The polycomb group protein enhancer of zeste 2 is a novel therapeutic target for cervical cancer

Comparative analysis of EZH2, p16 and p53 expression in uterine carcinosarcomas

Introduction: The role of p16 and p53 immunohistochemistry in the diagnosis of rare and aggressive uterine carcinosarcoma (UCS) has been well established. However, enhancer of zeste homolog 2 (EZH2), a histone methyltransferase and a member of the polycomb group family is a relatively new biomarker, with limited published data on its significance in this tumor type. The goal of this study was to examine EZH2 expression in UCS and its components, in correlation with morphological features, and p16 and p53 staining patterns. Methods: Twenty-eight UCSs were included in the study. EZH2, p16 and p53 immunoreactivity were assessed independently by two pathologists in both tumor components (epithelial and mesenchymal). EZH2 and p16 immunostains were scored semiquantitatively: based on the percentage and intensity of tumor cell staining a binary staining index ("high- or low-expressing") was calculated. The p53 staining pattern was evaluated as wild-type or aberrant (diffuse nuclear, null, or cytoplasmic expression). Statistical tests were used to evaluate the correlation between staining patterns for all three markers and the different tumor components and histotypes. Results: High EZH2 and p16 expression and aberrant p53 patterns were present in 89.3% 78.6% and 85.7% of the epithelial component and in 78.6%, 62.5% and 82.1% of the mesenchymal component, respectively. Differences among these expression rates were not found to be significant (p > 0.05). Regarding the epithelial component, aberrant p53 pattern was found to be significantly (p = 0.0474) more frequent in the serous (100%) than in endometrioid (66.6%) histotypes. Within the mesenchymal component, p53 null expression pattern occurred significantly (p = 0.0257) more frequently in heterologous sarcoma components (71.4%) compared to the homologous histotype (18.8%). Conclusion: In conclusion, EZH2, p16 and p53 seem to play a universal role in the pathogenesis of UCS; however, a distinctive pattern of p53 expression appears to exist between the serous and endometrioid carcinoma components and also between the homologous and heterologous sarcoma components.

Ultrasound microbubble-mediated delivery of ANLN silencing-repressed EZH2 expression alleviates cervical cancer progression

Ultrasound-targeted microbubble destruction (UTMD) is a new gene therapy method that uses ultrasound and microbubbles carrying target genes to achieve gene transfection. However, whether UTMD-mediated ANLN silencing transfection helps to restrain the growth of cervical cancer (CC) is obscure. ANLN level in tumor tissues, adjacent tissues, and cells was tested using the database, qRT-PCR, and western blot. The optimal concentration of SF6 was determined by MTT assay. Mechanical index (MI) was selected by flow cytometry. After transfection with liposome or UTMD-mediated liposome, cell function experiments, qRT-PCR, and western blot were employed to assess CC cell biological behaviors and EZH2 level. Epithelial-mesenchymal transition (EMT)-related marker and apoptosis-related marker expressions were examined utilizing qRT-PCR and western blot. 10% SF6 and MI of 0.28 were selected for subsequent tests. ANLN was highly expressed in CC and cells. The transfection efficiency of the UTMD-siANLN group was higher than that of the L-siANLN group. Moreover, the repression of UTMD-siANLN on CC cell malignant phenotypes was stronger than L-siANLN. UTMD-siANLN attenuated EZH2 expression in CC cells. The modulatory role of UTMD-siANLN on EMT- and apoptosis-related markers was reversed by EZH2 overexpression. UTMD can improve the efficiency of siANLN transfection into CC cells to induce suppression of CC cell malignant phenotypes, which may become a new target of gene therapy for CC.

EZH2 inhibition decreases neuroblastoma proliferation and in vivo tumor growth

Investigation of the mechanisms responsible for aggressive neuroblastoma and its poor prognosis is critical to identify novel therapeutic targets and improve survival. Enhancer of Zeste Homolog 2 (EZH2) is known to play a key role in supporting the malignant phenotype in several cancer types and knockdown of EZH2 has been shown to decrease tumorigenesis in neuroblastoma cells. We hypothesized that the EZH2 inhibitor, GSK343, would affect cell proliferation and viability in human neuroblastoma. We utilized four long-term passage neuroblastoma cell lines and two patient-derived xenolines (PDX) to investigate the effects of the EZH2 inhibitor, GSK343, on viability, motility, stemness and in vivo tumor growth. Immunoblotting confirmed target knockdown. Treatment with GSK343 led to significantly decreased neuroblastoma cell viability, migration and invasion, and stemness. GSK343 treatment of mice bearing SK-N-BE(2) neuroblastoma tumors resulted in a significant decrease in tumor growth compared to vehicle-treated animals. GSK343 decreased viability, and motility in long-term passage neuroblastoma cell lines and decreased stemness in neuroblastoma PDX cells. These data demonstrate that further investigation into the mechanisms responsible for the anti-tumor effects seen with EZH2 inhibitors in neuroblastoma cells is warranted.

Loss of histone lysine methyltransferase EZH2 confers resistance to tyrosine kinase inhibitors in non-small cell lung cancer

Tyrosine kinase inhibitor (TKI) treatment is the first-line therapy for non-small cell lung cancer (NSCLC) caused by activating mutations of epidermal growth factor receptor (EGFR). However, acquired resistance to EGFR-TKI occurs almost inevitably. Aberrant activation of proto-oncogene MET has been known to confer EGFR-TKI resistance; however, the mechanisms involved remains unclear. Recent evidence implicates epigenetic heterogeneity as playing roles in cancer drug resistance, whereas links involving epigenetic heterogeneity and MET in NSCLC remain poorly understood. We found that expression of EZH2, a histone methyltransferase, was negatively correlated with MET activation and EGFR-TKI resistance in NSCLC cells and clinical samples, suggesting the potential for EZH2 to be used as a biomarker for EGFR-TKI sensitivity. Knockdown or inhibition of EZH2 up-regulated MET expression and phosphorylation, and elevated proliferation and EGFR-TKI resistance of cells in vitro. Meanwhile, inhibition of MET or PI3K/AKT enhanced EZH2 levels and restored sensitivity to EGFR-TKI. These findings indicate a "MET-AKT-EZH2" feedback loop regulating EGFR-TKI-resistance. Furthermore, combination therapy of PI3K/AKT inhibition and EGFR-TKI, which interrupts the loop, enhanced tumor-suppressive effects in an EGFR-TKI-resistant xenograft model, indicating a potential approach against drug resistance in NSCLC.

Next-generation sequencing identifies recurrent copy number variations in invasive breast carcinomas from Ghana

African and African-American (AA) women have higher incidence of triple-negative breast cancers (TNBC) with high histological grade and aggressive clinical behavior, but the reasons are not fully understood. We recently found that the oncogenic protein EZH2 is overexpressed in Ghanaian breast cancer patients, with 16% of the tumors expressing cytoplasmic EZH2. Understanding the molecular underpinnings of these aggressive tumors may lead to the identification of potential targetable oncogenic drivers. We characterized the copy number variations of 11 Ghanaian breast tumor patients by targeted multiplexed PCR-based DNA next-generation sequencing (NGS) over 130 cancer-relevant genes. While the DNA quality was not optimal for mutation analysis, 90% of the tumors had frequent recurrent copy number alterations (CNAs) of 17 genes: SDHC, RECQL4, TFE3, BCL11A, BCL2L1, PDGFRA, DEK, SMUG1, AKT3, SMARCA4, VHL, KLF6, CCNE1, G6PD, FGF3, ABL1, and CCND1, with the top oncogenic functions being mitotic G1-G1/S-phase regulation, gene transcription, apoptosis, and PI3K/AKT pathway. The most common recurrent high-level CNAs were gains of RECQL4 and SDHC, in 50% and 60% of cases, respectively. Network analyses revealed a significant predicted interaction among 12 of the 17 (70.6%) genes with high-level CNAs (p = 5.7E-07), which was highly correlated with EZH2 expression (r = 0.4-0.75). By immunohistochemistry, RECQL4 and SDHC proteins were upregulated in 53 of 86 (61.6%) and 48 of 86 (56%) of Ghanaian invasive carcinoma tissue samples. In conclusion, our data show that invasive carcinomas from Ghana exhibit recurrent CNAs in 17 genes, with functions in oncogenic pathways, including PI3K/AKT and G1-G1/S regulation, which may have implications for the biology and treatment of invasive carcinomas in African and AA women.

Inhibition of Histone Methyltransferase EZH2 Suppresses Endometriotic Vesicle Development in a Rat Model of Endometriosis

Endometriosis is a painful gynecological disease with no cure and limited therapeutic options. It has been hypothesized that epigenetic drugs can be used as a nonhormonal treatment for endometriosis. This study was conducted to study the efficacy of an inhibitor of the histone methyltransferase EZH2 using an established rat model of endometriosis. We hypothesized that treatment will block or reduce the number of endometriotic vesicles in this model. We conducted a preclinical drug study in female rats with experimental endometriosis (uterine tissue transplanted next to the intestinal mesentery) or control sham (sutures only). Rats with endometriosis or sham surgery received either treatment with EZH2 inhibitor (5 mg/kg or 10 mg/kg) or vehicle (0.1%, 67% DMSO) every other day during 4 weeks. After treatment completion, the number, area, volume, and weight of vesicles were evaluated. RT [2] Profiler Arrays for neuropathic and inflammation, epithelial to mesenchymal transition, inflammatory response, and autoimmunity pathways were used to examine gene expression changes in the vesicles that developed. Treatment with EZH2 inhibitor (10 mg/kg) suppressed the development of vesicles, by significantly decreasing the total vesicle number, area, volume, and weight. In addition, EZH2 inhibition significantly increased the expression of CACNA1B and FKBP1A genes, involved in pain and proliferation, respectively. EZH2 inhibition suppresses the growth of vesicles without apparent detrimental effects to other organs. Treatment with this epigenetic inhibitor leads to upregulation of a limited number of genes related to endometriosis-relevant pathways. In conclusion, these data support follow-up studies to evaluate its potential as a therapeutic approach for endometriosis.

Epigenetic Modulators as Potential Multi-targeted Drugs Against Hedgehog Pathway for Treatment of Cancer

The Sonic hedgehog signalling is known to play a crucial role in regulating embryonic development, cancer stem cell maintenance and tissue patterning. Dysregulated hedgehog signalling has been reported to affect tumorigenesis and drug response in various human malignancies. Epigenetic therapy relying on DNA methyltransferase and Histone deacetylase inhibitors are being proposed as potential drug candidates considering their efficiency in preventing development of cancer progenitor cells, killing drug resistant cells and also dictating "on/off" switch of tumor suppressor genes and oncogenes. In this docking approach, epigenetic modulators were virtually screened for their efficiency in inhibiting key regulators of SHH pathway viz., sonic hedgehog, Smoothened and Gli using polypharmacological approach. The control drugs and epigenetic modulators were docked with PDB protein structures using AutoDock vina and further checked for their drug-likeness properties. Further molecular dynamics simulation using VMD and NAMD, and MMP/GBSA energy calculation were employed for verifying the stability and entropy of the ligand-receptor complex. EPZ-6438 and GSK 343 (EZH2 inhibitors), CHR 3996 and Mocetinostat (HDAC inhibitors), GSK 126 (HKMT inhibitor) and UNC 1215 (L3MBTL3 antagonist) exhibited multiple-targeted approach in modulating HH signalling. This is the first study to report these epigenetic drugs as potential multi-targeted hedgehog pathway inhibitors. Thus, epigenetic polypharmacology approach can be explored as a better alternative to challenges of acute long term toxicity and drug resistance occurring due to traditional single targeted chemotherapy in the future.

Effects of histone methyltransferase inhibition in endometriosis

Although the histone methyltransferase EZH2 and its product H3K27me3 are well studied in cancer, little is known about their role and potential as therapeutic targets in endometriosis. We have previously reported that endometriotic lesions are characterized by global enrichment of H3K27me3. Therefore, we aimed to (1) characterize the expression levels of EZH2 in endometriotic tissues; (2) assess H3K27me3 enrichment in candidate genes promoter regions; and (3) determine if pharmacological inhibition of EZH2 impacts migration, proliferation, and invasion of endometriotic cells. Immunohistochemistry of an endometriosis-focused tissue microarray was used to assess the EZH2 protein levels in tissues. Chromatin immunoprecipitation-qPCR was conducted to assess enrichment of H3K27me3 in candidate gene promoter regions in tissues. Immunofluorescence was performed to assess the effect of an EZH2-specific pharmacological inhibitor on H3K27me3 global enrichment in cell lines. To measure effects of the inhibitor in migration, proliferation, and invasion in vitro we used Scratch, BrdU, and Matrigel assays, respectively. Endometriotic lesions had significantly higher EZH2α nuclear immunostaining levels compared to eutopic endometrium from patients (glands, stroma) and controls (glands). H3K27me3 was enriched within promoter regions of candidate genes in some but not all of the endometriotic lesions. Inhibition of EZH2 reduced H3K27me3 levels in the endometriotic cells specifically, and also reduced migration, proliferation but not invasion of endometriotic epithelial cells (12Z). These findings support future preclinical studies to determine in vivo efficacy of EZH2 inhibitors as promising nonhormonal treatments for endometriosis, still an incurable gynecological disease.

Long non-coding RNA LINC01535 promotes cervical cancer progression via targeting the miR-214/EZH2 feedback loop

Long non‐coding RNAs (lncRNAs) have shown critical roles in multiple cancers via competitively binding common microRNAs. miR‐214 has been proved to play tumour suppressive roles in various cancers, including cervical cancer. In this study, we identified that lncRNA LINC01535 physically binds miR‐214, relieves the repressive roles of miR‐214 on its target EZH2, and therefore up‐regulates EZH2 protein expression. Intriguingly, we also found that EZH2 directly represses the expression of miR‐214. Thus, miR‐214 and EZH2 form double negative regulatory loop. Through up‐regulating EZH2, LINC01535 further represses miR‐214 expression. Functional experiments showed that enhanced expression of LINC01535 promotes cervical cancer cell growth, migration and invasion in vitro and cervical cancer xenograft growth in vivo. Reciprocally, LINC01535 knockdown suppresses cervical cancer cell growth, migration and invasion. Activation of the miR‐214/EZH2 regulatory loop by overexpression of miR‐214 or silencing of EZH2 reverses the roles of LINC01535 in promoting cervical canc`er cell growth, migration and invasion in vitro and cervical cancer xenograft growth in vivo. Clinically, LINC01535 is significantly up‐regulated in cervical cancer tissues and correlated with advanced clinical stage and poor prognosis. Moreover, the expression of LINC01535 is reversely associated with the expression of miR‐214 and positively associated with the expression of EZH2 in cervical cancer tissues. In conclusion, this study reveals that LINC01535 promotes cervical cancer progression via repressing the miR‐214/EZH2 regulatory loop.

A polycomb-mediated epigenetic field defect precedes invasive cervical carcinoma

Human papillomavirus (HPV)-associated cervical carcinoma is preceded by stages of cervical intra-epithelial neoplasia (CIN) that can variably progress to malignancy. Understanding the different molecular processes involved in the progression of pre-malignant CIN is critical to the development of improved predictive and interventional capabilities. We tested the role of regulators of transcription in both the development and the progression of HPV-associated CIN, performing the most comprehensive genomic survey to date of DNA methylation in HPV-associated cervical neoplasia, testing ~2 million loci throughout the human genome in biopsies from 78 HPV+ women, identifying changes starting in early CIN and maintained through carcinogenesis. We identified loci at which DNA methylation is consistently altered, beginning early in the course of neoplastic disease and progressing with disease advancement. While the loss of DNA methylation occurs mostly at intergenic regions, acquisition of DNA methylation is at sites involved in transcriptional regulation, with strong enrichment for targets of polycomb repression. Using an independent cohort from The Cancer Genome Atlas, we validated the loci with increased DNA methylation and found that these regulatory changes were associated with locally decreased gene expression. Secondary validation using immunohistochemistry showed that the progression of neoplasia was associated with increasing polycomb protein expression specifically in the cervical epithelium. We find that perturbations of genomic regulatory processes occur early and persist in cervical carcinoma. The results indicate a polycomb-mediated epigenetic field defect in cervical neoplasia that may represent a target for early, topical interventions using polycomb inhibitors.

EZH2-mediated repression of GSK-3β and TP53 promotes Wnt/β-catenin signaling-dependent cell expansion in cervical carcinoma

Enhancer of zeste homolog 2 (EZH2), a catalytic core component of the Polycomb repressive complex 2 (PRC2), stimulates the silencing of target genes through histone H3 lysine 27 trimethylation (H3K27me3). Recent findings have indicated EZH2 is involved in the development and progression of various human cancers. However, the exact mechanism of EZH2 in the promotion of cervical cancer is largely unknown. Here, we show that EZH2 expression gradually increases during the progression of cervical cancer. We identified a significant positive correlation between EZH2 expression and cell proliferation in vitro and tumor formation in vivo by the up-regulation or down-regulation of EZH2 using CRISPR-Cas9-mediated gene editing technology and shRNA in HeLa and SiHa cells. Further investigation indicated that EZH2 protein significantly accelerated the cell cycle transition from the G0/G1 to S phase. TOP/FOP-Flash reporter assay revealed that EZH2 significantly activated Wnt/β-catenin signaling and the target genes of Wnt/β-catenin pathway were up-regulated, including β-catenin, cyclin D1, and c-myc. Moreover, dual-luciferase reporter and chromatin immunoprecipitation (ChIP) assays confirmed that EZH2 inhibited the expression of glycogen synthase kinase-3β (GSK-3β) and TP53 through physically interacting with motifs in the promoters of the GSK-3β and TP53 genes. Additionally, blockage of the Wnt/β-catenin pathway resulted in significant inhibition of cell proliferation, and activation of the Wnt/β-catenin pathway resulted in significant enhancement of cell proliferation, as induced by EZH2. Taken together, our data demonstrate that EZH2 promotes cell proliferation and tumor formation in cervical cancer through activating the Wnt/β-catenin pathway by epigenetic silencing via GSK-3β and TP53.

The EZH2 inhibitor GSK343 suppresses cancer stem-like phenotypes and reverses mesenchymal transition in glioma cells

Enhancer of zeste homolog 2 (EZH2) is the catalytic unit of polycomb repressive complex 2 (PRC2) which epigenetically silences many genes involved in tumor-suppressive mechanisms via the trimethylation of lysine 27 of histone H3 (H3K27me3). We recently found that overexpression of EZH2 was associated with poor outcome of glioblastoma (GBM). In this study, we examined the antitumor effects of the EZH2 inhibitor GSK343 on glioma cells in vitro and in vivo. The proliferation and cell cycle of glioma cells was measured. Wound healing assay and transwell invasion assay were performed to evaluate the capacity of migration and invasion of glioma cells. Western blot, qPCR, immunoprecipitation and fluorescent staining were used to test the levels of EZH2 and associated proteins. Spheroid formation assay and clonogenic assays were conducted to assess the stemness of glioma stem cells. Finally, the effect of GSK343 was measured through a nude mice model with intracranially xenotransplanted glioma. We found that GSK343 reduced proliferation, attenuated cell motility and reversed epithelial-mesenchymal transition in U87 and LN229 glioma cells. GSK343 also suppressed the stemness of cell lines and patient derived glioma stem cells. Further, GSK343 inhibited histone H3K27 methylation and upregulated the expression of EZH2 target genes thereby regulating the levels of markers involved in epithelial-mesenchymal transition and stemness. Taken together, our results indicate that GSK343 could be a potential drug against glioblastoma.

Efficacy of EZH2 inhibitory drugs in human papillomavirus-positive and human papillomavirus-negative oropharyngeal squamous cell carcinomas

Background

Head and neck squamous cell carcinoma (HNSCC) is the sixth most prevalent cancer worldwide with rates of HPV-positive oropharyngeal squamous cell carcinoma (OPSCC) dramatically increasing. The overexpression of enhancer of zeste homolog 2 (EZH2), a histone methyltransferase responsible for the trimethylation at lysine 27 of histone 3 (H3K27me3), is associated with a poor clinical prognosis and aggressive HPV-positive phenotypes.

Methods

We utilized three EZH2 pathway inhibitors, GSK-343, DZNeP, and EPZ-5687, and tested their efficacy in two HPV-positive and two HPV-negative OPSCC cell lines.

Results

Treatment with GSK-343 decreased H3K27me3 in all cell lines and treatment with DZNeP decreased H3K27me3 in only HPV-negative cell lines as determined by Western blot. Cells treated with EPZ-5687 displayed no appreciable change in H3K27me3. Epigenetic effect on gene expression was measured via ddPCR utilizing 11 target probes. Cells treated with DZNeP showed the most dramatic expressional changes, with decreased EGFR in HPV-positive cell lines and an overall increase in proliferation markers in HPV-negative cell lines. GSK-343-treated cells displayed moderate expressional changes, with CCND1 increased in HPV-positive cell lines and decreased TP53 in HPV-negative SCC-1. EPZ-5687-treated cell lines displayed few expressional changes overall. Only DZNeP-treated cells displayed anti-proliferative characteristics shown in wound-healing assays.

Conclusions

Our findings suggest that EZH2 inhibitors are a viable therapeutic option for the role of epigenetic effect, potentially sensitizing tumors to current chemotherapies or limiting cell differentiation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-017-0390-y) contains supplementary material, which is available to authorized users.

Epigenetic regulation of the extrinsic oncosuppressor PTX3 gene in inflammation and cancer

PTX3 is a component of the humoral arm of innate immunity and an extrinsic oncosuppressor gene taming tumor-promoting inflammation. Here, we show that two enhancers differently regulate PTX3 expression: enhancer 1, located 230 kb upstream of PTX3 promoter, mediated the action of inflammatory transcription factors; and enhancer 2, encompassing PTX3 second exon, was implicated in pre-initiation complex assembly. Polycomb repressive complex 2 silenced these regulatory elements and the promoter in basal condition. Enhancer 1 was epigenetically inactivated in early colorectal cancer (CRC) stages, while the promoter and enhancer 2 showed increasingly DNA methylation during CRC progression from adenomas to stage II and III CRC. Inhibition of DNA methylation rescued PTX3 expression in CRC. Finally, enhancer 1 acquired the binding of STAT3 in stage I CRC, and inhibition of STAT3 phosphorylation restored PTX3 activity and decreased enhancer 1 methylation. Thus, the expression of PTX3 is under the control of two enhancers, which emerge as important fine regulators of PTX3 expression in inflammation and cancer.

Impairment of both IRE1 expression and XBP1 activation is a hallmark of GCB DLBCL and contributes to tumor growth

The endoplasmic reticulum kinase inositol-requiring enzyme 1 (IRE1) and its downstream target X-box-binding protein 1 (XBP1) drive B-cell differentiation toward plasma cells and have been shown to contribute to multiple myeloma development; yet, little is known of the role of this pathway in diffuse large B-cell lymphoma (DLBCL). Here, we show that in the germinal center B-cell-like (GCB) DLBCL subtype, IRE1 expression is reduced to a level that prevents XBP1 activation. Gene expression profiles indicated that, in GCB DLBCL cancer samples, expression of IRE1 messenger RNA was inversely correlated with the levels and activity of the epigenetic repressor, histone methyltransferase enhancer of zeste homolog 2 (EZH2). Correspondingly, in GCB-derived cell lines, the IRE1 promoter carried increased levels of the repressive epigenetic mark histone 3 lysine 27 trimethylation. Pharmacological inhibition of EZH2 erased those marks and restored IRE1 expression and function in vitro and in vivo. Moreover, reconstitution of the IRE1-signaling pathway, by expression of the XBP1-active form, compromised GCB DLBCL tumor growth in a mouse xenograft cancer model. These findings indicate that IRE1-XBP1 downregulation distinguishes GCB DLBCL from other DLBCL subtypes and contributes to tumor growth.

Investigation of EZH2 pathways for novel epigenetic treatment strategies in oropharyngeal cancer

Background

In recent decades, the incidence of oropharyngeal squamous cell carcinoma (OPSCC) has been rising worldwide as a result of increasing oncogenic human papillomavirus (HPV) infections in the oropharynx. EZH2 is an epigenetic regulatory protein associated with tumor aggressiveness and negative survival outcomes in several human cancers. We aimed to determine the role of EZH2 as a potential therapeutic epigenetic target in HPV-positive and negative OPSCC.

Methods

The expression of EZH2 was measured by immunohistochemistry (IHC) and droplet digital PCR (ddPCR) in 2 HPV-positive and 2 HPV-negative cell lines. The cell lines were then cultured and treated with one of 3 EZH2 epigenetic inhibitors (3-deazaneplanocin A, GSK-343 and EPZ005687) or DMSO (control). Following 2, 4 and 7 days of treatment, cells were analyzed and compared by gene expression, cell survival and proliferation assays.

Results

EZH2 targeting resulted in greater inhibition of growth and survival in HPV-positive compared to HPV-negative cells lines. The expression profile of genes important in OPSCC also differed according to HPV-positivity for Ki67, CCND1, MET and PTEN/PIK3CA, but remained unchanged for EGFR, CDKN2A and p53.

Conclusion

Inhibition of EZH2 has anti-tumorigenic effects on OPSCC cells in culture that is more pronounced in HPV-positive cell lines. EZH2 is a promising epigenetic target for the treatment of OPSCC.

Novel strategies for molecular targeting to cancer

This editorial draws attention to the work published by CEPP in 2014-2015 on mechanisms underlying cancer drug resistance, invasion and metastasis. Genetic, genomic and immunological changes in platinum drug resistance and new drug candidates for cancer metastasis are highlighted. Attention is paid to the Epimedium plant drug icariin in glioblastoma invasion, the plant Avicennia marina bioactive compound Naphtho[1,2-b]furan-4,5-dione in breast cancer metastasis, the PI3K inhibitor BEZ235 in colon cancer stem cells, the histone methyltransferase EZH1 inhibitor GSK343 in cervical cancer, and vitamin D3 in prostate cancer.