HOTTIP Predicts Poor Survival in Gastric Cancer Patients and Contributes to Cisplatin Resistance by Sponging miR-216a-5p

Role of Epigenetics for the Efficacy of Cisplatin

The clinical utility of the chemotherapeutic agent cisplatin is restricted by cancer drug resistance, which is either intrinsic to the tumor or acquired during therapy. Epigenetics is increasingly recognized as a factor contributing to cisplatin resistance and hence influences drug efficacy and clinical outcomes. In particular, epigenetics regulates gene expression without changing the DNA sequence. Common types of epigenetic modifications linked to chemoresistance are DNA methylation, histone modification, and non-coding RNAs. This review provides an overview of the current findings of various epigenetic modifications related to cisplatin efficacy in cell lines in vitro and in clinical tumor samples. Furthermore, it discusses whether epigenetic alterations might be used as predictors of the platinum agent response in order to prevent avoidable side effects in patients with resistant malignancies. In addition, epigenetic targeting therapies are described as a possible strategy to render cancer cells more susceptible to platinum drugs.

MALAT1 promotes FOXA1 degradation by competitively binding to miR-216a-5p and enhancing neuroendocrine differentiation in prostate cancer

OBJECTIVES

Prostate cancer (PC) is a leading cause of cancer-related death in males worldwide. Neuroendocrine differentiation (NED) is a feature of PC that often goes undetected and is associated with poor patient outcomes. Long non-coding RNAs (lncRNAs), microRNAs (miRNAs/miRs), and messenger RNAs (mRNAs) play important roles in the development and progression of PC.

METHODS

In this study, we used transcriptome sequencing and bioinformatics analysis to identify key regulators of NED in PC. Specifically, we examined the expression of PC-related lncRNAs, miRNAs, and mRNAs in PC cells and correlated these findings with NED phenotypes.

RESULTS

Our data revealed that metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and zinc finger protein 91 (ZFP91) were upregulated in PC, while miR-216a-5p was down-regulated. Ectopic expression of MALAT1 induced NED and promoted malignant phenotypes of PC cells. Furthermore, we found that MALAT1 competitively bound to miR-216a-5p, upregulated ZFP91, and promoted the degradation of forkhead box A1 (FOXA1), a key gene involved in NED of PC.

CONCLUSION

Taken together, these results suggest that MALAT1 plays an oncogenic role in NED and metastasis of PC via the miR-216a-5p/ZFP91/FOXA1 pathway. Our study highlights the potential of targeting this pathway as a novel therapeutic strategy for PC.

Tumor-derived exosome ElNF1-AS1 affects the progression of gastric cancer by promoting M2 polarization of macrophages

BACKGROUND

This study attempted to investigate the role of exosome ELFN1-AS1 in gastric cancer (GC).

METHODS

The study used various techniques to determine the level of exosomal ELFN1-AS1 in GC tissue and cells, including quantitative real-time PCR. Pull-down assay and dual-luciferase reporter assay were employed to identify interactions between ELFN1-AS1 and miR-4644, as well as miR-4644 and PKM. Western blot was employed to explore the potential regulatory mechanism. Several in vitro assays were conducted in xenograft models to investigate the impacts of exosomal ELFN1-AS1 on GC development, metastasis and macrophage polarization.

RESULTS

ELFN1-AS1 was upregulated in GC tissue and cells, with high enrichment in GC-derived exosomes. Exosomal ELFN1-AS1 enhances the cell abilities and stemness of GC. ELFN1-AS1 targeted and regulated miR-4644, which triggered PKM expression. Exosomal ELFN1-AS1 modulated glycolysis via PKM in an HIF-1α dependent manner in GC, promoting M2 polarization and macrophage recruitment. Furthermore, exosomal ELFN1-AS1 enhanced GC cell growth, metastasis and M2 polarization in vivo.

CONCLUSIONS

The study suggests that ELFN1-AS1 could be a promising biomarker for the diagnosis and treatment of GC.

Regulatory miRNAs in cancer cell recovery from therapy exposure and its implications as a novel therapeutic strategy for preventing disease recurrence

The desired outcome of cancer therapies is the eradication of disease. This can be achieved when therapy exposure leads to therapy-induced cancer cell death as the dominant outcome. Theoretically, a permanent therapy-induced growth arrest could also contribute to a complete response, which has the potential to lead to remission. However, preclinical models have shown that therapy-induced growth arrest is not always durable, as recovering cancer cell populations can contribute to the recurrence of cancer. Significant research efforts have been expended to develop strategies focusing on the prevention of recurrence. Recovery of cells from therapy exposure can occur as a result of several cell stress adaptations. These include cytoprotective autophagy, cellular quiescence, a reversable form of senescence, and the suppression of apoptosis and necroptosis. It is well documented that microRNAs regulate the response of cancer cells to anti-cancer therapies, making targeting microRNAs therapeutically a viable strategy to sensitization and the prevention of recovery. We propose that the use of microRNA-targeting therapies in prolonged sequence, that is, a significant period after initial therapy exposure, could reduce toxicity from the standard combination strategy, and could exploit new epigenetic states essential for cancer cells to recover from therapy exposure. In a step toward supporting this strategy, we survey the available scientific literature to identify microRNAs which could be targeted in sequence to eliminate residual cancer cell populations that were arrested as a result of therapy exposure. It is our hope that by successfully identifying microRNAs which could be targeted in sequence we can prevent disease recurrence.

Characterization of the m6A regulator-mediated methylation modification patterns in oral squamous cell carcinoma

N⁶-methyladenosine (m⁶A) is a form of posttranscriptional modification that plays important roles in cancer including oral squamous cell carcinoma (OSCC). Most studies to date have focused on a limited number of regulators and oncogenic pathways, thus failing to provide comprehensive insight into the dynamic effects of m⁶A modification. In addition, the role of m⁶A modification in shaping immune cell infiltration in OSCC has yet to be clarified. This study was designed to assess m⁶A modification dynamics in OSCC and to understand how such modifications influence clinical immunotherapeutic treatment outcomes. m⁶A modification patterns linked with 23 m⁶A regulators were analyzed in 437 OSCC patients from TCGA and GEO cohorts. These patterns were then quantified through m⁶A score based on algorithms derived from a principal component analysis (PCA) approach. The m⁶A modification patterns of OSCC samples were grouped into two clusters based on the m⁶A regulators expression, and immune cell infiltration was linked with the 5-year survival outcomes of patients in these clusters. 1575 genes associated with OSCC patient prognosis were identified and used to re-cluster these samples into two groups. Patients in clusters exhibiting higher levels of m⁶A regulator expression exhibited poorer overall survival (OS), whereas patients with high m⁶A scores survived for longer (p < 0.001). The overall mortality rates in the groups of patients with low and high m⁶A scores were 55% and 40%, respectively, and the m⁶A score distributions in clusters of patients grouped by m⁶A modification patterns and gene expression further supported the link between a high m⁶A score and better prognostic outcomes. Immunophenoscore (IPS) values for patients in different m⁶A score groups suggested that the use of PD-1-specific antibodies or CTLA-4 inhibitors alone or in combination would yield superior treatment outcomes in patients in the high-m⁶A score group relative to the low-m⁶A score group. m⁶A modification patterns are relevant to heterogeneity in OSCC. Detailed analyses of m⁶A modification patterns may thus offer novel insight regarding immune cell infiltration within the OSCC tumor microenvironment, guiding novel efforts to provide patients with more effective immunotherapeutic interventions.

Molecular mechanisms of microRNA-216a during tumor progression

MicroRNAs (miRNAs) as the members of non-coding RNAs family are involved in post-transcriptional regulation by translational inhibiting or mRNA degradation. They have a critical role in regulation of cell proliferation and migration. MiRNAs aberrations have been reported in various cancers. Considering the importance of these factors in regulation of cellular processes and their high stability in body fluids, these factors can be suggested as suitable non-invasive markers for the cancer diagnosis. MiR-216a deregulation has been frequently reported in different cancers. Therefore, in the present review we discussed the molecular mechanisms of the miR-216a during tumor progression. It has been reported that miR-216a mainly functioned as a tumor suppressor through the regulation of signaling pathways and transcription factors. This review paves the way to suggest the miR-216a as a probable therapeutic and diagnostic target in cancer patients.

HOX cluster-embedded lncRNAs and epithelial-mesenchymal transition in cancer: Molecular mechanisms and therapeutic opportunities

Although there has been substantial improvement in the treatment modalities, cancer remains the major cause of fatality worldwide. Metastasis, recurrence, and resistance to oncological therapies are the leading causes of cancer mortality. Epithelial-mesenchymal transition (EMT) is a complex biological process that allows cancer cells to undergo morphological transformation into a mesenchymal phenotype to acquire invasive potential. It encompasses reversible and dynamic ontogenesis by neoplastic cells during metastatic dissemination. Hence, understanding the molecular landscape of EMT is imperative to identify a reliable clinical biomarker to combat metastatic spread. Accumulating evidence reveals the role of HOX (homeobox) cluster-embedded long non-coding RNAs (lncRNAs) in EMT and cancer metastasis. They play a crucial role in the induction of EMT, modulating diverse biological targets. The present review emphasizes the involvement of HOX cluster-embedded lncRNAs in EMT as a molecular sponge, chromatin remodeler, signaling regulator, and immune system modulator. Furthermore, the molecular mechanisms behind therapy resistance and the potential use of novel drugs targeting HOX cluster-embedded lncRNAs in the clinical management of distant metastasis will be discussed.

Regulation of autophagy by non-coding RNAs in gastric cancer

Autophagy is a conserved cellular self-digesting process that degrades obsoleting proteins and cellular components and plays a crucial role in the tumorigenesis, metastasis, and drug resistance of various tumors such as gastric cancer (GC). As a hotspot in molecular biology, non-coding RNAs (ncRNAs) are involved in the regulation of multiple biological processes, such as autophagy. Increasing evidence indicate that various ncRNAs exert double roles in the initiation and progression of GC, either serve as oncogenes or tumor suppressors. Recent studies have shown that some ncRNAs could modulate autophagy activity in GC cells, which would affect the malignant transformation and drug resistance. Whether the function of ncRNAs in GC is dependent on autophagy is undefined. Therefore, identifying the underlying moleculr targets of ncRNAs in autophagy pathways and the role of ncRNA-regulated autophagy in GC could develop new treatment interventions for this disease. This review summarizes the autophagy process and its role in GC, and the regulatory mechanisms of ncRNAs, as well as focuses on the dual role of ncRNAs-mediated autophagy in GC, for the development of potential therapeutic strategies in GC patients.

lncRNA HOTTIP Recruits EZH2 to Inhibit PTEN Expression and Participates in IM Resistance in Chronic Myeloid Leukemia

Objective

To investigate that HOTTIP suppressed PTEN gene expression and was involved in IM resistance in chronic myeloid leukemia through recruitment of EZH2 protein.

Methods

Seventy-one cases of bone marrow monocytes diagnosed with CML in the Second Hospital of Hebei Medical University from 2018 to 2021 were selected. These patients were diagnosed with CML by bone marrow morphology, immunology, molecular biology, and cytogenetics, of which 36 were sensitive to IM and 35 were resistant to IM. We selected K562 and IR-K562 cells preserved in the laboratory as our subjects to study the expression levels of HOTTIP in the bone marrow cells of IM CML-resistant patients and IM-resistant cells.

Results

In this study, we found that HOTTIP was highly expressed in the bone marrow and cell lines of CML patients resistant to Imatinib mesylate (IM). In in vitro experiments, lentiviral knockdown of HOTTIP inhibited CML cell proliferation and promoted apoptosis, and knockdown of HOTTIP also increased sensitivity to IM. Mechanistically, highly expressed HOTTIP is involved in the biological process of IM resistance by recruiting Zeste homologous protein 2 enhancer (EZH2) to inhibit the expression of phosphatase and Tensin homologous protein (PTEN) genes.

Conclusions

We confirmed that HOTTIP and EZH2 are highly expressed in IM-resistant patients and IM-resistant CML cell lines. In CML cell lines, HOTTIP is involved in regulating the proliferation and apoptosis of CML cells and resistance to IM.

Long Non-Coding RNA HOTTIP is Elevated in Patients with Sepsis and Promotes Cardiac Dysfunction

BACKGROUND

Cardiac dysfunction is the most common clinical complication of sepsis. Herein, the study explored the clinical importance of long non-coding RNA (lncRNA) HOXA terminal transcript antisense RNA (HOTTIP) in the onset of sepsis and the development of cardiac dysfunction.

METHODS

120 patients with sepsis were recruited and divided into cardiac dysfunction group and non-cardiac dysfunction group. Serum HOTTIP levels were measured via RT-qPCR. AC16 cells were treated with lipopolysaccharide (LPS) for cell experiments and detected for cell viability and apoptosis.

RESULTS

High serum HOTTIP levels were tested in sepsis patients, which was associated with procalcitonin (PCT) level. Serum HOTTIP can identify sepsis cases from healthy people with the AUC of 0.927. 72 cases developed into cardiac dysfunction, accompanied by elevated levels of HOTTIP. ROC curve displayed the predictive ability of serum HOTTIP in the development of cardiac dysfunction in patients with sepsis. After adjusting for other clinical parameters, HOTTIP can independently affect the development of cardiac dysfunction. In vitro, HOTTIP knockdown promoted the recovery of cell viability and reversed LPS-induced cell apoptosis and excessive interleukin-6 (IL-6) release.

CONCLUSION

LncRNA HOTTIP is closely related to the condition of patients with sepsis and the development of cardiac dysfunction, possibly owing to its function in LPS-induced myocardial apoptosis and inflammation.

Epigenetic regulation of autophagy in gastrointestinal cancers

The development of novel therapeutic approaches is necessary to manage gastrointestinal cancers (GICs). Considering the effective molecular mechanisms involved in tumor growth, the therapeutic response is pivotal in this process. Autophagy is a highly conserved catabolic process that acts as a double-edged sword in tumorigenesis and tumor inhibition in a context-dependent manner. Depending on the stage of malignancy and cellular origin of the tumor, autophagy might result in cancer cell survival or death during the GICs' progression. Moreover, autophagy can prevent the progression of GIC in the early stages but leads to chemoresistance in advanced stages. Therefore, targeting specific arms of autophagy could be a promising strategy in the prevention of chemoresistance and treatment of GIC. It has been revealed that autophagy is a cytoplasmic event that is subject to transcriptional and epigenetic regulation inside the nucleus. The effect of epigenetic regulation (including DNA methylation, histone modification, and expression of non-coding RNAs (ncRNAs) in cellular fate is still not completely understood. Recent findings have indicated that epigenetic alterations can modify several genes and modulators, eventually leading to inhibition or promotion of autophagy in different cancer stages, and mediating chemoresistance or chemosensitivity. The current review focuses on the links between autophagy and epigenetics in GICs and discusses: 1) How autophagy and epigenetics are linked in GICs, by considering different epigenetic mechanisms; 2) how epigenetics may be involved in the alteration of cancer-related phenotypes, including cell proliferation, invasion, and migration; and 3) how epidrugs modulate autophagy in GICs to overcome chemoresistance.

Emerging roles of long noncoding RNAs in chemoresistance of pancreatic cancer

Pancreatic cancer is one of the most common causes of cancer death in the world due to the lack of early symptoms, metastasis occurrence and chemoresistance. Therefore, early diagnosis by detection of biomarkers, blockade of metastasis, and overcoming chemoresistance are the effective strategies to improve the survival of pancreatic cancer patients. Accumulating evidence has revealed that long noncoding RNA (lncRNA) and circular RNAs (circRNAs) play essential roles in modulating chemosensitivity in pancreatic cancer. In this review article, we will summarize the role of lncRNAs in drug resistance of pancreatic cancer cells, including HOTTIP, HOTAIR, PVT1, linc-ROR, GAS5, UCA1, DYNC2H1-4, MEG3, TUG1, HOST2, HCP5, SLC7A11-AS1 and CASC2. We also highlight the function of circRNAs, such as circHIPK3 and circ_0000284, in regulation of drug sensitivity of pancreatic cancer cells. Moreover, we describe a number of compounds, including curcumin, genistein, resveratrol, quercetin, and salinomycin, which may modulate the expression of lncRNAs and enhance chemosensitivity in pancreatic cancers. Therefore, targeting specific lncRNAs and cicrRNAs could contribute to reverse chemoresistance of pancreatic cancer cells. We hope this review might stimulate the studies of lncRNAs and cicrRNAs, and develop the new therapeutic strategy via modulating these noncoding RNAs to promote chemosensitivity of pancreatic cancer cells.

Contribution of MicroRNAs in Chemoresistance to Cisplatin in the Top Five Deadliest Cancer: An Updated Review

Cisplatin (DDP) is a well-known anticancer drug used for the treatment of numerous human cancers in solid organs, including bladder, breast, cervical, head and neck squamous cell, ovarian, among others. Its most important mode of action is the DNA-platinum adducts formation, inducing DNA damage response, silencing or activating several genes to induce apoptosis; these mechanisms result in genetics and epigenetics modifications. The ability of DDP to induce tumor cell death is often challenged by the presence of anti-apoptotic regulators, leading to chemoresistance, wherein many patients who have or will develop DDP-resistance. Cancer cells resist the apoptotic effect of chemotherapy, being a problem that severely restricts the successful results of treatment for many human cancers. In the last 30 years, researchers have discovered there are several types of RNAs, and among the most important are non-coding RNAs (ncRNAs), a class of RNAs that are not involved in protein production, but they are implicated in gene expression regulation, and representing the 98% of the human genome non-translated. Some ncRNAs of great interest are long ncRNAs, circular RNAs, and microRNAs (miRs). Accumulating studies reveal that aberrant miRs expression can affect the development of chemotherapy drug resistance, by modulating the expression of relevant target proteins. Thus, identifying molecular mechanisms underlying chemoresistance development is fundamental for setting strategies to improve the prognosis of patients with different types of cancer. Therefore, this review aimed to identify and summarize miRs that modulate chemoresistance in DDP-resistant in the top five deadliest cancer, both in vitro and in vivo human models.

Is Autophagy Always a Barrier to Cisplatin Therapy?

Cisplatin has long been a first-line chemotherapeutic agent in the treatment of cancer, largely for solid tumors. During the course of the past two decades, autophagy has been identified in response to cancer treatments and almost uniformly detected in studies involving cisplatin. There has been increasing recognition of autophagy as a critical factor affecting tumor cell death and tumor chemoresistance. In this review and commentary, we introduce four mechanisms of resistance to cisplatin followed by a discussion of the factors that affect the role of autophagy in cisplatin-sensitive and resistant cells and explore the two-sided outcomes that occur when autophagy inhibitors are combined with cisplatin. Our goal is to analyze the potential for the combinatorial use of cisplatin and autophagy inhibitors in the clinic.

Long non-coding RNA PAARH promotes hepatocellular carcinoma progression and angiogenesis via upregulating HOTTIP and activating HIF-1α/VEGF signaling

Hepatocellular carcinoma (HCC) is one of the leading lethal malignancies and a hypervascular tumor. Although some long non-coding RNAs (lncRNAs) have been revealed to be involved in HCC. The contributions of lncRNAs to HCC progression and angiogenesis are still largely unknown. In this study, we identified a HCC-related lncRNA, CMB9-22P13.1, which was highly expressed and correlated with advanced stage, vascular invasion, and poor survival in HCC. We named this lncRNA Progression and Angiogenesis Associated RNA in HCC (PAARH). Gain- and loss-of function assays revealed that PAARH facilitated HCC cellular growth, migration, and invasion, repressed HCC cellular apoptosis, and promoted HCC tumor growth and angiogenesis in vivo. PAARH functioned as a competing endogenous RNA to upregulate HOTTIP via sponging miR-6760-5p, miR-6512-3p, miR-1298-5p, miR-6720-5p, miR-4516, and miR-6782-5p. The expression of PAARH was significantly positively associated with HOTTIP in HCC tissues. Functional rescue assays verified that HOTTIP was a critical mediator of the roles of PAARH in modulating HCC cellular growth, apoptosis, migration, and invasion. Furthermore, PAARH was found to physically bind hypoxia inducible factor-1 subunit alpha (HIF-1α), facilitate the recruitment of HIF-1α to VEGF promoter, and activate VEGF expression under hypoxia, which was responsible for the roles of PAARH in promoting angiogenesis. The expression of PAARH was positively associated with VEGF expression and microvessel density in HCC tissues. In conclusion, these findings demonstrated that PAARH promoted HCC progression and angiogenesis via upregulating HOTTIP and activating HIF-1α/VEGF signaling. PAARH represents a potential prognostic biomarker and therapeutic target for HCC.

Gastric cancer: An epigenetic view

Gastric cancer (GC) poses a serious threat worldwide with unfavorable prognosis mainly due to late diagnosis and limited therapies. Therefore, precise molecular classification and search for potential targets are required for diagnosis and treatment, as GC is complicated and heterogeneous in nature. Accumulating evidence indicates that epigenetics plays a vital role in gastric carcinogenesis and progression, including histone modifications, DNA methylation and non-coding RNAs. Epigenetic biomarkers and drugs are currently under intensive evaluations to ensure efficient clinical utility in GC. In this review, key epigenetic alterations and related functions and mechanisms are summarized in GC. We focus on integration of existing epigenetic findings in GC for the bench-to-bedside translation of some pivotal epigenetic alterations into clinical practice and also describe the vacant field waiting for investigation.

The Implication of Autophagy in Gastric Cancer Progression

Gastric cancer is the fifth most common malignancy and the third leading cause of cancer-related death worldwide. The three entirely variable entities have distinct epidemiology, molecular characteristics, prognosis, and strategies for clinical management. However, many gastric tumors appear to be resistant to current chemotherapeutic agents. Moreover, a significant number of gastric cancer patients, with a lack of optimal treatment strategies, have reduced survival. In recent years, multiple research data have highlighted the importance of autophagy, an essential catabolic process of cytoplasmic component digestion, in cancer. The role of autophagy as a tumor suppressor or tumor promoter mechanism remains controversial. The multistep nature of the autophagy process offers a wide array of targetable points for designing novel chemotherapeutic strategies. The purpose of this review is to summarize the current knowledge regarding the interplay between gastric cancer development and the autophagy process and decipher the role of autophagy in this kind of cancer. A plethora of different agents that direct or indirect target autophagy may be a novel therapeutic approach for gastric cancer patients.

Prognostic Autophagy-Related Genes of Gastric Cancer Patients on Chemotherapy

Background: Chemotherapy resistance based on fluorouracil and cisplatin is one of the most encountered postoperative clinical problems in patients diagnosed with gastric cancer (GC), resulting in poor prognosis. Aim of the Study: This study aimed to combine autophagy-related genes (ARGs) to investigate the susceptibility patients with GC to postoperative chemotherapy. Methods: Based on The Cancer Genome Atlas (TCGA) database, gene expression data for GC patients undergoing chemotherapy were integrated and analyzed. Prognostic genes were screened based on univariate and multivariate analysis regression analysis. Subjects were divided into high-risk and low-risk groups according to the median risk score. Kaplan-Meier method was used to evaluate OS and DFS. The accuracy of the prediction was determined by the subject operating characteristic curve analysis. In addition, stratified analyses based on different clinical variables was performed to assess the correlation between risk scores and clinical variables. Quantitative real-time (qRT) PCR was used to verify the expression of CXCR4 in GC tissues and cell lines. Results: A total of nine ARGs related to the prognosis of chemotherapy patients were screened out. Compared with normal gastric mucosa cell, CXCR4 showed elevated expression in GC and was significantly associated with survival. Based on GEO and TCGA databases, the model accurately predicted DFS and OS after chemotherapy. Conclusion: This study established prognostic markers based on nine genes, predicting that ARGs are related to chemotherapy susceptibility of GC patients, which can provide better individualized treatment regimens for clinical practice.

Functional interplay between long non-coding RNAs and the Wnt signaling cascade in osteosarcoma

Osteosarcoma is a common and highly malignant bone tumor among children, adolescents and young adults. However, the underlying molecular mechanisms remain largely unexplored. LncRNAs are transcripts with no or limited protein-coding capacity in human genomes, and have been demonstrated to play crucial functions in initiation, progression, therapeutic resistance, recurrence and metastasis of tumor. Considerable studies revealed a dysregulated lncRNA expression pattern in osteosarcoma, which may act as oncogenes or suppressors to regulate osteosarcoma progression. Wnt signaling pathway is an important cascade in tumorigenesis by modulation of pleiotropic biological functions including cell proliferation, apoptosis, differentiation, stemness, genetic stability and chemoresistance. Hyperactivation or deficiency of key effectors in Wnt cascade is a common event in many osteosarcoma patients. Recently, increasing evidences have suggested that lncRNAs could interplay with component of Wnt pathway, and thereby contribute to osteosarcoma onset, progression and dissemination. In this review, we briefly summarize Wnt signaling-related lncRNAs in osteosarcoma progression, aiming to gain insights into their underlying crosstalk as well as clinical application in osteosarcoma therapeutic modalities.

The Role of Autophagy in Gastric Cancer Chemoresistance: Friend or Foe?

Gastric cancer is the third most common cause of cancer-related death worldwide. Drug resistance is the main inevitable and vital factor leading to a low 5-year survival rate for patients with gastric cancer. Autophagy, as a highly conserved homeostatic pathway, is mainly regulated by different proteins and non-coding RNAs (ncRNAs) and plays dual roles in drug resistance of gastric cancer. Thus, targeting key regulatory nodes in the process of autophagy by small molecule inhibitors or activators has become one of the most promising strategies for the treatment of gastric cancer in recent years. In this review, we provide a systematic summary focusing on the relationship between autophagy and chemotherapy resistance in gastric cancer. We comprehensively discuss the roles and molecular mechanisms of multiple proteins and the emerging ncRNAs including miRNAs and lncRNAs in the regulation of autophagy pathways and gastric cancer chemoresistance. We also summarize the regulatory effects of autophagy inhibitor and activators on gastric cancer chemoresistance. Understanding the vital roles of autophagy in gastric cancer chemoresistance will provide novel opportunities to develop promising therapeutic strategies for gastric cancer.

MicroRNA-mediated autophagy regulation in cancer therapy: The role in chemoresistance/chemosensitivity

Chemoresistance has doubled the effort needed to reach an effective treatment for cancer. Now, scientists should consider molecular pathways and mechanisms involved in chemoresistance to overcome cancer. Autophagy is a "self-digestion" mechanism in which potentially toxic and aged organelles and macromolecules are degraded. Increasing evidence has shown that autophagy possesses dual role in cancer cells (onco-suppressor or oncogene). So, it is vital to identify its role in cancer progression and malignancy. MicroRNAs (miRs) are epigenetic factors capable of modulation of autophagy in cancer cells. In the current review, we emphasize on the relationship between miRs and autophagy in cancer chemotherapy. Besides, we discuss upstream mediators of miR/autophagy axis in cancer chemotherapy including long non-coding RNAs, circular RNAs, Nrf2 c-Myc, and HIF-1α. At the final section, we provide a discussion about how anti-tumor compounds affect miR/autophagy axis in ensuring chemosensitivity. These topics are described in this review to show how autophagy inhibition/induction can lead to chemosensitivity/chemoresistance, and miRs are considered as key players in these discussions.