Browsing by Subject "EGFR"

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Open Access
Functional effects of ATAD2 gene expression in breast cancer
(2016-08) Özel, Buse Nurten
The ATAD2 gene is a newly investigated gene of which the expression levels are associated with the disease prognosis in many types of cancer and especially breast cancer and that is known to be overexpressed usually through gene amplification and E2F/RB pathway activation. ATAD2 (ATPase family, AAA domain-containing 2) can be overexpressed due to amplification or other regulatory mechanisms in many cancers such as lung, breast, prostate and liver. The fact that ATAD2 has an AAA+ ATPase and bromodomain indicates that it may be a good target for anti-cancer therapy. However, it is necessary to clarify the role of the ATAD2 gene in tumorigenesis before strategies that target ATAD2 are developed. We evaluated a regulator that consistently shows high expression in breast cancer in this study. ATAD2 (ATPase family AAA domain-containing protein 2) is a gene that regulates important cellular activities such as cell proliferation and invasion. This study aimed to clarify the mechanism of action of ATAD2 in breast cancer. The ATAD2 expression of the MCF7 and T47D cell lines with high ATAD2 gene expression was silenced with siRNA and the expression levels of all genes were screened. Gene chip expression analyses revealed that the suppression of ATAD2 in breast cancer cells indicated a role in the regulation of microtubule organization, cell growth, cell adhesion and important signal pathways such as EGFR, FGFR, MAPK, and PI3K. Functional studies with breast cancer cells have supported the gene expression analysis results. Our study revealed that silencing of ATAD2 lead to suppression of ER(-) breast cancer cell migration but not ER(+) cancer cell migration. The same experiments causes a marked decrease in the colony formation capacity and proliferation potential of HCC1937 cells while there was no change in SKBR3 and ER(+) cells. ATAD2 silencing also lead to a senescence response in all breast cancer cells. We investigated the molecular mechanisms of action of ATAD2 to determine the factors underlying the biological effect. The MCF7 and HCC1937 cells were used to clarify its action on the main cellular signal pathways. We found that ATAD2 silencing induced an apoptosis response in both cell types. Intrinsic pathways are activated with caspase-9 cleavage in MCF7 cells while high Bcl2 and BclXL expression prevents caspase-9 cleavage in HCC1937 cells. Decreased ATAD2 did not cause a difference in the p53 protein level in either cells but while p21 expression was increased in just MCF7 cells, RB phosphorylation was inhibited in both cell lines. The results indicate that dysregulation of proteins involved in intracellular control pathways triggers the senescence mechanism. ERα gene expression has been shown to be suppressed as a result of siRNA suppression of ATAD2 gene expression in MCF7 cells. This result indicates that ATAD2 has a role in ERα regulation. ATAD2 gene expression has been found to decrease following Gefitinib suppression of EGFR signaling while EGF treatment of serum-starved MCF7 cells caused increased ATAD2 gene expression. These results indicate that EGFR could be a possible upstream activator of ATAD2. This gene expression pattern also points towards a positive feedback mechanism between ATAD2+ERα and EGFR. Although it is known that EGFR is frequently overexpressed in breast cancer and cross-talk with the estrogen receptor, we do not have detailed information on the mechanism of their interactions. ‘Pathway Enrichment’ analysis of microarray studies have revealed EGFR signaling as one of pathways enriched in the genes downregulated with decreased ATAD2 expression. The silencing of ATAD2 and ERα together prevents EGFR expression in MCF7 cells while silencing of ATAD2 by itself in HCC1937 cells does not cause a change in EGFR expression but prevents its phosphorylation in the Tyr1173 region of the receptor. The ATAD2-suppressed EGFR activity in HCC1937 cells did not lead any change in the Akt level or MEK/ERK activity. The down-stream signaling pathway analysis of the EGFR has revealed that Akt protein expression is suppressed when ATAD2 is silenced in MCF7 cells. The increase in the MEK/ERK signaling activity with decreased ERα expression in the same cells was suppressed with decreased ATAD2 expression. In conclusion, the high expression of the ATAD2 gene in breast cancer stimulates growth of cancer cells while its interaction with the EGFR signaling pathway could be one of the causes of the pro-oncogenic effects of the gene. Its suppression together with EGFR could provide an option for new therapeutic applications in breast cancer studies.
Open Access
Herpes simplex virus 1 amplicon vector-mediated siRNA targeting epidermal growth factor receptor inhibits growth of human glioma cells in vivo
(2005) Saydam O.; Glauser, D.L.; Heid I.; Turkeri G.; Hilbe, M.; Jacobs, A.H.; Ackermann, M.; Fraefel, C.
In primary glioblastomas and other tumor types, the epidermal growth factor receptor (EGFR) is frequently observed with alterations, such as amplification, structural rearrangements, or overexpression of the gene, suggesting an important role in glial tumorigenesis and progression. In this study, we investigated whether posttranscriptional gene silencing by vector-mediated RNAi to inhibit EGFR expression can reduce the growth of cultured human gli36 glioma cells. To "knock down" EGFR expression, we have created HSV-1-based amplicons that contain the RNA polymerase III-dependent H1 promoter to express double-stranded hairpin RNA directed against EGFR at two different locations (pHSVsiEGFR I and pHSVsiEGFR II). We demonstrate that both pHSVsiEGFR I and pHSVsiEGFR II mediated knock-down of transiently transfected full-length EGFR or endogenous EGFR in a dose-dependent manner. The knock-down of EGFR resulted in the growth inhibition of human glioblastoma (gli36-luc) cells both in culture and in athymic mice in vivo. Cell cycle analysis and annexin V staining revealed that siRNA-mediated suppression of EGFR induced apoptosis. Overall HSV-1 amplicons can mediate efficient and specific posttranscriptional gene silencing. Copyright © The American Society of Gene Therapy.
Open Access
In vitro analysis of the renin–angiotensin system and inflammatory gene transcripts in human bronchial epithelial cells after infection with severe acute respiratory syndrome coronavirus
(SAGE, 2020) Türk, C.; Türk, S.; Temirci, Elif Sena; Malkan, Ü. Y.; Haznedaroğlu, İ. C.
Introduction: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a recently identified coronavirus family member that triggers a respiratory disease similar to severe acute respiratory syndrome coronavirus (SARS-CoV). SARS-CoV and SARS-CoV-2 are very similar to each other in many respects, such as structure, genetics, and pathobiology. We hypothesized that coronaviruses could affect pulmonary tissues via integration with the critical immune genes after their interaction with renin–angiotensin system (RAS) elements. The aim of the present bioinformatics study was to assess expression changes of the RAS and non-RAS genes, particularly immune response genes, in the lung epithelial cells after infection with SARS-CoV. Methods: Linear regression, hierarchical clustering, pathway analysis, and network analysis were performed using the E-GEOD-17400 data set. Results: The whole-genome expression data of the lung epithelial cells infected with SARS-CoV for 12, 24, and 48 hours were analyzed, and a total of 15 RAS family and 29 immune genes were found to be highly correlated with the exposure time to the virus in the studied groups. Conclusion: RAS genes are important at the initiation of the infections caused by coronavirus family members and may have a strong relationship with the exchange of immune genes in due course following the infection.