Mis-trafficking of endosomal urokinase proteins triggers drug-induced glioma nonapoptotic cell death

Combined Antitumor Effect of the Serine Protease Urokinase Inhibitor Upamostat and the Sphingosine Kinase 2 Inhibitor Opaganib on Cholangiocarcinoma Patient-Derived Xenografts

Upamostat is an orally available small-molecule serine protease inhibitor that is a highly potent inhibitor of trypsin 1, trypsin 2, trypsin 3 (PRSS1/2/3), and the urokinase-type plasminogen activator (uPA). These enzymes are expressed in many cancers, especially during tissue remodeling and subsequent tumor cell invasion. Opaganib (ABC294640), a novel, orally available small molecule is a selective inhibitor of the phosphorylation of sphingosine to sphingosine-1-phosphate (S-1-P) by sphingosine kinase 2 (SPHK2). Both sphingosine kinase 1 (SPHK1) and SPHK2 are known to regulate the proliferation-inducing compound S-1-P. However, SPHK2 is more critical in cancer pathogenesis. The goal of this project was to investigate the potential antitumor effects of upamostat and opaganib, individually and in combination, on cholangiocarcinoma (CCA) xenografts in nude mice. PAX165, a patient-derived xenograft (PDX) from a surgically resected CCA, expresses substantial levels of SPHK2, PRSS1, PRSS2, and PRSS3. Four groups of 18 mice each were treated with upamostat, opaganib, both, or vehicle. Mouse weights and PAX165 tumor volumes were measured. Tumor volumes in the upamostat, opaganib, and upamostat plus opaganib groups were significantly decreased compared to the control group.

Cmpd10357 to treat B-cell acute lymphoblastic leukemia

B-cell acute lymphoblastic leukemia (B-ALL) is the most common type of cancer found in children. Although the overall survival rates are now >80%, 15%-20% of pediatric patients relapse, with survival rates subsequently dropping to 5%-10%. Cmpd10357, 3-amino-5-arylamino-6-chloro-N- (diaminomethylene) pyrazine-2-carboximide, is a highly potent, cell-permeant compound recently shown to have cytotoxic effects on solid tumors, including human breast cancer and high-grade gliomas, independent of their proliferative status. Cmpd10357 demonstrated concentration-dependent cytotoxicity in two human B-ALL cell lines, JM1 and Reh, at half-maximal inhibitory concentrations (IC₅₀) of 3.2 and 3.3 μM, respectively. Cmpd10357, at a dose of 5 mg/kg, significantly prolonged survival in our B-ALL xenograft mouse model, with a median survival time of 49.0 days compared with 45.5 days in the control group (p < 0.05). The cytotoxicity of Cmpd10357 demonstrated caspase-independent, nonapoptotic cancer cell demise associated with the nuclear translocation of apoptosis-inducing factor (AIF). The cytotoxicity of Cmpd10357 in B-ALL cells was inhibited by Necrostatin-1 but not by Necrosulfonamide. These studies suggest that an AIF-mediated, caspase-independent necrosis mechanism of Cmpd10357 in B-ALL could be used in combination with traditional apoptotic chemotherapeutic agents.

Therapeutic Strategies Targeting Urokinase and Its Receptor in Cancer

Several studies have ascertained that uPA and uPAR do participate in tumor progression and metastasis and are involved in cell adhesion, migration, invasion and survival, as well as angiogenesis. Increased levels of uPA and uPAR in tumor tissues, stroma and biological fluids correlate with adverse clinic-pathologic features and poor patient outcomes. After binding to uPAR, uPA activates plasminogen to plasmin, a broad-spectrum matrix- and fibrin-degrading enzyme able to facilitate tumor cell invasion and dissemination to distant sites. Moreover, uPAR activated by uPA regulates most cancer cell activities by interacting with a broad range of cell membrane receptors. These findings make uPA and uPAR not only promising diagnostic and prognostic markers but also attractive targets for developing anticancer therapies. In this review, we debate the uPA/uPAR structure-function relationship as well as give an update on the molecules that interfere with or inhibit uPA/uPAR functions. Additionally, the possible clinical development of these compounds is discussed.

Immunotargeting of Nanocrystals by SpyCatcher Conjugation of Engineered Antibodies

Inorganic nanocrystals such as quantum dots (QDs) and upconverting nanoparticles (UCNPs) are uniquely suited for quantitative live-cell imaging and are typically functionalized with ligands to study specific receptors or cellular targets. Antibodies (Ab) are among the most useful targeting reagents owing to their high affinities and specificities, but common nanocrystal labeling methods may orient Ab incorrectly, be reversible or denaturing, or lead to Ab-NP complexes too large for some applications. Here, we show that SpyCatcher proteins, which bind and spontaneously form covalent isopeptide bonds with cognate SpyTag peptides, can conjugate engineered Ab to nanoparticle surfaces with control over stability, orientation, and stoichiometry. Compact SpyCatcher-functionalized QDs and UCNPs may be labeled with short-chain variable fragment Ab (scFv) engineered to bind urokinase-type plasminogen activator receptors (uPAR) that are overexpressed in many human cancers. Confocal imaging of anti-uPAR scFv-QD conjugates shows the antibody mediates specific binding and internalization by breast cancer cells expressing uPAR. Time-lapse imaging of photostable scFv-UCNP conjugates shows that Ab binding causes uPAR internalization with a ∼20 min half-life on the cell surface, and uPAR is internalized to endolysosomal compartments distinct from general membrane stains and without significant recycling to the cell surface. The controlled and stable conjugation of engineered Ab to NPs enables targeting of diverse receptors for live-cell study of their distribution, trafficking, and physiology.

Inhibition of PAI-1 Blocks PD-L1 Endocytosis and Improves the Response of Melanoma Cells to Immune Checkpoint Blockade

Immune checkpoint molecules, especially PD-1 and its ligand PD-L1, act as a major mechanism of cancer immune evasion. Although anti-PD-1/PD-L1 monotherapy increases therapeutic efficacy in melanoma treatment, only a subset of patients exhibits long-term tumor remission, and the underlying mechanism of resistance to PD-1/PD-L1 inhibitors remains unclear. In this study, we demonstrated that cell surface retention of PD-L1 is inversely correlated with PAI-1 expression in vitro, in vivo, and in clinical specimens. Moreover, extracellular PAI-1 induced the internalization of surface-expressed PD-L1 by triggering clathrin-mediated endocytosis. The endocytosed PD-L1 was transported to lysosomes for degradation by endolysosomal systems, resulting in the reduction of surface PD-L1. Notably, inhibition of PAI-1 by pharmacological inhibitor with tiplaxtinin led to elevated PD-L1 expression on the plasma membrane, both in vitro and in vivo. Strikingly, targeting PAI-1 by tiplaxtinin treatment synergizes with anti-PD-L1 immune checkpoint blockade therapy in a syngeneic murine model of melanoma. Our findings demonstrate a role for PAI-1 activity in immune checkpoint modulation by promoting surface PD-L1 for lysosomal degradation and provides an insight into the combination of PAI-1 inhibition and anti-PD-L1 immunotherapy as a promising therapeutic regimen for melanoma treatment.

The Endosomal Recycling Pathway-At the Crossroads of the Cell

The endosomal recycling pathway lies at the heart of the membrane trafficking machinery in the cell. It plays a central role in determining the composition of the plasma membrane and is thus critical for normal cellular homeostasis. However, defective endosomal recycling has been linked to a wide range of diseases, including cancer and some of the most common neurological disorders. It is also frequently subverted by many diverse human pathogens in order to successfully infect cells. Despite its importance, endosomal recycling remains relatively understudied in comparison to the endocytic and secretory transport pathways. A greater understanding of the molecular mechanisms that support transport through the endosomal recycling pathway will provide deeper insights into the pathophysiology of disease and will likely identify new approaches for their detection and treatment. This review will provide an overview of the normal physiological role of the endosomal recycling pathway, describe the consequences when it malfunctions, and discuss potential strategies for modulating its activity.

Oncogenic dependence of glioma cells on kish/TMEM167A regulation of vesicular trafficking

Genetic lesions in glioblastoma (GB) include constitutive activation of PI3K and EGFR pathways to drive cellular proliferation and tumor malignancy. An RNAi genetic screen, performed in Drosophila melanogaster to discover new modulators of GB development, identified a member of the secretory pathway: kish/TMEM167A. Downregulation of kish/TMEM167A impaired fly and human glioma formation and growth, with no effect on normal glia. Glioma cells increased the number of recycling endosomes, and reduced the number of lysosomes. In addition, EGFR vesicular localization was primed toward recycling in glioma cells. kish/TMEM167A downregulation in gliomas restored endosomal system to a physiological state and altered lysosomal function, fueling EGFR toward degradation by the proteasome. These endosomal effects mirrored the endo/lysosomal response of glioma cells to Brefeldin A (BFA), but not the Golgi disruption and the ER collapse, which are associated with the undesirable toxicity of BFA in other cancers. Our results suggest that glioma growth depends on modifications of the vesicle transport system, reliant on kish/TMEM167A. Noncanonical genes in GB could be a key for future therapeutic strategies targeting EGFR-dependent gliomas.

[A plasminogen regulation system in brain tumors]

INTRODUCTION

Tumor progression and neovascularization during malignant processes are believed to be associated with plasminogen activators and the PAI-1 inhibitor, but their role and interactions in various types of brain tumors have been studied insufficiently.

AIM

To conduct a comparative study of plasminogen regulation in optic nerve sheath meningiomas, glioblastomas, and brain metastases of breast cancer, as well as in perifocal tissues surrounding the tumors.

MATERIAL AND METHODS

Tumors and perifocal areas of 19 breast cancer (BC) metastases, 24 glioblastomas, and 13 meningiomas without perifocal edema were investigated by ELISA in 56 patients aged 35-72 years. Histological control was carried out in each case.

RESULTS

Significant differences were found in the levels of urokinase (uPA), tissue plasminogen activator (tPA), and PAI-1 inhibitor between glioblastomas and breast cancer metastases and the histologically unaltered (relatively intact) tissue around meningioma lesions (p≤0.05 in all cases). The levels of uPA-AG and uPA-act in meningioma were higher than those in the relatively intact tissue, while the levels of both tPA forms were reduced. The levels of uPA-AG and uPA-act in both malignant tumors and their perifocal areas were elevated compared to those in the relatively intact tissue. The levels of both tPA forms were reduced in all other tissues, except for glioblastoma. The level of PAI-1 inhibitor in malignant tissues was higher (being predominant in tumors) compared to that in the intact tissue surrounding meningioma, as well as relative to that in meningioma. The study proves that uPA and its inhibitor PAI-1 are directly involved in the metabolism of malignant gliomas and brain metastases of breast cancer. The role of tPA is to protect meningiomas; tPA activation in malignant brain tumors is suppressed.

Disruption of endolysosomal trafficking pathways in glioma cells by methuosis-inducing indole-based chalcones

Methuosis is a form of non-apoptotic cell death involving massive vacuolization of macropinosome-derived endocytic compartments, followed by a decline in metabolic activity and loss of membrane integrity. To explore the induction of methuosis as a potential therapeutic strategy for killing cancer cells, we have developed small molecules (indole-based chalcones) that trigger this form of cell death in glioblastoma and other cancer cell lines. Here, we report that in addition to causing fusion and expansion of macropinosome compartments, the lead compound, 3-(5-methoxy-2-methyl-1H-indol-3-yl)-1-(4-pyridinyl)-2-propen-1-one (MOMIPP), disrupts vesicular trafficking at the lysosomal nexus, manifested by impaired degradation of EGF and LDL receptors, defective processing of procathepsins, and accumulation of autophagosomes. In contrast, secretion of the ectodomain derived from a prototypical type-I membrane glycoprotein, β-amyloid precursor protein, is increased rather than diminished. A closely related MOMIPP analog, which causes substantial vacuolization without reducing cell viability, also impedes cathepsin processing and autophagic flux, but has more modest effects on receptor degradation. A third analog, which causes neither vacuolization nor loss of viability, has no effect on endolysosomal trafficking. The results suggest that differential cytotoxicity of structurally similar indole-based chalcones is related, at least in part, to the severity of their effects on endolysosomal trafficking pathways.

Molecular features of the cytotoxicity of an NHE inhibitor: Evidence of mitochondrial alterations, ROS overproduction and DNA damage

BACKGROUND

NH exchangers (NHEs) play a crucial role in regulating intra/extracellular pH, which is altered in cancer cells, and are therefore suitable targets to alter cancer cell metabolism in order to inhibit cell survival and proliferation. Among NHE inhibitors, amiloride family members are commonly used in clinical practice as diuretics; we focused on the amiloride HMA, reporting a net cytotoxic effect on a panel of human cancer cell lines; now we aim to provide new insights into the molecular events leading to cell death by HMA.

METHODS

Colon cancer cell lines were treated with HMA and analysed with: morphological and cellular assays for cell viability and death, and autophagy; biochemical approaches to evaluate mitochondrial function and ROS production; in situ detection of DNA damage; molecular tools to silence crucial autophagy/necroptosis factors.

RESULTS

HMA affects cellular morphology, alters mitochondrial structure and function, causes an increase in ROS, which is detrimental to DNA integrity, stimulates poly(ADP-ribose) synthesis, activates RIPK3-dependent death and triggers autophagy, which is unable to rescue cell survival. These features are hot points of an intricate network of processes, including necroptosis and autophagy, regulating the homeostasis between survival and death.

CONCLUSION

Our results allow the identification of multiple events leading to cell death in cancer cells treated with HMA. The here-defined intricate network activated by HMA could be instrumental to selectively target the key players of each pathway in the attempt to improve the global response to HMA. Our data could be the starting point for developing a newly designed targeted therapy.

Hexamethylene amiloride engages a novel reactive oxygen species- and lysosome-dependent programmed necrotic mechanism to selectively target breast cancer cells

Anticancer chemotherapeutics often rely on induction of apoptosis in rapidly dividing cells. While these treatment strategies are generally effective in debulking the primary tumor, post-therapeutic recurrence and metastasis are pervasive concerns with potentially devastating consequences. We demonstrate that the amiloride derivative 5-(N,N-hexamethylene) amiloride (HMA) harbors cytotoxic properties particularly attractive for a novel class of therapeutic agent. HMA is potently and specifically cytotoxic toward breast cancer cells, with remarkable selectivity for transformed cells relative to non-transformed or primary cells. Nonetheless, HMA is similarly cytotoxic to breast cancer cells irrespective of their molecular profile, proliferative status, or species of origin, suggesting that it engages a cell death mechanism common to all breast tumor subtypes. We observed that HMA induces a novel form of caspase- and autophagy-independent programmed necrosis relying on the orchestration of mitochondrial and lysosomal pro-death mechanisms, where its cytotoxicity was attenuated with ROS-scavengers or lysosomal cathepsin inhibition. Overall, our findings suggest HMA may efficiently target the heterogeneous populations of cancer cells known to reside within a single breast tumor by induction of a ROS- and lysosome-mediated form of programmed necrosis.