We evaluate whether 1,25(OH)(2)D(3) downregulates TP73 variants in colon and 
breast carcinomas, the role of survivin in this context, and the significance of 
this network in the clinic. Tumor cells were treated/untreated with 
1,25(OH)(2)D(3) and transiently transfected with survivin. Levels of survivin 
and TP73 variants were evaluated by quantitative RT-PCR and Western blotting. In 
75 colon and 60 breast cancer patients, the expressions of survivin and TP73 
isoforms were determined. Tumor characteristics were examined in each patient. 
Survivin protein levels were also evaluated in a subgroup of patients and cell 
lines. Decrease in survivin and TAp73 transcripts and protein and ΔNp73 mRNA was 
detected after 1,25(OH)(2)D(3) treatment. Ectopic survivin expression led to an 
increase in the TAp73, ΔNp73, ΔEx2p73, and ΔEx2-3p73 transcripts. In cancer 
patients, direct correlations were observed between TP73 variants and survivin 
levels. 1,25(OH)(2)D(3) negatively regulate survivin and TP73 variants in colon 
and breast cancer cells. Positive regulation of TP73 isoforms by survivin may 
exist, which reinforces the possibility that the downregulation of TP73 forms by 
1,25(OH)(2)D(3) is survivin-dependent.