Molecular Predictors of Gastric Neoplastic Progression

The immune microenvironment in gastric adenocarcinoma

Like most solid tumours, the microenvironment of epithelial-derived gastric adenocarcinoma (GAC) consists of a variety of stromal cell types, including fibroblasts, and neuronal, endothelial and immune cells. In this article, we review the role of the immune microenvironment in the progression of chronic inflammation to GAC, primarily the immune microenvironment driven by the gram-negative bacterial species Helicobacter pylori. The infection-driven nature of most GACs has renewed awareness of the immune microenvironment and its effect on tumour development and progression. About 75-90% of GACs are associated with prior H. pylori infection and 5-10% with Epstein-Barr virus infection. Although 50% of the world's population is infected with H. pylori, only 1-3% will progress to GAC, with progression the result of a combination of the H. pylori strain, host susceptibility and composition of the chronic inflammatory response. Other environmental risk factors include exposure to a high-salt diet and nitrates. Genetically, chromosome instability occurs in ~50% of GACs and 21% of GACs are microsatellite instability-high tumours. Here, we review the timeline and pathogenesis of the events triggered by H. pylori that can create an immunosuppressive microenvironment by modulating the host's innate and adaptive immune responses, and subsequently favour GAC development.

Magnesium-dependent Phosphatase (MDP) 1 is a Potential Suppressor of Gastric Cancer

BACKGROUND

Recurrence is the leading cause of treatment failure and death in patients with gastric cancer (GC). However, the mechanism underlying GC recurrence remains unclear, and prognostic markers are still lacking.

METHODS

We analyzed DNA methylation profiles in gastric cancer cases with shorter survival (<1 year) or longer survival (> 3 years), and identified candidate genes associated with GC recurrence. Then, the biological effects of these genes on gastric cancer were studied.

RESULTS

A novel gene, magnesium-dependent phosphatase 1 (mdp1), was identified as a candidate gene whose DNA methylation was higher in GC samples from patients with shorter survival and lower in patients with longer survival. MDP1 protein was highly expressed in GC tissues with longer survival time, and also had a tendency to be expressed in highly differentiated GC samples. Forced expression of MDP1 in GC cell line BGC-823 inhibited cell proliferation, whereas the knockdown of MDP1 protein promoted cell growth. Overexpression of MDP1 in BGC-823 cells also enhanced cell senescence and apoptosis. Cytoplasmic kinase protein c-Jun N-terminal kinase (JNK) and signal transducer and activator of transcription 3 (Stat3) were found to mediate the biological function of MDP1.

CONCLUSION

These results suggest that MDP1 protein suppresses the survival of gastric cancer cells and loss of MDP expression may benefit the recurrence of gastric cancer.

Gastric juice piR-1245: A promising prognostic biomarker for gastric cancer

Background

Emerging reports demonstrated that PIWI‐interacting RNAs (piRNAs) played an indispensable role in tumorigenesis. However, it still remains elusive whether piR‐1245 in gastric juice specific in stomach could be employed as a biomarker for gastric cancer (GC). The present work is aiming at exploring the possibility of piR‐1245 in gastric juice as a potential marker to judge for diagnosis and prognosis of gastric cancer.

Methods

Gastric juice was collected from 66 GC patients and 66 healthy individuals. Quantitative real‐time reverse transcriptase polymerase chain reaction (qRT‐PCR) was employed to measure the levels of piR‐1245 expression. Then, the pattern of piR‐1245 expression in gastric juice was determined between GC patients and healthy individuals. A receiver operating characteristic (ROC) curve was constructed for distinguishing GC from healthy individuals.

Results

Gastric juice piR‐1245 levels in GC were higher than those of controls (P < .0001). The value of area under ROC (AUC) was 0.885 (sensitivity, 90.9%; specificity, 74.2%; 95% confidence interval, 0.8286 to 0.9414). High gastric juice piR‐1245 expression was signally correlated with tumor size (P = .013) and TNM stage (P = .001). GC patients with high piR‐1245 expression in gastric juice exerted a poorer overall survival (OS) (P = .0152) and progression‐free survival (PFS) (P = .013). COX regression analysis verified that gastric juice piR‐1245 expression was an independent prognostic risk variable for OS (P < .05).

Conclusions

The current study suggested that piR‐1245 in gastric juice had the potential to be a useful biomarker for GC detection and prognosis prediction.

Association between Gastric Pathology and Hepatitis B Virus Infection in Patients with or without Helicobacter Pylori

Background:

In the recent years, hepatitis B virus (HBV) infection has been considered as a risk factor for gastric cancer, but further studies are required to confirm these claim. The present study was aimed to evaluate the correlation between gastric pathology (precancerous and cancerous conditions) with HBV infection in Helicobacter pylori (H. pylori) positive or negative patients.

Methods:

In this cross-sectional study, 728 patients under endoscopy examination in Yazd Shaheed Sadoughi Hospital between 2017 and 2018 were participated. Histopathological analysis was performed on gastric specimens. Hepatitis B surface antigen (HBsAg) in sera was detected by the enzyme-linked immunosorbent assay (ELISA). The relationship between gastric pathology and HBV infection were explored by logistic regression analysis.

Results:

Of 728 patients, HBsAg and H. pylori infection were detected in 83 and 408 patients, respectively. Sixty nine patients were co-infected with H. pylori/HBV. H. pylori infection detected in patients with HbsAg positive significantly more than those were negative for HbsAg (p=0.029). None of HBV/H. pylori co-infected patients did not have normal gastric tissue. A significant difference was seen in histopathology of gastric tissue between HBsAg positive patients with and without H. pylori infection (p<0.0001). The HBsAg was associated with histopathology of gastric (OR=21.56, 95℅CI=7.070-65.741, p<0.001) and as a risk factor for gastritis (OR=12.457, 95℅CI= 3.007-51.614, P=0.001) but no cancer (OR=2.127, 95℅CI=0.242-18.704, P=0.496).

Conclusion:

The HBV infection alone is associated with some precancerous lesions but is not correlated with gastric cancer. It can increase development of premalignant conditions and carcinoma significantly in H. pylori positive patients.

PRKDC is a prognostic marker for poor survival in gastric cancer patients and regulates DNA damage response

A hallmark of gastric cancer is the high rate of genomic instability associated with deregulation of DNA damage repair pathways. DNA-Dependent Protein Kinase Catalytic Subunit (PRKDC) is a key component of the non-homologous end-joining (NHEJ) pathway. By reanalyzing transcriptome data of 80 pairs of gastric cancer tumors and the adjacent normal tissues from non-treated patients, we identified PRKDC as the top upregulated DNA damage repair genes in gastric cancer. High expression of PRKDC is associated with poor survival of gastric cancer patients, and genomic amplification of the gene is frequently observed across most gastric cancer subtypes. Knockdown of PRKDC in gastric cell lines resulted in reduced proliferation and cell cycle arrest. Furthermore, we showed that loss of PRKDC induced DNA damage and enhanced gastric cancer cell chemosensitivity to DNA-damaging reagents. Together, our results suggest that PRKDC is a prognostic marker of poor survival and is a putative target to overcome chemoresistance in gastric cancer.

Aclidinium bromide inhibits the growth and metastasis of gastric cancer MKN‑28 cells via the PI3K signaling pathway

The present study investigated the effect and underling mechanisms of aclidinium bromide, a novel, inhaled long‑acting muscarinic antagonist, on the development of gastric cancer. Human gastric cancer MKN‑28 cells, as a model in vitro, were treated with aclidinium bromide and dimethyl sulfoxide. Cell Counting Kit‑8 assay, transwell assay and flow cytometry were used to assess cell proliferation, invasion/migration and apoptosis, respectively. In addition, western blotting was performed to determine the relative expression of proteins associated with apoptosis and the phosphatidylinositol‑3‑kinase (PI3K) signaling pathway. Optical density values of MKN‑28 cells were decreased in a time‑ and dose‑dependent manner in the aclidinium bromide treated group. Matrigel invasion analysis demonstrated the number of invasive cells were significantly decreased in the aclidinium bromide‑treated group when compared with the control group. Furthermore, aclidinium bromide led to the marked reduction of the number of MKN‑28 cells passing though the microwells of the transwell chamber. The expression levels of the anti‑apoptotic protein B‑cell lymphoma 2 (Bcl‑2) decreased, and the expression of pro‑apoptotic proteins active Caspase3 and Bcl‑2‑associated X protein increased concurrently following aclidinium bromide stimulation using western blotting. The phosphorylation of protein kinase B and mechanistic target of rapamycin were significantly inhibited in MKN‑28 cells treated with aclidinium bromide; and the activity of the downstream proteins such as p70S6K and Cyclin D1 were also significantly decreased. In conclusion, aclidinium bromide could inhibit gastric cancer cell proliferation and metastasis, which may be associated with the enhancement of apoptosis induced by the PI3K signaling pathway.

KDM5B demethylates H3K4 to recruit XRCC1 and promote chemoresistance

Chemotherapy is the main treatment for human cancers including gastric cancer. However, in response to chemotherapeutic drugs, tumor cells can develop drug resistance by reprogramming intracellular metabolic and epigenetic networks to maintain their intrinsic homeostasis. Previously, we have established cisplatin-resistant gastric cancer cells as a drug resistant model, and elucidated the XRCC1 as the core DNA repair mechanism of drug resistance. This study investigated the regulation of XRCC1 by lysine demethylase 5B (KDM5B) in drug resistance. We found that the methylation level of H3K4 decreased significantly in drug-resistant cells. The chemical inhibitor of H3K4 demethylases, JIB-04, restored the methylation of H3K4 and blocked the co-localization of XRCC1 and γH2AX, eventually improved drug sensitivity. We further found that the expression level of KDM5B increased significantly in drug-resistant cells. Knockdown of KDM5B increased the methylation level of H3K4 and blocked the localization of XRCC1 to the DNA damage site, leads to increased drug sensitivity. In the sensitive cells, overexpression of KDM5B suppressed H3K4 methylation levels, which resulted to resistance to cisplatin. Moreover, we found that the posttranslational modification of KDM5B is responsible for its high expression in drug-resistant cells. Through mass spectrometry screening and co-immunoprecipitation validation, we found that the molecular chaperone HSP90 forms a complex with KDM5B in drug resistance cells. Interestingly, HSP90 inhibitor 17-AAG induced KDM5B degradation in a time-and-dose-dependent manner, indicating that HSP90 protected KDM5B from protein degradation. Targeting inhibition of HSP90 and KDM5B reversed drug resistance both in vitro and in vivo. Taken together, molecular chaperon HSP90 interacted with KDM5B to protect it from ubiquitin-dependent proteasomal degradation. Increased KDM5B demethylated H3K4 and facilitated the recruitment of XRCC1 to repair damaged DNA. Therefore, inhibition of HSP90 or KDM5B represented a novel approach to reverse chemoresistance in human cancers.