Suppression of asparaginyl endopeptidase attenuates breast cancer-induced bone pain through inhibition of neurotrophin receptors

Oral Cancer Cells Release Vesicles that Cause Pain

Oral cancer pain is attributed to the release from cancers of mediators that sensitize and activate sensory neurons. Intraplantar injection of conditioned media (CM) from human tongue cancer cell line HSC-3 or OSC-20 evokes nociceptive behavior. By contrast, CM from noncancer cell lines, DOK, and HaCaT are non-nociceptive. Pain mediators are carried by extracellular vesicles (EVs) released from cancer cells. Depletion of EVs from cancer cell line CM reverses mechanical allodynia and thermal hyperalgesia. CM from non-nociceptive cell lines become nociceptive when reconstituted with HSC-3 EVs. Two miRNAs (hsa-miR-21-5p and hsa-miR-221-3p) are identified that are present in increased abundance in EVs from HSC-3 and OSC-20 CM compared to HaCaT CM. The miRNA target genes suggest potential involvement in oral cancer pain of the toll like receptor 7 (TLR7) and 8 (TLR8) pathways, as well as signaling through interleukin 6 cytokine family signal transducer receptor (gp130, encoded by IL6ST) and colony stimulating factor receptor (G-CSFR, encoded by CSF3R), Janus kinase and signal transducer and activator of transcription 3 (JAK/STAT3). These studies confirm the recent discovery of the role of cancer EVs in pain and add to the repertoire of algesic and analgesic cancer pain mediators and pathways that contribute to oral cancer pain.

C/EBPβ/AEP Signaling Regulates the Oxidative Stress in Malignant Cancers, Stimulating the Metastasis

Solid tumors start as a local disease, but some are capable of metastasizing to the lymph nodes and distant organs. The hypoxic microenvironment, which is critical during cancer development, plays a key role in regulating cancer progression and metastasis. However, the molecular mechanisms mediating the disseminated cancer cell metastasis remain incompletely understood. Here, we show that C/EBPβ/AEP signaling that is upregulated in breast cancers mediates oxidative stress and lung metastasis, and inactivation of asparagine endopeptidase (AEP, also known as legumain) robustly regulates breast cancer reactive oxygen species (ROS) and metastasis. AEP, a protease activated in acidic conditions, is overexpressed in numerous types of cancer and promotes metastasis. Employing a breast cancer cell line MDA-MD-231, we show that C/EBPβ, an oxidative stress or inflammation-activated transcription factor, and its downstream target AEP mediate ROS production as well as migration and invasion in cancer cells. Deficiency of AEP in the MMTV-PyMT transgenic breast cancer mouse model significantly regulates oxidative stress and suppresses lung metastasis. Administration of an innovative AEP inhibitor substantially mitigates ROS production and cancer metastasis. Hence, our study demonstrates that pharmacologic inhibition of AEP activity might provide a disease-modifying strategy to suppress cancer metastasis.

Usefulness of the measurement of neurite outgrowth of primary sensory neurons to study cancer-related painful complications

Abnormal outgrowth of sensory nerves is one of the important contributors to pain associated with cancer and its treatments. Primary neuronal cultures derived from dorsal root ganglia (DRG) have been widely used to study pain-associated signal transduction and electrical activity of sensory nerves. However, there are only a few studies using primary DRG neuronal culture to investigate neurite outgrowth alterations due to underlying cancer-related factors and chemotherapeutic agents. In this study, primary DRG sensory neurons derived from mouse, non-human primate, and human were established in serum and growth factor-free conditions. A bovine serum albumin gradient centrifugation method improved the separation of sensory neurons from satellite cells. The purified DRG neurons were able to maintain their heterogeneous subpopulations, and displayed an increase in neurite growth when exposed to cancer-derived conditioned medium, while they showed a reduction in neurite length when treated with a neurotoxic chemotherapeutic agent. Additionally, a semi-automated quantification method was developed to measure neurite length in an accurate and time-efficient manner. Finally, these exogenous factors altered the gene expression patterns of murine primary sensory neurons, which are related to nerve growth, and neuro-inflammatory pain and nociceptor development. Together, the primary DRG neuronal culture in combination with a semi-automated quantification method can be a useful tool for further understanding the impact of exogenous factors on the growth of sensory nerve fibers and gene expression changes in sensory neurons.

GDI2 is a target of paclitaxel that affects tumorigenesis of prostate cancer via the p75NTR signaling pathway

BACKGROUND

Prostate cancer (PCa) refers to malignant tumors derived from prostate epithelial cells, whose morbidity and mortality rates have been increasing every year. Although new drugs for treating prostate cancer continue to emerge, the unclear mechanism underlying drug targets limits this therapy, thereby constraining identification of effective therapeutic targets. Although GDP dissociation inhibitor 2(GDI2) is highly expressed and closely associated with occurrence and development of many tumors, its role in prostate cancer remains unclear. In this study, we investigated the role of GDI2 and elucidated its underlying mechanism of action in prostate cancer. Moreover, we screened chemotherapeutic drugs that affect GDI2 expression with a view of identifying novel targets for diagnosis and treatment of prostate cancer.

METHODS

We performed sequence analyses and functional assays to precisely elucidate the GDI2 role in prostate cancer. Moreover, we induced tumorigenesis in nude mice to verify the role of GDI2 in vivo. Finally, we used the CCK8 assay to ascertain the most suitable IC₅₀ across the three drugs and performed quantitative real time polymerase chain reaction (qRT-PCR) and Western Blot to analyze the effects of drugs on expression of GDI2, p75NTR, and p-NFκB.

RESULTS

GDI2 was up-regulated in prostate cancer cells and tissues. Knocking down GDI2 suppressed cell proliferation but promoted cell apoptosis. Interestingly, knocking down GDI2 activated the p75NTR signaling pathway, indicating, for the first time, that p75NTR is negatively correlated with GDI2 expression.

CONCLUSION

Taken together, these results indicate that GDI2 is a therapeutic target of paclitaxel. Knocking down of GDI2 inhibits cell proliferation and promotes cell apoptosis via the p75NTR signaling pathway in prostate cancer. Notably, paclitaxel inhibits GDI2 expression, implying that GDI2 may be a promising therapeutic target in prostate cancer.

Target Enzymes Considered for the Treatment of Alzheimer's Disease and Parkinson's Disease

Various amyloidogenic proteins have been suggested to be involved in the onset and progression of neurodegenerative diseases (ND) such as Alzheimer's disease (AD) and Parkinson's disease (PD). Particularly, the aggregation of misfolded amyloid-β and hyperphosphorylated tau and α-synuclein are linked to the pathogenesis of AD and PD, respectively. In order to care the diseases, multiple small molecules have been developed to regulate the aggregation pathways of these amyloid proteins. In addition to controlling the aggregation of amyloidogenic proteins, maintaining the levels of the proteins in the brain by amyloid degrading enzymes (ADE; neprilysin (NEP), insulin-degrading enzyme (IDE), asparagine endopeptidase (AEP), and ADAM10) is also essential to cure AD and PD. Therefore, numerous biological molecules and chemical agents have been investigated as either inducer or inhibitor against the levels and activities of ADE. Although the side effect of enhancing the activity of ADE could occur, the removal of amyloidogenic proteins could result in a relatively good strategy to treat AD and PD. Furthermore, since the causes of ND are diverse, various multifunctional (multitarget) chemical agents have been designed to control the actions of multiple risk factors of ND, including amyloidogenic proteins, metal ions, and reactive oxygen species. Many of them, however, were invented without considerations of regulating ADE levels and actions. Incorporation of previously created molecules with the chemical agents handling ADE could be a promising way to treat AD and PD. This review introduces the ADE and molecules capable of modulating the activity and expression of ADE.

Legumain Induces Oral Cancer Pain by Biased Agonism of Protease-Activated Receptor-2

Oral squamous cell carcinoma (OSCC) is one of the most painful cancers, which interferes with orofacial function including talking and eating. We report that legumain (Lgmn) cleaves protease-activated receptor-2 (PAR₂) in the acidic OSCC microenvironment to cause pain. Lgmn is a cysteine protease of late endosomes and lysosomes that can be secreted; it exhibits maximal activity in acidic environments. The role of Lgmn in PAR₂-dependent cancer pain is unknown. We studied Lgmn activation in human oral cancers and oral cancer mouse models. Lgmn was activated in OSCC patient tumors, compared with matched normal oral tissue. After intraplantar, facial or lingual injection, Lgmn evoked nociception in wild-type (WT) female mice but not in female mice lacking PAR₂ in Na_V1.8-positive neurons (Par₂Na_v1.8), nor in female mice treated with a Lgmn inhibitor, LI-1. Inoculation of an OSCC cell line caused mechanical and thermal hyperalgesia that was reversed by LI-1. Par₂Na_v1.8 and Lgmn deletion attenuated mechanical allodynia in female mice with carcinogen-induced OSCC. Lgmn caused PAR₂-dependent hyperexcitability of trigeminal neurons from WT female mice. Par₂ deletion, LI-1, and inhibitors of adenylyl cyclase or protein kinase A (PKA) prevented the effects of Lgmn. Under acidified conditions, Lgmn cleaved within the extracellular N terminus of PAR₂ at Asn³⁰↓Arg³¹, proximal to the canonical trypsin activation site. Lgmn activated PAR₂ by biased mechanisms in HEK293 cells to induce Ca²⁺ mobilization, cAMP formation, and PKA/protein kinase D (PKD) activation, but not β-arrestin recruitment or PAR₂ endocytosis. Thus, in the acidified OSCC microenvironment, Lgmn activates PAR₂ by biased mechanisms that evoke cancer pain.SIGNIFICANCE STATEMENT Oral squamous cell carcinoma (OSCC) is one of the most painful cancers. We report that legumain (Lgmn), which exhibits maximal activity in acidic environments, cleaves protease-activated receptor-2 (PAR₂) on neurons to produce OSCC pain. Active Lgmn was elevated in OSCC patient tumors, compared with matched normal oral tissue. Lgmn evokes pain-like behavior through PAR₂ Exposure of pain-sensing neurons to Lgmn decreased the current required to generate an action potential through PAR₂ Inhibitors of adenylyl cyclase and protein kinase A (PKA) prevented the effects of Lgmn. Lgmn activated PAR₂ to induce calcium mobilization, cAMP formation, and activation of protein kinase D (PKD) and PKA, but not β-arrestin recruitment or PAR₂ endocytosis. Thus, Lgmn is a biased agonist of PAR₂ that evokes cancer pain.

Down-Regulation of NOX4 Expression in Dorsal Horn of Spinal Cord Could Alleviate Cancer-Induced Bone Pain in Rats by Reducing Oxidative Stress Response

Introduction

Cancer-induced bone pain (CIBP) is very common in patients with advanced cancer. Recent studies have shown that reactive oxygen species (ROS) can sense and regulate pain response process through spinal cord mechanism, and play a role in CIBP. NADPH oxidase (NOX) is a group of protease complexes that produce ROS. In the current study, we investigated the expression of NOX4 in the spinal dorsal horn of rats with CIBP and its related role and molecular mechanism.

Materials and Methods

A rat CIBP model was established by injecting Walker-256 cells into the tibia medullary cavity, and the expression of NOX4 in spinal dorsal horn was down-regulated by injecting lentivirus into spinal cord. RT-PCR, Western blot and immunofluorescence staining were used to detect the expression of NOX4 in CIBP rats, cell localization and its effect on CIBP rats, and the effect of down-regulating the expression of NOX4 on the expression of H₂O₂, nitric oxide synthase nNO, antioxidant enzyme SOD, and the activity of neuro-receptor in spinal dorsal horn of rats.

Results

In rats with CIBP, the expression of NOX4 was significantly increased, and immunofluorescence showed that NOX4 was mainly expressed in microglia in the dorsal horn of spinal cord. Down-regulating the expression of NOX4 in rats can reduce the level of H₂O₂ and nNO in dorsal horn tissue, and increase the expression of SOD to reduce the oxidative stress response. At the same time, down-regulating NOX4 can reduce the sensitivity of spinal cord and relieve the pain of bone cancer by inhibiting the expression of NMDAR and GABAA-γ2 in dorsal horn tissue.

Conclusion

NOX4 is a promising therapeutic target in CIBP, and down-regulation of NOX4 expression can alleviate CIBP in rats by reducing oxidative stress and weakening spinal cord sensitization.

The LGMN pseudogene promotes tumor progression by acting as a miR-495-3p sponge in glioblastoma

Pseudogenes, which are long noncoding RNAs that originate from protein-coding genes, have been suggested to play important roles in disease. Although studies have revealed high expression of legumain (LGMN) in many types of tumors, the regulation of LGMN remains largely unknown. Here, we found that a novel LGMN pseudogene (LGMNP1) was upregulated in glioblastoma (GBM) tissues and high LGMNP1 expression in GBM cells enhanced proliferation and invasion. Biochemical analysis showed that cytoplasmic LGMNP1 functionally targeted miR-495-3p in a manner involving an RNA-induced silencing complex. Dual-luciferase reporter assays demonstrated that LGMN was a target of miR-495-3p, and LGMN was upregulated and positively correlated with LGMNP1 in GBM. Moreover, miR-495-3p was downregulated and negatively correlated with LGMNP1 in GBM tissues. Notably, the tumor-promoting effects of LGMNP1 upregulation could be alleviated by miR-495-3p mimics. Furthermore, GBM cells overexpressing LGMNP1 exhibited more aggressive tumor progression and elevated LGMN expression in vivo. Thus, our data illustrate that LGMNP1 exerts its oncogenic activity, at least in part, as a competitive endogenous RNA (ceRNA) that elevates LGMN expression by sponging miR-495-3p. CeRNA-mediated miRNA sequestration might be a novel therapeutic strategy in GBM.

Low‑affinity neurotrophin receptor p75 of brain‑derived neurotrophic factor contributes to cancer‑induced bone pain by upregulating mTOR signaling

Crucial to the development and maintenance of pain sensations is neurotrophin receptor p75 (p75^NTR), the low affinity receptor of brain-derived neurotrophic factor (BDNF). This receptor is widespread among dorsal root ganglion (DRG) neurons and the spinal cord. Few reports have demonstrated the specific role of p75^NTR in the development of cancer-induced bone pain (CIBP). Therefore the present study examined whether p75^NTR contributed to CIBP by upregulating mammalian target of rapamycin (mTOR) signaling. A CIBP rat model was induced and reverse transcription-quantitative polymerase chain reaction was employed to determine p75^NTR and mTOR mRNA expression. Immunofluorescence analysis was performed to determine the coexpression of p75^NTR and mTOR in DRG neurons, as well as the spinal cord. Von Frey filaments were used to measure the 50% likelihood of paw withdrawal thresholds (PWTs). Spontaneous pain was assessed by ambulatory score. The results demonstrated that compared with the control group, mTOR activation in primary cultured DRG neurons was significantly increased. In addition, mTOR and p75^NTR expression was significantly enhanced in the BDNF-treated primary DRG in the BDNF group. In vivo experiments determined that mTOR and p75^NTR levels were increased in the CIBP rats compared with the sham group. PWT, in response to mechanical stimulation, was significantly lower compared with that in sham rats and the ambulatory score was significantly higher than that in sham rats. Finally, intrathecal injection of a p75^NTR-targeting small interfering RNA significantly decreased mTOR and p75^NTR expression levels in DRG neurons and the spinal cord of CIBP rats, as well as partially reversing the decline in PWTs and the increase in ambulatory score. In conclusion, the present study determined that the activation of BDNF/p75^NTR/mTOR signaling may participate in nociceptive transmission in CIBP, suggesting a novel mechanism and potential therapeutic target for CIBP treatment and management.

Sinomenine attenuates cancer-induced bone pain via suppressing microglial JAK2/STAT3 and neuronal CAMKII/CREB cascades in rat models

Cancer-induced bone pain is one of the most severe types of pathological pain, which often occurs in patients with advanced prostate, breast, and lung cancer. It is of great significance to improve the therapies of cancer-induced bone pain due to the opioids' side effects including addiction, sedation, pruritus, and vomiting. Sinomenine, a traditional Chinese medicine, showed obvious analgesic effects on a rat model of chronic inflammatory pain, but has never been proven to treat cancer-induced bone pain. In the present study, we investigated the analgesic effect of sinomenine after tumor cell implantation and specific cellular mechanisms in cancer-induced bone pain. Our results indicated that single administration of sinomenine significantly and dose-dependently alleviated mechanical allodynia in rats with cancer-induced bone pain and the effect lasted for 4 h. After tumor cell implantation, the protein levels of phosphorylated-Janus family tyrosine kinase 2 (p-JAK2), phosphorylated-signal transducers and activators of transcription 3 (p-STAT3), phosphorylated-Ca2+/calmodulin-dependent protein kinase II (p-CAMKII), and phosphorylated-cyclic adenosine monophosphate response element-binding protein (p-CREB) were persistently up-regulated in the spinal cord horn. Chronic intraperitoneal treatment with sinomenine markedly suppressed the activation of microglia and effectively inhibited the expression of JAK2/STAT3 and CAMKII/CREB signaling pathways. We are the first to reveal that up-regulation of microglial JAK2/STAT3 pathway are involved in the development and maintenance of cancer-induced bone pain. Moreover, our investigation provides the first evidence that sinomenine alleviates cancer-induced bone pain by inhibiting microglial JAK2/STAT3 and neuronal CAMKII/CREB cascades.