Cathepsin K: A Versatile Potential Biomarker and Therapeutic Target for Various Cancers

The potential contribution of aberrant cathepsin K expression to gastric cancer pathogenesis

The role of cathepsin K (CTSK) expression in the pathogenesis and progression of gastric cancer (GC) remains unclear. Hence, the primary objective of this study is to elucidate the precise expression and biological role of CTSK in GC by employing a combination of bioinformatics analysis and in vitro experiments. Our findings indicated a significant upregulation of CTSK in GC. The bioinformatics analysis revealed that GC patients with a high level of CTSK expression exhibited enrichment of hallmark gene sets associated with angiogenesis, epithelial-mesenchymal transition (EMT), inflammatory response, KRAS signaling up, TNFα signaling via KFκB, IL2-STAT5 signaling, and IL6-JAK-STAT3 signaling. Additionally, these patients demonstrated elevated levels of M2-macrophage infiltration, which was also correlated with a poorer prognosis. The results of in vitro experiments provided confirmation that the over-expression of CTSK leads to an increase in the proliferative and invasive abilities of GC cells. However, further evaluation was necessary to determine the impact of CTSK on the migration capability of these cells. Our findings suggested that CTSK has the potential to facilitate the initiation and progression of GC by augmenting the invasive capacity of GC cells, engaging in tumor-associated EMT, and fostering the establishment of an immunosuppressive tumor microenvironment (TME).

Engineering small-molecule and protein drugs for targeting bone tumors

Bone cancer is common and severe. Both primary (e.g., osteosarcoma, Ewing sarcoma) and secondary (e.g., metastatic) bone cancers lead to significant health problems and death. Currently, treatments such as chemotherapy, hormone therapy, and radiation therapy are used to treat bone cancer, but they often only shrink or slow tumor growth and do not eliminate cancer completely. The bone microenvironment contributes unique signals that influence cancer growth, immunogenicity, and metastasis. Traditional cancer therapies have limited effectiveness due to off-target effects and poor distribution on bones. As a result, therapies with improved specificity and efficacy for treating bone tumors are highly needed. One of the most promising strategies involves the targeted delivery of pharmaceutical agents to the site of bone cancer by introduction of bone-targeting moieties, such as bisphosphonates or oligopeptides. These moieties have high affinities to the bone hydroxyapatite matrix, a structure found exclusively in skeletal tissue, and can enhance the targeting ability and efficacy of anticancer drugs when combating bone tumors. This review focuses on the engineering of small molecules and proteins with bone-targeting moieties for the treatment of bone tumors.

Proteomics study of primary and recurrent adamantinomatous craniopharyngiomas

BACKGROUND

Adamantinomatous craniopharyngiomas (ACPs) are rare benign epithelial tumours with high recurrence and poor prognosis. Biological differences between recurrent and primary ACPs that may be associated with disease recurrence and treatment have yet to be evaluated at the proteomic level. In this study, we aimed to determine the proteomic profiles of paired recurrent and primary ACP, gain biological insight into ACP recurrence, and identify potential targets for ACP treatment.

METHOD

Patients with ACP (n = 15) or Rathke's cleft cyst (RCC; n = 7) who underwent surgery at Sanbo Brain Hospital, Capital Medical University, Beijing, China and received pathological confirmation of ACP or RCC were enrolled in this study. We conducted a proteomic analysis to investigate the characteristics of primary ACP, paired recurrent ACP, and RCC. Western blotting was used to validate our proteomic results and assess the expression of key tumour-associated proteins in recurrent and primary ACPs. Flow cytometry was performed to evaluate the exhaustion of tumour-infiltrating lymphocytes (TILs) in primary and recurrent ACP tissue samples. Immunohistochemical staining for CD3 and PD-L1 was conducted to determine differences in T-cell infiltration and the expression of immunosuppressive molecules between paired primary and recurrent ACP samples.

RESULTS

The bioinformatics analysis showed that proteins differentially expressed between recurrent and primary ACPs were significantly associated with extracellular matrix organisation and interleukin signalling. Cathepsin K, which was upregulated in recurrent ACP compared with that in primary ACP, may play a role in ACP recurrence. High infiltration of T cells and exhaustion of TILs were revealed by the flow cytometry analysis of ACP.

CONCLUSIONS

This study provides a preliminary description of the proteomic differences between primary ACP, recurrent ACP, and RCC. Our findings serve as a resource for craniopharyngioma researchers and may ultimately expand existing knowledge of recurrent ACP and benefit clinical practice.

Inhibitory effect of O-propargyllawsone in A549 lung adenocarcinoma cells

BACKGROUND

Lung cancer is the deadliest type of cancer in the world and the search for compounds that can treat this disease is highly important. Lawsone (2-hydroxy-1,4-naphtoquinone) is a naphthoquinone found in plants from the Lawsone genus that show a high cytotoxic effect in cancer cell lines and its derivatives show an even higher cytotoxic effect.

METHODS

Sulforhodamine B was used to evaluate the cytotoxic activity of compounds on tumor cells. Clonogenic assay was used to analyze the reduction of colonies and wound healing assay to the migratory capacity of A549 cells. Apoptosis and necrosis were analyzed by flow cytometer and Giemsa staining. Hemolysis assay to determine toxicity in human erythrocytes.

RESULTS

Lawsone derivatives were evaluated and compound 1 (O-propargyllawsone) was the one with the highest cytotoxic effect, with IC50 below 2.5 µM in A549 cells. The compound was able to reduce colony formation and inhibit cell migration. Morphological changes and cytometry analysis show that the compound induces apoptosis and necrosis in A549 cells.

CONCLUSIONS

These results show that O-propargyllawsone show a cytotoxic effect and may induce apoptosis in A549 cells.

Cell mediated ECM-degradation as an emerging tool for anti-fibrotic strategy

Investigation into the role of cells with respect to extracellular matrix (ECM) remodeling is still in its infancy. Particularly, ECM degradation is an indispensable process during the recovery from fibrosis. Cells with ECM degradation ability due to the secretion of various matrix metalloproteinases (MMPs) have emerged as novel contributors to the treatment of fibrotic diseases. In this review, we focus on the ECM degradation ability of cells associated with the repertoire of MMPs that facilitate the attenuation of fibrosis through the inhibition of ECM deposition. Besides, innovative approaches to engineering and characterizing cells with degradation ability, as well as elucidating the mechanism of the ECM degradation, are also illustrated. Studies conducted to date on the use of cell-based degradation for therapeutic purposes to combat fibrosis are summarized. Finally, we discuss the therapeutic potential of cells with high degradation ability, hoping to bridge the gap between benchside research and bedside applications in treating fibrotic diseases.

CD200-CD200R affects cisplatin and paclitaxel sensitivity by regulating cathepsin K-mediated p65 NF-κB signaling in cervical cancer

Background

CD200-CD200R plays a critical role in regulating the human tumor microenvironment, but its role in cervical cancer remains unclear.

Methods

A total of 62 paraffin blocks of tumor tissues were collected from cervical cancer patients. Expression of CD200 and cathepsin K (CTSK) in cancer tissues and para-cancerous tissues was analyzed by immunohistochemistry. Stably transfected CD200 cells were established in HeLa and SiHa cells. Human THP-1 monocytes were induced to differentiate into M2 macrophages. HeLa and SiHa cells were cultured in conditioned medium from M2 macrophages to observe the effects of CD200-CD200R on invasion, CTSK, p65NF-κB, and cisplatin or paclitaxel sensitivity in cervical cancer cells. HeLa cells were injected to induce xenograft tumors in mice, and a CTSK inhibitor, MK-0822, was used to confirm the regulation of CTSK and paclitaxel sensitivity by CD200-CD200R in vivo.

Results

A significant decrease in CD200 and CTSK expression was found in tumor cancer tissues compared with para-cancerous tissues. Only CD200 overexpression did not affect cervical cell invasion, but CD200-CD200R could enhance the cell invasion and resistance to cisplatin or paclitaxel. Meanwhile, expression of CTSK and p-p65NF-κB in cancer cells stably transfected with CD200 was obviously increased after culture in conditioned medium from M2 macrophages compared with transfection with the plasmid control. In vivo, CTSK inhibition significantly suppressed the effects of CD200-CD200R overexpression on the response to paclitaxel by suppressing the CTSK-mediated NF-κB pathway.

Conclusions

CD200-CD200R regulates CTSK-mediated NF-κB pathway to affect cisplatin or paclitaxel sensitivity in cervical cancer, which provides a possible immunotherapeutic target and combination strategy for advanced cervical cancer.

Cathepsin K inhibition induces Raptor destabilization and mitochondrial dysfunction via Syk/SHP2/Src/OTUB1 axis-mediated signaling

The Raptor signaling pathway is a critical point of intervention in the invasion and progression of cancer. The non-receptor tyrosine kinase Src-mediated phosphorylation of OTUB1-Y26 plays a critical role in Raptor stabilization, whereas cathepsin K inhibitor (odanacatib; ODN) and knockdown (siRNA) induce Raptor destabilization. However, the mechanisms involved in cathepsin K inhibition-induced OTUB1-Y26 phosphorylation in Raptor stabilization have not been yet elucidated. This study showed that cathepsin K inhibition activates SHP2, a tyrosine phosphatase, that dephosphorylates OTUB1 and destabilizes Raptor, whereas SHP2 deletion and pharmacological inhibition increase OTUB1-Y26 phosphorylation and Raptor expression. SHP2 deletion also led to the inhibition of ODN-induced mitochondrial ROS, fusion, and dysfunction. Furthermore, cathepsin K inhibition phosphorylated spleen tyrosine kinase (Syk) at Y525 and Y526, resulting in the SHP2-mediated dephosphorylation of OTUB1-Y26. Collectively, our findings identified Syk not only as an upstream tyrosine kinase required for SHP2 activation but also showed a critical mechanism that regulates ODN-induced Raptor downregulation and mitochondrial dysfunction. In conclusion, Syk/SHP2/Src/OTUB1 axis-mediated signaling can act as a therapeutic target in cancer management.

Clinicopathological correlation of Cathepsin K expression in salivary gland carcinomas; relation to patients` outcome

BACKGROUND

Salivary gland carcinomas (SGCs) represent various groups of tumors that demonstrate marked diversity in their prognosis owing to different histology and clinical characteristics. One of the poor prognostic indicators is distant metastasis which is considered the major reason for death in SGC patients. Discovering new biomarkers is urgently required to aid in the detection of cancer onset and progression. Cathepsin K (CTSK), the lysosomal cysteine protease has a principal role in cancer invasion and progression through interaction with the tumor microenvironment, degradation of extracellular membrane proteins and destruction of the elastic lamina of blood vessels. In the English literature, little information was present about the role of CTSK in SGCs. The current study aimed to assess the immunohistochemical expression of CTSK in SGCs and correlate its expression to different clinicopathologic parameters.

METHODS

The retrospective study applied to 45 cases of SGCs categorized as high-grade (33 cases) and low-grade SGCs (12 cases) following the criteria of WHO classification (2017) of head and neck tumors. All patients` clinicopathological and follow-up records were retrieved. The following statistical tests were used to study the variance of CTSK expression in SGCs concerning different clinicopathological parameters; Pearson`s Chi-square test, unpaired two-tailed student t-test, One-way ANOVA, and Post Hoc tests. Disease-free survival (DFS) and Overall survival (OS) were calculated and displayed with the Kaplan-Meier strategy and analyzed with the log-rank test. Univariate and multivariate survival analyses were performed with Cox regression. A P-value lesser than 0.05 was considered statistically significant.

RESULTS

Strong CTSK expression was significantly related to high-grade SGCs (P = 0.000), large infiltrating carcinomas (P = 0.000), presence of nodal (P = 0.041) and distant metastasis (P = 0.009), advanced TNM clinical stage (P = 0.000), the incidence of recurrence (P = 0.009), and reduced DFS (P = 0.006). Distant metastasis was the independent predictor for DFS using Cox regression model.

CONCLUSIONS

CTSK has a great role in cancer progression by triggering many signaling pathways. Its level in cancerous tissue is considered an effective index for predicting the severity and prognosis of cancer. Therefore, we indicate its utility as a prognostic tool and therapeutic target for cancer treatment.

TRIAL REGISTRATION

Retrospectively registered.

The immunoregulatory protein CD200 as a potentially lucrative yet elusive target for cancer therapy

CD200 is an immunoregulatory cell surface ligand with proven pro-tumorigenic credentials via its ability to suppress CD200 receptor (CD200R)-expressing anti-tumor immune function. This definitive role for the CD200-CD200R axis in regulating an immunosuppressive tumor microenvironment has garnered increasing interest in CD200 as a candidate target for immune checkpoint inhibition therapy. However, while the CD200 blocking antibody samalizumab is still in the early stages of clinical testing, alternative mechanisms for the pro-tumorigenic role of CD200 have recently emerged that extend beyond direct suppression of anti-tumor T cell responses and, as such, may not be susceptible to CD200 antibody blockade. Herein, we will summarize the current understanding of CD200 expression and function in the tumor microenvironment as well as alternative strategies for potential neutralization of multiple CD200 mechanisms in human cancers.

Proteolytic Biosensors with Functional Nanomaterials: Current Approaches and Future Challenges

Proteolytic enzymes are one of the important biomarkers that enable the early diagnosis of several diseases, such as cancers. A specific proteolytic enzyme selectively degrades a certain sequence of a polypeptide. Therefore, a particular proteolytic enzyme can be selectively quantified by changing detectable signals causing degradation of the peptide chain. In addition, by combining polypeptides with various functional nanomaterials, proteolytic enzymes can be measured more sensitively and rapidly. In this paper, proteolytic enzymes that can be measured using a polypeptide degradation method are reviewed and recently studied functional nanomaterials-based proteolytic biosensors are discussed. We anticipate that the proteolytic nanobiosensors addressed in this review will provide valuable information on physiological changes from a cellular level for individual and early diagnosis.

Molecular mechanisms behind ROS regulation in cancer: A balancing act between augmented tumorigenesis and cell apoptosis

ROS include hydroxyl radicals (HO^.), superoxide (O₂^..), and hydrogen peroxide (H₂O₂). ROS are typically produced under physiological conditions and play crucial roles in living organisms. It is known that ROS, which are created spontaneously by cells through aerobic metabolism in mitochondria, can have either a beneficial or detrimental influence on biological systems. Moderate levels of ROS can cause oxidative damage to proteins, DNA and lipids, which can aid in the pathogenesis of many disorders, including cancer. However, excessive concentrations of ROS can initiate programmed cell death in cancer. Presently, a variety of chemotherapeutic drugs and herbal agents are being investigated to induce ROS-mediated cell death in cancer. Therefore, preserving ROS homeostasis is essential for ensuring normal cell development and survival. On account of a significant association of ROS levels at various concentrations with carcinogenesis in a number of malignancies, further studies are needed to determine the underlying molecular mechanisms and develop the possibilities for intervening in these processes.

Cathepsin K in Pathological Conditions and New Therapeutic and Diagnostic Perspectives

Cathepsin K (CatK) is a part of the family of cysteine proteases involved in many important processes, including the degradation activity of collagen 1 and elastin in bone resorption. Changes in levels of CatK are associated with various pathological conditions, primarily related to bone and cartilage degradation, such as pycnodysostosis (associated with CatK deficiency), osteoporosis, and osteoarthritis (associated with CatK overexpression). Recently, the increased secretion of CatK is being highly correlated to vascular inflammation, hypersensitivity pneumonitis, Wegener granulomatosis, berylliosis, tuberculosis, as well as with tumor progression. Due to the wide spectrum of diseases in which CatK is involved, the design and validation of active site-specific inhibitors has been a subject of keen interest in pharmaceutical companies in recent decades. In this review, we summarized the molecular background of CatK and its involvement in various diseases, as well as its clinical significance for diagnosis and therapy.