Targeting Phosphatidylserine with Calcium-Dependent Protein-Drug Conjugates for the Treatment of Cancer

Gla-domain mediated targeting of externalized phosphatidylserine for intracellular delivery

Phosphatidylserine (PS) is a negatively charged phospholipid normally localized to the inner leaflet of the plasma membrane of cells but is externalized onto the cell surface during apoptosis as well as in malignant and infected cells. Consequently, PS may comprise an important molecular target in diagnostics, imaging, and targeted delivery of therapeutic agents. While an array of PS-binding molecules exist, their utility has been limited by their inability to internalize diagnostic or therapeutic payloads. We describe the generation, isolation, characterization, and utility of a PS-binding motif comprised of a carboxylated glutamic acid (GLA) residue domain that both recognizes and binds cell surface-exposed PS, and then unlike other PS-binding molecules is internalized into these cells. Internalization is independent of the traditional endosomal-lysosomal pathway, directly entering the cytosol of the target cell rapidly. We demonstrate that this PS recognition extends to stem cells and that GLA-domain-conjugated probes can be detected upon intravenous administration in animal models of infectious disease and cancer. GLA domain binding and internalization offer new opportunities for specifically targeting cells with surface-exposed PS for imaging and delivery of therapeutics.

Fundamental concepts of protein therapeutics and spacing in oncology: an updated comprehensive review

Current treatment regimens in cancer cases cause significant side effects and cannot effectively eradicate the advanced disease. Hence, much effort has been expended over the past years to understand how cancer grows and responds to therapies. Meanwhile, proteins as a type of biopolymers have been under commercial development for over three decades and have been proven to improve the healthcare system as effective medicines for treating many types of progressive disease, such as cancer. Following approving the first recombinant protein therapeutics by FDA (Humulin), there have been a revolution for drawing attention toward protein-based therapeutics (PTs). Since then, the ability to tailor proteins with ideal pharmacokinetics has provided the pharmaceutical industry with an important noble path to discuss the clinical potential of proteins in oncology research. Unlike traditional chemotherapy molecules, PTs actively target cancerous cells by binding to their surface receptors and the other biomarkers particularly associated with tumorous or healthy tissue. This review analyzes the potential and limitations of protein therapeutics (PTs) in the treatment of cancer as well as highlighting the evolving strategies by addressing all possible factors, including pharmacology profile and targeted therapy approaches. This review provides a comprehensive overview of the current state of PTs in oncology, including their pharmacology profile, targeted therapy approaches, and prospects. The reviewed data show that several current and future challenges remain to make PTs a promising and effective anticancer drug, such as safety, immunogenicity, protein stability/degradation, and protein-adjuvant interactions.

Comprehensive classification of proteins based on structures that engage lipids by COMPOSEL

Structures can now be predicted for any protein using programs like AlphaFold and Rosetta, which rely on a foundation of experimentally determined structures of architecturally diverse proteins. The accuracy of such artificial intelligence and machine learning (AI/ML) approaches benefits from the specification of restraints which assist in navigating the universe of folds to converge on models most representative of a given protein's physiological structure. This is especially pertinent for membrane proteins, with structures and functions that depend on their presence in lipid bilayers. Structures of proteins in their membrane environments could conceivably be predicted from AI/ML approaches with user-specificized parameters that describe each element of the architecture of a membrane protein accompanied by its lipid environment. We propose the Classification Of Membrane Proteins based On Structures Engaging Lipids (COMPOSEL), which builds on existing nomenclature types for monotopic, bitopic, polytopic and peripheral membrane proteins as well as lipids. Functional and regulatory elements are also defined in the scripts, as shown with membrane fusing synaptotagmins, multidomain PDZD8 and Protrudin proteins that recognize phosphoinositide (PI) lipids, the intrinsically disordered MARCKS protein, caveolins, the β barrel assembly machine (BAM), an adhesion G-protein coupled receptor (aGPCR) and two lipid modifying enzymes - diacylglycerol kinase DGKε and fatty aldehyde dehydrogenase FALDH. This demonstrates how COMPOSEL communicates lipid interactivity as well as signaling mechanisms and binding of metabolites, drug molecules, polypeptides or nucleic acids to describe the operations of any protein. Moreover COMPOSEL can be scaled to express how genomes encode membrane structures and how our organs are infiltrated by pathogens such as SARS-CoV-2.

Targeting the Phosphatidylserine-Immune Checkpoint with a Small-Molecule Maytansinoid Conjugate

Ligand-targeting drug delivery systems have made significant strides for disease treatments with numerous clinical approvals in this era of precision medicine. Herein, we report a class of small molecule-based immune checkpoint-targeting maytansinoid conjugates. From the ligand targeting ability, pharmacokinetics profiling, in vivo anti-pancreatic cancer, triple-negative breast cancer, and sorafenib-resistant liver cancer efficacies with quantitative mRNA analysis of treated-tumor tissues, we demonstrated that conjugate 40a not only induced lasting regression of tumor growth, but it also rejuvenated the once immunosuppressive tumor microenvironment to an “inflamed hot tumor” with significant elevation of gene expressions that were not accessible in the vehicle-treated tumor. In turn, the immune checkpoint-targeting small molecule drug conjugate from this work represents a new pharmacodelivery strategy that can be expanded with combination therapy with existing immune-oncology treatment options.

Nanoalbumin-prodrug conjugates prepared via a thiolation-and-conjugation method improve cancer chemotherapy and immune checkpoint blockade therapy by promoting CD8+ T-cell infiltration

Protein-drug conjugates are emerging tools to combat cancers. Here, we adopted an indirect thiolation-and-conjugation method as a general strategy to prepare protein-drug conjugates. We found for the first time that this method led to the formation of nanometric conjugates, probably due to the formation of intermolecular disulfide bonds, which facilitated enhanced uptake by cancer cells. As a proof-of-concept application in cancer therapy, a nanometric albumin-doxorubicin prodrug conjugate (NanoAlb-proDOX) was prepared. The nanometric size promoted its uptake by cancer cells, and the prodrug characteristic defined its selective cytotoxicity toward cancer cells in vitro and reduced side effects in vivo. In multiple tumor xenograft models, nanometric NanoAlb-proDOX showed superior antitumor activity and synergy with immune checkpoint blockade, probably due to the synergistically enhanced tumor CD8⁺ T-cell infiltration and activation. Hence, the thiolation-and-conjugation strategy may serve as a generally applicable method for preparing drug conjugates, and the proof-of-concept nanometric albumin-doxorubicin conjugate may be a good choice for antitumor therapy with the ability to co-stimulate the efficacy of immune checkpoint blockade.

Phospholipid Scramblases: Role in Cancer Progression and Anticancer Therapeutics

Phospholipid scramblases (PLSCRs) that catalyze rapid mixing of plasma membrane lipids result in surface exposure of phosphatidyl serine (PS), a lipid normally residing to the inner plasma membrane leaflet. PS exposure provides a chemotactic eat-me signal for phagocytes resulting in non-inflammatory clearance of apoptotic cells by efferocytosis. However, metastatic tumor cells escape efferocytosis through alteration of tumor microenvironment and apoptotic signaling. Tumor cells exhibit altered membrane features, high constitutive PS exposure, low drug permeability and increased multidrug resistance through clonal evolution. PLSCRs are transcriptionally up-regulated in tumor cells leading to plasma membrane remodeling and aberrant PS exposure on cell surface. In addition, PLSCRs interact with multiple cellular components to modulate cancer progression and survival. While PLSCRs and PS exposed on tumor cells are novel drug targets, many exogenous molecules that catalyze lipid scrambling on tumor plasma membrane are potent anticancer therapeutic molecules. In this review, we provide a comprehensive analysis of scramblase mediated signaling events, membrane alteration specific to tumor development and possible therapeutic implications of scramblases and PS exposure.

Identification of Core Genes and Screening of Potential Targets in Glioblastoma Multiforme by Integrated Bioinformatic Analysis

Glioblastoma multiforme is the most common primary intracranial malignancy, but its etiology and pathogenesis are still unclear. With the deepening of human genome research, the research of glioma subtype screening based on core molecules has become more in-depth. In the present study, we screened out differentially expressed genes (DEGs) through reanalyzing the glioblastoma multiforme (GBM) datasets GSE90598 from the Gene Expression Omnibus (GEO), the GBM dataset TCGA-GBM and the low-grade glioma (LGG) dataset TCGA-LGG from the Cancer Genome Atlas (TCGA). A total of 150 intersecting DEGs were found, of which 48 were upregulated and 102 were downregulated. These DEGs from GSE90598 dataset were enriched using the overrepresentation method, and multiple enriched gene ontology (GO) function terms were significantly correlated with neural cell signal transduction. DEGs between GBM and LGG were analyzed by gene set enrichment analysis (GSEA), and the significantly enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways involved in synapse signaling and oxytocin signaling pathways. Then, a protein-protein interaction (PPI) network was constructed to assess the interaction of proteins encoded by the DEGs. MCODE identified 2 modules from the PPI network. The 11 genes with the highest degrees in module 1 were designated as core molecules, namely, GABRD, KCNC1, KCNA1, SYT1, CACNG3, OPALIN, CD163, HPCAL4, ANK3, KIF5A, and MS4A6A, which were mainly enriched in ionic signaling-related pathways. Survival analysis of the GSE83300 dataset verified the significant relationship between expression levels of the 11 core genes and survival. Finally, the core molecules of GBM and the DrugBank database were assessed by a hypergeometric test to identify 10 drugs included tetrachlorodecaoxide related to cancer and neuropsychiatric diseases. Further studies are required to explore these core genes for their potentiality in diagnosis, prognosis, and targeted therapy and explain the relationship among ionic signaling-related pathways, neuropsychiatric diseases and neurological tumors.

Selective Depletion of Antigen-Specific Antibodies for the Treatment of Demyelinating Disease

Current treatments for antibody-mediated autoimmunity are associated with lack of specificity, leading to immunosuppressive effects. To overcome this limitation, we have developed a class of antibody-based therapeutics for the treatment of autoimmunity involving antibodies that recognize the autoantigen, myelin oligodendrocyte glycoprotein (MOG). These agents ("Seldegs," for selective degradation) selectively eliminate antigen (MOG)-specific antibodies without affecting the levels of antibodies of other specificities. Seldeg treatment of mice during antibody-mediated exacerbation of experimental autoimmune encephalomyelitis by patient-derived MOG-specific antibodies results in disease amelioration. Consistent with their therapeutic effects, Seldegs deliver their targeted antibodies to Kupffer and liver sinusoidal endothelial cells that are known to have tolerogenic effects. Our results show that Seldegs can ameliorate disease mediated by MOG-specific antibodies and indicate that this approach also has the potential to treat other autoimmune diseases where the specific clearance of antibodies is required.

BPRDP056, a novel small molecule drug conjugate specifically targeting phosphatidylserine for cancer therapy

Zinc(II)-dipicolylamine (Zn-DPA) has been shown to specifically identify and bind to phosphatidylserine (PS), which exists in bulk in the tumor microenvironment. BPRDP056, a Zn-DPA-SN38 conjugate was designed to provide PS-targeted drug delivery of a cytotoxic SN38 to the tumor microenvironment, thereby allowing a lower dosage of SN38 that induces apoptosis in cancer cells. Micro-Western assay showed that BPRDP056 exhibited apoptotic signal levels similar to those of CPT-11 in the treated tumors growing in mice. Pharmacokinetic study showed that BPRDP056 has excellent systemic stability in circulation in mice and rats. BPRDP056 is accumulated in tumors and thus increases the cytotoxic effects of SN38. The in vivo antitumor activities of BPRDP056 have been shown to be significant in subcutaneous pancreas, prostate, colon, liver, breast, and glioblastoma tumors, included an orthotopic pancreatic tumor, in mice. BPRDP056 shrunk tumors at a lower (~20% only) dosing intensity of SN38 compared to that of SN38 conjugated in CPT-11 in all tumor models tested. A wide spectrum of antitumor activities is expected to treat all cancer types of PS-rich tumor microenvironments. BPRDP056 is a first-in-class small molecule drug conjugate for cancer therapy.

Targeting phosphatidylserine for Cancer therapy: prospects and challenges

Cancer is a leading cause of mortality and morbidity worldwide. Despite major improvements in current therapeutic methods, ideal therapeutic strategies for improved tumor elimination are still lacking. Recently, immunotherapy has attracted much attention, and many immune-active agents have been approved for clinical use alone or in combination with other cancer drugs. However, some patients have a poor response to these agents. New agents and strategies are needed to overcome such deficiencies. Phosphatidylserine (PS) is an essential component of bilayer cell membranes and is normally present in the inner leaflet. In the physiological state, PS exposure on the external leaflet not only acts as an engulfment signal for phagocytosis in apoptotic cells but also participates in blood coagulation, myoblast fusion and immune regulation in nonapoptotic cells. In the tumor microenvironment, PS exposure is significantly increased on the surface of tumor cells or tumor cell-derived microvesicles, which have innate immunosuppressive properties and facilitate tumor growth and metastasis. To date, agents targeting PS have been developed, some of which are under investigation in clinical trials as combination drugs for various cancers. However, controversial results are emerging in laboratory research as well as in clinical trials, and the efficiency of PS-targeting agents remains uncertain. In this review, we summarize recent progress in our understanding of the physiological and pathological roles of PS, with a focus on immune suppressive features. In addition, we discuss current drug developments that are based on PS-targeting strategies in both experimental and clinical studies. We hope to provide a future research direction for the development of new agents for cancer therapy.

Molecular determinants as therapeutic targets in cancer chemotherapy: An update

It is well known that cancer cells are heterogeneous in nature and very distinct from their normal counterparts. Commonly these cancer cells possess different and complementary metabolic profile, microenvironment and adopting behaviors to generate more ATPs to fulfill the requirement of high energy that is further utilized in the production of proteins and other essentials required for cell survival, growth, and proliferation. These differences create many challenges in cancer treatments. On the contrary, such situations of metabolic differences between cancer and normal cells may be expected a promising strategy for treatment purpose. In this article, we focus on the molecular determinants of oncogene-specific sub-organelles such as potential metabolites of mitochondria (reactive oxygen species, apoptotic proteins, cytochrome c, caspase 9, caspase 3, etc.), endoplasmic reticulum (unfolded protein response, PKR-like ER kinase, C/EBP homologous protein, etc.), nucleus (nucleolar phosphoprotein, nuclear pore complex, nuclear localization signal), lysosome (microenvironment, etc.) and plasma membrane phospholipids, etc. that might be exploited for the targeted delivery of anti-cancer drugs for therapeutic benefits. This review will help to understand the various targets of subcellular organelles at molecular levels. In the future, this molecular level understanding may be combined with the genomic profile of cancer for the development of the molecularly guided or personalized therapeutics for complete eradication of cancer.

Engineering a HER2-specific antibody-drug conjugate to increase lysosomal delivery and therapeutic efficacy

We improve the potency of antibody-drug conjugates (ADCs) containing the HER2-specific antibody pertuzumab by reducing their affinity for HER2 by >250-fold at acidic endosomal pH relative to near neutral pH. These engineered pertuzumab variants show increased lysosomal delivery and cytotoxicity towards tumor cells expressing intermediate HER2 levels. In HER2^int xenograft tumor models in mice, the variants show higher therapeutic efficacy than the parent ADC and a clinically-approved HER2-specific ADC.