Breast cell invasive potential relates to the myoepithelial phenotype

Abstract

On the basis of marker profile, the majority of breast carcinomas are thought to be derived from luminal epithelial cells; however, a subgroup of tumours with more mesenchymal characteristics are associated with a worse prognosis. The hypothesis of our study is that some breast carcinomas exhibit myoepithelial rather than pure mesenchymal differentiation and that acquisition of myoepithelial characteristics confers an aggressive phenotype. Pure luminal epithelial cells and fibroblasts are readily distinguished by many markers but distinguishing between myoepithelial and fibroblast cell lineages is more problematic. The markers found to be most discriminating in our study were CK14, ␣6␤4 integrin and the myoepithelial-associated desmosomal cadherin DSg3. These markers were applied to a series of breast cell lines and purified normal breast cell populations and the expression profile related to in vitro invasive behaviour. This demonstrated that expression of one or more myoepithelial markers by tumour cells (MDA MB 231, MDA MB 468, MDA MB 436) was associated with a high invasive capacity compared with cells with a pure luminal phenotype (MCF-7, T47D, ZR75). To address why myoepithelial characteristics are associated with higher invasion, the in vitro behaviour of normal myoepithelial cells and two other nontumourigenic breast cell lines (MCF-10A, HBL100) was also analysed. Primary myoepithelial cells from normal human breast exhibit a high invasive capacity when grown at low density, suggesting that invasive capacity is part of the myoepithelial phenotype. In keeping with this, both nontumourigenic cell lines exhibited features of the myoepithelial phenotype and a high invasive capacity. These results suggest that tumours that exhibit a myoepithelial phenotype may be clinically more aggressive because a high invasive capacity is intrinsic to the myoepithelial phenotype. © 2003 Wiley-Liss, Inc. Key words: myoepithelial cell; invasion; breast cancerThe normal human nonpregnant breast comprises a system of branching ducts, terminating in lobules embedded in interstitial stroma. The glandular structures are composed of 2 distinct epithelial cell types: the inner luminal epithelium and the outer attenuated myoepithelium, which forms the predominant interface with the basement membrane. 1,2 The myoepithelial cells are contractile cells, as indicated by their expression of ␣-smooth muscle actin, but they are likely to have a more central role in controlling the breast microenvironment. This is reflected in their high-level expression of the integrin receptors ␣2␤1, ␣3␤1, ␣6␤4, 3,4 growth factors and their receptors including members of the fibroblast growth factor family 5 and epidermal growth factor receptor 6 and other proteins including the common acute lymphoblastic leukaemia antigen (CALLA), which is identical to the neutral endopeptidase Ϫ24.11. This is involved in the hydrolysis of biologically active peptides and has been implicated in the control of growth and differentiation in the mammary gland. 7,8 In contra...

Nek3 kinase regulates prolactin-mediated cytoskeletal reorganization and motility of breast cancer cells

“…In addition, a significant decrease in T47D invasion through a Type I collagen substratum was noted following siRNA-mediated knockdown of Nek3. Although not as invasive as some less well-differentiated cell lines (Nawrocki et al, 2001;Gordon et al, 2003), T47D cells were obtained from a malignant pleural effusion, suggesting a role for Nek3 in metastatic phenotype in some breast cancer lineages.…”

“…Western-blot analysis showed comparable Nek3 siRNA knockdown efficiency in both T47D, and MDA-MB231 cells (Figure 3a), eliminating this as a potential reason for this difference in findings. In contrast to T47D, which has been genotyped to the well-differentiated 'luminal' phenotype of breast cancer, MDA-MB231 cells lack expression of E-cadherin and express matrix metalloproteinases, which are properties associated with a more aggressive tumorigenic phenotype, consistent with its 'basaloid' phenotype (Nawrocki et al, 2001;Gordon et al, 2003). In addition, MDA-MB231 cells have a significantly higher in vitro invasive index (Nawrocki et al, 2001;Gordon et al, 2003), are metastatic in nude mice (Inoue et al, 1993;Yoneda et al, 1997;Salcedo et al, 2000;Salcedo et al, 2002) and may therefore possess additional mutations that can circumvent Nek3 regulation.…”

“…In contrast to T47D, which has been genotyped to the well-differentiated 'luminal' phenotype of breast cancer, MDA-MB231 cells lack expression of E-cadherin and express matrix metalloproteinases, which are properties associated with a more aggressive tumorigenic phenotype, consistent with its 'basaloid' phenotype (Nawrocki et al, 2001;Gordon et al, 2003). In addition, MDA-MB231 cells have a significantly higher in vitro invasive index (Nawrocki et al, 2001;Gordon et al, 2003), are metastatic in nude mice (Inoue et al, 1993;Yoneda et al, 1997;Salcedo et al, 2000;Salcedo et al, 2002) and may therefore possess additional mutations that can circumvent Nek3 regulation. Although Western-blot analysis of equal amounts of protein in both cell lines showed no remarkable differences in basal Nek3 expression (Figure 3a), differences in PRL-mediated kinase activity and consequently phosphorylation of other proteins linked to cancer motility such as Vav2, PI3K, MAPK and paxillin may be significant.…”

Indole-3-carbinol-induced death in cancer cells involves EGFR downregulation and is exacerbated in a 3D environment

“…29 Moreover, drug resistance tests using collagen gel culture have proved to be accurate and highly predictive. 30,31 All cell lines used in this study express α2β1 integrin, 32 responsible for adhesion to collagen I. The other 3D model we investigated was spheroid culture, because in some cases cells in spheroids are more resistant to cytotoxic agents than in monolayer culture.…”

Factors influencing retention of adenovirus within tumours following direct intratumoural injection

“…In contrast, ZR75.1 is a typical luminal epithelial cell that grows as cohesive sheets, expressing E-cadherin, epithelial membrane antigen and human milk fat globulin 1 but not matrix metalloproteinase 7, vimentin or tenascin and with a low invasive capacity. 21 Knowledge of the factors that influence drainage of virus from these tumours, and how such factors may be controlled, could help enhance transduction and reduce toxicity, potentially improving therapeutic outcome.…”