Abstract
BackgroundSpecial AT-rich sequence-binding protein 1 (SATB1) is a global gene regulator that has been reported to confer malignant behavior and associate with poor prognosis in several cancer forms. SATB1 expression has been demonstrated to correlate with unfavourable tumour characteristics in rectal cancer, but its association with clinical outcome in colorectal cancer (CRC) remains unclear. In this study, we examined the prognostic impact of SATB1 expression in CRC, and its association with important molecular characteristics; i.e. beta-catenin overexpression, microsatellite instability (MSI) screening status, and SATB2 expression.MethodsImmunohistochemical expression of SATB1 and beta-catenin was assessed in tissue microarrays with tumours from 529 incident CRC cases in the prospective population-based Malmö Diet and Cancer Study, previously analysed for SATB2 expression and MSI screening status. Spearmans Rho and Chi-Square tests were used to explore correlations between SATB1 expression, clinicopathological and investigative parameters. Kaplan Meier analysis and Cox proportional hazards modelling were used to explore the impact of SATB1 expression on cancer specific survival (CSS) and overall survival (OS).ResultsSATB1 was expressed in 222 (42%) CRC cases and negative, or sparsely expressed, in adjacent colorectal mucosa (n = 16). SATB1 expression was significantly associated with microsatellite stable tumours (p < 0.001), beta-catenin overexpression (p < 0.001) and SATB2 expression (p < 0.001). While not prognostic in the full cohort, SATB1 expression was significantly associated with poor prognosis in SATB2 negative tumours (HR = 2.63; 95% CI 1.46-4.71; pinteraction = 0.011 for CSS and HR = 2.31; 95% CI 1.32-4.04; pinteraction = 0.015 for OS), remaining significant in multivariable analysis.ConclusionsThe results of this study demonstrate that SATB1 expression in CRC is significantly associated with beta-catenin overexpression, microsatellite stability and SATB2 expression. Furthermore, SATB1 expression is a factor of poor prognosis in SATB2 negative tumours. Altogether, these data indicate an important role for SATB1 in colorectal carcinogenesis and suggest prognostically antagonistic effects of SATB1 and SATB2. The mechanistic basis for these observations warrants further study.Virtual slidesThe virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1922643082772076
Highlights
Special AT-rich sequence-binding protein 1 (SATB1) is a global gene regulator that has been reported to confer malignant behavior and associate with poor prognosis in several cancer forms
We have previously demonstrated that special AT-rich sequence-binding protein 2 (SATB2), a nuclear matrix associated protein and epigenetic regulator that orchestrates the function of multiple genes [2], is expressed in a highly tissue-specific manner in normal mucosa of the lower gastrointestinal tract and in colorectal cancer (CRC) [3,4]
The T-lineage enriched global chromatin organizer SATB1 [6,7] is a close homologue to Special AT-rich sequence-binding protein 2 (SATB2), and expression of SATB1 has been reported to correlate with poor prognosis in several cancer forms, e.g. breast, gastric and liver cancer [8,9,10,11]
Summary
Special AT-rich sequence-binding protein 1 (SATB1) is a global gene regulator that has been reported to confer malignant behavior and associate with poor prognosis in several cancer forms. SATB1 expression has been demonstrated to correlate with unfavourable tumour characteristics in rectal cancer, but its association with clinical outcome in colorectal cancer (CRC) remains unclear. We examined the prognostic impact of SATB1 expression in CRC, and its association with important molecular characteristics; i.e. beta-catenin overexpression, microsatellite instability (MSI) screening status, and SATB2 expression. MRNA and protein levels of SATB1 were found to correlate with unfavourable tumour characteristics in rectal cancer, but the prognostic significance of SATB1 expression was not reported [12]. As activation of the WNT signaling pathway and its major mediator betacatenin is a critical event in colorectal carcinogenesis [13], and SATB1 has been shown to interact with and recruit beta-catenin to its genomic binding sites, the role of SATB1 in CRC development and progression merits further investigation
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