Drug Resistance In Colorectal Cancer Research Articles

High expression of ADAR mediated by OGT promotes chemoresistance in colorectal cancer through the A-to-I editing pathway.

Colorectal cancer (CRC) is a malignant tumor with poor prognosis and adverse therapeutic effect. The study aims to elucidate the contribution of OGT-mediated glycosylation of ADAR to chemoresistance in CRC through its role and regulatory mechanisms. Variations in OGT expression levels and their impact on CRC cell chemoresistance were investigated using gain-of-function and loss-of-function assays. Through a series of molecular biology experiments, we confirmed that ADAR is the downstream target of OGT regulation, emphasizing the role of OGT-mediated glycosylation in stabilizing ADAR. Furthermore, RNA immunoprecipitation (RIP) assays were conducted to examine the effects of ADAR-mediated A-to-I editing on the mRNA stability and translation of genes associated with DNA damage repair. Elevated OGT expression was found to enhance CRC's malignancy and resistance to chemotherapy. OGT's influence leads to the glycosylation of ADAR, thereby increasing its protein levels. ADAR, through its role in A-to-I editing, modulates the mRNA editing of genes implicated in DNA damage repair. This regulation enhances the expression of these genes, improves DNA repair capabilities, and ultimately, fosters chemoresistance in CRC cells. In conclusion, ADAR promotes PARP1 expression under the positive regulation of OGT-mediated O-glycosylation modification to enhance drug resistance in COAD cells. It provides the research basis for overcoming the drug resistance of CRC.

Mitotic Arrest Deficient 2 Like 1 Contributes to Colorectal Cancer Cell Migration, Invasion, and Oxaliplatin Resistance Through the Wnt/β-Catenin Pathway.

Colorectal cancer (CRC) is a highly prevalent malignancy, requiring chemotherapy for advanced stages of the disease. Previously, we found that mitotic arrest deficient 2 like 1 (MAD2L1) was upregulated and facilitated malignant proliferation in CRC. However, the association between MAD2L1 expression and tumor progression, as well as chemotherapy resistance in CRC, remains unclear. The progression capacities of CRC cells were assessed using transwell and wound healing assays, and the resistance to cisplatin in oxaliplatin-resistant CRC cells was assessed using CCK-8 assay and flow cytometry. Relevant protein levels of epithelial-to-mesenchymal transition (EMT) and Wnt/β-catenin pathway were analyzed using western blotting. Revealing the impact of MAD2L1 on metastasis and drug resistance in CRC through inhibition of the Wnt/β-catenin pathway. Knockdown of MAD2L1 attenuated the malignant progression of CRC cells, inhibited EMT, and blocked the Wnt/β-catenin pathway. MAD2L1 was significantly upregulated in oxaliplatin-resistant CRC cells, accompanied by the activation of the Wnt/β-catenin pathway. Knockdown of MAD2L1 effectively reversed oxaliplatin resistance, leading to apoptosis and downregulation of the protein expression levels of β-catenin, P-glycoprotein (P-gp), and ABCG2. After the knockdown of MAD2L1, the inhibition of the Wnt/β-catenin pathway exhibited a synergistic effect, effectively suppressing malignant progression and reversing oxaliplatin resistance in CRC cells. So, knockdown of MAD2L1 suppressed cell malignant progression, equally sensitized resistant CRC cells to oxaliplatin, potentially by blocking the activation of the Wnt/β-catenin pathway.

The role of PIK3CA gene mutations in colorectal cancer and the selection of treatment strategies

PIK3CA gene encodes the p110α catalytic subunit of PI3K, which regulates the PI3K/AKT/mTOR signaling pathway. PIK3CA gene mutation is one of the most common mutations in colorectal cancer (CRC), affecting about 15%–20% of CRC patients. PIK3CA gene mutation leads to the persistent activation of the PI3K/AKT/mTOR signaling pathway, which promotes the proliferation, invasion, metastasis, and drug resistance of CRC. This article provides a summary of the key detection methods for PIK3CA gene mutation, and provides an introduction to the existing colorectal cancer treatments and their practical applications in the clinic. Besides, this article summarizes the role and mechanism of PIK3CA gene mutation in the occurrence and development of CRC. It also explores the relationship between PIK3CA gene mutation and the clinical features and prognosis of CRC. This article focuses on the influence and mechanism of PIK3CA gene mutation on the targeted therapy and immunotherapy of CRC, and discusses the potential value and future direction of PIK3CA gene mutation in the personalized therapy of CRC. We aim to provide new perspectives and ideas for the precise diagnosis and treatment of CRC.

Novel Perspectives in the Management of Colorectal Cancer: Mechanistic Investigations Into the Reversal of Drug Resistance via Active Constituents Derived From Herbal Medicine.

The high incidence and mortality rate of colorectal cancer have become a significant global health burden. Chemotherapy has been the traditional treatment for colorectal cancer and has demonstrated promising antitumor effects, leading to significant improvements in patient survival. However, the development of chemoresistance poses a major challenge during chemotherapy in colorectal cancer, significantly impeding treatment efficacy and affecting patient prognosis. Despite the development of a variety of novel anticolorectal cancer chemotherapy agents, their effectiveness and side effects vary, possibly due to the complex mechanisms of resistance in colorectal cancer. Abnormal drug metabolism or protein targets are the most direct causes of resistance. Further studies have revealed that these resistance mechanisms involve biochemical processes such as altered protein expression, autophagy, and epithelial-mesenchymal transitions. Herbal active ingredients offer an alternative treatment option and have shown promise in reversing colorectal cancer drug resistance. This paper aims to summarize the role of various biochemical processes and key protein targets in the occurrence and maintenance of resistance mechanisms in colorectal cancer. Additionally, it elaborates on the mechanisms of action of herbal active ingredients in reversing colorectal cancer drug resistance. The article also discusses the limitations and opportunities in developing novel anticolorectal cancer drugs based on herbal medicine.

In vivo delivery of PBAE/ZIF-8 enhances the sensitivity of colorectal cancer to doxorubicin through sh-LncRNA ASB16-AS1.

The aim of this study is to investigate the impact of sh-LncRNA ASB16-AS1 on doxorubicin (DOX) resistance in colorectal cancer (CRC). First, an in vitro study was conducted to investigate the effects of LncRNA ASB16-AS1, miR-185-5p, and TEAD1 on drug resistance in CRC cells. Subsequently, utilizing nanotechnology, poly(beta amino esters) (PBAE)/zeolitic imidazolate framework-8 (ZIF-8)@sh-LncRNA ASB16-AS1 nanoparticles (PZSNP) were synthesized and characterized, evaluating their cellular toxicity and hemolytic activity. Finally, a mouse subcutaneous tumor model was established by subcutaneous injection of SW480/DOX cell suspension to investigate the impact of PZSNP on the tumor. Under DOX treatment, downregulation of LncRNA ASB16-AS1, overexpression of miR-185-5p, or downregulation of TEAD1 suppressed the viability and proliferation of drug-resistant CRC cells while promoting apoptosis. Conversely, overexpression of LncRNA ASB16-AS1, inhibition of miR-185-5p, or overexpression of TEAD1 enhanced the viability and proliferation of drug-resistant CRC cells while inhibiting apoptosis. The synthesized PZSNP exhibited a spherical shape with an average particle size of 123.6 nm, possessed positive charge, displayed good stability. It effectively encapsulated shRNA and displayed low cellular toxicity and hemolytic activity. Under DOX treatment, significant tumor necrosis was observed in the PZSNP group, and tumor growth was suppressed without causing weight loss. LncRNA ASB16-AS1, miR-185-5p, and TEAD1 are involved in regulating cell viability, proliferation, and apoptosis, contributing to drug resistance in CRC cells. sh-LncRNA ASB16-AS1 enhances the sensitivity of CRC cells to DOX during treatment, and in vivo delivery of PZSNP may serve as an effective strategy to overcome chemotherapy resistance in CRC.

Decoding the Methylation Patterns of ABC Transporters in Colorectal Cancer

Colorectal cancer (CRC) is a significant global health concern, posing a major threat to morbidity and mortality rates. The molecular mechanisms that drive CRC, particularly the DNA methylation patterns in ATP-binding cassette (ABC) genes, have attracted considerable attention because of their potential roles in CRC drug resistance, initiation, and progression. This study aimed to investigate the methylation patterns of ABC genes in CRC using a high-throughput microarray technology. Microarray methylation data from CRC and adjacent normal tissues were subjected to preprocessing, differential methylation analysis, and correlation analysis using the MethSurv tool for a detailed study of methylation patterns. The study revealed global hypomethylation of 43 ABC transporters and two pseudogenes in CRC compared to normal tissues. Receiver operating characteristic curve analysis identified 369 CpG sites as potential biomarkers for CRC diagnosis, with area under the curve values ranging from acceptable to outstanding. Survival analysis demonstrated the correlation between DNA methylation of individual CpG sites and patient survival probability in colon and rectal adenocarcinoma datasets from The Cancer Genome Atlas. The study provides insights into the epigenetic landscape of ABC genes in CRC, highlighting their potential roles in drug resistance, disease initiation, and progression. The findings offer opportunities for developing innovative therapeutic approaches and improving patient outcomes in the fight against CRC. Further research is needed to validate these results and investigate the functional implications of ABC gene methylation in CRC pathogenesis and treatment response.

Merging Metabolic Modeling and Imaging for Screening Therapeutic Targets in Colorectal Cancer.

Cancer-associated fibroblasts (CAFs) play a key role in metabolic reprogramming and are well-established contributors to drug resistance in colorectal cancer (CRC). To exploit this metabolic crosstalk, we integrated a systems biology approach that identified key metabolic targets in a data-driven method and validated them experimentally. This process involved a novel machine learning-based method to computationally screen, in a high-throughput manner, the effects of enzyme perturbations predicted by a computational model of CRC metabolism. This approach reveals the network-wide effects of metabolic perturbations. Our results highlighted hexokinase (HK) as the crucial target, which subsequently became our focus for experimental validation using patient-derived tumor organoids (PDTOs). Through metabolic imaging and viability assays, we found that PDTOs cultured in CAF-conditioned media exhibited increased sensitivity to HK inhibition, confirming the model predictions. Our approach emphasizes the critical role of integrating computational and experimental techniques in exploring and exploiting CRC-CAF crosstalk.

TsRNA-GlyGCC promotes colorectal cancer progression and 5-FU resistance by regulating SPIB

BackgroundtRNA-derived small RNAs (tsRNAs) are newly discovered non-coding RNA, which are generated from tRNAs and are reported to participate in several biological processes in diseases, especially cancer; however, the mechanism of tsRNA involvement in colorectal cancer (CRC) and 5-fluorouracil (5-FU) is still unclear.MethodsRNA sequencing was performed to identify differential expression of tsRNAs in CRC tissues. CCK8, colony formation, transwell assays, and tumor sphere assays were used to investigate the role of tsRNA-GlyGCC in 5-FU resistance in CRC. TargetScan and miRanda were used to identify the target genes of tsRNA-GlyGCC. Biotin pull-down, RNA pull-down, luciferase assay, ChIP, and western blotting were used to explore the underlying molecular mechanisms of action of tsRNA-GlyGCC. The MeRIP assay was used to investigate the N(7)-methylguanosine RNA modification of tsRNA-GlyGCC.ResultsIn this study, we uncovered the feature of tsRNAs in human CRC tissues and confirmed a specific 5’ half tRNA, 5’tiRNA-Gly-GCC (tsRNA-GlyGCC), which is upregulated in CRC tissues and modulated by METTL1-mediated N(7)-methylguanosine tRNA modification. In vitro and in vivo experiments revealed the oncogenic role of tsRNA-GlyGCC in 5-FU drug resistance in CRC. Remarkably, our results showed that tsRNA-GlyGCC modulated the JAK1/STAT6 signaling pathway by targeting SPIB. Poly (β-amino esters) were synthesized to assist the delivery of 5-FU and tsRNA-GlyGCC inhibitor, which effectively inhibited tumor growth and enhanced CRC sensitive to 5-FU without obvious adverse effects in subcutaneous tumor.ConclusionsOur study revealed a specific tsRNA-GlyGCC-engaged pathway in CRC progression. Targeting tsRNA-GlyGCC in combination with 5-FU may provide a promising nanotherapeutic strategy for the treatment of 5-FU-resistance CRC.Graphical

Vasorin (VASN) overexpression promotes pulmonary metastasis and resistance to adjuvant chemotherapy in patients with locally advanced rectal cancer

BackgroundLARC patients commonly receive adjuvant therapy, however, hidden micrometastases still limit the improvement of OS. This study aims to investigate the impact of VASN in rectal cancer with pulmonary metastasis and understand the underlying molecular mechanisms to guide adjuvant chemotherapy selection.MethodsSequencing data from rectal cancer patients with pulmonary metastasis from Sun Yat-sen University Cancer Center (SYSUCC) and publicly available data were meticulously analyzed. The functional role of VASN in pulmonary metastasis was validated in vivo and in vitro. Coimmunoprecipitation (co-IP), immunofluorescence, and rescue experiments were conducted to unravel potential molecular mechanisms of VASN. Moreover, VASN expression levels in tumor samples were examined and analyzed for their correlations with pulmonary metastasis status, tumor stage, adjuvant chemotherapy benefit, and survival outcome.ResultsOur study revealed a significant association between high VASN expression and pulmonary metastasis in LARC patients. Experiments in vitro and in vivo demonstrated that VASN could promote the cell proliferation, metastasis, and drug resistance of colorectal cancer. Mechanistically, VASN interacts with the NOTCH1 protein, leading to concurrent activation of the NOTCH and MAPK pathways. Clinically, pulmonary metastasis and advanced tumor stage were observed in 90% of VASN-positive patients and 53.5% of VASN-high patients, respectively, and VASN-high patients had a lower five-year survival rate than VASN-low patients (26.7% vs. 83.7%). Moreover, the Cox analysis and OS analysis indicated that VASN was an independent prognostic factor for OS (HR = 7.4, P value < 0.001) and a predictor of adjuvant therapy efficacy in rectal cancer.ConclusionsOur study highlights the role of VASN in decreasing drug sensitivity and activating the NOTCH and MAPK pathways, which leads to tumorigenesis and pulmonary metastasis. Both experimental and clinical data support that rectal cancer patients with VASN overexpression detected in biopsies have a higher risk of pulmonary metastasis and adjuvant chemotherapy resistance.

Advancements in Research and Treatment Applications of Patient-Derived Tumor Organoids in Colorectal Cancer.

Colorectal cancer (CRC) remains a significant health burden globally, being the second leading cause of cancer-related mortality. Despite significant therapeutic advancements, resistance to systemic antineoplastic agents remains an important obstacle, highlighting the need for innovative screening tools to tailor patient-specific treatment. This review explores the application of patient-derived tumor organoids (PDTOs), three-dimensional, self-organizing models derived from patient tumor samples, as screening tools for drug resistance in CRC. PDTOs offer unique advantages over traditional models by recapitulating the tumor architecture, cellular heterogeneity, and genomic landscape and are a valuable ex vivo predictive drug screening tool. This review provides an overview of the current literature surrounding the use of PDTOs as an instrument for predicting therapy responses in CRC. We also explore more complex models, such as co-cultures with important stromal cells, such as cancer-associated fibroblasts, and organ-on-a-chip models. Furthermore, we discuss the use of PDTOs for drug repurposing, offering a new approach to identify the existing drugs effective against drug-resistant CRC. Additionally, we explore how PDTOs serve as models to gain insights into drug resistance mechanisms, using newer techniques, such as single-cell RNA sequencing and CRISPR-Cas9 genome editing. Through this review, we aim to highlight the potential of PDTOs in advancing our understanding of predicting therapy responses, drug resistance, and biomarker identification in CRC management.

Mechanisms of drug resistance in nutrient-depleted colorectal cancer cells: insights into lysosomal and mitochondrial drug sequestration.

This Review delves into the mechanisms behind drug resistance in colorectal cancer (CRC), particularly examining the role of nutrient depletion and its contribution to multidrug resistance (MDR). The study highlights metabolic adaptations of cancer cells as well as metabolic adaptations of cancer cells under low nutrient availability, including shifts in glycolysis and lipid metabolism. It emphasizes the significance of MDR1 and its encoded efflux transporter, P-glycoprotein (P-gp/B1), in mediating drug resistance and how pathways such as HIF1α, AKT, and mTOR influence the expression of P-gp/B1 under limited nutrient availability. Additionally, the Review explores the dual roles of autophagy in drug sensitivity and resistance under nutrient limited conditions. It further investigates the involvement of lysosomes and mitochondria, focusing on their roles in drug sequestration and the challenges posed by lysosomal entrapment facilitated by non-enzymatic processes and ABC transporters like P-gp/B1. Finally, the Review underscores the importance of understanding the interplay between drug sequestration, lysosomal functions, nutrient depletion, and MDR1 gene modulation. It suggests innovative strategies, including structural modifications and nanotechnology, as promising approaches to overcoming drug resistance in cancer therapy.

Polyunsaturated Fatty Acids in Quinoa Induce Ferroptosis of Colon Cancer by Suppressing Stemness.

Polyunsaturated fatty acids (PUFAs) are essential nutrients for the human body, playing crucial roles in reducing blood lipids, anti-inflammatory responses, and anticancer effect. Quinoa is a nutritionally sound food source, rich in PUFAs. This study investigates the role of quinoa polyunsaturated fatty acids (QPAs) on quelling drug resistance in colorectal cancer. The results reveal that QPA downregulates the expression of drug-resistant proteins P-gp, MRP1, and BCRP, thereby enhancing the sensitivity of colorectal cancer drug-resistant cells to the chemotherapy drug. QPA also inhibits the stemness of drug-resistant colorectal cancer cells by reducing the expression of the stemness marker CD44. Consequently, it suppresses the downstream protein SLC7A11 and leads to ferroptosis. Additionally, QPA makes the expression of ferritin lower and increases the concentration of free iron ions within cells, leading to ferroptosis. Overall, QPA has the dual-function reversing drug resistance in colorectal cancer by simultaneously inhibiting stemness and inducing ferroptosis. This study provides a new option for chemotherapy sensitizers and establishes a theoretical foundation for the development and utilization of quinoa.

Overcoming the Tumor Collagen Barriers: A Multistage Drug Delivery Strategy for DDR1-Mediated Resistant Colorectal Cancer Therapy.

The extracellular matrix (ECM) is critical for drug resistance in colorectal cancer (CRC). The abundant collagen within the ECM significantly influences tumor progression and matrix-mediated drug resistance (MMDR) by binding to discoidin domain receptor 1 (DDR1), but the specific mechanisms by which tumor cells modulate ECM via DDR1 and ultimately regulate TME remain poorly understand. Furthermore, overcoming drug resistance by modulating the tumor ECM remains a challenge in CRC treatment. In this study, a novel mechanism is elucidated by which DDR1 mediates the interactions between tumor cells and collagen, enhances collagen barriers, inhibits immune infiltration, promotes drug efflux, and leads to MMDR in CRC. To address this issue, a multistage drug delivery system carrying DDR1-siRNA and chemotherapeutic agents is employed to disrupt collagen barriers by silencing DDR1 in tumor, enhancing chemotherapy drugs diffusion and facilitating immune infiltration. These findings not only revealed a novel role for collagen-rich matrix mediated by DDR1 in tumor resistance, but also introduced a promising CRC treatment strategy.

Fe-MOF nanoplatform: Specifically overcoming oxaliplatin resistance in colorectal cancer through multifaceted pathways

Oxaliplatin (OXA) is a widely used chemotherapy drug for advanced colorectal cancer (CRC), yet resistance frequently and rapidly develops in patients. Here, we explored a Fe-based metal-organic framework (Fe-MOF) as a nanoplatform to simultaneously deliver OXA and a nitric oxide (NO) donor, specifically l-Arginine (L-Arg). The aim was to overcome OXA resistance in CRC cells, thereby enhancing the anticancer efficacy against drug-resistant CRC. Due to the abundant glutathione (GSH) in tumor tissue, Fe3+ in Fe-MOF undergoes reduction to Fe2+, causing the collapse of Fe-MOF structure and the subsequent release of OXA and L-Arg. This process is accompanied by GSH depletion, amplifying the effectiveness of OXA against drug-resistant CRC. Fe2+ further reacts with overexpressed H2O2 to generate •OH, inducing direct cell apoptosis and subsequently reacting with L-Arg to rapidly produce NO. NO plays multifaceted roles in the anti-CRC effect, reversing drug resistance in CRC cells through multiple pathways, inducing apoptosis of CRC cells to initiate gas therapy, and reacting with •OH to generate highly toxic reactive nitrogen species for cancer cell destruction. This synergistic strategy effectively addresses the challenge of drug resistance in CRC, offering a promising avenue for enhancing the clinical effectiveness of OXA in cases resistant to conventional treatment.

A novel Senescence-Based prognostic model unveils tumor interactions and drug resistance in colorectal cancer

BackgroundIn China, CRC incidence is escalating. The main hurdles are heterogeneity and drug resistance. This research delves into cellular senescence in CRC, aiming to devise a prognostic model and pinpoint mechanisms impacting drug resistance. MethodsMendelian randomization (MR) analysis confirmed the association between CRC and cellular aging. The Cancer Genome Atlas (TCGA)-CRC data served as the training set, with GSE38832 and GSE39582 as validation sets. Various bioinformatics methods were employed to construct and validate a risk model. CRC cells with NADPH Oxidase 4 (NOX4) knockout were generated using CRISPR-Cas9 technology. Protein blotting and colony formation assays elucidated the role of NOX4 in CRC cell aging and drug resistance. ResultsA prognostic model, derived from dataset analysis, uncovered a link between high-risk groups and cancer progression. Notable differences in the tumor microenvironment were observed between risk groups. Finally, NOX4 was found to be linked with aging and drug resistance in CRC. ConclusionThis research presents a novel senescence-based CRC prognosis model. It identifies NOX4′s role in CRC drug resistance, suggesting it is a potential treatment target.

Abstract 374: Hypoxia-induced mitochondrial glutathione transporter expression causes drug resistance in colorectal cancer

Abstract Colorectal cancer (CRC) is the third most common type of cancer worldwide, with higher incidence and mortality rates. In order to adapt stress conditions during cancer progression, the cancer cells will be subject to metabolism reprogramming to increase energy production and remove hazardous substances. One of the important organelles, mitochondria is responsible for cellular ATP production, ion homeostasis, and several metabolic pathways. Therefore, mitochondria require a series of transporters called solute carrier family 25 (SLC25) to transport metabolites crossing the mitochondrial inner membrane, and dysregulation of those transporters causes abnormal cell morphology and diseases. In this study, members of the SLC25 family were analyzed in CRC via bioinformatics analysis, and a mitochondrial glutathione transporter was identified to overexpress in several public datasets of CRC and our own clinical specimens. In addition, its role has not been reported in any disease, including cancer. To systemically analyze the underlying mechanism causing overexpression of glutathione transporter during CRC progression, several stress conditions had been applied to colon cancer cells. However, only hypoxia was identified to induce its protein expression but not mRNA expression. Since a previous study reported that glutathione deprivation induced its protein expression, hypoxia didn’t alter the abundance of glutathione level suggesting that another glutathione-independent regulatory mechanism might be involve it. Interestingly, our findings revealed that hypoxia-induced glutathione transporter protein expression was mediated through the activation of internal ribosome binding site-mediated translation under hypoxia. To identify the potential role of glutathione transporter during colon cancer progression, its mitochondrial metabolite profiles from knockout cells of previous studies were further analyzed and identified that the changes of metabolites were associated with the urea cycle which had been reported to be associated with the sensitivity of oxaliplatin and 5-fluorouracil (5-FU) in cancer treatment. Importantly, our results showed that hypoxia-attenuated those chemotherapeutic effects were abolished by loss of glutathione transporter in colon cancer cells, indicating its crucial role in hypoxia-induced drug resistance. In conclusion, our study shows that glutathione transporter increased by hypoxia might lead to drug resistance of cancer therapy in colon cancer. Citation Format: Chin-Chun Lin. Hypoxia-induced mitochondrial glutathione transporter expression causes drug resistance in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 374.

Abstract 306: The role of exosomal UBE2R2 in colorectal cancer drug resistance

Abstract Background: Ctherapy resistance has been a major barrier against successful theratment. Exosome (EV), an important intercellular communication mediator, participates in a highly and complex network that drug resistance of cancer cells. EV has been reported to be able to transfer drug resistance from drug-resistant tumor cells to adjacent drug-sensitive cells. We identified a novel target, UBE2R2, based on our previous exosome proteomics analysis of resistant colorectal cancer cell lines. The main goal of this study is to validate the underlying mechanisms leading to chemotherapy resistance. Methods: We isolated EV from drug resistant cancer cell lines including coloractal cancer cell lines (HCT116-OXAR, DLD-1 OXA-R, DLD-1-OXA-R/SN38) its parental cell lines (HCT116, DLD-1) using the ExoLutE isolation kits based on a combination of multiple isolation techniques. Based on the existing data (proteomic analysis), we conducted experiments to elucidate the functions and mechanisms involved in cancer resistance of the identified UBE2R2. Cell viability assay and invasion asaay were performed to assess the effects of EVs drived from drug resistance colorectal cells on oxaliplatin and irinotecan resistance. In addition, cells transfected with siControl and siUBE2R2 were treated with oxaliplatin to access the relative UBE2R2 drug resistance effect. To explore the related mechanisms, we performed real time PCR and western blot to identify the UBE2R2-SMYD3-P53 pathway, and FACS analysis to confirm apoptosis. Additionally, TMA samples were utilized to confirm resistance according to patient stage, and UBE2R2 expression was validated by immunohistological methods. Results: UBE2R2, which is involved in ubiquitination, was most prominently expressed in resistant cell lines compared to controls in our previous proteomic analysis. Based on these results, we found that cell lines treated with exosomes which were derived from resistant cell lines showed lower sensitivity to the drug. Notably, treatment of resistant cell lines with siUBE2R2 resulted in increased sensitivity, confirming the involvement of UBE2R2 in resistance. As a possible mechanism in which UBE2R2 may be involved, western analysis targeting the SMYD-P53 mechanism showed that the combination of UBE2R2-SMYD3-p53 promoted the ubiquitination and degradation of p53. Analyzed using TMA patient samples, we found that the expression of UBE2R2 increased towards more advenced stage. Conclusion: Our results suggest a novel mechanism of chemotherapy resistance may be associated with UBE2R2. Exosome (including UBE2R2) which was drived from drug resistance cells may induce oxaliplatin and irinotecan resistance in parental colorectal cells via regulation of SMYD3-UBE2R2-P53 signaling pathway, which will be useful for investigating a potential clinical target in prediction drug resistance. Citation Format: Chi Hoon Maeng, Minji Choi. The role of exosomal UBE2R2 in colorectal cancer drug resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 306.

PI3K/Akt/mTOR Signaling Pathway as a Target for Colorectal Cancer Treatment.

In the last decade, pathway-specific targeted therapy has revolutionized colorectal cancer (CRC) treatment strategies. This type of therapy targets a tumor-vulnerable spot formed primarily due to an alteration in an oncogene and/or a tumor suppressor gene. However, tumor heterogeneity in CRC frequently results in treatment resistance, underscoring the need to understand the molecular mechanisms involved in CRC for the development of novel targeted therapies. The phosphatidylinositol 3-kinase/protein kinase B/mammalian target of the rapamycin (PI3K/Akt/mTOR) signaling pathway axis is a major pathway altered in CRC. The aberrant activation of this pathway is associated with CRC initiation, progression, and metastasis and is critical for the development of drug resistance in CRC. Several drugs target PI3K/Akt/mTOR in clinical trials, alone or in combination, for the treatment of CRC. This review aims to provide an overview of the role of the PI3K/Akt/mTOR signaling pathway axis in driving CRC, existing PI3K/Akt/mTOR-targeted agents against CRC, their limitations, and future trends.

The potential therapeutic effect of melatonin in oxaliplatin combination therapy against chemoresistant colorectal cancer cells.

Oxaliplatin is one of the main therapeutics in colorectal cancer (CRC) chemotherapy. However, in light of multidrug resistance (MDR) phenotype development, the efficacy of oxaliplatin has decreased. This study aimed to assess the potential therapeutic effect of melatonin in oxaliplatin combination therapy for drug-resistant colorectal cancer cells. Initially, the oxaliplatin-resistant cell line was created of LS174T (LS174T/DR) by using the oxaliplatin IC50 concentration and resting cycles. MTT assays and flow cytometry were applied for assessing cell viability and apoptotic cells. The mRNA expression level of Bax, Bcl2, MT1, MT2, and ABCB1 as well as protein levels of ABCB1, Bcl2, BAX were measured by the qRT-PCR and western blot techniques respectively. P-gp activity was assessed by Rho123 staining. The IC50 concentration of oxaliplatin in resistant cells was increased from 500.7 ± 0.2 nM to 7119 ± 0.1 nM. Bcl2, MT1, MT2, and ABCB1 mRNA plus protein expression levels of Bcl2 and ABCB1 were significantly reduced in resistant cells, along with a marked increase in Bax mRNA and protein levels compared to parental cells. Rho 123 staining revealed a marked reduction in P-gp activities in the combination-treated group compared to the oxaliplatin-treated group. The results of cytotoxicity assays, MTT, and flow cytometry revealed that the combination of melatonin and oxaliplatin exerts synergistic effects on induction of oxaliplatin's cytotoxicity in CRC. Our research suggests that combining the treatments of melatonin and oxaliplatin may be considered as a new approach to overcoming oxaliplatin resistance in CRC patients.

Development and Nanoparticle-Mediated Delivery of Novel MDM2/MDM4 Heterodimer Peptide Inhibitors to Enhance 5-Fluorouracil Nucleolar Stress in Colorectal Cancer Cells.

Colorectal cancer (CRC) often involves wild-type p53 inactivation by MDM2 and MDM4 overexpression, promoting tumor progression and resistance to 5-fluoruracil (5-FU). Disrupting the MDM2/4 heterodimer can proficiently reactivate p53, sensitizing cancer cells to 5-FU. Herein, we developed 16 peptides based on Pep3 (1), the only known peptide acting through this mechanism. The new peptides, notably 3 and 9, showed lower IC50 values than 1. When incorporated into tumor-targeted biodegradable nanoparticles, these exhibited cytotoxicity against three different CRC cell lines. Notably, NPs/9 caused a significant increase in p53 levels associated with a strong increment of its main downstream target p21 inducing apoptosis. Also, the combined treatment of 9 with 5-FU caused the activation of nucleolar stress and a synergic apoptotic effect. Hence, the co-delivery of MDM2/4 heterodimer disruptors with 5-FU through nanoparticles might be a promising strategy to overcome drug resistance in CRC.