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Human cytomegalovirus inhibits apoptosis by regulating the activating transcription factor 5 signaling pathway in human malignant glioma cells.

Wang T, Qian D, Hu M, Li L, Zhang L, Chen H, Yang R, Wang B - Oncol Lett (2014)

Bottom Line: Furthermore, in glioblastoma U87 cells, HCMV infection induced cellular proliferation in parallel with an increase in the expression level of ATF5 and B-cell lymphoma/leukemia-2 to Bcl-2-associated X protein ratio.Loss of ATF5 function was achieved using a dominant-negative form of ATF5 in U87 cells, whereby cells appeared to grow marginally following HCMV infection when compared with the control.These results indicate that ATF5 signaling pathways may be important in the anti-apoptotic activity of HCMV-infected glioblastoma cells; therefore, the anti-apoptotic molecular mechanisms of HCMV in human glioblastoma cells were investigated in the current study.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Qingdao University Medical College, Qingdao, Shandong 266071, P.R. China.

ABSTRACT
The activating transcription factor 5 (ATF5), also termed ATFx, is a member of the ATF/cAMP response element-binding protein (CREB) family of basic zipper proteins. ATF5 is an anti-apoptotic protein that is highly expressed in malignant glioma and is essential for glioma cell survival. Accumulating evidence indicates that human malignant gliomas are universally infected with human cytomegalovirus (HCMV). Recent studies have shown that HCMV may be resistant to the induction of apoptosis by disrupting cellular pathways in glioblastoma. To investigate the potential anti-apoptotic function of HCMV in glioma, malignant U87 glioma cells were infected with HCMV. The present study showed that HCMV infection suppressed apoptosis in glioblastoma U87 cells by regulating the expression of ATF5. Furthermore, in glioblastoma U87 cells, HCMV infection induced cellular proliferation in parallel with an increase in the expression level of ATF5 and B-cell lymphoma/leukemia-2 to Bcl-2-associated X protein ratio. Loss of ATF5 function was achieved using a dominant-negative form of ATF5 in U87 cells, whereby cells appeared to grow marginally following HCMV infection when compared with the control. However, the anti-apoptotic ability was appeared to decline in the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay. These results indicate that ATF5 signaling pathways may be important in the anti-apoptotic activity of HCMV-infected glioblastoma cells; therefore, the anti-apoptotic molecular mechanisms of HCMV in human glioblastoma cells were investigated in the current study. Prevention of HCMV infection may present a potential and promising approach for the treatment of malignant gliomas.

No MeSH data available.


Related in: MedlinePlus

Cell viability analysis of siATF5 or dnATF5 U87 cells following HCMV infection. (A) U87 cells expressing non-targeting siRNA or ATF5 short hairpin RNA were infected with HCMV for 0, 12, 24 or 48 h. Knocking down ATF5 expression reduced tumor cell proliferation. HCMV-infected siATF5 U87 marginally promoted proliferation. (B) U87 cells were produced with loss of ATF5 function using a dn form. The results were consistent with siATF5 U87 cells. Cell proliferation was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Data are presented as the mean ± standard deviation of three independent experiments (*P<0.05 vs. con + HCMV). si, small interfering; dn, dominant-negative; ATF5, activating transcription factor 5; HCMV, human cytomegalovirus; con, control.
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f2-ol-08-03-1051: Cell viability analysis of siATF5 or dnATF5 U87 cells following HCMV infection. (A) U87 cells expressing non-targeting siRNA or ATF5 short hairpin RNA were infected with HCMV for 0, 12, 24 or 48 h. Knocking down ATF5 expression reduced tumor cell proliferation. HCMV-infected siATF5 U87 marginally promoted proliferation. (B) U87 cells were produced with loss of ATF5 function using a dn form. The results were consistent with siATF5 U87 cells. Cell proliferation was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Data are presented as the mean ± standard deviation of three independent experiments (*P<0.05 vs. con + HCMV). si, small interfering; dn, dominant-negative; ATF5, activating transcription factor 5; HCMV, human cytomegalovirus; con, control.

Mentions: To investigate the function of ATF5 in HCMV-infected U87 cells, the effect of silencing ATF5 on the proliferation of HMCV-infected U87 cells was examined. U87 cells were infected with lentiviral RNAi to interfere with ATF5. Western blot analysis revealed that ATF5 protein levels were markedly decreased (data not shown). The cells were subsequently infected with HCMV at various time points and cell proliferation was determined by MTT assay. As shown in Fig. 2A, compared with U87 cells, cell proliferation was reduced following ATF5 interference in U87 cells (P<0.05; between12 and 48 h). Cell viability following ATF5 interference in U87 cells was marginally increased following HCMV infection when compared with siATF5 U87 cells. To further validate this observation, U87 cells were transfected with dnATF5 plasmids to interfere with ATF5. As shown in Fig. 2B, the results were consistent with Fig. 2A. These results indicated that ATF5 may be involved in the regulation of cell proliferation of HCMV-infected U87 cells in vitro.


Human cytomegalovirus inhibits apoptosis by regulating the activating transcription factor 5 signaling pathway in human malignant glioma cells.

Wang T, Qian D, Hu M, Li L, Zhang L, Chen H, Yang R, Wang B - Oncol Lett (2014)

Cell viability analysis of siATF5 or dnATF5 U87 cells following HCMV infection. (A) U87 cells expressing non-targeting siRNA or ATF5 short hairpin RNA were infected with HCMV for 0, 12, 24 or 48 h. Knocking down ATF5 expression reduced tumor cell proliferation. HCMV-infected siATF5 U87 marginally promoted proliferation. (B) U87 cells were produced with loss of ATF5 function using a dn form. The results were consistent with siATF5 U87 cells. Cell proliferation was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Data are presented as the mean ± standard deviation of three independent experiments (*P<0.05 vs. con + HCMV). si, small interfering; dn, dominant-negative; ATF5, activating transcription factor 5; HCMV, human cytomegalovirus; con, control.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4114579&req=5

f2-ol-08-03-1051: Cell viability analysis of siATF5 or dnATF5 U87 cells following HCMV infection. (A) U87 cells expressing non-targeting siRNA or ATF5 short hairpin RNA were infected with HCMV for 0, 12, 24 or 48 h. Knocking down ATF5 expression reduced tumor cell proliferation. HCMV-infected siATF5 U87 marginally promoted proliferation. (B) U87 cells were produced with loss of ATF5 function using a dn form. The results were consistent with siATF5 U87 cells. Cell proliferation was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Data are presented as the mean ± standard deviation of three independent experiments (*P<0.05 vs. con + HCMV). si, small interfering; dn, dominant-negative; ATF5, activating transcription factor 5; HCMV, human cytomegalovirus; con, control.
Mentions: To investigate the function of ATF5 in HCMV-infected U87 cells, the effect of silencing ATF5 on the proliferation of HMCV-infected U87 cells was examined. U87 cells were infected with lentiviral RNAi to interfere with ATF5. Western blot analysis revealed that ATF5 protein levels were markedly decreased (data not shown). The cells were subsequently infected with HCMV at various time points and cell proliferation was determined by MTT assay. As shown in Fig. 2A, compared with U87 cells, cell proliferation was reduced following ATF5 interference in U87 cells (P<0.05; between12 and 48 h). Cell viability following ATF5 interference in U87 cells was marginally increased following HCMV infection when compared with siATF5 U87 cells. To further validate this observation, U87 cells were transfected with dnATF5 plasmids to interfere with ATF5. As shown in Fig. 2B, the results were consistent with Fig. 2A. These results indicated that ATF5 may be involved in the regulation of cell proliferation of HCMV-infected U87 cells in vitro.

Bottom Line: Furthermore, in glioblastoma U87 cells, HCMV infection induced cellular proliferation in parallel with an increase in the expression level of ATF5 and B-cell lymphoma/leukemia-2 to Bcl-2-associated X protein ratio.Loss of ATF5 function was achieved using a dominant-negative form of ATF5 in U87 cells, whereby cells appeared to grow marginally following HCMV infection when compared with the control.These results indicate that ATF5 signaling pathways may be important in the anti-apoptotic activity of HCMV-infected glioblastoma cells; therefore, the anti-apoptotic molecular mechanisms of HCMV in human glioblastoma cells were investigated in the current study.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Qingdao University Medical College, Qingdao, Shandong 266071, P.R. China.

ABSTRACT
The activating transcription factor 5 (ATF5), also termed ATFx, is a member of the ATF/cAMP response element-binding protein (CREB) family of basic zipper proteins. ATF5 is an anti-apoptotic protein that is highly expressed in malignant glioma and is essential for glioma cell survival. Accumulating evidence indicates that human malignant gliomas are universally infected with human cytomegalovirus (HCMV). Recent studies have shown that HCMV may be resistant to the induction of apoptosis by disrupting cellular pathways in glioblastoma. To investigate the potential anti-apoptotic function of HCMV in glioma, malignant U87 glioma cells were infected with HCMV. The present study showed that HCMV infection suppressed apoptosis in glioblastoma U87 cells by regulating the expression of ATF5. Furthermore, in glioblastoma U87 cells, HCMV infection induced cellular proliferation in parallel with an increase in the expression level of ATF5 and B-cell lymphoma/leukemia-2 to Bcl-2-associated X protein ratio. Loss of ATF5 function was achieved using a dominant-negative form of ATF5 in U87 cells, whereby cells appeared to grow marginally following HCMV infection when compared with the control. However, the anti-apoptotic ability was appeared to decline in the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay. These results indicate that ATF5 signaling pathways may be important in the anti-apoptotic activity of HCMV-infected glioblastoma cells; therefore, the anti-apoptotic molecular mechanisms of HCMV in human glioblastoma cells were investigated in the current study. Prevention of HCMV infection may present a potential and promising approach for the treatment of malignant gliomas.

No MeSH data available.


Related in: MedlinePlus