Tumour cells nutrients

This technique is only appropriate for normal cells which on serum deprivation arrest in Gl. Tumour cells often (but not always) arrest in other parts of the cell cycle usually as a result of deficiency in the supply of nutrients rather than as a result of depletion of serum supplied growth factors (Chapter 2). 

The model was adapted from Kontoravdi et al. (2005) for cell growth/death, nutrient uptake, and major metabolism. The model was further developed to include description of cell cycle sub-populations. The cell cycle representation was based on the yeast model of Uchiyama Shioya (1999) and the tumour cell model of Basse et al. (2003). Eq.(l)-(4) express viable cell concentration(Xv[cell L" ]) in terms of cells in Gq/Gi, S, and G2/M phases. As a simplification in notation, Gq/Gi cells will be indicated as G unless otherwise stated. Xoi, Xs, X02/M [cell L" ] are concentrations of viable cells in Gq/Gi, S, and G2/M phase, respectively, whereas Fo ,[L h" ] is the outlet flowrate. F[L] is the cell culture volume b, ki, k [h" ] are the transition rates of cells from Gi to S, S to G2, and M to Gi respectively and /[Pg.110]

In the course of tissue augmentation (hyperplasia), the tumour outgrows into the surrounding tissue. To grow further and satisfy the increased demand for nutrients, the tmnour requires the formation of new blood vessels (angiogenesis) (Fig. 5.120). [300] Eventually, cancer cells are released into the blood or lymph system and disseminated into other organs to establish secondary tumours (metastases). 

In more complex systems such as tissues and tumours not all cells will be involved in an active cell cycle. This introduces two further concepts of growth fraction and cell loss. The term GO has been adopted to refer to those cells that are out of cycle. However, this rather nondescript term is used to describe cells that may be out of cycle for vastly different reasons. Cells may be out of cycle because they have started the process of differentiation and maturation or they may have reached their life span and are undergoing cell death. They may be in a poorly vascularized area of the tissue and cannot continue their cycle due to nutrient deprivation this may leave them in a state of temporary h3 poxia in which they may be able to re-enter the cycle if the microenvironment improves or they may die if the situation becomes chronic. Cell loss also describes a diversity of underlying processes from exfoliation in mucosal tissues to programmed cell death or apoptosis, necrosis, or even metastatic loss in tumours. 

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