The present invention relates to a method of enhancing cell homing and engraftment potential, the method comprises ex-vivo or in vitro subjecting a population of cells to an amount of nicotinamide for a period of time sufficient for enhancing cell homing and engraftment potential, the method is further characterized by at least one of the following: (i) wherein said amount of nicotinamide and said period of time are selected sufficient to down regulate CD26 expression by cells of said population of cells but not for stem and/or progenitor cell expansion； (ii) said population of cells does not include, mononuclear cells, early liver progenitor cells, committed progenitor cells, non-hematopoietic stem and progenitor cells, or embryonic stem and progenitor cells； (iii) said subjecting is in the absence of nutrients； (iv) said subjecting is in the absence of a cytokine； (v) said subjecting is in the absence of FLT-3 ligand； (vii) said subjecting is in the absence of stem cell factor (SCF)； (vii) said subjecting is in the absence of granulocyte colony stimulating factor (GCSF)； (viii) said subjecting is in the absence of an early acting cytokine； and (ix) said subjecting is in the absence of a late acting cytokine； and wherein said population of cells does not include a hematopoietic stem and/or progenitor cell population.
