PhD ThesisBackground: TNF-related apoptosis-inducing ligand (TRAIL) can induce cell death in
cancer cells after binding to its TRAIL receptors [TRAILR, Death Receptor 4 (DR4) and
Death Receptor 5 (DR5)] while sparing non-malignant cells. The application of TRAIL
provides an approach that can potentially overcome drug resistance and toxicity
associated with high doses of conventional therapies. It could be administered alone or
in combination with conventional therapies and, therefore, may offer a promising new
approach to bone sarcoma treatment. Enhancing the cytotoxic effect of TRAIL involves
targeting a tumour associated antigen (TAA). Here, the aim was to characterise bone
sarcoma cells for TRAILR expression and to assess the effectiveness, both in vitro and
in vivo of a novel TRAIL construct, neural/glial antigen 2 (NG2) targeted TRAIL
(ScFvNG2-Fc-scTRAIL).
Methods: Bone sarcoma cell lines were characterised for TRAILR and NG2 expression
on RNA and protein level. Together with non-malignant cell lines, they were exposed
to the novel TRAIL therapeutic (ScFvNG2-Fc-scTRAIL) in vitro and then tested in vivo in
a newly developed xenograft model of dedifferentiated chondrosarcoma.
Results: Surface DR5 was expressed in all cell lines examined (very high: HT1080,
MG63; moderate: SW153, U2OS, TC71). NG2 was also expressed (very high: SW1353,
MG63; moderate: U2OS, HT1080). ScFvNG2-Fc-scTRAIL demonstrated enhanced
cytotoxicity in DR5- and NG2-expressing cell lines (MG63>HT1080>U2OS), which
increased with doxorubicin and was also found in vivo when engrafting a luciferase
expressing HT1080 cell line in a dedifferentiated chondrosarcoma mouse model.
Conclusion: I demonstrate that a novel targeted TRAIL therapeutic, ScFvNG2-FcscTRAIL, has a selective and significant cytotoxic effect on cell lines expressing both cell
surface DR5 and NG2, and these cytotoxic effects can be enhanced further with
doxorubicin. Such combinations could minimise the risk of treatment failure due to
drug resistance, a common problem of single agent approaches. Furthermore, these
findings provide a framework for the clinical development of ScFvNG2-Fc-scTRAIL and
could potentially be used in the neoadjuvant setting, which would be a shift from the
usual convention of prioritising excision of the sarcoma