PURPOSE: Cumulative data support the role of ΔTAp73 variants in tumorigenic 
processes such as drug resistance. We evaluate the impact of TP73 isoforms and 
their putative target genes ABCB1, HMGB1, and CASP1 on the survival of colon 
cancer patients and the correlation between their expressions.
EXPERIMENTAL DESIGN: We determined in 77 colon cancer patients the expression of 
ΔEx2p73, ΔEx2/3p73, ΔNp73, TAp73, ABCB1, HMGB1, and CASP1 by quantitative 
real-time reverse transcriptase-PCR. Tumor characteristics, disease-free 
survival, and overall survival (OS) were examined in each patient. Functional 
experiments were carried out to check whether ectopic expression of ΔNp73 
modifies the proliferation, drug resistance, migration, and invasion properties 
of colon tumor cells and the expression of ABCB1, HMGB1, and CASP1.
RESULTS: Positive correlations were observed between the expression levels of 
ΔTAp73 variants and HMGB1. Furthermore, a trend was observed for ABCB1. 
Overexpression of ΔEx2/3p73 and ΔNp73 isoforms was significantly associated with 
advanced stages (P = 0.04 and P = 0.03, respectively) and predicted shortened OS 
(P = 0.04 and P = 0.05, respectively). High levels of ABCB1 and HMGB1 were 
associated with shorter OS (P = 0.04 and P = 0.05, respectively). Multivariate 
analysis showed that, in addition to the tumor stage, ABCB1 and HMGB1 had 
independent relationships with OS (P = 0.008). Ectopic expression of ΔNp73 was 
associated with an increase in proliferation and drug resistance.
CONCLUSIONS: The positive correlation between ΔTAp73 variants and HMGB1 and 
ABCB1 expression supports them as TP73 targets. The fact that upregulation of 
ΔTAp73 isoforms was associated with shortened OS, increase in proliferation, and 
drug resistance confirms their oncogenic role and plausible value as prognostic 
markers. ABCB1 and HMGB1, putative ΔTAp73 target genes, strongly predict OS in 
an independent manner, making clear the importance of studying downstream TP73 
targets that could predict the outcome of colon cancer patients better than 
ΔTAp73 variants themselves do.