Gabriel Ichim

• PhD
• Group Leader at Cancer Research Center of Lyon, French National Centre for Scientific Research

Dependence receptors (DRs) induce cell death by apoptosis in the absence of their ligand. Among them, Kremen1 was first described to induce cancer cell death in the absence of its ligand, DKK1. Nevertheless, the exact mechanism of Kremen1-triggered cell death remains unexplored. In this study, we demonstrate that Kremen1 induces cell death with aut...

Background & Aims Owing to unexplained interpatient variation and treatment failure in hepatocellular carcinoma (HCC), novel therapeutic approaches remain an urgent clinical need. Hepatic neurons, belonging to the autonomic nervous system (ANS), mediate liver/whole body crosstalk. Pathological innervation of the ANS has been identified in cancer, n...

Recent studies have unveiled unexpected connections between cell death and cell motility. While traditionally recognized for their pro-apoptotic roles, caspases have emerged as regulators of physiological processes beyond cell death, including cellular differentiation and motility. In some particularly aggressive cancers like melanoma, caspase-3, a...

Inflammasomes are multiprotein platforms that control caspase-1 activation, which process the inactive precursor forms of the inflammatory cytokines IL-1β and IL-18, leading to an inflammatory type of programmed cell death called pyroptosis. Studying inflammasome-driven processes, such as pyroptosis-induced cell swelling, under controlled condition...

In lung adenocarcinoma (LUAD), EGFR-targeted therapies often result in incomplete tumor responses followed by disease progression caused by acquired resistance. As EGFR mutations are truncal (i.e., present in every cell of a tumor), it remains unclear why a fraction of tumor cells can survive in the presence of drug treatment. It is increasingly...

Neuroblastoma (NB) is the most common pediatric tumor and is currently treated by several types of therapies including chemotherapies, such as bortezomib treatment. However, resistance to bortezomib is frequently observed by mechanisms that remain to be deciphered. Bortezomib treatment leads to caspase activation and aggresome formation. Using mode...

Mixed lineage kinase-like (MLKL) is activated by RHIM-domain containing kinase (RIPK)3 to permeabilize the plasma-membrane and execute necroptosis, a form of regulated necrosis. We found that MLKL is activated in an atypical, RIPK3- and necroptosis-independent manner downstream of Toll-like receptor 3, resulting in its translocation to lysosomes an...

Nutrient availability is a key determinant of tumor cell behavior. While nutrient‐rich conditions favor proliferation and tumor growth, scarcity, and particularly glutamine starvation, promotes cell dedifferentiation and chemoresistance. Here, linking ribosome biogenesis plasticity with tumor cell fate, we uncover that the amino acid sensor general...

Inflammasomes are multiprotein platforms which control caspase-1 activation, leading to the processing of proinflammatory cytokines into mature and active cytokines IL-1β and IL-18, and to pyroptosis through the cleavage of gasdermin-D (GSDMD). Inflammasomes assemble upon activation of specific cytosolic pattern recognition receptors (PRRs) by dama...

Membrane structural integrity is essential for optimal mitochondrial function. These organelles produce the energy needed for all vital processes, provided their outer and inner membranes are intact. This prevents the release of mitochondrial apoptogenic factors into the cytosol and ensures intact mitochondrial membrane potential (ΔΨm) to sustain A...

BCL-2 and related proteins are major regulators of apoptosis that have emerged as promising targets for the elimination senescent cells (or ‘senolysis’) to improve age-related diseases and promote healthy ageing. However, seminal observations and recent findings shed light on non-apoptotic roles of BCL-2 proteins in the regulation of cellular senes...

Nutrient availability is a key determinant of tumor cell behavior. While nutrient-rich conditions favor proliferation and tumor growth, scarcity, and particularly glutamine starvation, promotes cell dedifferentiation and chemoresistance. Here, linking ribosome biogenesis plasticity with tumor cell fate, we uncover that the amino acid sensor GCN2 re...

As a cellular intrinsic mechanism leading to cellular demise, apoptosis was thoroughly characterized from a mechanistic perspective. Nowadays there is an increasing interest in describing the non-cell autonomous or community effects of apoptosis, especially in the context of resistance to cancer treatments. Transitioning from cell-centered to cell...

Metastases are the main cause of death in cancer patients, and platelets are largely known for their contribution in cancer progression. However, targeting platelets is highly challenging given their paramount function in hemostasis. Using a high-throughput screening and platelet-induced breast tumor cell survival (PITCS) assay as endpoint, we iden...

The protease caspase-3 is a key mediator of apoptotic programmed cell death. But weak or transient caspase activity can contribute to neuronal differentiation, axonal pathfinding, and synaptic long-term depression. Despite the importance of sublethal, or nonapoptotic, caspase activity in neurodevelopment and neural plasticity, there has been no sim...

As a cellular intrinsic mechanism leading to cellular demise, apoptosis was thoroughly characterized from a mechanistic perspective. Nowadays there is an increasing interest in describing the non-cell autonomous or community effects of apoptosis, especially in the context of resistance to cancer treatments. Transitioning from cell-centered to cell...

Since the Nobel Prize award more than twenty years ago for discovering the core apoptotic pathway in C. elegans, apoptosis and various other forms of regulated cell death have been thoroughly characterized by researchers around the world. Although many aspects of regulated cell death still remain to be elucidated in specific cell subtypes and disea...

Micronuclei are DNA-containing structures separate from the nucleus found in cancer cells. Micronuclei are recognized by the immune sensor axis cGAS/STING, driving cancer metastasis. The mitochondrial apoptosis apparatus can be experimentally triggered to a non-apoptotic level, and this can drive the appearance of micronuclei through the Caspase-ac...

Mitochondrial dysfunction is interconnected with cancer. Nevertheless, how defective mitochondria promote cancer is poorly understood. We find that mitochondrial dysfunction promotes DNA damage under conditions of increased apoptotic priming. Underlying this process, we reveal a key role for mitochondrial dynamics in the regulation of DNA damage an...

Glioblastoma (GBM) is the most prevalent malignant primary brain tumour in adults. GBM typically has a poor prognosis, mainly due to a lack of effective treatment options leading to tumour persistence or recurrence. We investigated the therapeutic potential of targeting anti-apoptotic BCL-2 proteins in GBM. Levels of anti-apoptotic BCL-xL and MCL-1...

Mechanical stress is known to fuel several hallmarks of cancer, ranging from genome instability to uncontrolled proliferation or invasion. Cancer cells are constantly challenged by mechanical stresses not only in the primary tumour but also during metastasis. However, this latter has seldom been studied with regards to mechanobiology, in particular...

Mitochondrial dysfunction is interconnected with cancer. Nevertheless, how defective mitochondria promote cancer is poorly understood. We find that mitochondrial dysfunction promotes DNA damage under conditions of increased apoptotic priming. Underlying this process, we reveal a key role for mitochondrial dynamics in the regulation of DNA damage an...

Mechanical stress is known to fuel several hallmarks of cancer, ranging from genome instability to uncontrolled proliferation or invasion. Cancer cells are constantly challenged by mechanical stresses not only in the primary tumour but also during metastasis. However, this latter has seldom been studied with regards to mechanobiology, in particular...

IDH wild-type glioblastoma (GBM) is the most prevalent malignant primary brain tumour in adults. GBM typically has a poor prognosis, mainly due to a lack of effective treatment options leading to tumour persistence or recurrence. Tackling this, we investigated the therapeutic potential of targeting anti-apoptotic BCL-2 proteins in GBM. Levels of an...

In cancer cells only, TLR3 acquires death receptor properties by efficiently triggering the extrinsic pathway of apoptosis with Caspase-8 as apical protease. Here, we demonstrate that in the absence of Caspase-8, activation of TLR3 can trigger a form of programmed cell death, which is distinct from classical apoptosis. When TLR3 was activated in th...

Mammalian cytosine DNA methylation (5mC) is associated with the integrity of the genome and the transcriptional status of nuclear DNA. Due to technical limitations, it has been less clear if mitochondrial DNA (mtDNA) is methylated and whether 5mC has a regulatory role in this context. Here, we used bisulfite-independent single-molecule sequencing o...

Significance TAT-RasGAP 317–326 can lyse cancer cells in a manner distinct from known programmed cell death pathways through its ability to target specific plasma membrane lipids. The killing properties of this peptide may therefore be difficult for cancer cells to alleviate through resistance-building alterations within known regulated cell death...

Apoptosis, the most extensively studied form of programmed cell death, is essential for organismal homeostasis. Apoptotic cell death has widely been reported as a tumor suppressor mechanism. However, recent studies have shown that apoptosis exerts noncanonical functions and may paradoxically promote tumor growth and metastasis. The hijacking of apo...

We describe here the evaluation of the cytotoxic efficacy of two platinum (II) complexes bearing an N-heterocyclic carbene (NHC) ligand, a pyridine ligand and bromide or iodide ligands on a panel of human metastatic cutaneous melanoma cell lines representing different genetic subsets including BRAF-inhibitor-resistant cell lines, namely A375, SK-ME...

Simple Summary Glioblastoma is a fast-growing and very aggressive brain tumor. Its treatment is usually based on radiation and chemotherapy, which are inefficient owing to glioblastoma stem cells. Indeed, these cells are often resistant to therapy and are a source of tumor regrowth. Therefore, understanding how the survival of glioblastoma stem cel...

Cytosine DNA methylation in the CpG context (5mCpG) is associated with the transcriptional status of nuclear DNA. Due to technical limitations, it has been less clear if mitochondrial DNA (mtDNA) is methylated and whether 5mCpG has a regulatory role in this context. The main aim of this work was to develop and validate a novel tool for determining...

Apoptosis is vital for the correct morphogenesis of multi-cellular organisms. However, like most physiological programs, the cell’s ability to commit suicide is hijacked by cancer in its own proliferative and invasive interest. We recently showed that inefficient execution of apoptosis (or failed apoptosis) is used by cancer to boost invasiveness.

Triggering apoptosis remains an efficient strategy to treat cancer. However, apoptosis is no longer a final destination since cancer cells can undergo partial apoptosis without dying. Recent evidence shows that partial mitochondrial permeabilization and non-lethal caspase activation occur under certain circumstances, although it remains unclear how...

Epigenetic deregulation of gene transcription is central to cancer cell plasticity and malignant progression, but remains poorly understood. We found that the uncharacterized epigenetic factor Chromodomain on Y-like 2 (CDYL2) is commonly over-expressed in breast cancer, and that high CDYL2 levels correlate with poor prognosis. Supporting a function...

Glioblastoma is one of the cancers with the worst prognosis, despite huge efforts to understand its unusual heterogeneity and aggressiveness. These are mainly attributable to glioblastoma stem cells, which are also responsible for the frequent tumour recurrence following surgery or chemo/radiotherapy. We report here that tumorspheres derived from t...

The Sonic Hedgehog (SHH) pathway plays a key role in cancer. Alterations of SHH canonical signaling, causally linked to tumor progression, have become rational targets for cancer therapy. However, Smoothened (SMO) inhibitors have failed to show clinical benefit in patients with cancers displaying SHH autocrine/paracrine expression. We reported earl...

TLR3 converts in cancer cells from an inflammatory to a death receptor and TLR3-induced cell death activates the extrinsic apoptosis pathway. Here, we demonstrate that activation of TLR3 triggers a form lysosomal cell death. Following the combinational treatment of IFN-1/poly(I:C) of the caspase-8 deficient neuroblastoma cell line SH-SY5Y, lysosome...

Triggering apoptosis remains an efficient strategy to treat cancer. However, apoptosis is no longer a final destination, since cells can undergo partial apoptosis without dying. Recent evidence shows that partial mitochondrial permeabilization and non-lethal caspase activation occur under certain circumstances, though it remains unclear how failed...

Background Apoptosis, the most well-known type of programmed cell death, can induce in a paracrine manner a proliferative response in neighboring surviving cells called apoptosis-induced proliferation (AiP). While having obvious benefits when triggered in developmental processes, AiP is a serious obstacle in cancer therapy, where apoptosis is frequ...

The neurotrophin-3 (NT-3) receptor tropomyosin receptor kinase C (TrkC/NTRK3) has been described as a dependence receptor and, as such, triggers apoptosis in the absence of its ligand NT-3. This proapoptotic activity has been proposed to confer a tumor suppressor activity to this classic tyrosine kinase receptor (RTK). By investigating interacting...

Raw data of histograms. (XLSX)

TrkC-KF is translocated to the nucleus by importins and has no intrinsic transcriptional activity per se. (A) SHEP cells transfected with either control plasmid, TrkC-KF-Flag, TrkC-FL, or Neo-IC were fractionated into cytoplasmic (Cytoplasm, marker: GAPDH) and nuclear (Nucleus, marker: histone) fractions. Input corresponds to the construct expressi...

TrkC-KF and Hey1 cooperate to inhibit MDM2 transcription by direct binding on its promoter. (A) Proximity ligation assay (DuoLink) using an anti-MDM2 antibody (recognizing endogenous MDM2) on SHEP cells transfected with TrkC-KF-Flag (anti-Flag antibody) or not transfected (anti-Hey1 antibody targeting endogenous Hey1 and anti-p53 antibody targeting...

Primers and probes used for ChIP. RT-QPCR was performed using the TaqMan technique, requiring the indicated probes (Universal Probe Library, Roche Applied Science). ChIP, chromatin immunoprecipitation; RT-QPCR, quantitative real-time PCR. (XLS)

Hey1 is necessary for TrkC-KF-induced p53 stabilization. (A) Quantification of the western blot presented in (Fig 4A), which has been reproduced and quantified 3 times: Signal of the anti-p53 western blot is compared to anti-Actin signal. Data represent values indexed to control, mean ± SEM (n = 3). *p < 0.05, **p < 0.01. t test. (B) p53 expression...

TrkC-KF associates specifically to the transcription factor Hey1 in the nucleus. (A) Mouse Hey1, Hey2, and HeyL mRNA expression were assessed in N2A cells transfected with an siRNA control or an siRNA targeting Hey1. Data represent values (arbitrary units) relative to HPRT mRNA expression (housekeeping gene). (B) Hey1 expression was assessed by wes...

Hey1 is essential for the cell death mediated by TrkC. (A) TrkA, TrkB, TrkC, NGF, BDNF, and NT-3 mRNA expression was assessed by RT-QPCR on CLB-Ga, LAN6, and SHEP cells relative to HPRT mRNA expression (housekeeping gene). A representative experiment is shown. (B) Immunofluorescence staining using Cy3 performed on LAN6 cells transfected or with the...

Primers and probes used for RT-QPCR. RT-QPCR was performed using the TaqMan technique, requiring the indicated probes (Universal Probe Library, Roche Applied Science). RT-QPCR, quantitative real-time PCR. (XLS)

NB tumors gain a selective advantage when the TrkC apoptotic pathway is silenced. (A, B) TrkC and Hey1 expression in neuroblastic tumors. Dot plots of TrkC (A) and Hey1 (B) mRNA expression values in neuroblastic tumor samples stages 1 to 3 versus stage 4 analyzed using the Agilent microarray 44K (T. Wolf cohort [54], 649 samples, NB1–3 [n = 357], a...

Schematic representation of TrkC proapoptotic pathway. When TrkC is deprived of its ligand, its intracellular domain is double cleaved by caspase, and the released fragment is called TrkC-KF. TrkC-KF is shuttled into the nucleus by importins and interacts there with Hey1 bHLH transcription factor. Hey1 and TrkC-KF bind jointly on MDM2 promoter and...

Caspase-8 is involved in a number of cellular functions, with the most well established being the control of cell death. Yet caspase-8 is unique among the caspases in that it acts as an environmental sensor, transducing a range of signals to cells, modulating responses that extend far beyond simple survival. Ranging from the control of apoptosis an...

Apoptosis represents a key anti-cancer therapeutic effector mechanism. During apoptosis, mitochondrial outer membrane permeabilization (MOMP) typically kills cells even in the absence of caspase activity. Caspase activity can also have a variety of unwanted consequences that include DNA damage. We therefore investigated whether MOMP-induced caspase...

Apoptosis represents a key anti-cancer therapeutic effector mechanism. During apoptosis, mitochondrial outer membrane permeabilization (MOMP) typically kills cells even in the absence of caspase activity. Caspase activity can also have a variety of unwanted consequences that include DNA damage. We therefore investigated whether MOMP-induced caspase...

Mitochondria are not only the 'powerhouse' of the cell; they are also involved in a multitude of processes that include calcium storage, the cell cycle and cell death. Traditional means of investigating mitochondrial importance in a given cellular process have centered upon depletion of mtDNA through chemical or genetic means. Although these method...

Apoptotic cell death is widely considered a positive process that both prevents and treats cancer. Although undoubtedly having a beneficial role, paradoxically, apoptosis can also cause unwanted effects that may even promote cancer. In this Opinion article we highlight some of the ways by which apoptosis can exert oncogenic functions. We argue that...

Most apoptotic cell death events in the body occur via engagement of the mitochondrial pathway of apoptosis. This signaling pathway involves the regulated release, by members of the BCL2 protein family, of mitochondrial proteins following mitochondrial outer membrane permeabilization (MOMP). This in turn activates caspase proteases, generally leadi...

Most apoptotic stimuli require mitochondrial outer membrane permeabilization (MOMP) in order to execute cell death. As such, MOMP is subject to tight control by Bcl-2 family proteins. We have developed a powerful new technique to investigate Bcl-2-mediated regulation of MOMP. This method, called mito-priming, uses co-expression of pro- and anti-apo...

Supplementary Figures 1-6

SVEC cells stably expressing eGFP-tBID 2A BCL-xL were treated with 10μM ABT-737 and analysed for cell viability by SYTOX Green exclusion and IncuCyte cell imaging every 5 minutes for 21 hours.

SVEC cells stably expressing eGFP-tBID 2A BCL-xL were transfected with SMAC-mCherry. Following treatment with 10μM ABT-737, images were acquired on a Nikon A1R confocal instrument every 5 minutes for 1 hour.

SVEC cells stably expressing eGFP-tBID 2A BCL-xL were treated with 10μM ABT-737 and analysed for cell viability by Annexin V staining (purple). Images were acquired on a Nikon A1R confocal instrument every 5 minutes for 1.5 hour.

During apoptosis, the mitochondrial outer membrane is permeabilized, leading to the release of cytochrome c that activates downstream caspases. Mitochondrial outer membrane permeabilization (MOMP) has historically been thought to occur synchronously and completely throughout a cell, leading to rapid caspase activation and apoptosis. Using a new ima...

Apoptosis and necroptosis are 2 major, yet distinct, forms of regulated cell death. Whereas apoptosis requires caspase protease function, necroptosis requires activation of the receptor interacting protein kinases 1 (RIPK1) and RIPK3. Following activation, RIPK3 phosphorylates mixed-lineage kinase domain-like (MLKL), leading to cell death. Apoptosi...

The Bcl-2 proteins Bax and Bak can permeabilize the outer mitochondrial membrane and commit cells to apoptosis. Pro-survival Bcl-2 proteins control Bax by constant retrotranslocation into the cytosol of healthy cells. The stabilization of cytosolic Bax raises the question whether the functionally redundant but largely mitochondrial Bak shares this...

Regulated, programmed cell death is crucial for all multicellular organisms. Cell death is essential in many processes, including tissue sculpting during embryogenesis, development of the immune system and destruction of damaged cells. The best-studied form of programmed cell death is apoptosis, a process that requires activation of caspase proteas...

Programmed necrosis (or necroptosis) is a form of cell death triggered by the activation of receptor interacting protein kinase-3 (RIPK3). Several reports have implicated mitochondria and mitochondrial reactive oxygen species (ROS) generation as effectors of RIPK3-dependent cell death. Here, we directly test this idea by employing a method for the...

The receptor tyrosine kinase Met and its ligand, the hepatocyte growth factor, are essential to embryonic development, whereas the deregulation of Met signaling is associated with tumorigenesis. While ligand-activated Met promotes survival, caspase-dependent generation of the p40 Met fragment leads to apoptosis induction - hallmark of the dependenc...

The neurotrophin receptor TrkC was recently identified as a dependence receptor, and, as such, it triggers apoptosis in the absence of its ligand, NT-3. The molecular mechanism for apoptotic engagement involves the double cleavage of the receptor's intracellular domain, leading to the formation of a proapoptotic "killer" fragment (TrkC KF). Here, w...

Backgrounds & Aims: The TrkC neurotrophin receptor belongs to the functional dependence receptors family, members of which share the ability to induce apoptosis in the absence of their ligands. Such a trait has been hypothesized to confer tumor-suppressor activity. Indeed, cells that express these receptors are thought to be dependent on ligand ava...

Chromosomes are dynamic structures that must be reversibly condensed and unfolded to accommodate mitotic division and chromosome segregation. Histone modifications are involved in the striking chromatin reconfiguration taking place during mitosis. However, the mechanisms that regulate activity and function of histone-modifying factors as cells ente...

The neurotrophin receptor TRKC was initially shown to induce apoptosis in settings of lackof its ligand, NT-3. This cell death was described to be important in the regulation of neuronalsurvival during sympathetic nervous system formation and finally it was linked with severaltypes of cancer. During my thesis I focused on the molecular characteriza...

Tropomyosin-related kinase receptor C (TrkC) is a neurotrophin receptor with tyrosine kinase activity that was expected to be oncogenic. However, it has several characteristics of a tumor suppressor: its expression in tumors has often been associated with good prognosis; and it was recently demonstrated to be a dependence receptor, transducing diff...