The Invadopodia Scaffold Protein Tks5 Is Required for the Growth of Human Breast Cancer Cells In Vitro and In Vivo

Abstract

The ability of cancer cells to invade underlies metastatic progression. One mechanism by which cancer cells can become invasive is through the formation of structures called invadopodia, which are dynamic, actin-rich membrane protrusions that are sites of focal extracellular matrix degradation. While there is a growing consensus that invadopodia are instrumental in tumor metastasis, less is known about whether they are involved in tumor growth, particularly in vivo. The adaptor protein Tks5 is an obligate component of invadopodia, and is linked molecularly to both actin-remodeling proteins and pericellular proteases. Tks5 appears to localize exclusively to invadopodia in cancer cells, and in vitro studies have demonstrated its critical requirement for the invasive nature of these cells, making it an ideal surrogate to investigate the role of invadopodia in vivo. In this study, we examined how Tks5 contributes to human breast cancer progression. We used immunohistochemistry and RNA sequencing data to evaluate Tks5 expression in clinical samples, and we characterized the role of Tks5 in breast cancer progression using RNA interference and orthotopic implantation in SCID-Beige mice. We found that Tks5 is expressed to high levels in approximately 50% of primary invasive breast cancers. Furthermore, high expression was correlated with poor outcome, particularly in those patients with late relapse of stage I/II disease. Knockdown of Tks5 expression in breast cancer cells resulted in decreased growth, both in 3D in vitro cultures and in vivo. Moreover, our data also suggest that Tks5 is important for the integrity and permeability of the tumor vasculature. Together, this work establishes an important role for Tks5 in tumor growth in vivo, and suggests that invadopodia may play broad roles in tumor progression.

Transient mechanical strain promotes the maturation of invadopodia and enhances cancer cell invasion in vitro

“…Both integrin β1 and β3 are RGD-binding integrins (Branch et al, 2012) and are important in the regulation of invadopodia maturation (Beaty and Condeelis, 2014;Beaty et al, 2013;Knowles et al, 2013). As integrin β3 is downregulated upon mechanical stimulation, we examined the possibility that this was accompanied by an increase in activity of integrin β1, an integrin subunit known to localize to invadopodia (Mueller et al, 1999).…”

“…Invadopodia undergo three distinct phases in their lifetime: initiation, assembly and maturation. The formation of a core structure containing N-WASp (also known as WASL), Tks5 (also known as SH3PXD2A), cofilin and cortactin defines the initiation step (Artym et al, 2006;Blouw et al, 2015;Oser et al, 2009). The assembly phase requires the stabilization of these precursor proteins to continue the actin polymerization needed for maturation.…”

ADAM12 induction by Twist1 promotes tumor invasion and metastasis via regulation of invadopodia and focal adhesions

“…In rescue experiments, we observed that both the disintegrin domain and metalloproteinase domain of ADAM12 were necessary for rescuing the invadopodia formation defect, and could function in trans to do so. Adhesion rings containing integrins are found at invadopodia and have been shown to be crucial for invadopodia maturation (Branch et al, 2012). Therefore, the disintegrin domain of ADAM12 could potentially regulate adhesion ring dynamics around invadopodia to affect invadopodia formation.…”

The microenvironment controls invadosome plasticity

“…These linear invadosomes are formed along type I collagen fibrils and are found in both normal and transformed cells (Di Martino et al, 2015;Juin et al, 2012;Juin et al, 2014;Schachtner et al, 2013). Linear invadosomes present markers that are common to all invadosomes, such as the actin-binding proteins N-WASP and cortactin (Artym et al, 2006), the scaffold protein tyrosine kinase substrate 5 (Tks5, also known as SH3PXD2A) (Blouw et al, 2015) and the Rho GTPase Cdc42 (Di . Linear invadosomes, in contrast to invadosomes that are organised into individual dots, do not contain ring proteins, such as talin, vinculin, paxillin or integrins (Juin et al, 2012).…”