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Title: The role of induciable transcription factors and microenvironment in leukemia
Author: Qattan, Malak
ISNI:       0000 0004 2649 327X
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2014
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Although the survival rates of 80% in acute lymphocytic leukemia (ALL) is a remarkable achievement, the 20% of affected children are facing the risk of death and toxicity of the treatment is significant. The drugs used in ALL are anthracyclines and steroids. Glucocorticoids exert their therapeutic effects in leukemia by inducing apoptosis through intracellular glucocorticoid receptor (GR). Anthracyclines have the ability to inhibit the DNA topoisomerase II causing DNA double strands breaks and the end result is activation of p53 protein. The exact mechanisms of action of those drugs are not well understood, and significant proportion of children develops drug resistance. Moreover, it has recently been described that microenvironment can also contribute to leukemia cell survival and protect leukemia cells from the cytotoxic effect of drugs. Increased understanding of the mechanisms that lead to 80% curable rate will help bring curable rate to this level in other cancer types as well. The aim of this study was to better understand of the role played by GR in improving the treatment and the role of bone marrow environment in inducing resistance. We have used ALL cell lines that are sensitive (CEM-C7-14) and resistant (CEM-C1-15) to glucocorticoid induced apoptosis and treated them with anthracyclines (etoposide-Etop) and glucocorticoids (dexamethasone-Dex) in the absence and presence of conditioned media (CM) obtained from bone marrow cells thus mimicking clinical settings. Our results demonstrate Bim down-regulation and Bax up-regulation highlighting the possibility of alternative pathways being utilized for apoptosis when both drugs are used. Also, analysis of the post translatonal modifications of GR indicated that a complex crosstalk may be involved, and the GR phosphorylation status differs when cells were treated with either Dex or ETOP alone or in combination. Additionally, CM has significant effects on GR phosphorylation profile in both cell lines. Furthermore, our preliminary data indicates that dexamethasone induces autophagy as well as apoptosis in leukemia cells. The activation of autophagy appears to be through beclin which is activated by glucocorticoids and activation of beclin is considered as a reason for efficient killing of the leukemic cells by dexamethasone. That may highlight beclin as a new target of glucocorticoids and open new therapeutic possibilities. To have wider view, microarray technique was adapted. The interesting preliminary data revealed the repressive effect of CM on particular genes linked to cell death or survival including NFKBIB (an inhibitor of NK-κB), RUNX3, Bad and RIP-1.Repressive effect of bone marrow microenvironment on those genes leads to cell survival, which is one way for the bone marrow microenvironment to develop resistance. RIP-1 is significantly repressed in cells grown in CM media and it has been linked to not only apoptosis, but also with other forms of cells death including autophagy and necroptosis In addition RIP-1 is also involved in the regulation of MAPK and NF-κB, which are pathways that play an important role in regulating GR. Therefore, we initiated analysis and validation of RIP-1 to evaluate RIP-1 as a key switch between apoptosis and autophagy, and their significance with respect to cancer development and treatment. The data showed that inhibition of RIP-1 resulted in increased autophagy and not apoptosis. On the other hand, Dex treatment alone or combined tends to exert apoptotic stress on the cells rather than autophagy. In conclusion, our findings can increase the understands of the biological and molecular aspects of the differences between the sensitive and resistant cells in acute lymphoblastic leukemia and the effect of the stem cell niche on the therapy which can contribute to more efficient, less toxic therapy.
Supervisor: Jackson, Dean; Krstic-Demonacos, Marija Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available