CD44 and neoplasm: The belonging of tumor cells to the CD44+ fraction was also confirmed by the fact that the EC initiation by the fraction of CD44-cells even at a dose of 106 cells / mouse caused the formation of a tumor only in 50% of cases, with an absolute number of cells in the PC 5 times less than in under introduction of a similar amount of the total population of EC and more than 100 times less than after the introduced CD44+-fraction.