Work Package 1: Understanding the divergent relationship between tumour elimination and bone regeneration in Osteosarcoma
Recently, there has being increasing interest in the use of 3D cultures to study the interactions between tumour cells and other cellular or acellular components of the tumour microenvironment as the results better correlate with results seen in vivo. Therefore, we developed a 3D spheroid model of early and late-stage osteosarcoma, consisting of a direct co-culture of both osteosarcoma cells and MSCs. As MSCs are an integral player in osteosarcoma progression, but also are well known to play an important role in bone regeneration, it was vital that these were included in the model. We validated the clinical relevancy of the model using FDA-approved chemotherapeutic Doxorubicin. Following validation with Doxorubicin, we were able to use this model to further understand the paradoxical relationship between tumour elimination and bone regeneration. Specifically, our model validated that osteogenic supplements have stimulatory effect on the stromal cells, but minimal effect of cancer cell growth. However, when these osteogenic supplements are delivered along with chemotherapeutics this stimulatory effect is completely abolished. Taken together, we have developed and validated a model that mimics the vital relationship between stromal and osteosarcoma cells as well as models their response to chemotherapeutics and regenerative cues, providing vital information that can inform the design of future therapies for these young patients. This work culminated in a paper in Advanced Healthcare Materials in 2021.
Work package 2: Investigate the tumour promotive/regenerative potential of BMP-2 delivery in an immunocompetent orthotopic model for osteosarcoma.
The results generated from WP1 clearly demonstrate that there is a fine balance with regenerating the damaged tissue without causing tumour recurrence. With this in mind, I first established an orthotopic model for osteosarcoma which metastasises to the lung. Next, we conducted our in vivo study to understand the effect BMP-2 delivery alone or in combination with Doxorubicin would have on tumour progression and bone formation. The results from this study show that BMP-2 delivery did not accelerate tumour progression in a pre-clinical osteosarcoma orthotopic model, when compared to non-treated or doxorubicin alone groups. Interestingly, when treated locally with a hydrogel containing BMP-2 alone ectopic bone formation was observed surrounding the tibia However, when treated with the same hydrogel and concentration of BMP-2 in combination with systemic chemotherapeutics this stimulatory effect was significantly diminished (see Figure 1). Taken together, these results indicate that although BMP-2 delivery does not exert any tumour-promoting effects as previously feared, it is not an effective therapy to aid with the regeneration, while the patient is undergoing chemotherapy.
Work Package 3: Investigate if localised delivery of miR-29b would suppress osteosarcoma tumours whilst simultaneously normalising the dysregulation of bone homeostasis caused by osteosarcoma.
We developed a formulation of miR-29b:nanoparticles that were delivered via a novel hyaluronic-based hydrogel to enable local and sustained release of the therapy, and to study the potential of attenuating tumour growth whilst normalising bone homeostasis. We found that when miR-29b alone, compared to chemotherapy alone, our therapy provided a significant decrease in tumour burden, increase in mouse survival, and a significant decrease in osteolysis thereby normalising the dysregulation of bone lysis activity caused by the tumour (Figure 2). This work is currently under review in Advanced Materials.
All of this work was presented at 5 international conferences (3 poster presentations 2 podium presentations). There will also be 3 journal publications in leading journals including Advanced Healthcare Materials and Trends in Molecular Medicine.
