Nestin expression in cutaneous melanomas and melanocytic nevi

Prognostic significance of melanoma differentiation and trans-differentiation

Cutaneous malignant melanomas share a number of molecular attributes such as limitless replicative potential that define capabilities acquired by most malignancies. Accordingly, much effort has been focused on evaluating and validating protein markers related to these capabilities to function as melanoma prognostic markers. However, a few studies have also highlighted the prognostic value of markers that define melanocytic differentiation and the plasticity of melanoma cells to trans-differentiate along several other cellular pathways. Here, we provide a comprehensive review and evaluation of the prognostic significance of melanocyte-lineage markers such as MITF and melanogenic proteins, as well as markers of vascular epithelial and neuronal differentiation.

Expression of the stem cell marker nestin in peripheral blood of patients with melanoma

BACKGROUND

There is continued interest in markers indicative of circulating melanoma cells. Nestin is a neuroepithelial intermediate filament protein that was found to be expressed in melanoma and in various cancer stem cells.

OBJECTIVES

We investigated expression of nestin in peripheral blood of patients with melanoma.

METHODS

We analysed nestin expression by flow cytometry and by quantitative reverse transcription-polymerase chain reaction both in tissues (n = 23) and in blood samples (n = 102) from patients with American Joint Committee on Cancer stage III-IV melanoma. Forty-six negative controls were also added.

RESULTS

Flow cytometry did not reveal nestin-expressing cells in peripheral blood of healthy volunteers. In patients with melanoma, however, nestin protein was expressed in a proportion of melanoma cells enriched from peripheral blood by immunomagnetic sorting. In melanoma tissue samples a significant correlation was found between mRNAs coding for nestin and tyrosinase (P = 0.001) and melan-A (P = 0.002), whereas in blood a significant correlation was observed only for tyrosinase (P = 0.015), but not for melan-A (P = 0.53). Nestin expression was higher in stage IV patients compared with stage III/IV with no evidence of disease, in patients with high tumour burden, and was positively correlated to expression of tyrosinase and melan-A.

CONCLUSIONS

Nestin was found to be an additional marker of interest for circulating melanoma cells. Prospective studies should investigate its potential added informative value in comparison with markers already in use for melanoma cell detection.

The nuclear matrix shell proteome of human epidermis

BACKGROUND

Proteomic approaches have identified cancer specific biomarker proteins in the nuclear matrix fraction of cancer cells. We wanted to determine whether a similar approach could be used to investigate melanoma biomarkers.

OBJECTIVE

Since it was not clear that a nuclear matrix fraction could be isolated from the intact human epidermis, we first wanted to determine whether a nuclear matrix fraction could be isolated from the intact epidermis of human skin. If this was possible, we secondarily wanted to compare the proteome of cultured melanoma and carcinoma cells to that of the intact epidermis.

METHODS

We applied two-dimensional electrophoresis (2DGE) and LC/MS/MS to identify proteins isolated in the nuclear matrix shell protein fraction isolated from the human epidermis and from cultured primary skin and cancer cells.

RESULTS

A subcellular fractionation of intact epidermis succeeded in yielding a nuclear matrix shell which made up approximately 40% of total tissue protein. Only 5-10% of total cell protein was fractionated in the nuclear matrix shell of cultured skin cells. The nuclear matrix shell of the intact epidermis was distinguishable from cultured keratinocytes or HaCaT cells by expression of keratin 1. The nuclear matrix of the epidermis was distinguishable from melanocytes and melanoma cells by expression of vimentin in melanocyte-derived cells and by expression of desmoplakin in the intact epidermis.

CONCLUSION

The nuclear matrix-intermediate filament system can be isolated from the intact human epidermis. A careful examination of the protein composition of this subcellular fraction from the epidermis and skin cancers may identify useful cancer specific biomarkers.

SOX9 and SOX10 but not BRN2 are required for nestin expression in human melanoma cells

Nestin is an intermediate filament protein and a marker of neuroectodermal stem cells indicating multipotentiality and regenerative capability. In melanoma tissues, nestin re-expression was correlated with tumor progression. Activation of the nestin neural enhancer was shown to be dependent on the binding of class III POU transcription factors, with brain-2 (BRN2) suggested to play a key role. We found both nestin and BRN2 mRNA in almost all of 13 analyzed melanoma cell lines of different progression stages, but expression levels did not correlate. Nestin protein was detected in 11 of 13 and BRN2 protein in 7 of 13 melanoma cell lines independent of progression stage. Downregulation of BRN2 by small-interfering RNA did not alter nestin expression in melanoma cells. However, POU proteins, such as BRN2, commonly cooperate with transcription factors of the Sry-box (SOX) family by binding to a nearby DNA site necessary for their action. SOX9 and SOX10 have been shown to be expressed in melanocyte precursors, with SOX10 downregulated upon differentiation. We now demonstrate SOX9 and SOX10 protein expression in melanoma tissues and cell lines. Downregulation of SOX9 and of SOX10 markedly decreased nestin levels in melanoma cells in a cooperative manner. Thus, SOX9 and SOX10 but not BRN2 seem to be required for nestin expression in human melanoma.

The prognostic value of nestin expression in newly diagnosed glioblastoma: report from the Radiation Therapy Oncology Group

Background

Nestin is an intermediate filament protein that has been implicated in early stages of neuronal lineage commitment. Based on the heterogeneous expression of nestin in GBM and its potential to serve as a marker for a dedifferentiated, and perhaps more aggressive phenotype, the Radiation Therapy Oncology Group (RTOG) sought to determine the prognostic value of nestin expression in newly diagnosed GBM patients treated on prior prospective RTOG clinical trials.

Methods

Tissue microarrays were prepared from 156 patients enrolled in these trials. These specimens were stained using a mouse monoclonal antibody specific for nestin and expression was measured by computerized quantitative image analysis using the Ariol SL-50 system. The parameters measured included both staining intensity and the relative area of expression within a specimen. This resulted into 3 categories: low, intermediate, and high nestin expression, which was then correlated with clinical outcome.

Results

A total of 153 of the 156 samples were evaluable for this study. There were no statistically significant differences between pretreatment patient characteristics and nestin expression. There was no statistically significant difference in either overall survival or progression-free survival (PFS) demonstrated, although a trend in decreased PFS was observed with high nestin expression (p = 0.06).

Conclusion

Although the correlation of nestin expression and histologic grade in glioma is of considerable interest, the presented data does not support its prognostic value in newly diagnosed GBM. Further studies evaluating nestin expression may be more informative when studied in lower grade glioma, in the context of markers more specific to tumor stem cells, and using more recent specimens from patients treated with temozolomide in conjunction with radiation.