Detection and analysis of the methylation status of PTCH1 gene involved in the hedgehog signaling pathway in a human gastric cancer cell line

The Cross-Talk between Epigenetic Gene Regulation and Signaling Pathways Regulates Cancer Pathogenesis

Cancer begins due to uncontrolled cell division. Cancer cells are insensitive to the signals that control normal cell proliferation. This uncontrolled cell division is due to the accumulation of abnormalities in different factors associated with the cell division, including different cyclins, cell cycle checkpoint inhibitors, and cellular signaling. Cellular signaling pathways are aberrantly activated in cancer mainly due to epigenetic regulation and post-translational regulation. In this chapter, the role of epigenetic regulation in aberrant activation of PI3K/AKT, Ras, Wnt, Hedgehog, Notch, JAK/STAT, and mTOR signaling pathways in cancer progression is discussed. The role of epigenetic regulators in controlling the upstream regulatory proteins and downstream effector proteins responsible for abnormal cellular signaling-mediated cancer progression is covered in this chapter. Similarly, the role of signaling pathways in controlling epigenetic gene regulation-mediated cancer progression is also discussed. We have tried to ascertain the current status of potential epigenetic drugs targeting several epigenetic regulators to prevent different cancers.

Targeting Hedgehog Pathway and DNA Methyltransferases in Uterine Leiomyosarcoma Cells

Uterine leiomyosarcoma (LMS) is an aggressive tumor that presents poor prognosis, high rates of recurrence and metastasis. Because of its rarity, there is no information available concerning LMS molecular mechanisms of origin and development. Here, we assessed the expression profile of Hedgehog (HH) signaling pathway markers and the effects of their pharmacological inhibition on uterine smooth muscle (UTSM), leiomyoma and LMS cells. Additionally, we also evaluated the effects of DNMTs inhibition on LMS cells behavior. Cell proliferation, migration and apoptosis rates were evaluated by MTT, Scratch and Annexin V assays, respectively. RNA expression and protein levels were assessed by qRT-PCR and Western blot. We found that SMO and GLIs (1, 2 and 3) expression was upregulated in LMS cells, with increased nuclear levels of GLI proteins. Treatment with LDE225 (SMOi) and Gant61 (GLIi) resulted in a significant reduction in Glis protein levels in LMS (p < 0.05). Additionally, the expression of DNMT (1, 3a, and 3b), as well as GLI1 nuclear expression, was significantly decreased after treatment with HH inhibitor in LMS cells. Our results showed that blocking of SMO, GLI and DNMTs is able to inhibit LMS proliferation, migration and invasion. Importantly, the combination of those treatments exhibited a potentiated effect on LMS malignant features due to HH pathway deactivation.

Epigenetic heterogeneity in cancer

Phenotypic and functional heterogeneity is one of the hallmarks of human cancers. Tumor genotype variations among tumors within different patients are known as interpatient heterogeneity, and variability among multiple tumors of the same type arising in the same patient is referred to as intra-patient heterogeneity. Subpopulations of cancer cells with distinct phenotypic and molecular features within a tumor are called intratumor heterogeneity (ITH). Since Nowell proposed the clonal evolution of tumor cell populations in 1976, tumor heterogeneity, especially ITH, was actively studied. Research has focused on the genetic basis of cancer, particularly mutational activation of oncogenes or inactivation of tumor-suppressor genes (TSGs). The phenomenon of ITH is commonly explained by Darwinian-like clonal evolution of a single tumor. Despite the monoclonal origin of most cancers, new clones arise during tumor progression due to the continuous acquisition of mutations. It is clear that disruption of the "epigenetic machinery" plays an important role in cancer development. Aberrant epigenetic changes occur more frequently than gene mutations in human cancers. The epigenome is at the intersection of the environment and genome. Epigenetic dysregulation occurs in the earliest stage of cancer. The current trend of epigenetic therapy is to use epigenetic drugs to reverse and/or delay future resistance to cancer therapies. A majority of cancer therapies fail to achieve durable responses, which is often attributed to ITH. Epigenetic therapy may reverse drug resistance in heterogeneous cancer. Complete understanding of genetic and epigenetic heterogeneity may assist in designing combinations of targeted therapies based on molecular information extracted from individual tumors.

Prognostic significance of the methylation of Wnt pathway antagonists-CXXC4, DACT2, and the inhibitors of sonic hedgehog signaling-ZIC1, ZIC4, and HHIP in head and neck squamous cell carcinomas

Objectives

Aberrations in Wnt and Shh signaling pathways are related to the pathogenesis of head and neck carcinomas, and their activation frequently results from epigenetic alterations. This study aimed to assess the frequency of methylation of negative regulators of Wnt signaling: CXXC4, DACT2, HDPR1, and FBXW11 and Shh signaling: HHIP, PTCH1, SUFU, ZIC1, and ZIC4 and correlate it with clinicopathological features in this group of patients.

Materials and methods

Methylation-specific PCR was used to detect gene promoter methylation, and real-time PCR was used to assess gene expression level.

Results

The analysis of the occurrence of gene promoter methylation in head and neck carcinoma cell lines indicated that CXXC4, DACT2, HHIP, ZIC1, and ZIC4 are methylated in these tumors. These genes were further analyzed in tumor sections from oral and laryngeal cancer patients. Gene methylation rate was higher in laryngeal tumors. The methylation index in tumor samples correlated with the overall survival in a subgroup of oral cancer patients who died of the disease. Moreover, ZIC4 methylation correlated with lymph node involvement in oral cancer patients.

Conclusions

Our findings corroborate that the activation of Wnt signaling in head and neck squamous cell carcinoma (HNSCC) is related to epigenetic silencing of its negative regulators. Moreover, the results indicate that the same mechanism of activation may operate in the case of Shh signaling.

Clinical relevance

The methylation of ZIC4 may be considered a new prognostic marker in oral cavity and oropharyngeal tumors. Further investigations should determine the diagnostic significance of methylation of ZIC4, HHIP, and DACT2 in head and neck carcinomas.

Cooperative integration between HEDGEHOG-GLI signalling and other oncogenic pathways: implications for cancer therapy

The HEDGEHOG-GLI (HH-GLI) signalling is a key pathway critical in embryonic development, stem cell biology and tissue homeostasis. In recent years, aberrant activation of HH-GLI signalling has been linked to several types of cancer, including those of the skin, brain, lungs, prostate, gastrointestinal tract and blood. HH-GLI signalling is initiated by binding of HH ligands to the transmembrane receptor PATCHED and is mediated by transcriptional effectors that belong to the GLI family, whose activity is finely tuned by a number of molecular interactions and post-translation modifications. Several reports suggest that the activity of the GLI proteins is regulated by several proliferative and oncogenic inputs, in addition or independent of upstream HH signalling. The identification of this complex crosstalk and the understanding of how the major oncogenic signalling pathways interact in cancer is a crucial step towards the establishment of efficient targeted combinatorial treatments. Here we review recent findings on the cooperative integration of HH-GLI signalling with the major oncogenic inputs and we discuss how these cues modulate the activity of the GLI proteins in cancer. We then summarise the latest advances on SMO and GLI inhibitors and alternative approaches to attenuate HH signalling through rational combinatorial therapies.

Prediction of spontaneous regression of cervical intraepithelial neoplasia lesions grades 2 and 3 by proteomic analysis

Regression of cervical intraepithelial neoplasia (CIN) 2-3 to CIN 1 or less is associated with immune response as demonstrated by immunohistochemistry in formaldehyde-fixed paraffin-embedded (FFPE) biopsies. Proteomic analysis of water-soluble proteins in supernatants of biopsy samples with LC-MS (LTQ-Orbitrap) was used to identify proteins predictive of CIN2-3 lesions regression. CIN2-3 in the biopsies and persistence (CIN2-3) or regression (≤CIN1) in follow-up cone biopsies was validated histologically by two experienced pathologists. In a learning set of 20 CIN2-3 (10 regressions and 10 persistence cases), supernatants were depleted of seven high abundance proteins prior to unidimensional LC-MS/MS protein analysis. Mean protein concentration was 0.81 mg/mL (range: 0.55–1.14). Multivariate statistical methods were used to identify proteins that were able to discriminate between regressive and persistent CIN2-3. The findings were validated in an independent test set of 20 CIN2-3 (10 regressions and 10 persistence cases). Multistep identification criteria identified 165 proteins. In the learning set, zinc finger protein 441 and phospholipase D6 independently discriminated between regressive and persistent CIN2-3 lesions and correctly classified all 20 patients. Nine regression and all persistence cases were correctly classified in the validation set. Zinc finger protein 441 and phospholipase D6 in supernatant samples detected by LTQ-Orbitrap can predict regression of CIN2-3.

Role of PTCH1 gene methylation in gastric carcinogenesis

The present study aimed to investigate the role of PTCH1 methylation in gastric carcinogenesis and the therapeutic effect of the methylation inhibitor, 5-aza-2′-deoxycytidine (5-aza-dC), in the treatment of gastric cancer. Total RNA was extracted from 20 gastric cancer tissues, their corresponding adjacent normal tissues and a gastric cancer AGS cell line. PTCH1 mRNA expression was detected by quantitative PCR, and the PTCH1 methylation of the promoter was examined by methylation-specific PCR. The AGS cells were treated with 5-Aza-dC; apoptosis and the cell cycle were examined by flow cytometry, and the PTCH1 methylation level was observed. PTCH1 expression was negatively correlated with promoter methylation in the gastric cancer tissues, their corresponding adjacent normal tissues and the gastric cancer AGS cell line (r=−0.591, P=0.006). 5-Aza-dC treatment caused apoptosis and the G₀/G₁ phase arrest of the AGS cells, and also induced the demethylation and increased expression of PTCH1. In conclusion, the study found that the hypermethylation of the PTCH1 gene promoter region is one of the main causes of low PTCH1 expression in AGS cells. Demethylation agent 5-Aza-dC can reverse the methylation status of PTCH1 and regulate the expression of PTCH1, indicating its potential role in gastric cancer treatment.