Immunohistochemical Analysis of pH-Sensitive TRPV5 in Common Skin Tumors.

Transient receptor potential vanilloid 5 (TRPV5) is a calcium- and pH-sensitive ion channel. It plays a role in tumor biology and cellular calcium homeostasis. Due to the inverse pH gradient in solid tumors (extracellular acidosis and increased intracellular pH), TRPV5 is interesting as a signaling molecule in tumors, as the altered pH in the tumor microenvironment (TME) impacts tumor growth and metastasis. This is the first study to analyze the expression of TRPV5 in common skin cancers, i.e., basal cell carcinomas (BCC), squamous cell carcinomas (SCC), malignant melanomas (MM) and melanocytic nevi (MCN). The results showed a significantly lower expression of TRPV5 in BCC than in all other tumor entities analyzed. While less than half of the BCC were positive for TRPV5, SCC, MM, and MCN exhibited a high level of positive staining results. These results suggest that TRPV5 may especially help as a novel marker in the differentiation of SCC from BCC. The low expression of TRPV5 in BCC, a rarely metastatic tumor, may also point to a role of TRPV5 in the progression of epithelial skin tumors. Further functional studies, however, are needed to clarify the exact role of TRPV5 in skin tumors.