Knock-Down of Mucolipin 1 Channel Promotes Tumor Progression and Invasion in Human Glioblastoma Cell Lines

Targeting mineral metabolism in cancer: Insights into signaling pathways and therapeutic strategies

Cancer remains the second leading cause of death worldwide, emphasizing the critical need for effective treatment and control strategies. Essential minerals such as copper, iron, zinc, selenium, phosphorous, calcium, and magnesium are integral to various biological processes and significantly influence cancer progression through altered metabolic pathways. For example, dysregulated copper levels promote tumor growth, while cancer cells exhibit an increased dependency on iron for signaling and redox reactions. Zinc influences tumor development through pathways such as Akt-p21. Selenium, primarily through its role in selenoproteins, exhibits anticancer potential but may also contribute to tumor progression. Similarly, dietary phosphate exacerbates tumorigenesis, metastasis, and angiogenesis through signaling pathway activation. Calcium, the most abundant mineral in the body, is tightly regulated within cells, and its dysregulation is a hallmark of various cancers. Magnesium deficiency, on the other hand, promotes cancer progression by fostering inflammation and free radical-induced DNA mutations. Interestingly, magnesium also plays a dual role, with low levels enhancing epithelial-mesenchymal transition (EMT), a critical process in cancer metastasis. This complex interplay of essential minerals underscores their potential as therapeutic targets. Dysregulation of these minerals and their pathways could be exploited to selectively target cancer cells, offering novel therapeutic strategies. This review summarizes current research on the abnormal accumulation or depletion of these microelements in tumor biology, drawing evidence from animal models, cell lines, and clinical samples. We also highlight the potential of these minerals as biomarkers for cancer diagnosis and prognosis, as well as therapeutic approaches involving metal chelators, pharmacological agents, and nanotechnology. By highlighting the intricate roles of these minerals in cancer biology, we aim to inspire further research in this critical yet underexplored area of oncology.

Targeting TRPML3 inhibits proliferation and invasion, and enhances doxorubicin sensitivity by disrupting lysosomal acidification and mitochondrial function in triple-negative breast cancer

TNBC remains the most aggressive and therapy-resistant type of breast cancer, for which efficient targeted therapies have not been developed yet. Here, we identified TRPML3 (ML3) as a potential therapeutic target in TNBC. Our data showed that ML3 is significantly upregulated in TNBC cells compared with nontumorigenic control cells. ML3 knockdown (KD) impairs TNBC cell proliferation by inducing cell cycle arrest and caspase-dependent apoptosis. ML3 KD also inhibits TNBC cell migration and invasion. Mechanistically, ML3 KD reduces lysosomal number and enhances lysosomal acidification, which in turn activates mTORC1, thereby inhibiting autophagy initiation and flux. This disruption negatively impacts mitochondrial function, as evidenced by reduced ATP production, increased ROS and NO production, and mitochondrial fragmentation. Importantly, ML3 KD enhances TNBC cell sensitivity to doxorubicin and paclitaxel. The finding suggests that targeting ML3 disrupts lysosomal and mitochondrial homeostasis and enhance chemosensitivity, presenting ML3 as a potential therapeutic vulnerability in TNBC enhancing chemosensitivity.

Ion channel expression and function in glioblastoma multiforme (GBM): pathophysiological mechanisms and therapeutic potential

Glioblastoma Multiforme (GBM) is a highly malignant and diffusely invasive WHO Grade IV brain tumor arising from glial and neural stem cells. GBM is characterized by rapid proliferation and migration, aggressive invasion of local brain parenchyma, a hypoxic microenvironment, resistance to apoptosis and high vascular remodeling and angiogenesis. These hallmarks contribute to a near universal tumor recurrence after treatment or resection and poor patient prognosis. Ion channels, a superfamily of proteins responsible for permitting ion flux across otherwise impermeant membranes, show extensive remodeling in GBM with aberrant function mechanistically linked to manipulation of each of these hallmarks. In this review, we will discuss the known links between ion channel expression and activity and cellular processes that are enhanced or perturbed during GBM formation or progression. We will also discuss the extent to which basic or translational findings on ion channels in GBM samples or cell lines have shown preclinical promise towards the development of improved therapeutics against GBMs.

Correlation of organelle interactions in the development of non-alcoholic fatty liver disease

Organelles, despite having distinct functions, interact with each other. Interactions between organelles typically occur at membrane contact sites (MCSs) to maintain cellular homeostasis, allowing the exchange of metabolites and other pieces of information required for normal cellular physiology. Imbalances in organelle interactions may lead to various pathological processes. Increasing evidence suggests that abnormalorganelle interactions contribute to the pathogenesis of non-alcoholic fatty liver disease (NAFLD). However, the key role of organelle interactions in NAFLD has not been fully evaluated and researched. In this review, we summarize the role of organelle interactions in NAFLD and emphasize their correlation with cellular calcium homeostasis, lipid transport, and mitochondrial dynamics.

TRPML1 ameliorates seizures-related neuronal injury by regulating autophagy and lysosomal biogenesis via Ca2+/TFEB signaling pathway

Alterations in autophagy have been observed in epilepsy, although their exact etiopathogenesis remains elusive. Transient Receptor Potential Mucolipin Protein 1 (TRPML1) is an ion channel protein that regulates autophagy and lysosome biogenesis. To explore the role of TRPML1 in seizures-induced neuronal injury and the potential mechanisms involved, an hyperexcitable neuronal model induced by Mg2+-free solution was used for the study. Our results revealed that TRPML1 expression was upregulated after seizures, which was accompanied by intracellular ROS accumulation, mitochondrial damage, and neuronal apoptosis. Activation of TRPML1 by ML-SA1 diminished intracellular ROS, restored mitochondrial function, and subsequently alleviated neuronal apoptosis. Conversely, inhibition of TRPML1 had the opposite effect. Further examination revealed that the accumulation of ROS and damaged mitochondria was associated with interrupted mitophagy flux and enlarged defective lysosomes, which were attenuated by TRPML1 activation. Mechanistically, TRPML1 activation allows more Ca2+ to permeate from the lysosome into the cytoplasm, resulting in the dephosphorylation of TFEB and its nuclear translocation. This process further enhances autophagy initiation and lysosomal biogenesis. Additionally, the expression of TRPML1 is positively regulated by WTAP-mediated m6A modification. Our findings highlighted crucial roles of TRPML1 and autophagy in seizures-induced neuronal injury, which provides a new target for epilepsy treatment.

The intersection between cysteine proteases, Ca2+ signalling and cancer cell apoptosis

Apoptosis is a highly complex and regulated cell death pathway that safeguards the physiological balance between life and death. Over the past decade, the role of Ca2+ signalling in apoptosis and the mechanisms involved have become clearer. The initiation and execution of apoptosis is coordinated by three distinct groups of cysteines proteases: the caspase, calpain and cathepsin families. Beyond its physiological importance, the ability to evade apoptosis is a prominent hallmark of cancer cells. In this review, we will explore the involvement of Ca2+ in the regulation of caspase, calpain and cathepsin activity, and how the actions of these cysteine proteases alter intracellular Ca2+ handling during apoptosis. We will also explore how apoptosis resistance can be achieved in cancer cells through deregulation of cysteine proteases and remodelling of the Ca2+ signalling toolkit.

Blunting ROS/TRPML1 pathway protects AFB1-induced porcine intestinal epithelial cells apoptosis by restoring impaired autophagic flux

Aflatoxin B1 (AFB1) is a stable mycotoxin that contaminates animal feed on a large scale and causes severe damage to intestinal cells, induces inflammation and stimulates autophagy. Transient receptor potential mucolipin subfamily 1 (TRPML1) is a regulatory factor of autophagy, but the underlying mechanisms of TRPML1-mediated autophagy in AFB1 intestine toxicity remain elucidated. In the present study, AFB1 (0, 5, 10 μg/mL) was shown to reduce cell viability, increase reactive oxygen species (ROS) accumulation and apoptosis rate. Additionally, AFB1 caused structural damage to mitochondria and lysosomes and increased autophagosomes numbers. Furthermore, AFB1 promoted Ca²⁺ release by activating the TRPML1 channel, stimulated the expression of autophagy-related proteins, and induced autophagic flux blockade. Moreover, pharmacological inhibition of autophagosome formation by 3-methyladenine attenuated AFB1-induced apoptosis by downregulating the levels of TRPML1 and ROS, whereas blockade of autophagosome-lysosomal fusion by chloroquine alleviated AFB1-induced apoptosis by upregulating TRPML1 expression and exacerbating ROS accumulation. Intriguingly, blocking AFB1-induced autophagic flux generated ROS- and TRPML1-dependent cell death, as shown by the decreased apoptosis in the presence the free radical scavenger N-Acetyl-L-cysteine and the TRPML1 inhibitor ML-SI1. Overall, these results showed that AFB1 promoted apoptosis of IPEC-J2 cells by disrupting autophagic flux through activation of the ROS/TRPML1 pathway.

Highly Potent and Selective Dopamine D4 Receptor Antagonists Potentially Useful for the Treatment of Glioblastoma

To better understand the role of dopamine D₄ receptor (D₄R) in glioblastoma (GBM), in the present paper, new ligands endowed with high affinity and selectivity for D₄R were discovered starting from the brain penetrant and D₄R selective lead compound 1-(3-(4-phenylpiperazin-1-yl)propyl)-3,4-dihydroquinolin-2(1H)-one (6). In particular, the D₄R antagonist 24, showing the highest affinity and selectivity over D₂R and D₃R within the series (D₂/D₄ = 8318, D₃/D₄ = 3715), and the biased ligand 29, partially activating D₄R G_i-/G_o-protein and blocking β-arrestin recruitment, emerged as the most interesting compounds. These compounds, evaluated for their GBM antitumor activity, induced a decreased viability of GBM cell lines and primary GBM stem cells (GSC#83), with the maximal efficacy being reached at a concentration of 10 μM. Interestingly, the treatment with both compounds 24 and 29 induced an increased effect in reducing the cell viability with respect to temozolomide, which is the first-choice chemotherapeutic drug in GBM.

Coexpression of TRPML1 and TRPML2 Mucolipin Channels Affects the Survival of Glioblastoma Patients

Among brain cancers, glioblastoma (GBM) is the most malignant glioma with an extremely poor prognosis. It is characterized by high cell heterogeneity, which can be linked to its high malignancy. We have previously demonstrated that TRPML1 channels affect the OS of GBM patients. Herein, by RT-PCR, FACS and Western blot, we demonstrated that TRPML1 and TRPML2 channels are differently expressed in GBM patients and cell lines. Moreover, these channels partially colocalized in ER and lysosomal compartments in GBM cell lines, as evaluated by confocal analysis. Interestingly, the silencing of TRPML1 or TRPML2 by RNA interference results in the decrease in the other receptor at protein level. Moreover, the double knockdown of TRPML1 and TRPML2 leads to increased GBM cell survival with respect to single-channel-silenced cells, and improves migration and invasion ability of U251 cells. Finally, the Kaplan–Meier survival analysis demonstrated that patients with high TRPML2 expression in absence of TRPML1 expression strongly correlates with short OS, whereas high TRPML1 associated with low TRPML2 mRNA expression correlates with longer OS in GBM patients. The worst OS in GBM patients is associated with the loss of both TRPML1 and TRPML2 channels.

Functional In Vitro Assessment of VEGFA/NOTCH2 Signaling Pathway and pRB Proteasomal Degradation and the Clinical Relevance of Mucolipin TRPML2 Overexpression in Glioblastoma Patients

Glioblastoma (GBM) is the most malignant glioma with an extremely poor prognosis. It is characterized by high vascularization and its growth depends on the formation of new blood vessels. We have previously demonstrated that TRPML2 mucolipin channel expression increases with the glioma pathological grade. Herein by ddPCR and Western blot we found that the silencing of TRPML2 inhibits expression of the VEGFA/Notch2 angiogenic pathway. Moreover, the VEGFA/Notch2 expression increased in T98 and U251 cells stimulated with the TRPML2 agonist, ML2-SA1, or by enforced-TRPML2 levels. In addition, changes in TRPML2 expression or ML2-SA1-induced stimulation, affected Notch2 activation and VEGFA release. An increased invasion capability, associated with a reduced VEGF/VEGFR2 expression and increased vimentin and CD44 epithelial-mesenchymal transition markers in siTRPML2, but not in enforced-TRPML2 or ML2-SA1-stimulated glioma cells, was demonstrated. Furthermore, an increased sensitivity to Doxorubicin cytotoxicity was demonstrated in siTRPML2, whereas ML2-SA1-treated GBM cells were more resistant. The role of proteasome in Cathepsin B-dependent and -independent pRB degradation in siTRPML2 compared with siGLO cells was studied. Finally, through Kaplan-Meier analysis, we found that high TRPML2 mRNA expression strongly correlates with short survival in GBM patients, supporting TRPML2 as a negative prognostic factor in GBM patients.

TPC2 targeting evolution: Leveraging therapeutic opportunities for cancer

Growing evidence implicates a vital role for TPC2/Ca²⁺ signaling in pathophysiological processes attributed to cancer, raising questions regarding the utility of TPC2 as a cancer therapeutic target. In this issue of Cell Chemical Biology, Müller et al. (2021) develop TPC2 inhibitors, SG005 and SG-094, exhibiting anti-tumor effects with potential translational relevance.