A combination of dietary protein depletion and PHA-induced gut growth reduce the mass of a murine non-Hodgkin lymphoma

The results presented in this study show that a switch from a non-protein diet (NPD) to one of a normal protein content (LA) on the day of subcutaneous injection of non-Hodgkin lymphoma tumour cells greatly favoured the development and growth of the tumour. Interestingly, however, inclusion of the plant lectin phytohaemagglutinin (PHA) in the LA diet appeared to compete with the effect of switch to the protein-rich diet, resulting in decreased tumour size and an increased incidence of necrosis. PHA was shown to induce hyperplasia of the gut even in the presence of the growing tumour. This observation together with the fact that gut hyperplasia also occurred in animals which were fed NPD supplemented with PHA, indicated the strength of PHA as a growth signal. It would seem likely that this ‘normal’ growth is able to compete with the tumour for important growth factors and nutrients, including polyamines, effectively starving the tumour for these molecules and resulting in its decreased rate of proliferation.