GPR56 Drives Colorectal Tumor Growth and Promotes Drug Resistance through Upregulation of MDR1 Expression via a RhoA-Mediated Mechanism

Cancer Stem Cell markers: Symphonic masters of chemoresistance and immune evasion

Cancer Stem Cells (CSCs) are highly tumorigenic, chemoresistant, and immune evasive. They emerge as a central driver that gives rise to the bulk of tumoral mass, modifies the tumor microenvironment (TME), and exploits it, leading to poor clinical outcomes for patients with cancer. The existence of CSCs thus accounts for the failure of conventional therapies and immune surveillance. Identifying CSCs in solid tumors remains a significant challenge in modern oncology, with the use of cell surface markers being the primary strategy for studying, isolating, and enriching these cells. In this review, we explore CSC markers, focusing on the underlying signaling pathways that drive CSC self-renewal, which simultaneously makes them intrinsically chemoresistant and immune system evaders. We comprehensively discuss the autonomous and non-autonomous functions of CSCs, with particular emphasis on their interactions with the tumor microenvironment, especially immune cells. This reciprocal network enhances CSCs malignancy while compromising the surrounding niche, ultimately defining therapeutic vulnerabilities associated with each CSC marker. The most common CSCs surface markers addressed in this review-CD44, CD133, ICAM1/CD54, and LGR5-provide insights into the interplay between chemoresistance and immune evasion, two critically important phenomena in disease eradication. This new perspective on the state-of-the-art of CSCs will undoubtedly open new avenues for therapy.

RhoA-ROCK2 signaling possesses complex pathophysiological functions in cancer progression and shows promising therapeutic potential

The Rho GTPase signaling pathway is responsible for cell-specific processes, including actin cytoskeleton organization, cell motility, cell division, and the transcription of specific genes. The implications of RhoA and the downstream effector ROCK2 in cancer epithelial-mesenchymal transition, migration, invasion, and therapy resistance associated with stem cells highlight the potential of targeting RhoA/ROCK2 signaling in therapy. Tumor relapse can occur due to cancer cells that do not fully respond to adjuvant chemoradiotherapy, targeted therapy, or immunotherapy. Rho signaling-mediated mitotic defects and cytokinesis failure lead to asymmetric cell division, allowing cells to form polyploids to escape cytotoxicity and promote tumor recurrence and metastasis. In this review, we elucidate the significance of RhoA/ROCK2 in the mechanisms of cancer progression and summarize their inhibitors that may improve treatment strategies.

Mechanisms of peptide agonist dissociation and deactivation of adhesion G-protein-coupled receptors

Adhesion G protein-coupled receptors (ADGRs) belong to Class B2 of GPCRs and are involved in a wide array of important physiological processes. ADGRs contain a GPCR autoproteolysis-inducing (GAIN) domain that is proximal to the receptor N-terminus and undergoes autoproteolysis during biosynthesis to generate two fragments: the N-terminal fragment (NTF) and C-terminal fragment (CTF). Dissociation of NTF reveals a tethered agonist to activate CTF of ADGRs for G protein signaling. Synthetic peptides that mimic the tethered agonist can also activate the ADGRs. However, mechanisms of peptide agonist dissociation and deactivation of ADGRs remain poorly understood. In this study, we have performed all-atom enhanced sampling simulations using a novel Protein-Protein Interaction-Gaussian accelerated Molecular Dynamics (PPI-GaMD) method on the ADGRG2-IP15 and ADGRG1-P7 complexes. The PPI-GaMD simulations captured dissociation of the IP15 and P7 peptide agonists from their target receptors. We were able to identify important low-energy conformations of ADGRG2 and ADGRG1 in the active, intermediate, and inactive states, as well as exploring different states of the peptide agonists IP15 and P7 during dissociation. Therefore, our PPI-GaMD simulations have revealed dynamic mechanisms of peptide agonist dissociation and deactivation of ADGRG1 and ADGRG2, which will facilitate rational design of peptide regulators of the two receptors and other ADGRs.

The intestinal stem cell as a target: A review

Human intestinal epithelium handles several events that may affect health. It is composed of villi and crypts, which contain different types of cells. Each cell type plays an essential role in intestinal functions, including absorption, defense, self-renewal, and regeneration. Intestinal stem cells (ISCs), located at the base of intestinal crypts, play an important role in intestinal homeostasis and renewal. Any disruption in intestinal homeostasis, in which ISCs alter their function, may result in tumor growth. As Wnt and Notch signaling pathways are essential for ISCs homeostasis and for maintaining self-renewal, any defects in these pathways could increase the risk of developing colorectal cancer (CRC). Lgr5+ cells have been identified as intestinal stem cells expressing a leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5), which is involved in the regulation of Wnt signaling. Several studies have reported upregulated expression of LGR5 in CRC. Hence, in this review, we discuss the relationship between LGR5, Wnt signaling, and Notch signaling and the development of CRC, as well as recent therapeutic strategies targeting LGR5, cancer stem cells (CSCs), and the aforementioned signaling pathways.

Depletion of CPNE7 sensitizes colorectal cancer to 5-fluorouracil by downregulating ATG9B expression

We aimed to explore the biological function of CPNE7 and determine the impact of CPNE7 on chemotherapy resistance in colorectal cancer (CRC) patients. According to the Gene Expression Profiling Interactive Analysis database and previously published data, CPNE7 was identified as a potential oncogene in CRC. RT-qPCR and Western blotting were performed to verify the expression of CPNE7. Chi-square test was used to evaluate the associations between CPNE7 and clinical features. Cell proliferation, colony formation, cell migration and invasion, cell cycle and apoptosis were assessed to determine the effects of CPNE7. Transcriptome sequencing was used to identify potential downstream regulatory genes, and gene set enrichment analysis was performed to investigate downstream pathways. The effect of CPNE7 on 5-fluorouracil chemosensitivity was verified by half maximal inhibitory concentration (IC50). Subcutaneous tumorigenesis assay was used to examine the role of CPNE7 in sensitivity of CRC to chemotherapy in vivo. Transmission electron microscopy was used to detect autophagosomes. CPNE7 was highly expressed in CRC tissues, and its expression was correlated with T stage and tumour site. Knockdown of CPNE7 inhibited the proliferation and colony formation of CRC cells and promoted apoptosis. Knockdown of CPNE7 suppressed the expression of ATG9B and enhanced the sensitivity of CRC cells to 5-fluorouracil in vitro and in vivo. Knockdown of CPNE7 reversed the induction of the autophagy pathway by rapamycin and reduced the number of autophagosomes. Depletion of CPNE7 attenuated the malignant proliferation of CRC cells and enhanced the chemosensitivity of CRC cells to 5-fluorouracil.

Inhibition of RhoGEF/RhoA alleviates regorafenib resistance and cancer stemness via Hippo signaling pathway in hepatocellular carcinoma

Patients with hepatocellular carcinoma (HCC) are vulnerable to drug resistance. Although drug resistance has been taken much attention to HCC therapy, little is known of regorafenib and regorafenib resistance (RR). This study aimed to determine the drug resistance pattern and the role of RhoA in RR. Two regorafenib-resistant cell lines were constructed based on Huh7 and Hep3B cell lines. In vitro and in vivo assays were conducted to study RhoA expression, the activity of Hippo signaling pathway and cancer stem cell (CSC) traits. The data showed that RhoA was highly expressed, Hippo signaling was hypoactivated and CSC traits were more prominent in RR cells. Inhibiting RhoA could reverse RR, and the alliance of RhoA inhibition and regorafenib synergistically attenuated CSC phenotype. Furthermore, inhibiting LARG/RhoA increased Kibra/NF2 complex formation, prevented YAP from shuttling into the nucleus and repressed CD44 mRNA expression. Clinically, the high expression of RhoA correlated with poor prognosis. LARG, RhoA, YAP1 and CD44 show positive correlation with each other. Thus, inhibition of RhoGEF/RhoA has the potential to reverse RR and repress CSC phenotype in HCC.

GPR56, an Adhesion GPCR with Multiple Roles in Human Diseases, Current Status and Future Perspective

Human G protein-coupled receptor 56 (GPR56) belongs to a member of the adhesion G-protein coupled receptor (aGPCR) family and widely exists in the central nervous system and various types of tumor tissues. Recent studies have shown that abnormal expression or dysfunction of GPR56 is closely associated with many physiological and pathological processes, including brain development, neuropsychiatric disorders, cardiovascular diseases and cancer progression. In addition, GPR56 has been proven to enhance the susceptibility of some antipsychotics and anticarcinogens in response to the treatment of neuropsychological diseases and cancer. Although there have been some reports about the functions of GPR56, the underlying mechanisms implicated in these diseases have not been clarified thoroughly, especially in depression and epilepsy. Therefore, in this review, we described the molecular structure and signal transduction pathway of GPR56 and carried out a comprehensive summary of GPR56's function in the development of psychiatric disorders and cancer. Our review showed that GPR56 deficiency led to depressive-like behaviors and an increase in resistance to antipsychotic treatment. In contrast, the upregulation of GPR56 contributed to tumor cell proliferation and metastasis in malignant diseases such as glioblastoma, colorectal cancer, and ovarian cancer. Moreover, we elucidated specific signaling pathways downstream of GPR56 related to the pathogenesis of these diseases. In summary, our review provides compelling arguments for an attractive therapeutic target of GPR56 in improving the therapeutic efficiency for patients suffering from psychiatric disorders and cancer.

The expression profile and tumorigenic mechanisms of CD97 (ADGRE5) in glioblastoma render it a targetable vulnerability

Glioblastoma (GBM) is the most common and aggressive primary brain malignancy. Adhesion G protein-coupled receptors (aGPCRs) have attracted interest for their potential as treatment targets. Here, we show that CD97 (ADGRE5) is the most promising aGPCR target in GBM, by virtue of its de novo expression compared to healthy brain tissue. CD97 knockdown or knockout significantly reduces the tumor initiation capacity of patient-derived GBM cultures (PDGCs) in vitro and in vivo. We find that CD97 promotes glycolytic metabolism via the mitogen-activated protein kinase (MAPK) pathway, which depends on phosphorylation of its C terminus and recruitment of β-arrestin. We also demonstrate that THY1/CD90 is a likely CD97 ligand in GBM. Lastly, we show that an anti-CD97 antibody-drug conjugate selectively kills tumor cells in vitro. Our studies identify CD97 as a regulator of tumor metabolism, elucidate mechanisms of receptor activation and signaling, and provide strong scientific rationale for developing biologics to target it therapeutically in GBM.

Mechanism of multidrug resistance to chemotherapy mediated by P‑glycoprotein (Review)

Multidrug resistance (MDR) seriously limits the clinical application of chemotherapy. A mechanism underlying MDR is the overexpression of efflux transporters associated with chemotherapeutic drugs. P‑glycoprotein (P‑gp) is an ATP‑binding cassette (ABC) transporter, which promotes MDR by pumping out chemotherapeutic drugs and reducing their intracellular concentration. To date, overexpression of P‑gp has been detected in various types of chemoresistant cancer and inhibiting P‑gp‑related MDR has been suggested. The present review summarizes the mechanisms underlying MDR mediated by P‑gp in different tumors and evaluated the related signaling pathways, with the aim of improving understanding of the current status of P‑gp‑mediated chemotherapeutic resistance. This review focuses on the main mechanisms of inhibiting P‑gp‑mediated MDR, with the aim of providing a reference for the study of reversing P‑gp‑mediated MDR. The first mechanism involves decreasing the efflux activity of P‑gp by altering its conformation or hindering P‑gp‑chemotherapeutic drug binding. The second inhibitory mechanism involves inhibiting P‑gp expression to reduce efflux. The third inhibitory mechanism involves knocking out the ABCB1 gene. Potential strategies that can inhibit P‑gp include certain natural products, synthetic compounds and biological techniques. It is important to screen lead compounds or candidate techniques for P‑gp inhibition, and to identify inhibitors by targeting the relevant signaling pathways to overcome P‑gp‑mediated MDR.

GPR114/ADGRG5 is activated by its tethered peptide agonist because it is a cleaved adhesion GPCR

Family B2 or adhesion G protein-coupled receptors (AGPCRs) are distinguished by variable extracellular regions that contain a modular protease, termed the GPCR autoproteolysis-inducing domain that self-cleaves the receptor into an N-terminal fragment (NTF) and a C-terminal fragment (CTF), or seven transmembrane domain (7TM). The NTF and CTF remain bound after cleavage through noncovalent interactions. NTF binding to a ligand(s) presented by nearby cells, or the extracellular matrix anchors the NTF, such that cell movement generates force to induce NTF/CTF dissociation and expose the AGPCR tethered peptide agonist. The released tethered agonist (TA) binds rapidly to the 7TM orthosteric site to activate signaling. The orphan AGPCR, GPR114 was reported to be uncleaved, yet paradoxically capable of activation by its TA. GPR114 has an identical cleavage site and TA to efficiently cleave GPR56. Here, we used immunoblotting and biochemical assays to demonstrate that GPR114 is a cleaved receptor, and the self-cleavage is required for GPR114 TA-activation of Gs and no other classes of G proteins. Mutagenesis studies defined features of the GPR114 and GPR56 GAINA subdomains that influenced self-cleavage efficiency. Thrombin treatment of protease-activated receptor 1 leader/AGPCR fusion proteins demonstrated that acute decryption of the GPR114/56 TAs activated signaling. GPR114 was found to be expressed in an eosinophilic-like cancer cell line (EoL-1 cells) and endogenous GPR114 was efficiently self-cleaved. Application of GPR114 TA peptidomimetics to EoL-1 cells stimulated cAMP production. Our findings may aid future delineation of GPR114 function in eosinophil cAMP signaling related to migration, chemotaxis, or degranulation.

TBX18 knockdown sensitizes esophageal squamous cell carcinoma to radiotherapy by blocking the CHN1/RhoA axis

OBJECTIVE

Radioresistance is a challenge in the effective treatment of esophageal squamous cell carcinoma (ESCC). Herein, this research ascertained whether TBX18 reduced the radiosensitivity of ESCC.

METHODS

Bioinformatics analysis was utilized to retrieve differentially expressed genes. Then, the expression of corresponding candidate genes was tested using qRT-PCR in ESCC clinical specimens, and TBX18 was selected for subsequent experiments. The binding between TBX18 and CHN1 was evaluated by dual-luciferase reporter and ChIP assays, and the relationship between CHN1 and RhoA was identified by GST pull-down. Ectopic expression or knockdown experiments and radiation treatment were performed in cells and the nude mouse xenograft model to clarify the impacts of TBX18, CHN1, and RhoA on radiosensitivity in ESCC.

RESULTS

Bioinformatics analysis and qRT-PCR retrieved upregulated TBX18 in ESCC for the follow-up study. Additionally, TBX18 was positively correlated with CHN1 in ESCC clinical specimens. Mechanistically, TBX18 bound to the CHN1 promoter region to transcriptionally activate CHN1, thus elevating RhoA activity. Moreover, TBX18 knockdown reduced ESCC cell proliferation and migration while augmenting their apoptosis after radiation, which was negated by further overexpressing CHN1 or RhoA. CHN1 or RhoA knockdown diminished ESCC cell proliferation and migration, as well as enhanced cell apoptosis, subsequent to radiation. Likewise, TBX18 overexpression increased ESCC cell autophagy after radiation, which was partially reversed by knockdown of RhoA. The results of in vivo xenograft experiments in nude mice were concurrent with the in vitro results.

CONCLUSION

TBX18 knockdown lowered CHN1 transcription and thus reduced RhoA activity, which sensitized ESCC cells to radiotherapy.

G protein-coupled receptor-targeting antibody-drug conjugates: Current status and future directions

In recent years, antibody-drug conjugates (ADCs) have emerged as promising anti-cancer therapeutic agents with several having already received market approval for the treatment of solid tumor and hematological malignancies. As ADC technology continues to improve and the range of indications treatable by ADCs increases, the repertoire of target antigens has expanded and will undoubtedly continue to grow. G protein-coupled receptors (GPCRs) are well-characterized therapeutic targets implicated in many human pathologies, including cancer, and represent a promising emerging target of ADCs. In this review, we will discuss the past and present therapeutic targeting of GPCRs and describe ADCs as therapeutic modalities. Moreover, we will summarize the status of existing preclinical and clinical GPCR-targeted ADCs and address the potential of GPCRs as novel targets for future ADC development.

Signaling pathways in cancer metabolism: mechanisms and therapeutic targets

A wide spectrum of metabolites (mainly, the three major nutrients and their derivatives) can be sensed by specific sensors, then trigger a series of signal transduction pathways and affect the expression levels of genes in epigenetics, which is called metabolite sensing. Life body regulates metabolism, immunity, and inflammation by metabolite sensing, coordinating the pathophysiology of the host to achieve balance with the external environment. Metabolic reprogramming in cancers cause different phenotypic characteristics of cancer cell from normal cell, including cell proliferation, migration, invasion, angiogenesis, etc. Metabolic disorders in cancer cells further create a microenvironment including many kinds of oncometabolites that are conducive to the growth of cancer, thus forming a vicious circle. At the same time, exogenous metabolites can also affect the biological behavior of tumors. Here, we discuss the metabolite sensing mechanisms of the three major nutrients and their derivatives, as well as their abnormalities in the development of various cancers, and discuss the potential therapeutic targets based on metabolite-sensing signaling pathways to prevent the progression of cancer.

Loss of LGR5 through Therapy-induced Downregulation or Gene Ablation Is Associated with Resistance and Enhanced MET-STAT3 Signaling in Colorectal Cancer Cells

Leucine-rich repeat-containing, G protein-coupled receptor 5 (LGR5) is highly expressed in colorectal cancer and cancer stem cells (CSCs) that play important roles in tumor initiation, progression, and metastasis. Loss of LGR5 has been shown to enhance therapy resistance. However, the molecular mechanisms that mediate this resistance remain elusive. In this study, we demonstrate conversion of LGR5+ colorectal cancer cells to an LGR5- state in response to chemotherapy, LGR5- targeted antibody-drug conjugates (ADCs), or LGR5 gene ablation led to activation of STAT3. Further investigation revealed increased STAT3 activation occurred as a result of increased mesenchymal epithelial transition (MET) factor receptor activity. LGR5 overexpression decreased MET-STAT3 activity and sensitized colorectal cancer cells to therapy. STAT3 inhibition suppressed MET phosphorylation, while constitutively active STAT3 reduced LGR5 levels and increased MET activity, suggesting a potential feedback mechanism. Combination treatment of MET-STAT3 inhibitors with irinotecan or antibody-drug conjugates (ADCs) substantiated synergistic effects in colorectal cancer cells and tumor organoids. In colorectal cancer xenografts, STAT3 inhibition combined with irinotecan enhanced tumor growth suppression and prolonged survival. These findings suggest a mechanism by which drug-resistant LGR5- colorectal cancer cells acquire a survival advantage through activation of MET-STAT3 and provide rationale for new treatment strategies to target colorectal cancer.

An antibody-drug conjugate targeting GPR56 demonstrates efficacy in preclinical models of colorectal cancer

BACKGROUND

Long-term prognosis remains poor for colorectal cancer (CRC) patients with advanced disease due to treatment resistance. The identification of novel targets is essential for the development of new therapeutic approaches. GPR56, an adhesion GPCR, is highly expressed in CRC tumours and correlates with poor survival. Here, we describe the generation and preclinical evaluation of a novel ADC consisting of an anti-GPR56 antibody (10C7) conjugated with the DNA-damaging payload duocarmycin.

METHODS

RNA-seq dataset analysis was performed to determine GPR56 expression in CRC subtypes. The specificity of binding, epitope mapping, and internalisation of 10C7 was examined. 10C7 was conjugated to payload and ADC cytotoxicity was assessed against a panel of CRC cell lines and tumour organoids. Antitumour efficacy was evaluated in xenograft models of CRC cell lines and patient-derived tumours.

RESULTS

High GPR56 was shown to be associated with the microsatellite stable (MSS) subtype that accounts for 80-85% of CRC. GPR56 ADC selectively induced cytotoxicity in CRC cells and tumour organoids at low nanomolar potency in a GPR56-dependent manner and showed significant antitumour efficacy against GPR56-expressing xenograft models.

CONCLUSIONS

This study provides the rationale for the future development of a GPR56-targeted ADC approach to potentially treat a large fraction of MSS CRC patients.

Functions of G protein-coupled receptor 56 in health and disease

Human G protein-coupled receptor 56 (GPR56) is encoded by gene ADGRG1 from chromosome 16q21 and is homologously encoded in mice, at chromosome 8. Both 687 and 693 splice forms are present in humans and mice. GPR56 has a 381 amino acid-long N-terminal extracellular segment and a GPCR proteolysis site upstream from the first transmembrane domain. GPR56 is mainly expressed in the heart, brain, thyroid, platelets, and peripheral blood mononuclear cells. Accumulating evidence indicates that GPR56 promotes the formation of myelin sheaths and the development of oligodendrocytes in the cerebral cortex of the central nervous system. Moreover, GPR56 contributes to the development and differentiation of hematopoietic stem cells, induces adipogenesis, and regulates the function of immune cells. The lack of GPR56 leads to nervous system dysfunction, platelet disorders, and infertility. Abnormal expression of GPR56 is related to the malignant transformation and tumor metastasis of several cancers including melanoma, neuroglioma, and gastrointestinal cancer. Metabolic disorders and cardiovascular diseases are also associated with dysregulation of GPR56 expression, and GPR56 is involved in the pharmacological resistance to some antidepressant and cancer drug treatments. In this review, the molecular structure, expression profile, and signal transduction of GPR56 are introduced, and physiological and pathological functions of GRP56 are comprehensively summarized. Attributing to its significant biological functions and its long N-terminal extracellular region that interacts with multiple ligands, GPR56 is becoming an attractive therapeutic target in treating neurological and hematopoietic diseases.

Cellular irinotecan resistance in colorectal cancer and overcoming irinotecan refractoriness through various combination trials including DNA methyltransferase inhibitors: a review

Treatment with pharmacological drugs for colorectal cancer (CRC) remains unsatisfactory. A major cause of failure in pharmacotherapy is the resistance of colon cancer cells to the drugs, creating an urgent issue. In this review, we summarize previous studies on the resistance of CRC cells to irinotecan and discuss possible reasons for refractoriness. Our review presents the following five major causes of irinotecan resistance in human CRC: (1) cellular irinotecan resistance is induced mainly through the increased expression of the drug efflux transporter, ABCG2; (2) cellular irinotecan resistance is also induced in association with a nuclear receptor, pregnane/steroid X receptor (PXR/SXR), which is enriched in the CYP3A4 gene enhancer region in CRC cells by exposing the cells to SN-38; (3) irinotecan-resistant cells possess either reduced DNA topoisomerase I (Top1) expression at both the mRNA and protein levels or Top1 missense mutations; (4) alterations in the tumor microenvironment lead to drug resistance through intercellular vesicle-mediated transmission of miRNAs; and (5) CRC stem cells are the most difficult targets to successfully treat CRC. In the clinical setting, CRC gradually develops resistance to initially effective irinotecan-based therapy. To solve this problem, several clinical trials, such as irinotecan plus cetuximab vs. cetuximab monotherapy, have been conducted. Another clinical trial on irinotecan plus guadecitabine, a DNA-methyltransferase inhibitor, has also been conducted.

Role of ADGRG1/GPR56 in Tumor Progression

Cellular communication plays a critical role in diverse aspects of tumorigenesis including tumor cell growth/death, adhesion/detachment, migration/invasion, angiogenesis, and metastasis. G protein-coupled receptors (GPCRs) which constitute the largest group of cell surface receptors are known to play fundamental roles in all these processes. When considering the importance of GPCRs in tumorigenesis, the adhesion GPCRs (aGPCRs) are unique due to their hybrid structural organization of a long extracellular cell-adhesive domain and a seven-transmembrane signaling domain. Indeed, aGPCRs have been increasingly shown to be associated with tumor development by participating in tumor cell interaction and signaling. ADGRG1/GPR56, a representative tumor-associated aGPCR, is recognized as a potential biomarker/prognostic factor of specific cancer types with both tumor-suppressive and tumor-promoting functions. We summarize herein the latest findings of the role of ADGRG1/GPR56 in tumor progression.

Roles of G Protein-Coupled Receptors (GPCRs) in Gastrointestinal Cancers: Focus on Sphingosine 1-Shosphate Receptors, Angiotensin II Receptors, and Estrogen-Related GPCRs

It is well established that gastrointestinal (GI) cancers are common and devastating diseases around the world. Despite the significant progress that has been made in the treatment of GI cancers, the mortality rates remain high, indicating a real need to explore the complex pathogenesis and develop more effective therapeutics for GI cancers. G protein-coupled receptors (GPCRs) are critical signaling molecules involved in various biological processes including cell growth, proliferation, and death, as well as immune responses and inflammation regulation. Substantial evidence has demonstrated crucial roles of GPCRs in the development of GI cancers, which provided an impetus for further research regarding the pathophysiological mechanisms and drug discovery of GI cancers. In this review, we mainly discuss the roles of sphingosine 1-phosphate receptors (S1PRs), angiotensin II receptors, estrogen-related GPCRs, and some other important GPCRs in the development of colorectal, gastric, and esophageal cancer, and explore the potential of GPCRs as therapeutic targets.

Recent Updates on Mechanisms of Resistance to 5-Fluorouracil and Reversal Strategies in Colon Cancer Treatment

5-Fluorouracil (5-FU) plus leucovorin (LV) remain as the mainstay standard adjuvant chemotherapy treatment for early stage colon cancer, and the preferred first-line option for metastatic colon cancer patients in combination with oxaliplatin in FOLFOX, or irinotecan in FOLFIRI regimens. Despite treatment success to a certain extent, the incidence of chemotherapy failure attributed to chemotherapy resistance is still reported in many patients. This resistance, which can be defined by tumor tolerance against chemotherapy, either intrinsic or acquired, is primarily driven by the dysregulation of various components in distinct pathways. In recent years, it has been established that the incidence of 5-FU resistance, akin to multidrug resistance, can be attributed to the alterations in drug transport, evasion of apoptosis, changes in the cell cycle and DNA-damage repair machinery, regulation of autophagy, epithelial-to-mesenchymal transition, cancer stem cell involvement, tumor microenvironment interactions, miRNA dysregulations, epigenetic alterations, as well as redox imbalances. Certain resistance mechanisms that are 5-FU-specific have also been ascertained to include the upregulation of thymidylate synthase, dihydropyrimidine dehydrogenase, methylenetetrahydrofolate reductase, and the downregulation of thymidine phosphorylase. Indeed, the successful modulation of these mechanisms have been the game plan of numerous studies that had employed small molecule inhibitors, plant-based small molecules, and non-coding RNA regulators to effectively reverse 5-FU resistance in colon cancer cells. It is hoped that these studies would provide fundamental knowledge to further our understanding prior developing novel drugs in the near future that would synergistically work with 5-FU to potentiate its antitumor effects and improve the patient's overall survival.

ADGRG1 Is a Predictor of Chemoresistance and Poor Survival in Cervical Squamous Carcinoma

Background

Cisplatin is the first-line chemotherapy for cervical cancer. Cisplatin resistance has always been one of the most significant barriers to acquiring better outcomes. However, the complex molecular mechanisms accounting for the phenomenon are not completely clear.

Methods

Construction of the cisplatin-resistant cell model of cervical cancer, then performing RNA sequencing and bioinformatic analysis of the differential expression genes. Then Adhesion G protein-coupled receptor G1 (ADGRG1) was screened out as our target gene. Gene Expression Profiling Interactive Analysis (GEPIA) was searched to show the expression level of ADGRG1 in cervical cancer and normal tissue. Kaplan-Meier Plotter (Kmplot) was used to explore the relationship of its expression with survival data. Tissue specimens were used to verify the relationship between the clinicopathological characteristics and ADGRG1 expression. Then we explored the roles of ADGRG1 in tumorigenesis through in vitro and in vivo assays.

Results

We found the ADGRG1 was significantly overexpressed in cervical cancer tissues compared to corresponding normal tissues. Higher ADGRG1 expression was correlated with poor progress-free survival. Knockdown of ADGRG1 markedly suppressed cell proliferation, migration, and invasion and increased cell sensitivity to cisplatin in vitro. Similarly, the role of ADGRG1 knockdown on tumorigenicity and sensitivity to cisplatin treatment was verified in vivo. The underlying mechanism was explored by western blotting that ADGRG1 knockdown inhibited tumorigenesis by PI3K/Akt/mTOR signaling pathway.

Conclusion

ADGRG1 acts as an oncogene to maintain tumorigenicity, migration, and invasion, and its depressed expression prompts sensitivity to cisplatin. Thus, ADGRG1 may represent a potential prognostic marker and possible therapeutic target for cervical cancer.

The role of GPR56/ADGRG1 in health and disease

GPR56/ADGRG1 is a versatile adhesion G protein-coupled receptor important in the physiological functions of the central and peripheral nervous systems, reproductive system, muscle hypertrophy, immune regulation, and hematopoietic stem cell generation. By contrast, aberrant expression or deregulated functions of GPR56 have been implicated in diverse pathological processes, including bilateral frontoparietal polymicrogyria, depression, and tumorigenesis. In this review article, we summarize and discuss the current understandings of the role of GPR56 in health and disease.

Targeting cancer stem cells for reversing therapy resistance: mechanism, signaling, and prospective agents

Cancer stem cells (CSCs) show a self-renewal capacity and differentiation potential that contribute to tumor progression and therapy resistance. However, the underlying processes are still unclear. Elucidation of the key hallmarks and resistance mechanisms of CSCs may help improve patient outcomes and reduce relapse by altering therapeutic regimens. Here, we reviewed the identification of CSCs, the intrinsic and extrinsic mechanisms of therapy resistance in CSCs, the signaling pathways of CSCs that mediate treatment failure, and potential CSC-targeting agents in various tumors from the clinical perspective. Targeting the mechanisms and pathways described here might contribute to further drug discovery and therapy.

Ursolic acid reduces Adriamycin resistance of human ovarian cancer cells through promoting the HuR translocation from cytoplasm to nucleus

Ursolic acid (UA) has been shown to suppress various tumor progression, however, its roles in Adriamycin resistance of human ovarian cancer (OC) cells are still unclear. This work aims to investigate the effects of UA on the Adriamycin resistance of human OC cells. Here, we constructed Adriamycin-resistant OC SKOV3-Adr cells and found that UA attenuated Adriamycin resistance in SKOV3-Adr cells. Additionally, UA enhanced Adriamycin sensitivity in the parental SKOV3 and another OC cell line A2780 cells. Mechanistic studies showed that HuR mRNA level was similar between SKOV3 and SKOV3-Adr cells, but the cytoplasmic expression of HuR protein was increased in SKOV3-Adr cells compared with that in SKOV3 cells, and subsequently enhancing the mRNA stability of multidrug resistance gene 1 (MDR1). Moreover, UA had no effects on HuR expression, but promoted the cytoplasm-nucleus translocation of HuR protein, decreased MDR1 mRNA stability and thus reduced MDR1 expression. Furthermore, overexpression of MDR1 rescued the effects of UA on Adriamycin resistance and sensitivity. This work reveals a novel HuR/MDR1 axis responsible for UA-mediated attenuation on Adriamycin resistance in OC cells.

Streptomycin sulphate loaded solid lipid nanoparticles show enhanced uptake in macrophage, lower MIC in Mycobacterium and improved oral bioavailability

Present study addresses the challenge of incorporating hydrophilic streptomycin sulphate (STRS; log P -6.4) with high dose (1 g/day) into a lipid matrix of SLNs. Cold high-pressure homogenization technique used for SLN preparation achieved 30% drug loading and 51.17 ± 0.95% entrapment efficiency. Polyethylene glycol 600 as a supporting-surfactant assigned small size (218.1 ± 15.46 nm) and mucus-penetrating property. It was conceived to administer STRS-SLNs orally rather than intramuscularly. STRS-SLNs remained stable on incubation for varying times in SGF or SIF. STRS-SLNs were extensively characterised for microscopic (TEM and AFM), thermal (DSC), diffraction (XRD) and spectroscopic (NMR and FTIR) properties and showed zero-order controlled release. Enhanced (60 times) intracellular uptake was observed in THP-1 and Pgp expressing LoVo and DLD-1 cell lines, using fluorescein-SLNs. Presence of SLNs in LoVo cells was also revealed by TEM studies. STRS-SLNs showed 3 times reduction in MIC against Mycobacterium tuberculosis H37RV (256182) in comparison to free STRS. It also showed better activity against both M. bovis BCG and Mycobacterium tuberculosis H37RV (272994) in comparison to free STRS. Cytotoxicity and acute toxicity studies (OECD 425 guidelines) confirmed in vitro and in vivo safety of STRS-SLNs. Single-dose oral pharmacokinetic studies in rat plasma using validated LCMS/MS technique or the microbioassay showed significant oral absorption and bioavailability (160% - 710% increase than free drug).

Anti-GPR56 monoclonal antibody potentiates GPR56-mediated Src-Fak signaling to modulate cell adhesion

GPR56 is a member of the adhesion G-protein-coupled receptor family shown to play important roles in cell adhesion, brain development, immune function, and tumorigenesis. GPR56 is highly upregulated in colorectal cancer and correlates with poor prognosis. Several studies have shown GPR56 couples to the Gα_12/13 class of heterotrimeric G-proteins to promote RhoA activation. However, due to its structural complexity and lack of a high-affinity receptor-specific ligand, the complete GPR56 signaling mechanism remains largely unknown. To delineate the activation mechanism and intracellular signaling functions of GPR56, we generated a monoclonal antibody (mAb) that binds with high affinity and specificity to the extracellular domain (ECD). Using deletion mutants, we mapped the mAb binding site to the GAIN domain, which mediates membrane-proximal autoproteolytic cleavage of the ECD. We showed that GPR56 overexpression in 293T cells leads to increased phosphorylation of Src, Fak, and paxillin adhesion proteins and activation of the Gα_12/13-RhoA-mediated serum response factor (SRF) pathway. Treatment with the mAb potentiated Src-Fak phosphorylation, RhoA–SRF signaling, and cell adhesion. Consistently, GPR56 knockdown in colorectal cancer cells decreased Src–Fak pathway phosphorylation and cell adhesion. Interestingly, GPR56-mediated activation of Src–Fak phosphorylation occurred independent of RhoA, yet mAb-induced potentiation of RhoA–SRF signaling was Src-dependent. Furthermore, we show that the C-terminal portion of the Serine–Threonine–Proline-rich (STP) region, adjacent to the GAIN domain, was required for Src–Fak activation. However, autoproteolytic cleavage of the ECD was dispensable. These data support a new ECD-dependent mechanism by which GPR56 functions to regulate adhesion through activation of Src–Fak signaling.

ANLN Directly Interacts with RhoA to Promote Doxorubicin Resistance in Breast Cancer Cells

Background

Chemotherapy resistance is the leading cause of cancer treatment failure. This research was conducted to explore a potential link between actin-binding protein anillin (ANLN) and doxorubicin resistance in breast cancer.

Materials and Methods

We compared ANLN expression and 50% inhibition concentration (IC50) of doxorubicin in human breast cancer cells (MDA-MB-231) and human breast cancer cells with doxorubicin resistance (MDA-MB-231/ADM). Co-immunoprecipitation was used to investigate the interaction between ANLN and RhoA. The cell viability, apoptosis, gene and protein expression were estimated by MTT, flow cytometry, quantitative real-time PCR and western blot.

Results

The doxorubicin resistance in MDA-MB-231/ADM cells (IC50 = 19.40 ± 1.16 μg/mL) was significantly higher than that in MDA-MB-231 cells (IC50 = 1.65 ± 0.23 μg/mL). ANLN was up-regulated in MDA-MB-231/ADM cells compared to MDA-MB-231 cells. Furthermore, ANLN overexpression promoted cell viability and inhibited apoptosis of MDA-MB-231 cells. The gene and protein expression of multidrug resistance (MDR1) and cancer resistance protein (BCRP) were enhanced by ANLN overexpression in MDA-MB-231 cells. ANLN silencing suppressed cell viability and the expression of MDR1 and BCRP and facilitated apoptosis in MDA-MB-231/ADM cells. Moreover, ANLN promoted RhoA activation by interacting with RhoA. ANLN up-regulation enhanced cell viability and the expression of MDR1 and BCRP and decreased apoptosis of MDA-MB-231 cells. The influence conferred by ANLN overexpression was effectively abolished by C3 transferase.

Conclusion

This work revealed that ANLN promoted doxorubicin resistance in breast cancer cells by activating RhoA. Thus, our study suggests a novel target for breast cancer treatment.

Clinical relevance of multi-drug resistance gene C3435T polymorphism in diffuse large B-cell lymphoma in Xinjiang

To explore the relationship between C3435T polymorphism of multi-drug resistance gene (MDR1) gene and susceptibility, clinicopathological characteristics, curative effect and hematological toxicity of diffuse large B-cell lymphoma (DLBCL) in XinJiang.The peripheral venous blood samples of 54 patients with DLBCL and 60 healthy controls were collected. The alleles and genotypes of MDR1 gene C3435T were detected by DNA direct extraction with PCR technique, and the frequency of C3435T allele and genotypes were detected by the chi-square test. The relationship between the allele and genotype distribution of C3435T locus and the susceptibility, clinicopathological characteristics, curative effect and hematological toxicity of DLBCL were analyzed.1 the frequency of CT heterozygote and CC homozygote mutation was significantly higher in the case group (46.3% in CT genotype and 42.6% in CC genotype) compared to the control group (P < 0.05). The frequency of CC genotype mutation in the case group was 42.6%, which was significantly higher than that in the control group (P < 0.05, OR 3.209, 95% CI: 1.288-7.997). 2 the genotypes of C3435T locus of MDR1 gene were distributed in age, sex, nationality, pathological characteristics, clinical-stage, IPI index, B symptoms, infection with EB virus, clinicopathological characteristics and clinical efficacy of hepatitis B in patients with DLBCL. There was no significant difference in myelosuppression (P > 0.05).The homozygous mutation genotype of CC is the risk genotype of DLBCL. The alleles and genotypes are not associated with the clinicopathological characteristics, efficacy and myelosuppression toxicity of DLBCL.

In Silico Approach in Designing a Novel Multi-Epitope Vaccine Candidate against Non-Small Cell Lung Cancer with Overexpressed G Protein-Coupled Receptor 56

Background:

Majority of cancer-related deaths worldwide is attributed to non-small cell lung cancer (NSCLC). G protein-coupled receptor 56 (GPR56) is overexpressed and associated in the progression of NSCLC. The aim of this study is to use immunoinformatics approach in designing a multi-epitope vaccine to target overexpressed GPR56 which can potentially activate antibody-mediated cell death mechanisms and inhibit pathways involved in the proliferation, migration and survival of NSCLC.

Methods:

Herein, the reported overexpression of GPR56 was further investigated by conducting a differential gene expression analysis of NSCLC samples from GEO DataSets (GSE29249). Results confirmed significant overexpression of GPR56 in NSCLC compared to adjacent normal samples. A multi-epitope vaccine (Fvax) was constructed in silico by adjoining B lymphocytes (BL) and helper T lymphocytes (HTL) epitopes from the extracellular sequence of GPR56. Population coverage (PC) of HTL epitopes was also estimated. To enhance its immunogenicity, sequences of flagellin domains were fused as adjuvant. Fvax was evaluated in silico for antigenicity, allergenicity, peptide toxicity, physicochemical properties and cross-reactivity. Its tertiary structure was predicted, refined, and validated followed by structural epitope prediction. Lastly, Fvax DNA was optimized and cloned in silico.

Results:

This is the first work to design a potential vaccine against GPR56-overexpressing NSCLC. Fvax has 3 BL and 7 HTL immunogenic epitopes on GPR56. In silico evaluations suggest that Fvax is antigenic, non-toxic, non-allergenic, stable, and has accessible BL epitopes with high PC worldwide for HTL epitopes.

Conclusion:

Overall, results showed that Fvax is a potential vaccine against NSCLC. The approach of this study efficiently minimized the number of tests, cost and time required to select the best epitopes and to design a vaccine for the treatment of NSCLC.

The prognostic value of leucine-rich repeat-containing G-protein (Lgr5) and its impact on clinicopathological features of colorectal cancer

Introduction

Colorectal cancer (CRC) constitutes one of the most prevalent malignancies in the world. Recent research suggests that cancer stem cells (CSCs) are responsible for tumor cell’s malignant behavior in CRC. This study has been designed to determinate clinical implications of CSC markers: CD44, DCLK1, Lgr5, and ANXA2 in CRC.

Materials and methods

The study was performed on tissue samples which were collected from 89 patients undergoing colectomy. Formalin-fixed paraffin-embedded tissue blocks with representative tumor areas were identified and corded. Immunohistochemical staining was performed using anti-CD44, anti-LGR5, anti-ANXA2, and anti-DCLK1 antibodies. The H-score system was utilized to determine the immunointensity of CRC cells.

Results

The lower expression of Lgr5 was significantly correlated with the presence of lymph-node metastases (p = 0.011), while high expression of Lgr5 was statistically significant in vascular invasion in examined cancer tissue samples (p = 0.027). Moreover, a high H-score value of Lgr5 expression was significantly related to a reduced overall survival rate (p = 0.043).

Conclusion

Our results suggest a strong relationship between CSC marker Lgr5 and vascular invasion, presence of lymph-node metastasis, and overall poor survival. The presence of Lgr5 might be an unfavorable prognostic factor, and its high level in cancer tissue is related to an aggressive course. This marker could also be used to access the effectiveness of the treatment.

The Neuropeptide System and Colorectal Cancer Liver Metastases: Mechanisms and Management

Colorectal cancer (CRC), classified as the third most prevalent cancer worldwide, remains to be a clinical and research challenge. It is estimated that ~50% of CRC patients die from distant metastases, with treatment of this complication still posing significant difficulties. While liver metastasis (LM) cascade is known in the literature, its mechanisms are still unclear and remain studied in different research models. A connection is suggested between nervous system dysfunctions and a range of Neurotransmitters (Nts) (including Neuropeptides, NPs), Neurotrophins (Ntt) and their receptors (Rs) in CRC liver metastasis development. Studies on the role of NP/NP-Rs in the progression and metastasis of CRC, show the complexity of brain–tumor interactions, caused by their different forms of release to the extracellular environment (endocrine, autocrine, paracrine and neurocrine). Many stages of LM are connected to the activity of pro-inflammatory, e.g., Corticotropin-releasing Hormone Receptor 1 (CRHR1), Neuropeptide Y (NPY) and Neurotensin (NT), anti-inflammatory, e.g., Calcitonin Gene-related Peptide (CGRP), CRHR2 and Vasoactive Intestinal Polypeptide (VIP) or dual role neuropeptides, e.g., Substance P (SP). The regulation of the local immunological profile (e.g., CRH/CRHRs), dysfunctions of enteroprotective role of NPs on epithelial cells (e.g., NT/NT-R), as well as structural-functional changes in enteric nervous system innervation of the tumor are also important. More research is needed to understand the exact mechanisms of communication between the neurons and tumor cells. The knowledge on the mechanisms regulating tumor growth and different stages of metastasis, as well as effects of the action of a numerous group of Nts/NPs/Ntt as growth factors, have implications for future therapeutic strategies. To obtain the best treatment outcomes, it is important to use signaling pathways common for many NPs, as well to develop a range of broad-spectrum antagonists. This review aims to summarize the current knowledge on the importance of neuroactive molecules in the promotion of the invasion-metastasis cascade in CRC, as well as the improvements of clinical management of CRC liver metastasis.

The Neuropeptide System and Colorectal Cancer Liver Metastases: Mechanisms and Management

Colorectal cancer (CRC), classified as the third most prevalent cancer worldwide, remains to be a clinical and research challenge. It is estimated that ~50% of CRC patients die from distant metastases, with treatment of this complication still posing significant difficulties. While liver metastasis (LM) cascade is known in the literature, its mechanisms are still unclear and remain studied in different research models. A connection is suggested between nervous system dysfunctions and a range of Neurotransmitters (Nts) (including Neuropeptides, NPs), Neurotrophins (Ntt) and their receptors (Rs) in CRC liver metastasis development. Studies on the role of NP/NP-Rs in the progression and metastasis of CRC, show the complexity of brain–tumor interactions, caused by their different forms of release to the extracellular environment (endocrine, autocrine, paracrine and neurocrine). Many stages of LM are connected to the activity of pro-inflammatory, e.g., Corticotropin-releasing Hormone Receptor 1 (CRHR1), Neuropeptide Y (NPY) and Neurotensin (NT), anti-inflammatory, e.g., Calcitonin Gene-related Peptide (CGRP), CRHR2 and Vasoactive Intestinal Polypeptide (VIP) or dual role neuropeptides, e.g., Substance P (SP). The regulation of the local immunological profile (e.g., CRH/CRHRs), dysfunctions of enteroprotective role of NPs on epithelial cells (e.g., NT/NT-R), as well as structural-functional changes in enteric nervous system innervation of the tumor are also important. More research is needed to understand the exact mechanisms of communication between the neurons and tumor cells. The knowledge on the mechanisms regulating tumor growth and different stages of metastasis, as well as effects of the action of a numerous group of Nts/NPs/Ntt as growth factors, have implications for future therapeutic strategies. To obtain the best treatment outcomes, it is important to use signaling pathways common for many NPs, as well to develop a range of broad-spectrum antagonists. This review aims to summarize the current knowledge on the importance of neuroactive molecules in the promotion of the invasion-metastasis cascade in CRC, as well as the improvements of clinical management of CRC liver metastasis.

Regulation of Integrin Subunit Alpha 2 by miR-135b-5p Modulates Chemoresistance in Gastric Cancer

Chemotherapy has substantially improved gastric cancer (GC) patient outcomes in the past decades. However, the development of chemotherapy resistance has become the major cause of treatment failure. Although numerous molecules have been implicated in GC chemoresistance, its pathological mechanisms are still unclear. Here, we found that integrin subunit alpha 2 (ITGA2) is upregulated in chemoresistant GC cells and that increased ITGA2 levels correlated with the poor prognosis of GC patients who received chemotherapy. ITGA2 overexpression led to elevated chemotherapy resistance and drug-induced apoptosis inhibition in GC cells. ITGA2 knockdown resulted in restored chemosensitivity and increased apoptosis in chemoresistant GC cells both in vitro and in vivo. NanoString analysis revealed a unique signature of deregulated pathway expression in GC cells after ITGA2 silencing. The MAPK/ERK pathway and epithelial-mesenchymal transition (EMT) were found to be downregulated after ITGA2 knockdown. miR-135b-5p was identified as a direct upstream regulator of ITGA2. miR-135b-5p overexpression reduced chemoresistance and induced apoptosis in GC cells and attenuated ITGA2-induced chemoresistance and antiapoptotic effects by inhibiting MAPK signaling and EMT. In conclusion, this study underscored the role and mechanism of ITGA2 in GC and suggested the novel miR-135b-5p/ITGA2 axis as an epigenetic cause of chemoresistance with diagnostic and therapeutic implications.

m6A modification-mediated CBX8 induction regulates stemness and chemosensitivity of colon cancer via upregulation of LGR5

BACKGROUND

Colon cancer (CC) cells can exhibit stemness and expansion capabilities, which contribute to resistance to conventional chemotherapies. Aberrant expression of CBX8 has been identified in many types of cancer, but the cause of this aberrant CBX8 expression and whether CBX8 is associated with stemness properties in CC remain unknown.

METHODS

qRT-PCR and IHC were applied to examine CBX8 levels in normal and chemoresistant CC tissues. Cancer cell stemness and chemosensitivity were evaluated by spheroid formation, colony formation, Western blot and flow cytometry assays. RNA-seq combined with ChIP-seq was used to identify target genes, and ChIP, IP and dual luciferase reporter assays were applied to explore the underlying mechanisms.

RESULTS

CBX8 was significantly overexpressed in chemoresistant CC tissues. In addition, CBX8 could promote stemness and suppress chemosensitivity through LGR5. Mechanistic studies revealed that CBX8 activate the transcription of LGR5 in a noncanonical manner with assistance of Pol II. CBX8 recruited KMT2b to the LGR5 promoter, which maintained H3K4me3 status to promote LGR5 expression. Moreover, m6A methylation participated in the upregulation of CBX8 by maintaining CBX8 mRNA stability.

CONCLUSIONS

Upon m6A methylation-induced upregulation, CBX8 interacts with KMT2b and Pol II to promote LGR5 expression in a noncanonical manner, which contributes to increased cancer stemness and decreased chemosensitivity in CC. This study provides potential new therapeutic targets and valuable prognostic markers for CC.