the expression of steroid hormones and Her2/Neu oncogene have distinct prognosis and undergo different therapies. Besides differing in their phenotype, sub-types of breast cancer display various molecular lesions that participate in their pathogenesis. BRCA1 is one of the common hereditary cancer predisposition genes and encodes for an ubiquitin ligase. Ubiquitin ligases or E3 enzymes participate together with ubiquitin activating enzyme and ubiquitin conjugating enzymes in the attachment of ubiquitin (ubiquitination) in target proteins. Ubiquitination is a post-translational modification regulating multiple cell functions. It also plays important roles in carcinogenesis in general and in breast carcinogenesis in particular. Ubiquitin conjugating enzymes are a central component of the ubiquitination machinery and are often perturbed in breast cancer. This paper will discuss ubiquitin and ubiquitin-like proteins conjugating enzymes participating in breast cancer pathogenesis, their relationships with other proteins of the ubiquitination machinery and their role in phenotype of breast cancer sub-types.

Interplay between membrane lipid peroxidation, transglutaminase activity, and cyclooxygenase 2 expression in the tissue adjoining to breast cancer

Breast cancer, a leading cause of cancer related deaths worldwide, is one of the most common neoplasms in women. The increased generation of reactive oxygen species (ROS) in breast lesion is critically involved in the mutagenic processes that drive to breast carcinoma initiation and progression. To date, the molecular events occurring in the tissue adjoin the cancer lesion have not been elucidated. Here, we investigated the role of excess ROS generation during human breast carcinogenesis by evaluating oxidative stress biomarkers, tissue transglutaminase (t-TGase) activity, and expression levels of ubiquitin and cyclooxygenase-2 (COX-2) in the normal tissue adjoin to fibroadenoma (nFA), atypical ductal hyperplasia (nADH), and invasive ductal carcinoma (nIDC) from 45 breast cancer patients. We found that lipid peroxidation and nitric oxide production significantly increased in nIDC respect to nFA and nADH (P < 0.005) whereas the 4-hydroxy-2-nonenal (HNE) protein-adducts increased only in nADH (P < 0.005). The increased lipid damage observed in nIDC correlates with estrogen receptor exposure in IDC (R(2) = 0.89). Moreover, nIDC and invasive ductal carcinoma (IDC) showed a 10-fold higher t-TGase activity compared to nFA and nADH. Contrary, COX-2 expression levels significantly decreased nIDC and IDC respect to the nFA and nADH (P < 0.001). The analysis of the free ubiquitin expression revealed equal levels in nADH and nIDC samples whereas high molecular weight-ubiquitin conjugate increased about fivefold only in nIDC (P < 0.01 vs. nADH). These novel findings reveal an interplay between membrane lipid peroxidation, t-TGase activity, and COX-2 expression levels in the tissue adjoining to neoplastic lesion during breast cancer progression.

Expression of the novel human gene, UBE2Q1, in breast tumors

The novel human gene, designated ubiquitin-conjugating enzyme E2Q family member 1 (UBE2Q1) maps to chromosome 1q21.3. The gene has an open reading frame corresponding to 422 amino acids and contains a RWD domain and an E2 ubiquitin conjugating enzyme domain. Here, we investigated the expression levels of both mRNA and protein of UBE2Q1 gene in cancerous versus normal parts of breast specimens from 26 patients. Real-time PCR data showed that the relative expression level of UBE2Q1 mRNA was significantly greater in cancers than in non-cancerous tissues of breast specimens (Mean ± SEM, 0.064 ± 0.015 for cancers and 0.026 ± 0.01 for noncancerous tissues, P < 0.05 Mann-Whitney test). A rabbit polyclonal antibody was generated against an amino acid sequence predicted from the DNA sequence of UBE2Q1 gene. This antibody was used to perform Western blotting on 21 cases in our cohort of breast specimens. Thus, 13 (61.904%) of the cases showed an increase in the UBE2Q1 immunoreactivity in their cancerous tissues as compared with the corresponding normal tissues. This result along with the real-time PCR data shows that the novel human gene, UBE2Q1, is expressed in human breast and may have implications for pathogenesis of breast cancer.