Chemoresistance In Gastric Cancer Research Articles

Baicalin enhances the chemotherapy sensitivity of oxaliplatin-resistant gastric cancer cells by activating p53-mediated ferroptosis

Gastric cancer is one of the most common malignant tumors, and chemotherapy is the main treatment for advanced gastric cancer. However, chemotherapy resistance leads to treatment failure and poor prognosis in patients with gastric cancer. Multidrug resistance (MDR) is a major challenge that needs to be overcome in chemotherapy. According to recent research, ferroptosis activation is crucial for tumor therapeutic strategies. In this work, we explored the solution to chemoresistance in gastric cancer by investigating the effects of the Chinese medicine monomer baicalin on ferroptosis. Baicalin with different concentrations was used to treat the parent HGC27 and drug-resistant HGC27/L cells of gastric cancer. Cell viability was measured by CCK8, and synergistic effects of baicalin combined with oxaliplatin were evaluated using Synergy Finder software. The effects of baicalin on organelles and cell morphology were investigated using projective electron microscopy. Iron concentration, MDA production and GSH inhibition rate were measured by colorimetry. ROS accumulation was detected by flow cytometry. The ferroptosis-related genes (IREB2, TfR, GPX4, FTH1), P53, and SLC7A11 were analysed by Western blot, and the expression differences of the above proteins between pretreatment and pretreatment of different concentrations of baicalin, were assayed in both parental HGC27 cells and Oxaliplatin-resistant HGC27/L cells. Mechanically, Baicalin disrupted iron homeostasis and inhibits antioxidant defense, resulting in iron accumulation, lipid peroxide aggregation, and specifically targeted and activated ferroptosis by upregulating the expression of tumor suppressor gene p53, thereby activating the SLC7A11/GPX4/ROS pathway mediated by it. Baicalin activates ferroptosis through multiple pathways and targets, thereby inhibiting the viability of oxaliplatin-resistant gastric cancer HGC27/L cells and enhancing the sensitivity to oxaliplatin chemotherapy.

N6-methyladenosine reader hnRNPA2B1 recognizes and stabilizes NEAT1 to confer chemoresistance in gastric cancer.

Chemoresistance is a major cause of treatment failure in gastric cancer (GC). Heterogeneous nuclear ribonucleoprotein A2B1 (hnRNPA2B1) is an N6-methyladenosine (m6A)-binding protein involved in a variety of cancers. However, whether m6A modification and hnRNPA2B1 play a role in GC chemoresistance is largely unknown. In this study, we aimed to investigate the role of hnRNPA2B1 and the downstream mechanism in GC chemoresistance. The expression of hnRNPA2B1 among public datasets were analyzed and validated by quantitative PCR (qPCR), Western blotting, immunofluorescence, and immunohistochemical staining. The biological functions of hnRNPA2B1 in GC chemoresistance were investigated both in vitro and in vivo. RNA sequencing, methylated RNA immunoprecipitation, RNA immunoprecipitation, and RNA stability assay were performed to assess the association between hnRNPA2B1 and the binding RNA. The role of hnRNPA2B1 in maintenance of GC stemness was evaluated by bioinformatic analysis, qPCR, Western blotting, immunofluorescence, and sphere formation assays. The expression patterns of hnRNPA2B1 and downstream regulators in GC specimens from patients who received adjuvant chemotherapy were analyzed by RNAscope and multiplex immunohistochemistry. Elevated expression of hnRNPA2B1 was found in GC cells and tissues, especially in multidrug-resistant (MDR) GC cell lines. The expression of hnRNPA2B1 was associated with poor outcomes of GC patients, especially in those who received 5-fluorouracil treatment. Silencing hnRNPA2B1 effectively sensitized GC cells to chemotherapy by inhibiting cell proliferation and inducing apoptosis both in vitro and in vivo. Mechanically, hnRNPA2B1 interacted with and stabilized long noncoding RNA NEAT1 in an m6A-dependent manner. Furthermore, hnRNPA2B1 and NEAT1 worked together to enhance the stemness properties of GC cells via Wnt/β-catenin signaling pathway. In clinical specimens from GC patients subjected to chemotherapy, the expression levels of hnRNPA2B1, NEAT1, CD133, and CD44 were markedly elevated in non-responders compared with responders. Our findings indicated that hnRNPA2B1 interacts with and stabilizes lncRNA NEAT1, which contribute to the maintenance of stemness property via Wnt/β-catenin pathway and exacerbate chemoresistance in GC.

Epigenetic modulation of cytokine expression in gastric cancer: influence on angiogenesis, metastasis and chemoresistance.

Cytokines are proteins that act in the immune response and inflammation and have been associated with the development of some types of cancer, such as gastric cancer (GC). GC is a malignant neoplasm that ranks fifth in incidence and third in cancer-related mortality worldwide, making it a major public health issue. Recent studies have focused on the role these cytokines may play in GC associated with angiogenesis, metastasis, and chemoresistance, which are key factors that can affect carcinogenesis and tumor progression, quality, and patient survival. These inflammatory mediators can be regulated by epigenetic modifications such as DNA methylation, histone protein modification, and non-coding RNA, which results in the silencing or overexpression of key genes in GC, presenting different targets of action, either direct or mediated by modifications in key genes of cytokine-related signaling pathways. This review seeks insight into the relationship between cytokine-associated epigenetic regulation and its potential effects on the different stages of development and chemoresistance in GC.

Targeting Ubiquitin-specific Protease 5 Overcomes Chemoresistance via Negatively Regulating p53 in Gastric Cancer.

Resistance to chemotherapy is a major obstacle in the clinical management of gastric cancer, and the mechanisms underlying chemoresistance remain largely unknown. This study aimed to investigate the involvement of ubiquitin-specific protease 5 (USP5), a deubiquitinating enzyme, in gastric cancer chemoresistance Methods: USP5 expression was analyzed in fifty paired gastric cancer and adjacent normal tissues, chemo-sensitive and chemo-resistant gastric cancer lines using quantitative ELISA. The role of USP5 was determined using loss-of-function and gainof- function methods. USP5-mediated downstream effectors were analyzed using biochemical methods focusing on p53. USP5 expression was comparable in tumors and normal in the majority of the cohort. Following chemotherapy treatment, USP5 expression significantly increased in gastric cancer cells, while p53 levels remained unaltered. Overexpression of USP5 amplified growth and migration while decreasing apoptosis induced by serum withdrawal across multiple gastric cancer cell lines. Conversely, USP5 knockdown effectively heightened gastric cancer sensitivity to paclitaxel and 5-FU treatments, particularly targeting chemo-resistant gastric cancer cells by inhibiting proliferation and migration and inducing apoptosis. Additionally, USP5 knockdown increased levels of p53 but not MDM2, increased p53 activity and increased transcription of p53 target genes. In contrast, USP5 overexpression decreased the level and activity of p53 and inhibited transcription of p53 target genes. The anti-proliferative, anti-migratory, and pro-apoptotic effects of USP5 were significantly diminished upon p53 depletion, highlighting the interplay between p53 and USP5 in regulating gastric cancer cell activities. Additionally, USP5 inhibition suppressed chemo-resistant gastric cancer cell migration via suppressing epithelial-mesenchymal transition (EMT) and RhoA activity. Targeting USP5 inhibition has emerged as a promising alternative therapeutic approach to overcoming chemoresistance in gastric cancer. Additionally, our study sheds light on the novel role of USP5 as a regulator of p53 in gastric cancer.

Investigation on the mechanism of the combination of eremias multiocellata and cisplatin in reducing chemoresistance of gastric cancer based on in vitro and in vivo experiments.

Cisplatin (DDP) is one of the important chemotherapy drugs for patients with advanced gastric cancer and metastasis, but its resistance is a bottleneck problem that affects clinical efficacy and patient survival. Eremias multiocellata (EM) is a traditional Chinese herbal medicine, which has been used in the treatment of precancerous lesions, gastric cancer, liver fibrosis, and other digestive diseases. However, the mechanism of reducing chemotherapy resistance to gastric cancer is still unclear. We used the MTT assay to evaluate the proliferative viability of gastric cancer parental cell line MKN45 and its drug-resistant cell line MKN45/DDP, and compared their drug-resistance indices. The migration and invasion abilities of MKN45/DDP drug-resistant cells were evaluated using the Transwell assay. Apoptosis in MKN45/DDP drug-resistant cells was detected using flow cytometry. The effect of a combination of EM and cisplatin on the levels of reactive oxygen species (ROS) and lipid peroxides (LPO) in cisplatin-resistant gastric cancer cells was detected using ROS fluorescent probes and a lipid peroxidation assay kit in conjunction with flow cytometry. The effect of EM combined with cisplatin on the level of iron ions was detected by fluorescence probe and confocal laser technique. Hematoxylin-eosin staining (HE staining) was used to detect the histopathologic morphology of drug-resistant gastric cancer in nude mice. Ferroptosis-related proteins were measured using immunohistochemistry. Real-time fluorescence quantitative polymerase chain reaction (RT-qPCR) was used to detect tumor drug resistance-related genes. The NF-κB/Snail pathway-related proteins, PI3K/AKT/mTOR pathway-related proteins, and drug resistance-related proteins were detected by Western blot. The results of in vitro and in vivo experiments showed that EM combined with DDP could effectively inhibit the migration and invasive ability of MKN45/DDP cells, as well as induce apoptosis of MKN45/DDP cells; the combination of the two drugs could significantly increase the levels of ROS, lipid peroxidation and divalent ferric ions in MKN45/DDP cells, at the same time reducing the levels of Ferroptosis-related proteins, which could induce Ferroptosis. In addition, EM combined with DDP can also exert the effect of reversing DDP resistance and increasing the sensitivity of gastric cancer drug-resistant cells to DDP by regulating the NF-κB/Snail signaling pathway, PI3K/AKT/mTOR signaling pathway, and the expression of drug resistance-related proteins and genes.

Chemotherapeutic Drugs Endow Gastric Cancer Mesenchymal Stem Cells with Stronger Tumor-Promoting Ability.

Gastric cancer (GC) is one of the most aggressive tumors and has a poor prognosis. It has been demonstrated that gastric cancer mesenchymal stem cells (GC-MSCs) can promote the progression, metastasis, and chemoresistance of GC through various mechanisms, but the effect of GC-MSCs on GC during chemotherapy is still unknown. In this study, flow cytometry, CCK8 assay, migration assay, colony formation assay, and western blot were conducted. We also analyzed GC patients from the cancer genome atlas (TCGA). Our results showed that GC-MSCs were resistant to 5-FU and Taxol at the IC50 concentration for GC cells, and 5-FU could promote the migration of GC-MSCs at low doses. Furthermore, the conditioned medium of GC-MSCs pretreated with chemotherapeutic drugs was more effective in promoting the proliferation, migration, and stemness of GC cell lines than the conditioned medium of GC-MSCs without chemotherapeutic drugs treatment. These effects were dependent on the activation of phosphorylated AKT (p-AKT) in GC cell lines. Correspondingly, the inhibition of p-AKT reversed the tumor-promoting effect of the conditioned medium of GC-MSCs pretreated with chemotherapeutic drugs. Additionally, the expression of AKT1 was higher in GC tissues than in both paracancerous tissues and normal tissues, and patients resistant to chemotherapy expressed more AKT1 compared to those who were sensitive. Taken together, our data demonstrated that GC-MSCs gained more tumor-promoting abilities during chemotherapy.

CDK5 promotes apoptosis and attenuates chemoresistance in gastric cancer via E2F1 signaling

BackgroundChemoresistance is a major clinical challenge that leads to tumor metastasis and poor clinical outcome. The mechanisms underlying gastric cancer resistance to chemotherapy are still unclear.MethodsWe conducted bioinformatics analyses of publicly available patient datasets to establish an apoptotic phenotype and determine the key pathways and clinical significance. In vitro cell models, in vivo mouse models, and numerous molecular assays, including western blotting, qRT-PCR, immunohistochemical staining, and coimmunoprecipitation assays were used to clarify the role of factors related to apoptosis in gastric cancer in this study. Differences between datasets were analyzed using the Student’s t-test and two-way ANOVA; survival rates were estimated based on Kaplan–Meier analysis; and univariate and multivariate Cox proportional hazards models were used to evaluate prognostic factors.ResultsBulk transcriptomic analysis of gastric cancer samples established an apoptotic phenotype. Proapoptotic tumors were enriched for DNA repair and immune inflammatory signaling and associated with improved prognosis and chemotherapeutic benefits. Functionally, cyclin-dependent kinase 5 (CDK5) promoted apoptosis of gastric cancer cells and sensitized cells and mice to oxaliplatin. Mechanistically, we demonstrate that CDK5 stabilizes DP1 through direct binding to DP1 and subsequent activation of E2F1 signaling. Clinicopathological analysis indicated that CDK5 depletion correlated with poor prognosis and chemoresistance in human gastric tumors.ConclusionOur findings reveal that CDK5 promotes cell apoptosis by stabilizing DP1 and activating E2F1 signaling, suggesting its potential role in the prognosis and therapeutic decisions for patients with gastric cancer.

Caveolin-1 mediates the utilization of extracellular proteins for survival in refractory gastric cancer

Despite advances in cancer therapy, the clinical outcome of patients with gastric cancer remains poor, largely due to tumor heterogeneity. Thus, finding a hidden vulnerability of clinically refractory subtypes of gastric cancer is crucial. Here, we report that chemoresistant gastric cancer cells rely heavily on endocytosis, facilitated by caveolin-1, for survival. caveolin-1 was highly upregulated in the most malignant stem-like/EMT/mesenchymal (SEM)-type gastric cancer cells, allowing caveolin-1-mediated endocytosis and utilization of extracellular proteins via lysosomal degradation. Downregulation of caveolin-1 alone was sufficient to induce cell death in SEM-type gastric cancer cells, emphasizing its importance as a survival mechanism. Consistently, chloroquine, a lysosomal inhibitor, successfully blocked caveolin-1-mediated endocytosis, leading to the marked suppression of tumor growth in chemorefractory gastric cancer cells in vitro, including patient-derived organoids, and in vivo. Together, our findings suggest that caveolin-1-mediated endocytosis is a key metabolic pathway for gastric cancer survival and a potential therapeutic target.

Androgen receptor promotes cell stemness via interacting with co-factor YAP1 in gastric cancer

Cancer stem cells (CSCs) have been proposed to explain tumor relapse and chemoresistance in various types of cancers, and androgen receptor (AR) has been emerged as a potential regulator of stemness in cancers. However, the underlying mechanism of AR-regulated CSCs properties and chemoresistance in gastric cancer (GC) remains unknown. Here, we shown that AR is upregulated in GC tissues and correlates with poor survival rate and CSCs phenotypes of GC patients. According to our experimental data, overexpression of AR upregulated the expression of CSCs markers and this was consistent with the result concluded from data analysis that the expression of AR was positively correlated with CD44 in GC patients. In addition, AR overexpression obviously enhanced the tumor sphere formation ability and chemoresistance of GC cells in vitro. Whereas these effects were attenuated by inhibition of AR. These results were further validated in vivo that MGC-803 cells overexpressing AR had stronger properties to initiate gastric tumorigenesis than the control cells, and inhibition of AR increased the chemosensitivity of GC cells. Mechanically, AR upregulated CD44 expression by directly binding to its promoter region and Yes-associated protein 1 (YAP1) served as the co-factor of AR, which was demonstrated by the fact that the promoting effects of AR on GC cells stemness were partially counteracted by YAP1 knockdown. Thus, this study revealed that AR facilitates CSCs properties and chemoresistance of GC cells via forming complex with YAP1and indicates a potential therapeutic approach to GC patients.

Predictive value of DNA methylation in the efficacy of chemotherapy for gastric cancer.

Gastric cancer (GC) is one of the most common causes of cancer-related death. Drug resistance in chemotherapy often occurs in patients with GC, leading to tumor recurrence and poor survival. DNA methylation is closely related to the development of cancer. To investigate the role of DNA methylation in chemotherapy resistance in GC patients, we conducted a comprehensive analysis using DNA methylation data and survival information obtained from The Cancer Genome Atlas. Univariate Cox analysis was performed to screen for differential DNA methylation of chemotherapy response in patients who did and did not receive chemotherapy. Multivariate Cox analysis was then performed to identify the independent prognostic genes. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were used to explore the biological function of the signature genes. Patients receiving adjuvant chemotherapy for GC survived longer. 308 differentially methylated genes were demonstrated to be associated with prognosis. Six genes were optimally chosed for establisehing the risk model, including C6orf222, CCNL1, CREBZF, GCKR, TFCP2, and VIPR2. It was constructed based on the DNA methylation levels of these six genes: risk score = 0.47123374*C6orf222 + 9.53554803*CCNL1 + 10.40234138* CREBZF + 0.07611856* GCKR + 18.87661557*TFCP2 - 0.46396254* VIPR2. According to the risk score, patients receiving chemotherapy were divided into high- and low-risk groups, and the prognosis of the two groups was compared. The high-risk group had a shorter survival; however, this association was not present in patients without chemotherapy. The accuracy and predictive efficacy of the risk score in predicting the 1-, 3-, and 5-year survival of patients was evaluated with the receiver operating characteristic curve. In patients receiving chemotherapy, the area under the curve of the risk score for 1-, 3-, and 5-year survival was 0.841, 0.72, and 0.734, respectively. In patients who did not receive chemotherapy, the area under the curve was 0.406, 0.585, and 0.585, respectively. A nomogram model was constructed based on the risk score and clinical indicators. The model showed good consistency in the predicted probabilities and actual probabilities. Gene Ontology functional enrichment of these candidate methylated genes showed the following molecular functions: RNA binding, protein binding, mRNA binding, and nucleic acid binding; that they were mediated mainly through the following cell components: nuclear speck, nucleoplasm, nucleus, catalytic step 2 spliceosome, and the transcription factor AP-1 complex; and that they were involved in the following biological processes: mRNA processing, mRNA splicing, and RNA polymerase II promoter transcription. The Kyoto Encyclopedia of Genes and Genomes pathway enrichment results revealed that the signaling pathways mainly enriched were transcriptional misregulation in cancer, spliceosome, and the IL-17 signaling pathway. Our work identifies a six DNA methylated expression signature as a promising biomarker of chemo-resistance in GC, which provides new insights into the development of new strategies to overcome chemo-resistance in GC.

Neddylation-dependent LSD1 destabilization inhibits the stemness and chemoresistance of gastric cancer

Histone lysine-specific demethylase 1 (LSD1) expression has been evaluated in multiple tumors, including gastric cancer (GC). However, the mechanisms underlying LSD1 dysregulation in GC remain largely unclear. In this study, neural precursor cell-expressed developmentally down-regulated protein 8 (NEDD8) was identified to be conjugated to LSD1 at K63 by ubiquitin-conjugating enzyme E2 M (UBE2M), and this neddylated LSD1 could promote LSD1 ubiquitination and degradation, leading to a decrease of GC cell stemness and chemoresistance. Herein, our findings revealed a novel mechanism of LSD1 neddylation and its contribution to decreasing GC cell stemness and chemoresistance. Taken together, our findings may whistle about the future application of neddylation inhibitors.

PICH Activates Cyclin A1 Transcription to Drive S-Phase Progression and Chemoresistance in Gastric Cancer.

PICH binds Pol II and ATF4 in an ATPase-dependent manner to form a transcriptional complex that promotes cyclin A1 expression, accelerates S-phase progression, and impairs 5-FU chemosensitivity in gastric cancer.

MiR-708–3p promotes gastric cancer progression through downregulating ETNK1

MicroRNAs (miRNAs) are small, evolutionarily conserved, non-coding RNAs playing a role in the proliferation, metastasis, apoptosis, chemo-sensitivity, and chemo-resistance of gastric cancer, as well as the stemness of gastric cancer stem cells. miR-708–3p induces gastric cancer cell chemo-resistance, but its actual role in gastric cancer progression remains unclear. This paper shows that miR-708–3p is upregulated in gastric cancer samples and that a high miR-708–3p expression in gastric cancer patients is associated with poor overall survival. Our functional study results indicate that miR-708–3p overexpression promotes gastric cancer cell proliferation and migration, inhibits cell apoptosis, and facilitates the transition from the G0/G1 to the G2/M phase. Furthermore, reducing miR-708–3p levels yielded opposite effects. Next, our in vivo experiments revealed that miR-708–3p advanced gastric cancer cell growth in nude mice. The underlying mechanism was the regulation of ethanolamine kinase 1 (ETNK1) expression by miR-708–3p, which bound to the 3′UTR of the ETNK1 gene in gastric cancer cells. Finally, the recovery assay results showed that ETNK1 overexpression could slow miR-708-3p-induced gastric cancer progression. In conclusion, we identified a new miR-708–3p/ETNK1 pathway involved in gastric cancer progression. These results may offer new targets for gastric cancer therapy and markers for gastric cancer prognosis.

Dampening HOTAIR sensitizes the gastric cancer cells to oxaliplatin through miR-195-5p and ABCG2 pathway.

Long non-coding RNAs (lncRNA) have an extensive role in the progression and chemoresistance of gastric cancer (GC). Deeply study the regulatory role of lncRNAs could provide potential therapeutic targets. The aim of this study is to explore the regulatory role of HOTAIR in the progression and oxaliplatin resistance of GC. The expression of HOTAIR in GC and cell lines were detected by using qRT-PCR. Cell proliferation and apoptosis were analysed by CCK-8, EdU incorporation and flow cytometry. Luciferase reporter assay was used to identify the interaction between HOTAIR and ABCG2 (ATP-binding cassette (ABC) superfamily G member 2, ABCG2) via miR-195-5p. The regulatory functions were verified by using molecular biology experiments. HOTAIR was significantly overexpressed in GC and associated with poor prognosis. Knock-down of HOTAIR inhibited the GC cells proliferation and oxaliplatin resistance, while overexpression of HOTAIR showed opposite functions. Further studies found that HOTAIR acted as a competing endogenous RNA (ceRNA) to absorb miR-195-5p and elevated the expression of ABCG2, which leads to resistance of GC cells to oxaliplatin. Taken together, our findings demonstrated that HOTAIR regulates ABCG2 induced resistance of GC to oxaliplatin through miR-195-5p signalling and illustrate the great potential of developing new therapeutic targets for GC patients.

ADAMTS12 promotes oxaliplatin chemoresistance and angiogenesis in gastric cancer through VEGF upregulation

BackgroundWhile ADAMTS12 (A disintegrin and metalloproteinase with thrombospondin motifs 12) has been established as an important regulator of gastrointestinal tumor development and angiogenic activity, the precise mechanistic functions of ADAMTS12 have yet to be fully clarified in gastric cancer (GC). Accordingly, this study was developed to explore the molecular functions of ADAMTS12 in GC and to examine its utility as a biomarker associated with chemoresistance and prognostic outcomes in this cancer type. MethodsThe ability of ADAMTS12 to modulate the proliferative, migratory, invasive, chemoresistant, and tube formation activity of tumor cells was assessed in vivo and in vitro through gain- and loss-of-function approaches. Correlations between ADAMTS12, CD31, and VEGF expression levels in GC patient tumor tissue samples from individuals that did and did not undergo neoadjuvant chemotherapy (NAC) treatment were analyzed via immunohistochemical staining. ResultsThese analyses revealed the ability of ADAMTS12 to promote in vivo and in vitro cellular proliferative and angiogenic activity, promoting the activation of ERK and the consequent upregulation of VEGF, thereby inducing angiogenesis and decreasing GC cell oxaliplatin sensitivity. A positive correlation between ADAMTS12 levels and both the expression of VEGF as well as the density of microvessels was observed in GC patient tumor tissues. Moreover, those GC patients exhibiting higher intratumoral ADAMTS12 expression exhibited worse responses to NAC treatment and worse overall survival outcomes. ConclusionsThese findings suggest that ADAMTS12 can modulate signaling via the MAPK/VEGF axis in GC cells to enhance tumor cell resistance to oxaliplatin treatment under hypoxic and normoxic conditions. Elevated ADAMTS12 levels can additionally predict vascular abnormalities, worse survival outcomes, and chemoresistance in patients with GC.

FAM64A aggravates proliferation, invasion, lipid droplet formation, and chemoresistance in gastric cancer: A biomarker for aggressiveness and a gene therapy target.

FAM64A is a mitogen-induced regulator of the metaphase and anaphase transition. Here, we found that FAM64A messenger RNA (mRNA) and protein expression levels were higher in gastric cancer tissue than in normal mucosa (p < .05). FAM64A methylation was negatively correlated with FAM64A mRNA expression (p < .05). The differentially expressed genes of FAM64A were mainly involved in digestion, potassium transporting or exchanging ATPase, contractile fibers, endopeptidase, and pancreatic secretion (p < .05). The FAM64A-related genes were principally categorized into ubiquitin-mediated proteolysis, cell cycle, chromosome segregation and mitosis, microtubule binding and organization, metabolism of amino acids, cytokine receptors, lipid droplet, central nervous system, and collagen trimer (p < .05). FAM64A protein expression was lower in normal gastric mucosa than intestinal metaplasia, adenoma, and primary cancer (p < .05), negatively correlated with older age, T stage, lymphatic and venous invasion, tumor, node, metastasis stage, and dedifferentiation (p < .05), and associated with a favorable overall survival of gastric cancer patients. FAM64A overexpression promoted proliferation, antiapoptosis, migration, invasion, and epithelial-mesenchymal transition via the EGFR/Akt/mTOR/NF-κB, while the opposite effect was observed for FAM64A knockdown. FAM64A also induced chemoresistance directly or indirectly through lipid droplet formation via ING5. These results suggested that upregulation of FAM64A expression might induce aggressive phenotypes, leading to gastric carcinogenesis and its subsequent progression. Thus, FAM64A could be regarded as a prognosis biomarker and a target for gene therapy.

RNautophagic regulation of DNMT3a-dependent DNA methylation by Linc00942 enhances chemoresistance in gastric cancer.

Energy balance has long been known to extend lifespans and inhibit carcinogenesis in multiple species by slowing age-related epigenetic changes while the underlying mechanisms remain largely unknown. Herein, we found that starvation activated autophagy to remodel the DNA methylation profile by inhibiting DNMT3a expression. Illumina Infinium MethylationEPIC BeadChip and dot blot assay were performed to quantify the global DNA methylation level. Protein-RNA interactions were validated through RNA immunoprecipitation and RNA pull-down assay. In vitro and in vivo experiments were carried out to testify the effect of DNMT3a on chemoresistance. Autophagy is impaired in chemoresistance which was associated with differential DNA methylation and could be reversed by DNMT3a inhibition. Autophagy activation decreases the expression of DNMT3a mRNA, accompanied with the downregulation of chemoresistance-related Linc00942. Knockdown of Linc00942 reduces DNMT3a expression and genome-wide DNA methylation while Linc00942 overexpression increased DNMT3a expression and correlated hypermethylation in cancer cells and primary tumour tissues. Mechanistically, Linc00942 recruits RNA methyltransferase METTL3 to stimulate N6-methyladenosine (m6A) deposit on DNMT3a transcripts, triggering IGF2BP3/HuR to recognize modified mRNA for reinforced stability. SQSTM1/p62 recruits Linc00942 for autophagic degradation which can be abrogated after autophagy inhibition by p62 knockdown or chloroquine treatment. Inhibition of autophagy increases Linc00942 expression to promote chemoresistance and autophagy activation or hypomethylating agent decitabine restores chemosensitivity by reducing global DNA methylation. Overall, this study identifies a novel methylation cascade linking impaired RNautophagy to global hypermethylation in chemoresistance, and provides a rationale for repurposing decitabine to overcome chemoresistance in cancer treatment.

Growth differentiation factor 15 induces cisplatin resistance through upregulation of xCT expression and glutathione synthesis in gastric cancer.

Gastric cancer is a common cancer worldwide, particularly in East Asia. Chemotherapy is used in adjuvant or palliative therapies for gastric cancer. However, subsequent chemoresistance often develops. Growth differentiation factor 15 (GDF15) links to several cancers, but its effect on chemoresistance in gastric cancer remains unclear. Here, we analyzed clinical samples from genetic databases and included patients with gastric cancer. We dissected the regulatory mechanism underlying GDF15-mediated resistance of cisplatin in human gastric cancer cells. We showed that GDF15 serum levels might be a valuable biomarker for predicting prognosis in gastric cancer. The expressions of GDF15 and its receptor glial cell-derived neurotrophic factor family receptor a-like (GFRAL) in gastric tumors are important for malignant progression. Moreover, GDF15 expression is increased in gastric cancer cells with cisplatin resistance, resulting from elevated intracellular glutathione (GSH) and antioxidant activities. Upregulated GDF15 could increase intracellular GSH content by activating the GFRAL-GCN2-eIF2α-ATF4 signaling, enhancing cystine-uptake transporter xCT expression, and contributing biosynthesis of GSH in human gastric cancer cells. In conclusion, our results indicate that GDF15 could induce chemoresistance by upregulating xCT expression and GSH biosynthesis in human gastric cancer cells. Targeting GDF15 could be a promising treatment method for gastric cancer progression.

Circular RNA circLRCH3 promotes oxaliplatin resistance in gastric cancer through the modulation of the miR-383-5p/FGF7 axis.

Gastric cancer (GC) is a common malignant tumor of the digestive system. Circular RNAs (circRNAs) play a vital role in tumorigenesis and chemoresistance. The current study aimed to explore the possible role and mechanism of circRNA leucine rich repeats and calponin homology domain containing 3 (circLRCH3) in GC chemoresistance. The levels of circLRCH3, microRNA-383-5p (miR-383-5p) and fibroblast growth factor 7 (FGF7) were determined by quantitative real-time PCR or Western blot. Cell Counting Kit-8 (CCK-8) assay was utilized to evaluate cell survival rate and proliferation ability. Colony formation, transwell and flow cytometry assays were used to assess cell proliferation, migration, invasion and apoptosis. The expression of multidrug resistance proteins was detected by Western blot. The binding relationship between miR-383-5p and circLRCH3/FGF7 was verified by dual-luciferase reporter assay or RNA immunoprecipitation assay. Xenograft assay was conducted to analyze the role of circLRCH3 in OXA resistance in vivo. CircLRCH3 and FGF7 levels were up-regulated, while miR-383-5p level was reduced in OXA-resistant GC tissues and cells. Depletion of circLRCH3 attenuated the resistance of OXA-resistant cells to OXA. CircLRCH3 silence reduced OXA resistance by regulating miR-383-5p. Besides, miR-383-5p elevated OXA sensitivity of GC cells by repressing FGF7. Moreover, the deletion of circLRCH3 increased OXA sensitivity in vivo. Knockdown of circLRCH3 alleviated OXA resistance of GC by modulating the miR-383-5p/FGF7 axis, which provided a promising therapeutic target for GC chemoresistance.

MSC-NPRA loop drives fatty acid oxidation to promote stemness and chemoresistance of gastric cancer

Cisplatin (CDDP)-based chemotherapy is the preferred treatment strategy for advanced stage gastric cancer (GC) patients. Despite the efficacy of chemotherapy, the development of chemoresistance negatively affects the prognosis of GC and the underlying mechanism remains poorly understood. Accumulated evidence suggests that mesenchymal stem cells (MSCs) play important roles in drug resistance. The chemoresistance and stemness of GC cells were observed by colony formation, CCK-8, sphere formation and flow cytometry assays. Cell lines and animal models were utilized to investigate related functions. Western blot, quantitative real-time PCR (qRT-PCR) and co-immunoprecipitation were used to explore related pathways. The results showed that MSCs improved the stemness and chemoresistance of GC cells and accounted for the poor prognosis of GC. Natriuretic peptide receptor A (NPRA) was upregulated in GC cells cocultured with MSCs and knockdown of NPRA reversed the MSC-induced stemness and chemoresistance. At the same time, MSCs could be recruited to GC by NPRA, which formed a loop. In addition, NPRA facilitated stemness and chemoresistance through fatty acid oxidation (FAO). Mechanistically, NPRA protected Mfn2 against protein degradation and promoted its mitochondrial localization, which consequently improved FAO. Furthermore, inhibition of FAO with etomoxir (ETX) attenuated MSC-induced CDDP resistance in vivo. In conclusion, MSC-induced NPRA promoted stemness and chemoresistance by upregulating Mfn2 and improving FAO. These findings help us understand the role of NPRA in the prognosis and chemotherapy of GC. NPRA may be a promising target to overcome chemoresistance.