CD99 suppresses osteosarcoma cell migration through inhibition of ROCK2 activity

Abstract

CD99, a transmembrane protein encoded by MIC2 gene is involved in multiple cellular events including cell adhesion and migration, apoptosis, cell differentiation and regulation of protein trafficking either in physiological or pathological conditions. In osteosarcoma, CD99 is expressed at low levels and functions as a tumour suppressor. The full-length protein (CD99wt) and the short-form harbouring a deletion in the intracytoplasmic domain (CD99sh) have been associated with distinct functional outcomes with respect to tumour malignancy. In this study, we especially evaluated modulation of cell-cell contacts, reorganisation of the actin cytoskeleton and modulation of signalling pathways by comparing osteosarcoma cells characterised by different metastasis capabilities and CD99 expression, to identify molecular mechanisms responsible for metastasis. Our data indicate that forced expression of CD99wt induces recruitment of N-cadherin and β-catenin to adherens junctions. In addition, transfection of CD99wt inhibits the expression of several molecules crucial to the remodelling of the actin cytoskeleton, such as ACTR2, ARPC1A, Rho-associated, coiled-coil containing protein kinase 2 (ROCK2) as well as ezrin, an ezrin/radixin/moesin family member that has been clearly associated with tumour progression and metastatic spread in osteosarcoma. Functional studies point to ROCK2 as a crucial intracellular mediator regulating osteosarcoma migration. By maintaining c-Src in an inactive conformation, CD99wt inhibits ROCK2 signalling and this leads to ezrin decrease at cell membrane while N-cadherin and β-catenin translocate to the plasma membrane and function as main molecular bridges for actin cytoskeleton. Taken together, we propose that the re-expression of CD99wt, which is generally present in osteoblasts but lost in osteosarcoma, through inhibition of c-Src and ROCK2 activity, manages to increase contact strength and reactivate stop-migration signals that counteract the otherwise dominant promigratory action of ezrin in osteosarcoma cells.

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

“…Previous studies have reported that the cytoskeleton linker ezrin provides an early survival advantage for OS cells colonizing the lung, 29 and CD99 suppresses OS cell migration by inhibiting ROCK2, 30 In addition to EPLIN, we demonstrated that SATB2 regulates the expression of additional genes associated with cytoskeletal dynamics and adhesion such as ABI3, GSN and FMN2. The pathways altered by SATB2 are similar to those identified in breast cancer cells lacking SATB1.…”

Tuning Collective Cell Migration by Cell–Cell Junction Regulation

“…Epithelial tumors invade collectively, with duct-like patterns and E-cadherin and b-catenin positive cell-cell junctions, with or without lumen formation, and with or without up-regulation of EMT markers, including Twist and Zeb1 (Cheung et al 2013;Bronsert et al 2014). Furthermore, both E-and N-cadherin can orchestrate AJs and cell-cell interactions in cancer cells (Bronsert et al 2014;Zucchini et al 2014). Besides cadherins, Ig superfamily members and ephrins/EpH receptor systems were implicated in mediating more labile or transient cell-cell interactions in cancer cells (Cavallaro and Christofori 2004;Haeger et al 2014;Krusche et al 2016).…”

Possible Gender-Related Modulation by the ROCK1 Gene in Colorectal Cancer Susceptibility

“…Overexpression of ROCK has been described in many solid tumors, including hepatocellular carcinoma [18], osteosarcoma [19,20], breast cancer [21], testicular cancer [22], bladder cancer [23] and also colon cancer [24]. In addition, several studies have emphasized the antimigratory and anti-invasive activity due to ROCK inhibition [25,26,27,28] or silencing [18,24,29,30], reinforcing the association between the Rho-ROCK axis and cancer.…”