Overexpression of cyclo‐oxygenase‐2 is an independent predictor of unfavourable outcome in node‐negative breast cancer, but is not associated with protein kinase B (Akt) and mitogen‐activated protein kinase (ERK1/2, p38) activation or with Her‐2/neu signalling pathways

K Schmitz

R Callies

J Wohlschlaeger

R Kimmig

K J Schmitz, J Wohlschlaeger, F Otterbach, J Bohr, H‐S Lee, K W Schmid, Institute of Pathology, University Hospital of Essen, Essen, Germany

R Callies, R Kimmig, Department of Obstetrics and Gynaecology, University Hospital of Essen

A Takeda, Department of Internal Medicine, Gumma Paz Gakuen College, Gumma, Japan

Correspondence to: H A Baba
Institute of Pathology, University Hospital of Essen, D‐45147 Essen, Hufelandstr 55, Germany; hideo.baba@medizin.uni‐essen.de

K J Schmitz, J Wohlschlaeger, F Otterbach, J Bohr, H‐S Lee, K W Schmid, Institute of Pathology, University Hospital of Essen, Essen, GermanyR Callies, R Kimmig, Department of Obstetrics and Gynaecology, University Hospital of EssenA Takeda, Department of Internal Medicine, Gumma Paz Gakuen College, Gumma, JapanCorrespondence to: H A Baba
Institute of Pathology, University Hospital of Essen, D‐45147 Essen, Hufelandstr 55, Germany; hideo.baba@medizin.uni‐essen.de

Accepted 2005 Oct 20.

Abstract

Background and aim

The production of prostaglandins is regulated by cyclo‐oxygenases (COXs), which also have a role in tumour development and progression in various malignancies, including breast cancer. The mechanisms by which COX‐2 contributes to unfavourable prognosis are still poorly understood. The association between expression of COX‐2 and possible linked signalling pathways—namely, Akt, extracellular regulated kinases (ERK1/2), the stress‐activated kinase p38 or Her‐2/neu—is assessed in a series of 113 node‐negative breast cancers.

Results

COX‐2 was identified as an independent prognostic factor (p = 0.034) in node‐negative breast cancer by survival analysis. The lack of a relationship between COX‐2 expression and activated Akt, Erk1/2, p38 and Her‐2/neu was indicated by statistical analysis.

Conclusions

The prognostic effect of COX‐2 expression on lymph node‐negative breast cancer is confirmed—COX‐2 is probably not regulated by HER‐2, Akt, Erk1/2 or p38. Further studies are necessary for the elucidation of the signalling pathways responsible for the modification of COX‐2 expression and the increased aggressiveness of breast cancers overexpressing COX‐2.

Abstract

Breast carcinoma is the most common malignancy in women. In the US, in 2005, about 211 000 cases of breast cancers were diagnosed, with 40 800 patients dying from the disease.¹ Besides commonly accepted prognostic markers such as lymph node status, tumour size and grade,² numerous other potential prognostic parameters have emerged. Among the potential prognostic parameters, cyclo‐oxgenase (COX)‐2 is of particular interest, as it may also offer the option of treatment with non‐steroidal anti‐inflammatory drugs (NSAIDs).³ Cyclo‐oxygenases regulate the synthesis of prostaglandins and are thus the major target of NSAIDs. Its two isoforms (COX‐1 and COX‐2) have different expression patterns, with COX‐1 being expressed in a broad variety of tissues. COX‐2 and its main product, prostaglandin E₂ (PGE₂), are inducible by growth factors and inflammatory stimuli. Additionally, COX‐2 has been shown to participate in tumour development and progression.⁴⁵ Prostaglandins exert their effects locally in both autocrine and paracrine patterns. The effects of PGE₂ are mediated by a family of G protein‐coupled receptors—namely, EP₁, EP₂, EP₃ and EP₄. The relevance of prostaglandins in breast cancer was studied by Bennett and Rolland more than 20 years ago—they found raised prostaglandin levels in breast cancer tissue and indicated that prostaglandin production may serve as a prognostic marker.⁶⁷⁸

Both COX‐2 mRNA and protein levels were found to be raised in human breast cancer, ⁹¹⁰ which was associated with decreased survival.¹¹¹² The application of NSAIDs was markedly associated with reduced development and progression of colonic tumours in patients with familial adenomatous polyposis (FAP),¹³¹⁴ whereas the data obtained on breast cancer are conflicting.¹⁵¹⁶

The mechanisms by which COX‐2 contributes to the poor prognosis have not been completely elucidated yet. COX‐2 has been shown to contribute to both tumorigenesis and the malignant phenotype of tumour cells by different mechanisms, including (1) the inhibition of apoptosis by increased production of PGE₂, leading to increased expression of Bcl‐2 and attenuation of nitric oxide (NO) signalling; (2) increased angiogenesis by increased PGE₂ production with subsequent vascular endothelial growth factor production; (3) increased invasiveness by overexpression of CD44; and (4) increased cell growth by activation of EP receptors.¹⁷ The growth factor‐mediated activation of the PI3‐kinase/PKB (Akt) pathway is a key element of cellular survival and proliferation. Four phosphorylation sites (serine 124, threonine 308, threonine 450 and serine 473) have been identified at the PH domain of Akt. Activation of the Akt kinase requires phosphorylation at the serine 473 and threonine 308 sites. So far, the studies evaluating the potential prognostic value of the Akt kinase in breast cancer have yielded conflicting results.¹⁸¹⁹ Activation of the Akt kinase is markedly associated with reduced overall disease‐specific survival.²⁰ St Germain and coworkers²¹²² suggested that the PI3‐kinase–Akt pathway participates in the regulation of COX expression. In addition to the serine–threonine kinase Akt, two members of mitogen‐activated protein kinase (MAPK) signalling pathways are implicated in the expression of COX‐2—namely, extracellular regulated kinases (ERK1/2) and stress‐activated protein kinase p38.²³ A recent study identified stress‐activated kinase p38 as an upstream regulator of COX‐2 expression and showed overexpression of both phospho‐p38 (pp38) and COX‐2 in ductal carcinoma in situ.²⁴ Besides the Akt and MAPK signalling pathways, Her‐2/neu has also been implicated in the regulation of COX‐2.²⁵

This immunohistochemical study assesses the possible association between COX‐2 expression and the activation of putative signalling pathways, namely phospho‐Akt (pAkt; serine 473 and threonine 308), phospho‐ERK (pERK)1/2, pp38 or Her‐2/neu, in a series of 113 node‐negative breast cancers.

Acknowledgements

The technical assistance of Dorothe Möllmann is acknowledged.

Acknowledgements

Abbreviations

COX - cyclo‐oxygenase

ERK - extracellular regulated kinases

FAP - familial adenomatous polyposis

FISH - fluorescent in situ hybridisation

IHC - immunohistochemistry

MAPK - mitogen‐activated protein kinase

NSAID - non‐steroidal anti‐inflammatory drug

pAkt - phospho‐Akt

pERK - phospho‐ERK

PGE₂ - prostaglandin E₂

pp38 - phospho‐p38

SSC - sodium salt citrate

Abbreviations

Footnotes

Competing interests: RK, FO AND KWS are members of the West German Cancer Centre Essen (WTZE), Essen, Germany. KJS, RC, JW, RK, FO, KWS and HAB are members of the University Breast Cancer Centre Essen, Essen, Germany.

Footnotes

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