Abnormal desmoglein expression by squamous cell carcinoma cells

Abnormal expression of cell adhesion molecules and related proteins has been observed in various carcinoma cells. We compared expression patterns of desmosomal cadherins, E-cadherin, and cytoplasmic plaque proteins of four different human squamous cell carcinoma cell lines and in vivo squamous cell carcinoma cells with those of normal human keratinocytes. Unlike normal human keratinocytes, the squamous cell carcinoma cells, both in culture and in vivo, exhibited diminished or unusual expression of desmoglein 3 and desmoglein 1, which bear pemphigus vulgaris and pemphigus foliaceus antigens, respectively. Abnormal expression of E-cadherin and cytoplasmic plaque proteins such as desmoplakin and plakoglobin was also observed. Western blotting study demonstrated that three squamous cell carcinoma cell lines expressed two desmogleins with a predominant 150 kDa molecule, and a minor 130 kDa one. Although these molecular sizes were similar to those of cultured normal human keratinocytes, the 130 kDa desmoglein, which usually carries pemphigus antigenic epitopes, was weakly or negatively reactive with pemphigus vulgaris serum. One squamous cell carcinoma cell line showed a doublet of 140 and 145 kDa bands in addition to the 130 kDa band. All the carcinoma cell lines constantly expressed desmoglein 2 and desmoglein 3 mRNA, whereas cultured normal human keratinocytes always expressed desmoglein 1 and desmoglein 3 mRNA, with or without desmoglein 2 mRNA. These findings indicate that the squamous cell carcinoma cells revealed abnormal expression of desmoglein isoforms, which may be related to tumour cell kinetics such as cell invasion and metastasis.