Preclinical testing of TRAIL therapeutics for sarcoma

Zakareya Gamie, Anja Krippner-Heidenreich, Craig Gerrand, Kenneth Rankin
Newcastle University, Northern Institute for Cancer Research, Newcastle upon Tyne, United Kingdom

Background
Despite intensive, multimodal therapy, patients with bone sarcomas have poor 5-year survival, close to 50%. TNF-related apoptosis-inducing ligand (TRAIL) can induce apoptosis in cancer cells, via the extrinsic pathway, after binding to its death receptors: DR4 and DR5, while sparing non-transformed cells. TRAIL provides an approach that can overcome current therapeutic limitations, such as drug resistance and toxicity associated with high doses, when administered alone or combined with conventional therapies. 

Objectives
To characterise sarcoma cells for Death Receptor (DR) expression and factors that render them susceptible to TRAIL therapy, and to assess the effectiveness of different forms of TRAIL. 

Study Design & Methods
We characterized osteosarcoma cell lines (U2OS, SAOS-2 and SJSA-1), Ewing’s sarcoma cell line (TC-71), bone fibrosarcoma cell line (HT1080), chondrosarcoma cell line (SW1353), for Death Receptor 4 (DR4) and Death Receptor 5 (DR5) expression at the RNA and protein levels. Sarcoma and normal human cell lines were exposed to different forms of TRAIL. 

Results
DR5 was found to be upregulated in sarcoma cell lines. Crosslinked forms of TRAIL were more cytotoxic when compared to non-crosslinked forms of TRAIL. Fibroblasts and stem cells were resistant to TRAIL therapy; however, human hepatocytes cells were sensitive. SuperKillerTRAIL (SKT) and a newly designed scFv:TRAIL variant targetting NG2, also upregulated in HT1080, U2OS and SW1353 cell lines, demonstrated significantly enhanced cell killing (figure), particularly when combined with doxorubicin. 

Conclusions
Our pilot in vitro data indicate that osteosarcoma cell lines such as U2OS can be killed by pre-oligomerised versions of TRAIL and more resistant cell lines such as SJSA-1 and SW1353 can be sensitised to TRAIL by current chemotherapeutics. Furthermore, resistant cell lines such as SW1353 can also be sensitised by Birinapant, which is an improvement on previous smac mimetics. We plan to test the therapeutics in vivo in an orthotopic mouse model of bone sarcoma.