Possible association between HPV16 E7 protein level and cytokeratin 19

Abstract

The mechanisms employed by human papillomaviruses (HPVs) to control the replication of the viral genome and the expression of the viral genes are extremely complex and further complicated by the fact that the viral life cycle is intricately tied to the differentiation program of its host epithelial tissue. Indeed, HPV-induced immortalization of keratinocytes and disruption of the normal cytokeratin (CK) expression pattern progress pari passu during the stepwise process that preludes to squamous cell carcinoma. A subset of HPVs, including type 16, are associated with squamous cervical and oropharyngeal carcinomas. 1-4 Two papillomaviral oncoproteins, E6 and E7, are likely to play a role in HPVassociated cancers. In particular, a number of data underline E7 oncogene implication. The E7 oncogene appears to redirect terminally differentiating epithelial cells to support viral DNA amplification, an important process in the generation of progeny virus. 5 In a recent study aimed to define the regulation of HPV16 E7 expression at the translational level, one of our labs described a molecular interaction occurring between HPV16 E7 mRNA and a 6-mer peptide having the amino acid sequence SEQIKA. It was demonstrated that the SEQIKA fragment binds to, prevents decay of and blocks translation of HPV16 E7 mRNA in in vitro experiments. The fragment was present in rabbit alpha 1-globin polypeptide, thus explaining the inefficient in vitro translation of E7 mRNA using rabbit reticulocyte cell free system. 6,7 Moreover, through similarity analysis it was demonstrated that the SEQIKA peptide is present in the human CK7 at the amino acid 91-96 position. The datum appeared of interest because of the specific CK7 localization in a large number of epithelial cell types including ductal and glandular epithelia, such as the squamo-columnar junction of the cervix, 8 -10 that is in areas where invasive squamous cell carcinomas arise. Finally, HPV16 E7 mRNA/CK7 interaction could also be demonstrated in the SiHa cancer cell line. 7 Here we extend these studies by comparatively analyzing the 2 HPV16-positive CaSki and SiHa cell lines.Indeed, a comparative analysis of CaSki and SiHa cells appeared suitable to further our understanding of the biologic function of HPV16 E7 mRNA/CK7 interaction and its role in HPV16 E7 oncoprotein expression for the following reasons. CaSki cells contain a high number of HPV16 DNA per cell, whereas the SiHa cell line contains 1 to 2 copies of HPV16 DNA per cell. Notwithstanding the striking difference in the number of HPV16 genome copies, it has been found that SiHa cells express more viral oncoprotein E7 per HPV16 genome harbored in the cell than CaSki cells. 11 Moreover, it has been established that although CaSki cells contain numerous copies of HPV16 genomes, the transcriptional activity of these genomes is relatively low and similar to that in SiHa cells. 12 Therefore, possibly different mechanisms are active at the translational level in the HPV16 E7 protein synthesis in SiHa and CaSki cells.As a first ste...

Detection of occult carcinomatous diffusion in lymph nodes from head and neck squamous cell carcinoma using real-time RT–PCR detection of cytokeratin 19 mRNA

“…Previous studies using such markers in HNSCC have suggested a low specificity (Kawamata et al, 1999;Hamakawa et al, 2000a), particularly because of false-positive results associated with benign epithelial rests in lymph nodes found in 1.6% of cervical nodes, but only in lymph nodes from level I (Gnepp, 2000;Hamakawa et al, 2000b). The assay used in the present study, that is, RT -PCR detection of CK19 mRNA, has been developed in our laboratory for the detection of occult carcinomatous cells in mediastinal lymph nodes in non-small-cell lung carcinoma (Saintigny et al, 2005) and by other teams in various carcinomas (Van Trappen et al, 2001;Inokuchi et al, 2003;Favia et al, 2004). The primers and probe for CK19 mRNA detection were designed to avoid the detection of the two known pseudogenes (Rund et al, 1999;Van Trappen et al, 2001;Saintigny et al, 2005) and we used real-time RT -PCR with the Taqman chemistry.…”

Cytokeratin7 expression in histologic and cytologic specimens of cystic neck metastasis from HPV positive squamous cell carcinoma of the tonsil: A case report

“…Although a growing number of studies have reported a close link between CK7 or CK19 and HPV positive OPSCC, little is known about the roles played by CK7 and CK19 in the pathogenesis of HPV‐related SCC . However, a few studies have analyzed interactions between HPV16 E7 mRNA and CK7 and CK19 in cervical cancer cell lines . In particular, in SiHa cells containing CK7/CK19, CK19 promotes HPV16 E7 oncoprotein expression by binding to the 6‐mer peptide SEQIKA of CK7, which interacts with E7 mRNA and inhibits E7 mRNA translation …”

“…7,8,10 However, a few studies have analyzed interactions between HPV16 E7 mRNA and CK7 and CK19 in cervical cancer cell lines. [11][12][13] In particular, in SiHa cells containing CK7/CK19, CK19 promotes HPV16 E7 oncoprotein expression by binding to the 6-mer peptide SEQIKA of CK7, which interacts with E7 mRNA and inhibits E7 mRNA translation. [11][12][13] Tonsillar and uterine cervical SCCs share some histopathological and immunohistochemical features.…”

“…[11][12][13] In particular, in SiHa cells containing CK7/CK19, CK19 promotes HPV16 E7 oncoprotein expression by binding to the 6-mer peptide SEQIKA of CK7, which interacts with E7 mRNA and inhibits E7 mRNA translation. [11][12][13] Tonsillar and uterine cervical SCCs share some histopathological and immunohistochemical features. They both arise in CK7 and CK19 positive squamocolumnar junctional cells infected by HR HPV and frequently accompany intratumoral cystic changes.…”

Deciphering the Multifactorial Susceptibility of Mucosal Junction Cells to HPV Infection and Related Carcinogenesis

“…Indeed, by interacting with a 6-mer amino acid peptide SEQIKA present at position 91–96 in the human Krt7 sequence, HPV E7 messenger RNA (mRNA) was shown to be protected/stabilized [39]. In addition, viral mRNA translation was presumed to be increased by Krt19 [40], another member of the keratin family overexpressed in both cervical and anal SC junctions [17,41]. Although these intriguing findings need to be confirmed, they support the hypothesis of a specific regulation of viral transcripts in SC junction cells leading to increased viral oncoprotein levels and, subsequently, to (pre)cancer development/progression.…”