Elsevier

The Breast

Volume 12, Issue 2, April 2003, Pages 111-119
The Breast

ORIGINAL ARTICLE
Clinicopathological study of the expression of hsp27, pS2, cathepsin D and metallothionein in primary invasive breast cancer

https://doi.org/10.1016/S0960-9776(02)00290-4Get rights and content

Abstract

Expression of the hormone-related proteins hsp27, pS2, and also of cathepsin D (CD) and metallothionein (MT) was studied by immunohistochemistry and analyzed against clinical data in breast cancer. Archived material of paraffin-embedded breast carcinoma tissues from a cohort of 134 patients with primary invasive breast cancer was used. Hsp27 and pS2 (>10% of tumor cells stained) were found to be expressed in 63.6% and 37.6% of cases, respectively, and were correlated negatively with grading (P=0.006 and 0.01) and positively with estrogen receptors (ER) (P=0.04 and 0.04). pS2 expression was correlated with lymph node status (P=0.02), tumor size (P=0.01), progesterone receptor (PR) content (P=0.02), hsp27 (P=0.015) and bcl-2 protein (P=0.001). An inverse relationship between pS2 expression and the expression of p53 protein (P=0.005) and proliferation-associated index MIB1 (P<0.0001) was noted. Stromal cathepsin D was positively correlated with tumor grade (P=0.01), PCNA (P=0.007), MIB1 (P=0.001) and p53 (P=0.01), and negatively with ER (P=0.04) and bcl-2 (P<0.0001). MT was correlated positively with stromal CD (P=0.007) and inversely with PgR (P=0.04). Univariate analysis showed CD expression to be a positive prognostic factor for survival (P=0.035), with borderline significance, while MT was more strongly positive (P=0.01). However, none of the proteins studied was found to be related to disease outcome in univariate analysis. Our data show that hsp27, pS2 and stromal CD expression may reflect tumor differentiation and the functional status of ER in breast cancer, but stromal CD and tumor MT expression were the only factors found that may be of limited prognostic value.

Introduction

Beast cancer is controlled to large extent by estrogen, and several proteins have been implicated in the same pathogenetic pathways of breast carcinogenesis. We chose to study the expression of four estrogen-regulated proteins and test for any prognostic significance and predictive power in terms of response to tamoxifen. These proteins have been evaluated separately in other studies, with controversial results.

Hsp27 is a heat-shock protein (hsp) that is overexpressed in human breast cancer cells.1 Hsps are synthesized in response to a wide variety of stressful stimuli, such as heavy metals, oxidants, and viral and microbial infections with the biological purpose of rendering the cells resistant to further and more severe stress. Interestingly, these proteins have been shown to be synthesized under hormonal control. It has been suggested that hsp27 expression may have some prognostic importance in breast cancer.2,3 High levels of hsp27 are expressed mainly in estrogen target organs of the female reproductive system,4–6 while several studies have linked its expression with drug resistance,7–9 viral neoplasia,10 and cell development, differentiation and growth.3,11,12

pS2 protein was first detected in an estrogen-dependent breast cancer cell line in response to estrogen stimulation.13 In subsequent studies pS2 mRNA and pS2 protein expression were found to correlate with estrogen receptor (ER).14–17 It has also been suggested that it is a favorable prognostic factor and a good predictor of responsiveness to hormone therapy.18−19 pS2 has been proposed as a useful guide to selection of the appropriate adjuvant therapy for breast cancer patients.21 However, the function of pS2 and its biological significance remain unclear, contradictory reports suggesting pS2 that is an independent prognostic marker in breast cancer.15,18,19,21,22

The prognostic role of cathepsin D (CD, an estrogen-inducible lysosomal enzyme) also remains unclear, and conflicting data have been published relating to its prognostic value in breast cancer.23–29 Metallothioneins (MTs) represent a group of low-molecular-weight cystein-rich intracellular proteins that bind and detoxify a group of IIb heavy metals. MTs are implicated in a transient response to any form of stress or injury providing a cytoprotective mechanism against potential damaging effects of oxygen-derived free radicals.30 MTs have been described in a wide variety of tumors, including breast cancer and have been associated with disease progression and poor prognosis.31–35 In addition, MT, like hsp27, may play some part in drug resistance mechanisms36 and is correlated with hormone receptor status.31,32,35,37,38

In this study we assessed the expression of hsp27, pS2, CD and MT in a series of invasive breast cancers in an attempt to clarify their potential clinical importance. Their expression was correlated with the expression of steroid receptors [ER, progesterone receptor (PgR)] other known, potential prognostic factors (p53, bcl-2, MIB1, and PCNA) and standard clinicopathological parameters (tumor grade and size, lymph node status, distant metastasis, recurrence, disease-free survival, and overall survival). We also investigated the interrelationship of the expression of these proteins, as they have some common functions, with the aim of elucidating the role of these molecules in tumor development.

Section snippets

Materials and method

A cohort of 134 patients who had had primary invasive breast carcinoma treated by surgical resection were investigated. We had follow-up data for 98 of the patients and these 98 were included in the survival analysis. They constituted an unselected cohort of women with invasive early breast cancer and of a median age 55 (range 28-80) years, who had been diagnosed, treated, and followed up in the Ioannina University Hospital, between 1989 and 1998. Detailed clinical data were available for the

Hsp27expression

Hsp27expression (>10% of tumor cells immunoreactive) was observed in 63/99 (63.6%) of breast cancers (Fig. 1). Hsp27 expression was inversely correlated with tumor grade (P=0.006). In particular, statistically significant differences between grades 1 and 3 (P=0.02) and between grades 2 and 3 (P=0.0041) were observed (Table 2). Positive correlations of hsp27 expression with estrogen receptor (ER) (P=0.04) and with pS2 protein expression (P=0.015) were also found (Table 3, Table 4).

pS2 immunoreactivity

pS2

Discussion

Several proteins, such as hsp27, pS2, bcl-2, MT and cathepsin D have been reported to be correlated with hormonal status. In particular, hsp27 and pS2 are under active investigation as promising prognostic factors in breast cancer. Their value, either at protein level or at mRNA level, has been the subject of many studies with contradictory results. The most commonly used methods for measuring expression of these proteins are immunohistochemical staining on paraffin-embedded tumor sections and

Conclusion

In conclusion, the results of the present study confirm the hormone-dependent nature of hsp27 and pS2 proteins. In addition to their protective function in stressful (possibly hormonal) conditions, they might be involved in cell differentiation. Furthermore, pS2 seems to have a complex role in the process of apoptosis and in the control of growth and inactivation of the tumor suppressor gene. Further studies are necessary to confirm these observations. The interrelationship of the various

Acknowledgements

We offer our thanks to Mrs A. Christodoulou for technical assistance.

References (0)

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