Background: The mechanism by which glioblastoma evades temozolomide (TMZ)-induced cytotoxicity is largely unknown. We hypothesized that mitochondria plays a role in this process. Methods: RNA transcriptomes were obtained from tumor samples and online databases. Expression of different proteins was manipulated using RNA interference or gene amplification. Autophagic activity and mitochondrial metabolism was assessed in vitro using the respective cellular and molecular assays. In vivo analysis were also carried out in this study. Results: High SH3GLB1 gene expression was found to be associated with higher disease grading and worse survival profiles. Single-cell transcriptome analysis of clinical samples suggested that SH3GLB1 and the altered gene levels of oxidative phosphorylation (OXPHOS) were related to subsets expressing a tumor-initiating cell signature. The SH3GLB1 protein was regulated by promoter binding with Sp1, a factor associated with TMZ resistance. Downregulation of SH3GLB1 resulted in retention of TMZ susceptibility, upregulated p62, and reduced LC3B-II. Autophagy inhibition by SH3GLB1 deficiency and chloroquine resulted in attenuated OXPHOS expression. Inhibition of SH3GLB1 in resistant cells resulted in alleviation of TMZ-enhanced mitochondrial metabolic function, such as mitochondrial membrane potential, mitochondrial respiration, and ATP production. SH3GLB1 modulation could determine tumor susceptibility to TMZ. Finally, in animal models, resistant tumor cells with SH3GLB1 knockdown became resensitized to the anti-tumor effect of TMZ, including the suppression of TMZ-induced autophagy and OXPHOS. Conclusions: SH3GLB1 promotes TMZ resistance via autophagy to alter mitochondrial function. Characterizing SH3GLB1 in glioblastoma may help develop new therapeutic strategies against this disease in the future.

DJ-1 is an oncoprotein that promotes survival of cancer cells through anti-apoptosis. However, DJ-1 also plays a role in regulating IL-1β expression, and whether inflammatory microenvironment built by dysregulated DJ-1 affects cancer progression is still unclear. This study thus aimed to compare the metastatic abilities of melanoma cells in wild-type (WT) and DJ-1 knockout (KO) mice, and to check whether inflammatory microenvironment built in DJ-1 KO mice plays a role in migration of cancer cells to lungs. First, B16F10 melanoma cells (at 6×10⁴) were injected into the femoral vein of mice, and formation of lung nodules, levels of lung IL-1β and serum cytokines, and accumulation of myeloid-derived suppressor cells (MDSCs) were compared between WT and DJ-1 KO mice. Second, the cancer-bearing mice were treated with an interleukin-1 beta (IL-1β) neutralizing antibody to see whether IL-1β is involved in the cancer migration. Finally, cultured RAW 264.7 macrophage and B16F10 melanoma cells were respectively treated with DJ-1 shRNA and recombinant IL-1β to explore underlying molecular mechanisms. Our results showed that IL-1β enhanced survival and colony formation of cultured melanoma cells, and that IL-1β levels were elevated both in DJ-1 KO mice and in cultured macrophage cells with DJ-1 knockdown. The elevated IL-1β correlated with higher accumulation of immunosuppressive MDSCs and formation of melanoma module in the lung of DJ-1 KO mice, and both can be decreased by treating mice with IL-1β neutralizing antibodies. Taken together, these results indicate that immunosuppressive tissue microenvironment built in DJ-1 KO mice can enhance lung migration of cancer, and IL-1β plays an important role in promoting the cancer migration.

Journal of Cancer Metastasis and Treatment is an open access journal, focusing on basic and clinical studies related to cancer cell, cell biology, oncology, radiation therapy and radiology, obstetrics and gynecology, pediatrics, surgery, hematology, neuro-oncology, etc.

The phosphoinositide-3-kinase (PI3K) pathway has widely been considered as a potential therapeutic target for head and neck cancer (HNC); however, the application of PI3K inhibitors is often overshadowed by the induction of drug resistance with unknown mechanisms. In this study, PII3K inhibitor resistant cancer cells were developed by prolonged culturing of cell lines with BEZ235, a dual PI3K and mammalian target of rapamycin (mTOR) inhibitor. The drug resistant HNC cells showed higher IC₅₀ of the proliferation to inhibitors specifically targeting PI3K and/or mTOR, as compared to their parental cells. These cells also showed profound resistance to drugs of other classes. Molecular analysis revealed persistent activation of phosphorylated AKT at threonine 308 in the drug resistant cells and increased expression of markers for tumor-initiating cells. Interestingly, increased intra-cellular ROS levels were observed in the drug resistant cells. Among anti-oxidant molecules, the expression of SOD2 was increased and was associated with the ALDH-positive tumor-initiating cell features. Co-incubation of SOD inhibitors and BEZ235 decreased the stemness feature of the cells in vitro, as shown by results of the spheroid formation assay. In conclusion, dysregulation of SOD2 might contribute to the profound resistance to PI3K inhibitors and the other drugs in HNC cells.

Background/Aim: Glioblastoma (GBM) is a highly aggressive brain tumor associated with poor prognosis and frequent resistance to standard treatments, including temozolomide (TMZ) and radiotherapy. Our previous study identified superoxide dismutase 2 (SOD2) as a key contributor to TMZ resistance through enhanced antioxidant defenses. This study aimed to determine whether SOD2 also plays a role in reduced radiation sensitivity in TMZ-resistant GBM cells. Materials and Methods: Clonogenic assays were used to assess the radiation response of TMZ-resistant U87MG and A172 cells. A pharmacological SOD inhibitor (SODi), sodium diethyldithiocarbamate trihydrate, was applied to evaluate its effect on radiosensitivity. An in vivo subcutaneous xenograft model derived from resistant U87MG cells was used to examine the efficacy of combination therapy with TMZ, irradiation, and SODi. Tumor progression was monitored using a bioluminescence imaging system. Results: TMZ-resistant GBM cells demonstrated enhanced survival after 4 Gy radiation exposure, indicating a cross-resistance phenotype. SODi treatment significantly reduced colony formation in vitro and restored sensitivity to irradiation. In vivo, the triple combination of TMZ, irradiation, and SODi markedly suppressed tumor growth compared to other treatment groups. Conclusion: SOD2 contributes to both TMZ and radiation resistance in GBM. Targeting resistance-associated pathways may offer a promising strategy to improve the efficacy of radiochemotherapy in treatment-refractory glioblastoma.

Objectives: Glioblastoma (GBM) is a prevalent malignant brain tumor prone to drug resistance. We previously found a strong correlation between SH3 domain GRB2-like endophilin B1 (SH3GLB1) and superoxide dismutase 2 (SOD2), which converts O2 to hydrogen peroxide (H2O2). Prior studies show that H2O2 redox signaling is vital for physiological processes and can drive tumor progression. Therefore, we aim to define how H2O2 signaling regulates SH3GLB1 and AKT (protein kinase B) pathways in GBM and to assess whether modulating H2O2 reverses temozolomide (TMZ) resistance. Methods: We used cultured cells and pharmacological inhibitors and activators to confirm the significance of H2O2 signaling. GBM cells were used to verify the role of H2O2 signaling in cell state transitions and animal experiments identified optimal treatment strategies. Results: We found that SOD2 acts as an upstream regulator of SH3GLB1. When SOD inhibitors and TMZ were combined, cells showed reduced SH3GLB1 and autophagy levels. SH3GLB1 was found to be regulated by H2O2 via AKT signaling using redox homeostasis-regulating experiments. Although treatment-induced changes in mitochondrial H2O2 levels mirrored those in the cytosol, parental and resistant cells exhibited divergent fates, highlighting cell-fate plasticity. TMZ combined with a redox modulator reduced resistant tumor cell growth (about 2/3 reduction of tumor size; p < 0.05) and suppressed SH3GLB1 and autophagy levels in animal models. The TMZ-induced increase in SH3GLB1 expression was reversed by HgCl2, which inhibited the aquaporin-9/AKT signaling. Conclusion: Overall, these findings underscore the importance of H2O2-SH3GLB1 signaling in GBM and may inform future therapeutic strategies for overcoming TMZ resistance.