This study aims to determine the effect of 1[alpha],25(OH)2D 3 and TPA on localization of 1,25 D3-MARRS and NF[kappa]B in APL NB4 cells; to determine the effects of 1[alpha],25(OH)2D 3 treatment on the association between 1,25D3-MARRS and NF[kappa]B. In this thesis, it is shown that 1,25D3-MARRS and NF[kappa]B associate constantly with one another in NB4 cells over a 2 h 1[alpha],25(OH) 2D3 time course. In addition, it is shown that 1[alpha],25(OH)2D3 leads to strong nuclear co-translocation of 1,25D3-MARRS and NF[kappa]B, when combined with TPA for 12 h; 1,25D3-MARRS is translocated to the nucleus when NB4 cells are treated with 1[alpha],25(OH)2D3 and TPA for 10 min. It is likely that 1[alpha],25(OH)2D3 has a priming effect on the association between 1,25D3-MARRS and NF[kappa]B protein, then interacts with TPA to cause them to translocate into the nucleus, where NF[kappa]B regulates the monocytic differentiation of NB4 cells.