Chemokines are a family of low-molecular weight proteins that mediate their effects through binding with chemokine receptors (a group of seven trans-membrane spanning G-protein coupled receptors). Chemokines are well known for their role in leukocyte trafficking, although they also mediate a range of other physiological functions including cell proliferation, growth and differentiation. Chemokines are integral to the development and functioning of the immune system and are implicated in the pathogenesis of a wide range of diseases including autoimmune disorders, HIV infection and malignancies. Non-Hodgkin’s lymphoma (NHL) is a malignancy of the lymphoid system, which can affect any tissues in the body but has a predilection for the secondary lymphoid organs and the bone marrow. NHL represents a heterogeneous group of disorders with variations in presentation and prognosis. Whilst there have been improvements in overall survival in the last few decades following developments in treatment there is still a significant mortality associated with NHL as well as significant morbidity associated with the treatments required to control the disease or affect a cure. There is increasing evidence that chemokines and their receptors play a role in the pathogenesis of NHL with increased chemokine receptor expression seen in certain subtypes. Chemokines have also been shown to influence prognosis in particular NHL subtypes. This thesis describes studies to examine the relationship between constitutive chemokine receptor expression and NHL subtype with subsequent correlation between chemokine receptor expression and outcome. Results from studies on clinical samples obtained from patients with a range of B-cell NHL subtypes revealed significant differences in chemokine receptor expression between subtypes. Predominantly these differences were noted with the receptors CCR4 and CCR7. CCR4 has previously been examined in relation to T-cell lymphomas and high CCR4 expression has been associated with an adverse prognosis in adult T-cell leukaemia/lymphoma. However, systematic examination of CCR4 in B-cell NHL has not been done before. In this study CCR4 expression was seen in samples of diffuse large B-cell lymphoma (DLBCL), mantle cell lymphoma (MCL), MALT lymphoma and Burkitt’s lymphoma. Furthermore high CCR4 expression was associated with a significantly improved survival in patients with DLBCL. CCR7 expression was significantly higher in cases of MCL and chronic lymphocytic lymphoma/small lymphocytic lymphoma (CLL/SLL), this however did not equate to differences in outcome. The high expression of CCR7 in MCL and CLL/SLL does however make this receptor an ideal target for the development of targeted therapies. Further studies in this thesis describe strategies used to target the chemokine system with cytotoxic agents. CCR7 was chosen for targeting experiments due to its restricted expression (naïve T-cells, memory T-cells, dendritic cells and subsets of B-cells) in normal tissues, the fact that it controls homing of leukocytes to lymph nodes, and that is the second most commonly reported chemokine receptor detected in cancers. The first approach for targeting the chemokine system used radio-labelled chemokines to induce cytotoxicity in cells expressing the cognate receptor. Unfortunately, the results from this were not conclusive and further studies are required to explore this approach. The second approach described in this thesis entailed the potential use of oncolytic adenoviral gene therapy. This approach requires the redirection of adenoviral tropism from the coxsackie and adenovirus receptor (CAR) and through CCR7. This was successfully achieved in cell lines engineered to express and those endogenously expressing CCR7 by ‘shrouding’ the virus in CCL19. However, background infection was high and this led to the engineering of an adenoviral vector incorporating a peptide within the viral knob protein to allow for more efficient ‘shrouding’ of the virus and thus more efficient redirection of the virus. However, final experiments with this vector were not performed due to time constraints. The final part of this thesis relates to the characterisation of EL4 cells (a murine T-cell lymphoma cell line) for use as a potential in-vivo mouse model for targeting experiments. Following injection into the flank of C57/BL6 with these cells, measurable tumours develop. It was demonstrated that this cell line expressed CCR7, and finally after a number of modifications, it was shown that adenoviral tropism could be redirected through chemokine receptors on the surface of these cells. In summary the results in this thesis shows for the first time that CCR4 is expressed across a number of B-cell NHL subtypes and that this is associated with outcome in DLBCL. Results also demonstrate that therapeutic targeting of CCR7 is a reasonable therapeutic approach in NHL. In addition, redirection of oncolytic adenoviral vectors through chemokine receptors provides a potential strategy for obtaining this targeted therapy. Finally, EL4 cells have the potential to be used as an in-vivo mouse model for CCR7 targeted therapies.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:535289 |
| Date | January 2011 |
| Creators | Bryson, Michelle |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/2675/ |
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