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Open Access Research

Low RBM3 protein expression correlates with tumour progression and poor prognosis in malignant melanoma: An analysis of 215 cases from the Malmö Diet and Cancer Study

Liv Jonsson1, Julia Bergman1, Björn Nodin1, Jonas Manjer23, Fredrik Pontén4, Mathias Uhlén56 and Karin Jirström1*

Author Affiliations

1 Department of Clinical Sciences, Pathology, Lund University, Skåne University Hospital, 221 85 Lund, Sweden

2 Department Clinical Sciences, Surgery, Lund University, Skåne University Hospital, 205 02 Malmö, Sweden

3 The Malmö Diet and Cancer Study, Lund University, 205 02 Malmö, Sweden

4 Department of Genetics and Pathology, Rudbeck Laboratory, Uppsala University, 251 87 Uppsala, Sweden

5 Department of Proteomics, AlbaNova University Center, Royal Institute of Technology, 106 91 Stockholm, Sweden

6 Science for Life Laboratory, Royal Institute of Technology, 106 91 Stockholm, Sweden

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Journal of Translational Medicine 2011, 9:114  doi:10.1186/1479-5876-9-114

Published: 21 July 2011

Abstract

Background

We have previously reported that expression of the RNA- and DNA-binding protein RBM3 is associated with a good prognosis in breast cancer and ovarian cancer. In this study, the prognostic value of immunohistochemical RBM3 expression was assessed in incident cases of malignant melanoma from a prospective population-based cohort study.

Methods

Until Dec 31st 2008, 264 incident cases of primary invasive melanoma had been registered in the Malmö Diet and Cancer Study. Histopathological and clinical information was obtained for available cases and tissue microarrays (TMAs) constructed from 226 (85.6%) suitable paraffin-embedded tumours and 31 metastases. RBM3 expression was analysed by immunohistochemistry on the TMAs and a subset of full-face sections. Chi-square and Mann-Whitney U tests were used for comparison of RBM3 expression and relevant clinicopathological characteristics. Kaplan Meier analysis and Cox proportional hazards modelling were used to assess the relationship between RBM3 and recurrence free survival (RFS) and overall survival (OS).

Results

RBM3 could be assessed in 215/226 (95.1%) of primary tumours and all metastases. Longitudinal analysis revealed that 16/31 (51.6%) of metastases lacked RBM3 expression, in contrast to the primary tumours in which RBM3 was absent in 3/215 (1.4%) cases and strongly expressed in 120/215 (55.8%) cases. Strong nuclear RBM3 expression in the primary tumour was significantly associated with favourable clinicopathological parameters; i.e. non-ulcerated tumours, lower depth of invasion, lower Clark level, less advanced clinical stage, low mitotic activity and non-nodular histological type, and a prolonged RFS (RR = 0.50; 95% CI = 0.27-0.91) and OS (RR = 0.36, 95%CI = 0.20-0.64). Multivariate analysis demonstrated that the beneficial prognostic value of RBM3 remained significant for OS (RR = 0.33; 95%CI = 0.18-0.61).

Conclusions

In line with previous in vitro data, we here show that RBM3 is down-regulated in metastatic melanoma and high nuclear RBM3 expression in the primary tumour is an independent marker of a prolonged OS. The potential utility of RBM3 in treatment stratification of patients with melanoma should be pursued in future studies.