p53 immunohistochemical expression in early posttransplant-associated malignant and premalignant cutaneous lesions

Human papillomavirus infection and skin cancer risk in organ transplant recipients

Warts and squamous cell carcinomas are important cutaneous complications in organ transplant recipients. The role of infection with human papillomaviruses (HPV) in the development of cutaneous squamous cell carcinoma is still unclear. An extremely diverse group of HPV types, mainly consisting of epidermodysplasia-verruciformis (EV)-associated HPV types, can be detected in benign, premalignant, and malignant skin lesions of organ transplant recipients. Frequently, there are multiple HPV types present in single skin biopsies. Typically, the prevalence of viral warts rises steadily after transplantation and a strong association exists between the number of HPV-induced warts and the development of skin cancer. The interval between the transplantation to the development of warts is clearly shorter than the interval from transplantation to the diagnosis of the first skin cancer. A comparison of transplant recipients with and without skin cancer, however, showed an equally high prevalence of EV-HPV DNA in keratotic skin lesions in both groups of patients and the detection rate and spectrum of HPV infection in hyperkeratotic papillomas, actinic keratoses, and squamous cell carcinomas was also similar. HPV DNA can frequently be detected in patients with hyperproliferative disorders like psoriasis and antibodies against HPV in patients with regenerating skin (e.g., after extensive second degree burns). Latent infection with EV-HPV seems to be widespread. The hair follicle region might be the reservoir of EV-HPV. The E6 protein from a range of cutaneous HPV types effectively inhibits apoptosis in response to UV-light induced damage. It is therefore conceivable that individuals who are infected by EV-HPV are at an increased risk of developing actinic keratoses and squamous cell carcinomas, possibly by chronically preventing UV-light induced apoptosis.

Altered p53 expression in benign and malignant skin lesions from renal transplant recipients and immunocompetent patients with skin cancer: correlation with human papillomaviruses?

Renal transplant recipients are prone to numerous benign and malignant skin lesions. Previous work in the authors' laboratory has determined that the human papillomavirus may be the viral aetiology of these skin lesions. The p53 tumor-suppressor gene is the most frequently mutated gene in a wide range of human cancers. Here the authors describe an immunohistochemical study to evaluate the expression of p53 in benign and malignant skin lesions from renal transplant recipients and immunocompetent patients with skin cancer. The effect of p53 mutations on the expression patterns observed were examined by polymerase chain reaction-single strand conformation polymorphism analysis and direct cycle sequencing. The expression of the p53-regulated cyclin-dependant kinase inhibitor p21Waf1/Cip1 and Mdm2 was also examined in p53-positive cells. The expression of p53 in benign and malignant lesions was found to be markedly different. p53 was expressed in only 40% (6/15) of viral warts analyzed. The expression was confined to the basal layer both in the lesion and in adjacent normal skin, and the level of expression was low and only in a small number of cells (<10%). Of the cutaneous squamous cell carcinomas analyzed, 60% (9/15) showed p53 expression. Two different patterns of expression were observed. Basal layer expression in both the invasive tumor and adjacent normal skin was observed in 50% of the p53-positive squamous cell carcinomas; in the remaining 50%, p53 was expressed diffusely throughout the invasive tumor and in the basal layer of adjacent normal skin. The level of expression was high and in a large number of cells. Polymerase chain reaction-single strand conformation polymorphism analysis revealed that only one of the squamous cell carcinomas expressing p53 harbored a p53 mutation and that the accumulated p53 in the remaining tumors was wild type. No Mdm2 or p21Waf1/Cip1 expression was detected in the p53-positive squamous cell carcinomas, indicating that although the accumulated p53 is stable, it does not function effectively as a transcriptional activator. This represents a novel p53 phenotype in cutaneous squamous cell carcinoma. In addition, no correlation was seen between the presence and absence of human papillomavirus and p53 expression.