SATB2 enhances migration and invasion in osteosarcoma by regulating genes involved in cytoskeletal organization

Abstract

Osteosarcoma (OS) is the most common malignant bone tumor and the majority of recurrences are due to metastasis. However, the molecular mechanisms that regulate OS metastatic spread are largely unknown. In this study, we report that special AT-rich-binding protein 2 (SATB2) is highly expressed in OS cells and tumors. Short hairpin RNA-mediated knockdown of SATB2 (sh-SATB2) decreases migration and invasion of OS cells without affecting proliferation or viability. Microarray analysis identified genes that were differentially regulated by SATB2 including the actin-binding protein Epithelial Protein Lost In Neoplasm (EPLIN), which was upregulated in sh-SATB2 cells. Silencing EPLIN rescues the decreased invasion observed in sh-SATB2 cells. Pathway analyses of SATB2-regulated genes revealed enrichment of those involved in cytoskeleton dynamics, and increased stress fiber formation was detected in cells with SATB2 knockdown. Furthermore, sh-SATB2 cells exhibit increased RhoA, decreased Rac1 and increased phosphorylation of focal adhesion kinase (FAK) and paxillin. These findings identify SATB2 as a novel regulator of OS invasion, in part via effects on EPLIN and the cytoskeleton.

Special AT‐rich sequence‐binding protein 2 (SATB2) expression is sensitive but may not be specific for osteosarcoma as compared with other high‐grade primary bone sarcomas

“…The finding could be explained by SATB2 expression in other lineages or cross‐reaction of the antibody with other nuclear proteins that are not specific to osteosarcoma. However, substantial in‐vitro evidence suggests that, in the skeleton at least, SATB2 is a specific marker of osteoblastic regulation and differentiation . Taken together, these observations provide an alternative explanation for the expression of SATB2 in UPS and fibrosarcoma; namely, that a subset of these tumours represent osteosarcomas that produce too little bone or osteoid to be detected, even after extensive sampling.…”

“…Alternatively, the SATB2‐positive undifferentiated tumours may represent malignancies of the osteoblast lineage that are too primitive to synthesize matrix components. Studies examining the developmental pathways of bone have shown that osteoblastic differentiation occurs with SATB2 acting in concert with many regulatory genes and transcription factors, including RUNX2 and microRNAs (miRNAs) . RUNX2 is the earliest regulator of osteogenic development, and it then up‐regulates SATB2 protein expression, both directly and indirectly through repression of miRNAs, as miRNAs suppress SATB2 expression .…”

SATB2 expression increased anchorage-independent growth and cell migration in human bronchial epithelial cells

“…The dynamics of actin cytoskeleton are regulated by small Rho GTPases including Rho, Rac and Cdc42 [33]. In a recent study by Seog et al [8], SATB2 was found to be highly expressed in osteosarcoma cells and tumors. Knockdown SATB2 decreased migration and invasion without affecting proliferation or viability.…”

“…In colorectal cancer, high expression of SATB2 is associated with a favorable prognosis and increased sensitivity to radiation and chemotherapy [6], and overexpression of SATB2 in DLD-1 cells reduced anchorage-independent growth and tumor size when injected to nude mice [7], indicating a tumor suppressor role for SATB2. On the other hand, high SATB2 expression was observed in osteoscarcoma tumors cells, and migration and invasion was decreased by SATB2 knockdown [7, 8]. Moreover, in a breast cancer study, SATB2 mRNA expression was associated with increased tumor grade and poor overall survival [9] indicating a tumor promoting activity.…”

Role of miR‐31 and SATB2 in arsenic‐induced malignant BEAS‐2B cell transformation

“…In line with the finding that SATB2 reduction eliminated the transformation properties of arsenic‐transformed cells, we investigated whether knocking down of SATB2 in normal BEAS‐2B cells prior to arsenic exposure would prevent arsenic‐induced cell transformation. Of note, under normal conditions, SATB2 is only weakly expressed in the lung, but not detectable in BEAS‐2B cells . We knocked down SATB2 in BEAS‐2B cells that do not express this gene, using stable shRNA transfection to prevent its expected increase in expression after exposure to arsenic.…”