SATB2 Expression Affects Chemotherapy Metabolism and Immune Checkpoint Gene Expression in Colorectal Cancer.

Background: Special AT-rich binding protein-2 (SATB2) is a nuclear matrix associated protein regulating gene expression which is normally expressed in colonic tissue. Loss of SATB2 expression in colorectal cancer (CRC) has negative implications for prognosis and has been associated with chemotherapy resistance. Furthermore, recent evidence suggests SATB2 may influence immune checkpoint (IC) expression. We hypothesized that SATB2 expression may be associated with altered expression of chemotherapy resistance associated and IC genes.

Methods: Clinicopathologic and gene expression data were extracted from The Cancer Genome Atlas PanCancer Atlas. SATB2 expression was compared by clinicopathologic characteristic and by using multivariate regression analysis to explore associations with chemotherapy and IC gene expression.

Results: About 553 patients were included for analysis. Lower quartile SATB2 expression was associated with worse disease specific survival (P = .04). MSI (P < .001) and mucinous (P < .001) tumors were associated with reduced SATB2 expression independently. SATB2 varied by consensus molecular subtype (P < .001) and was lowest in CMS1. On multivariate analysis, SATB2 was negatively associated with 5-FU related metabolism genes, while more complex but significant relationships were seen with oxaliplatin and irinotecan related genes. Low SATB2 expression was associated with increased expression of PD-1, PD-L1, TIM-3 and CTLA-4 IC genes.

Conclusion: The positive prognostic influence of SATB2 expression is reaffirmed in this study. This effect may be explained by the negative association between SATB2 and 5-FU-resistance related gene expression. Enhanced IC gene expression in SATB2 low cases suggests a potential role for IC inhibition in this setting, but further study is required.