Abstract
BackgroundThe role of human papillomavirus (HPV) in bladder carcinogenesis remains controversial. Overexpression of p16INK4a, a surrogate marker for infection with oncogenic HPV in other tumours, has been described for urothelial carcinoma in situ (UCIS). Our goal was therefore to evaluate whether overexpression of p16INK4a is associated with HPV infection and to identify mechanisms of p16INK4a upregulation in UCIS.Materials and MethodsIn 60 tissue specimens from a total of 45 patients (UCIS and controls), we performed p16INK4a immunohistochemistry followed by detection and subclassification of HPV DNA. In a subset of samples, we tested for gene amplification of p16INK4a applying fluorescence in situ hybridization (FISH). RAS/MAPK signalling and epithelial-mesenchymal transition (EMT) was assessed using immunohistochemistry. Finally, we transfected urothelial carcinoma cells with KRAS and examined the expression of p16INK4a as well as markers of EMT.ResultsWe found overexpression of p16INK4a in 92.6% of UCIS and in all cervical intraepithelial neoplasia (CIN) controls. In contrast, we detected high-risk HPV DNA in 80% of CIN, but none in UCIS. There was no gene amplification of p16INK4a. High levels of phosphorylated kinases and urokinase plasminogen activator (uPA) and loss of membraneous E-cadherin were detected in UCIS. KRAS transfection of urothelial carcinoma cells led to upregulation of p16INK4a and uPA accompanied by loss of E-cadherin that could be inhibited by application of the kinase-inhibitor Sorafenib.ConclusionsOur results show that overexpression of p16INK4a in UCIS is neither associated with HPV infection nor p16INK4a gene amplification but is a consequence of enhanced RAS/MAPK signalling that promotes EMT, possibly due to Sorafenib-sensitive paracrine secretion of the EMT activator uPA. These findings might open a novel therapeutic option for localized but aggressive urothelial cancer.
Highlights
Urothelial bladder cancer is the 7th most common cancer in men and the 17th most common cancer in women worldwide[1]
KRAS transfection of urothelial carcinoma cells led to upregulation of p16INK4a and urokinase plasminogen activator (uPA) accompanied by loss of E-cadherin that could be inhibited by application of the kinase-inhibitor Sorafenib
Our results show that overexpression of p16INK4a in urothelial carcinoma in situ (UCIS) is neither associated with human papillomavirus (HPV) infection nor p16INK4a gene amplification but is a consequence of enhanced RAS/MAPK signalling that promotes epithelial-mesenchymal transition (EMT), possibly due to Sorafenibsensitive paracrine secretion of the EMT activator uPA
Summary
Urothelial bladder cancer is the 7th most common cancer in men and the 17th most common cancer in women worldwide[1]. It has been shown that UCIS lesions can be induced by exposure to the carcinogene nitrosamine and that they progress to invasive carcinomas upon STAT3 activation, P53 mutations and loss of heterozygosity of chromosome 9[3,4]. It has further been shown that UCIS lesions already express molecular markers that conform to epithelial-mesenchymal transition (EMT) of the tumour cells and are regarded as a prerequisite for invasion and metastasis[5]. Reactive urothelial atypia (UA) and UCIS share common characteristics, such as loss of nuclear stratification and an increase in mitotic activity[8]. Overexpression of p16INK4a, a surrogate marker for infection with oncogenic HPV in other tumours, has been described for urothelial carcinoma in situ (UCIS). Our goal was to evaluate whether overexpression of p16INK4a is associated with HPV infection and to identify mechanisms of p16INK4a upregulation in UCIS
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
