Expression and prognostic relevance of activated extracellular-regulated kinases (ERK1/2) in breast cancer

Abstract

Extracellular-regulated kinases (ERK1, ERK2) play important roles in the malignant behaviour of breast cancer cells in vitro. In our present study, 148 clinical breast cancer samples (120 cases with follow-up data) were studied for the expression of ERK1, ERK2 and their phosphorylated forms p-ERK1 and p-ERK2 by immunoblotting, and p-ERK1/2 expression in corresponding paraffin sections was analysed by immunohistochemistry. The results were correlated with established clinical and histological prognostic parameters, follow-up data and expression of seven cell-cycle regulatory proteins as well as MMP1, MMP9, PAI-1 and AP-1 transcription factors, which had been analysed before. High p-ERK1 expression as determined by immunoblots correlated significantly with a low frequency of recurrences and infrequent fatal outcome (P ¼ 0.007 and 0.008) and was an independent indicator of long relapse-free and overall survival in multivariate analysis. By immunohistochemistry, strong p-ERK staining in tumour cells was associated with early stages (P ¼ 0.020), negative nodal status (P ¼ 0.003) and long recurrence-free survival (P ¼ 0.017). In contrast, expression of the unphosphorylated kinases ERK1 and ERK2 was not associated with clinical and histological prognostic parameters, except a positive correlation with oestrogen receptor status. Comparison with the expression of formerly analysed cell-cycle-and invasion-associated proteins corroborates our conclusion that activation of ERK1 and ERK2 is not associated with enhanced proliferation and invasion of mammary carcinomas. Growth factors or cytokines exert positive and negative effects on cell proliferation and differentiation. After binding to their membrane receptors, the message is relayed to the nucleus by a complex system of intracellular signalling pathways. The majority of signalling molecules involved in these pathways are kinases, which are themselves activated by phosphorylation and repressed by their specific phosphatases. The mitogen-activated protein kinase (MAPK) signalling pathway includes a cascade of four groups of kinases (MAPKKKKs, MAPKKKs, MAPKKs and MAPKs). The MAPK kinase kinase kinases of the first level are phosphorylated in response to various extracellular stimuli through interaction with small GTP-binding proteins like Ras, Raf, etc. The activated enzymes then phosphorylate one of 14 kinases of the second level (the MAPKKKs, that is, Raf proteins, MEKK1-4, etc.), which themselves activate one of the MAPK kinases (MEK1 and 2, MKK3 -7) of the third level. Finally, these kinases (MAPKKs) activate MAP kinases, which are then able to phosphorylate transcription factors, which regulate the expression of genes involved in cell proliferation or differentiation. Three different, partly interacting signalling pathways have been identified in mammalian cells, leading to the activation of three types of MAP kinases: the MAP kinase JNK (Jun kinase) phosphorylates c-Jun, JunB, ATF2 and ELK1, etc., P38 activates ATF2, ELK-1 and MAX, whereas ERK1 and ERK2 phosphorylate...

C-Fos expression is a molecular predictor of progression and survival in epithelial ovarian carcinoma

“…Proteins were lysed in ice-cold sample buffer (50 mM Tris pH 6.8, 1% sodium dodecyl sulphate (SDS), 10% sucrose and 10 ml ml À1 protease inhibitor cocktail (Sigma, Taufkirchen, Germany)), and protein concentration was determined following the standard protocols and using bovine serum albumin protein standards as described previously (Bamberger et al, 1999;Milde-Langosch et al, 2005).…”

The CDK inhibitors in cancer research and therapy

“…Particularly, deregulated kinases are often found to be oncogenic and can be central for the survival of cancer cells (Hunter and Cooper 1985). Moreover, the phosphorylation of some proteins, such as ErbB2 (Cicenas et al 2006;Cicenas 2007;DiGiovanna et al 2005), EGFR (Cicenas 2007;Kanematsu et al 2003), Erk (Milde-Langosch et al 2005;Bergqvist et al 2006;Svensson et al 2005), SchA (Cicenas et al 2010), p21Cip1 (Xia et al 2004), p27Kip1 (Clarke 2003), Akt (Cicenas et al 2004(Cicenas et al , 2005Cicenas 2008) and retinoblastoma protein (Rb) (Derenzini et al 2007), is associated with prognosis in cancers.…”

Activated extracellular signal‐regulated kinase is an independent prognostic factor in clinically confined renal cell carcinoma

“…19,20 Much of the current literature that lends support for ERK-1/2 serving as a cancer driver has been generated by the use of in vitro, ex vivo, and mouse cancer models, with an actual paucity of studies that report its expression, activity, and significance in clinical tumor specimens. 21 Of the clinical immunohistologic studies undertaken to date, phosphorylated ERK (pERK) has been shown to correlate with disease progression in melanoma, 22 hepatocellular, 23 and nonsmall cell lung carcinomas. 24 In hepatocellular carcinoma, pERK is predominantly expressed in poorly differentiated tumors, and as such serves as a powerful prognostic factor.…”