The time of tumor cell division and death depends on the site of growth

We show here, for the first time, in two very different murine tumors, a ma mmary one (ectoderm) and a lung one (endoderm), that: tumors have day/night differences of spontaneous apoptosis additional to the well-known circadia n rhythm of mitosis. The times of maximal and minimal mitosis and apoptosis changed for a tumor cell line when growing in different organs (as metasta sis) or anatomical sites. Both tumor lines, have identical circadian curves when growing in a specific organ or anatomical site. The peaks of apoptosi s match with the valleys of mitosis and vice versa.