Intercellular junctions in Ewing sarcoma/primitive neuroectodermal tumor: additional evidence of epithelial...

Area of Science:

• Oncology
• Cell Biology
• Molecular Pathology

Background:

• Ewing sarcoma/primitive neuroectodermal tumor (ES/PNET) exhibits cytokeratin expression, suggesting partial epithelial differentiation.
• Previous studies noted primitive cell-cell junctions resembling desmosomes in ES/PNET.
• Recent advancements provide antibodies for intercellular junction proteins.

Purpose of the Study:

• To investigate the expression of intercellular junction proteins in genetically confirmed ES/PNET.
• To determine the presence and type of epithelial differentiation markers in ES/PNET.

Main Methods:

• Immunohistochemical staining of formalin-fixed, paraffin-embedded ES/PNET specimens (n=30).
• Antibodies used: claudin-1, occludin, ZO-1 (tight junctions); desmoglein, desmoplakin (desmosomes); E-cadherin (adherens junctions).
• Scoring based on >5% positive cells; normal colonic epithelium and skin as positive controls.

Main Results:

• Claudin-1 expressed in 63% (19/30) and ZO-1 in 51% (15/29) of ES/PNET.
• Occludin expression was low (11%, 3/28).
• Tight junction markers were present in 54% (one marker) and 36% (two markers), but never all three. Desmosomal and adherens junction proteins were rare to absent.

Conclusions:

• ES/PNET frequently exhibits poorly formed tight junctions, indicated by claudin-1 and ZO-1 expression.
• The absence of occludin suggests abnormal tight junction formation.
• Findings support the hypothesis of frequent partial epithelial differentiation in ES/PNET.