Cathepsin S is aberrantly overexpressed in human hepatocellular carcinoma

Cysteine cathepsins: From diagnosis to targeted therapy of cancer

Cysteine cathepsins are a fascinating group of proteolytic enzymes that play diverse and crucial roles in numerous biological processes, both in health and disease. Understanding these proteases is essential for uncovering novel insights into the underlying mechanisms of a wide range of disorders, such as cancer. Cysteine cathepsins influence cancer biology by participating in processes such as extracellular matrix degradation, angiogenesis, immune evasion, and apoptosis. In this comprehensive review, we explore foundational research that illuminates the diverse and intricate roles of cysteine cathepsins as diagnostic markers and therapeutic targets for cancer. This review aims to provide valuable insights into the clinical relevance of cysteine cathepsins and explore their capacity to advance personalised and targeted medical interventions in oncology.

The current landscape of the antimicrobial peptide melittin and its therapeutic potential

Melittin, a main component of bee venom, is a cationic amphiphilic peptide with a linear α-helix structure. It has been reported that melittin can exert pharmacological effects, such as antitumor, antiviral and anti-inflammatory effects in vitro and in vivo. In particular, melittin may be beneficial for the treatment of diseases for which no specific clinical therapeutic agents exist. Melittin can effectively enhance the therapeutic properties of some first-line drugs. Elucidating the mechanism underlying melittin-mediated biological function can provide valuable insights for the application of melittin in disease intervention. However, in melittin, the positively charged amino acids enables it to directly punching holes in cell membranes. The hemolysis in red cells and the cytotoxicity triggered by melittin limit its applications. Melittin-based nanomodification, immuno-conjugation, structural regulation and gene technology strategies have been demonstrated to enhance the specificity, reduce the cytotoxicity and limit the off-target cytolysis of melittin, which suggests the potential of melittin to be used clinically. This article summarizes research progress on antiviral, antitumor and anti-inflammatory properties of melittin, and discusses the strategies of melittin-modification for its future potential clinical applications in preventing drug resistance, enhancing the selectivity to target cells and alleviating cytotoxic effects to normal cells.

All Roads Lead to Cathepsins: The Role of Cathepsins in Non-Alcoholic Steatohepatitis-Induced Hepatocellular Carcinoma

Cathepsins are lysosomal proteases that are essential to maintain cellular physiological homeostasis and are involved in multiple processes, such as immune and energy regulation. Predominantly, cathepsins reside in the lysosomal compartment; however, they can also be secreted by cells and enter the extracellular space. Extracellular cathepsins have been linked to several pathologies, including non-alcoholic steatohepatitis (NASH) and hepatocellular carcinoma (HCC). NASH is an increasingly important risk factor for the development of HCC, which is the third leading cause of cancer-related deaths and poses a great medical and economic burden. While information regarding the involvement of cathepsins in NASH-induced HCC (NASH-HCC) is limited, data to support the role of cathepsins in either NASH or HCC is accumulating. Since cathepsins play a role in both NASH and HCC, it is likely that the role of cathepsins is more significant in NASH-HCC compared to HCC derived from other etiologies. In the current review, we provide an overview on the available data regarding cathepsins in NASH and HCC, argue that cathepsins play a key role in the transition from NASH to HCC, and shed light on therapeutic options in this context.

The multifaceted role of cathepsins in liver disease

Proteases are the most abundant enzyme gene family in vertebrates and they execute essential functions in all living organisms. Their main role is to hydrolase the peptide bond within proteins, a process also called proteolysis. Contrary to the conventional paradigm, proteases are not only random catalytic devices, but can perform highly selective and targeted cleavage of specific substrates, finely modulating multiple essential cellular processes. Lysosomal protease cathepsins comprise 3 families of proteases that preferentially act within acidic cellular compartments, but they can also be found in other cellular locations. They can operate alone or as part of signalling cascades and regulatory circuits, playing important roles in apoptosis, extracellular matrix remodelling, hepatic stellate cell activation, autophagy and metastasis, contributing to the initiation, development and progression of liver disease. In this review, we comprehensively summarise current knowledge on the role of lysosomal cathepsins in liver disease, with a particular emphasis on liver fibrosis, non-alcoholic fatty liver disease and hepatocellular carcinoma.

An Immunosensor for the Determination of Cathepsin S in Blood Plasma by Array SPRi-A Comparison of Analytical Properties of Silver-Gold and Pure Gold Chips

The array SPR imaging (SPRi) technique is well suited to the determination of biomarkers in body fluids, called liquid biopsy. No signal enhancement or analyte preconcentration is required. With the aim of achieving signal enhancement and lowering the cost of a single determination, the replacement of gold-covered chips by silver–gold chips was investigated. The aim of this work was to investigate the analytical characteristics of a biosensor formed on a Ag/Au chip and to compare them with those of a biosensor formed on a gold chip. A biosensor for the determination of cathepsin S (Cath S) was chosen as an example. The biosensor consisted of the linker cysteamine and an immobilized rat monoclonal antibody specific for cathepsin S. Both biosensors exhibited a Langmuirian response to Cath S concentration, with linear response ranging from LOQ to 1.5 ng mL⁻¹. The LOQ is 0.1 ng mL⁻¹ for the biosensor formed on the Ag/Au chip, and 0.22 ng mL⁻¹ for that formed on the gold chip. Recoveries and precision for medium and high Cath S concentrations were acceptable for both biosensors, i.e., precision better than 10% and recoveries within the range 102–105%. However, the results for the lowest Cath S concentration were better for the biosensor formed on the Ag/Au chip (9.4 and 106% for precision and recovery, respectively). Generally, no significant differences in analytical characteristics were observed between the Ag/Au and Au chips. The two biosensors were also compared in the determination of Cath S in real samples. Nine plasma samples from healthy donors and nine from patients with ovarian cancer were analyzed for Cath S concentration with the biosensors formed on Ag/Au and Au chips. The results obtained with the two biosensors were very similar and show no significant differences on the Bland–Altman plot. The Cath S concentration in the blood plasma of ovarian cancer patients was elevated by one order of magnitude as compared with the control (12.6 ± 3.6 vs. 1.6 ± 1.2 ng mL⁻¹).

Novel Opportunities for Cathepsin S Inhibitors in Cancer Immunotherapy by Nanocarrier-Mediated Delivery

Cathepsin S (CatS) is a secreted cysteine protease that cleaves certain extracellular matrix proteins, regulates antigen presentation in antigen-presenting cells (APC), and promotes M2-type macrophage and dendritic cell polarization. CatS is overexpressed in many solid cancers, and overall, it appears to promote an immune-suppressive and tumor-promoting microenvironment. While most data suggest that CatS inhibition or knockdown promotes anti-cancer immunity, cell-specific inhibition, especially in myeloid cells, appears to be important for therapeutic efficacy. This makes the design of CatS selective inhibitors and their targeting to tumor-associated M2-type macrophages (TAM) and DC an attractive therapeutic strategy compared to the use of non-selective immunosuppressive compounds or untargeted approaches. The selective inhibition of CatS can be achieved through optimized small molecule inhibitors that show good pharmacokinetic profiles and are orally bioavailable. The targeting of these inhibitors to TAM is now more feasible using nanocarriers that are functionalized for a directed delivery. This review discusses the role of CatS in the immunological tumor microenvironment and upcoming possibilities for a nanocarrier-mediated delivery of potent and selective CatS inhibitors to TAM and related APC to promote anti-tumor immunity.

The liver injury following ischemia and reperfusion is worse in experimental knockout heterozygote mouse model for expression of connexin 431

PURPOSE

To evaluate that Connexin (Cx43) plays a role in lesions after hepatic ischemia/reperfusion (IR) injury.

METHODS

We use Cx43 deficient model (heterozygotes mice) and compared to a wild group. The groups underwent 1 hour ischemia and 24 hours reperfusion. The heterozygote genotype was confirmed by PCR. We analyzed the hepatic enzymes (AST, ALT, GGT) and histology.

RESULTS

The mice with Cx43 deficiency showed an ALT mean value of 4166 vs. 307 in the control group (p<0.001); AST mean value of 7231 vs. 471 in the control group (p<0.001); GGT mean value of 9.4 vs. 1.7 in the control group (p=0.001); histology showed necrosis and inflammation in the knockout group.

CONCLUSIONS

This research demonstrated that the deficiency of Cx43 worses the prognosis for liver injury. The topic is a promising target for therapeutics advancements in liver diseases and procedures.

A Novel Role for Cathepsin S as a Potential Biomarker in Triple Negative Breast Cancer

Cathepsin S (CTSS) has previously been implicated in a number of cancer types, where it is associated with poor clinical features and outcome. To date, patient outcome in breast cancer has not been examined with respect to this protease. Here, we carried out immunohistochemical (IHC) staining of CTSS using a breast cancer tissue microarray in patients who received adjuvant therapy. We scored CTSS expression in the epithelial and stromal compartments and evaluated the association of CTSS expression with matched clinical outcome data. We observed differences in outcome based on CTSS expression, with stromal-derived CTSS expression correlating with a poor outcome and epithelial CTSS expression associated with an improved outcome. Further subtype characterisation revealed high epithelial CTSS expression in TNBC patients with improved outcome, which remained consistent across two independent TMA cohorts. Further in silico gene expression analysis, using both in-house and publicly available datasets, confirmed these observations and suggested high CTSS expression may also be beneficial to outcome in ER-/HER2+ cancer. Furthermore, high CTSS expression was associated with the BL1 Lehmann subgroup, which is characterised by defects in DNA damage repair pathways and correlates with improved outcome. Finally, analysis of matching IHC analysis reveals an increased M1 (tumour destructive) polarisation in macrophage in patients exhibiting high epithelial CTSS expression. In conclusion, our observations suggest epithelial CTSS expression may be prognostic of improved outcome in TNBC. Improved outcome observed with HER2+ at the gene expression level furthermore suggests CTSS may be prognostic of improved outcome in ER- cancers as a whole. Lastly, from the context of these patients receiving adjuvant therapy and as a result of its association with BL1 subgroup CTSS may be elevated in patients with defects in DNA damage repair pathways, indicating it may be predictive of tumour sensitivity to DNA damaging agents.

Inhibitory Covalent Labeling and Clickable-Eu-Tagging-Based ICPMS: Measurement of pH-Dependent Absolute Activities of the Cathepsins in Hepatocyte Lysosomes

We report an inhibitory covalent labeling and clickable-element-tagging strategy for measuring the absolute activity of a protease in cells using inductively coupled plasma mass spectrometry (ICPMS). Epoxysuccinyl-leucine-tyrosine-6-aminocaproic-lysine-amino-Boc-alkyne (epoxysuccinyl-LYK-alkyne) was designed and synthesized to achieve irreversibly labeling of the cysteine cathepsins, recording their momentary activities. L and Y assisted epoxysuccinyl-LYK-alkyne in accessing the deprotonated -S^- of Cys25, located at the bottom of the long cathepsin active domain. Quantitative Eu-tagging was followed using azido-DOTA-Eu through a bioorthogonal 1:1 copper-catalyzed azide-alkyne-cycloaddition click reaction. The Eu tag could be absolutely quantified using ¹⁵³Eu-species-nonspecific-isotope-dilution ICPMS coupled with HPLC, serving as a Eu ruler and allowing us to simultaneously measure the pH-dependent activities of cathepsins B, L, and S as well as the pH in the lysosomal microenvironment of liver cancerous C7721 and paracancerous C7701 cells. As long as suitable labeling molecules and elemental tags are designed and synthesized, we believe that such a tandem labeling and tagging ICPMS approach can be applied to the measurement of the activities of other proteases in cells, providing more accurate information on the proteases' biofunctions and thus implementing precise clinical diagnoses.

Melittin Induced G1 Cell Cycle Arrest and Apoptosis in Chago-K1 Human Bronchogenic Carcinoma Cells and Inhibited the Differentiation of THP-1 Cells into Tumour- Associated Macrophages

Background: Bronchogenic carcinoma (lung cancer) is one of the leading causes of death. Although many compounds isolated from natural products have been used to treat it, drug resistance is a serious problem, and alternative anti-cancer drugs are required. Here, melittin from Apis mellifera venom was used, and its effects on bronchogenic carcinoma cell proliferation and tumour-associated macrophage differentiation were evaluated. Methods: The half maximal inhibitory concentration (IC50) of melittin was measured by MTT. Cell death was observed by annexin V and propidium iodide (PI) co-staining followed by flow cytometry. Cell cycle arrest was revealed by PI staining and flow cytometry. To investigate the tumour microenvironment, differentiation of circulating monocytes (THP-1) into tumour-associated macrophages (TAMs) was assayed by sandwich-ELISA and interleukin (IL)-10 levels were determined. Cell proliferation and migration was observed by flat plate colony formation. Secretion of vascular endothelial growth factor (VEGF) was detected by ELISA. The change in expression levels of CatS, Bcl-2, and MADD was measured by quantitative RT-PCR. Results: Melittin was significantly more cytotoxic (p < 0.01) to human bronchogenic carcinoma cells (ChaGo-K1) than to the control human lung fibroblasts (Wi-38) cells. At 2.5 μM, melittin caused ChaGo-K1 cells to undergo apoptosis and cell cycle arrest at the G1 phase. The IL-10 levels showed that melittin significantly inhibited the differentiation of THP-1 cells into TAMs (p < 0.05) and reduced the number of colonies formed in the treated ChaGo-K1 cells compared to the untreated cells. However, melittin did not affect angiogenesis in ChaGo-K1 cells. Unlike MADD, Bcl-2 was up-regulated significantly (p < 0.05) in melittin-treated ChaGo-K1 cells. Conclusion: Melittin can be used as an alternative agent for lung cancer treatment because of its cytotoxicity against ChaGo-K1 cells and the inhibition of differentiation of THP-1 cells into TAMs.

Z-FL-COCHO, a cathepsin S inhibitor, enhances oxaliplatin-mediated apoptosis through the induction of endoplasmic reticulum stress

Multiple cancer cells highly express cathepsin S, which has pro-tumoral effects. However, it was previously unknown whether knockdown or a pharmacological inhibitor (ZFL) of cathepsin S acts as an inducer of ER stress. Here, ZFL and knockdown of cathepsin S markedly induced ER stress through the up-regulation of calcium levels in the cytosol. Induction of calcium levels by inhibition of cathepsin S is markedly blocked by an inhibitor of the IP3 receptor and the ryanodine receptor Ca²⁺ channel in the ER, but an inhibitor of a mitochondrial Ca²⁺ uniporter had no effect on ZFL-induced calcium levels. Furthermore, production of mitochondrial ROS by ZFL was associated with an increase in cytosolic calcium levels. ZFL-mediated ER stress enhanced anti-cancer drug-induced apoptotic cell death, and pretreatment with chemical chaperones or down-regulation of ATF4 and CHOP by small interfering RNA markedly reduced ZFL plus oxaliplatin-induced apoptosis. Taken together, our findings reveal that inhibition of cathepsin S is an inducer of ER stress; these findings may contribute to the enhancement of therapeutic efficiency in cancer cells.

A drug that inhibits a key cancer enzyme could be used in combination with anti-cancer drugs to improve sensitivity to treatment. The intracellular endoplasmic reticulum (ER) is involved in several vital processes in cells, including folding and processing proteins. Taeg Kyu Kwon at Keimyung University, Daegu, South Korea, and co-workers have demonstrated how inhibition of cathepsin S, which is expressed in many cancer cells, induces ER stress. In trials on human kidney cancer cells grafted onto mice and in vitro, the team found that ZFL (cathepsin S inhibitor) triggered transient ER stress by increasing calcium levels inside cells. Subsequent treatment with the anti-cancer drug oxaliplatin resulted in increased cancer cell death.

Evaluating the diagnostic and prognostic value of circulating cathepsin S in gastric cancer

To evaluate whether serum Cathepsin S (Cat S) could serve as a biomarker for the diagnosis and prognosis of gastric cancer (GC), Enzyme-linked immuno sorbent assay (ELISA) was used to detect serum Cat S in 496 participants including healthy controls and patients with benign gastric diseases, gastric cancer, esophageal cancer, liver cancer, colorectal cancer, nasopharyngeal cancer and lung cancer. The levels of serum Cat S were significantly increased in cancer patients, especially in GC patients. The qRT-PCR, Western blotting, and immunohistochemical staining revealed the overexpression of Cat S in GC cell lines and tissues. The diagnostic value of serum Cat S for GC patients from controls resulted in an AUC of 0.803 with a sensitivity of 60.7% and a specificity of 90.0%. Moreover, the levels of serum Cat S were associated with GC tumor volume, lymphoid nodal status, metastasis status, and stages. Moreover, the patients with high levels of serum Cat S had a poorer overall survival. Univariate analysis revealed Cat S expression was a prognostic factor. The knockdown of Cat S significantly suppressed the migration and invasion of GC cells. This study suggested serum Cat S may be a potential biomarker for the diagnosis and prognosis of GC.

Long-term endurance training increases serum cathepsin S levels in healthy female subjects

BACKGROUND

Circulating cathepsin S (CS) has been associated with a lower risk for breast cancer in a large Swedish cohort. Long-term physical activity has been shown to have beneficial effects on the development of various cancer subtypes, in particular breast and colorectal cancers. The aim of this study was to investigate the effect of long-term endurance sport on CS levels in females.

MATERIAL AND METHODS

Thirty-six of 40 subjects completed the study. Subjects were told to increase their activity pensum for 8 months reaching 150 min/week moderate or 75 min/week intense exercise. Ergometries were performed at the beginning and the end of the study to prove/quantify the performance gain. Blood samples were drawn at baseline and every 2 months. Serum CS levels were measured by ELISA. To analyse the change and the progression of CS, Wilcoxon rank sum and Friedman tests were used.

RESULTS

The sportive group (performance gain by > 4.9%) showed a significant increase of CS levels from 3.32/2.73/4.09 to 4.00/3.09/5.04 ng/ml (p = 0.008) corresponding to an increase of 20.5%.

CONCLUSIONS

We could show a significant increase of circulating CS levels in healthy female subjects induced by long-term physical activity. CS, occurring in the tumour microenvironment, is well-known to promote tumour growth, e.g. by ameliorating angiogenesis. However, the role of circulating CS in cancer growth is not clear. As physical activity is known as preventive intervention, in particular concerning breast and colorectal cancers, and long-term physical activity leads to an increase of CS levels in female subjects, circulating CS might even be involved in this protective effect.

TRIAL REGISTRATION

Clinical trial registration: NCT02097199.

Inhibition of cathepsin S confers sensitivity to methyl protodioscin in oral cancer cells via activation of p38 MAPK/JNK signaling pathways

Oral cancer is one of the most common cancers in the world. Approximately 90% of oral cancers are subtyped to oral squamous cell carcinoma (OSCC). Despite advances in diagnostic techniques and improvement in treatment modalities, the prognosis remains poor. Therefore, an effective chemotherapy mechanism that enhances tumor sensitivity to chemotherapeutics is urgently needed. Methyl protodioscin (MP) is a furostanol bisglycoside with a wide range of beneficial effects, including anti-inflammatory and anti-cancer properties. The aim of the present study was to determine the antitumor activity of MP on OSCC and its underlying mechanisms. Our results show that treatment of OSCC cells with MP potently inhibited cell viability. Moreover, MP leading to cell cycle arrest at G2/M phase, which subsequently activates caspase-3, -8, -9 and PARP to induce cell apoptosis. Meanwhile, we also demonstrate that MP induces a robust autophagy in OSCC cells. The results indicate cathepsin S (CTSS) is involved in MP-induced apoptosis and autophagy by modulation of p38 MAPK and JNK1/2 pathways. These findings may provide rationale to combine MP with CTSS blockade for the effective treatment of OSCC.

Cathepsin S attenuates endosomal EGFR signalling: A mechanical rationale for the combination of cathepsin S and EGFR tyrosine kinase inhibitors

EGF-mediated EGFR endocytosis plays a crucial role in the attenuation of EGFR activation by sorting from early endosomes to late endosomes and transporting them into lysosomes for the final proteolytic degradation. We previously observed that cathepsin S (CTSS) inhibition induces tumour cell autophagy through the EGFR-mediated signalling pathway. In this study, we further clarified the relationship between CTSS activities and EGFR signalling regulation. Our results revealed that CTSS can regulate EGFR signalling by facilitating EGF-mediated EGFR degradation. CTSS inhibition delayed the EGFR degradation process and caused EGFR accumulation in the late endosomes at the perinuclear region, which provides spatial compartments for prolonged EGFR and sustained downstream signal transducer and activator of transcription 3 and AKT signalling. Notably, cellular apoptosis was markedly enhanced by combining treatment with the EGFR inhibitor Iressa and CTSS inhibitor 6r. The data not only reveal a biological role of CTSS in EGFR signalling regulation but also evidence a rationale for its clinical evaluation in the combination of CTSS and EGFR tyrosine kinase inhibitors.

A bioavailable cathepsin S nitrile inhibitor abrogates tumor development

Background

Cathepsin S has been implicated in a variety of malignancies with genetic ablation studies demonstrating a key role in tumor invasion and neo-angiogenesis. Thus, the application of cathepsin S inhibitors may have clinical utility in the treatment of cancer. In this investigation, we applied a cell-permeable dipeptidyl nitrile inhibitor of cathepsin S, originally developed to target cathepsin S in inflammatory diseases, in both in vitro and in vivo tumor models.

Methods

Validation of cathepsin S selectivity was carried out by assaying fluorogenic substrate turnover using recombinant cathepsin protease. Complete kinetic analysis was carried out and true K_i values calculated. Abrogation of tumour invasion using murine MC38 and human MCF7 cell lines were carried out in vitro using a transwell migration assay. Effect on endothelial tube formation was evaluated using primary HUVEC cells. The effect of inhibitor in vivo on MC38 and MCF7 tumor progression was evaluated using cells propagated in C57BL/6 and BALB/c mice respectively. Subsequent immunohistochemical staining of proliferation (Ki67) and apoptosis (TUNEL) was carried out on MCF7 tumors.

Results

We confirmed that this inhibitor was able to selectively target cathepsin S over family members K, V, L and B. The inhibitor also significantly reduced MC38 and MCF7 cell invasion and furthermore, significantly reduced HUVEC endothelial tubule formation in vitro. In vivo analysis revealed that the compound could significantly reduce tumor volume in murine MC38 syngeneic and MCF7 xenograft models. Immunohistochemical analysis of MCF7 tumors revealed cathepsin S inhibitor treatment significantly reduced proliferation and increased apoptosis.

Conclusions

In summary, these results highlight the characterisation of this nitrile cathepsin S inhibitor using in vitro and in vivo tumor models, presenting a compound which may be used to further dissect the role of cathepsin S in cancer progression and may hold therapeutic potential.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-016-0513-7) contains supplementary material, which is available to authorized users.

Melittin suppresses cathepsin S-induced invasion and angiogenesis via blocking of the VEGF-A/VEGFR-2/MEK1/ERK1/2 pathway in human hepatocellular carcinoma

Melittin, a significant constituent of Apis mellifera (honeybee) venom, is a water-soluble toxic peptide that has traditionally been used as an antitumor agent. However, the underlying mechanisms by which it inhibits tumor cell growth and angiogenesis remain to be elucidated. In the present study, screening for increased cathepsin S (Cat S) expression levels was performed in MHCC97-H cells and various other hepatocellular carcinoma cell lines by reverse transcription-polymerase chain reaction and western blot analysis. A pcDNA3.1-small hairpin RNA (shRNA)-Cat S vector was stably transfected into MHCC97-H cells (shRNA/MHCC97-H) in order to knockdown the expression of Cat S. The effects resulting from the inhibition of Cat S-induced proliferation, invasion and angiogenesis by melittin were examined using cell proliferation, cell viability, flat plate colony formation, migration, wound healing, Transwell migration and ELISA assays. In order to substantiate the evidence for melittin-mediated inhibition of Cat S-induced angiogenesis, Cat S RNA was transfected into primary human umbilical vein endothelial cells (Cat S-HUVECs) to induce overexpression of the Cat S gene. The effects of melittin on HUVECs were examined using Transwell migration and tube formation assays. The findings demonstrated that melittin was able to significantly suppress MHCC97-H cell (Mock/MHCC97-H) proliferation, invasion and angiogenesis, as well as capillary tube formation of Cat S-HUVECs, in a dose-dependent manner. However, proliferation, invasion and angiogenesis in shRNA/MHCC97-H and in native HUVECs (Mock-HUVECs) were unaffected. In addition, melittin specifically decreased the expression of phosphorylated (activated) Cat S, and components of the vascular endothelial growth factor (VEGF)-A/VEGF receptor 2 (VEGFR-2)/mitogen-activated protein kinase kinase 1 (MEK1)/extracellular signal-regulated kinase (ERK)1/2 signaling pathway in Mock/MHCC97-H cells. In conclusion, the inhibition of tumor cell growth and anti-angiogenic activity exerted by melittin may be associated with anti-Cat S actions, via the inhibition of VEGF-A/VEGFR-2/MEK1/ERK1/2 signaling.

Autophagy-Regulated ROS from Xanthine Oxidase Acts as an Early Effector for Triggering Late Mitochondria-Dependent Apoptosis in Cathepsin S-Targeted Tumor Cells

Cathepsin S (CTSS), which is highly expressed in various malignant tumor cells, has been proposed to promote tumor progression, migration, and invasion. CTSS inhibition not only blocks tumor cell invasion and endothelial tube formation but also induces cellular cytotoxicity. In our previous studies, we have observed that CTSS inhibition induces autophagy, which is responsible for up-regulating xanthine oxidase for early ROS generation and consequent cell death. However, whether the autophagy-regulated early ROS triggers apoptosis remains unclear. We conducted a long-term follow-up study to investigate the relationship between early autophagy and late mitochondria-dependent apoptosis. We demonstrated that early ROS generation is critical for mitochondria damage and the activation of intrinsic apoptotic pathway. Attenuating the early ROS level diminished later mitochondrial damage and downstream apoptotic signaling. Collectively, mitochondria-dependent apoptosis is regulated by autophagy-regulated early ROS, which serves as an early effector that triggers mitochondrial signaling for late apoptosis. The data emphasize the essential role of autophagy-regulated early ROS in triggering late apoptotic signaling.

The role of Cathepsin S as a marker of prognosis and predictor of chemotherapy benefit in adjuvant CRC: a pilot study

Background:

The aim of this pilot retrospective study was to investigate the immunohistochemical expression of Cathepsin S (CatS) in three cohorts of colorectal cancer (CRC) patients (n=560).

Methods:

Prevalence and association with histopathological variables were assessed across all cohorts. Association with clinical outcomes was investigated in the Northern Ireland Adjuvant Chemotherapy Trial cohort (n=211), where stage II/III CRC patients were randomised between surgery-alone or surgery with adjuvant fluorouracil/folinic acid (FU/FA) treatment.

Results:

Greater than 95% of tumours had detectable CatS expression with significantly increased staining in tumours compared with matched normal colon (P>0.001). Increasing CatS was associated with reduced recurrence-free survival (RFS; P=0.03) among patients treated with surgery alone. Adjuvant FU/FA significantly improved RFS (hazard ratio (HR), 0.33; 95% CI, 0.12–0.89) and overall survival (OS; HR, 0.25; 95% CI, 0.08–0.81) among 36 patients with high CatS. Treatment did not benefit the 66 patients with low CatS, with a RFS HR of 1.34 (95% CI, 0.60–3.19) and OS HR of 1.33 (95% CI, 0.56–3.15). Interaction between CatS and treatment status was significant for RFS (P=0.02) and OS (P=0.04) in a multivariate model adjusted for known prognostic markers.

Conclusion:

These results signify that CatS may be an important prognostic biomarker and predictive of response to adjuvant FU/FA in CRC.