Bisphosphonates are a class of drug that help slow down the thinning of the bone, and so they are sometimes used during the treatment of cancers to help prevent bone damage. In recent years, the exact effect that bisphosphonates can have on cancer has been questioned and an anti-tumour effect has been seen on many cancer types; including osteosarcoma.
This anti-tumour effect of bisphosphonates includes decreasing the tumour burden and preventing the tumour from spreading to other areas of the body; but the exact way in which the bisphosphonates give rise to these anti-tumour effects is unknown and which cells they are directly acting on to create these effects is uncertain.
Dr Anke Roelofs, from The University of Aberdeen, worked to determine the cell types that bisphosphonate drugs were acting on in order to better understand the effect of these drugs on tumours such as osteosarcoma. A main finding of this project was that a cell known as a macrophage can take up bisphosphonates.
What does this finding mean?
Macrophages in the tumour (also known as tumour-associated macrophages, or TAMs) can actively promote tumour growth and tumour spread, and so it was hypothesised that the bisphosphonates were acting on these TAMs and preventing their role in tumour development. Using a bisphosphonate called Zoledronic Acid, Dr Anke Roelofs found tumour-associated macrophages to be more sensitive to this drug than any other cell type present within an osteosarcoma tumour and that the number of tumour-associated macrophages decreased when the osteosarcoma was treated with this drug.Unfortunately, large amounts of Zoledronic Acid were required to see these effects, and so further testing is required to confirm these results. Studies like this continue to increase our understanding of the properties of drugs such as bisphosphonates and clarify their functioning and effects on tumours of the bone. This enables the development of better treatment strategies to maximise the anti-tumour potential of these drugs in osteosarcoma and other forms of bone cancer.