Elsevier

Pathology

Volume 48, Issue 7, December 2016, Pages 660-665
Pathology

Anatomical pathology
Calretinin but not caveolin-1 correlates with tumour histology and survival in malignant mesothelioma

https://doi.org/10.1016/j.pathol.2016.08.003Get rights and content

Summary

Malignant mesothelioma (MM) continues to be a disease with poor prognosis and limited treatment options. Calretinin and caveolin-1 expression by tumour in MM have recently been described to be associated with tumour histology, differentiation and consequently survival. In a large, well annotated cohort, we studied both of these biomarkers and explored their association with clinicopathological parameters and survival.

A retrospective search of patients with MM who underwent surgery at the Austin Hospital in Melbourne, Australia, was conducted. Clinical history and outcome data were retrieved from patient records. Tissue microarrays (TMAs) were constructed and stained for calretinin and caveolin-1. ‘H scores’ were derived, taking intensity and distribution of staining, and the cohort was dichotomised using median values for both markers.

In the 329 patients evaluated, median age was 67 years. Males outnumbered females by 5:1. Epithelioid histology 202/319 (62.9%) was the most common, followed by biphasic 72/319 (21.8%) and sarcomatoid 45/319 (13.6%); histology could not be confirmed in 10 patients. Calretinin expression was detected in 246 of the 324 (76%) evaluable patients and high expression was associated with epithelioid histology (p < 0.0001). Caveolin-1 was expressed in 298 (94%) of 317 evaluable patients which was much higher compared to its expression in a cohort of lung adenocarcinomas (8/58, 13.7%). However, no association with histology was found (p = 0.409). When taken as a continuous variable, calretinin expression was found to be an independent predictor of survival, alongside histology, neutrophil-lymphocyte ratio, weight loss and stage. No prognostic value was demonstrable for caveolin-1 expression and calretinin/caveolin-1 ratio. There was no relationship between calretinin and caveolin-1 expression.

In MM, increased calretinin expression is associated with epithelioid histology and better survival. Caveolin-1 is a sensitive MM marker and is expressed in a high proportion of cases but lacks association with histology and survival.

Introduction

Despite the ban of asbestos use in most industrialised countries, the incidence of malignant mesothelioma (MM) is set to rise in the coming decades.1, 2 The World Health Organization (WHO) mortality database between 1994 and 2008 reported an age-adjusted mortality rate for MM of 4.9 per million.3 Despite the development of aggressive multi-modality treatment, the mainstay of current paradigms remains pemetrexed and cisplatin, based on the results of the EMPHACIS (Evaluation of Mesothelioma in a Phase III Trial of Pemetrexed with Cisplatin) study.4, 5 However, the MAPS study (Mesothelioma Avastin Cisplatin Pemetrexed study) has recently suggested that the addition of bevacizumab further improves overall survival.6, 7

The use of a panel of immunohistochemistry (IHC) markers is now routine in MM diagnosis. However, the differentiation of MM from other malignancies metastasising to the pleura remains problematic despite the use of several well known mesothelioma markers. Calretinin, which is a calcium binding protein, has been established as a useful marker in distinguishing MM from adenocarcinomas with pleural metastases.8 However, its expression is also observed in 15% of adenocarcinomas of breast origin9 and 4–18% of pulmonary adenocarcinomas.10, 11, 12 Caveolin-1, one of a three-member caveolin protein family, is a membrane-associated protein possibly involved in integrin signalling and in cell migration. It is expressed in endothelial and mesothelial cells as well as in alveolar type I pneumocytes.12 Caveolin-1 has been purported to play a dual and opposite role in tumorigenesis, as it has been implicated in both tumour suppression and oncogenesis. In human cancers, caveolin-1 is a marker of extracellular matrix remodelling13 and epithelial to mesenchymal transition.14 It has been associated with aggressive biology and resistance to apoptotic signals in several malignancies.15, 16, 17 Caveolin-1 has also been described as a marker of dedifferentiation in soft tissue and bone sarcomas.18, 19 It has also been projected as a novel marker for MM. In a study comparing its expression in 80 epithelioid MMs and 80 lung adenocarcinomas, a 100% sensitivity and 93% specificity for caveolin-1 in epithelioid MMs was reported.12

Besides their importance in MM diagnosis, both of these IHC markers have also been studied for their association with tumour differentiation, histology and prognosis. Takeshima et al. found that higher calretinin scores were seen in more well differentiated tumours, which in turn have more favourable prognosis.20 The prognostic role of calretinin expression has also been explored by Kao et al., who demonstrated low expression of calretinin to be poorly prognostic in two different patient cohorts.21, 22, 23 They also reported calretinin expression in 828/910 (91%) of all MMs; with 530/545 (97%) of epithelioid and 113/119 (94%) of biphasic but only 92/153 (60%) of sarcomatoid MMs.23 In a series of 131 MM patients, Righi et al. found higher rates of caveolin-1 expression amongst non-epithelioid MM (40/40, 100%) as compared to epithelioid MM (70/91, 77%) and suggested that its expression increases with dedifferentiation from low grade epithelioid to high grade sarcomatoid histology.24 The same authors also described a poorer outcome for epithelioid MMs in which caveolin-1 expression was detected in stromal cells.

Emerging literature suggests caveolin-1 is a sensitive IHC based diagnostic marker for MM, especially the sarcomatoid subtype, although its specificity is still questionable given its expression in other mesenchymal cells such as endothelial and smooth muscle cells. Using a large cohort of well annotated confirmed MM patients, we studied and compared the expression of these two IHC markers. We also sought to determine if their expression correlated with each other, and with clinico-pathological parameters and survival.

Section snippets

Materials and methods

A retrospective search of the thoracic surgery database of the Austin Hospital in Melbourne, Australia, was carried out for patients who underwent surgery (diagnostic/therapeutic/palliative) for MM between 1988 and 2014. Clinical information on patient demographics, co-morbidities, treatments, follow-up and outcome was retrieved from patient medical records. Archival formalin fixed, paraffin embedded (FFPE) blocks chosen after a review of the original histopathology reports were retrieved from

Results

Of the 373 patients who underwent surgical procedures for MM between 1988 and 2014, adequate clinical and outcome data were available for 359. A further 30 patients were excluded for various reasons, including lack of adequate archival FFPE tissue blocks and inability to conclusively prove MM despite using a panel of IHC markers. The TMA was constructed from the FFPE tissues of 329 patients with confirmed MM.

In this cohort, males outnumbered females by more than 5:1. The age at presentation

Discussion

In this large cohort of patients with MM, we investigated two markers which are purported to be closely associated with tumour differentiation. We investigated their expression and association with clinicopathological parameters including tumour histology and OS. Positivity with caveolin-1 was found to be higher than calretinin in the entire cohort. Previous findings of a statistically significant association of calretinin expression with epithelioid histology and also survival were

Conflicts of interest and sources of funding

This study was supported by the Mesothelioma grant awarded by Cancer Council Victoria and Victorian Cancer Agency and in part by funds from the Operational Infrastructure Support Program provided by the Victorian Government, Australia. TJ is recipient of a NHMRC Early Career Fellowship (APP1074035) and BT is supported by an Australian Postgraduate Award post-graduate scholarship. The authors state there are no conflicts of interest to disclose.

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