Calpain as a therapeutic target in cancer

CAPN2-responsive mesoporous silica nanoparticles: A promising nanocarrier for targeted therapy of pancreatic cancer

Pancreatic adenocarcinoma (PDAC) is highly resistant to conventional chemotherapeutic interventions, resulting in exceptionally low survival rates. The limited efficacy can in part be attributed to dose limitations and treatment cessation urged by toxicity of currently used chemotherapy. The advent of targeted delivery strategies has kindled hope for circumventing off-target toxicity. We have previously reported a PDAC-specific mesoporous silica nanoparticle (MSN) containing a protease linker responsive to ADAM9, a PDAC-enriched extracellularly deposited protease. Upon loading with paclitaxel these ADAM9-MSNs reduced side effects both in vitro and in vivo, however, disappointing antitumor efficacy was observed in vivo. Here, we propose that an efficient uptake of MSNs by tumor cells might underlie the lack of antitumor efficacy of MSNs functionalized with linker responsive to extracellular proteases. Harnessing this premise to improve antitumor efficacy, we performed an in silico analysis to identify PDAC-enriched intracellular proteases. We report the identification of BACE2, CAPN2 and DPP3 as PDAC enriched intracellular proteases, and report the synthesis of BACE2-, CAPN2- and DPP3-responsive MSNs. Extensive preclinical assessments revealed that paclitaxel-loaded CAPN2- and DPP3-MSNs exhibit high PDAC specificity in vitro as opposed to free paclitaxel. The administration of paclitaxel-loaded CAPN2- and DPP3-MSNs in vivo confirmed the reduction of leukopenia and induced no organ damage. Promisingly, in two mouse models CAPN2-MSNs reduced tumor growth at least as efficiently as free paclitaxel. Taken together, our results pose CAPN2-MSNs as a promising nanocarrier for the targeted delivery of chemotherapeutics in PDAC.

Tiliroside disrupted iron homeostasis and induced ferroptosis via directly targeting calpain-2 in pancreatic cancer cells

BACKGROUND

Tiliroside (TIL) is a flavonoid compound that exists in a variety of edible plants. These dietary plants are widely used as food and medicine to treat various diseases. However, the effect of TIL on pancreatic cancer (PC) and its underlying mechanisms are unclear.

PURPOSE

This study aims to reveal the anti-PC effect of TIL and clarify its mechanism.

METHODS

The inhibitory effects of TIL on PC growth were studied both in vitro and in vivo. Flow cytometry, transmission electron microscopy, immunofluorescence, biochemical analyses, RT-qPCR, genetic ablation, and western blotting were employed to evaluate ferroptosis, autophagy, and iron regulation. Additionally, RNA sequencing (RNA-seq), biomolecular layer interferometry (BLI), and molecular simulation analysis were combined to identify TIL molecular targets. The clinicopathological significance of Calpain-2 (CAPN2) was determined through immunohistochemistry (IHC) on a PC tissue microarray.

RESULTS

Herein, we showed that TIL was an effective anti-PC drug. CAPN2 was involved in the TIL - induced elevation of the labile iron pool (LIP) in PC cells. TIL directly bound to and inhibited CAPN2 activity, resulting in AKT deactivation and decreased expression of glucose transporters (GLUT1 and GLUT3) in PC cells. Consequently, TIL impaired ATP and NADPH generation, inducing autophagy and ROS production. The accumulation of TIL-induced ROS combined with LIP iron causes the Fenton reaction, leading to lipid peroxidation. Meanwhile, TIL-induced reduction of free iron ions promoted autophagic degradation of ferritin to regulate cellular iron homeostasis, which further exacerbated the death of PC cells by ferroptosis. As an extension of these in vitro findings, our murine xenograft study showed that TIL inhibited the growth of PANC-1 cells. Additionally, we showed that CAPN2 expression levels were related to clinical prognoses in PC patients.

CONCLUSION

We identify TIL as a potent bioactive inhibitor of CAPN2 and an anti-PC candidate of natural origin. These findings also highlight CAPN2 as a potential target for PC treatment.

17β-Estradiol promotes metastasis in triple-negative breast cancer through the Calpain/YAP/β-catenin signaling axis

β-catenin is an important regulator of malignant progression. 17β-Estradiol (E2), an important sex hormone in women, promotes the growth and metastasis of triple-negative breast cancer (TNBC). However, whether β-catenin is involved in E2-induced metastasis of TNBC remains unknown. In this study, we show that E2 induces the proliferation, migration, invasion, and metastasis of TNBC cells. E2 induces β-catenin protein expression and nuclear translocation, thereby regulating the expression of target genes such as Cyclin D1 and MMP-9. The inhibition of β-catenin reversed the E2-induced cell malignant behaviors. Additionally, E2 activated Calpain by increasing intracellular Ca2+ levels and reducing calpastatin levels. When Calpain was inhibited, E2 did not induce the proliferation, migration, invasion, or metastasis of TNBC cells. In addition, E2 promoted translocation of YAP into the nucleus by inhibiting its phosphorylation. Calpain inhibition reversed the E2-induced YAP dephosphorylation. Inhibition of YAP transcriptional activity reversed the effects of E2 on the proliferation, migration, invasion, and β-catenin of TNBC cells. In conclusion, we demonstrated that E2 induced metastasis-related behaviors in TNBC cells and this effect was mediated through the Calpain/YAP/β-catenin signaling pathway.

Human calpain-3 and its structural plasticity: dissociation of a homohexamer into dimers on binding titin

Calpain-3 is an intracellular Ca2+-dependent cysteine protease abundant in skeletal muscle. Its physiological role in the sarcomere is thought to include removing damaged muscle proteins after exercise. Loss-of-function mutations in its single-copy gene cause a dystrophy of the limb-girdle muscles. These mutations, of which there are over 500 in humans, are spread all along this 94-kDa multi-domain protein that includes three 40+-residue sequences (NS, IS1, and IS2). The latter sequences are unique to this calpain isoform and are hypersensitive to proteolysis. To investigate the whole enzyme structure and how mutations might affect its activity, we produce the proteolytically more stable 85-kDa calpain-3 ΔNS ΔIS1 form with a C129A inactivating mutation as a recombinant protein in E. coli. During size-exclusion chromatography, this calpain-3 was consistently eluted as a much larger 0.5-MDa complex rather than the expected 170-kDa dimer. Its size, which was confirmed by SEC-MALS, Blue Native PAGE, and AUC, made the complex amenable to single-particle cryo-EM analysis. From two data sets, we obtained a 3.85-Å reconstruction map that shows the complex is a trimer of calpain-3 dimers with six penta-EF-hand domains at its core. Calpain-3 has been reported to bind the N2A region of the giant muscle protein titin. When this 37-kDa region of titin was co-expressed with calpain-3 the multimer was reduced to a 320-kDa particle, which appears to be the calpain dimer bound to several copies of the titin fragment. We suggest that newly synthesized calpain-3 is kept as an inactive hexamer until it binds the N2A region of titin in the sarcomere, whereupon it dissociates into functional dimers.

The neuronal transcription factor MEIS2 is a calpain-2 protease target

Tight control over transcription factor activity is necessary for a sensible balance between cellular proliferation and differentiation in the embryo and during tissue homeostasis by adult stem cells, but mechanistic details have remained incomplete. The homeodomain transcription factor MEIS2 is an important regulator of neurogenesis in the ventricular-subventricular zone (V-SVZ) adult stem cell niche in mice. We here identify MEIS2 as direct target of the intracellular protease calpain-2 (composed of the catalytic subunit CAPN2 and the regulatory subunit CAPNS1). Phosphorylation at conserved serine and/or threonine residues, or dimerization with PBX1, reduced the sensitivity of MEIS2 towards cleavage by calpain-2. In the adult V-SVZ, calpain-2 activity is high in stem and progenitor cells, but rapidly declines during neuronal differentiation, which is accompanied by increased stability of MEIS2 full-length protein. In accordance with this, blocking calpain-2 activity in stem and progenitor cells, or overexpression of a cleavage-insensitive form of MEIS2, increased the production of neurons, whereas overexpression of a catalytically active CAPN2 reduced it. Collectively, our results support a key role for calpain-2 in controlling the output of adult V-SVZ neural stem and progenitor cells through cleavage of the neuronal fate determinant MEIS2.

Intensive care unit-acquired weakness: Recent insights

Intensive care unit-acquired weakness (ICU-AW) is a common complication in critically ill patients and is associated with a variety of adverse outcomes. These include the need for prolonged mechanical ventilation and ICU stay; higher ICU, in-hospital, and 1-year mortality; and increased in-hospital costs. ICU-AW is associated with multiple risk factors including age, underlying disease, severity of illness, organ failure, sepsis, immobilization, receipt of mechanical ventilation, and other factors related to critical care. The pathological mechanism of ICU-AW remains unclear and may be considerably varied. This review aimed to evaluate recent insights into ICU-AW from several aspects including risk factors, pathophysiology, diagnosis, and treatment strategies; this provides new perspectives for future research.

Challenges in bridging the gap between protein structure prediction and functional interpretation

The rapid evolution of protein structure prediction tools has significantly broadened access to protein structural data. Although predicted structure models have the potential to accelerate and impact fundamental and translational research significantly, it is essential to note that they are not validated and cannot be considered the ground truth. Thus, challenges persist, particularly in capturing protein dynamics, predicting multi-chain structures, interpreting protein function, and assessing model quality. Interdisciplinary collaborations are crucial to overcoming these obstacles. Databases like the AlphaFold Protein Structure Database, the ESM Metagenomic Atlas, and initiatives like the 3D-Beacons Network provide FAIR access to these data, enabling their interpretation and application across a broader scientific community. Whilst substantial advancements have been made in protein structure prediction, further progress is required to address the remaining challenges. Developing training materials, nurturing collaborations, and ensuring open data sharing will be paramount in this pursuit. The continued evolution of these tools and methodologies will deepen our understanding of protein function and accelerate disease pathogenesis and drug development discoveries.

Calpains, the proteases of two faces controlling the epithelial homeostasis in mammary gland

Calpain-1 and calpain-2 are calcium-dependent Cys-proteases ubiquitously expressed in mammalian tissues with a processive, rather than degradative activity. They are crucial for physiological mammary gland homeostasis as well as for breast cancer progression. A growing number of evidences indicate that their pleiotropic functions depend on the cell type, tissue and biological context where they are expressed or dysregulated. This review considers these standpoints to cover the paradoxical role of calpain-1 and -2 in the mammary tissue either, under the physiological conditions of the postlactational mammary gland regression or the pathological context of breast cancer. The role of both calpains will be examined and discussed in both conditions, followed by a brief snapshot on the present and future challenges for calpains, the two-gateway proteases towards tissue homeostasis or tumor development.

Suppressing Src-Mediated EGFR Signaling by Sustained Calcium Supply Targeting Triple-Negative Breast Cancer

Src is emerging as a promising target in triple-negative breast cancer (TNBC) treatment because it activates survival signaling linked to the epidermal growth factor receptor. In this study, the effect of calcium supply on Src degradation was investigated to confirm underlying mechanisms and anticancer effects targeting TNBC. MDA-MB-231 cells, the TNBC cell line, were used. Calcium supply was feasible through lactate calcium salt (CaLac), and the applicable calcium concentration was decided by changes in the viability with different doses of CaLac. Expression of signaling molecules mediated by calcium-dependent Src degradation was observed by Western blot analysis and immunocytochemistry, and the recovery of the signaling molecules was confirmed following calpeptin treatment. The anticancer effect was investigated in the xenograft animal model. Significant suppression of Src was induced by calcium supply, followed by a successive decrease in the expression of epithelial growth factor receptor, RAS, extracellular signal-regulated kinase, and nuclear factor kappa B. Then, the suppression of cyclooxygenase-2 contributed to a significant deactivation of the prostaglandin E2 receptors. These results suggest that calcium supply has the potential to reduce the risk of TNBC. However, as this study is at an early stage to determine clinical applicability, close consideration is needed.

A cysteine proteinase inhibitor ALLN alleviates bleomycin-induced skin and lung fibrosis

BACKGROUND

Systemic sclerosis (SSc) is a connective tissue disease that is characterized by fibrosis in the skin and internal organs, such as the lungs. Activated differentiation of progenitor cells, which are mainly resident fibroblasts, into myofibroblasts is considered a key mechanism underlying the overproduction of extracellular matrix and the resultant tissue fibrosis in SSc. Calpains are members of the Ca2+-dependent cysteine protease family, whose enzymatic activities participate in signal transduction and tissue remodeling, potentially contributing to fibrosis in various organs. However, the roles of calpain in the pathogenesis of SSc remain unknown. This study aimed to examine the anti-fibrotic properties of N-acetyl-Leu-Leu-norleucinal (ALLN), one of the cysteine proteinase inhibitors that primarily inhibit calpain, in vitro and in vivo, to optimally translate into the therapeutic utility in human SSc.

METHODS

Normal human dermal and lung fibroblasts pretreated with ALLN were stimulated with recombinant transforming growth factor beta 1 (TGF-β1), followed by assessment of TGF-β1/Smad signaling and fibrogenic molecules.

RESULTS

ALLN treatment significantly inhibited TGF-β1-induced phosphorylation and nuclear transport of Smad2/3 in skin and lung fibroblasts. TGF-β1-dependent increases in α-smooth muscle actin (αSMA), collagen type I, fibronectin 1, and some mesenchymal transcription markers were attenuated by ALLN. Moreover, our findings suggest that ALLN inhibits TGF-β1-induced mesenchymal transition in human lung epithelial cells. Consistent with these in vitro findings, administering ALLN (3 mg/kg/day) three times a week intraperitoneally remarkably suppressed the development of skin and lung fibrosis in a SSc mouse model induced by daily subcutaneous bleomycin injection. The number of skin- and lung-infiltrating CD3+ T cells decreased in ALLN-treated mice compared with that in control-treated mice. Phosphorylation of Smad3 and/or an increase in αSMA-positive myofibroblasts was significantly inhibited by ALLN treatment on the skin and lungs. However, no adverse effects were observed.

CONCLUSIONS

Our results prove that calpains can be a novel therapeutic target for skin and lung fibrosis in SSc, considering its inhibitor ALLN.

Thiosulfinates: Cytotoxic and Antitumor Activity

Pharmacological value of some natural compounds makes them attractive for use in oncology. The sulfur-containing thiosulfinates found in plants of the genus Allium have long been known as compounds with various therapeutic properties, including antitumor. Over the last few years, the effect of thiosulfinates on various stages of carcinogenesis has been actively investigated. In vitro and in vivo studies have shown that thiosulfinates inhibit proliferation of cancer cells, as well as they induce apoptosis. The purpose of this review is to summarize current data on the use of natural and synthetic thiosulfinates in cancer therapy. Antitumor mechanisms and molecular targets of these promising compounds are discussed. A significant part of the review is devoted to consideration of a new strategy for treatment of oncological diseases - use of the directed enzyme prodrug therapy approach aiming to obtain antitumor thiosulfinates in situ.

Inclusion Body Myositis and Neoplasia: A Narrative Review

Inclusion body myositis (IBM) is an acquired, late-onset inflammatory myopathy, with both inflammatory and degenerative pathogenesis. Although idiopathic inflammatory myopathies may be associated with malignancies, IBM is generally not considered paraneoplastic. Many studies of malignancy in inflammatory myopathies did not include IBM patients. Indeed, IBM is often diagnosed only after around 5 years from onset, while paraneoplastic myositis is generally defined as the co-occurrence of malignancy and myopathy within 1 to 3 years of each other. Nevertheless, a significant association with large granular lymphocyte leukemia has been recently described in IBM, and there are reports of cancer-associated IBM. We review the pathogenic mechanisms supposed to be involved in IBM and outline the common mechanisms in IBM and malignancy, as well as the therapeutic perspectives. The terminally differentiated, CD8+ highly cytotoxic T cells expressing NK features are central in the pathogenesis of IBM and, paradoxically, play a role in some cancers as well. Interferon gamma plays a central role, mostly during the early stages of the disease. The secondary mitochondrial dysfunction, the autophagy and cell cycle dysregulation, and the crosstalk between metabolic and mitogenic pathways could be shared by IBM and cancer. There are intermingled subcellular mechanisms in IBM and neoplasia, and probably their co-existence is underestimated. The link between IBM and cancers deserves further interest, in order to search for efficient therapies in IBM and to improve muscle function, life quality, and survival in both diseases.

Immune suppressive function of IL-1α release in the tumor microenvironment regulated by calpain 1

Interleukin-1α (IL-1α) plays an important role in inflammation and hematopoiesis. Many tumors have increased IL-1α expression. However, the immune regulatory role of secreted IL-1α in tumor development and whether it can be targeted for cancer therapy are still unclear. Here, we found that tumoral-secreted IL-1α significantly promoted hepatocellular carcinoma (HCC) development in vivo. Tumoral-released IL-1α were found to inhibit T and NK cell activation, and the killing capacity of CD8⁺ T cells. Moreover, MDSCs were dramatically increased by tumoral-released IL-1α in both spleens and tumors. Indeed, higher tumoral IL-1α expression is associated with increased tumoral infiltration of MDSCs in HCC patients. Further studies showed that tumoral-released IL-1α promoted MDSC recruitment to the tumor microenvironment through a CXCR2-dependent mechanism. Depletion of MDSCs could diminish the tumor-promoting effect of tumoral-released IL-1α. On the contrary, systemic administration of recombinant IL-1α protein significantly inhibited tumor development by activating T cells. In fact, IL-1α protein could promote T cell activation and enhance the cytotoxicity of CD8⁺ T cells in vitro. Thus, our study demonstrated that tumoral-released IL-1α promoted tumor development through recruiting MDSCs to inhibit T cell activation, while systemic IL-1α directly promoted anti-tumor T cell responses. We further identified calpain 1 as the major intracellular protease mediating tumoral IL-1α secretion. Calpain 1 KO tumors had diminished IL-1α release and reduced tumor development. Thus, our findings provide new insights into the functions of secreted IL-1α in tumor immunity and its implications for immunotherapy.