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- All Subjects: Molecular Biology
Description
Acute Myeloid Leukemia (AML) is a disease that occurs when genomic changes alter expression of key genes in myeloid blood cells. These changes cause them to resume an undifferentiated state, proliferate, and maintain growth throughout the body. AML is commonly treated with chemotherapy, but recent efforts to reduce therapy toxicity have focused on drugs that specifically target and inhibit protein products of the cancer’s aberrantly expressed genes. This method has proved difficult for some proteins because of structural challenges or mutations that confer resistance to therapy. One potential method of targeted therapy that circumvents these issues is the use of small molecules that stabilize DNA secondary structures called G-quadruplexes. G-quadruplexes are present in the promoter region of many potential oncogenes and have regulatory roles in their transcription. This study analyzes the therapeutic potential of the compound GQC-05 in AML. This compound was shown in vitro to bind and stabilize the regulatory G-quadruplex in the MYC oncogene, which is commonly misregulated in AML. Through qPCR and western blot analysis, a GQC-05 mediated downregulation of MYC mRNA and protein was observed in AML cell lines with high MYC expression. In addition, GQC-05 is able to reduce cell viability through induction of apoptosis in sensitive AML cell lines. Concurrent treatment of AML cell lines with GQC-05 and the MYC inhibitor (+)JQ1 showed an antagonistic effect, indicating potential competition in the silencing of MYC. However, GQC-05 is not able to reduce MYC expression significantly enough to induce apoptosis in less sensitive AML cell lines. This resistance may be due to the cells’ lack of dependence on other potential GQC-05 targets that may help upregulate MYC or stabilize its protein product. Three such genes identified by RNA-seq analysis of GQC-05 treated cells are NOTCH1, PIM1, and RHOU. These results indicate that the use of small molecules to target the MYC promoter G-quadruplex is a viable potential therapy for AML. They also support a novel mechanism for targeting other potentially key genetic drivers in AML and lay the groundwork for advances in treatment of other cancers driven by G-quadruplex regulated oncogenes.
ContributorsTurnidge, Megan (Author) / Lake, Douglas (Thesis advisor) / Kim, Suwon (Committee member) / Azorsa, David (Committee member) / Arizona State University (Publisher)
Created2017
Description
Inhibitor of growth factor 4 (ING4) is a tumor suppressor of which low expression has been associated with poor patient survival and aggressive tumor progression in breast cancer. ING4 is characterized as a transcription regulator of inflammatory genes. Among the ING4-regulated genes is CXCL10, a chemokine secreted by endothelial cells during normal inflammation response, which induces chemotactic migration of immune cells to the site. High expression of CXCL10 has been implicated in aggressive breast cancer, but the mechanism is not well understood. A potential signaling molecule downstream of Cxcl10 is Janus Kinase 2 (Jak2), a kinase activated in normal immune response. Deregulation of Jak2 is associated with metastasis, immune evasion, and tumor progression in breast cancer. Thus, we hypothesized that the Ing4/Cxcl10/Jak2 axis plays a key role in breast cancer progression. We first investigated whether Cxcl10 affected breast cancer cell migration. We also investigated whether Cxcl10-mediated migration is dependent on ING4 expression levels. We utilized genetically engineered MDAmb231 breast cancer cells with a CRISPR/Cas9 ING4-knockout construct or a viral ING4 overexpression construct. We performed Western blot analysis to confirm Ing4 expression. Cell migration was assessed using Boyden Chamber assay with or without exogenous Cxcl10 treatment. The results showed that in the presence of Cxcl10, ING4-deficient cells had a two-fold increase in migration as compared to the vector controls, suggesting Ing4 inhibits Cxcl10-induced migration. These findings support our hypothesis that ING4-deficient tumor cells have increased migration when Cxcl10 signaling is present in breast cancer. These results implicate Ing4 is a key regulator of a chemokine-induced tumor migration. Our future plan includes evaluation of Jak2 as an intermediate signaling molecule in Cxcl10/Ing4 pathway. Therapeutic implications of these findings are targeting Cxcl10 and/or Jak2 may be effective in treating ING4-deficient aggressive breast cancer.
ContributorsArnold, Emily (Author) / Kim, Suwon (Thesis director) / Blattman, Joseph (Thesis director) / Mason, Hugh (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05