HPV16 E6 and E7 upregulate the histone lysine demethylase KDM2B through the c-MYC/miR-146a-5p axys

Abstract

Persistent infection by high-risk human papillomaviruses (HPVs) is associated with the development of cervical cancer and a subset of anogenital and head and neck squamous cell carcinomas. Abnormal expression of cellular microRNAs (miRNAs) plays an important role in the development of cancer, including HPV-related tumors. In this study, we demonstrated that miR-146a-5p was down-regulated by E6 and, less efficiently, by E7 of high-risk HPV16 in keratinocytes and the presence of low levels of this miRNA in cervical carcinoma cell lines and in high-risk HPV-positive cervical specimens. Down-regulation of miR-146a-5p was mediated at least in part by the transcription repressor c-MYC, through binding sites in the miR-146a promoter. Overexpression of miR-146a-5p significantly inhibited proliferation and migration of keratinocytes and cervical cancer cells. The histone demethylase KDM2B was validated as a new direct target of miR-146a-5p and two putative binding sites for miR-146a-5p were identified in its 3'UTR sequence. Western blot analysis and immunohistochemistry showed that KDM2B was overexpressed in HPV16 E6/E7-positive keratinocytes, in cervical cancer cell lines, and in a subset of invasive cervical carcinomas and HPV-positive laryngeal squamous cell carcinomas. In these tumors, KDM2B overexpression was associated with c-MYC copy number gain. In vitro, silencing of KDM2B inhibited proliferation of cervical cancer cells. In conclusion, this study identified a novel player, the hystone demethylase KDM2B, in HPV-mediated tumorigenesis. E6 and, less efficiently, E7 of high-risk HPV16 up-regulated KDM2B expression in human keratinocytes through a pathway involving overexpression of c-MYC, which in turn downregulated miR-146a-5p.

The role of miR‐146a in viral infection

“…Also, upregulation of miR‐146a‐5p in cervical carcinoma cell lines and HFKs leads to inhibit the capacity of migration and cell proliferation. Furthermore, they showed that HPV‐16 E6 and E7 proteins are likely to inhibit miR‐146a‐5p through c‐MYC, because c‐MYC has the ability to bind to miR‐146a promoter . The E6 and E7 oncoproteins suppress miR‐146a‐5p, however, tumor virus oncoproteins, such as KSHV‐encoded vFLIP K13, EBV‐LMP1 oncoprotein, and HTLV‐1 Tax protein induce miR‐146a‐5p expression by NF‐κB .…”

“…Upregulation of miR‐146a‐5p for these viruses seems to have suppressor effects on cellular antiviral responses and virus replication, and probably display the host‐defense system against malignant transformation. However, forced expression of this miRNA in HPV‐positive cervical cancer cell lines and in human keratinocytes inhibits cell migration and proliferation …”

“…They showed that this miRNA directly targets the KDM2B transcript, and KDM2B is upregulated in the cervical cancer cell and in keratinocytes transduced with HPV16 E6. Moreover, high‐risk HPV oncoproteins E6 and, less efficiently, E7 increase KDM2B expression through a pathway involving upregulation of c‐MYC, which in turn declines miR‐146a‐5p expression …”

“…They found a significant negative correlation between EGFR expression and miR-146a-5p levels in penile SCCs, and they showed that miR-146a upregulation leads to suppress HeLa and HFKs cells proliferation. 65 In another study by this group, 66 miR-146a-5p was explored in HPV-related cancer and observed that although the E6 proteins of HPV-16 (high risk) suppresses the miR-146a-5p expression in primary oral keratinocytes and in HFKs, HPV6 E6 (low risk) does not have this function. Also, upregulation of miR-146a-5p in cervical carcinoma cell lines and HFKs leads to inhibit the capacity of migration and cell proliferation.…”

Loss of miR-143 and miR-145 in condyloma acuminatum promotes cellular proliferation and inhibits apoptosis by targeting NRAS

“…As early as 2012, a set of HPV core miRNAs, including the miR-15a/miR-16/miR-195/miR-497 family, miR-143/miR-145 and miR-106-363 clusters, were identified in HPV + HNSCC, which were more similar to HPV + cervical SCC (CSCC) than to HPV - HNSCC [20]. Both high-risk HPV (hrHPV) E6 and E7 oncoproteins can influence expression of cellular miRNAs through their effects on transcription factors, such as p53, c-Myc and E2F [11,26,27]. Recently, HPV16 E6 has been shown to suppress miR-23b expression in CSCC through DNA methylation of the host gene C9orf3 [28].…”