Cancer: Tumour Angiogenesis

The rate of tumour growth is altered by cell kinetics and tumour angiogenesis. Tumours need blood supply to enlarge, as oxygen can only diffuse a certain distance from existing blood vessels. Thus, tumours relying on oxygen diffusion soon develop hypoxia and apoptosis occur due to activation of p53 (tumour suppressor gene).

The reason why angiogenesis is important for tumour growth is diverse, including: 1) angiogenesis means: a) supply of O2 and nutrients, b) new endothelial cells induce adjacent tumour cells to grow by secreting growth factors: PDGF, GM-CSF, IL-1. 2) Angiogenesis is prerequisite for metastasis ===> hence one way of determine prognosis and malignancy is tumour angiogenesis.

How does tumour angiogenesis occur? Tumour associated angiogenic factors may be produced by tumour cells or derived from inflammatory cells infiltrating the area. Two such important factors are: 1) VEGF, 2) basic FBG. These growth factors are highly produced by tumour cells ===> inducing tumour angiogenesis.

Is tumour angiogenesis inhibited as well? Yes, and this is done by presence of antiangiogenesis factors. Thus, tumour growth controlled by TAF & antiangiogenesis factors. Antiangiogenesis factors may be produced by tumour cells (e.g.: thrombospondin 1) or their production may be influenced by tumour cells. Angiostatin, endostatin, vasculostatin belong to the latter group. These are derived from cleavage of collagen, plasminogen & transthyretin.

Clinical trials are being done on whether therapy by antiangiogenesis factors will inhibit tumour growth.

Category: Pathology Notes