Cancer cells not only use the human blood vessels as a source of nutrients, but they can also form their own blood channels through a form of mimicry. Researchers are now trying to develop and test medications that can stop tumours from copying and manipulating the human blood vessels.
Cancer researchers have been studying the ways tumours grow and recruit blood supply and nutrients. Cancer cells use human blood vessels by inducing the endothelial cells of normal blood vessels to form new lines to the tumour, a process known as angiogenesis. Alternatively, a different mechanism, where the tumour cells create their own blood delivering tubes that connect to human blood vessels, called vasculogenic mimicry, has been purported.
As reported by Science in March 2000, a group of scientists met to debate the differences between these two means of tumour growth. Angiogenesis means that the tumours can faster obtain the nutrients and oxygen needed for increased replication and growth. This is widely accepted as one of the hallmarks of cancer. The development of angiogenesis blocking drugs has shown clinically that this might not always be the case. Drugs on the market include Acastin and Nexavar, and these have only been shown to slow the tumour growth, until it eventually becomes resistant to the drugs.
Vasculogenic mimicry provides an alternate explanation to why angiogenesis inhibitors have failed to live up to their potential at delaying tumour growth. Researchers at the University of Iowa planted melanoma cells on a gel surface that replicated the human extracellular matrix, the material that surround human cells. What they observed was that the aggressive tumour cells migrated through the matrix surface and scrunched it up, in accordance to the vasculogenic mimicry hypothesis. A recent Chinese meta-analysis showed this occurred in a number of other types of cancer, and correlated it with an overall poorer prognosis.
Furthermore, vasculogenic mimicry could promote metastasis, or the spread of the cancer cells throughout the body. A team of Cambridge scientists tracked various cells that turned into metastasis, and found that they had amplified genes that inhibited blood clotting, and increased vasculogenic mimicry. Currently, pharmaceutical companies like TaiRx are working to develop drugs that would block this, and potentially block cancer growth. This would be an exciting step in the fight against cancer.
Written By: Sarah Kassenaar, BSc (Hons)