5-Fluorouracil resistance due to sphingosine kinase 2 overexpression in colorectal cancer is associated with myeloid-derived suppressor cell-mediated immunosuppressive effects.

PURPOSE: Colorectal cancer (CRC) is one of the top five cancer-related causes of mortality globally. Acquired resistance has hindered the effectiveness of 5-fluorouracil (5-FU), the main chemotherapeutic drug used to treat CRC. Sphingosine kinase 2 (SphK2) may be a cancer treatment target and involved in 5-FU resistance. METHODS: Cell growth was examined using MTT and clone formation assays for SphK2 expression. To identify immune cells in mice, flow cytometry was performed. West blotting demonstrated alterations in cell division and inflammation-related proteins. SphK2 levels and inflammation-related variables were studied using Elisa. RESULTS: Due to SphK2 overexpression, immunosuppression, and 5-FU resistance are caused by the development of myeloid-derived suppressor cells (MDSCs) subsequent to IL-6/STAT3 activation and alterations in the arginase (ARG-1) protein. After therapy, the combination of SphK2 inhibitors and 5-FU can effectively suppress MDSCs while increasing CD4+ and CD8+ T cell infiltration into the tumor microenvironment, lowering tumor burden, and exhibiting a therapeutic impact on CRC. CONCLUSIONS: Our findings suggest that 5-FU treatment combined with simultaneous Spkh2 inhibition by ABC294640 has anti-tumor synergistic effects by influencing multiple effects on tumor cells, T cells, and MDSCs, potentially improving the poor prognosis of colorectal cancer patients.

Innovative Strategies to Combat 5-Fluorouracil Resistance in Colorectal Cancer: The Role of Phytochemicals and Extracellular Vesicles.

Colorectal cancer (CRC) is a significant public health challenge, with 5-fluorouracil (5-FU) resistance being a major obstacle to effective treatment. Despite advancements, resistance to 5-FU remains formidable due to complex mechanisms such as alterations in drug transport, evasion of apoptosis, dysregulation of cell cycle dynamics, tumor microenvironment (TME) interactions, and extracellular vesicle (EV)-mediated resistance pathways. Traditional chemotherapy often results in high toxicity, highlighting the need for alternative approaches with better efficacy and safety. Phytochemicals (PCs) and EVs offer promising CRC therapeutic strategies. PCs, derived from natural sources, often exhibit lower toxicity and can target multiple pathways involved in cancer progression and drug resistance. EVs can facilitate targeted drug delivery, modulate the immune response, and interact with the TME to sensitize cancer cells to treatment. However, the potential of PCs and engineered EVs in overcoming 5-FU resistance and reshaping the immunosuppressive TME in CRC remains underexplored. Addressing this gap is crucial for identifying innovative therapies with enhanced efficacy and reduced toxicities. This review explores the multifaceted mechanisms of 5-FU resistance in CRC and evaluates the synergistic effects of combining PCs with 5-FU to improve treatment efficacy while minimizing adverse effects. Additionally, it investigates engineered EVs in overcoming 5-FU resistance by serving as drug delivery vehicles and modulating the TME. By synthesizing the current knowledge and addressing research gaps, this review enhances the academic understanding of 5-FU resistance in CRC, highlighting the potential of interdisciplinary approaches involving PCs and EVs for revolutionizing CRC therapy. Further research and clinical validation are essential for translating these findings into improved patient outcomes.

Jianpi Jiedu decoction reverses 5-fluorouracil resistance in colorectal cancer by suppressing the xCT/GSH/GPX4 axis to induce ferroptosis.

Introduction: Innate and acquired chemoresistance in colorectal cancer (CRC) often results in 5-fluorouracil (5-FU) treatment failure. This study aimed to investigate the potential of Jianpi Jiedu (JPJD) decoction to reverse 5-FU resistance in CRC and clarify its potential mechanism of action. Methods: The CCK-8 assay was employed to assess cell activity. Flow cytometry was employed to assess various parameters including cell apoptosis, cell cycle distribution, P-glycoprotein (P-gp) activity, reactive oxygen species levels, and lipid peroxidation. Metabolomics analysis was conducted to identify differentially expressed metabolites. Western blotting was utilized for protein expression analysis. Results: In this study, we demonstrated that the combined JPJD and 5-FU treatment reversed 5-FU resistance in HCT8/5-FU cells, inducing cell apoptosis, causing G2/M-phase cell cycle arrest, and reducing P-gp protein expression and activity. Metabolomics analysis revealed ferroptosis as a key pathway in the development of 5-FU resistance. Furthermore, the combination treatment reversed drug resistance primarily by impacting ferroptosis and triggering critical ferroptosis events through the suppression of the cystine/glutamate transporter (xCT)/glutathione (GSH)/glutathione peroxidase (GPX4) axis. Conclusion: JPJD decoction primarily suppressed the xCT/GSH/GPX4 axis to trigger ferroptosis, thereby effectively reversing 5-FU resistance in colorectal cancer (CRC).

MiR-22-3p Inhibits 5-Fluorouracil Resistance in Cholangiocarcinoma Cells Through PTEN/PI3K/AKT Axis.

Cholangiocarcinoma (CCA) is a prevalent and highly lethal form of cancer globally. Although microRNAs (miRNAs) have been implicated in the advancement of CCA, their potential influence on 5-fluorouracil (5-Fu) resistance in CCA remains to be fully elucidated. Here, in this study, we investigated the impact of miR-22-3p on CCA resistance. Our investigation involved bioinformatics analysis, which revealed an association between miR-22-3p and the progression, diagnosis, and patient survival of CCA. Furthermore, we validated a notable downregulation of miR-22-3p expression in CCA cell lines. Elevated levels of miR-22-3p inhibit the activity and proliferation of 5-Fu-resistant CCA cell lines. In addition, we confirmed that phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a target gene of miR-22-3p, and its expression correlates with the survival of CCA patients. Reduced PTEN expression enhances apoptosis in 5-Fu-resistant CCA cells. Meanwhile, we verified the existence of the miR-22-3p/PTEN/phosphatidylinositol-3 kinase (PI3K)/Protein kinase B (AKT) regulatory networks in CCA, influencing the sensitivity of CCA cells to 5-Fu. In conclusion, our findings suggest that miR-22-3p acts as a tumor suppressor. Its overexpression inhibits the PTEN/PI3K/AKT axis, promoting cell apoptosis and enhancing CCA sensitivity to 5-Fu.