Posted November 10, 2015 by admin in Health Technology and Medicine | 480 Total Views
BRD4 INHIBITOR EFFECT ON OVARIAN CANCER CELLS
Multiple genetic and epigenetic events contribute to epithelial carcinogenesis. Many components involved in epigenetic regulation of gene expression, DNA repair and replication generally encounter mutations in various cancers. Chromatin structure organization is crucial for regulating many fundamental cellular processes. Currently it is known that there are four epigenetic factors that regulate DNA modification and 16 epigenetic factors that regulate histone modifications. Many proteins that control and interpret this modification play a role in oncogenesis such as proteins Bromodomain. Protein Bromodomain classified as BET protein because it has Bromodomain and Extraterminal domain.
Brd4 (bromodomain-containing protein 4) protein participates in the maintenance of the higher-order chromatin structure and binds toacetylated histones. These proteins are often known as “chromatin reader” . Until now there has been a few research on the potential role in the pathogenesis of ovarian cancer BRD4. My evaluation of TCGA database using the cBioportal showed that, BRD4 ist amplified in ~15 % of serous ovarian cancer samples and overexpressed in 45% of late stage serous ovarian cancer samples. Ovarian cancer patient with any alteration of BRD4 gene have lower survival rate than patient without any BRD4 alteration. I found that BRD4 protein is overexpressed in clinical papillary serous ovarian cancer samples as well as in a panel of ovarian cancer cell lines. BRD4 short isoforms are overexpressed in most of ovarian cancer cell lines. Furthermore, BRD4 knockdown in ovarian cancer cell line A2780 and OVCAR5 lead to decreased viability (25-60%) ovarian cancer cells. Knockdown BRD4 also cause a decrease in the expression and phosphorylation of NFκB and c-myc in A2780 and OVCAR5 (unpublished personal data).
This shows that BRD4 appears to play a role in mediating inflammation and cancer development because the two main molecules in the process of cancer development (c-myc), and NFκB expression influenced by BRD4. The aim of this research is to observe the effect of BRD4 inhibitor, I-BET-151, on cell proliferation, cell death and NFκB and c-myc expression in an ovarian cancer cell line, SKOV3.
SKOV3 cells were cultured and treated with IBET-151 for 72 hours. As a positive control, SKOV3 was incubated with Doxorubicin 1 mg/mL for 72 hours. Effect of IBET-151 on cell proliferation was observed using MTT assay, whereas its effect on cell apoptosis was assayed by ELISA quantification of histonecomplexed DNA fragments. Effect of IBET-151 on the expression of c-myc and NFκB was detected using Western Blot analysis.
It was shown that IBET-151 reduce cell proliferation of SKOV3. IC50 of IBET-151 on SKOV3 is 880 nM. This IBET-151 effect on proliferation is coincident with its activity to induce apoptosis of the SKOV3 cells. This result was also supported by c-myc downregulation, which is strongly correlates with cell proliferation and furthermore sensitize cells to apoptosis. IBET-151 with a high concentration (higher than 1400 nM) could downregulate NFκB expression. It showed that IBET-151 with the concentration below 1400 nM did not have any effect on the expression of NFκB. Probably the effect of BRD4 inhibitor is more in the phosphorylation activity of NFκB. This result showed that downstream pathway of BRD4 is especially downstream that activate c-myc expression. According to this result, it showed that BRD4 inhibitor performed a different mechanism in reducing cancer cell number in compare to doxorubicin. In conclusion, BRD4 inhibitor decreased ovarian cancer cell proliferation through signaling pathways which regulate cmyc
expression and function.
LIST OF RESEARCH OUTPUT
Presentation about “BRD4 Overexpression in Ovarian Cancer” in BIBMC, on September 2014.
HEAD OF RESEARCH TEAM r.rer.nat. Marselina Irasonia Tan
TEAM MEMBERS : Dr. Indra Wibowo
OFFICIAL ADDRESS : School of Life Sciences and Technology, Institut Teknologi Bandung,
Jl. Ganesa 10. Bandung 40132
EMAIL : marsel[at]sith.itb.ac.id