Molecular Bases of Mechanisms Accounting for Drug Resistance in Gastric Adenocarcinoma

Preclinical evaluation of fenretinide against primary and metastatic intestinal type‑gastric cancer

In recent years there has been a decline in the incidence of gastric cancer, however the high mortality rate has remained constant. The present study evaluated the potential effects of the retinoid fenretinide on the viability and migration of two cell lines, AGS and NCI-N87, that represented primary and metastatic intestinal gastric cancer subtypes, respectively. It was determined that a similar2 dose of fenretinide reduced the viability of both the primary and metastatic cell lines. In addition, it was demonstrated that combined treatment with fenretinide and cisplatin may affect the viability of both primary and metastatic gastric cancer cells. Furthermore, a wound healing assay demonstrated an inhibitory effect for fenretinide on cell migration. As part of the characterization of the mechanism of action, the effect of fenretinide on reactive oxygen species production and lipid droplet content was evaluated, with the latter as an indirect means of assessing autophagy. These results support the hypothesis of combining using fenretinide with conventional therapies to improve survival rates in advanced or metastatic gastric cancer.

HER-2 positive gastric cancer: Current targeted treatments

Gastric cancer (GC) is highly metastatic and characterized by HER2 amplification. Aberrant HER2 expression drives metastasis, therapy resistance, and tumor recurrence. HER2 amplification contributes to drug resistance by upregulating DNA repair enzymes and drug afflux proteins, reducing drug efficacy. HER2 modulates transcription factors critical for cancer stem cell properties, further impacting drug resistance. HER2 activity is influenced by HER-family ligands, promoting oncogenic signaling. These features point to HER2 as a targetable driver in GC. This review outlines recent advances in HER2-mediated mechanisms and their upstream and downstream signaling pathways in GC. Additionally, it discusses preclinical research investigation that comprehends trastuzumab-sensitizing phytochemicals, chemotherapeutics, and nanoparticles as adjunct therapies. These developments hold promise for improving outcomes and enhancing the management of HER2-positive GC.

Tanshinone I Stimulates Pyroptosis of Cisplatin-Resistant Gastric Cancer Cells by Activating the NF-κB/Caspase-3(8)/GSDME Signaling Pathway

Cisplatin (DDP) resistance frequently occurs in gastric cancer (GC) therapy. Tanshinone I is a liposoluble phenanthraquinone compound present in the roots of Salvia miltiorrhiza Bunge (Danshen). In this study, we aimed to explore the effects of tanshinone I on modulating DDP resistance of GC cells in vitro and in vivo. DDP-resistant GC cell models (BGC823/DDP and SGC7901/DDP) were established, and their viability, proliferation, migration, lactate dehydrogenase activity, reactive oxygen species (ROS) generation, and pyroptosis were assessed after DDP treatment with or without tanshinone I. In addition, a mouse model with subcutaneously transplanted GC tumors was established to confirm the effects of tanshinone I and DDP on tumor growth and cell pyroptosis. The results revealed that tanshinone I inhibited DDP-resistant GC cell proliferation and migration; increased intracellular ROS levels; and activated cell pyroptosis by enhancing the levels of cleaved caspase-8, cleaved caspase-3, GSDME-NT, phospho-IKK-α/β, and nuclear factor kappa-B (NF-κB). GSDME knockdown weakened these effects of tanshinone I on DDP-resistant GC cells. Furthermore, DDP combined with tanshinone I inhibited the growth of subcutaneously transplanted GC tumors in mice by reducing cell proliferation and inducing pyroptosis. In conclusion, tanshinone I reversed DDP resistance of GC cells by stimulating pyroptosis, by activating NF-κB/caspase-3(8)/GSDME signaling pathway.

Emerging roles of circular RNAs in tumorigenesis, progression, and treatment of gastric cancer

With an estimated one million new cases reported annually, gastric cancer (GC) ranks as the fifth most diagnosed malignancy worldwide. The early detection of GC remains a major challenge, and the prognosis worsens either when patients develop resistance to chemotherapy or radiotherapy or when the cancer metastasizes. The precise pathogenesis underlying GC is not well understood, which further complicates its treatment. Circular RNAs (circRNAs), a recently discovered class of noncoding RNAs that originate from parental genes through "back-splicing", have been shown to play a key role in various biological processes in both eukaryotes and prokaryotes. CircRNAs have been linked to cardiovascular diseases, diabetes, hypertension, Alzheimer's disease, and the occurrence and progression of tumors. Prior studies have established that circRNAs play a crucial role in GC, impacting tumorigenesis, diagnosis, progression, and therapy resistance. This review aims to summarize how circRNAs contribute to GC tumorigenesis and progression, examine their roles in the development of drug resistance, discuss their potential as biotechnological drugs, and summarize their response to therapeutic drugs and microorganism in GC.

The role of p62 in cell death and survival of 5-fluorouracil and oxaliplatin-resistant colorectal cancer cells

The protein sequestosome 1 (p62/SQSTM1) is primarily known as a selective autophagy cargo receptor, but due to its multidomain structure, it also has roles in the ubiquitin-proteasome system, metabolism, cell death and survival signalling. The increase in p62 levels is detected in some types of cancers, including colorectal cancer (CRC). Chemoresistance is the main cause of high mortality rates of CRC patients. Since p62 can regulate both cell survival and death, it is a potential modulator of chemoresistance. The impact of p62 on molecular causes of chemoresistance in CRC cells is insufficiently analysed. Therefore, we aimed to determine the impact of p62 on apoptosis, RIPK1-pRIPK3 axis, and IL-8 levels in chemoresistant CRC cells. Our data revealed that p62 levels are higher in the 5-fluorouracil (5-FU)-resistant HCT116/FU subline compared to the parental cell line. 5-FU and oxaliplatin (OxaPt) treatment decreased p62 protein levels and it correlated with chemoresistance of HCT116 and DLD1 cell lines. The silencing of p62 increased CRC cell sensitivity to 5-FU and OxaPt, hence p62 is one of the factors supporting chemoresistance. The downregulation of p62 reduced the activation of caspase-3 and the levels of RIPK1 and pRIPK3. Furthermore, p62 silencing decreased the BAX/BCL2 ratio in the HCT116/FU subline and did not change the levels of apoptosis. Instead, p62 silencing reduced the amount of IL-8 protein. Our results show that p62 impacts chemoresistance by stimulating prosurvival signalling.

The ceramide synthase (CERS/LASS) family: Functions involved in cancer progression

INTRODUCTION

Ceramide synthases (CERSes) are also known longevity assurance (LASS) genes. CERSes play important roles in the regulation of cancer progression. The CERS family is expressed in a variety of human tumours and is involved in tumorigenesis. They are closely associated with the progression of liver, breast, cervical, ovarian, colorectal, head and neck squamous cell, gastric, lung, prostate, oesophageal, pancreatic and blood cancers. CERSes play diverse and important roles in the regulation of cell survival, proliferation, apoptosis, migration, invasion, and drug resistance. The differential expression of CERSes in tumour and nontumour cells and survival analysis of cancer patients suggest that some CERSes could be used as potential prognostic markers. They are also important potential targets for cancer therapy.

METHODS

In this review, we summarize the available evidence on the inhibitory or promotive roles of CERSes in the progression of many cancers. Furthermore, we summarize the identified upstream and downstream molecular mechanisms that may regulate the function of CERSes in cancer settings.

IL-15 armoring enhances the antitumor efficacy of claudin 18.2-targeting CAR-T cells in syngeneic mouse tumor models

Claudin 18.2 (CLDN18.2)-targeting chimeric antigen receptor (CAR)-modified T cells are one of the few cell therapies currently producing an impressive therapeutic effect in treating solid tumors; however, their long-term therapeutic efficacy is not satisfactory with a short duration of response. Transgenic expression of interleukin (IL)-15 has been reported to promote T-cell expansion, survival, and function and enhance the antitumor activity of engineered T cells in vitro and in vivo. Therefore, this study aimed to explore whether IL-15 modification would increase the antitumor activity of CLDN18.2-targeting CAR-modified T (CAR-T) cells in immunocompetent murine tumor models. CLDN18.2-specific CAR-T cells with (H9 CAR-IL15) or without transgenic IL-15 expression (H9 CAR) were generated by retroviral transduction of mouse splenic T cells. In vitro, compared with H9 CAR T cells, H9 CAR-IL15 T cells exhibited better expansion and viability in the absence of antigen stimulation, with a less differentiated and T-cell exhausted phenotype; although IL-15 modification did not affect the production of effector cytokines and cytotoxic activity in the short-term killing assay, it moderately improved the in vitro recursive killing activity of CAR-T cells against CLDN18.2-expressing tumor cells. In vivo, H9 CAR T cells showed no antitumor activity against CLDN18.2-expressing pancreatic tumors in immunocompetent mice without lymphodepleting pretreatment; however, H9 CAR-IL15 T cells produced significant tumor-suppressive effects. Furthermore, H9 CAR-IL15 T cells exhibited greater in vivo expansion and tumor infiltration when combined with lymphodepleting preconditioning, resulting in superior antitumor activity in two murine tumor models and a survival advantage in one tumor model. We further demonstrated that recurrent tumors following H9 CAR-IL15 T-cell therapy downregulated CLDN18.2 expression, suggesting immune escape through the selection of antigen-negative cells under persistent CAR-T-cell immune pressure. In conclusion, our findings provide preclinical evidence supporting the clinical evaluation of IL-15-expressing CLDN18.2 CAR-T cells in patients with CLDN18.2-positive tumors.

The critical role of circular RNAs in drug resistance in gastrointestinal cancers

Nowadays, drug resistance (DR) in gastrointestinal (GI) cancers, as the main reason for cancer-related mortality worldwide, has become a serious problem in the management of patients. Several mechanisms have been proposed for resistance to anticancer drugs, including altered transport and metabolism of drugs, mutation of drug targets, altered DNA repair system, inhibited apoptosis and autophagy, cancer stem cells, tumor heterogeneity, and epithelial-mesenchymal transition. Compelling evidence has revealed that genetic and epigenetic factors are strongly linked to DR. Non-coding RNA (ncRNA) interferences are the most crucial epigenetic alterations explored so far, and among these ncRNAs, circular RNAs (circRNAs) are the most emerging members known to have unique properties. Due to the absence of 5' and 3' ends in these novel RNAs, the two ends are covalently bonded together and are generated from pre-mRNA in a process known as back-splicing, which makes them more stable than other RNAs. As far as the unique structure and function of circRNAs is concerned, they are implicated in proliferation, migration, invasion, angiogenesis, metastasis, and DR. A clear understanding of the molecular mechanisms responsible for circRNAs-mediated DR in the GI cancers will open a new window to the management of GI cancers. Hence, in the present review, we will describe briefly the biogenesis, multiple features, and different biological functions of circRNAs. Then, we will summarize current mechanisms of DR, and finally, discuss molecular mechanisms through which circRNAs regulate DR development in esophageal cancer, pancreatic cancer, gastric cancer, colorectal cancer, and hepatocellular carcinoma.

The hypoxia-inducible factor-1α in stemness and resistance to chemotherapy in gastric cancer: Future directions for therapeutic targeting

Hypoxia-inducible factor-1α (HIF-1α) is a crucial mediator of intra-tumoral heterogeneity, tumor progression, and unresponsiveness to therapy in tumors with hypoxia. Gastric tumors, one of the most aggressive tumors in the clinic, are highly enriched in hypoxic niches, and the degree of hypoxia is strongly correlated with poor survival in gastric cancer patients. Stemness and chemoresistance in gastric cancer are the two root causes of poor patient outcomes. Based on the pivotal role of HIF-1α in stemness and chemoresistance in gastric cancer, the interest in identifying critical molecular targets and strategies for surpassing the action of HIF-1α is expanding. Despite that, the understanding of HIF-1α induced signaling in gastric cancer is far from complete, and the development of efficacious HIF-1α inhibitors bears various challenges. Hence, here we review the molecular mechanisms by which HIF-1α signaling stimulates stemness and chemoresistance in gastric cancer, with the clinical efforts and challenges to translate anti-HIF-1α strategies into the clinic.

PROPERTY: study protocol for a randomized, double-blind, multicenter placebo-controlled trial assessing neurotoxicity in patients with metastatic gastrointestinal cancer taking PHYCOCARE® during oxaliplatin-based chemotherapy

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) is one of the most common adverse effects of antineoplastic agents, ranging in prevalence from 19% to over 85%. Clinically, CIPN is a predominantly sensory neuropathy that may be accompanied by motor and autonomic changes of varying intensity and duration. The high prevalence of CIPN among cancer patients makes it a major problem for both patients and survivors, as well as for their health care providers, especially because there is currently no single effective method of preventing CIPN; moreover, the options for treating this syndrome are very limited. Phycocyanin, a biliprotein pigment and an important constituent of the blue-green algae Spirulina platensis, has been reported to possess significant antioxidant and radical-scavenging properties, offering protection against oxidative stress, which is one of the hypothetic mechanisms, between others, of CIPN occurrence.

METHODS

Our hypothesis is that phycocyanin may give protection against oxaliplatin-induced neuropathy in the treatment of gastrointestinal cancers. Our trial will be a randomized double-blind placebo-controlled study with 110 randomized patients suffering from metastatic gastrointestinal adenocarcinoma including esogastric, colorectal, and pancreatic cancers. Patients are being followed up in the gastroenterology or oncology departments of seven French hospitals.

DISCUSSION

Due to the neuropathy, patients need to avoid injury by paying careful attention to home safety; patients' physicians often prescribe over-the-counter pain medications. If validated, our hypothesis should help to limit neurotoxicity without the need to discontinue chemotherapy.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05025826. First published on August 27, 2021.

Evaluation of Drug Resistance in the Tamoxifen-treated MKN-45 Gastric Cancer Cell Line via the Epithelial-mesenchymal Transition Signaling Pathway

One of the major challenges in gastric cancer (GC) chemotherapy is the phenomenon of multi-drug resistance (MDR). The epithelial-mesenchymal transition (EMT) and its key molecules, transforming growth factor-β (TGFβ) and SMAD2, play a central role in MDR occurrence. Tamoxifen (TAM), a triphenylethylene derivative, can overcome MDR in human gastric cancers. The aim of this study was to investigate the effect of TAM on 5-FU resistance of GC by suppressing the TGFβ1/SMAD2 signaling pathway and EMT. The MKN-45 cell line was subjected to treatment with 5-FU, TAM and a combination of both. The MTT assay was used to investigate the cytotoxic effects of 5-FU and TAM, and the DNA laddering technique was used to assess DNA fragmentation and apoptosis. Real-time RT-PCR examined the change in gene expression in EMT-related genes (SNAI2, VIM, TGFβ1 and SMAD2). The results of the present study indicated that not only TAM treatment significantly decreased the IC50 of 5-FU (P≤0.05), but also the addition of TAM to 5-FU induced apoptosis in the MKN-45 cell line. Treatment with TAM and 5-FU significantly inhibited TGFβ1 and TGFβ1-induced expression of EMT markers (VIM and SNAI2) in MKN-45 cells (P≤0.05). The reduction of TGFβ1 targets downstream of the SMAD2 signaling pathway reversed the process of EMT and significantly increased the sensitivity of MKN-45 cells to 5-FU. The results of the present study suggested that reversal of EMT-mediated MDR via the TGFβ1/SMAD signaling pathway using TAM may be a potential new therapeutic strategy to overcome chemoresistance to 5-FU during GC chemotherapy.

Eriodictyol Suppresses Gastric Cancer Cells via Inhibition of PI3K/AKT Pathway

Gastric cancer (GC) is among the five most common malignancies worldwide. Traditional chemotherapy cannot efficiently treat the disease and faces the problems of side effects and chemoresistance. Polygoni orientalis Fructus (POF), with flavonoids as the main bioactive compounds, exerts anti-cancer potential. In this study, we compared the anti-GC effects of the main flavonoids from POF and investigated the anti-cancer effects of eriodictyol towards GC both in vitro and in vivo. CCK-8 assays were performed to examine the inhibitory effects of common flavonoids from POF on GC cell viability. Colony formation assays were used to determine cell proliferation after eriodictyol treatment. Cell cycle distribution was analyzed using flow cytometry. Induction of apoptosis was assessed with Annexin V/PI staining and measurement of related proteins. Anti-cancer effects in vivo were investigated using a xenograft mouse model. Potential targets of eriodictyol were clarified by network pharmacological analysis, evaluated by molecular docking, and validated with Western blotting. We found that eriodictyol exhibited the most effective inhibitory effect on cell viability of GC cells among the common flavonoids from POF including quercetin, taxifolin, and kaempferol. Eriodictyol suppressed colony formation of GC cells and induced cell apoptosis. The inhibitory effects of eriodictyol on tumor growth were also validated using a xenograft mouse model. Moreover, no obvious toxicity was identified with eriodictyol treatment. Network pharmacology analysis revealed that PI3K/AKT signaling ranked first among the anti-GC targets. The molecular docking model of eriodictyol and PI3K was constructed, and the binding energy was evaluated. Furthermore, efficient inhibition of phosphorylation and activation of PI3K/AKT by eriodictyol was validated in GC cells. Taken together, our results identify eriodictyol as the most effective anti-GC flavonoids from POF and the potential targets of eriodictyol in GC. These findings suggest that eriodictyol has the potential to be a natural source of anti-GC agents.

Expression of Chemoresistance-Associated ABC Proteins in Hepatobiliary, Pancreatic and Gastrointestinal Cancers

Simple Summary

One-third of the approximately 10 million deaths yearly caused by cancer worldwide are due to hepatobiliary, pancreatic, and gastrointestinal tumors. One primary reason for this high mortality is the lack of response of these cancers to pharmacological treatment. More than 100 genes have been identified as responsible for seven mechanisms of chemoresistance, but only a few of them play a critical role. These include ABC proteins (mainly MDR1, MRP1-6, and BCRP), whose expression pattern greatly determines the individual sensitivity of each tumor to pharmacotherapy.

Abstract

Hepatobiliary, pancreatic, and gastrointestinal cancers account for 36% of the ten million deaths caused by cancer worldwide every year. The two main reasons for this high mortality are their late diagnosis and their high refractoriness to pharmacological treatments, regardless of whether these are based on classical chemotherapeutic agents, targeted drugs, or newer immunomodulators. Mechanisms of chemoresistance (MOC) defining the multidrug resistance (MDR) phenotype of each tumor depend on the synergic function of proteins encoded by more than one hundred genes classified into seven groups (MOC1-7). Among them, the efflux of active agents from cancer cells across the plasma membrane caused by members of the superfamily of ATP-binding cassette (ABC) proteins (MOC-1b) plays a crucial role in determining tumor MDR. Although seven families of human ABC proteins are known, only a few pumps (mainly MDR1, MRP1-6, and BCRP) have been associated with reducing drug content and hence inducing chemoresistance in hepatobiliary, pancreatic, and gastrointestinal cancer cells. The present descriptive review, which compiles the updated information on the expression of these ABC proteins, will be helpful because there is still some confusion on the actual relevance of these pumps in response to pharmacological regimens currently used in treating these cancers. Moreover, we aim to define the MOC pattern on a tumor-by-tumor basis, even in a dynamic way, because it can vary during tumor progression and in response to chemotherapy. This information is indispensable for developing novel strategies for sensitization.

Inhibitory role of LINC00332 in gastric cancer progression through regulating cell EMT and stemness

OBJECTIVE

Gastric cancer (GC) is one of the most common lethal malignancies worldwide. The molecular mechanisms underlying GC early detection are poorly understood. Identifying potential coding and non-coding markers and related pathways in the GC progression is essential. Some Long non-coding RNAs (lncRNAs) reportedly play vital roles during gastric GC development. However, the clinical significance and biological function of LINC00332 in GC remain largely unclear.

METHODS

The gene expression patterns of GC from an RNAseq dataset (GSE122401) were retrieved from the Gene Expression Omnibus (GEO) database to recognize differentially expressed genes (DEGs) and lncRNAs (DELs) between normal and GC samples through several bioinformatic analysis. The expression of LINC00332 and MMP-13 as a target gene was quantified in fresh frozen tissues obtained from GC patients. In addition, we investigated the potential function of LINC00332 in silico and in vitro.

RESULTS

The expressions of LINC00332 and MMP-13 were significantly downregulated and upregulated in GC tissues, respectively. A significant inverse correlation between LINC00332 and MMP-13 mRNA expression was observed in tumor samples. The mRNA expression level of mesenchymal markers, stem cell factors, and MMP genes were significantly decreased after the LINC00332 ectopic expression, while epithelial markers expression was significantly increased. The LINC00332 overexpression markedly repressed proliferation, migration, and invasion and did not induce apoptosis in AGS cells. In addition, LINC00332 overexpression notably promoted the E-cadherin protein expression. Moreover, LINC00332 significantly decreased the cisplatin resistance.

CONCLUSION

Our findings indicated that LINC00332 may be a critical anti-EMT factor and provided a new efficient therapeutic strategy for GC treatment.

Comprehensive bioinformatic analysis reveals a cancer-associated fibroblast gene signature as a poor prognostic factor and potential therapeutic target in gastric cancer

BACKGROUND

Gastric cancer is one of the deadliest cancers, currently available therapies have limited success. Cancer-associated fibroblasts (CAFs) are pivotal cells in the stroma of gastric tumors posing a great risk for progression and chemoresistance. The poor prognostic signature for CAFs is not clear in gastric cancer, and drugs that target CAFs are lacking in the clinic. In this study, we aim to identify a poor prognostic gene signature for CAFs, targeting which may increase the therapeutic success in gastric cancer.

METHODS

We analyzed four GEO datasets with a network-based approach and validated key CAF markers in The Cancer Genome Atlas (TCGA) and The Asian Cancer Research Group (ACRG) cohorts. We implemented stepwise multivariate Cox regression guided by a pan-cancer analysis in TCGA to identify a poor prognostic gene signature for CAF infiltration in gastric cancer. Lastly, we conducted a database search for drugs targeting the signature genes.

RESULTS

Our study revealed the COL1A1, COL1A2, COL3A1, COL5A1, FN1, and SPARC as the key CAF markers in gastric cancer. Analysis of the TCGA and ACRG cohorts validated their upregulation and poor prognostic significance. The stepwise multivariate Cox regression elucidated COL1A1 and COL5A1, together with ITGA4, Emilin1, and TSPAN9 as poor prognostic signature genes for CAF infiltration. The search on drug databases revealed collagenase clostridium histolyticum, ocriplasmin, halofuginone, natalizumab, firategrast, and BIO-1211 as the potential drugs for further investigation.

CONCLUSIONS

Our study demonstrated the central role of extracellular matrix components secreted and remodeled by CAFs in gastric cancer. The gene signature we identified in this study carries high potential as a predictive tool for poor prognosis in gastric cancer patients. Elucidating the mechanisms by which the signature genes contribute to poor patient outcomes can lead to the discovery of more potent molecular-targeted agents and increase the therapeutic success in gastric cancer.

Acquisition of paclitaxel resistance modulates the biological traits of gastric cancer AGS cells and facilitates epithelial to mesenchymal transition and angiogenesis

PURPOSE

This study aims to develop a paclitaxel (PTX)-resistant gastric cancer AGS cells (AGS-R) and evaluate the mechanisms of drug resistance.

METHODS

AGS cells were successively treated with increasing PTX concentrations. Cross-resistance of established AGS-R, the molecular patterns of cell survival, evasion of apoptosis, epithelial-mesenchymal transition (EMT), and the angiogenic potential were evaluated.

RESULTS

AGS-R was induced within six months of PTX exposure. Extension of the treatment resulted in PTX-resistance beyond clinical levels. The established AGS-R showed resistance to vincristine and doxorubicin but not cisplatin. Upon induction of resistance, the expressions of MDR-1 (P < 0.001) and MRP-1 (P < 0.01) genes and proteins significantly increased. AGS-R cells had elevated levels of BCL-2, pro-CASP3, cleaved-NOTCH1, HES1, HEY1, NF-κB, PI3K, p-AKT, HIF-1α, Cyclin A, and B1 as compared with parental cells (at least P < 0.01). The protein levels of BAX, CASP3, P53, and P21 (at least P < 0.01) as well as intracellular ROS (P < 0.001) were reduced in AGS-R. A relative arrest at the G2/M phase (15.8 ± 0.75 vs. 26.7 ± 1.67) of the cell cycle and enrichment of AGS-R cells for CD44 marker (9 ± 0.6 vs. 1 ± 0.8) (P < 0.001) were detected by flow cytometry. While the E-cadherin expression was reduced (P < 0.001), the protein levels of Vimentin, N-cadherin, SLUG, and SNAIL were increased (at least P < 0.05). The angiogenic activity and release of VEGF and MMP2/9 were increased in AGS-R cells relative to the AGS line (P < 0.001).

CONCLUSION

AGS-R cells could bypass chemotherapy stress by expressing the genes coding for efflux pumps and altering some key signaling in favor of survival, EMT, and angiogenesis.

Helicobacter pylori-induced RASAL2 Through Activation of Nuclear Factor-κB Promotes Gastric Tumorigenesis via β-catenin Signaling Axis

BACKGROUND & AIMS

Helicobacter pylori infection is the predominant risk factor for gastric cancer. RAS protein activator like 2 (RASAL2) is considered a double-edged sword in carcinogenesis. Herein, we investigated the role of RASAL2 in response to H pylori infection and gastric tumorigenesis.

METHODS

Bioinformatics analyses of local and public databases were applied to analyze RASAL2 expression, signaling pathways, and clinical significance. In vitro cell culture, spheroids, patient-derived organoids, and in vivo mouse models were used. Molecular assays included chromatin immunoprecipitation, co-immunoprecipitation, Western blotting, quantitative polymerase chain reaction, and immunocyto/histochemistry.

RESULTS

H pylori infection induced RASAL2 expression via a nuclear factor-κB (NF-κB)-dependent mechanism whereby NF-κB was directly bound to the RASAL2 promoter activating its transcription. By gene silencing and ectopic overexpression, we found that RASAL2 upregulated β-catenin transcriptional activity. RASAL2 inhibited protein phosphatase 2A activity through direct binding with subsequent activation of the AKT/β-catenin signaling axis. Functionally, RASAL2 silencing decreased nuclear β-catenin levels and impaired tumor spheroids and organoids formation. Furthermore, the depletion of RASAL2 impaired tumor growth in gastric tumor xenograft mouse models. Clinicopathological analysis indicated that abnormal overexpression of RASAL2 correlated with poor prognosis and chemoresistance in human gastric tumors.

CONCLUSIONS

These studies uncovered a novel signaling axis of NF-κB/RASAL2/β-catenin, providing a novel link between infection, inflammation and gastric tumorigenesis.

Long non-coding RNA HNF1A-AS1 induces 5-FU resistance of gastric cancer through miR-30b-5p/EIF5A2 pathway

BACKGROUND

Gastric cancer (GC) is one of the leading causes of cancer-related deaths worldwide and chemoresistance is a major cause for its poor prognosis. Long non-coding RNAs (lncRNAs) are associated with cancer chemoresistance. The current study sought to explore the mechanism of lncRNA HNF1A antisense RNA 1 (HNF1A-AS1) in mediating 5-fluorouracil (5-FU) resistance of GC.

METHODS

qRT-PCR was performed to detect the expression level of HNF1A-AS1 in GC tissues and cells. Abnormal expression of HNF1A-AS1 in GC cells was induced by lentivirus infection. Protein levels of EIF5A2, E-Cadherin, Vimentin and N-Cadherin were detected using western blot. Competitive endogenous RNA (ceRNA) mechanisms were explored through luciferase assays and RNA immunoprecipitation (RIP) assays. Functional experiments of chemoresistance were performed by CCK-8 assays, colony formation assays and flow cytometry with the treatment of 5-FU. Mouse tumor xenograft assays were performed to verify the findings in vivo.

RESULTS

The findings showed HNF1A-AS1 was significantly upregulated in GC tissues especially in chemoresistance group. Findings from in vitro and in vivo experiments showed HNF1A-AS1 increased cell viability and proliferation, repressed apoptosis and promoted xenograft tumors growth in the presence of 5-FU. Mechanistic studies revealed HNF1A-AS1 promoted chemoresistance by facilitating epithelial mesenchymal transition (EMT) process through upregulating EIF5A2 expression and HNF1A-AS1 acted as a sponge of miR-30b-5p.

CONCLUSIONS

The findings from the current study showed HNF1A-AS1 promoted 5-FU resistance by acting as a ceRNA of miR-30b-5p and promoting EIF5A2-induced EMT process in GC. This indicates that HNF1A-AS1 is a potential therapeutic target for alleviating GC chemoresistance.

Tau and stathmin proteins in breast cancer: A potential therapeutic target

Breast cancer is the most common malignant neoplasm among women, responsible for 30% of all malignant tumours, and the second most significant reason of cancer fatality in women. Treatment failure and tumour recurrence are common outcomes of chemotherapy when patients develop multidrug resistance (MDR). New therapeutic methods like molecularly targeted therapeutic interventions need a thorough understanding of malignant tumour's molecular processes. Numerous studies published in the last few years indicate that stathmin and tubulin-associated units (tau) are upregulated in a range of human malignant tumours, suggesting that they may enhance the incidence and progression of malignancies. By promoting cancer cell reproduction, infiltration and generating drug resistance, these proteins aid in the disease's development. Existing information on the expression of tau protein and stathmin in breast cancer, as well as their involvement in treatment methods, is summarized in this literature review.

Drug Resistance and Endoplasmic Reticulum Stress in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common and deadly cancers worldwide. It is usually diagnosed in an advanced stage and is characterized by a high intrinsic drug resistance, leading to limited chemotherapeutic efficacy and relapse after treatment. There is therefore a vast need for understanding underlying mechanisms that contribute to drug resistance and for developing therapeutic strategies that would overcome this. The rapid proliferation of tumor cells, in combination with a highly inflammatory microenvironment, causes a chronic increase of protein synthesis in different hepatic cell populations. This leads to an intensified demand of protein folding, which inevitably causes an accumulation of misfolded or unfolded proteins in the lumen of the endoplasmic reticulum (ER). This process is called ER stress and triggers the unfolded protein response (UPR) in order to restore protein synthesis or—in the case of severe or prolonged ER stress—to induce cell death. Interestingly, the three different arms of the ER stress signaling pathways have been shown to drive chemoresistance in several tumors and could therefore form a promising therapeutic target. This review provides an overview of how ER stress and activation of the UPR contributes to drug resistance in HCC.

Long Non-Coding RNA in Gastric Cancer: Mechanisms and Clinical Implications for Drug Resistance

Gastric cancer (GC) is the third leading cause of cancer-related deaths worldwide, with high recurrence and mortality rate. Chemotherapy, including 5-fluorouracil (5-FU), adriamycin (ADR), vincristine (VCR), paclitaxel (PTX), and platinum drugs, remains one of the fundamental methods of GC treatment and has efficiently improved patients’ prognosis. However, most patients eventually develop resistance to chemotherapeutic agents, leading to the failure of clinical treatment and patients’ death. Recent studies suggest that long non-coding RNAs (lncRNAs) are involved in the drug resistance of GC by modulating the expression of drug resistance-related genes via sponging microRNAs (miRNAs). Moreover, lncRNAs also play crucial roles in GC drug resistance via a variety of mechanisms, such as the regulation of the oncogenic signaling pathways, inhibition of apoptosis, induction of autophagy, modulation of cancer stem cells (CSCs), and promotion of the epithelial-to-mesenchymal transition (EMT) process. Some of lncRNAs exhibit great potential as diagnostic and prognostic biomarkers, as well as therapeutic targets for GC patients. Therefore, understanding the role of lncRNAs and their mechanisms in GC drug resistance may provide us with novel insights for developing strategies for individual diagnosis and therapy. In this review, we summarize the recent findings on the mechanisms underlying GC drug resistance regulated by lncRNAs. We also discuss the potential clinical applications of lncRNAs as biomarkers and therapeutic targets in GC.

Comprehensive analysis to identify DNA damage response-related lncRNA pairs as a prognostic and therapeutic biomarker in gastric cancer

OBJECTIVE

Gastric cancer (GC) is the fifth most common malignancy and the fourth leading cause of cancer-related mortality worldwide. The identification of valuable predictive signatures to improve the prognosis of patients with GC is becoming a realistic prospect. DNA damage response-related long noncoding ribonucleic acids (drlncRNAs) play an important role in the development of cancers. However, their prognostic and therapeutic values remain sparse in gastric cancer (GC).

METHODS

We obtained the transcriptome data and clinical information from The Cancer Genome Atlas Stomach Adenocarcinoma (TCGA-STAD) cohort. Co-expression network analyses were performed to discover functional modules using the igaph package. Subsequently, lncRNA pairs were identified by bioinformation analysis, and prognostic pairs were determined by univariate analysis, respectively. In addition, we utilized least absolute shrinkage and selection operator (LASSO) cox regression analysis to construct the risk model based on lncRNA pairs. Then, we distinguished between the high- or low- risk groups from patients with GC based on the optimal model. Finally, we reevaluated the association between risk score and overall survival, tumor immune microenvironment, specific tumor-infiltrating immune cells related biomarkers, and the sensitivity of chemotherapeutic agents.

RESULTS

32 drlncRNA pairs were obtained, and a 17-drlncRNA pairs signature was constructed to predict the overall survival of patients with GC. The ROC was 0.797, 0.812 and 0.821 at 1, 2, 3 years, respectively. After reclassifying these patients into different risk-groups, we could differentiate between them based on negative overall survival outcome, specialized tumor immune infiltration status, higher expressed immune cell related biomarkers, and a lower chemotherapeutics sensitivity. Compared with previous models, our model showed better performance with a higher ROC value.

CONCLUSION

The prognostic and therapeutic signature established by novel lncRNA pairs could provide promising prediction value, and guide individual treatment strategies in the future.

A review on the role of tau and stathmin in gastric cancer metastasis

Gastric cancer is resistant to chemotherapy, especially in the later stages. The prevalence of gastric cancer increases after the age of 40, and its peak is in the 7th decade of life. The proteins tau (tubulin associated unit) and stathmin are overexpressed in gastric cancer and contribute to the progression of the disease by increasing cancer cell proliferation, invasion, and inducing drug resistance. This review summarizes the current knowledge on the expression of tau protein and stathmin in gastric cancer and their roles in drug resistance. Medline and PubMed databases were searched from 1990 till February 2021 for the terms "tau protein", "stathmin", and "gastric cancer." Two reviewers screened all articles and assessed prognostic studies on the role of tau and stathmin proteins in gastric cancer progression. Collectively, studies reported that both proteins are expressed at different concentrations in gastric cancer and could be significant molecular biomarkers for prognosis. Both proteins could be good candidates for targeted therapy of gastric cancer and are associated with resistance to taxanes.

The Emerging Role of Liquid Biopsy in Gastric Cancer

(1) Background: Liquid biopsy (LB) is a novel diagnostic method with the potential of revolutionizing the prevention, diagnosis, and treatment of several solid tumors. The present paper aims to summarize the current knowledge and explore future possibilities of LB in the management of metastatic gastric cancer. (2) Methods: This narrative review examined the most recent literature on the use of LB-based techniques in metastatic gastric cancer and the current LB-related clinical trial landscape. (3) Results: In gastric cancer, the detection of circulating cancer cells (CTCs) has been recognized to have a prognostic role in all the disease stages. In the setting of localized disease, cell-free DNA (cfDNA) and circulating tumor DNA (ctDNA) qualitative and quantitative detection have the potential to inform on the risk of cancer recurrence and metastatic dissemination. In addition, gastric cancer-released exosomes may play an essential part in metastasis formation. In the metastatic setting, the levels of cfDNA show a positive correlation with tumor burden. There is evidence that circulating tumor microemboli (CTM) in the blood of metastatic patients is an independent prognostic factor for shorter overall survival. Gastric cancer-derived exosomal microRNAs or clonal mutations and copy number variations detectable in ctDNA may contribute resistance to chemotherapy or targeted therapies, respectively. There is conflicting and limited data on CTC-based PD-L1 verification and cfDNA-based Epstein-Barr virus detection to predict or monitor immunotherapy responses. (4) Conclusions: Although preliminary studies analyzing LBs in patients with advanced gastric cancer appear promising, more research is required to obtain better insights into the molecular mechanisms underlying resistance to systemic therapies. Moreover, validation and standardization of LB methods are crucial before introducing them in clinical practice. The feasibility of repeatable, minimally invasive sampling opens up the possibility of selecting or dynamically changing therapies based on prognostic risk or predictive biomarkers, such as resistance markers. Research is warranted to exploit a possible transforming area of cancer care.

Linc00641 promotes the progression of gastric carcinoma by modulating the miR-429/Notch-1 axis

Linc00641 plays different roles in various types of human cancers. However, the function of linc00641 and its underlying mechanism of action in gastric cancer have not been fully elucidated. Therefore, the aim of our current study was to explore the molecular mechanism of linc00641 in gastric cancer. MTT assays, flow cytometry, wound healing assays, and Transwell invasion assays were utilized to measure cell viability, apoptosis, migration and invasion, respectively. Western blotting and RT-PCR assays were carried out to explore the mechanism of linc00641 in gastric cancer cells. We found that silencing linc00641 suppressed the viability and stimulated the apoptosis of gastric cancer cells, while linc00641 overexpression had the opposite effects. Moreover, linc00641 sponged the expression of miR-429 and subsequently upregulated Notch-1 expression in gastric cancer cells. We concluded that linc00641 promoted the malignant progression of gastric cancer by modulating the miR-429/Notch-1 axis.

Lupeol and its derivatives as anticancer and anti-inflammatory agents: Molecular mechanisms and therapeutic efficacy

Lupeol is a natural triterpenoid that widely exists in edible fruits and vegetables, and medicinal plants. In the last decade, a plethora of studies on the pharmacological activities of lupeol have been conducted and have demonstrated that lupeol possesses an extensive range of pharmacological activities such as anticancer, antioxidant, anti-inflammatory, and antimicrobial activities. Pharmacokinetic studies have indicated that absorption of lupeol by animals was rapid despite its nonpolar characteristics, and lupeol belongs to class II BCS (biopharmaceutics classification system) compounds. Moreover, the bioactivities of some isolated or synthesized lupeol derivatives have been investigated, and these results showed that, with modification to C-3 or C-19, some derivatives exhibit stronger activities, e.g., antiprotozoal or anticancer activity. This review aims to summarize the advances in pharmacological and pharmacokinetic studies of lupeol in the last decade with an emphasis on its anticancer and anti-inflammatory activities, as well as the research progress of lupeol derivatives thus far, to provide researchers with the latest information, point out the limitations of relevant research at the current stage and the aspects that should be strengthened in future research.

Cellular Mechanisms Accounting for the Refractoriness of Colorectal Carcinoma to Pharmacological Treatment

Simple Summary

Colorectal cancer (CRC) causes a high number (more than 800,000) of deaths worldwide each year. Better methods for early diagnosis and the development of strategies to enhance the efficacy of the therapeutic approaches used to complement or substitute surgical removal of the tumor are urgently needed. Currently available pharmacological armamentarium provides very moderate benefits to patients due to the high resistance of tumor cells to respond to anticancer drugs. The present review summarizes and classifies into seven groups the cellular and molecular mechanisms of chemoresistance (MOC) accounting for the failure of CRC response to the pharmacological treatment.

Abstract

The unsatisfactory response of colorectal cancer (CRC) to pharmacological treatment contributes to the substantial global health burden caused by this disease. Over the last few decades, CRC has become the cause of more than 800,000 deaths per year. The reason is a combination of two factors: (i) the late cancer detection, which is being partially solved by the implementation of mass screening of adults over age 50, permitting earlier diagnosis and treatment; (ii) the inadequate response of advanced unresectable tumors (i.e., stages III and IV) to pharmacological therapy. The latter is due to the existence of complex mechanisms of chemoresistance (MOCs) that interact and synergize with each other, rendering CRC cells strongly refractory to the available pharmacological regimens based on conventional chemotherapy, such as pyrimidine analogs (5-fluorouracil, capecitabine, trifluridine, and tipiracil), oxaliplatin, and irinotecan, as well as drugs targeted toward tyrosine kinase receptors (regorafenib, aflibercept, bevacizumab, cetuximab, panitumumab, and ramucirumab), and, more recently, immune checkpoint inhibitors (nivolumab, ipilimumab, and pembrolizumab). In the present review, we have inventoried the genes involved in the lack of CRC response to pharmacological treatment, classifying them into seven groups (from MOC-1 to MOC-7) according to functional criteria to identify cancer cell weaknesses. This classification will be useful to pave the way for developing sensitizing tools consisting of (i) new agents to be co-administered with the active drug; (ii) pharmacological approaches, such as drug encapsulation (e.g., into labeled liposomes or exosomes); (iii) gene therapy interventions aimed at restoring the impaired function of some proteins (e.g., uptake transporters and tumor suppressors) or abolishing that of others (such as export pumps and oncogenes).