Chronic exposure to fulvestrant promotes overexpression of the c-Met receptor in breast cancer cells: implications for tumour–stroma interactions

Abstract

Our previous investigations using cell models of tamoxifen resistance have shown that the acquisition of an endocrine-insensitive state is accompanied by an invasive in vitro phenotype. In this study, we wished to determine whether this was specifically related to partial oestrogen receptor agonists or whether similar phenomena arise with the newer 'pure' anti-oestrogens, exemplified by fulvestrant. Our data demonstrate that the development of fulvestrant resistance in two breast cancer cell lines, MCF7 and T47D, is accompanied by an augmented migratory and invasive phenotype in vitro and overexpression of the HGF/SF receptor, c-Met. Importantly, upregulated c-Met expression in these cells facilitates their stimulation by HGF/SF-secreting stromal fibroblasts, leading to the activation of Src, Akt and ERK1/2 and a profound enhancement of their aggressive phenotype in vitro. These effects could be specifically attributable to activation of the c-Met receptor since the inclusion of neutralising antibodies to c-Met, or siRNA-mediated knockdown of c-Met expression, suppressed both invasion and migration stimulated by either exogenous HGF/SF, fibroblast-conditioned medium or following co-culture with fibroblast cells. Together, these in vitro data suggest that the development of fulvestrant resistance in vivo may confer a metastatic advantage to the cells by allowing their migratory and invasive behaviour to be augmented by surrounding stromal cells.

Transferrin receptor (CD71) is a marker of poor prognosis in breast cancer and can predict response to tamoxifen

“…Further models examined in log-phase comprised MCF-7-derived sub-lines that had acquired resistance to various endocrine strategies as follows: (1) the ER? MCF-7X model of acquired resistance to severe oestrogen deprivation (maintained in phenol-red RPMI medium supplemented with 5% heat-treated charcoal-stripped FCS [14] and (2) acquired anti-oestrogen resistant TAMR and FASR models (maintained in phenol-red-free RPMI medium containing 10 -7 M 4-OH-tamoxifen or Faslodex (FAS) [15][16][17]. All basal media were supplemented with penicillin-streptomycin (100 U/ml), fungizone (2.5 lg/ml), and L-glutamine (4 mM).…”

Inhibition of focal adhesion kinase suppresses the adverse phenotype of endocrine-resistant breast cancer cells and improves endocrine response in endocrine-sensitive cells

“…We have previously demonstrated that the development of endocrine resistance in breast cancer cells is accompanied by an increased migratory capacity in vitro [19,29]. Given that FAK is a key regulator or such behaviour, we first determined whether the expression and/or activation status of FAK differed in endocrine-sensitive MCF7 cells versus two acquired endocrine-resistant MCF7 derivatives.…”

“…Since TamR and FasR cells display a highly migratory phenotype compared to their poorly-migratory MCF7 counterparts [19,29], we addressed the role of FAK in this process. Inhibition of FAK activity corresponded to a significant inhibition of both TamR and FasR cell migration over fibronectin ( Figure 4C).…”

“…Recent in vitro studies using cell models of acquired tamoxifen and fulvestrant resistance had revealed that acquisition of resistance to such agents is accompanied by altered growth factor signalling [18] and the development of an aggressive, invasive phenotype [19,20] in which the FAK-associated kinase, Src, may play a central role [21]. However, despite the efficacy of Src inhibitors in suppressing these adverse characteristics of endocrine-resistant breast cancer cells, in cells lacking FAK, Src inhibitors do not provide added benefit in terms of suppression of cell migration, suggesting that the effects of Src on cell migration are mediated through FAK [22].…”

Efeitos morfológicos, histológicos e moleculares dos moduladores seletivos dos receptores de estrogênios tamoxifeno e raloxifeno na prevenção primária de tumores mamários quimicamente induzidos em ratas

“…Os relatos da literatura demonstram casos de superexpressão do HGF em tumores mamários mais agressivos e resistentes ao tamoxifeno, corroborando com os nossos achados (Hiscox et al, 2006;Kuske et al, 2006). O Hif1a (fator indutor de hipóxia, subunidade1) é um fator de transcrição encontrado em células de mamíferos, nas quais o gene supressor tumoral VHL (Von Hippel-Lindau) provoca a ubiquitinação do Hif em resposta à mudança na oxigenação tecidual.…”