Siriporn Jitkaew

Ferroptosis resistance is a major challenge in cancer therapy, contributing to poor prognosis and unsatisfactory treatment outcomes. Thus, identifying key regulators of ferroptosis is essential for developing strategies to overcome this limitation. Mixed lineage kinase domain-like protein (MLKL) is well established as the executioner of necroptosis, but emerging evidence suggests broader functions beyond necroptosis. A previous study demonstrated that MLKL regulates ferroptosis in an acute kidney injury model. However, its role in ferroptosis regulation in cancer remains largely unexplored. Bioinformatics analyses revealed that MLKL expression positively correlates with glutathione metabolism-related genes in colorectal cancer (CRC) patients and with reduced sensitivity to GPX4 inhibitors across pan-cancer cell lines. Functional studies demonstrated that MLKL depletion sensitizes not only CRC cells but also multiple cancer cell types to ferroptosis induced by GPX4 inhibitors. Mechanistically, MLKL-deficient CRC cells exhibited reduced intracellular glutathione levels and dysregulation of the NRF2/KEAP1/SLC7A11 antioxidant axis. However, KEAP1 knockdown in MLKL-depleted cells partially reduced ferroptosis sensitivity, indicating that additional mechanisms are involved. Proteomic analysis identified CHMP5, a component of the ESCRT-III membrane repair machinery, as a key downstream effector associated with MLKL. MLKL depletion suppressed CHMP5 expression and impaired its translocation to the plasma membrane during ferroptosis induction. Consistent with defective membrane repair, MLKL-knockdown CRC cells exhibited increased HMGB1 release following GPX4 inhibitor treatment, indicating enhanced membrane damage. Notably, CHMP5 overexpression reduced ferroptosis in MLKL-knockdown cells, highlighting that MLKL regulates ferroptosis susceptibility in part through CHMP5-dependent ESCRT-III signaling. This study reveals a previously unrecognized role for MLKL in ferroptosis regulation through coordinating NRF2/KEAP1/SLC7A11-mediated glutathione metabolism and ESCRT-III-dependent membrane repair. These findings identify MLKL as a potential regulator of ferroptosis resistance and warrant further studies to evaluate the therapeutic relevance of MLKL-targeting strategies in colorectal cancer.

5-Fluorouracil (5-FU) is one of the most widely used chemotherapeutic agents for various cancers, including cholangiocarcinoma (CCA) and colorectal cancer (CRC). However, its therapeutic efficiency has remained unsatisfactory. A better understanding of the molecular mechanisms underlying 5-FU responsiveness is therefore crucial for developing more effective treatment strategies and improving patient survival. Mixed lineage kinase domain-like protein (MLKL), a key regulator of necroptosis, has been implicated in cancer progression and therapeutic response. However, the exact roles of MLKL in modulating chemotherapy response, particularly 5-FU, has also remained unknown. Through a comprehensive bioinformatics analysis, we identified a significant association between high MLKL expression and poor therapeutic outcomes in CCA and CRC patients treated with 5-FU. Moreover, higher MLKL expression was detected in CRC patients who were clinically unresponsive to 5-FU-based treatments compared to responders, suggesting a crucial role of MLKL in mediating 5-FU response. Of particular interest, MLKL depletion sensitized CRC cells to 5-FU and enhanced its tumor-suppressive effects in a xenograft mouse model by promoting apoptosis. We propose that MLKL suppression potentiate TNF-α/TNFR-I-mediated apoptotic signaling, potentially by prolonging TNFR-I retention within the early endosome and delaying its degradation upon 5-FU treatment. Notably, silencing of TNFR-I attenuated 5-FU-induced cell death in MLKL-knockdown cells. These findings provide novel insights into previously unrecognized roles of MLKL in modulating 5-FU responsiveness and highlight MLKL as a potential predictive and therapeutic target to improve 5-FU efficacy in precision cancer therapy.

Cholangiocarcinoma (CCA) is an aggressive malignancy with limited treatment options. Despite the approval of chemotherapy and immune checkpoint inhibitors (ICIs) in clinical practice, treatment outcomes remain poor, largely due to the poorly immunogenic tumor microenvironment associated with this type of carcinoma. Necroptosis, an inflammatory form of programmed cell death, has emerged as a promising therapeutic target for stimulating antitumor immunity. Our previous study linked necroptosis to increased CD8 + T cell infiltration and T cell-induced PD-L1 expression in CCA cells, suggesting its role in enhancing ICI efficacy. However, the underlying mechanisms by which necroptosis-activated T cells induce PD-L1 expression remain unclear. Here, we investigate how necroptosis in CCA cells influences T cell response, which subsequently promotes PD-L1 expression, thus providing insights for optimizing necroptosis-based therapies in combination with ICIs. Conditioned medium from gemcitabine-induced necroptotic CCA cells triggers PBMC-derived T cell activation by upregulating the surface activation marker CD69 and promoting cytokine release, primarily IL-6 and IL-1β. This cytokine release subsequently induces PD-L1 expression in CCA cells via IL-6, as confirmed by IL-6 neutralizing antibodies. Furthermore, T cell killing assays demonstrated that pembrolizumab, an anti-PD-1 inhibitor, enhances T cell cytotoxicity against PD-L1-upregulated CCA cells. Additionally, bioinformatics analysis identified an IL-6 signaling-related gene signature associated with ICI responsiveness, suggesting potential biomarkers for personalized treatment strategies. This study highlights that necroptosis shapes the tumor immune microenvironment by promoting T cell activation and IL-6-mediated PD-L1 upregulation in CCA cells. These findings support the integration of necroptosis-based therapies with ICIs as a sequential chemo-immunotherapy strategy. Additionally, the identified IL-6 signaling-related gene signature may serve as a biomarker for patient stratification and personalized treatment in CCA.

Cholangiocarcinoma (CCA) is a highly aggressive bile duct cancer with a poor prognosis and high mortality rates, primarily due to the lack of early diagnosis and effective treatments. We have shown that cyclin D and CDK4/6, key regulators of cell cycle progression, are highly expressed in CCA patients. Moreover, high levels of cyclin D, CDK4, and CDK6 are associated with shorter survival in CCA patients, suggesting that cyclin D and CDK4/6 might be potential targets for CCA therapy. However, we have demonstrated that CDK4/6 inhibitor palbociclib monotherapy is less effective in CCA cells. We have identified Cellular Inhibitor of Apoptosis Proteins 1 and 2 (cIAP1/2), NF-κB target genes that their expression is associated with shorter survival in CCA patients, as potential key regulators of the CDK4/6 inhibitor response. We showed that palbociclib, a CDK4/6 inhibitor, increases phosphorylated p65 and its nuclear translocation, resulting in cIAP1/2 upregulation in CCA cells. Therefore, we hypothesized that the combination of a cIAP1/2 antagonist and a CDK4/6 inhibitor might enhance the CDK4/6 inhibitor response. Interestingly, combined treatment with the Smac mimetic LCL161, a cIAP1/2 antagonist, and palbociclib synergistically inhibits cell proliferation and induces cell death in both 2D monolayer and 3D spheroid CCA cultures. We further showed that this combination treatment has less effect on non-tumor cholangiocytes and human peripheral blood mononuclear cells (PBMCs). Our findings demonstrate for the first time that the combined treatment of Smac mimetics and CDK4/6 inhibitors is a promising novel targeted therapy for CCA patients.

Cholangiocarcinoma (CCA) is a bile duct malignancy. Our previous comprehensive analysis showed that ferroptosis-related genes can stratify CCA patients into low-risk and high-risk groups based on survival time. Here, we explored the role of ferroptosis in CCA by analyzing mRNA expression in CCA patients from public databases. We identified acyl-CoA synthetase long chain family member 3 (ACSL3) as a potential ferroptosis suppressor in high-risk CCA patients. Using a panel of CCA cell lines, we confirmed ACSL3 upregulation in CCA cell lines associated with high-risk CCA, correlating this with resistance to the ferroptosis inducer RSL3. Lipidomic analysis revealed increased monounsaturated fatty acid (MUFA)-containing phospholipids in resistant cell lines. ACSL3 silencing sensitized these cells to RSL3. Resistance to ferroptosis was also dependent on exogenous MUFAs and was enhanced by lipid droplet biogenesis inhibition. These findings highlight ACSL3 as a promising target for therapeutic strategies aimed at overcoming ferroptosis resistance in CCA.