SATB1 (special AT-rich binding protein 1) is a global chromatin organizer regulating the expression of a large number of genes. Overexpression has been found in various solid tumors and positively correlated with prognostic and clinicopathological properties. In colorectal cancer (CRC), SATB1 overexpression and its correlation with poor differentiation, invasive depth, TNM (tumor, nodes, metastases) stage and prognosis have been demonstrated. However, more detailed studies on the SATB1 functions in CRC are warranted. In this article, we comprehensively analyze the cellular and molecular role of SATB1 in CRC cell lines with different SATB1 expression levels by using RNAi-mediated knockdown. Using siRNAs with different knockdown efficacies, we demonstrate antiproliferative, cell cycle-inhibitory and proapoptotic effects of SATB1 knockdown in a SATB1 gene dose-dependent manner. Tumor growth inhibition is confirmed in vivo in a subcutaneous tumor xenograft mouse model using stable knockdown cells. The in-depth analysis of cellular effects reveals increased activities of caspases-3, -7, -8, -9 and other mediators of apoptotic pathways. Similarly, the analysis of E-and N-cadherin, slug, twist, b-catenin and MMP7 indicates SATB1 effects on epithelial-mesenchymal transition (EMT) and matrix breakdown. Our results also establish SATB1 effects on receptor tyrosine kinases and (proto-)oncogenes such as HER receptors and Pim-1. Taken together, this suggests a more complex molecular interplay between tumor-promoting and possible inhibitory effects in CRC by affecting multiple pathways and molecules involved in proliferation, cell cycle, EMT, invasion and cell survival.Colorectal cancer (CRC) is one of the most common causes for cancer-related deaths in the Western world. 1 Although methods of diagnosis and treatment have improved over the last few decades, the tumor stage at diagnosis is still most important for prognosis, and the overall survival of patients with advanced CRC is still poor owing to the high risk of metastasis. 2 The special AT-rich binding protein 1 (SATB1) is a global chromatin organizer that regulates the expression of a large number of genes. 3 SATB1 interacts with the altered sugarphosphate backbone of the DNA that is specific for doublestranded base-unpairing regions (BURs). BURs are often found in matrix attachment regions (MARs) at the base of chromatin loops. 4 In the nuclei of thymocytes, SATB1 has a cage-like network distribution and tethers specialized DNA sequences onto its network. 5 Furthermore, SATB1 targets chromatin remodeling complexes to DNA at the base of chromatin loops, functioning as a "landing platform" for chromatin remodeling enzymes. 6 In this way, SATB1 folds chromatin into loops and regulates the expression of a multitude of genes in cell type-and cell function-specific manners. 5,7-10 Under physiological conditions, SATB1 is required for the development of thymocytes 8 and the activation of Th2 cells. 7 Furthermore, SATB1 participates in Xchromosome inactivation, 11 development...