Evaluation of Monomer-containing Isocyanate Groups on Stabilizing Demineralized Dentin Matrix Against Bond Interface Degradation.

PURPOSE: To evaluate the effect of urethane methacrylate precursor (UMP) on the enzymatic resistance of demineralized dentin (DD) matrices. MATERIALS AND METHODS: Experimental treatments containing 0 (control), 1, and 5 mmol/L UMP dissolved in an acetone (Ace) solution were formulated. Dentin matrix specimens were demineralized in vitro and immersed in the experimental treatments for 1 h. The treated specimens were then stored in 0.1 mg/mL collagenase solution for 24 h, after which their dry mass loss and hydroxyproline (HYP) release were assessed. The swelling ratios of specimens in each group were also evaluated. The interaction between UMP and the dentin matrix was observed using field-emission scanning electron microscopy (FE-SEM). Endogenous enzyme activity in dentin was evaluated using confocal laser scanning microscopy (CLSM). RESULTS: Compared with the other treatment groups, treatment with 1 mM and 5 mM UMP-Ace significantly decreased the dry mass loss, HYP release and swelling ratio of the DD matrix (p < 0.05). FE-SEM and CLSM observations showed that treatment with UMP-Ace protected the structure of the dentin matrix and decreased porosity within the dentin-collagen network. CONCLUSION: Treatment with 1 mM and 5 mM UMP-Ace protects DD matrix against collagenase degradation and may be clinically useful for improving the durability of the hybrid layer.

Circulating IgG Fragments for Gastric Cancer and Esophageal Cancer.

Blood serum of patients with gastric (n = 68) and esophageal (n = 43) cancer was assessed for proteolytic fragments of IgG. Serum samples of 20 healthy donors were used as a control. We analyzed indicators of hemostasis (prothrombin time, fibrinogen, plasminogen activity, a2-antiplasmin activity, protein C activity) in blood plasma and the level of total IgG in the blood serum. The median IgG-LysK of healthy donors was lower than in esophageal cancer and in patients with gastric cancer. ROC-analysis showed high sensitivity (91%) and specificity (85%) in the group with esophageal cancer but 68% and 85%, respectively, in patients with gastric cancer. Analysis of false negatives IgG-LysK in cancer patients showed that most patients had an advanced stage of cancer accompanied by metastases. Total IgG in the plasma of patients with false-negative IgG-LysK values was 30% lower than in samples with positive values, while the level of a2-antiplasmin was increased and the prothrombin time was shorter. These changes in blood homeostasis may be the reason for an increase in the proportion of false-negative values of the IgG-LysK coefficient. Circulatory IgG-LysK levels increase in the early stages of such cancers as gastric and esophageal cancers. Thus, when used in a panel with other more specific markers for these pathologies, this indicator can significantly increase the early detection of cancer.

Authentic hSAA related with AA amyloidosis: New method of purification, folding and amyloid polymorphism.

The secondary amyloidosis of humans is caused by the formation of hSAA fibrils in different organs and tissues. Until now hSAA was thought to have low amyloidogenicity in vitro and the majority of SAA aggregation experiments were done using murine protein or hSAA non-pathogenic isoforms. In this work a novel purification method for recombinant hSAA was introduced, enabling to obtain monomeric protein capable of amyloid aggregation under physiological conditions. The stability and amyloid aggregation of hSAA have been examined using a wide range of biophysical methods. It was shown that the unfolding of monomeric protein occurs through the formation of molten globule-like intermediate state. Polymorphism of hSAA amyloids was discovered to depend on the solution pH. At pH 8.5, rapid protein aggregation occurs, which leads to the formation of twisted short fibrils. Even a slight decrease of the pH to 7.8 results in delayed aggregation with the formation of long straight amyloids composed of laterally associated protofilaments. Limited proteolysis experiments have shown that full-length hSAA is involved in the formation of intermolecular interactions in both amyloid polymorphs. The results obtained, and the experimental approach used in this study can serve as a basis for further research on the mechanism of authentic hSAA amyloid formation.

New horizons in the mechanisms and therapeutic strategies for PD-L1 protein degradation in cancer.

Programmed death-ligand 1 (PD-L1) has become a crucial focus in cancer immunotherapy considering it is found in many different cells. Cancer cells enhance the suppressive impact of programmed death receptor 1 (PD-1) through elevating PD-L1 expression, which allows them to escape immune detection. Although there have been significant improvements, the effectiveness of anti-PD-1/PD-L1 treatment is still limited to a specific group of patients. An important advancement in cancer immunotherapy involves improving the PD-L1 protein degradation. This review thoroughly examined the processes by which PD-L1 breaks down, including the intracellular pathways of ubiquitination-proteasome and autophagy-lysosome. In addition, the analysis revealed changes that affect PD-L1 stability, such as phosphorylation and glycosylation. The significant consequences of these procedures on cancer immunotherapy and their potential role in innovative therapeutic approaches are emphasised. Our future efforts will focus on understanding new ways in which PD-L1 degradation is controlled and developing innovative treatments, such as proteolysis-targeting chimeras designed specifically to degrade PD-L1. It is crucial to have a thorough comprehension of these pathways in order to improve cancer immunotherapy strategies and hopefully improve therapeutic effectiveness.

O-GlcNAcylated RALY Contributes to Hepatocellular Carcinoma Cells Proliferation by Regulating USP22 mRNA Nuclear Export.

Hepatocellular carcinoma (HCC) is one of the most prevalent and deadly tumors; however, its pathogenic mechanism remains largely elusive. In-depth researches are needed to reveal the expression regulatory mechanisms and functions of the RNA-binding protein RALY in HCC. Here, we identify RALY as a highly expressed oncogenic factor that affects HCC cells proliferation both in vitro and in vivo. O-GlcNAcylation of RALY at Ser176 enhances its stability by protecting RALY from TRIM27-mediated ubiquitination, thus maintaining hyper-expression of the RALY protein. Mechanistically, RALY interacts with USP22 messenger RNA, as revealed by RNA immunoprecipitation, to increase their cytoplasmic localization and protein expression, thereby promoting the proliferation of HCC cells. Furthermore, we develop a novel RALY protein degrader based on peptide proteolysis-targeting chimeras, named RALY-PROTAC, which we chemically synthesize by linking a RALY-targeting peptide with the E3 ubiquitin ligase recruitment ligand pomalidomide. In conclusion, our findings demonstrate a novel mechanism by which O-GlcNAcylation/RALY/USP22 mRNA axis aggravates HCC cells proliferation. RALY-PROTACs as degraders of the RALY protein exhibit potential as therapeutic drugs for RALY-overexpressing HCC.

Proteolytic cleavage of Golgi glycosyltransferases by SPPL3 and other proteases and its implications for cellular glycosylation: (special issue title: New aspects of glycosyltransferases).

Glycosylation of proteins and lipids is of fundamental importance in multicellular eukaryotes. The vast diversity of glycan structures observed is generated in the Golgi apparatus by the concerted activity of >100 distinct enzymes, which include glycosyltransferases and other glycan-modifying enzymes. Well-known for decades, the majority of these enzymes is released from the Golgi apparatus and subsequently secreted into the extracellular space following endoproteolytic cleavage, but the underlying molecular mechanisms and the physiological implications have remained unexplored. This review will summarize our current knowledge of Golgi enzyme proteolysis and secretion and will discuss its conceptual implications for the regulation of cellular glycosylation and the organization of the Golgi apparatus. A particular focus will lie on the intramembrane protease SPPL3, which recently emerged as key protease facilitating Golgi enzyme release and has since been shown to affect a multitude of glycosylation-dependent physiological processes.

Protective Proteolysis in Huntington's Disease: Unraveling the Role of Post-Translational Myristoylation of Huntingtin in Autophagy.

 Huntington's disease (HD) is a devastating neurodegenerative disorder characterized by impaired motor function and cognitive decline, ultimately leading to death. HD is caused by a polyglutamine expansion in the N-terminal region of the huntingtin (HTT) protein, which is linked to decreased HTT turnover, increased HTT proteolysis, increased HTT aggregation, and subsequent neuronal death. In this review, we explore the mechanism of the protective effect of blocking HTT proteolysis at D586, which has been shown to rescue the HD phenotype in HD mouse models. Until recently, the mechanism remained unclear. Herein, we discuss how blocking HTT proteolysis at D586 promotes HTT turnover by correcting autophagy, and making HTT a better autophagy substrate, through post-translational myristoylation of HTT at G553.

Targeting the mSWI/SNF complex in POU2F-POU2AF transcription factor-driven malignancies.

The POU2F3-POU2AF2/3 transcription factor complex is the master regulator of the tuft cell lineage and tuft cell-like small cell lung cancer (SCLC). Here, we identify a specific dependence of the POU2F3 molecular subtype of SCLC (SCLC-P) on the activity of the mammalian switch/sucrose non-fermentable (mSWI/SNF) chromatin remodeling complex. Treatment of SCLC-P cells with a proteolysis targeting chimera (PROTAC) degrader of mSWI/SNF ATPases evicts POU2F3 and its coactivators from chromatin and attenuates downstream signaling. B cell malignancies which are dependent on the POU2F1/2 cofactor, POU2AF1, are also sensitive to mSWI/SNF ATPase degraders, with treatment leading to chromatin eviction of POU2AF1 and IRF4 and decreased IRF4 signaling in multiple myeloma cells. An orally bioavailable mSWI/SNF ATPase degrader significantly inhibits tumor growth in preclinical models of SCLC-P and multiple myeloma without signs of toxicity. This study suggests that POU2F-POU2AF-driven malignancies have an intrinsic dependence on the mSWI/SNF complex, representing a therapeutic vulnerability.

An essential host dietary fatty acid promotes TcpH inhibition of TcpP proteolysis promoting virulence gene expression in Vibrio cholerae.

Vibrio cholerae is a Gram-negative gastrointestinal pathogen responsible for the diarrheal disease cholera. Expression of key virulence factors, cholera toxin and toxin-coregulated pilus, is regulated directly by ToxT and indirectly by two transmembrane transcription regulators (TTRs), ToxR and TcpP, that promote the expression of toxT. TcpP abundance and activity are controlled by TcpH, a single-pass transmembrane protein, which protects TcpP from a two-step proteolytic process known as regulated intramembrane proteolysis (RIP). The mechanism of TcpH-mediated protection of TcpP represents a major gap in our understanding of V. cholerae pathogenesis. The absence of tcpH leads to unimpeded degradation of TcpP in vitro and a colonization defect in a neonate mouse model of V. cholerae colonization. Here, we show that TcpH protects TcpP from RIP via direct interaction. We also demonstrate that α-linolenic acid, a dietary fatty acid, promotes TcpH-dependent inhibition of RIP via co-association of TcpP and TcpH molecules within detergent-resistant membranes (DRMs) in a mechanism requiring the TcpH transmembrane domain. Taken together, our data support a model where V. cholerae cells use exogenous α-linolenic acid to remodel the phospholipid bilayer in vivo, leading to co-association of TcpP and TcpH within DRMs where RIP of TcpP is inhibited by TcpH, thereby promoting V. cholerae pathogenicity. IMPORTANCE: Vibrio cholerae continues to pose a significant global burden on health and an alternative therapeutic approach is needed, due to evolving multidrug resistance strains. Transcription of toxT, stimulated by TcpP and ToxR, is essential for V. cholerae pathogenesis. Our results show that TcpP, one of the major regulators of toxT gene expression, is protected from proteolysis by TcpH, via direct interaction. Furthermore, we identified a gut metabolite, α-linolenic acid, that stimulates the co-association of TcpP and TcpH within detergent-resistant membranes (also known as lipid-ordered membrane domains), thereby supporting TcpH-dependent antagonism of TcpP proteolysis. Data presented here extend our knowledge of RIP, virulence gene regulation in V. cholerae, and, to the best of our knowledge, provides the first evidence that lipid-ordered membranes exist within V. cholerae. The model presented here also suggests that TTRs, common among bacteria and archaea, and co-component signal transduction systems present in Enterobacteria, could also be influenced similarly.

Charting the importance of filamin A posttranslational modifications.

Filamin A is an essential protein in the cell cytoskeleton because of its actin binding properties and unique homodimer rod-shaped structure, which organises actin into three-dimensional orthogonal networks imperative to cell motility, spreading and adhesion. Filamin A is subject to extensive posttranslational modification (PTM) which serves to co-ordinate cellular architecture and to modulate its large protein-protein interaction network which is key to the protein's role as a cellular signalling hub. Characterised PTMs include phosphorylation, irreversible cleavage, ubiquitin mediated degradation, hydroxylation and O-GlcNAcylation, with preliminary evidence of tyrosylation, carbonylation and acetylation. Each modification and its relation to filamin A function will be described here. These modifications are often aberrantly applied in a range of diseases including, but not limited to, cancer, cardiovascular disease and neurological disease and we discuss the concept of target specific PTMs with novel therapeutic modalities. In summary, our review represents a topical 'one-stop-shop' that enables understanding of filamin A function in cell homeostasis and provides insight into how a variety of modifications add an extra level of Filamin A control.

Progress of proteolysis-targeting chimeras (PROTACs) delivery system in tumor treatment.

Proteolysis targeting chimeras (PROTACs) can use the intrinsic protein degradation system in cells to degrade pathogenic target proteins, and are currently a revolutionary frontier of development strategy for tumor treatment with small molecules. However, the poor water solubility, low cellular permeability, and off-target side effects of most PROTACs have prevented them from passing the preclinical research stage of drug development. This requires the use of appropriate delivery systems to overcome these challenging hurdles and ensure precise delivery of PROTACs towards the tumor site. Therefore, the combination of PROTACs and multifunctional delivery systems will open up new research directions for targeted degradation of tumor proteins. In this review, we systematically reviewed the design principles and the most recent advances of various PROTACs delivery systems. Moreover, the constructive strategies for developing multifunctional PROTACs delivery systems were proposed comprehensively. This review aims to deepen the understanding of PROTACs drugs and promote the further development of PROTACs delivery system.

Thermostability-assisted limited proteolysis-coupled mass spectrometry for capturing drug target proteins and sites.

BACKGROUND: Identifying drug-binding targets and their corresponding sites is crucial for drug discovery and mechanism studies. Limited proteolysis-coupled mass spectrometry (LiP-MS) is a sophisticated method used for the detection of compound and protein interactions. However, in some cases, LiP-MS cannot identify the target proteins due to the small structure changes or the lack of enrichment of low-abundant protein. To overcome this drawback, we developed a thermostability-assisted limited proteolysis-coupled mass spectrometry (TALiP-MS) approach for efficient drug target discovery. RESULTS: We proved that the novel strategy, TALiP-MS, could efficiently identify target proteins of various ligands, including cyclosporin A (a calcineurin inhibitor), geldanamycin (an HSP90 inhibitor), and staurosporine (a kinase inhibitor), with accurately recognizing drug-binding domains. The TALiP protocol increased the number of target peptides detected in LiP-MS experiments by 2- to 8-fold. Meanwhile, the TALiP-MS approach can not only identify both ligand-binding stability and destabilization proteins but also shows high complementarity with the thermal proteome profiling (TPP) and machine learning-based limited proteolysis (LiP-Quant) methods. The developed TALiP-MS approach was applied to identify the target proteins of celastrol (CEL), a natural product known for its strong antioxidant and anti-cancer angiogenesis effect. Among them, four proteins, MTHFD1, UBA1, ACLY, and SND1 were further validated for their strong affinity to CEL by using cellular thermal shift assay. Additionally, the destabilized proteins induced by CEL such as TAGLN2 and CFL1 were also validated. SIGNIFICANCE: Collectively, these findings underscore the efficacy of the TALiP-MS method for identifying drug targets, elucidating binding sites, and even detecting drug-induced conformational changes in target proteins in complex proteomes.

CDK9 targeting PROTAC L055 inhibits ERα-positive breast cancer.

Breast cancer is one of the most prevalent malignancies affecting women worldwide, underscoring the urgent need for more effective and specific treatments. Proteolysis-targeting chimeras (PROTACs) have emerged as a promising strategy to develop new lead compounds by selectively targeting oncoproteins for degradation. In this study, we designed, synthesized and evaluated a CRBN-based PROTAC, L055, which targets CDK9. Our findings demonstrate that L055 effectively inhibits the proliferation, induces cell cycle arrest, and decreases the survival of ERα-positive breast cancer cells in vitro. L055 specifically binds to CDK9, facilitating its degradation via the CRBN-dependent proteasomal pathway. Additionally, L055 suppressed the growth of organoids and tumors derived from T47D and MCF7 cells in nude mice. Thus, L055 represents a potential novel therapeutic agent for ERα-positive breast cancer and potentially other malignancies.

Cyclosporin A-Based PROTACs Can Deplete Abundant Cellular Cyclophilin A without Suppressing T Cell Activation.

Cyclophilin A (CypA), the cellular receptor of the immunosuppressant cyclosporin A (CsA), is an abundant cytosolic protein and is involved in a variety of diseases. For example, CypA supports cancer proliferation and mediates viral infections, such as the human immunodeficiency virus 1 (HIV-1). Here, we present the design of PROTAC (proteolysis targeting chimera) compounds against CypA to induce its intracellular proteolysis and to investigate their effect on immune cells. Interestingly, upon connecting to E3 ligase ligands, both peptide-based low-affinity binders and CsA-based high-affinity binders can degrade CypA at nM concentration in HeLa cells and fibroblast cells. As the immunosuppressive effect of CsA is not directly associated with the binding of CsA to CypA but the inhibition of phosphatase calcineurin by the CypA:CsA complex, we investigated whether a CsA-based PROTAC compound could induce CypA degradation without affecting the activation of immune cells. P3, the most efficient PROTAC compound discovered from this study, could deplete CypA in lymphocytes without affecting cell proliferation and cytokine production. This work demonstrates the feasibility of the PROTAC approach in depleting the abundant cellular protein CypA at low drug dosage without affecting immune cells, allowing us to investigate the potential therapeutic effects associated with the endogenous protein in the future.

Improving transient protein expression in agroinfiltrated Nicotiana benthamiana.

Agroinfiltration of Nicotiana benthamiana is routinely used in plant science and molecular pharming to transiently express proteins of interest. Here, we discuss four phenomena that should be avoided to improve transient expression. Immune responses can be avoided by depleting immune receptors and employing pathogen-derived effectors; transcript degradation by using silencing inhibitors or RNA interference machinery mutants; endoplasmic reticulum stress by co-expressing chaperones; and protein degradation can be avoided with subcellular targeting, protease mutants and co-expressing protease inhibitors. We summarise the reported increased yields for various recombinant proteins achieved with these approaches and highlight remaining challenges to further improve the efficiency of this versatile protein expression platform.

The emerging role of targeted protein degradation to treat and study cancer.

The evolution of cancer treatment has provided increasingly targeted strategies both in the upfront and relapsed disease settings. Small-molecule inhibitors and immunotherapy have risen to prominence with chimeric antigen receptor T-cells, checkpoint inhibitors, kinase inhibitors, and monoclonal antibody therapies being deployed across a range of solid organ and haematological malignancies. However, novel approaches are required to target transcription factors and oncogenic fusion proteins that are central to cancer biology and have generally eluded successful drug development. Thalidomide analogues causing protein degradation have been a cornerstone of treatment in multiple myeloma, but a lack of in-depth mechanistic understanding initially limited progress in the field. When the protein cereblon (CRBN) was found to mediate thalidomide analogues' action and CRBN's neo-targets were identified, existing and novel drug development accelerated, with applications outside multiple myeloma, including non-Hodgkin's lymphoma, myelodysplastic syndrome, and acute leukaemias. Critically, transcription factors were the first canonical targets described. In addition to broadening the application of protein-degrading drugs, resistance mechanisms are being overcome and targeted protein degradation is widening the scope of druggable proteins against which existing approaches have been ineffective. Examples of targeted protein degraders include molecular glues and proteolysis targeting chimeras (PROTACs): heterobifunctional molecules that bind to proteins of interest and cause proximity-induced ubiquitination and proteasomal degradation via a linked E3 ligase. Twenty years since their inception, PROTACs have begun progressing through clinical trials, with early success in targeting the oestrogen receptor and androgen receptor in breast and prostate cancer respectively. This review explores important developments in targeted protein degradation to both treat and study cancer. It also considers the potential advantages and challenges in the translational aspects of developing new treatments. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Assessing the functional roles of coevolving PHD finger residues.

Although in silico folding based on coevolving residue constraints in the deep-learning era has transformed protein structure prediction, the contributions of coevolving residues to protein folding, stability, and other functions in physical contexts remain to be clarified and experimentally validated. Herein, the PHD finger module, a well-known histone reader with distinct subtypes containing subtype-specific coevolving residues, was used as a model to experimentally assess the contributions of coevolving residues and to clarify their specific roles. The results of the assessment, including proteolysis and thermal unfolding of wildtype and mutant proteins, suggested that coevolving residues have varying contributions, despite their large in silico constraints. Residue positions with large constraints were found to contribute to stability in one subtype but not others. Computational sequence design and generative model-based energy estimates of individual structures were also implemented to complement the experimental assessment. Sequence design and energy estimates distinguish coevolving residues that contribute to folding from those that do not. The results of proteolytic analysis of mutations at positions contributing to folding were consistent with those suggested by sequence design and energy estimation. Thus, we report a comprehensive assessment of the contributions of coevolving residues, as well as a strategy based on a combination of approaches that should enable detailed understanding of the residue contributions in other large protein families.

Fluoxetine and ketamine trigger the p75NTR proteolytic pathway and enhance extinction memory and brain plasticity through p75NTR.

BACKGROUND: Diverse antidepressants were recently described to bind to TrkB and drive a positive allosteric modulation of endogenous BDNF. Although neurotrophins such as BDNF can bind to the p75 neurotrophin receptor (p75NTR), their precursors are the high affinity p75NTR ligands. While part of an unrelated receptor family capable of inducing completely opposite physiological changes, TrkB and p75NTR feature a cross-like conformation dimer and carry a cholesterol-recognition and alignment consensus in the transmembrane domain. Since such qualities were found crucial for antidepressants to bind to TrkB and drive behavioral and neuroplasticity effects, we hypothesized that their effects might also depend on p75NTR. METHODS: ELISA-based binding assay and NMR spectroscopy were accomplished to assess whether antidepressants would bind to p75NTR. HEK293T cells and a variety of in vitro assays were used to address whether fluoxetine (FLX) or ketamine (KET) would trigger any α- and γ-secretase-dependent p75NTR proteolysis, and lead to p75NTR nuclear localization. Ocular dominance shift was performed with male and female p75KO mice to study the effects of KET and FLX on brain plasticity, in addition to pharmacological interventions to verifying how p75NTR signaling is important for the effects of KET and FLX in enhancing extinction memory in male WT mice and rats. RESULTS: Antidepressants were found binding to p75NTR, FLX and KET triggered the p75NTR proteolytic pathway and induced p75NTR-dependent behavioral/neuroplasticity changes. CONCLUSION: We thus hypothesize that antidepressants co-opt both BDNF/TrkB and proBDNF/p75NTR systems to induce a more efficient activity-dependent synaptic competition, thereby boosting the brain ability for remodeling.

Mono- and Bi-specific Nanobodies Targeting the CUB Domains of PCPE-1 Reduce the Proteolytic Processing of Fibrillar Procollagens.

The excessive deposition of fibrillar collagens is a hallmark of fibrosis. Collagen fibril formation requires proteolytic maturations by Procollagen N- and C-proteinases (PNPs and PCPs) to remove the N- and C-propeptides which maintain procollagens in the soluble form. Procollagen C-Proteinase Enhancer-1 (PCPE-1, a glycoprotein composed of two CUB domains and one NTR domain) is a regulatory protein that activates the C-terminal processing of procollagens by the main PCPs. It is often up-regulated in fibrotic diseases and represents a promising target for the development of novel anti-fibrotic strategies. Here, our objective was to develop the first antagonists of PCPE-1, based on the nanobody scaffold. Using both an in vivo selection through the immunization of a llama and an in vitro selection with a synthetic library, we generated 18 nanobodies directed against the CUB domains of PCPE1, which carry its enhancing activity. Among them, I5 from the immune library and H4 from the synthetic library have a high affinity for PCPE-1 and inhibit its interaction with procollagens. The crystal structure of the complex formed by PCPE-1, H4 and I5 showed that they have distinct epitopes and enabled the design of a biparatopic fusion, the diabody diab-D1. Diab-D1 has a sub-nanomolar affinity for PCPE-1 and is a potent antagonist of its activity, preventing the stimulation of procollagen cleavage in vitro. Moreover, Diab-D1 is also effective in reducing the proteolytic maturation of procollagen I in cultures of human dermal fibroblasts and hence holds great promise as a tool to modulate collagen deposition in fibrotic conditions.

PROteolysis-Targeting Chimeras (PROTACs) in leukemia: overview and future perspectives.

Leukemia is a heterogeneous group of life-threatening malignant disorders of the hematopoietic system. Immunotherapy, radiotherapy, stem cell transplantation, targeted therapy, and chemotherapy are among the approved leukemia treatments. Unfortunately, therapeutic resistance, side effects, relapses, and long-term sequelae occur in a significant proportion of patients and severely compromise the treatment efficacy. The development of novel approaches to improve outcomes is therefore an unmet need. Recently, novel leukemia drug discovery strategies, including targeted protein degradation, have shown potential to advance the field of personalized medicine for leukemia patients. Specifically, PROteolysis-TArgeting Chimeras (PROTACs) are revolutionary compounds that allow the selective degradation of a protein by the ubiquitin-proteasome system. Developed against a wide range of cancer targets, they show promising potential in overcoming many of the drawbacks associated with conventional therapies. Following the exponential growth of antileukemic PROTACs, this article reviews PROTAC-mediated degradation of leukemia-associated targets. Chemical structures, in vitro and in vivo activities, pharmacokinetics, pharmacodynamics, and clinical trials of PROTACs are critically discussed. Furthermore, advantages, challenges, and future perspectives of PROTACs in leukemia are covered, in order to understand the potential that these novel compounds may have as future drugs for leukemia treatment.