Gene Profiling of Cottontail Rabbit Papillomavirus-Induced Carcinomas Identifies Upregulated Genes Directly Involved in Stroma Invasion as Shown by Small Interfering RNA-Mediated Gene Silencing

Abstract

While high-risk human papillomaviruses (HPVs) have been identified as necessary risk factors for the development of cervical cancer (7), the role of HPV in skin cancer, which is the most common cancer in Caucasians, is still undefined (3, 23). A first link between papillomaviruses and skin cancer was obtained in 1935 from an animal model system, when Rous and Beard (40) described the development of squamous cell carcinomas (SCCs) in rabbits after experimental infection with cottontail rabbit papillomavirus (CRPV). Initial benign warts develop into invasively growing SCCs without any further cocarcinogens within 6 to12 months in the vast majority of the animals (50). A similar situation has been described for humans, where in the rare genetic disorder epidermodysplasia verruciformis, patients develop flat HPV-induced warts which progress in up to 60% of the cases into mostly primary SCCs (36, 37). Skin cancer has also been recognized as a common side effect in long-term-immunosuppressed patients, who have a 65-fold-increased risk for this disease. Shortly after the onset of immunosuppressive therapy, HPV-induced warts develop, and after 20 years of immunosuppression, nonmelanocytic skin cancer can be found in up to 70% of the patients (8). As in the case of epidermodysplasia verruciformis patients, the lesions seem to progress from warts through dysplastic lesions into SCC (4,16,43). Although HPV-associated SCCs have been found in 65% (43) or 81% (4) of the cases, the mechanisms leading to the development of skin cancer and especially the role of papillomaviruses are not yet fully understood.Thus far, the only model system for studying the progression of papillomavirus-induced skin tumors is the domestic rabbit infected with CRPV. Infection of domestic rabbits with CRPV particles or viral DNA leads to the development of local tumors within 3 to 6 weeks postinfection. These papillomas progress within 6 to 12 months in more than 80% of the cases into invasively growing and finally metastasizing carcinomas (45; S. Jeckel, unpublished data). Only in very few individual rabbits do papillomas persist in the benign state, and even fewer regress. This progressive behavior does not depend on any other known cofactor besides the viral infection, which makes CRPV an important model for papillomavirus-associated skin disorders in order to study the role of viral and cellular gene expression during cancer development.Earlier studies using more descriptive methods, such as RNA-RNA in situ hybridization, showed no pronounced qualitative or quantitative changes in viral gene expression during malignant progression (50). The primary target cells localized in the bulge region of hair follicles already revealed rather high expression of E6 and E7 mRNAs (42), which remains a constant feature from papillomas through carcinomas to lung metastases (50, 52). Therefore it seems most likely that alterations

Papillomavirus E2 Protein Induces Expression of the Matrix Metalloproteinase-9 via the Extracellular Signal-Regulated Kinase/Activator Protein-1 Signaling Pathway

“…1) between WT E2, mutant R37K, and mutant I73A, suggesting that changes in the cellular gene expression that maybe caused by WT E2 and the mutant R37K but not by the I73A mutant could play a role in the tumorigenesis caused by CRPV. Indeed, in earlier gene expression profiling studies with CRPV-infected New Zealand White rabbits, we showed that during tumor progression several cellular genes involved in tumor invasion and cell motility become up-regulated (14). To identify the molecular basis for the different tumorigenic activity of the E2 transactivation domain mutants, we looked for differences between skin tumors induced by CRPV WT genome or by mutant genomes.…”

“…Most of the mutant E2 proteins had lost their ability to transactivate artificial promoters with multiple E2-binding sites, but all maintained their DNA-binding and replication capacities (13). On the cellular level, we identified tumor-promoting candidate genes by comparing the gene expression profiles of benign versus malignant rabbit skin tumors, which revealed proteins involved in cell motility, tumor invasion, and metastasis that are up-regulated in the process of CRVP-induced cancer progression (14). The transition from benign to invasive tumors is most likely not only dependent on the neoplastic cells themselves but also strongly affected by the interaction of neoplastic cells with their extracellular matrix (15).…”

Regulating cell migration: calpains make the cut

“…Calpain activity appears to play a central role in the movement of immune cells (Lokuta et al, 2003;Stewart et al, 1998), thereby participating in the development of inflammation in normal and pathological conditions such as chronic inflammatory disease (Cuzzocrea et al, 2000;. Furthermore, calpain 2 expression is upregulated in some cancers and has recently been associated with disease progression in patients with breast cancer (Rios-Doria et al, 2003;Wang et al, 2005;Carragher et al, 2004;Huber et al, 2004). The coordinate regulation of adhesion structures by calpains and Src tyrosine kinases places calpains in a crucial role at the interface of kinase and protease cascades that regulate migration of tumor cells and their invasive properties (Carragher et al, 2001;Carragher and Frame, 2002;Carragher et al, 2002;Mamoune et al, 2003).…”

Targeting 14-3-3zeta in cancer therapy

“…41 Moreover, 14-3-3zeta shows a constant upregulation of the transcripts in a cottontail rabbit papillomavirus squamous carcinoma model employing New Zealand 14-3-3zeta in cancer X Yang et al White rabbits. 42 A web-based meta-analysis (Oncomine) reveals 14-3-3zeta overexpression in various types of carcinomas, 41 suggesting its oncogene property. Based on these evidences, we suggest that 14-3-3zeta is a candidate proto-oncogene and deserves further investigation into its role in carcinogenesis.…”