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Title: Regulation of human CXCL12 expression by IKKα in bone cancer and cancer associated fibroblasts derived from clinical specimens obtained from breast cancer patients
Author: Khalaf, Yousif Hendi
ISNI:       0000 0004 7967 252X
Awarding Body: University of Strathclyde
Current Institution: University of Strathclyde
Date of Award: 2018
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Despite great progress in surgery, radio- and chemotherapy, the prognosis and treatment options for osteosarcoma and breast cancer remain extremely poor with a high inclination for metastatic spread to other organs. Compelling evidence has demonstrated that CXCL12/CXCR4 is implicated in human tumour pathogenesis. Therefore, targeting CXCL12 expression is a logical strategy for treating cancer patients. Moreover, studies have implicated inhibitory Kappa B kinase alpha (IKKα) as a key regulator in the non-canonical NF-κB pathway and it has recently been demonstrated that IKKα can regulate CXCL12 expression. Therefore, the aim of the current study was to investigate the role of the IKKα-mediated non-canonical NF-κB pathway in the regulation of CXCL12 expression in a human bone osteosarcoma cell line (U2OS) and cancer-associated fibroblasts (CAFs) derived from clinical specimens obtained from human breast cancer patients to determine the validity of this approach. Initially, newly synthesised selective IKKα inhibitors (SU compounds) were characterised in LTα₁β₂-stimulated U2OS cells and were shown to be moderately potent and selective for the non-canonical NF-κB pathway, whereas they exerted little effect on the classical NF-κB pathway at high micromolar concentrations. In addition, it was unexpectedly found that both TNFα and IL-1β were strong and early activators of the non-canonical NF-κB pathway activated by IKKα, which was established using both siRNA and the selective inhibitors. Both TNFα and IL-1β but not LTα₁β₂, stimulated a strong increase in CXCL12 in reporter U2OS cells and when endogenously measured using RT-qPCR. CXCL12 expression was susceptible to both siRNA knock down and IKKα inhibitors, suggesting that the early strong IKKα signal was significant for expression. We further examined the role of IKKα in CXCL12 expression in CAFs derived from breast cancer patients. ELISA data revealed that CXCL12 protein secretion in CAFs was significantly higher than that of normal fibroblasts (NFs). However, our findings did not demonstrate a significant difference in the activation of the non-canonical NF-κB pathway by LTα₁β₂. Moreover, the studies conducted using siRNA IKKα and SU compounds showed that CXCL12 expression was not altered in CAFs or NFs. Overall, these findings indicate that IKKα is not required for the regulation of CXCL12 expression in CAFs. Taken together, these results highlight a novel early kinetically distinct mode of non-canonical NF-κB signalling by IKKα, which is significant in the induction of CXCL12 in bone cells. Therefore, selective IKKα inhibition may be a target for cancer therapy but only for certain types of cancer and is not always linked to CXCL12 inhibition.
Supervisor: Plevin, Robin ; Paul, Andy Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral