mTOR target NDRG1 confers MGMT-dependent resistance to alkylating chemotherapy

Elevated expression of N-myc downstream regulated gene 1 protein in glioblastomas reflects tumor angiogenesis and poor patient prognosis

N-myc downstream regulated gene 1 (NDRG1) is a member of the NDRG family, of which four members (NDRG1, NDRG2, NDRG3, and NDRG4) have been identified. NDRG1 is repressed by c-MYC and N-MYC proto-oncogenes. NDRG1 is translated into a 43 kDa protein that is associated with the regulation of cellular stress responses, proliferation, and differentiation. In this study, we aimed to clarify the relationship between progression of glioblastoma (GB) IDH-wildtype and NDRG1 expression in tumor cells. We assessed the expression of NDRG1 in 41 GBs using immunostaining and evaluated its prognostic significance. NDRG1 expression by GBs was evaluated using Histoscore, which showed high and low scores in 23 and 18 cases, respectively. NDRG1-positive cells were strongly expressed in Ki-67 labeled proliferating tumor cells and CD105 positive proliferating microvessels around the area of palisading necrosis. Statistical analyses showed lower survival rates in the high-score group than the low-score group (P < 0.01). This study indicated that overexpression of NDRG1 by GB reflects tumor angiogenesis and poor patient prognosis.

Disrupting glioblastoma networks with tumor treating fields (TTFields) in in vitro models

PURPOSE

This study investigates the biological effect of Tumor Treating Fields (TTFields) on key drivers of glioblastoma's malignancy-tumor microtube (TM) formation-and on the function and overall integrity of the tumor cell network.

METHOD

Using a two-dimensional monoculture GB cell network model (2DTM) of primary glioblastoma cell (GBC) cultures (S24, BG5 or T269), we evaluated the effects of TTFields on cell density, interconnectivity and structural integrity of the tumor network. We also analyzed calcium (Ca2+) transient dynamics and network morphology, validating findings in patient-derived tumoroids and brain tumor organoids.

RESULTS

In the 2DTM assay, TTFields reduced cell density by 85-88% and disrupted network interconnectivity, particularly in cells with multiple TMs. A "crooked TM" phenotype emerged in 5-6% of treated cells, rarely seen in controls. Ca2+ transients were significantly compromised, with global Ca2+ activity reduced by 51-83%, active and periodic cells by over 50%, and intercellular co-activity by 52% in S24, and almost completely in BG5 GBCs. The effects were more pronounced at 200 kHz compared to a 50 kHz TTFields. Similar reductions in Ca2+ activity were observed in patient-derived tumoroids. In brain tumor organoids, TTFields significantly reduced tumor cell proliferation and infiltration.

CONCLUSION

Our comprehensive study provides new insights into the multiple effects of Inovitro-modeled TTFields on glioma progression, morphology and network dynamics in vitro. Future in vivo studies to verify our in vitro findings may provide the basis for a deeper understanding and optimization of TTFields as a therapeutic modality in the treatment of GB.

Matrix stiffness influences response to chemo and targeted therapy in brain metastatic breast cancer cells

Breast cancer is the most common malignancy accounting for 12.5% of all newly diagnosed cancer cases across the globe. Breast cancer cells are known to metastasize to distant organs (i.e., brain), wherein they can exhibit a dormant phenotype for extended time periods. These dormant cancer cells exhibit reduced proliferation and therapeutic resistance. However, the mechanisms by which dormant cancer cells exhibit resistance to therapy, in the context of brain metastatic breast cancer (BMBC), is not well understood. Herein, we utilized hyaluronic acid (HA) hydrogels with varying stiffnesses to study drug responsiveness in dormant vs. proliferative BMBC cells. It was found that cells cultured on soft HA hydrogels (∼0.4 kPa) that showed a non-proliferative (dormant) phenotype exhibited resistance to Paclitaxel or Lapatinib. In contrast, cells cultured on stiff HA hydrogels (∼4.5 kPa) that showed a proliferative phenotype exhibited responsiveness to Paclitaxel or Lapatinib. Moreover, dormancy-associated resistance was found to be due to upregulation of the serum/glucocorticoid regulated kinase 1 (SGK1) gene which was mediated, in part, by the p38 signaling pathway. Accordingly, SGK1 inhibition resulted in a dormant-to-proliferative switch and response to therapy. Overall, our study demonstrates that matrix stiffness influences dormancy-associated therapy response mediated, in part, via the p38/SGK1 axis.

MEN1 Deficiency-Driven Activation of the β-Catenin-MGMT Axis Promotes Pancreatic Neuroendocrine Tumor Growth and Confers Temozolomide Resistance

O6-methylguanine DNA methyltransferase (MGMT) removes alkyl adducts from the guanine O6 position (O6-MG) and repairs DNA damage. High MGMT expression results in poor response to temozolomide (TMZ). However, the biological importance of MGMT and the mechanism underlying its high expression in pancreatic neuroendocrine tumors (PanNETs) remain elusive. Here, it is found that MGMT expression is highly elevated in PanNET tissues compared with paired normal tissues and negatively associated with progression-free survival (PFS) time in patients with PanNETs. Knocking out MGMT inhibits cancer cell growth in vitro and in vivo. Ectopic MEN1 expression suppresses MGMT transcription in a manner that depends on β-Catenin nuclear export and degradation. The Leucine 267 residue of MEN1 is crucial for regulating β-Catenin-MGMT axis activation and chemosensitivity to TMZ. Interference with β-Catenin re-sensitizes tumor cells to TMZ and significantly reduces the cytotoxic effects of high-dose TMZ treatment, and MGMT overexpression counteracts the effects of β-Catenin deficiency. This study reveals the biological importance of MGMT and a new mechanism by which MEN1 deficiency regulates its expression, thus providing a potential combinational strategy for treating patients with TMZ-resistant PanNETs.

Increased oxygen stimulation promotes chemoresistance and phenotype shifting through PLCB1 in gliomas

Gliomas, the most common CNS (central nerve system) tumors, face poor survival due to severe chemoresistance exacerbated by hypoxia. However, studies on whether altered hypoxic conditions benefit for chemo-sensitivity and how gliomas react to increased oxygen stimulation are limited. In this study, we demonstrated that increased oxygen stimulation promotes glioma growth and chemoresistance. Mechanically, increased oxygen stimulation upregulates miR-1290 levels. miR-1290, in turn, downregulates PLCB1, while PLCB1 facilitates the proteasomal degradation of β-catenin and active-β-catenin by increasing the proportion of ubiquitinated β-catenin in a destruction complex-independent mechanism. This process inhibits PLCB1 expression, leads to the accumulation of active-β-catenin, boosting Wnt signaling through an independent mechanism and ultimately promoting chemoresistance in glioma cells. Pharmacological inhibition of Wnt by WNT974 could partially inhibit glioma volume growth and prolong the shortened survival caused by increased oxygen stimulation in a glioma-bearing mouse model. Moreover, PLCB1, a key molecule regulated by increased oxygen stimulation, shows promising predictive power in survival analysis and has great potential to be a biomarker for grading and prognosis in glioma patients. These results provide preliminary insights into clinical scenarios associated with altered hypoxic conditions in gliomas, and introduce a novel perspective on the role of the hypoxic microenvironment in glioma progression. Furthermore, the outcomes reveal the potential risks of utilizing hyperbaric oxygen treatment (HBOT) in glioma patients, particularly when considering HBOT as a standalone option to ameliorate neuro-dysfunctions or when combining HBOT with a single chemotherapy agent without radiotherapy.

NSUN6-mediated 5-methylcytosine modification of NDRG1 mRNA promotes radioresistance in cervical cancer

BACKGROUND

Radioresistance is the leading cause of death in advanced cervical cancer (CC). Dysregulation of RNA modification has recently emerged as a regulatory mechanism in radiation and drug resistance. We aimed to explore the biological function and clinical significance of 5-methylcytosine (m5C) in cervical cancer radiosensitivity.

METHODS

The abundance of RNA modification in radiotherapy-resistant and sensitive CC specimens was quantified by liquid chromatography-tandem mass spectrometry. The essential RNA modification-related genes involved in CC radiosensitivity were screened via RNA sequencing. The effect of NSUN6 on radiosensitivity was verified in CC cell lines, cell-derived xenograft (CDX), and 3D bioprinted patient-derived organoid (PDO). The mechanisms of NSUN6 in regulating CC radiosensitivity were investigated by integrative m5C sequencing, mRNA sequencing, and RNA immunoprecipitation.

RESULTS

We found a higher abundance of m5C modification in resistant CC samples, and NSUN6 was the essential m5C-regulating gene concerning radiosensitivity. NSUN6 overexpression was clinically correlated with radioresistance and poor prognosis in cervical cancer. Functionally, higher NSUN6 expression was associated with radioresistance in the 3D PDO model of cervical cancer. Moreover, silencing NSUN6 increased CC radiosensitivity in vivo and in vitro. Mechanistically, NDRG1 was one of the downstream target genes of NSUN6 identified by integrated m5C-seq, mRNA-seq, and functional validation. NSUN6 promoted the m5C modification of NDRG1 mRNA, and the m5C reader ALYREF bound explicitly to the m5C-labeled NDRG1 mRNA and enhanced NDRG1 mRNA stability. NDRG1 overexpression promoted homologous recombination-mediated DNA repair, which in turn led to radioresistance in cervical cancer.

CONCLUSIONS

Aberrant m5C hypermethylation and NSUN6 overexpression drive resistance to radiotherapy in cervical cancer. Elevated NSUN6 expression promotes radioresistance in cervical cancer by activating the NSUN6/ALYREF-m5C-NDRG1 pathway. The low expression of NSUN6 in cervical cancer indicates sensitivity to radiotherapy and a better prognosis.

Multi-modal mechanisms of the metastasis suppressor, NDRG1: Inhibition of WNT/β-catenin signaling by stabilization of protein kinase Cα

The metastasis suppressor, N-myc downstream regulated gene-1 (NDRG1), inhibits pro-oncogenic signaling in pancreatic cancer (PC). This investigation dissected a novel mechanism induced by NDRG1 on WNT/β-catenin signaling in multiple PC cell types. NDRG1 overexpression decreased β-catenin and downregulated glycogen synthase kinase-3β (GSK-3β) protein levels and its activation. However, β-catenin phosphorylation at Ser33, Ser37, and Thr41 are classically induced by GSK-3β was significantly increased after NDRG1 overexpression, suggesting a GSK-3β-independent mechanism. Intriguingly, NDRG1 overexpression upregulated protein kinase Cα (PKCα), with PKCα silencing preventing β-catenin phosphorylation at Ser33, Ser37, and Thr41, and decreasing β-catenin expression. Further, NDRG1 and PKCα were demonstrated to associate, with PKCα stabilization occurring after NDRG1 overexpression. PKCα half-life increased from 1.5 ± 0.8 h (3) in control cells to 11.0 ± 2.5 h (3) after NDRG1 overexpression. Thus, NDRG1 overexpression leads to the association of NDRG1 with PKCα and PKCα stabilization, resulting in β-catenin phosphorylation at Ser33, Ser37, and Thr41. The association between PKCα, NDRG1, and β-catenin was identified, with the formation of a potential metabolon that promotes the latter β-catenin phosphorylation. This anti-oncogenic activity of NDRG1 was multi-modal, with the above mechanism accompanied by the downregulation of the nucleo-cytoplasmic shuttling protein, p21-activated kinase 4 (PAK4), which is involved in β-catenin nuclear translocation, inhibition of AKT phosphorylation (Ser473), and decreased β-catenin phosphorylation at Ser552 that suppresses its transcriptional activity. These mechanisms of NDRG1 activity are important to dissect to understand the marked anti-cancer efficacy of NDRG1-inducing thiosemicarbazones that upregulate PKCα and inhibit WNT signaling.

MAPK14 /p38α Shapes the Molecular Landscape of Endometrial Cancer and promotes Tumorigenic Characteristics

The molecular underpinnings of H igh G rade E ndometrial C arcinoma (HGEC) metastatic growth and survival are poorly understood. Here we show that ascites-derived and primary tumor HGEC cell lines in 3D spheroid culture faithfully recapitulate key features of malignant peritoneal effusion and exhibit fundamentally distinct transcriptomic, proteomic and metabolomic landscapes when compared with conventional 2D monolayers. Using genetic screening platform we identify MAPK14 (which encodes the protein kinase p38α) as a specific requirement for HGEC in spheroid culture. MAPK14 /p38α has broad roles in programing the phosphoproteome, transcriptome and metabolome of HGEC spheroids, yet has negligible impact on monolayer cultures. MAPK14 promotes tumorigenicity in vivo and is specifically required to sustain a sub-population of spheroid cells that is enriched in cancer stemness markers. Therefore, spheroid growth of HGEC activates unique biological programs, including p38α signaling, that cannot be captured using 2D culture models and are highly relevant to malignant disease pathology.

'The Reports of My Death Are Greatly Exaggerated'-Evaluating the Effect of Necrosis on MGMT Promoter Methylation Testing in High-Grade Glioma

(1) Background: MGMT (O-6-methylguanine-DNA methyltransferase) promoter methylation remains an important predictive biomarker in high-grade gliomas (HGGs). The influence of necrosis on the fidelity of MGMT promoter (MGMTp) hypermethylation testing is currently unknown. Therefore, our study aims to evaluate the effect of varying degrees of necrosis on MGMTp status, as determined by pyrosequencing, in a series of primary and recurrent HGGs; (2) Methods: Within each case, the most viable blocks (assigned as 'true' MGMTp status) and the most necrotic block were determined by histopathology review. MGMTp status was determined by pyrosequencing. Comparisons of MGMTp status were made between the most viable and most necrotic blocks. (3) Results: 163 samples from 64 patients with HGGs were analyzed. MGMTp status was maintained in 84.6% of primary and 78.3% of recurrent HGGs between the most viable and necrotic blocks. A threshold of ≥60% tumor cellularity was established at which MGMTp status was unaltered, irrespective of the degree of necrosis. (4) Conclusions: MGMTp methylation status, as determined by pyrosequencing, does not appear to be influenced by necrosis in the majority of cases at a cellularity of at least 60%. Further investigation into the role of intratumoral heterogeneity on MGMTp status will increase our understanding of this predictive marker.

MGMT in TMZ-based glioma therapy: Multifaceted insights and clinical trial perspectives

Temozolomide (TMZ) is the most preferred and approved chemotherapeutic drug for either first- or second-line chemotherapy for glioma patients across the globe. In glioma patients, resistance to treatment with alkylating drugs like TMZ is known to be conferred by exalted levels of MGMT gene expression. On the contrary, epigenetic silencing through MGMT gene promoter methylation leading to subsequent reduction in MGMT transcription and protein expression, is predicted to have a response favoring TMZ treatment. Thus, MGMT protein level in cancer cells is a crucial determining factor in indicating and predicting the choice of alkylating agents in chemotherapy or choosing glioma patients directly for a second line of treatment. Thus, in-depth research is necessary to achieve insights into MGMT gene regulation that has recently enticed a fascinating interest in epigenetic, transcriptional, post-transcriptional, and post-translational levels. Furthermore, MGMT promoter methylation, stability of MGMT protein, and related subsequent adaptive responses are also important contributors to strategic developments in glioma therapy. With applications to its identification as a prognostic biomarker, thus predicting response to advanced glioma therapy, this review aims to concentrate on the mechanistic role and regulation of MGMT gene expression at epigenetic, transcriptional, post-transcriptional, and post-translational levels functioning under the control of multiple signaling dynamics.

O6-methylguanine DNA methyltransferase regulates β-glucan-induced trained immunity of macrophages via farnesoid X receptor and AMPK

Trained immunity is the heightened state of innate immune memory that enhances immune response resulting in nonspecific protection. Epigenetic changes and metabolic reprogramming are critical steps that regulate trained immunity. In this study, we reported the involvement of O6-methylguanine DNA methyltransferase (MGMT), a DNA repair enzyme of lesion induced by alkylating agents, in regulation the trained immunity induced by β-glucan (BG). Pharmacological inhibition or silencing of MGMT expression altered LPS stimulated pro-inflammatory cytokine productions in BG-trained bone marrow derived macrophages (BMMs). Targeted deletion of Mgmt in BMMs resulted in reduction of the trained responses both in vitro and in vivo models. The transcriptomic analysis revealed that the dampening trained immunity in MGMT KO BMMs is partially mediated by ATM/FXR/AMPK axis affecting the MAPK/mTOR/HIF1α pathways and the reduction in glycolysis function. Taken together, a failure to resolve a DNA damage may have consequences for innate immune memory.

Characterization of prevalent tyrosine kinase inhibitors and their challenges in glioblastoma treatment

Glioblastoma multiforme (GBM) is a highly aggressive malignant primary tumor in the central nervous system. Despite extensive efforts in radiotherapy, chemotherapy, and neurosurgery, there remains an inadequate level of improvement in treatment outcomes. The development of large-scale genomic and proteomic analysis suggests that GBMs are characterized by transcriptional heterogeneity, which is responsible for therapy resistance. Hence, knowledge about the genetic and epigenetic heterogeneity of GBM is crucial for developing effective treatments for this aggressive form of brain cancer. Tyrosine kinases (TKs) can act as signal transducers, regulate important cellular processes like differentiation, proliferation, apoptosis and metabolism. Therefore, TK inhibitors (TKIs) have been developed to specifically target these kinases. TKIs are categorized into allosteric and non-allosteric inhibitors. Irreversible inhibitors form covalent bonds, which can lead to longer-lasting effects. However, this can also increase the risk of off-target effects and toxicity. The development of TKIs as therapeutics through computer-aided drug design (CADD) and bioinformatic techniques enhance the potential to improve patients' survival rates. Therefore, the continued exploration of TKIs as drug targets is expected to lead to even more effective and specific therapeutics in the future.

Germ line variant GFI1-36N affects DNA repair and sensitizes AML cells to DNA damage and repair therapy

ABSTRACT

Growth factor independence 1 (GFI1) is a DNA-binding transcription factor and a key regulator of hematopoiesis. GFI1-36N is a germ line variant, causing a change of serine (S) to asparagine (N) at position 36. We previously reported that the GFI1-36N allele has a prevalence of 10% to 15% among patients with acute myeloid leukemia (AML) and 5% to 7% among healthy Caucasians and promotes the development of this disease. Using a multiomics approach, we show here that GFI1-36N expression is associated with increased frequencies of chromosomal aberrations, mutational burden, and mutational signatures in both murine and human AML and impedes homologous recombination (HR)-directed DNA repair in leukemic cells. GFI1-36N exhibits impaired binding to N-Myc downstream-regulated gene 1 (Ndrg1) regulatory elements, causing decreased NDRG1 levels, which leads to a reduction of O6-methylguanine-DNA-methyltransferase (MGMT) expression levels, as illustrated by both transcriptome and proteome analyses. Targeting MGMT via temozolomide, a DNA alkylating drug, and HR via olaparib, a poly-ADP ribose polymerase 1 inhibitor, caused synthetic lethality in human and murine AML samples expressing GFI1-36N, whereas the effects were insignificant in nonmalignant GFI1-36S or GFI1-36N cells. In addition, mice that received transplantation with GFI1-36N leukemic cells treated with a combination of temozolomide and olaparib had significantly longer AML-free survival than mice that received transplantation with GFI1-36S leukemic cells. This suggests that reduced MGMT expression leaves GFI1-36N leukemic cells particularly vulnerable to DNA damage initiating chemotherapeutics. Our data provide critical insights into novel options to treat patients with AML carrying the GFI1-36N variant.

MAOA suppresses the growth of gastric cancer by interacting with NDRG1 and regulating the Warburg effect through the PI3K/AKT/mTOR pathway

OBJECTIVE

Previous studies have indicated that neurotransmitters play important roles in the occurrence and development of gastric cancer. MAOA is an important catecholamine neurotransmitter-degrading enzyme involved in the degradation of norepinephrine, epinephrine and serotonin. To find a potential therapeutic target for the treatment of gastric cancer, the biological functions of MAOA and the underlying mechanism in gastric cancer need to be explored.

METHODS

The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO) datasets, Kaplan‒Meier (KM) plotter were used to identify the differentially expressed genes, which mainly involved the degradation and synthesis enzymes of neurotransmitters in gastric cancer. We also investigated the expression pattern of MAOA in human and mouse tissues and cell lines by immunohistochemistry and Western blotting analysis. Western blotting, quantitative real-time PCR, enzyme-linked immunosorbent assay (ELISA) and a Seahorse experiment were used to identify the molecular mechanism of cancer cell glycolysis. MAOA expression and patient survival were analysed in the Ren Ji cohort, and univariate and multivariate analyses were performed based on the clinicopathological characteristics of the above samples.

RESULTS

MAOA expression was significantly downregulated in gastric cancer tissue and associated with poor patient prognosis. Moreover, the expression level of MAOA in gastric cancer tissue had a close negative correlation with the SUXmax value of PET-CT in patients. MAOA suppressed tumour growth and glycolysis and promoted cancer cell apoptosis. We also reported that MAOA can interact with NDRG1 and regulate glycolysis through suppression of the PI3K/Akt/mTOR pathway. MAOA expression may serve as an independent prognostic factor in gastric cancer patients.

CONCLUSIONS

MAOA attenuated glycolysis and inhibited the progression of gastric cancer through the PI3K/Akt/mTOR pathway. Loss of function or downregulation of MAOA can facilitate gastric cancer progression. Overexpression of MAOA and inhibition of the PI3K/Akt/mTOR pathway may provide a potential method for gastric cancer treatment in clinical therapeutic regimens.

Modulating MGMT expression through interfering with cell signaling pathways

Guanine O6-alkylating agents are widely used as first-line chemotherapeutic drugs due to their ability to induce cytotoxic DNA damage. However, a major hurdle in their effectiveness is the emergence of chemoresistance, largely attributed to the DNA repair pathway mediated by O6-methylguanine-DNA methyltransferase (MGMT). MGMT plays an important role in removing the alkyl groups from lethal O6-alkylguanine (O6-AlkylG) adducts formed by chemotherapeutic alkylating agents. By doing so, MGMT enables tumor cells to evade apoptosis and develop drug resistance toward DNA alkylating agents. Although covalent inhibitors of MGMT, such as O6-benzylguanine (O6-BG) and O6-(4-bromothenyl)guanine (O6-4-BTG or lomeguatrib), have been explored in clinical settings, their utility is limited due to severe delayed hematological toxicity observed in most patients when combined with alkylating agents. Therefore, there is an urgent need to identify new targets and unravel the underlying molecular mechanisms and to develop alternative therapeutic strategies that can overcome MGMT-mediated tumor resistance. In this context, the regulation of MGMT expression via interfering the specific cell signaling pathways (e.g., Wnt/β-catenin, NF-κB, Hedgehog, PI3K/AKT/mTOR, JAK/STAT) emerges as a promising strategy for overcoming tumor resistance, and ultimately enhancing the efficacy of DNA alkylating agents in chemotherapy.

mTOR Signaling Pathway and Gut Microbiota in Various Disorders: Mechanisms and Potential Drugs in Pharmacotherapy

The mammalian or mechanistic target of rapamycin (mTOR) integrates multiple intracellular and extracellular upstream signals involved in the regulation of anabolic and catabolic processes in cells and plays a key regulatory role in cell growth and metabolism. The activation of the mTOR signaling pathway has been reported to be associated with a wide range of human diseases. A growing number of in vivo and in vitro studies have demonstrated that gut microbes and their complex metabolites can regulate host metabolic and immune responses through the mTOR pathway and result in disorders of host physiological functions. In this review, we summarize the regulatory mechanisms of gut microbes and mTOR in different diseases and discuss the crosstalk between gut microbes and their metabolites and mTOR in disorders in the gastrointestinal tract, liver, heart, and other organs. We also discuss the promising application of multiple potential drugs that can adjust the gut microbiota and mTOR signaling pathways. Despite the limited findings between gut microbes and mTOR, elucidating their relationship may provide new clues for the prevention and treatment of various diseases.

mTOR Regulation of N-Myc Downstream Regulated 1 (NDRG1) Phosphorylation in Clear Cell Renal Cell Carcinoma

The mechanistic target of rapamycin (mTOR) kinase is a component of two signaling complexes that are known as mTOR complex 1 (mTORC1) and mTORC2. We sought to identify mTOR-phosphorylated proteins that are differently expressed in clinically resected clear cell renal cell carcinoma (ccRCC) relative to pair-matched normal renal tissue. Using a proteomic array, we found N-Myc Downstream Regulated 1 (NDRG1) showed the greatest increase (3.3-fold) in phosphorylation (on Thr346) in ccRCC. This was associated with an increase in total NDRG1. RICTOR is a required subunit in mTORC2, and its knockdown decreased total and phospho-NDRG1 (Thr346) but not NDRG1 mRNA. The dual mTORC1/2 inhibitor, Torin 2, significantly reduced (by ~100%) phospho-NDRG1 (Thr346). Rapamycin is a selective mTORC1 inhibitor that had no effect on the levels of total NDRG1 or phospho-NDRG1 (Thr346). The reduction in phospho-NDRG1 (Thr346) due to the inhibition of mTORC2 corresponded with a decrease in the percentage of live cells, which was correlated with an increase in apoptosis. Rapamycin had no effect on ccRCC cell viability. Collectively, these data show that mTORC2 mediates the phosphorylation of NDRG1 (Thr346) in ccRCC. We hypothesize that RICTOR and mTORC2-mediated phosphorylation of NDRG1 (Thr346) promotes the viability of ccRCC cells.

TGFβ Governs the Pleiotropic Activity of NDRG1 in Triple-Negative Breast Cancer Progression

In triple-negative breast cancer (TNBC), the pleiotropic NDRG1 (N-Myc downstream regulated gene 1) promotes progression and worse survival, yet contradictory results were documented, and the mechanisms remain unknown. Phosphorylation and localization could drive NDRG1 pleiotropy, nonetheless, their role in TNBC progression and clinical outcome was not investigated. We found enhanced p-NDRG1 (Thr346) by TGFβ1 and explored whether it drives NDRG1 pleiotropy and TNBC progression. In tissue microarrays of 81 TNBC patients, we identified that staining and localization of NDRG1 and p-NDRG1 (Thr346) are biomarkers and risk factors associated with shorter overall survival. We found that TGFβ1 leads NDRG1, downstream of GSK3β, and upstream of NF-κB, to differentially regulate migration, invasion, epithelial-mesenchymal transition, tumor initiation, and maintenance of different populations of cancer stem cells (CSCs), depending on the progression stage of tumor cells, and the combination of TGFβ and GSK3β inhibitors impaired CSCs. The present study revealed the striking importance to assess both total NDRG1 and p-NDRG1 (Thr346) positiveness and subcellular localization to evaluate patient prognosis and their stratification. NDRG1 pleiotropy is driven by TGFβ to differentially promote metastasis and/or maintenance of CSCs at different stages of tumor progression, which could be abrogated by the inhibition of TGFβ and GSK3β.

Novel iron chelator SK4 demonstrates cytotoxicity in a range of tumour derived cell lines

Iron is an essential micronutrient due to its involvement in many cellular processes including DNA replication and OXPHOS. Tumors overexpress iron metabolism linked proteins which allow for iron accumulation driving high levels of proliferation. Our group has designed novel iron chelator SK4 which targets cancer’s “iron addiction.” SK4 comprises of two key moieties: an iron chelation moiety responsible for cytotoxicity and an amino acid moiety which allows entry through amino acid transporter LAT1. We selected LAT1 as a route of entry as it is commonly overexpressed in malignant tumors. SK4 has previously demonstrated promising results in an in vitro model for melanoma. We hypothesized SK4 would be effective against a range of tumor types. We have screened a panel of tumor-derived cell lines from different origins including breast, prostate, ovarian and cervical cancer for SK4 sensitivity and we have found a range of differential sensitivities varying from 111.3 to >500 μM. We validated the iron chelation moiety as responsible for inducing cytotoxicity through control compounds; each lacking a key moiety. Following the screen, we conducted a series of assays to elucidate the mechanism of action behind SK4 cytotoxicity. SK4 was shown to induce apoptosis in triple negative breast cancer cell line MDA MB 231 but not ovarian cancer cell line SKOV3 suggesting SK4 may induce different modes of cell death in each cell line. As MDA MB 231 cells harbor a mutation in p53, we conclude SK4 is capable of inducing apoptosis in a p53-independent manner. SK4 upregulated NDRG1 expression in MDA MB 231 and SKOV3 cells. Interestingly, knockdown of NDRG1 antagonized SK4 in MDA MB 231 cells but not SKOV3 cells suggesting SK4’s mechanism of action may be mediated through NDRG1 in MDA MB 231 cells. In conclusion, we have shown tagging iron chelators with an amino acid moiety to allow entry through the LAT1 transporter represents a double pronged approach to cancer therapy, targeting “iron addiction” and amino acid metabolism dysregulation.

Targeting the Axl and mTOR Pathway Synergizes Immunotherapy and Chemotherapy to Butylidenephthalide in a Recurrent GBM

Background. The role of inherent tumor heterogeneity and an immunosuppressive microenvironment in therapeutic resistance has been determined to be of importance for the better management of glioblastoma multiforme (GBM). Some studies have suggested that combined drugs with divergent mechanisms may be promising in treating recurrent GBM. Methods. Intracranial sustained (Z)-n-butylidenephthalide [(Z)-BP] delivery through Cerebraca Wafers (CWs) to eliminate unresectable brain tumors was combined with the administration of temozolomide (TMZ), pembrolizumab, and cytokine-induced killer (CIK) cells for treating a patient with recurrent glioblastoma. Neurological adverse events and wound healing delay were monitored for estimating tolerance and efficacy. Response Assessment in Neuro-Oncology criteria were applied to evaluate progression-free survival (PFS); further, the molecular characteristics of GBM tissues were analyzed, and the underlying mechanism was investigated using primary culture. Results. Intracerebral (Z)-BP in residual tumors could not only inhibit cancer stem cells but also increase interferon gamma levels in serum, which then led to the regression of GBM and an immune-responsive microenvironment. Targeting receptor tyrosine kinases, including Axl and epidermal growth factor receptor (EGFR), and inhibiting the mechanistic target of rapamycin (mTOR) through (Z)-BP were determined to synergize CIK cells in the presence of pembrolizumab and TMZ in recurrent GBM. Therefore, this well-tolerated regimen could simultaneously block multiple cancer pathways, which allowed extended PFS and improved quality of life for 22 months. Conclusion. Given the several unique functions of (Z)-BP, greater sensitivity of chemotherapy and the synergism of pembrolizumab and CIK cells could have affected the excellent prognosis seen in this patient with recurrent GBM.

Increased mTORC2 pathway activation in lymph nodes of iMCD-TAFRO

Idiopathic multicentric Castleman disease (iMCD) is a rare and life‐threatening haematologic disorder involving polyclonal lymphoproliferation and organ dysfunction due to excessive cytokine production, including interleukin‐6 (IL‐6). Clinical trial and real‐world data demonstrate that IL‐6 inhibition is effective in 34–50% of patients. mTOR, which functions through mTORC1 and mTORC2, is a recently discovered therapeutic target. The mTOR inhibitor sirolimus, which preferentially inhibits mTORC1, has led to sustained remission in a small cohort of anti‐IL‐6‐refractory iMCD patients with thrombocytopenia, anasarca, fever, renal dysfunction and organomegaly (iMCD‐TAFRO). However, sirolimus has not shown uniform effect, potentially due to its limited mTORC2 inhibition. To investigate mTORC2 activation in iMCD, we quantified the mTORC2 effector protein pNDRG1 by immunohistochemistry of lymph node tissue from six iMCD‐TAFRO and eight iMCD patients who do not meet TAFRO criteria (iMCD‐not‐otherwise‐specified; iMCD‐NOS). mTORC2 activation was increased in all regions of iMCD‐TAFRO lymph nodes and the interfollicular space of iMCD‐NOS compared with control tissue. Immunohistochemistry also revealed increased pNDRG1 expression in iMCD‐TAFRO germinal centres compared with autoimmune lymphoproliferative syndrome (ALPS), an mTOR‐driven, sirolimus‐responsive lymphoproliferative disorder, and comparable staining between iMCD‐NOS and ALPS. These results suggest increased mTORC2 activity in iMCD and that dual mTORC1/mTORC2 inhibitors may be a rational therapeutic approach.

NDRG1 in Aggressive Breast Cancer Progression and Brain Metastasis

BACKGROUND

N-Myc downstream regulated gene 1 (NDRG1) suppresses metastasis in many human malignancies, including breast cancer, yet has been associated with worse survival in patients with inflammatory breast cancer. The role of NDRG1 in the pathobiology of aggressive breast cancers remains elusive.

METHODS

To study the role of NDRG1 in tumor growth and brain metastasis in vivo, we transplanted cells into cleared mammary fat pads or injected them in tail veins of SCID/Beige mice (n = 7-10 per group). NDRG1 protein expression in patient breast tumors (n = 216) was assessed by immunohistochemical staining. Kaplan-Meier method with 2-sided log-rank test was used to analyze the associations between NDRG1 and time-to-event outcomes. A multivariable Cox regression model was used to determine independent prognostic factors. All statistical tests were 2-sided.

RESULTS

We generated new sublines that exhibited a distinct propensity to metastasize to the brain. NDRG1-high-expressing cells produced more prevalent brain metastases (100% vs 44.4% for NDRG1-low sublines, P = .01, Fisher's exact test), greater tumor burden, and reduced survival in mice. In aggressive breast cancer cell lines, silencing NDRG1 led to reduced migration, invasion, and tumor-initiating cell subpopulations. In xenograft models, depleting NDRG1 inhibited primary tumor growth and brain metastasis. In patient breast tumors, NDRG1 was associated with aggressiveness: NDRG1-high expression was also associated with shorter overall survival (hazard ratio [HR] = 2.27, 95% confidence interval [95% CI] = 1.20 to 4.29, P = .009) and breast cancer-specific survival (HR = 2.19, 95% CI = 1.07 to 4.48, P = .03). Multivariable analysis showed NDRG1 to be an independent predictor of overall survival (HR = 2.17, 95% CI = 1.10 to 4.30, P = .03) and breast cancer-specific survival rates (HR = 2.27, 95% CI = 1.05 to 4.92, P = .04).

CONCLUSIONS

We demonstrated that NDRG1 drives tumor progression and brain metastasis in aggressive breast cancers and that NDRG1-high expression correlates with worse clinical outcomes, suggesting that NDRG1 may serve as a therapeutic target and prognostic biomarker in aggressive breast cancers.

A Tumor Suppressor Gene, N-myc Downstream-Regulated Gene 1 (NDRG1), in Gliomas and Glioblastomas

The development of potent and selective therapeutic approaches to glioblastoma (GBM) requires the identification of molecular pathways that critically regulate the survival and proliferation of GBM. Glioblastoma stem-like cells (GSCs) possess stem-cell-like properties, self-renewal, and differentiation into multiple neural cell lineages. From a clinical point of view, GSCs have been reported to resist radiation and chemotherapy. GSCs are influenced by the microenvironment, especially the hypoxic condition. N-myc downstream-regulated gene 1 (NDRG1) is a tumor suppressor with the potential to suppress the proliferation, invasion, and migration of cancer cells. Previous studies have reported that deregulated expression of NDRG1 affects tumor growth and clinical outcomes of patients with GBM. This literature review aimed to clarify the critical role of NDRG1 in tumorigenesis and acquirement of resistance for anti-GBM therapies, further to discussing the possibility and efficacy of NDRG1 as a novel target of treatment for GBM. The present review was conducted by searching the PubMed and Scopus databases. The search was conducted in February 2022. We review current knowledge on the regulation and signaling of NDRG1 in neuro-oncology. Finally, the role of NDRG1 in GBM and potential clinical applications are discussed.

mTOR-Mediated Regulation of Immune Responses in Cancer and Tumor Microenvironment

The mechanistic/mammalian target of rapamycin (mTOR) is a downstream mediator in the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathways, which plays a pivotal role in regulating numerous cellular functions including cell growth, proliferation, survival, and metabolism by integrating a variety of extracellular and intracellular signals in the tumor microenvironment (TME). Dysregulation of the mTOR pathway is frequently reported in many types of human tumors, and targeting the PI3K/Akt/mTOR signaling pathway has been considered an attractive potential therapeutic target in cancer. The PI3K/Akt/mTOR signaling transduction pathway is important not only in the development and progression of cancers but also for its critical regulatory role in the tumor microenvironment. Immunologically, mTOR is emerging as a key regulator of immune responses. The mTOR signaling pathway plays an essential regulatory role in the differentiation and function of both innate and adaptive immune cells. Considering the central role of mTOR in metabolic and translational reprogramming, it can affect tumor-associated immune cells to undergo phenotypic and functional reprogramming in TME. The mTOR-mediated inflammatory response can also promote the recruitment of immune cells to TME, resulting in exerting the anti-tumor functions or promoting cancer cell growth, progression, and metastasis. Thus, deregulated mTOR signaling in cancer can modulate the TME, thereby affecting the tumor immune microenvironment. Here, we review the current knowledge regarding the crucial role of the PI3K/Akt/mTOR pathway in controlling and shaping the immune responses in TME.

Advantages and drawbacks of dexamethasone in glioblastoma multiforme

The most widespread, malignant, and deadliest type of glial tumor is glioblastoma multiforme (GBM). Despite radiation, chemotherapy, and radical surgery, the median survival of afflicted individuals is about 12 months. Unfortunately, existing therapeutic interventions are abysmal. Dexamethasone (Dex), a synthetic glucocorticoid, has been used for many years to treat brain edema and inflammation caused by GBM. Several investigations have recently shown that Dex also exerts antitumoral effects against GBM. On the other hand, more recent disputed findings have questioned the long-held dogma of Dex treatment for GBM. Unfortunately, steroids are associated with various undesirable side effects, including severe immunosuppression and metabolic changes like hyperglycemia, which may impair the survival of GBM patients. Current ideas and concerns about Dex's effects on GBM cerebral edema, cell proliferation, migration, and its clinical outcomes were investigated in this study.

Tumor-Acidity and Bioorthogonal Chemistry-Mediated On-Site Size Transformation Clustered Nanosystem to Overcome Hypoxic Resistance and Enhance Chemoimmunotherapy

Hypoxia, a common feature of most solid tumors, causes severe tumor resistance to chemotherapy and immunotherapy. Herein, a tumor-acidity and bioorthogonal chemistry-mediated on-site size transformation clustered nanosystem is designed to overcome hypoxic resistance and enhance chemoimmunotherapy. The nanosystem utilized the tumor-acidity responsive group poly(2-azepane ethyl methacrylate) with a rapid response rate and highly efficient bioorthogonal click chemistry to form large-sized aggregates in tumor tissue to enhance accumulation and retention. Subsequently, another tumor-acidity responsive group of the maleic acid amide with a slow response rate was cleaved allowing the aggregates to slowly dissociate into ultrasmall nanoparticles with better tumor penetration ability for the delivery of doxorubicin (DOX) and nitric oxide (NO) to a hypoxic tumor tissue. NO can reverse a hypoxia-induced DOX resistance and boost the antitumor immune response through a reprogrammed tumor immune microenvironment. This tumor-acidity and bioorthogonal chemistry-mediated on-site size transformation clustered nanosystem not only helps to counteract a hypoxia-induced chemoresistance and enhance antitumor immune responses but also provides a general drug delivery strategy for enhanced tumor accumulation and penetration.

EBV LMP1-activated mTORC1 and mTORC2 Coordinately Promote Nasopharyngeal Cancer Stem Cell Properties

Epstein-Barr Virus (EBV) is associated with several malignant diseases, including Burkitt's lymphoma, nasopharyngeal carcinoma (NPC), certain types of lymphomas, and a portion of gastric cancers. Virus-encoded oncoprotein LMP1 induces the epithelial-to-mesenchymal transition (EMT), leading to cancer stem cell formation. In the current study, we investigated how LMP1 contributes to cancer stem cell development in NPC. We found that LMP1 plays an essential role in acquiring CSC characteristics, including tumor initiation, metastasis, and therapeutic resistance by activating the PI3K/mTOR/Akt signaling pathway. We dissected the functions of distinct signaling (mTORC1 and mTORC2) in the acquisition of different CSC characteristics. Side population (SP) formation, which represents the chemotherapy resistance feature of CSC, requires mTORC1 signaling. Tumor initiation capability is mainly attributed to mTORC2, which confers on NPC the capabilities of proliferation and survival by activating mTORC2 downstream genes c-Myc. Both mTORC1 and mTORC2 enhance cell migration and invasion of NPC cells, suggesting that mTORC1/2 co-regulate metastasis of NPC. The revelation of the roles of the mTOR signaling pathways in distinct tumorigenic features provides a guideline for designing efficient therapies by choosing specific mTOR inhibitors targeting mTORC1, mTORC2, or both to achieve durable remission of NPC in patients. Importance LMP1 endows NPC to gain cancer stem cell characteristics through activating mTORC1 and mTORC2 pathways. The different mTOR pathways are responsible for distinct tumorigenic features. Rapamycin-insensitive mTORC1 is essential for CSC drug resistance. NPC tumor initiation capacity is mainly attributed to mTORC2 signaling. mTORC1 and mTORC2 co-regulate NPC cell migration and invasion. The revelation of the roles of mTOR signaling in NPC CSC establishment has implications for novel therapeutic strategies to treat relapsed and metastatic NPC and achieve durable remission.

Iron-Chelation Treatment by Novel Thiosemicarbazone Targets Major Signaling Pathways in Neuroblastoma

Despite constant advances in the field of pediatric oncology, the survival rate of high-risk neuroblastoma patients remains poor. The molecular and genetic features of neuroblastoma, such as MYCN amplification and stemness status, have established themselves not only as potent prognostic and predictive factors but also as intriguing targets for personalized therapy. Novel thiosemicarbazones target both total level and activity of a number of proteins involved in some of the most important signaling pathways in neuroblastoma. In this study, we found that di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) potently decreases N-MYC in MYCN-amplified and c-MYC in MYCN-nonamplified neuroblastoma cell lines. Furthermore, DpC succeeded in downregulating total EGFR and phosphorylation of its most prominent tyrosine residues through the involvement of NDRG1, a positive prognostic marker in neuroblastoma, which was markedly upregulated after thiosemicarbazone treatment. These findings could provide useful knowledge for the treatment of MYC-driven neuroblastomas that are unresponsive to conventional therapies.

Transcriptomic analysis reveals that mTOR pathway can be modulated in macrophage cells by the presence of cryptococcal cells

Cryptococcus neoformans and Cryptococcus gattii are the etiological agents of cryptococcosis, a high mortality disease. The development of such disease depends on the interaction of fungal cells with macrophages, in which they can reside and replicate. In order to dissect the molecular mechanisms by which cryptococcal cells modulate the activity of macrophages, a genome-scale comparative analysis of transcriptional changes in macrophages exposed to Cryptococcus spp. was conducted. Altered expression of nearly 40 genes was detected in macrophages exposed to cryptococcal cells. The major processes were associated with the mTOR pathway, whose associated genes exhibited decreased expression in macrophages incubated with cryptococcal cells. Phosphorylation of p70S6K and GSK-3β was also decreased in macrophages incubated with fungal cells. In this way, Cryptococci presence could drive the modulation of mTOR pathway in macrophages possibly to increase the survival of the pathogen.

mTOR-Rictor-EGFR axis in oncogenesis and diagnosis of glioblastoma multiforme

Glioblastoma multiforme (GBM) is one of the aggressive brain cancers with patients having less survival period upto 12-15 months. Mammalian target of rapamycin (mTOR) is a serine/threonine kinase, belongs to the phosphatidylinositol 3-kinases (PI3K) pathway and is involved in various cellular processes of cancer cells. Cancer metabolism is regulated by mTOR and its components. mTOR forms two complexes as mTORC1 and mTORC2. Studies have identified the key component of the mTORC2 complex, Rapamycin-insensitive companion of mammalian target of rapamycin (Rictor) plays a prominent role in the regulation of cancer cell proliferation and metabolism. Apart, growth factor receptor signaling such as epidermal growth factor signaling mediated by epidermal growth factor receptor (EGFR) regulates cancer-related processes. In EGFR signaling various other signaling cascades such as phosphatidyl-inositol 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR pathway) and Ras/Raf/mitogen-activated protein kinase/ERK kinase (MEK)/extracellular-signal-regulated kinase (ERK) -dependent signaling cross-talk each other. From various studies about GBM, it is very well established that Rictor and EGFR mediated signaling pathways majorly playing a pivotal role in chemoresistance and tumor aggressiveness. Recent studies have shown that non-coding RNAs such as microRNAs (miRs) and long non-coding RNAs (lncRNAs) regulate the EGFR and Rictor and sensitize the cells towards chemotherapeutic agents. Thus, understanding of microRNA mediated regulation of EGFR and Rictor will help in cancer prevention and management as well as a future therapy.

The Role of N-myc Downstream-Regulated Gene Family in Glioma Based on Bioinformatics Analysis

Glioma is the most common type of primary tumor in the central nervous system, and the molecular mechanisms remain elusive. N-myc downstream-regulated gene (NDRG) family is reported to take part in the pathogenesis of various diseases, including some preliminary exploration in glioma. However, there has been no bioinformatics analysis of NDRG family in glioma yet. Herein, we focused on the expression changes of NDRGs with their value in predicting patients' prognoses, upstream regulatory mechanisms (DNA mutation, DNA methylation, transcription factors, and microRNA regulation) and gene enrichment analysis based on co-expressed genes with data from public databases. Furthermore, the expression pattern of NDRGs was verified by the paired glioma and peritumoral samples in our institute. It was suggested that NDRGs were differentially expressed genes in glioma. In particular, the lower expression of NDRG2 or NDRG4 could serve as a predictor of higher grade tumor and poorer prognosis. Also, NDRGs might play a crucial role in signal transduction, energy metabolism, and cross-talk among cells in glioma, under the control of a complex regulatory network. This study enables us to better understand the role of NDRGs in glioma and with further research, it may contribute to the development of glioma treatment.

4-Acetylantrocamol LT3 Inhibits Glioblastoma Cell Growth and Downregulates DNA Repair Enzyme O6-Methylguanine-DNA Methyltransferase

Glioblastoma multiforme (GBM) is a deadly malignant brain tumor that is resistant to most clinical treatments. Novel therapeutic agents that are effective against GBM are required. Antrodia cinnamomea has shown antiproliferative effects in GBM cells. However, the exact mechanisms and bioactive components remain unclear. Thus, the present study aimed to investigate the effect and mechanism of 4-acetylantrocamol LT3 (4AALT3), a new ubiquinone from Antrodia cinnamomeamycelium, in vitro. U87 and U251 cell lines were treated with the indicated concentration of 4AALT3. Cell viability, cell colony-forming ability, migration, and the expression of proteins in well-known signaling pathways involved in the malignant properties of glioblastoma were then analyzed by CCK-8, colony formation, wound healing, and western blotting assays, respectively. We found that 4AALT3 significantly decreased cell viability, colony formation, and cell migration in both in vitro models. The epidermal growth factor receptor (EGFR), phosphatidylinositol-3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR), Hippo/yes-associated protein (YAP), and cAMP-response element binding protein (CREB) pathways were suppressed by 4AALT3. Moreover, 4AALT3 decreased the level of DNA repair enzyme O⁶-methylguanine-DNA methyltransferase and showed a synergistic effect with temozolomide. Our findings provide the basis for exploring the beneficial effect of 4AALT3 on GBM in vivo.

Rapid 3D Bioprinting of Glioblastoma Model Mimicking Native Biophysical Heterogeneity

Glioblastoma multiforme (GBM) is the most lethal primary brain tumor characterized by high cellular and molecular heterogeneity, hypervascularization, and innate drug resistance. Cellular components and extracellular matrix (ECM) are the two primary sources of heterogeneity in GBM. Here, biomimetic tri-regional GBM models with tumor regions, acellular ECM regions, and an endothelial region with regional stiffnesses patterned corresponding to the GBM stroma, pathological or normal brain parenchyma, and brain capillaries, are developed. Patient-derived GBM cells, human endothelial cells, and hyaluronic acid derivatives are used to generate a species-matched and biochemically relevant microenvironment. This in vitro study demonstrates that biophysical cues are involved in various tumor cell behaviors and angiogenic potentials and promote different molecular subtypes of GBM. The stiff models are enriched in the mesenchymal subtype, exhibit diffuse invasion of tumor cells, and induce protruding angiogenesis and higher drug resistance to temozolomide. Meanwhile, the soft models demonstrate enrichment in the classical subtype and support expansive cell growth. The three-dimensional bioprinting technology utilized in this study enables rapid, flexible, and reproducible patient-specific GBM modeling with biophysical heterogeneity that can be employed by future studies as a tunable system to interrogate GBM disease mechanisms and screen drug compounds.

Key genes and drug delivery systems to improve the efficiency of chemotherapy

Cancer cells can develop resistance to anticancer drugs, thereby becoming tolerant to treatment through different mechanisms. The biological mechanisms leading to the generation of anticancer treatment resistance include alterations in transmembrane proteins, DNA damage and repair mechanisms, alterations in target molecules, and genetic responses, among others. The most common anti-cancer drugs reported to develop resistance to cancer cells include cisplatin, doxorubicin, paclitaxel, and fluorouracil. These anticancer drugs have different mechanisms of action, and specific cancer types can be affected by different genes. The development of drug resistance is a cellular response which uses differential gene expression, to enable adaptation and survival of the cell to diverse threatening environmental agents. In this review, we briefly look at the key regulatory genes, their expression, as well as the responses and regulation of cancer cells when exposed to anticancer drugs, along with the incorporation of alternative nanocarriers as treatments to overcome anticancer drug resistance.

G3BPs tether the TSC complex to lysosomes and suppress mTORC1 signaling

Ras GTPase-activating protein-binding proteins 1 and 2 (G3BP1 and G3BP2, respectively) are widely recognized as core components of stress granules (SGs). We report that G3BPs reside at the cytoplasmic surface of lysosomes. They act in a non-redundant manner to anchor the tuberous sclerosis complex (TSC) protein complex to lysosomes and suppress activation of the metabolic master regulator mechanistic target of rapamycin complex 1 (mTORC1) by amino acids and insulin. Like the TSC complex, G3BP1 deficiency elicits phenotypes related to mTORC1 hyperactivity. In the context of tumors, low G3BP1 levels enhance mTORC1-driven breast cancer cell motility and correlate with adverse outcomes in patients. Furthermore, G3bp1 inhibition in zebrafish disturbs neuronal development and function, leading to white matter heterotopia and neuronal hyperactivity. Thus, G3BPs are not only core components of SGs but also a key element of lysosomal TSC-mTORC1 signaling.

The Role of Hypoxia in Glioblastoma Radiotherapy Resistance

Glioblastoma (GB) (grade IV astrocytoma) is the most malignant type of primary brain tumor with a 16 months median survival time following diagnosis. Despite increasing attention regarding the development of targeted therapies for GB that resulted in around 450 clinical trials currently undergoing, radiotherapy still remains the most clinically effective treatment for these patients. Nevertheless, radiotherapy resistance (radioresistance) is commonly observed in GB patients leading to tumor recurrence and eventually patient death. It is therefore essential to unravel the molecular mechanisms underpinning GB cell radioresistance in order to develop novel strategies and combinational therapies focused on enhancing tumor cell sensitivity to radiotherapy. In this review, we present a comprehensive examination of the current literature regarding the role of hypoxia (O2 partial pressure less than 10 mmHg), a main GB microenvironmental factor, in radioresistance with the ultimate goal of identifying potential molecular markers and therapeutic targets to overcome this issue in the future.

Crystal and solution structure of NDRG1, a membrane-binding protein linked to myelination and tumour suppression

N-myc downstream-regulated gene 1 (NDRG1) is a tumour suppressor involved in vesicular trafficking and stress response. NDRG1 participates in peripheral nerve myelination, and mutations in the NDRG1 gene lead to Charcot-Marie-Tooth neuropathy. The 43-kDa NDRG1 is considered as an inactive member of the α/β hydrolase superfamily. In addition to a central α/β hydrolase fold domain, NDRG1 consists of a short N terminus and a C-terminal region with three 10-residue repeats. We determined the crystal structure of the α/β hydrolase domain of human NDRG1 and characterised the structure and dynamics of full-length NDRG1. The structure of the α/β hydrolase domain resembles the canonical α/β hydrolase fold with a central β sheet surrounded by α helices. Small-angle X-ray scattering and CD spectroscopy indicated a variable conformation for the N- and C-terminal regions. NDRG1 binds to various types of lipid vesicles, and the conformation of the C-terminal region is modulated upon lipid interaction. Intriguingly, NDRG1 interacts with metal ions, such as nickel, but is prone to aggregation in their presence. Our results uncover the structural and dynamic features of NDRG1, as well as elucidate its interactions with metals and lipids, and encourage studies to identify a putative hydrolase activity of NDRG1. DATABASES: The coordinates and structure factors for the crystal structure of human NDRG1 were deposited to PDB (PDB ID: 6ZMM).

Regulating Tumor N6 -Methyladenosine Methylation Landscape using Hypoxia-Modulating OsSx Nanoparticles

The epigenetic dysregulation and hypoxia are two important factors that drive tumor malignancy, and N⁶ -methyladenosine (m⁶ A) in mRNA is involved in the regulation of gene expression. Herein, a nanocatalyst OsS_x -PEG (PEG = poly(ethylene glycol)) nanoparticles (NPs) as O₂ modulator is developed to improve tumor hypoxia. OsS_x -PEG NPs can significantly downregulate genes involved in hypoxia pathway. Interestingly, OsS_x -PEG NPs elevate RNA m⁶ A methylation levels to cause the m⁶ A-dependent mRNA degradation of the hypoxia-related genes. Moreover, OsS_x -PEG NPs can regulate the expression of RNA m⁶ A methyltransferases and demethylases. Finally, DOX@OsS_x -PEG (DOX = doxorubicin; utilized as a model drug) NPs modulate tumor hypoxia and regulate mRNA m⁶ A methylation of hypoxia-related genes in vivo. As the first report about relationship between catalytic nanomaterials and RNA modifications, the research opens a new avenue for unveiling the underlying action mechanisms of hypoxia-modulating nanomaterials and shows potential of regulating RNA modification to overcome chemoresistance.

Identification and Characterization of Cancer Cells That Initiate Metastases to the Brain and Other Organs

Specific biological properties of those circulating cancer cells that are the origin of brain metastases (BM) are not well understood. Here, single circulating breast cancer cells were fate-tracked during all steps of the brain metastatic cascade in mice after intracardial injection over weeks. A novel in vivo two-photon microscopy methodology was developed that allowed to determine the specific cellular and molecular features of breast cancer cells that homed in the brain, extravasated, and successfully established a brain macrometastasis. Those BM-initiating breast cancer cells (BMIC) were mainly originating from a slow-cycling subpopulation that included only 16% to 20% of all circulating cancer cells. BMICs showed enrichment of various markers of cellular stemness. As a proof of principle for the principal usefulness of this approach, expression profiling of BMICs versus non-BMICs was performed, which revealed upregulation of NDRG1 in the slow-cycling BMIC subpopulation in one BM model. Here, BM development was completely suppressed when NDRG1 expression was downregulated. In accordance, in primary human breast cancer, NDRG1 expression was heterogeneous, and high NDRG1 expression was associated with shorter metastasis-free survival. In conclusion, our data identify temporary slow-cycling breast cancer cells as the dominant source of brain and other metastases and demonstrates that this can lead to better understanding of BMIC-relevant pathways, including potential new approaches to prevent BM in patients. IMPLICATIONS: Cancer cells responsible for successful brain metastasis outgrowth are slow cycling and harbor stemness features. The molecular characteristics of these metastasis-initiating cells can be studied using intravital microscopy technology.

Pharmacological Inhibition of mTORC2 Reduces Migration and Metastasis in Melanoma

Despite recent advances in therapy, liver metastasis from melanoma is still associated with poor prognosis. Although targeting the mTOR signaling pathway exerts potent anti-tumor activity, little is known about specific mTORC2 inhibition regarding liver metastasis. Using the novel mTORC2 specific inhibitor JR-AB2-011, we show significantly reduced migration and invasion capacity by impaired activation of MMP2 in melanoma cells. In addition, blockade of mTORC2 induces cell death by non-apoptotic pathways and reduces tumor cell proliferation rate dose-dependently. Furthermore, a significant reduction of liver metastasis was detected in a syngeneic murine metastasis model upon therapy with JR-AB2-011 as determined by in vivo imaging and necropsy. Hence, our study for the first time highlights the impact of the pharmacological blockade of mTORC2 as a potent novel anti-cancer approach for liver metastasis from melanoma.

Activation of nuclear factor-κB in the angiogenesis of glioma: Insights into the associated molecular mechanisms and targeted therapies

Glioma is the most commonly observed primary intracranial tumour and is associated with massive angiogenesis. Glioma neovascularization provides nutrients for the growth and metabolism of tumour tissues, promotes tumour cell division and proliferation, and provides conditions ideal for the infiltration and migration of tumour cells to distant places. Growing evidence suggests that there is a correlation between the activation of nuclear factor (NF)‐κB and the angiogenesis of glioma. In this review article, we highlighted the functions of NF‐κB in the angiogenesis of glioma, showing that NF‐κB activation plays a pivotal role in the growth and progression of glioma angiogenesis and is a rational therapeutic target for antiangiogenic strategies aimed at glioma.

Prohibitin, STAT3 and SH2D4A physically and functionally interact in tumor cell mitochondria

Chromosome 8p is frequently deleted in various cancer entities and has been shown to correlate with poor patient survival. SH2D4A is located on chromosome 8p and prevents the nuclear translocation of the pro-tumorigenic transcription factor STAT3. Here, we investigated the interaction of SH2D4A and STAT3 to shed light on the non-canonical functions of STAT3 in cooperation with the tumor suppressor SH2D4A. Using an immunoprecipitation-mass spectrometry (IP-MS) approach, we identified the mitochondrial scaffold proteins prohibitin 1 (PHB1) and prohibitin 2 (PHB2) among other proteins to potentially bind to SH2D4A. Co-immunoprecipitation and proximity ligation assays confirmed direct interactions of STAT3, PHB1, and SH2D4A in situ and in vitro. In addition, cell fractionation and immunofluorescence staining revealed co-localization of these proteins with mitochondria. These interactions were selectively interrupted by the small molecule and PHB ligand FL3. Furthermore, FL3 led to a reduction of STAT3 protein levels, STAT3 transcriptional activity, and HIF1α protein stabilization upon dimethyloxalylglycine (DMOG) treatment. Besides, mitochondrial fusion and fission markers, L-OPA1, Mfn1, and FIS1, were dysregulated upon FL3 treatment. This dysregulated morphology was accompanied by significant reduction of mitochondrial respiration, thus, FL3 significantly diminished mitochondrial respirational capacity. In contrast, SH2D4A knockout increased mitochondrial respiration, whereas FL3 reversed the effect of SH2D4A knockout. The here described results indicate that the interaction of SH2D4A and PHB1 is involved in the mitochondrial function and integrity. The demonstrated interaction with STAT3, accompanied by its reduction of transcriptional activity, further suggests that SH2D4A is linking STAT3 to its mitochondrial functions, and inhibition of PHB-interaction may have therapeutic effects in tumor cells with STAT3 activation.

Serum and Glucocorticoid-Inducible Kinase 1 (SGK1) in NSCLC Therapy

Non-small cell lung cancer (NSCLC) remains the most prevalent and one of the deadliest cancers worldwide. Despite recent success, there is still an urgent need for new therapeutic strategies. It is also becoming increasingly evident that combinatorial approaches are more effective than single modality treatments. This review proposes that the serum and glucocorticoid-inducible kinase 1 (SGK1) may represent an attractive target for therapy of NSCLC. Although ubiquitously expressed, SGK1 deletion in mice causes only mild defects of ion physiology. The frequent overexpression of SGK1 in tumors is likely stress-induced and provides a therapeutic window to spare normal tissues. SGK1 appears to promote oncogenic signaling aimed at preserving the survival and fitness of cancer cells. Most importantly, recent investigations have revealed the ability of SGK1 to skew immune-cell differentiation toward pro-tumorigenic phenotypes. Future studies are needed to fully evaluate the potential of SGK1 as a therapeutic target in combinatorial treatments of NSCLC. However, based on what is currently known, SGK1 inactivation can result in anti-oncogenic effects both on tumor cells and on the immune microenvironment. A first generation of small molecules to inactivate SGK1 has already been already produced.

The Regulatory Properties of the Ccr4-Not Complex

The mammalian Ccr4–Not complex, carbon catabolite repression 4 (Ccr4)-negative on TATA-less (Not), is a large, highly conserved, multifunctional assembly of proteins that acts at different cellular levels to regulate gene expression. In the nucleus, it is involved in the regulation of the cell cycle, chromatin modification, activation and inhibition of transcription initiation, control of transcription elongation, RNA export, nuclear RNA surveillance, and DNA damage repair. In the cytoplasm, the Ccr4–Not complex plays a central role in mRNA decay and affects protein quality control. Most of our original knowledge of the Ccr4–Not complex is derived, primarily, from studies in yeast. More recent studies have shown that the mammalian complex has a comparable structure and similar properties. In this review, we summarize the evidence for the multiple roles of both the yeast and mammalian Ccr4–Not complexes, highlighting their similarities.

The Enigmatic Role of Serum & Glucocorticoid Inducible Kinase 1 in the Endometrium

The serum- and glucocorticoid-inducible kinase 1 (SGK1) is subject to genetic up-regulation by diverse stimulators including glucocorticoids, mineralocorticoids, dehydration, ischemia, radiation and hyperosmotic shock. To become active, the expressed kinase requires phosphorylation, which is accomplished by PI3K/PDK1 and mTOR dependent signaling. SGK1 enhances the expression/activity of various transport proteins including Na+/K+-ATPase as well as ion-, glucose-, and amino acid- carriers in the plasma membrane. SGK1 can further up-regulate diverse ion channels, such as Na+-, Ca2+-, K+- and Cl- channels. SGK1 regulates expression/activity of a wide variety of transcription factors (such as FKHRL1/Foxo3a, β-catenin, NFκB and p53). SGK1 thus contributes to the regulation of transport, glycolysis, angiogenesis, cell survival, immune regulation, cell migration, tissue fibrosis and tissue calcification. In this review we summarized the current findings that SGK1 plays a crucial function in the regulation of endometrial function. Specifically, it plays a dual role in the regulation of endometrial receptivity necessary for implantation and, subsequently in pregnancy maintenance. Furthermore, fetal programming of blood pressure regulation requires maternal SGK1. Underlying mechanisms are, however, still ill-defined and there is a substantial need for additional information to fully understand the role of SGK1 in the orchestration of embryo implantation, embryo survival and fetal programming.

Pharmacological targeting and the diverse functions of the metastasis suppressor, NDRG1, in cancer

N-myc downstream regulated gene-1 (NDRG1) is a potent metastasis suppressor that is regulated by hypoxia, metal ions including iron, the free radical nitric oxide (NO^.), and various stress stimuli. This intriguing molecule exhibits diverse functions in cancer, inhibiting epithelial-mesenchymal transition (EMT), cell migration and angiogenesis by modulation of a plethora of oncogenes via cellular signaling. Thus, pharmacological targeting of NDRG1 signaling in cancer is a promising therapeutic strategy. Of note, novel anti-tumor agents of the di-2-pyridylketone thiosemicarbazone series, which exert the "double punch" mechanism by binding metal ions to form redox-active complexes, have been demonstrated to markedly up-regulate NDRG1 expression in cancer cells. This review describes the mechanisms underlying NDRG1 modulation by the thiosemicarbazones and the diverse effects NDRG1 exerts in cancer. As a major induction mechanism, iron depletion appears critical, with NO^. also inducing NDRG1 through its ability to bind iron and generate dinitrosyl-dithiol iron complexes, which are then effluxed from cells. Apart from its potent anti-metastatic role, several studies have reported a pro-oncogenic role of NDRG1 in a number of cancer-types. Hence, it has been suggested that NDRG1 plays pleiotropic roles depending on the cancer-type. The molecular mechanism(s) underlying NDRG1 pleiotropy remain elusive, but are linked to differential regulation of WNT signaling and potentially differential interaction with the tumor suppressor, PTEN. This review discusses NDRG1 induction mechanisms by metal ions and NO^. and both the anti- and possible pro-oncogenic functions of NDRG1 in multiple cancer-types and compares the opposite effects this protein exerts on cancer progression.

Investigating Glioblastoma Response to Hypoxia

Glioblastoma (GB) is the most common and deadly type of primary malignant brain tumor with an average patient survival of only 15–17 months. GBs typically have hypoxic regions associated with aggressiveness and chemoresistance. Using patient derived GB cells, we characterized how GB responds to hypoxia. We noted a hypoxia-dependent glycolytic switch characterized by the up-regulation of HK2, PFKFB3, PFKFB4, LDHA, PDK1, SLC2A1/GLUT-1, CA9/CAIX, and SLC16A3/MCT-4. Moreover, many proangiogenic genes and proteins, including VEGFA, VEGFC, VEGFD, PGF/PlGF, ADM, ANGPTL4, and SERPINE1/PAI-1 were up-regulated during hypoxia. We detected the hypoxic induction of invasion proteins, including the plasminogen receptor, S100A10, and the urokinase plasminogen activator receptor, uPAR. Furthermore, we observed a hypoxia-dependent up-regulation of the autophagy genes, BNIP-3 and DDIT4 and of the multi-functional protein, NDRG1 associated with GB chemoresistance; and down-regulation of EGR1 and TFRC (Graphical abstract). Analysis of GB patient cohorts’ revealed differential expression of these genes in patient samples (except SLC16A3) compared to non-neoplastic brain tissue. High expression of SLC2A1, LDHA, PDK1, PFKFB4, HK2, VEGFA, SERPINE1, TFRC, and ADM was associated with significantly lower overall survival. Together these data provide important information regarding GB response to hypoxia which could support the development of more effective treatments for GB patients.

The prospect of serum and glucocorticoid-inducible kinase 1 (SGK1) in cancer therapy: a rising star

Serum and glucocorticoid-inducible kinase 1 (SGK1) is an AGC kinase that has been reported to be involved in a variety of physiological and pathological processes. Recent evidence has accumulated that SGK1 acts as an essential Akt-independent mediator of phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) signaling pathway in cancer. SGK1 is overexpressed in several tumors, including prostate cancer, colorectal carcinoma, glioblastoma, breast cancer, and endometrial cancer. The functions of SGK1 include regulating tumor growth, survival, metastasis, autophagy, immunoregulation, calcium (Ca²⁺) signaling, cancer stem cells, cell cycle, and therapeutic resistance. In this review, we introduce the pleiotropic role of SGK1 in the development and progression of tumors, summarize its downstream targets, and integrate the knowledge provided by preclinical studies that the prospect of SGK1 inhibition as a potential therapeutic approach.

Identifying Predictive Gene Expression and Signature Related to Temozolomide Sensitivity of Glioblastomas

Temozolomide (TMZ) is considered a standard chemotherapeutic agent for glioblastoma (GBM). Characterizing the biological molecules and signaling pathways involved in TMZ sensitivity would be helpful for selecting therapeutic schemes and evaluating prognosis for GBM. Thus, in the present study, we selected 34 glioma cell lines paired with specific IC₅₀ values of TMZ obtained from CancerRxGene and RNA-seq data downloaded from the Cancer Cell Line Encyclopedia to identify genes related to TMZ sensitivity. The results showed that 1,373 genes were related to the response of GBM cells to TMZ. Biological function analysis indicated that epithelial–mesenchymal transition, Wnt signaling, and immune response were the most significantly activated functions in TMZ-resistant cell lines. Additionally, negative regulation of telomere maintenance via telomerase was enriched in TMZ-sensitive glioma cell lines. We also preliminarily observed a synergistic effect of combination treatment comprising TMZ and a telomerase inhibitor in vitro. We identified six genes (MROH8, BET1, PTPRN2, STC1, NKX3-1, and ARMC10) using the random survival forests variable hunting algorithm based on the minimum error rate of the gene combination and constructed a gene expression signature. The signature was strongly related to GBM clinical characteristics and exhibited good prognosis accuracy for both The Cancer Genome Atlas (TCGA) and Chinese Glioma Genome Atlas (CGGA) datasets. Patients in the high score group had a shorter survival time than those in the low score group (11.2 vs. 22.2 months, hazard ratio = 7.31, p = 4.59e−11) of the TCGA dataset. The CGGA dataset was selected as a validation group with 40 patients in the high score set and 43 patients in the low score set (12.5 vs. 28.8 months, hazard ratio = 3.42, p = 8.61e−5). Moreover, the signature showed a better prognostic value than MGMT promoter methylation in both datasets. We also developed a nomogram for clinical use that integrated the TMZ response signature and four other risk factors to individually predict patient survival after TMZ chemotherapy. Overall, our study provides promising therapeutic targets and potential guidance for adjuvant therapy of GBM.