Kinetic perturbations during cancer therapy

Circadian rhythm of cell division

The existence of circadian oscillations in the level of hormones, in numerous physiological parameters, in toxicity and in behavior is now fully recognized in all living organisms. In contrast, the synchronisation and regulation of cell proliferation by circadian rhythms in vivo is only starting to be appreciated. This article reviews the experimental evidence for circadian synchronisation of cell division in different mammalian tissues (mainly the gastro-intestinal tract and hemapoietic system), including tumoral tissues. The possible causes of this coupling of the cell cycle phases to the circadian rhythm are discussed. Testing of novel antitumour agents using murine models should take into consideration the temporal difference between murine and human circadian control of proliferation (the peak of DNA synthesis occurs during the activity period, i.e. during daytime in man, and at night-time in mice and rats). Experimental and clinical data clearly support the important implications of the circadian control of the cell cycle in the optimisation of cancer chemotherapy, both for reducing toxicity and increasing the antitumour effects.

Cell and molecular mechanisms of pathogenesis and treatment of cancer

Surgery remains the mainstay of treatment for most classes of human solid tumours, with the principal exception of lymphomas, but it is insufficient in many cases to guarantee cure. With few exceptions, recurrent and metastatic solid tumours continue to defy attempts to develop effective adjuvant therapies. Recent insights into tumour biology reveal an increasingly complex picture of cell and molecular processes which confer heterogeneity and resistance to treatment upon tumours. These insights may also yield new targets for more effective adjuvant therapies.

Growth of metastases of the mouse adenocarcinoma EO 771: an allometric relationship between growth of the primary tumors and their metastases

Growth and cell kinetic parameters have been studied of paraaortal lumbar lymph node metastases of the mouse adenocarcinoma EO 771 growing intramuscularly in the thigh. An allometric relationship was found between the growth of the metastasis and that of the primary tumor, i.e. a linear relationship exists between the logarithm of the size of the metastasis and that of the primary tumor which permits the estimation of the growth rate of the metastasis based on the growth curve of the primary tumor. However, growth of metastases differs quantitatively from that of the primary tumor: the specific growth rate (growth rate per unit size) of the metastasis (1) is greater than that of the simultaneously growing primary tumor but (2) is smaller than that of the primary tumor of the same size as the metastasis. The allometric growth relationship further suggests that metastases originate later than is generally predicted presuming exponential growth of metastasis.