Apicidin down-regulates human papillomavirus type 16 E6 and E7 transcripts and proteins in SiHa cervical cancer cells

Recombinant adenoviruses expressing HPV16/18 E7 upregulate the HDAC6 and DNMT3B genes in C33A cells

Objective

High-risk human papillomavirus (HPV) is a carcinogenic virus associated with nearly all cases of cervical cancer, as well as an increasing number of anal and oral cancers. The two carcinogenic proteins of HPV, E6 and E7, can immortalize keratinocytes and are essential for HPV-related cellular transformation. Currently, the global regulatory effects of these oncogenic proteins on the host proteome are not fully understood, and further exploration of the functions and carcinogenic mechanisms of E6 and E7 proteins is needed.

Methods

We used a previously established platform in our laboratory for constructing recombinant adenoviral plasmids expressing the HPV16 E7 gene to further construct recombinant virus particles expressing HPV16/18 E6, E7, and both E6 and E7 genes. These recombinant viruses were used to infect C33A cells to achieve sustained expression of the HPV16/18 E6/E7 genes. Subsequently, total RNA was extracted and RNA-Seq technology was employed for transcriptome sequencing to identify differentially expressed genes associated with HPV infection in cervical cancer.

Results

RNA-Seq analysis revealed that overexpression of the HPV16/18 E6/E7 genes upregulated GP6, CD36, HDAC6, ESPL1, and DNMT3B among the differentially expressed genes (DEGs) associated with cervical cancer. Spearman correlation analysis revealed a statistically significant correlation between the HDAC6 and DNMT3B genes and key pathways, including DNA replication, tumor proliferation signature, G2M checkpoint, p53 pathways, and PI3K/AKT/mTOR signaling pathways. Further, qRT-PCR and Western blot analyses indicated that both HPV16/18 E7 can upregulate the expression of HDAC6 and DNMT3B, genes associated with HPV infection-related cervical cancer.

Conclusion

The successful expression of HPV16/18 E6/E7 in cells indicates that the recombinant viruses retain the replication and infection capabilities of Ad4. Furthermore, the recombinant viruses expressing HPV16/18 E7 can upregulate the HDAC6 and DNMT3B genes involved in cervical cancer pathways, thereby influencing the cell cycle. Additionally, HDAC6 and DNMT3B are emerging as important therapeutic targets for cancer. This study lays the foundation for further exploration of the oncogenic mechanisms of HPV E6/E7 and may provide new directions for the treatment of HPV-related cancers.

Small Molecule Inhibitors of Human Papillomavirus: A Review of Research from 1997 to 2021

Human papillomavirus (HPV) infections are the cause of warts, lesions and cancer, with different types of HPV causing different symptoms. HPV infections are the primary cause of cervical cancer. There are over 220 different types of HPV, and only nine of these can currently be vaccinated. There is a need to treat these viral infections without just treating the symptoms of the infection, as is currently the main method. There is a wide range of small molecules that have been used to inhibit various stages of the HPV infectious cycle. This review examined 132 small molecules from 121 studies that specifically target aspects of HPV infections. HPV DNA encodes for six early genes (E1 to E7, skipping E3) and two late genes (L1 and L2). According to the results, these targets for small molecule inhibitors fall into three categories: those targeting E1 and E2, targeting E6 and E7 and, finally, targeting L1 and L2. Inhibitors of E6 and E7 are the most widely studied targets, with the majority of HPV inhibition in this area. While compounds targeting both E1/E2 and E6/E7 have made it to clinical trials, there has been no significant advancement on the topic.

Molecular pathways in the development of HPV-induced oropharyngeal cancer

Oropharyngeal cancer, a subset of head and neck cancer, is increasingly recognized as a unique clinical entity primarily influenced by high-risk human papillomavirus (HPV) infections, particularly HPV-16. This review delves into the viral life cycle of HPV-16 and its interactions with host cells, with a specific focus on the crucial roles played by the viral oncoproteins E6 and E7. These oncoproteins drive cellular proliferation by targeting critical tumor suppressor proteins like p53 and Rb, resulting in uncontrolled cell growth and genomic instability. Furthermore, the significance of epigenetic modifications induced by HPV-16 and their implications is important for cancer progression. This comprehensive review provides valuable insights into the intricate molecular landscape of HPV-induced oropharyngeal cancer, shedding light on the development of targeted therapies and preventive strategies for this emerging global health concern. Video Abstract.

The Emerging Role of Histone Deacetylase Inhibitors in Cervical Cancer Therapy

Cervical carcinoma is one of the most common cancers among women globally. Histone deacetylase inhibitors (HDACIs) constitute anticancer drugs that, by increasing the histone acetylation level in various cell types, induce differentiation, cell cycle arrest, and apoptosis. The aim of the current review is to study the role of HDACIs in the treatment of cervical cancer. A literature review was conducted using the MEDLINE and LIVIVO databases with a view to identifying relevant studies. By employing the search terms "histone deacetylase" and "cervical cancer", we managed to identify 95 studies published between 2001 and 2023. The present work embodies the most up-to-date, comprehensive review of the literature centering on the particular role of HDACIs as treatment agents for cervical cancer. Both well-established and novel HDACIs seem to represent modern, efficacious anticancer drugs, which, alone or in combination with other treatments, may successfully inhibit cervical cancer cell growth, induce cell cycle arrest, and provoke apoptosis. In summary, histone deacetylases seem to represent promising future treatment targets in cervical cancer.

Histone Deacetylase Inhibitors as Therapeutic Interventions on Cervical Cancer Induced by Human Papillomavirus

The role of epigenetic modifications on the carcinogenesis process has received a lot of attention in the last years. Among those, histone acetylation is a process regulated by histone deacetylases (HDAC) and histone acetyltransferases (HAT), and it plays an important role in epigenetic regulation, allowing the control of the gene expression. HDAC inhibitors (HDACi) induce cancer cell cycle arrest, differentiation, and cell death and reduce angiogenesis and other cellular events. Human papillomaviruses (HPVs) are small, non-enveloped double-stranded DNA viruses. They are major human carcinogens, being intricately linked to the development of cancer in 4.5% of the patients diagnosed with cancer worldwide. Long-term infection of high-risk (HR) HPV types, mainly HPV16 and HPV18, is one of the major risk factors responsible for promoting cervical cancer development. In vitro and in vivo assays have demonstrated that HDACi could be a promising therapy to HPV-related cervical cancer. Regardless of some controversial studies, the therapy with HDACi could target several cellular targets which HR-HPV oncoproteins could be able to deregulate. This review article describes the role of HDACi as a possible intervention in cervical cancer treatment induced by HPV, highlighting the main advances reached in the last years and providing insights for further investigations regarding those agents against cervical cancer.

5azadC treatment upregulates miR-375 level and represses HPV16 E6 expression

High-risk human papillomaviruses are the etiological agents of cervical cancer and HPV16 is the most oncogenic genotype. Immortalization and transformation of infected cells requires the overexpression of the two viral oncoproteins E6 and E7 following HPV DNA integration into the host cell genome. Integration often leads to the loss of the E2 open reading frame and the corresponding protein can no longer act as a transcriptional repressor on p97 promoter. Recently, it has been proposed that long control region methylation also contributes to the regulation of E6/E7 expression.

To determine which epigenetic mechanism is involved in HPV16 early gene regulation, 5-aza-2′-deoxycytidine was used to demethylate Ca Ski and SiHa cell DNA. Decreased expression of E6 mRNA and protein levels was observed in both cell lines in an E2-independent manner. E6 repression was accompanied by neither a modification of the main cellular transcription factor expression involved in long control region regulation, nor by a modification of the E6 mRNA splicing pattern. In contrast, a pronounced upregulation of miR-375, known to destabilize HPV16 early viral mRNA, was observed. Finally, the use of miR-375 inhibitor definitively proved the involvement of miR-375 in E6 repression. These results highlight that cellular DNA methylation modulates HPV16 early gene expression and support a role for epigenetic events in high-risk HPV associated-carcinogenesis.

3-(2-Chloropropyl amide)-4-methoxy-N-phenylbenzamide inhibits expression of HPV oncogenes in human cervical cancer cell

BACKGROUND

Human papillomaviruses (HPVs) are the primary causative agents for cervical cancer, and HPV oncoproteins E6 and E7 are known to be the main reason for the onset and maintenance of the malignancies. Therefore, inhibition of viral E6 and E7 oncoproteins expression represents a viable strategy to cervical cancer therapies. This study is to evaluate the antiviral effect of a novel N-Phenylbenzamide derivative, 3-(2-Chloropropyl amide)-4-methoxy-N-phenylbenzamide (L17), against HPV16 in vitro and identify its associated mechanism of action in cervical cancer cells.

METHODS

The cytotoxic effect of L17 was assessed by MTT assay. The mRNA and protein levels of E6 and E7 oncogenes were analyzed by quantitative real-time reverse transcription PCR (qRT-PCR) and Western blot, respectively. p53 and Rb protein levels were also detected by Western blot. The effect of L17 on cell cycle was analyzed by flow cytometry.

RESULTS

The cytotoxic effect of L17 was greater in cervical carcinoma cells than in normal cells. L17 significantly reduced the expression of HPV16 E6 and E7 mRNA and protein, at least partly by enhancing degradation of HPV16 E6 and E7 mRNA. Moreover, reduced expression of E6 and E7 induced by L17 resulted in the up-regulation of p53 and Rb expression, which subsequently induced CaSki cells arrest at G₀/G₁ phase.

CONCLUSIONS

L17 has antiviral activity through suppressing E6 and E7 oncogene expression and could inhibit CaSki cell proliferating by inducing cells arrest at G₀/G₁ phase at nontoxic concentration, implying that L17 might be exploited as a candidate agent for HPV-associated cervical cancer prevention and treatment.

Short interfering RNA induced generation and translation of stable 5' mRNA cleavage intermediates

Sequence-specific degradation of homologous mRNA is the main mechanism by which short-interfering RNAs (siRNAs) suppress gene expression. Generally, it is assumed that the mRNA fragments resulting from Ago2 cleavage are rapidly degraded, thus making the transcript translation-incompetent. However, the molecular mechanisms involved in the post-cleavage mRNA decay are not completely understood and the fate of cleavage intermediates has been poorly studied. Using specific siRNAs and short-hairpin RNAs (shRNAs) we show that the 5' and 3' mRNA cleavage fragments of human papilloma virus type 16 (HPV-16) E6/7 mRNA, over-expressed in cervical malignancies, are unevenly degraded. Intriguingly, the 5' mRNA fragment was more abundant and displayed a greater stability than the corresponding 3' mRNA fragment in RNAi-treated cells. Further analysis revealed that the 5' mRNA fragment was polysome-associated, indicating its active translation, and this was further confirmed by using tagged E7 protein to show that C-terminally truncated proteins were produced in treated cells. Overall, our findings provide new insight into the degradation of siRNA-targeted transcripts and show that RNAi can alter protein expression in cells as a result of preferential stabilization and translation of the 5' cleavage fragment. These results challenge the current model of siRNA-mediated RNAi and provide a significant step forward towards understanding non-canonical pathways of siRNA gene silencing.

SAHA inhibits the transcription initiation of HPV18 E6/E7 genes in HeLa cervical cancer cells

High risk human papillomavirus (HPV) is a well recognized causative agent of cervical cancer. Suberoylanilide hydroxamic acid (SAHA) is a potential anti-cervical cancer drug; however, its effect on the expression of HPV E6 and E7 genes remains unclear. Here, we show that, in SAHA treated HeLa cells, HPV18 E6 and E7 mRNA and protein levels were reduced, HPV18 promoter activity was decreased, and the association of RNP II with HPV18 promoter was diminished, suggesting that SAHA inhibited the transcription initiation of HPV18 E6 and E7 genes. In SAHA-treated HeLa, although the level of lysine 9-acetylated histone H3 in the whole cell extracts increased obviously, its enrichment on HPV18 promoter was significantly reduced which is correlated with the down-regulation of HPV E6 and E7.

Utilization of Boron Compounds for the Modification of Suberoyl Anilide Hydroxamic Acid as Inhibitor of Histone Deacetylase Class II Homo sapiens

Histone deacetylase (HDAC) has a critical function in regulating gene expression. The inhibition of HDAC has developed as an interesting anticancer research area that targets biological processes such as cell cycle, apoptosis, and cell differentiation. In this study, an HDAC inhibitor that is available commercially, suberoyl anilide hydroxamic acid (SAHA), has been modified to improve its efficacy and reduce the side effects of the compound. Hydrophobic cap and zinc-binding group of these compounds were substituted with boron-based compounds, whereas the linker region was substituted with p-aminobenzoic acid. The molecular docking analysis resulted in 8 ligands with ΔG_binding value more negative than the standards, SAHA and trichostatin A (TSA). That ligands were analyzed based on the nature of QSAR, pharmacological properties, and ADME-Tox. It is conducted to obtain a potent inhibitor of HDAC class II Homo sapiens. The screening process result gave one best ligand, Nova2 (513246-99-6), which was then further studied by molecular dynamics simulations.

Antiviral activity of Bifidobacterium adolescentis SPM1005-A on human papillomavirus type 16

BACKGROUND

Probiotic lactic acid bacteria (LAB) support a functional and balanced immune system, and contribute to immune modulatory effects in combatting microbial pathogens, including viruses. Most cervical cancers are associated with anogenital region infection with high-risk (HR) human papillomavirus (HPV). In this study, we analyzed the antiviral activity of Bifidobacterium adolescentis SPM1005-A in the SiHa cervical cancer cell line expressing HPV type 16.

METHODS

We assessed the cellular toxicity of B. adolescentis SPM1005-A in SiHa cells by the Trypan blue dye exclusion assay. Cells (3.6 × 105) in culture plates with or without B. adolescentis SPM1005-A in the same type of medium, were incubated with HPV type 16 at a concentration of 5.1 × 107 cfu/ml. For antiviral analysis, we performed quantitative real-time PCR (qRT-PCR) for E6 and E7 oncogene expressions and observed protein levels by immunoblotting.

RESULTS

The qRT-PCR results showed that E6 and E7 mRNA levels decreased simultaneously. Western blot analysis revealed that the E6 protein expression slightly decreased after 24 and 48 h, but the level of E7 protein expression appear unaffected compared with that in the control. Decreased HPV16 E6 and E7 mRNA transcript and protein levels were not associated with cell morphology or significant cytotoxic effects.

CONCLUSIONS

This study showed that B. adolescentis SPM1005-A had antiviral activity through suppression E6 and E7 oncogene expression. The results suggest that B. adolescentis SPM1005-A could be potential applications of HPV-associated cervical cancer prevention.

Emerging promise of epigenetics and DNA methylation for the diagnosis and management of women's cancers

Over the last two decades, survival rates from women's cancers (breast, ovarian, endometrial and cervical cancer) have all but modestly improved despite huge efforts from both research and clinical communities. In parallel with this, the field of epigenetics has grown from its infancy into a promising scientific discipline. In particular, DNA methylation analysis has been adopted by oncologists in an attempt to better understand and manage cancer. Now that the epigenetic technological base has caught up, the potential of methylation markers in cancer research is finally being realized. In this review, we present the current status of epigenetic research into women's cancers with a main focus on DNA methylation analysis. We provide an overview of technological development, current markers of risk prediction, early detection, diagnosis, prognosis and response to treatment, and highlight the progression of epigenetic therapies. Finally, we comment on the potential impact of epigenetic analyses on the future of women's health.

Nuclear receptor mRNA expression by HBV in human hepatoblastoma cell lines

Recent studies have implicated nuclear receptors (NRs) in the development of hepatocarcinogenesis. We assumed that hepatitis B virus (HBV) alters the expression of NRs and coregulators, and compared the gene expression profiling for 84 NRs and related genes between HpeG2.2.15, which secretes complete HBV virion, and HepG2 by real-time RT-PCR with SyBr green. Forty (47.6%) genes were upregulated 2-fold or greater, and only 5 (5.9%) were downregulated 2-fold or more, in HepG2.2.15 compared to HepG2. These results suggest that HBV affects NRs and their related signal transduction, and that they play important roles in viral replication and HBV-related hepatocarcinogenesis.

Butyrate induces expression of 17β-hydroxysteroid dehydrogenase type 1 in HT29 and SW707 colorectal cancer cells

Epidemiological studies have revealed that butyrate and 17β-estradiol (E2) may decrease the incidence of colorectal cancer (CRC). In peripheral tissue, E2 can be produced locally by 17β-hydroxysteroid dehydrogenase 1 (HSD17B1) estrone (E1) reduction. Using quantitative real-time polymerase chain reaction and western blotting analysis, we found that sodium butyrate significantly upregulates HSD17B1 long and short transcripts and protein levels in HT29 and SW707 CRC cells. Chromatin immunoprecipitation analysis showed that upregulation of these transcript levels correlated with an increase in binding of Polymerase II to proximal and distal promoters of HSD17B1. Moreover, we observed that upregulation of HSD17B1 protein levels was associated with increased conversion of E1 to E2 in HT29 and SW707 CRC cells. Since sodium butyrate increases the conversion of E1 to E2, our findings may support the validity of butyrate in the prophylaxis of CRC incidence.

Apicidin suppresses transcription of 17β-hydroxysteroid dehydrogenase type 1 in endometrial adenocarcinoma cells

It has recently been reported that endometrial cancer cells are able to convert estron (E1) to 17β estradiol (E2). We observed the presence of 17β-hydroxysteroid dehydrogenase type 1 (HSD17B1) transcript and protein in receptor positive ER(+) and negative ER(-) Ishikawa endometrial adenocarcinoma (ISH) cells. ER(+) ISH, but not ER(-)02 ISH, cells were significantly susceptible to apicidin induced death, and we further used ER(-)ISH cells to study the effect of apicidin on cellular levels of HSD17B1 transcript and protein. We showed that apicidin significantly lowered HSD17B1 transcript and protein levels in ISH cells. There was no significant effect on HSD17B1 transcript stability. However, chromatin immunoprecipitation analysis revealed that apicidin significantly decreased occupation of the first exon of the HSD17B1 gene by Polymerase II. Since intratumoral E1 to E2 conversion is a significant contributor to the progression of estrogen dependent cancers, and HDAC inhibitors are being tested in anticancer clinical trials, our observations may have clinical value.

Histone deacetylases in viral infections

Chromatin remodeling and gene expression are regulated by histone deacetylases (HDACs) that condense the chromatin structure by deacetylating histones. HDACs comprise a group of enzymes that are responsible for the regulation of both cellular and viral genes at the transcriptional level. In mammals, a total of 18 HDACs have been identified and grouped into four classes, i.e., class I (HDACs 1, 2, 3, 8), class II (HDACs 4, 5, 6, 7, 9, 10), class III (Sirt1–Sirt7), and class IV (HDAC11). We review here the role of HDACs on viral replication and how HDAC inhibitors could potentially be used as new therapeutic tools in several viral infections.