Tumour metastasis as an adaptation of tumour cells to fulfil their phosphorus requirements.

Inorganic phosphate (Pi) is a vital component of nucleotides, membrane phospholipids, and phosphorylated intermediates in cellular signalling. The Growth Rate Hypothesis (GRH) states that fast growing organisms should be richer in phosphorus (relatively low C:P and N:P cell content) than slow developing organisms as a result of high ribosome biogenesis. Cells that proliferate rapidly, such as cancer cells, require a high amount of ribosomes and other P-rich RNA components that are necessary to manufacture proteins. The GRH hypothesis may be applied to cancer predicting that tumour cells are richer in phosphorus than the surrounding tissue, and that they resort to metastasis in order to meet their nutrient demands. Considering that the cells most P-deprived should be located in the inner parts of the tumour we propose that changes in the membrane of these cells favour the detachment of the more peripheral cells.