Oesophageal cancer: RNA editing of SLC22A3 mRNAs: causative relevance to familial ESCC?

SLC22A3 methylation-mediated gene silencing predicts adverse prognosis in acute myeloid leukemia

BACKGROUND

We screened out several hypermethylated solute carrier (SLC) family genes in acute myeloid leukemia by reduced representation bisulfite sequencing. SLC22A3 encodes an organic cation transport protein, which is critical for drug transportation and cellular detoxification. SLC22A3 is significantly downregulated and associated with tumor progression and worse prognosis in a variety of solid tumors. However, there are no data available regarding the role of SLC22 in AML. This study aimed to explore the regulatory mechanism of DNA methylation on SLC22A3 expression, as well as its clinical significance in AML prognosis.

RESULTS

SLC22A3 was identified as the sole prognosis-associated gene among SLCs based on TCGA and Beat AML databases. Bone marrow mononuclear cells (BMMNCs) from AML, MDS patients, and healthy donors were enrolled in this study. SLC22A3 methylation was significantly increased in AML compared with controls and MDS patients; meanwhile, the expression level of SLC22A3 was decreased. SLC22A3 hypermethylation presented an obvious association with some specific clinical characteristics and affected the survival time of AML patients as an independent risk indicator. SLC22A3 expression changed regularly as the disease complete remissions and relapses. Demethylation drug 5-aza-2'-deoxycytidine (DAC) activated transcription and increased mRNA expression of SLC22A3 in leukemia cell lines and AML fresh BMMNCs. Knockdown of SLC22A3 in leukemia cells enhanced cell proliferation and suppressed cell apoptosis. Data from public programs were used for auxiliary screening of probable molecular mechanisms of SLC22A3 in the antileukemia effect.

CONCLUSIONS

Our results showed that increased methylation and decreased expression of SLC22A3 may be indicators of poor prognosis in AML. Methylation-silenced SLC22A3 expression may have potential guiding significance on antileukemia effect of DAC.

Epigallocatechin gallate stimulated histamine production and downregulated histamine H1 receptor in oral cancer cell lines expressing histidine decarboxylase

OBJECTIVES

Increased histamine production and the overexpression of receptors (H1R∼H4R) has been reported in several tumors. The effects of TGFβ1 and epigallocatechin gallate (EGCG) on histamine synthesizing enzymes (HDCs), and the histamine transporter systems and receptors were investigated in this study.

METHODS

Four oral cancer cell lines (HSC2, HSC3, HSC4, and SAS) were treated with or without TGFβ1 or EGCG for 24 h. The expression levels of HDC, SLC22A3, H1R∼H4R, and TAS2R14 were investigated by Western blotting. Histamine concentrations were determined using the enzyme immune assay. Bitter taste receptor (TAS2R14 and TAS2R39) mRNAs were investigated by RT-PCR.

RESULTS

Varying expression levels of HDC, SLC22A3, H1R∼H4R, and TAS2R14 were observed in the four cell lines, where histamine concentrations were found to be ∼500 fmol/ml in cell culture media and induced 2-2.5 times higher amounts of histamine following EGCG treatment. TGFβ1 increased HDC expression in three cell lines, SLC22A3 expression in three cell lines, H1R expression in two cell lines, H2R expression in three cell lines, H3R expression in three cell lines, and H4R expression in three cell lines. EGCG decreased HDC expression in all four cell lines, SLC22A3 expression in three expression, H1R expression in all four cell lines, H2R expression in two cell lines, H3R expression in three cell lines, and H4R expression in two cell lines.

CONCLUSIONS

EGCG upregulated histamine production and decreased the expression level of H1R in the oral cancer cell lines. It might prove useful for cancer therapy during histamine regulation.

The role of RNA editing enzyme ADAR1 in human disease

Adenosine deaminase acting on RNA (ADAR) catalyzes the posttranscriptional conversion of adenosine to inosine in double-stranded RNA (dsRNA), which can lead to the creation of missense mutations in coding sequences. Recent studies show that editing-dependent functions of ADAR1 protect dsRNA from dsRNA-sensing molecules and inhibit innate immunity and the interferon-mediated response. Deficiency in these ADAR1 functions underlie the pathogenesis of autoinflammatory diseases such as the type I interferonopathies Aicardi-Goutieres syndrome and dyschromatosis symmetrica hereditaria. ADAR1-mediated editing of endogenous coding and noncoding RNA as well as ADAR1 editing-independent interactions with DICER can also have oncogenic or tumor suppressive effects that affect tumor proliferation, invasion, and response to immunotherapy. The combination of proviral and antiviral roles played by ADAR1 in repressing the interferon response and editing viral RNAs alters viral morphogenesis and cell susceptibility to infection. This review analyzes the structure and function of ADAR1 with a focus on its position in human disease pathways and the mechanisms of its disease-associated effects. This article is categorized under: RNA in Disease and Development > RNA in Disease RNA Processing > RNA Editing and Modification RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.

Identification of loci of functional relevance to Barrett's esophagus and esophageal adenocarcinoma: Cross-referencing of expression quantitative trait loci data from disease-relevant tissues with genetic association data

Esophageal adenocarcinoma (EA) and its precancerous condition Barrett's esophagus (BE) are multifactorial diseases with rising prevalence rates in Western populations. A recent meta-analysis of genome-wide association studies (GWAS) data identified 14 BE/EA risk loci located in non-coding genomic regions. Knowledge about the impact of non-coding variation on disease pathology is incomplete and needs further investigation. The aim of the present study was (i) to identify candidate genes of functional relevance to BE/EA at known risk loci and (ii) to find novel risk loci among the suggestively associated variants through the integration of expression quantitative trait loci (eQTL) and genetic association data. eQTL data from two BE/EA-relevant tissues (esophageal mucosa and gastroesophageal junction) generated within the context of the GTEx project were cross-referenced with the GWAS meta-analysis data. Variants representing an eQTL in at least one of the two tissues were categorized into genome-wide significant loci (P < 5×10-8) and novel candidate loci (5×10-8 ≤ P ≤ 5×10-5). To follow up these novel candidate loci, a genetic association study was performed in a replication cohort comprising 1,993 cases and 967 controls followed by a combined analysis with the GWAS meta-analysis data. The cross-referencing of eQTL and genetic data yielded 2,180 variants that represented 25 loci. Among the previously reported genome-wide significant loci, 22 eQTLs were identified in esophageal mucosa and/or gastroesophageal junction tissue. The regulated genes, most of which have not been linked to BE/EA etiology so far, included C2orf43/LDAH, ZFP57, and SLC9A3. Among the novel candidate loci, replication was achieved for two variants (rs7754014, Pcombined = 3.16×10-7 and rs1540, Pcombined = 4.16×10-6) which represent eQTLs for CFDP1 and SLC22A3, respectively. In summary, the present approach identified candidate genes whose expression was regulated by risk variants in disease-relevant tissues. These findings may facilitate the elucidation of BE/EA pathophysiology.

Two-photon fluorescent probe for detection of nitroreductase and hypoxia-specific microenvironment of cancer stem cell

Hypoxia plays a crucial role in cancer progression, and it has great significance for monitoring hypoxic level in biosystems. Cancer stem cells (CSCs) represent a small population of tumour cells that regard as the key to seed tumours. The survival of CSCs depend on the tumour microenvironment, which is distinct region has the hypoxic property. Therefore, the detection of the hypoxic CSC niche plays a pivotal role in the destructing the 'soil' of CSCs, and eliminating CSCs population. Numerous one-photon excited fluorescent probes have been developed to indicate the hypoxic status in tumours through the detection of nitroreductase (NTR) level. However, the biomedical application of one-photon fluorescent probes is limited due to the poor tissue penetration. In the present work, we reported a two-photon fluorescent probe to detect the NTR in CSCs and monitor the hypoxic microenvironment in vivo. The two-photon fluorescent molecular probe with a hypoxic specific response group can be reduced by NTR under hypoxic conditions. We used the two-photon probe to detect the hypoxia status of 3D cultured-CSCs in vitro and in vivo CSCs' microenvironment in tumour. The two-photon absorption cross section extends fluorescent excitation spectra to the near infrared region, which dramatically promotes the tissue penetration for hypoxic microenvironment detection of CSC in vivo.