P2X5 and P2X7 receptors in human warts and CIN-612 organotypic raft cultures of human papillomavirus infected keratinocytes

Purinergic receptors, which bind adenosine 5′-triphosphate (ATP), are expressed on human cutaneous keratinocytes and in squamous cell carcinomas. Studies on normal human epidermis and primary keratinocyte cultures have suggested that P2X₅ receptors are likely to be involved in keratinocyte differentiation and P2X₇ receptors are likely to be part of the machinery of end stage terminal differentiation/apoptosis of keratinocytes. P2X₇ receptor agonists can significantly reduce primary keratinocyte cell numbers in culture. Human papillomaviruses are increasingly recognised as important human carcinogens in the development of non-melanoma skin cancers. In our study, immunohistochemical analysis for P2X₅ and P2X₇ receptors was performed on paraffin sections of normal human skin, warts, raft cultures of normal human keratinocytes and raft cultures of CIN 612 cells, a model of keratinocytes infected with human papillomavirus type 31. In warts there was up-regulation of the expression of P2X₅ receptors. A similar pattern was seen in the CIN 612 raft cultures. Both P2X₅ and P2X₇ receptors were found in the nuclei of koilocytes, abnormal keratinocytes characteristic of human papillomavirus infection. P2X₅ and P2X₇ receptors may provide a new focus for therapeutic research into treatments for warts because these receptors can induce cell differentiation and cell death.An erratum to this article can be found at