SMAD7 is a prognostic marker in patients with colorectal cancer.
Chromosomal region 18q21 is frequently deleted in colorectal cancer (CRC) and is associated with poor prognosis. Potential tumor suppressor mechanisms altered by 18q21 deletion include mediation of TGFbeta signaling by SMADs. Following the definition of SMAD4 deletion as a negative predictive marker for chemotherapy benefit in patients with CRC, we aimed to evaluate the clinical relevance of the deletion of other SMAD genes clustered in this region: SMAD2 and SMAD7 in 264 CRC biopsies from a previous clinical study. In contrast to SMAD2 deletion, for which no clinical relevance was observed, hazard ratios (HR) in a multivariate analysis associated with SMAD7 deletion [overall survival (OS): HR = 0.43, p = 0.0012; disease-free survival (DFS): HR = 0.50, p = 0.0033] indicated a favorable outcome for these patients. In addition, SMAD7 duplication had a hazardous effect on survival [OS: HR = 2.10, p = 0.020; DFS: HR = 2.06, p = 0.015]. Moreover, the HRs associated with one additional copy of SMAD7 were 1.76, p = 0.00024 [OS] and 1.64, p = 0.00048 [DFS] respectively, showing a graded effect of SMAD7 on patient outcome depending on gene copy number that suggests a dose-and-effect basis. Since SMAD7 blocks TGFbeta signaling, these data are consistent with the loss of SMAD7 rendering carcinoma cells more sensitive to cell growth arrest/apoptotic effect of TGFbeta, whereas gain of SMAD7 function might result in TGFbeta resistance, thereby emphasizing the role of TGFbeta in tumor suppression.
Boulay
Jean-Louis
JL
Department of Research, University Hospital, Basel, Switzerland. jean-louis.boulay@unibas.ch
Mild
Gabriele
G
Lowy
Adam
A
Reuter
Juergen
J
Lagrange
Magali
M
Terracciano
Luigi
L
Laffer
Urban
U
Herrmann
Richard
R
Rochlitz
Christoph
C
D014408:Biomarkers, Tumor; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000401:mortality; D004268:DNA-Binding Proteins / Q000235:genetics*; D018572:Disease-Free Survival; D017353:Gene Deletion; D018628:Gene Dosage; D016163:Genes, DCC / Q000502:physiology; D006801:Humans; D011379:Prognosis; D051901:Smad4 Protein; D051906:Smad7 Protein; D015534:Trans-Activators / Q000235:genetics*
D014408:Biomarkers, Tumor; D004268:DNA-Binding Proteins; C497796:SMAD4 protein, human; C497806:SMAD7 protein, human; D051901:Smad4 Protein; D051906:Smad7 Protein; D015534:Trans-Activators