Cortactin underpins CD44-promoted invasion and adhesion of breast cancer cells to bone marrow endothelial cells

Abstract

Using a validated tetracycline (tet)-regulated MCF7-founder (MCF7F) expression system to modulate expression of CD44 standard form (CD44s), we report the functional importance of CD44s and that of a novel transcriptional target of hyaluronan (HA)/CD44s signaling, EMS1/cortactin, in underpinning breast cancer metastasis. In functional experiments, tet-regulated induction of CD44s potentiated the migration and invasion of MCF7F cells through HA-supplemented Matrigel. EMS1/cortactin was identified by expression profiling as a novel transcriptional target of HA/CD44 signaling, an association validated by quantitative PCR and immunoblotting experiments in a range of breast cancer cell lines. The mechanistic basis underpinning CD44-promoted transcription of EMS1/cortactin was shown to be dependent upon a NFjB mechanism, since pharmacological inhibition of IjKinase-2 or suppression of p65 Rel A expression attenuated CD44-induced increases in cortactin mRNA transcript levels. Overexpression of a c-myc tagged murine cortactin construct in the weakly invasive, CD44-deficient MCF7F and T47D cells potentiated their invasion. Furthermore, the functional importance of cortactin to CD44s-promoted metastasis was demonstrated by selective suppression of cortactin in CD44-expressing MCF7F-B5 and MDA-MB-231 breast cancer cells using RNAi, which was shown to result in attenuated CD44-promoted invasion and CD44-promoted adhesion to bone marrow endothelial cells (BMECs).

Separation and Characterization of Epithelial and Mesenchymal-like Murine Mammary Tumor Cells Reveals Epithelial Cell Differentiation Plasticity and Enhanced Tumorigenicity of Epithelial-enriched Tumor Cells

“…Expression of variant exons 3, 6, 8 and 10 have been associated with the invasive potential of tumors in numerous studies, as reviewed in [19]. However, studies have also indicated that expression of CD44s is associated with breast cancer metastasis [20,21], and there is recent evidence that expression of CD44s accelerates EMT and breast cancer progression [22]. Our data supports the association of CD44s with a mesenchymal phenotype.…”

Survivin Is a Novel Target of CD44-Promoted Breast Tumor Invasion

“…10 -13 The CD44 -HA complex initiates a series of intracellular signaling events that lead to migration, adhesion, invasion, proliferation, and differentiation of a variety of cells. The transduction of HA/CD44 signaling can occur through various mechanisms including the following: i) HA binding to CD44 can initiate the extracellular clustering of CD44, resulting in the activation of downstream kinases, 14 ii) CD44 can serve as a co-receptor physically associated with other cell signaling receptors, [15][16][17][18] iii) CD44 can serve as a docking protein for pericellular or cytoplasmic proteins, 19,20 and iv) the transmembrane domain of CD44 can be cleaved, allowing the translocation of the cytoplasmic domain to the nucleus, where it functions as a transcription factor regulating the expression of target genes such as CD44 itself. 21,22 CD44 and its variants can induce chemoresistance and invasion of human BC cell lines via different mechanisms.…”

“…[23][24][25][26][27] Despite knowing the role that CD44 -HA plays in promoting BC invasion and metastasis, the underlying downstream signaling mechanism is nascent. In an attempt to elucidate these downstream signaling mechanisms, we generated a tetracycline (tet)-off-inducible system of CD44 expression both in vitro 14 and in vivo. 16 These studies showed that induction of CD44 potentiated migration and invasion of BC cells 14 and promoted BC metastasis to the liver 16 through the CD44 -HA/NF-B/cortactin signaling pathway.…”

“…In an attempt to elucidate these downstream signaling mechanisms, we generated a tetracycline (tet)-off-inducible system of CD44 expression both in vitro 14 and in vivo. 16 These studies showed that induction of CD44 potentiated migration and invasion of BC cells 14 and promoted BC metastasis to the liver 16 through the CD44 -HA/NF-B/cortactin signaling pathway. 14 In the same study, 14 we identified the anti-apoptotic protein survivin (SVV) as a potential transcriptional CD44 downstream target gene involved in BC invasion and metastasis.…”

Prognostic significance of cortactin levels in head and neck squamous cell carcinoma: comparison with epidermal growth factor receptor status

“…Thus, the functional properties of cortactin, together with amplification of chromosome locus 11q13, suggest a link between its overexpression and tumour invasion and/or metastasis. Accordingly, in several animal models ectopic overexpression of cortactin has been shown to accelerate tumour dissemination, and decreased expression of cortactin, by RNA interference, leads to impaired tumour cell migration and metastasis (Li et al, 2001;Chuma et al, 2004;Hill et al, 2006;Luo et al, 2006).…”