In western countries, secondary lymphedema often occurs after cancer treatments. However, lymphedema appears months, sometimes years after treatment suggesting that it is not only a side effect of surgery and may be promoted in part by cancer treatments. In this study, we demonstrate that the first line chemotherapeutic agent 5-Fluorouracil (5-FU) induces lymphatic system damage, thereby increasing the risk of developing lymphedema. We found that metformin, a complex I respiration inhibitor widely used for decades in the treatment of diabetes, protects lymphatic endothelial cells and counteracts the deleterious effects of chemotherapy. Notably, metformin restores the gene expression of key molecules involved in lymphatic system maintenance, including Gata2, Foxc2, and Sox18. In vivo, the vessel collapse induced by 5-FU is not observed in the presence of metformin. In a murine model of lymphedema, metformin reduces the limb volume increased by 5-FU treatment. This is accompanied by a marked reduction in lymph reflux into tissues, a reduced dermal thickening, and disorganized lymphatic proliferation. Mechanistically, metformin prevents lymphatic endothelial cells from mitochondrial superoxide accumulation by restoring maximal respiration, ATP production, and spare respiratory capacity impaired by 5-FU, while also reducing mitochondrial mass. We found that the anti-oxidative effect of metformin is dependent on GATA2 pathway. Altogether, our study suggests that metformin could offer a pharmacological approach for the management of cancer-related secondary lymphedema.
Stress granules (SGs) are non-membranous protein–RNA aggregates that form in the cytoplasm of mammalian cells under various stress conditions. In normal cells, SGs mitigate stress-induced damage by arresting translation. SGs have also been implicated in cancer cell tumor progression and metastasis through their interaction with key signaling pathways. However, their role in oral squamous cell carcinoma (OSCC) remains poorly understood, despite growing interest. In this study, we investigated SG formation and its regulatory effects on tumor progression and metastasis in OSCC. SG markers, including G3BP1, eIF2α, TIAR, and PABP, were significantly overexpressed in OSCC tissues compared with those in adjacent normal tissues. In mouse models established using OSCC cells subjected to hypoxia preconditioning or ISRIB treatment after sodium arsenite-induced stress, suppression of eIF2α phosphorylation was associated with reduced SG formation, tumor growth, and metastatic burden. Moreover, SG formation was elevated during hypoxia-induced stress, highlighting a stress-responsive regulatory mechanism. These findings indicate that SGs promote OSCC progression via eIF2α phosphorylation and might serve as a novel therapeutic target.
Statins lower circulating cholesterol by inhibiting hepatic 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR). However, their clinical use is frequently limited by statin-associated muscle complications, the underlying mechanisms of which remain incompletely understood. Here we demonstrate that lovastatin and atorvastatin induce cellular senescence in hepatocytes and hepatic tissue, as evidenced by increased senescence-associated β-galactosidase (SA-β-gal) activity and induction of the canonical markers p21 and p16. Among senescence-associated secretory phenotype (SASP), insulin-like growth factor-1 (IGF-1) was selectively and significantly reduced. In a transwell coculture system, senescent AML12 hepatocytes impaired C2C12 myogenesis, decreased myotube diameter, and upregulated the muscle atrophy markers Atrogin-1 and MuRF1. Consistent with these in vitro findings, in vivo lovastatin and ezetimibe (LE) exposure increased hepatic SA-β-gal-positive area, elevated p21/p16 expression, and lowered circulating IGF-1. Tibialis anterior muscle displayed reduced fiber cross-sectional area with a smaller-shifted size distribution, heightened atrophy signaling, and diminished AKT/mTOR pathway activation. Together, these findings support a liver-to-muscle endocrine axis in which lovastatin-induced hepatic senescence suppresses IGF-1, secondarily impairing myogenesis and promoting skeletal muscle atrophy via attenuation of AKT/mTOR signaling. Targeting hepatic senescence or restoring IGF-1/AKT/mTOR activity may offer therapeutic strategies to mitigate statin-associated myopathy.
As the predominant microvascular complication of diabetes mellitus that leads to blindness, diabetic retinopathy (DR) still presents a challenge due to the scarcity of effective therapeutic approaches, particularly in its early stage. Here, we observed that the expression of the mitochondrial open-reading-frame of the 12 S rRNA-c (MOTS-c), a mitochondrial-derived peptide, was predominantly localized in retinal endothelial cells. Thus, we combined genetic and pharmacological approaches in vivo and in vitro to explore whether vascular endothelial damage in DR is involved in MOTS-c dysregulation and its underlying mechanism. High glucose exposure reduced the expression of MOTS-c in retinal vasculature. While MOTS-c treatment protected endothelial barrier and ameliorated mitochondrial dysfunction in human retinal endothelial cells with high-glucose-induced injury and streptozotocin-induced diabetic mouse model. Furthermore, in vitro experiments were used to explore the underlying molecular mechanisms for rescuing vascular endothelial damage of MOTS-c. Transcriptomic analyses and lipidomic analyses showed that MOTS-c increased the phospholipase A2 activity and regulated phospholipid metabolism. Among the differentially expressed genes associated with upregulated phospholipase A2 activity, phospholipase A2 group VI (PLA2G6) exhibited the most significant upregulation following MOTS-c treatment. PLA2G6-mediated lipid peroxide degradation served as a primary mediator of protecting the retinal endothelial barrier during MOTS-c treatment, while knockdown of PLA2G6 blocked the protective effect of MOTS-c against vascular endothelial damage in vitro and in vivo. Taken together, our findings identified a novel role of MOTS-c dysregulation mediating vascular endothelial damage in DR and that MOTS-c supplementation was a potential therapeutic approach to regulating phospholipid homeostasis and protecting the endothelial barrier via PLA2G6 against DR.
Tousled-like kinases TLK1 and TLK2 are evolutionarily conserved serine/threonine kinases involved in the DNA damage response and cell cycle regulation; however, their pan-cancer molecular profiles and clinical relevance remain largely unexplored. By integrating multi-omics data from TCGA and GTEx across 33 cancer types, we demonstrate that TLK1 and TLK2 exhibit distinct expression patterns and are associated with patient prognosis in a cancer type-specific manner. Genetic alterations in TLK1 and TLK2 were frequently observed and significantly correlated with multiple markers of genomic instability, including tumor mutation burden, microsatellite instability, and homologous recombination deficiency. Functional experiments showed that knockdown of TLK1 or TLK2 in cancer cell lines markedly increased DNA damage, impaired cellular proliferation, and induced apoptosis, with TLK2 exhibiting a more prominent role in DNA repair processes. Furthermore, both kinases were negatively correlated with immune and stromal scores, and their expression levels were linked to specific immune cell subsets—positively with resting CD4+ T cells and macrophages, but negatively with CD8+ T cells and activated NK cells. Additional functional immune analyses revealed that TLK1/TLK2 expression correlated positively with immune exclusion signatures and MDSC infiltration, rather than with classical T-cell exhaustion markers. Multiplex immunohistochemistry in colorectal cancer tissues further resolved these associations into divergent phenotypes: TLK1-high tumors exhibited reduced T cell infiltration consistent with immune exclusion, whereas TLK2-high tumors showed Treg enrichment and CD39 upregulation indicative of an immunosuppressive microenvironment. Notably, TLK1 and TLK2 expression demonstrated predictive utility for responses to chemotherapy and immunotherapy across several malignancies. Our findings underscore the multifaceted roles of TLK1 and TLK2 in tumorigenesis and tumor immune modulation, supporting their potential as prognostic biomarkers and promising therapeutic targets in precision oncology.
