DNA methylation transcriptionally regulates the putative tumor cell growth suppressor ZNF677 in non-small cell lung cancers

In our study, we investigated the role of ZNF677 in non-small cell lung cancers (NSCLC). By comparing ZNF677 expression in primary tumor (TU) and in the majority of cases also of corresponding non-malignant lung tissue (NL) samples from > 1,000 NSCLC patients, we found tumor-specific downregulation of ZNF677 expression (adjusted p-values < 0.001). We identified methylation as main mechanism for ZNF677 downregulation in NSCLC cells and we observed tumor-specific ZNF677 methylation in NSCLC patients (p < 0.0001). In the majority of TUs, ZNF677 methylation was associated with loss of ZNF677 expression. Moreover, ZNF677 overexpression in NSCLC cells was associated with reduced cell proliferation and cell migration. ZNF677 was identified to regulate expression of many genes mainly involved in growth hormone regulation and interferon signalling. Finally, patients with ZNF677 methylated TUs had a shorter overall survival compared to patients with ZNF677 not methylated TUs (p = 0.013). Overall, our results demonstrate that ZNF677 is trancriptionally regulated by methylation in NSCLCs, suggest that ZNF677 has tumor cell growth suppressing properties in NSCLCs and that ZNF677 methylation might serve as prognostic parameter in these patients

Genome-wide CpG island methylation analyses in non-small cell lung cancer patients

DNA methylation is part of the epigenetic gene regulation complex, which is relevant for the pathogenesis of cancer. We performed a genome-wide search for methylated CpG islands in tumors and corresponding non-malignant lung tissue samples of 101 stages IIII non-small cell lung cancer (NSCLC) patients by combining methylated DNA immunoprecipitation and microarray analysis. Overall, we identified 2414 genomic positions differentially methylated between tumor and non-malignant lung tissue samples. Ninety-seven percent of them were found to be tumor-specifically methylated. Annotation of these genomic positions resulted in the identification of 477 tumor-specifically methylated genes of which many are involved in regulation of gene transcription and cell adhesion. Tumor-specific methylation was confirmed by a gene-specific approach. In the majority of tumors, methylation of certain genes was associated with loss of their protein expression determined by immunohistochemistry. Treatment of NSCLC cells with epigenetically active drugs resulted in upregulated expression of many tumor-specifically methylated genes analyzed by gene expression microarrays suggesting that about one-third of these genes are transcriptionally regulated by methylation. Moreover, comparison of methylation results with certain clinicopathological characteristics of the patients suggests that methylation of HOXA2 and HOXA10 may be of prognostic relevance in squamous cell carcinoma (SCC) patients. In conclusion, we identified a large number of tumor-specifically methylated genes in NSCLC patients. Expression of many of them is regulated by methylation. Moreover, HOXA2 and HOXA10 methylation may serve as prognostic parameters in SCC patients. Overall, our findings emphasize the impact of methylation on the pathogenesis of NSCLCs

Additional file 1: Table S1. of SPAG6 and L1TD1 are transcriptionally regulated by DNA methylation in non-small cell lung cancers

Description of NSCLC cell lines used in this study. Information about histology, origin and disease stage of donors was obtained from ATCC catalogue ( https://www.lgcstandards-atcc.org ). EGFR, KRAS and TP53 mutational status and MET amplification according to supplementary references (1–3). *activating EGFR mutation in exon 19 (E746-E749 del), **activating EGFR mutation in exon 21 (L858R). N/A, not available; wt, wildtype; mut, mutated. Table S2. Clinico-pathological characteristics of 983 NSCLC patients. Overview of gender, histology, stage of disease and ethnicity of NSCLC patients obtained from TCGA database and used for mutation and copy number changes analyses of SPAG6 and L1TD1 is shown. ADC, adenocarcinoma; SCC, squamous cell carcinoma. Clinical data based on Caleydo software version 16/04/14. Table S3. Primer sequences. Summary of oligonucleotide sequences used for mRNA expression, MS-HRM, BGS analyses and construction of pCMV6-GFP expression vector. Y, random integration of C or T in fwd primer; R, random integration of G or A in rev primer. Table S4. Methylation of SPAG6 and L1TD1 in tumor cells of other tumor types. *Morphology, histology and origin of cell lines according to ATCC catalogue ( https://www.lgcstandards-atcc.org ). Percentage of methylation was calculated as described previously (4). (DOCX 33 kb

Additional file 4: Figure S3. of SPAG6 and L1TD1 are transcriptionally regulated by DNA methylation in non-small cell lung cancers

SPAG6 and L1TD1 SNVs and deletions in NSCLC patients. TCGA LUAD and LUSC datasets were analysed with Caleydo software (version April 2014). Mutation of TP53 was used to demonstrate reliability of TCGA data analysis. ADC, adenocarcinoma patients; SCC, squamous carcinoma patients. (TIF 90 kb

Additional file 3: Figure S2. of SPAG6 and L1TD1 are transcriptionally regulated by DNA methylation in non-small cell lung cancers

Impact of SPAG6 and L1TD1 mRNA expression on OS of NSCLC patients. (A) A shorter OS of squamous cell carcinoma patients with low SPAG6 mRNA expression (N = 155) compared to high SPAG6 mRNA expression (N = 267) was observed. (B) Adenocarcinoma patients with low L1TD1 mRNA expression (N = 138) showed a shorter OS compared to adenocarcinoma patients with high L1TD1 mRNA expression (N = 350). Gene expression microarray datasets (Affymetrix IDs 210032_s_at and 219955_at) were analysed and Kaplan-Meier plots were generated using all datasets and default settings of KM plotter. The cut-off values for “low” and “high” SPAG6 and L1TD1 mRNA expression were automatically defined by KM plotter software (Version 2013). (TIF 50 kb

Additional file 2: Figure S1. of SPAG6 and L1TD1 are transcriptionally regulated by DNA methylation in non-small cell lung cancers

SPAG6 and L1TD1 mRNA expression in different datasets of TCGA database. SPAG6 and L1TD1 mRNA expression was analysed using IlluminaHiSeq RNAseq data from TCGA database. Datasets LUAD and LUSC (lung), BRCA (breast), COADREAD (colorectal), HNSC (head and neck), KIRC (kidney), LIHC (liver) and PRAD (prostate) were analysed. Normalized log2 mRNA expression values are shown. Each dot represents a single sample. (TIF 176 kb