Sabrina E. Brzostek

6th Year Graduate Student

Department: Microbiology

Graduate Program: Molecular & Cellular Biology

Advisor: Dr. Nancy Reich

Abstract:

Title:  Effect of Etoposide on Interferon Signaling 

Etoposide, a chemotherapeutic drug used to treat various cancers, causes cell cycle arrest and death by apoptosis. Its mechanism of action involves the targeting of topoisomerase II, resulting in an increase the number of double stranded breaks in the DNA. Ultimately, this damage triggers cell death pathways, leading to apoptosis.

Our studies suggest that etoposide may induce a cellular response reminiscent to that of a virally infected cell. One known family of genes induced in response to viral infection encodes the interferon (IFN) cytokines. IFNs are secreted from infected cells and bind to specific cell surfaces receptors, stimulating a signaling pathway that induces the IFN stimulated genes (ISGs). mRNA expression measured by DNA microarray assays indicate that IFN-induced genes are induced following treatment with etoposide. Real time PCR studies show that etoposide treated cells have an increase in interferon α (IFNα) and interferon λ (IFNλ) mRNA.

The induction of interferon genes is dependent on transcription factors, such as the Interferon Regulatory Factors (IRFs) and NFκB. Using fluorescence microscopy studies to detect the activation of IRF3, IRF5 and IRF7, I show that these IRF family members remain latent in the cytoplasm in etoposide treated cells. This indicates that the IRFs may not play a crucial role in IFN gene induction, in response to etoposide treatment.

Another family of transcription factors, NFκB, play an important role in IFN induction in response to viral infection. I show that NFκB is activated in etoposide treated cells and I am continuing studies to determine whether this transcription factor is a key player in the induction of the interferon genes in etoposide treated cells.

Publications:
(MSTP-supported publications indicated with an *)

*Cheng TF, *Brzostek S, Ando O, Van Scoy S, Kumar KP, Reich NC. Differential Activation of IFN Regulatory Factor (IRF)-3 and IRF-5 Transcription. J Immunol . 176:7462-7470.

Makowski A, Brzostek S, Cohen RN, Hollenberg AN. Determination of nuclear receptor corepressor interactions with the thyroid hormone receptor. Mol Endocrinol. 17(2):273-86.

Cheng S, Brzostek S, Lee SR, Hollenberg AN, Balk SP. Inhibition of the dihydrotestosterone-activated androgen receptor by nuclear receptor corepressor. Mol Endocrinol. 16(7):1492-501.

Cohen RN, Brzostek S, Kim B, Chorev M, Wondisford FE, Hollenberg AN. The specificity of interactions between nuclear hormone receptors and corepressors is mediated by distinct amino acid sequences within the interacting domains. Mol Endocrinol. 15(7):1049-61