Effect of κ-opioid receptor agonist on the growth of non-small cell lung cancer (NSCLC) cells

Mu and Kappa opioid receptor immunolabeling indicates the prognosis of oropharyngeal squamous cell carcinoma: A cross-sectional observational study

BACKGROUND

Opioids are the most effective drugs currently available for cancer pain management. The administration of morphine, in addition to its analgesic effect, can alter tumor development.

OBJECTIVE

To characterize the immunoexpression of opioid receptors µ and κ in oropharyngeal squamous cell carcinoma, and correlate it with prognostic factors, proliferation markers, and cell death.

MATERIALS AND METHODS

A retrospective, cross-sectional observational study was carried out with 50 patients diagnosed at Haroldo Juaçaba Hospital. Sociodemographic, clinicopathological, and overall survival data were collected, and excisional biopsies were taken for immunohistochemistry using tissue microarrays for opioid receptors µ and κ, Ki-67, and caspase-3. Immunolabeling was evaluated and correlated with other variables using Mann-Whitney, Kruskal-Wallis, Spearman correlation, log-rank (Mantel-Cox), and Cox regression tests.

RESULTS

Immunoexpression of opioid receptors µ and κ, Ki-67, and caspase-3 was significantly higher in p16+ and p16- primary tumors and lymph node metastases than in surgical resection margins. The overall survival of patients with p16- tumors was 57.53 ± 8.43 months and that of patients with p16+ tumors was slightly higher at 75.92 ± 11.14 months. Multivariate analysis showed that the expression of opioid receptors µ and κ in the nucleus was directly associated with a lower and higher risk of death, respectively.

CONCLUSION

We found increased expression of opioid receptors µ and κ in tumor tissues. The nuclear expression of opioid receptors µ and κ influences overall survival and may be a prognostic factor of oropharyngeal squamous cell carcinoma.

Buprenorphine and methadone differentially alter early brain development in human cortical organoids

Buprenorphine (BUP) and methadone (MTD) are used for medication-assisted treatment (MAT) in opioid use disorder. Although both medications show improved maternal and neonatal outcomes compared with illicit opioid use during pregnancy, BUP has exhibited more favorable outcomes to newborns than MTD. The underlying cellular and molecular mechanisms for the difference between BUP and MTD are largely unknown. Here, we examined the growth and neuronal activity in human cortical organoids (hCOs) exposed to BUP or MTD. We found that the growth of hCOs was significantly restricted in the MTD-treated but not in the BUP-treated hCOs and BUP attenuated the growth-restriction effect of MTD in hCOs. Furthermore, a κ-receptor agonist restricted while an antagonist alleviated the growth-restriction effect of MTD in hCOs. Since BUP is not only a μ-agonist but a κ-antagonist, the prevention of this growth-restriction by BUP is likely due to its κ-receptor-antagonism. In addition, using multielectrode array (MEA) technique, we discovered that both BUP and MTD inhibited neuronal activity in hCOs but BUP showed suppressive effects only at higher concentrations. Furthermore, κ-receptor antagonist nBNI did not prevent the MTD-induced suppression of neuronal activity in hCOs but the NMDA-antagonism of MTD (that BUP lacks) plays a role in the inhibition of neuronal activity. We conclude that, although both MTD and BUP are μ-opioid agonists, a) the additional κ-receptor antagonism of BUP mitigates the MTD-induced growth restriction during neurodevelopment and b) the lack of NMDA antagonism of BUP (in contrast to MTD) induces much less suppressive effect on neural network communications.

Activation of kappa opioid receptor (KOR) inhibits estrogen receptor (ER)-positive breast cancer through the KOR-ER-XBP1 pathway

Opioids are commonly used in patients with breast cancer (BC), both for perioperative analgesia and for the relief of chronic cancer pain. Studies have suggested a potential association of opioid receptors (ORs) with the prognosis of BC patients. However, the exact roles of different ORs remain poorly understood. In this study, we found that κ opioid receptor (KOR) was the only OR (among the four types of ORs) that was significantly decreased in BC tumor tissues compared with peritumoral normal tissues. In addition, decreased expression of KOR correlated with poor clinical outcomes in patients with estrogen receptor (ER)-positive BC. In vitro studies confirmed the anti-tumor effects of KOR agonists in ER-positive MCF-7 and T47D cells by showing that activation of KOR significantly inhibited cellular proliferation and promoted apoptosis. Using Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and protein-protein interaction network (PPI) analysis, we found that KOR-ER-XBP1 was the potential downstream signaling pathway mediating the anti-tumor effects of KOR agonist. Finally, the role of XBP1 was confirmed as KOR activation-induced increase in the proliferative and monoclonal formation abilities of ER-positive BC cells were both significantly abolished after silencing of XBP1. These findings provide us a better understanding of the roles of different ORs in BC, identifying KOR agonists as better opioids than traditional μ opioid receptor (MOR) agonists for providing analgesia in ER-positive BC patients owing to their association with better prognosis.

Ion channels in lung cancer: biological and clinical relevance

Despite improvements in treatment, lung cancer is still a major health problem worldwide. Among lung cancer subtypes, the most frequent is represented by adenocarcinoma (belonging to the Non-Small Cell Lung Cancer class) although the most challenging and harder to treat is represented by Small Cell Lung Cancer, that occurs at lower frequency but has the worst prognosis. For these reasons, the standard of care for these patients is represented by a combination of surgery, radiation therapy and chemotherapy. In this view, searching for novel biomarkers that might help both in diagnosis and therapy is mandatory. In the last 30 years it was demonstrated that different families of ion channels are overexpressed in both lung cancer cell lines and primary tumours. The altered ion channel profile may be advantageous for diagnostic and therapeutic purposes since most of them are localised on the plasma membrane thus their detection is quite easy, as well as their block with specific drugs and antibodies. This review focuses on ion channels (Potassium, Sodium, Calcium, Chloride, Anion and Nicotinic Acetylcholine receptors) in lung cancer (both Non-Small Cell Lung Cancer and Small Cell Lung Cancer) and recapitulate the up-to-date knowledge about their role and clinical relevance for a potential use in the clinical setting, for lung cancer diagnosis and therapy.

Altered Membrane Expression and Function of CD11b Play a Role in the Immunosuppressive Effects of Morphine on Macrophages at the Nanomolar Level

Morphine, one of the most efficacious analgesics, is effective in severe pain, especially in patients with concomitant painful cancers. The clinical use of morphine may be accompanied by increased immunosuppression, susceptibility to infection and postoperative tumor metastatic recurrence, and the specific mechanisms and clinical strategies to alleviate this suppression remain to be investigated. Expression of CD11b is closely associated with the macrophage phagocytosis of xenobiotic particles, bacteria or tumor cells. Here, we find that morphine at 0.1-10 nM levels inhibited CD11b expression and function on macrophages via a μ-opioid receptor (MOR)-dependent mechanism, thereby reducing macrophage phagocytosis of tumor cells, a process that can be reversed by thymopentin (TP5), a commonly used immune-enhancing adjuvant in clinical practice. By knocking down or overexpressing MOR on macrophages and using naloxone, an antagonist of the MOR receptor, and LA1, a molecule that promotes macrophage CD11b activation, we suggest that morphine may regulate macrophage phagocytosis by inhibiting the surface expression and function of macrophage CD11b through the membrane expression and activation of MOR. The CD47/SIRPα axis, which is engaged in macrophage-tumor immune escape, was not significantly affected by morphine. Notably, TP5, when combined with morphine, reversed the inhibition of macrophage phagocytosis by morphine through mechanisms that promote membrane expression of CD11b and modulate its downstream signaling (e.g., NOS2, IFNG, IL1B and TNFA, as well as AGR1, PDGFB, IL6, STAT3, and MYC). Thus, altered membrane expression and function of CD11b may mediate the inhibition of macrophage phagocytosis by therapeutic doses of morphine, and the reversal of this process by TP5 may provide an effective palliative option for clinical immunosuppression by morphine.

Systemic immune effects of anesthetics and their intracellular targets in tumors

According to the result released by the World Health Organization (WHO), non-communicable diseases have occupied four of the top 10 current causes for death in the world. Cancer is one of the significant factors that trigger complications and deaths; more than 80% cancer patients require surgical or palliative treatment. In this case, anesthetic treatment is indispensable. Since cancer is a heterogeneous disease, various types of interventions can activate oncogenes or mutate tumor suppressor genes. More and more researchers believe that anesthetics have a certain effect on the long-term recurrence and metastasis of tumors, but it is still controversial whether they promote or inhibit the progression of cancer. On this basis, a series of retrospective or prospective randomized clinical trials have been conducted, but it seems to be difficult to reach a conclusion within 5 years or longer. This article focuses on the effects of anesthetic drugs on immune function and cancer and reviews their latest targets on the tumor cells, in order to provide a theoretical basis for optimizing the selection of anesthetic drugs, exploring therapeutic targets, and improving the prognosis of cancer patients.

The Kappa Opioid Receptor: A Promising Therapeutic Target for Multiple Pathologies

Kappa-opioid receptors (KOR) are widely expressed throughout the central nervous system, where they modulate a range of physiological processes depending on their location, including stress, mood, reward, pain, inflammation, and remyelination. However, clinical use of KOR agonists is limited by adverse effects such as dysphoria, aversion, and sedation. Within the drug-development field KOR agonists have been extensively investigated for the treatment of many centrally mediated nociceptive disorders including pruritis and pain. KOR agonists are potential alternatives to mu-opioid receptor (MOR) agonists for the treatment of pain due to their anti-nociceptive effects, lack of abuse potential, and reduced respiratory depressive effects, however, dysphoric side-effects have limited their widespread clinical use. Other diseases for which KOR agonists hold promising therapeutic potential include pruritis, multiple sclerosis, Alzheimer's disease, inflammatory diseases, gastrointestinal diseases, cancer, and ischemia. This review highlights recent drug-development efforts targeting KOR, including the development of G-protein-biased ligands, mixed opioid agonists, and peripherally restricted ligands to reduce side-effects. We also highlight the current KOR agonists that are in preclinical development or undergoing clinical trials.

Agonists Specific for κ-Opioid Receptor Induces Apoptosis of HCC Cells Through Enhanced Endoplasmic Reticulum Stress

Cancer pain is an important factor affecting life quality of patients especially in the advanced stage and relieving pain is one of fundamental strategies for cancer treatment. Opioids such as morphine are the most widely used in clinics. However, they have been reported to be associated with the occurrence and development of several types of cancer. Thus, search for an opioid that has analgesic effect and can retard cancer progress simultaneously is critical for cancer management. In this study, we first examined the expression of μ and κ (MOR and KOR) in cell lines and tumor tissues of hepatocellular carcinoma (HCC), a malignant tumor with high mortality, and then compared the effects of opioid receptors-specific agonists on malignant phenotypes of HCC cells in vitro and tumor growth in an HCC xenograft mouse model. KOR and MOR were found to be highly expressed in HCC cell lines and HCC tissues. The KOR-specific agonist U50488h, oxycodone (agonist for both KOR and MOR) and the MOR-specific agonist morphine inhibited HCC cell proliferation, while only U50488h and oxycodone suppressed colony formation and migration of HCC cells. U50488h and oxycodone, but not morphine, induced HCC apoptosis. Further detection of PERK, GRP78 and CHOP revealed that PERK signaling was upregulated by treatment with U50488h, while treatment with the PERK inhibitor GSK2656157 partially reversed the promotion of apoptosis and inhibition of cell proliferation by U50488h, indicating that endoplasmic reticulum stress is associated with its suppressing effect on HCC malignant phenotypes. Similar to the in vitro results, HCC growth was significantly reduced by administration of U50488h and oxycodone, but not by morphine, in the HCC xenograft mouse model. PERK and caspase-3 in the HCC tissues were up-regulated by U50488h treatment as detected by immunohistochemistry and western blotting. Taken together, our results revealed that activation of KOR by U50488h inhibited malignant phenotypes of HCC both in vitro and in vivo, while activation of MOR by morphine did not have such effect. Because of their dual roles in the relief of pain and in the suppression of malignant phenotypes, opioids such as U50488h that act on KOR should be considered as the first choice for HCC management.

Down-regulation of kappa opioid receptor promotes ESCC proliferation, invasion and metastasis via the PDK1-AKT signaling pathway

BACKGROUND

As a class of the opioid receptors, the kappa opioid receptor (KOR) has been verified to be a potential biomarker and therapeutic target for human malignant tumors. However, a thorough understanding of whether KOR affects progression of esophageal squamous cell carcinoma (ESCC) is still lacking. This study focused on exploring the effect of knocking down KOR in ESCC and its underlying mechanism.

METHODS

Bioinformatics analysis was used to compare the different expression level of OPRK1 (KOR gene) in tumor and adjacent normal tissues, and predict the relationship between KOR expression and overall survival. RNA-sequence analysis was performed to detect the altered functions and mechanisms after down regulating KOR. The in vitro and in vivo assays were used to detect the effects of down-regulated KOR on cell proliferation, migration and invasion. Substrate gel zymography and 3D cell culture assays were used to find the effect of KOR knockdown on the degradation of extracellular matrix (ECM), and immunefluorescence was performed to detect the altered cytoskeleton. Western blotting and immunohistochemistry were used to explore the underlying mechanism pathway.

RESULTS

Bioinformatics analysis revealed that the expression of OPRK1 was lower in tumor tissue than that in adjacent normal tissues, and lowered expression of KOR was associated with poorer overall survival. The in vitro assays demonstrated that down-regulation of KOR enhanced ESCC proliferation, metastasis and invasion. Western blotting revealed that down-regulation of KOR could activate PDK1-AKT signaling pathway, which actively regulated the cancer progression. Down-regulation of KOR enhanced the formation of invadopodia, secretion of matrix metalloproteinase-2 (MMP2) and rearrangement of cytoskeleton, which were positively related with the invasion of ESCC. KOR knockdown enhanced the tumor invasion and elevated the AKT phosphorylation in nude mice. The AKT kinase inhibition could reverse the effect of down-regulation of KOR.

CONCLUSION

KOR might act as a tumor suppressor in ESCC and down-regulation of KOR could enhance the ESCC tumor phenotype. Video Abstract.

Opioids Regulate the Immune System: Focusing on Macrophages and Their Organelles

Opioids are the most widely used analgesics and therefore have often been the focus of pharmacological research. Macrophages are the most plastic cells in the hematopoietic system. They show great functional diversity in various organism tissues and are an important consideration for the study of phagocytosis, cellular immunity, and molecular immunology. The expression of opioid receptors in macrophages indicates that opioid drugs act on macrophages and regulate their functions. This article reviewed the collection of research on effects of opioids on macrophage function. Studies show that opioids, both endogenous and exogenous, can affect the function of macrophages, effecting their proliferation, chemotaxis, transport, phagocytosis, expression of cytokines and chemokine receptors, synthesis and secretion of cytokines, polarization, and apoptosis. Many of these effects are closely associated with mitochondrial function and functions of other organelles in macrophages. Therefore, in depth research into effects of opioids on macrophage organelles may lead to some interesting new discoveries. In view of the important role of macrophages in HIV infection and tumor progression, this review also discusses effects of opioids on macrophages in these two pathological conditions.

Opioids in cancer: The κ‑opioid receptor (Review)

The κ‑opioid receptor (KOR) is one of the primary receptors of opioids and serves a vital role in the regulation of pain, anesthesia, addiction and other pathological and physiological processes. KOR is associated with several types of cancer and may influence cancer progression. It has been proposed that KOR may represent a new tumor molecular marker and provide a novel basis for molecular targeted therapies for cancer. However, the association between KOR and cancer remains to be explored comprehensively. The present review introduces KOR and its association with different types of cancer. Improved understanding of KOR may facilitate development of novel antitumor therapies.

Low doses of methylnaltrexone inhibits head and neck squamous cell carcinoma growth in vitro and in vivo by acting on the mu-opioid receptor

The Mu-opioid receptor (MOR) has been implicated in tumorigenesis and metastasis. Methylnaltrexone (MNTX), an antagonist of MOR, has shown to inhibit tumor growth and metastasis in lung cancer cell lines. The effect of MNTX on other cell lines such as head and neck squamous cell carcinoma (HNSCC) has not been investigated. We measured the expression and activity of the receptor in different HNSCC cell lines. Then, we evaluated the impact of modulating the expression MOR and the effect of MNTX on the proliferation, clonogenic activity, invasion, and migration of two HNSCC (FaDu and MDA686Tu) cell lines expressing MOR and one cell line (UMSCC47) not expressing the receptor. We also evaluated the impact of MNTX on tumor growth and metastasis formation in vivo. Activation of the receptor with [d-Ala2,N-Me-Phe4, Gly5-ol] (DAMGO) caused a significant reduction in cyclic adenosine monophosphate levels in FaDu cells. Knockdown of MOR inhibited in vitro aggressive cell behaviors on FaDu and MDA686Tu cells and correlated with a reduction in markers of epithelial-mesenchymal transition. In vitro studies showed that MNTX strongly inhibited the proliferation, clonogenic activity, invasion, and migration of FaDu and MDA686Tu cells but has no effect on UMSCC47 cells. In vivo experiments demonstrated that MNTX suppresses tumor growth in HNSCC cell tumor-bearing mice. Our studies indicate that MOR could be considered as a therapeutic target to treat HNSCC.

The kappa opioid receptor may be a potential tumor suppressor by regulating angiogenesis in breast cancer

Our hypothesis proposes that activating κ-opioid receptors (KORs) may inhibit the progression of breast cancer and improve patient prognosis. Consequently, KORs may become a promising therapeutic target for breast cancer. Activating KORs induces not only analgesic efficacy comparable to μ-opioid receptors but also shows a promising antitumor effect and with fewer opioid-induced adverse effects. Based on present studies and our bioinformatics analysis of KORs, we propose that KORs can function as a tumor suppressor by inhibiting angiogenesis in human breast cancer; therefore, analgesics that mainly activate KORs would be more suitable for breast cancer patients.

Butorphanol protects PC12 cells against OGD/R-induced inflammation and apoptosis

The aim of the present study was to examine the effects of butorphanol on neural injury in an oxygen glucose deprivation/reoxygenation (OGD/R) model using PC12 cells, and to investigate whether mitochondrial apoptosis was involved in these effects. To establish the OGD/R model, PC12 cells were cultured under hypoxia and low glucose conditions. Expression levels of inflammatory cytokines were evaluated by detecting the levels of tumor necrosis factor-α, interleukin (IL)-1β, IL-6 and monocyte chemoattractant protein-1. Oxidative stress was evaluated by measuring the levels of reactive oxygen species, lactate dehydrogenase activity and myeloperoxidase concentration. Apoptosis, protein expression and cell viability were determined by flow cytometry, western blotting and by using a Cell Counting Kit-8, respectively. Compared with the control group, cell viability, expression of inflammatory factors and oxidative stress were all decreased in the OGD/R group. All the above changes could be mitigated by treatment with butorphanol. In addition, butorphanol treatment resulted in a significant upregulation of Bax, and downregulation of Bcl-2, activated caspase-3, caspase-9 and poly ADP-ribose polymerase, increased the expression of X-linked inhibitor of apoptosis protein and enhanced ATP activity. To conclude, these results suggested that the protective effects of butorphanol are associated with the inhibition of OGD/R-induced inflammation and apoptosis injury, and may be partially associated with the inhibition of mitochondrial apoptosis.

Inhibitory role of Gi-coupled receptors on cAMP-driven cancers with focus on opioid receptors in lung adenocarcinoma and its stem cells

The development, progression, metastasis and drug resistance of the most common human cancers are driven by cyclic adenosine monophosphate (cAMP)-signaling downstream of beta-adrenergic receptors (β-Ars) coupled to the stimulatory G-protein G_s. Receptors coupled to the inhibitory G-protein G_i inhibit this signaling cascade by blocking the activation of the enzyme adenylyl cyclase that catalyzes the formation of cAMP and function as the physiological inhibitors of this signaling cascade. Members of the G_i-coupled receptor family widely expressed in the mammalian organism are GABA B receptors (GABA_B-Rs) for the inhibitory neurotransmitter γ-aminobutyric acid (GABA), opioid receptors for endogenous opioid peptides and cannabinoid receptors for endogenous cannabinoids. This review summarizes current evidence for the concept that the activation of G_i-receptor signaling by pharmacological and psychological means is a promising tool for the long-term management of cAMP-driven cancers with special emphasis on the inhibitory effects of opioids on lung adenocarcinoma and its stem cells.

Nociceptin Receptor Is Overexpressed in Non-small Cell Lung Cancer and Predicts Poor Prognosis

Classic opioid receptors, mu (μ), delta (δ), and kappa (κ), have been reported to be expressed in non-small cell lung cancer (NSCLC) cell lines and tumor tissues and to play a role in tumor prognosis. However, the expression and role of the non-classic opioid receptor, nociceptin receptor (NOP) in cancer are unclear. Our hypothesis was that NOP was also highly expressed in NSCLC tumor tissues and this could be correlated with patients' prognostic characters. Expression of NOP was examined in archived cancer tissues from 129 enrolled NSCLC patients by immunohistochemistry and was further analyzed with the patients' outcomes. NOP expression in NSCLC cell lines was also detected. The dataset from Kaplan-Meier Plotter was used to explore the correlation between the levels of NOP mRNA in cancerous tissue and the prognosis of NSCLC patients. Cell functional assays were performed to detect the effect of NOP activation on tumor aggressive furthers. Results showed NOP expression was highly expressed in cancer tissues and human cancer cell lines. NOP expression was not associated with patients' opioid requirement but closely with some clinicopathological indicators which reflected the malignancy. Moreover, NOP staining level was the independent poor prognostic factor for NSCLC patients receiving lobectomy, which was further verified by determining the mRNA expression levels through the online dataset. In vitro experiments revealed that NOP activation promotes the proliferation and invasion of A549 cells via PI3K/Akt signaling pathway. We conclude that NOP is overexpressed in NSCLC and is inversely correlated with patient's postoperative survival.

Repurposing of a Nucleoside Scaffold from Adenosine Receptor Agonists to Opioid Receptor Antagonists

While screening off-target effects of rigid (N)-methanocarba-adenosine 5'-methylamides as A₃ adenosine receptor (AR) agonists, we discovered μM binding hits at the δ-opioid receptor (DOR) and translocator protein (TSPO). In an effort to increase OR and decrease AR affinity by structure activity analysis of this series, antagonist activity at κ-(K)OR appeared in 5'-esters (ethyl 24 and propyl 30), which retained TSPO interaction (μM). 7-Deaza modification of C2-(arylethynyl)-5'-esters but not 4'-truncation enhanced KOR affinity (MRS7299 28 and 29, K _i ≈ 40 nM), revealed μ-OR and DOR binding, and reduced AR affinity. Molecular docking and dynamics simulations located a putative KOR binding mode consistent with the observed affinities, placing C7 in a hydrophobic region. 3-Deaza modification permitted TSPO but not OR binding, and 1-deaza was permissive to both; ribose-restored analogues were inactive at both. Thus, we have repurposed a known AR nucleoside scaffold for OR antagonism, with a detailed hypothesis for KOR recognition.

A Kappa Opioid Receptor Agonist Blocks Bone Cancer Pain Without Altering Bone Loss, Tumor Size, or Cancer Cell Proliferation in a Mouse Model of Cancer-Induced Bone Pain

Breast cancer metastasizes to bone, diminishing quality of life of patients because of pain, fracture, and limited mobility. Cancer-induced bone pain (CIBP) is characterized as moderate to severe ongoing pain, primarily managed by mu opioid agonists such as fentanyl. However, opioids are limited by escalating doses and serious side effects. One alternative may be kappa opioid receptor (KOR) agonists. There are few studies examining KOR efficacy on CIBP, whereas KOR agonists are efficacious in peripheral and inflammatory pain. We thus examined the effects of the KOR agonist U50,488 given twice daily across 7 days to block CIBP, tumor-induced bone loss, and tumor burden. U50,488 dose-dependently blocked tumor-induced spontaneous flinching and impaired limb use, without changing tactile hypersensitivity, and was fully reversed by the KOR antagonist nor-binaltorphimine. U50,488 treatment was higher in efficacy and duration of action at later time points. U50,488 blocked this pain without altering tumor-induced bone loss or tumor growth. Follow-up studies in human cancer cell lines confirmed that KOR agonists do not affect cancer cell proliferation. These studies suggest that KOR agonists could be a new target for cancer pain management that does not induce cancer cell proliferation or alter bone loss.

PERSPECTIVE

This study demonstrates the efficacy of KOR agonists in the treatment of bone cancer-induced pain in mice, without changing tumor size or proliferation in cancer cell lines. This suggests that KOR agonists could be used to manage cancer pain without the drawbacks of mu opioid agonists and without worsening disease progression.

Down-regulation of the tumour suppressor κ-opioid receptor predicts poor prognosis in hepatocellular carcinoma patients

BACKGROUND

Opioid receptors have become increasingly implicated in cancer progression and long-term patient outcomes. However, the expression and significance of the κ-opioid receptor (KOR) in hepatocellular carcinoma (HCC) remain unclear.

METHODS

In this study, KOR mRNA expression was analysed by real-time quantitative PCR in 64 pairs of HCC tumour tissues and adjacent non-tumour tissues, and KOR protein expression was analysed by immunohistochemistry in 174 HCC patients. We investigated the correlation between KOR expression and clinicopathological parameters to illustrate the potential prognostic significance of KOR expression in HCC.

RESULTS

KOR mRNA expression was significantly down-regulated in 79.69% (51 of 64) of the HCC tumour samples, and KOR expression in tumour tissue was significantly lower than that in adjacent non-tumour tissues (P < 0.001). ROC curve analysis showed that KOR mRNA expression yielded AUC of 0.745, for the detection of HCC patients. Low KOR mRNA expression in HCC was correlated with aggressive clinicopathological parameters, such as tumour size (P = 0.015), differentiation grade (P = 0.011), and TNM stage (P = 0.021). Moreover, down-regulation of KOR protein expression in HCC tissues was detected in 174 HCC patients. Similarly, negative KOR protein expression was significantly correlated with aggressive clinicopathological features, such as tumour size (P = 0.002), vascular invasion (P = 0.003), differentiation grade (P = 0.026), and TNM stage (P = 0.030). Furthermore, Kaplan-Meier survival analysis demonstrated that down-regulation of KOR in HCC indicated poor prognosis. KOR deficiency (KOR^T < N) was correlated to a shorter survival rate and an increased recurrence (both P < 0.001). In univariate and multivariate survival analyses, KOR was identified as a promising independent risk factor for both overall survival (OS, both P < 0.001) and recurrence-free survival (RFS, both P < 0.001).

CONCLUSIONS

Down-regulation of KOR in HCC tumour tissues has a strong association with poor prognosis and KOR might be a potential tumour suppressor.

Macrocyclic peptides decrease c-Myc protein levels and reduce prostate cancer cell growth

The oncoprotein c-Myc is often overexpressed in cancer cells, and the stability of this protein has major significance in deciding the fate of a cell. Thus, targeting c-Myc levels is an attractive approach for developing therapeutic agents for cancer treatment. In this study, we report the anti-cancer activity of the macrocyclic peptides [D-Trp]CJ-15,208 (cyclo[Phe-D-Pro-Phe-D-Trp]) and the natural product CJ-15,208 (cyclo[Phe-D-Pro-Phe-Trp]). [D-Trp]CJ-15,208 reduced c-Myc protein levels in prostate cancer cells and decreased cell proliferation with IC50 values ranging from 2.0 to 16 µM in multiple PC cell lines. [D-Trp]CJ-15,208 induced early and late apoptosis in PC-3 cells following 48 hours treatment, and growth arrest in the G2 cell cycle phase following both 24 and 48 hours treatment. Down regulation of c-Myc in PC-3 cells resulted in loss of sensitivity to [D-Trp]CJ-15,208 treatment, while overexpression of c-Myc in HEK-293 cells imparted sensitivity of these cells to [D-Trp]CJ-15,208 treatment. This macrocyclic tetrapeptide also regulated PP2A by reducing the levels of its phosphorylated form which regulates the stability of cellular c-Myc protein. Thus [D-Trp]CJ-15,208 represents a new lead compound for the potential development of an effective treatment of prostate cancer.

Novel 18F-Labeled κ-Opioid Receptor Antagonist as PET Radiotracer: Synthesis and In Vivo Evaluation of 18F-LY2459989 in Nonhuman Primates

The κ-opioid receptor (KOR) has been implicated in depression, addictions, and other central nervous system disorders and, thus, is an important target for drug development. We previously developed several ¹¹C-labeled PET radiotracers for KOR imaging in humans. Here we report the synthesis and evaluation of ¹⁸F-LY2459989 as the first ¹⁸F-labeled KOR antagonist radiotracer in nonhuman primates and its comparison with ¹¹C-LY2459989. Methods: The novel radioligand ¹⁸F-LY2459989 was synthesized by ¹⁸F displacement of a nitro group or an iodonium ylide. PET scans in rhesus monkeys were obtained on a small-animal scanner to assess the pharmacokinetic and in vivo binding properties of the ligand. Metabolite-corrected arterial activity curves were measured and used as input functions in the analysis of brain time-activity curves and the calculation of binding parameters. Results: With the iodonium ylide precursor, ¹⁸F-LY2459989 was prepared at high radiochemical yield (36% ± 7% [mean ± SD]), radiochemical purity (>99%), and mean molar activity (1,175 GBq/μmol; n = 6). In monkeys, ¹⁸F-LY2459989 was metabolized at a moderate rate, with a parent fraction of approximately 35% at 30 min after injection. Fast and reversible kinetics were observed, with a regional peak uptake time of less than 20 min. Pretreatment with the selective KOR antagonist LY2456302 (0.1 mg/kg) decreased the activity level in regions with high levels of binding to that in the cerebellum, thus demonstrating the binding specificity and selectivity of ¹⁸F-LY2459989 in vivo. Regional time-activity curves were well fitted by the multilinear analysis 1 kinetic model to derive reliable estimates of regional distribution volumes. With the cerebellum as the reference region, regional binding potentials were calculated and ranked as follows: cingulate cortex > insula > caudate/putamen > frontal cortex > temporal cortex > thalamus, consistent with the reported KOR distribution in the monkey brain. Conclusion: The evaluation of ¹⁸F-LY2459989 in nonhuman primates demonstrated many attractive imaging properties: fast tissue kinetics, specific and selective binding to the KOR, and high specific binding signals. A side-by-side comparison of ¹⁸F-LY2459989 and ¹¹C-LY2459989 indicated similar kinetic and binding profiles for the 2 radiotracers. Taken together, the results indicated that ¹⁸F-LY2459989 appears to be an excellent PET radiotracer for the imaging and quantification of the KOR in vivo.

Molecular Understanding of the Acquisition of Resistance to Anti-cancer Drugs Associated with the Exacerbation of Cancer

Gefitinib and erlotinib target the ATP cleft in the tyrosine kinase EGFR, which is overexpressed in 40-80 percent of non-small-cell lung cancer (NSCLC) and many other epithelial cancers. However, the application of gefitinib is ultimately limited by the emergence of mutations and other molecular mechanisms conferring drug resistance. Furthermore, it has been considered that acquired resistance to gefitinib is associated with a clinically significant risk of accelerated disease progression. We previously established a new gefitinib-resistant NSCLC cell line, HCC827GR, which harbors the T790M mutation. Using HCC827GR, we found that the inhibition of adenosine A2a receptors of NSCLC regulated cancer proliferation and exacerbation, indicating that adenosine A2a receptors may be new targets for a novel strategy in NSCLC therapy. These findings suggest that multilayered crosstalk between G-protein coupled receptors (GPCRs) and EGFR may play an important role in regulating downstream signaling molecules that are implicated in the development of gefitinib-resistant NSCLC.

Fluorine-18-Labeled Antagonist for PET Imaging of Kappa Opioid Receptors

Kappa opioid receptor (KOR) antagonists are potential drug candidates for diseases such as treatment-refractory depression, anxiety, and addictive disorders. PET imaging radiotracers for KOR can be used in occupancy study to facilitate drug development, and to investigate the roles of KOR in health and diseases. We have previously developed two ¹¹C-labeled antagonist radiotracers with high affinity and selectivity toward KOR. What is limiting their wide applications is the short half-life of ¹¹C. Herein, we report the synthesis of a first ¹⁸F-labeled KOR antagonist radiotracer and the initial PET imaging study in a nonhuman primate.

N-[18F]-FluoropropylJDTic for κ-opioid receptor PET imaging: Radiosynthesis, pre-clinical evaluation, and metabolic investigation in comparison with parent JDTic

INTRODUCTION

To image kappa opioid receptor (KOR) for preclinical studies, N-fluoropropylJDTic 9 derived from the best-established KOR antagonist JDTic, was labeled with fluorine-18.

METHODS

Radiosynthesis of [¹⁸F]9 was achieved according to an automated two-step procedure from [¹⁸F]-fluoride. Peripheral and cerebral distributions were determined by ex vivo experiments and by PET imaging in mouse. Radiometabolism studies were performed both in vivo in mice and in vitro in mouse and human liver microsomes. Identification of the major metabolic fragmentations was carried out by UPLC-MS analysis of enzymatic cleavage of non-radioactive ligand 9. Microsomal metabolic degradation of parent JDTic was also achieved for comparison.

RESULTS

The radiotracer [¹⁸F]9 was produced after 140±5min total synthesis time (2.2±0.4% not decay corrected radiochemical yield) with a specific activity of 41-89GBq/μmol (1.1-2.4Ci/μmol). Peripheral and regional brain distributions of [¹⁸F]9 were consistent with known KOR locations but no significant specific binding in brain was shown. [¹⁸F]9 presented a typical hepatobiliary and renal elimination, and was rapidly metabolized. The in vivo and in vitro radiometabolic profiles of [¹⁸F]9 were similar. Piperidine 12 was identified as the major metabolic fragment of the non-radioactive ligand 9. JDTic 7 was found to be much more stable than 9.

CONCLUSION

Although the newly proposed radioligand [¹⁸F]9 was concluded to be not suitable for KOR PET imaging due to the formation of brain penetrating radiometabolites, our findings highlight the metabolic stability of JDTic and may help in the design of novel JDTic derivatives for in vivo applications.

Chronic opioid therapy in long-term cancer survivors

PURPOSE

Long-term cancer survivors develop special health issues and specific needs. Chronic pain, whether the consequence of their cancer or as a side effect of treatment, is one of their most prevalent concerns.

METHODS

We conducted a review of the English-language literature on long-term cancer survivorship and chronic opioid therapy, with the objective of determining the efficacy, safety and tolerability in this group of patients. Practical management recommendations are made on the basis of this review.

RESULTS

Pain syndromes encountered in the long-term cancer survivors are diverse. Opioid receptor pathways possess complex and pleiotropic functions and continuous over-activation may lead to de novo endocrinopathies, immunosuppression, neurocognitive impairment, or cell cycle disturbances with potential clinical connotations. However, there are insufficient data to support evidence-based decision making with respect to patient selection, doses, administration, monitoring and follow-up. Data about long-term treatment effectiveness and safety are limited and often aggravated by the overlapping of several diseases prevalent among long-term cancer survivors, as well as chronic opiate-induced toxicity.

CONCLUSIONS

Chronic opioid therapy is frequent in long-term cancer survivors, and may negatively affect the immune system, and produce health problems such as endocrinopathies, osteoporosis, neurological or cardiopulmonary effects, alterations of cell cycle kinetics, abuse and addiction. This review highlights the need for specialized teams to treat chronic pain in long-term cancer survivors from an integrative perspective.

Regulation of nonsmall-cell lung cancer stem cell like cells by neurotransmitters and opioid peptides

Nonsmall-cell lung cancer (NSCLC) is the leading type of lung cancer and has a poor prognosis. We have shown that chronic stress promoted NSCLC xenografts in mice via stress neurotransmitter-activated cAMP signaling downstream of beta-adrenergic receptors and incidental beta-blocker therapy was reported to improve clinical outcomes in NSCLC patients. These findings suggest that psychological stress promotes NSCLC whereas pharmacologically or psychologically induced decreases in cAMP may inhibit NSCLC. Cancer stem cells are thought to drive the development, progression and resistance to therapy of NSCLC. However, their potential regulation by stress neurotransmitters has not been investigated. In the current study, epinephrine increased the number of cancer stem cell like cells (CSCs) from three NSCLC cell lines in spheroid formation assays while enhancing intracellular cAMP and the stem cell markers sonic hedgehog (SHH), aldehyde dehydrogenase-1 (ALDH-1) and Gli1, effects reversed by GABA or dynorphin B via Gαi -mediated inhibition of cAMP formation. The growth of NSCLC xenografts in a mouse model of stress reduction was significantly reduced as compared with mice maintained under standard conditions. Stress reduction reduced serum levels of corticosterone, norepinephrine and epinephrine while the inhibitory neurotransmitter γ-aminobutyric acid (GABA) and opioid peptides increased. Stress reduction significantly reduced cAMP, VEGF, p-ERK, p-AKT, p-CREB, p-SRc, SHH, ALDH-1 and Gli1 in xenograft tissues whereas cleaved caspase-3 and p53 were induced. We conclude that stress neurotransmitters activate CSCs in NSCLC via multiple cAMP-mediated pathways and that pharmacologically or psychologically induced decreases in cAMP signaling may improve clinical outcomes in NSCLC patients.

Gastric inhibitory polypeptide receptor (GIPR) is a promising target for imaging and therapy in neuroendocrine tumors

BACKGROUND

Ligands binding the somatostatin receptor type 2 (SSTR2) are useful for imaging and treatment of neuroendocrine tumors (NETs), but not all tumors express high levels of these receptors. The aim of this study was to evaluate gene expression of new therapeutic targets in NETs relative to SSTR2.

METHODS

RNA was extracted from 103 primary small bowel and pancreatic NETs, matched normal tissue, and 123 metastases. Expression of 12 candidate genes was measured by quantitative polymerase chain reaction normalized to internal controls; candidate gene expression was compared with SSTR2.

RESULTS

Relative to normal tissue, primary NET expression of SSTR2, GPR98, BRS3, GIPR, GRM1, and OPRK1 were increased by 3, 8, 13, 13, 17, and 20-fold, respectively. Similar changes were found in metastases. Although most candidate genes showed lesser absolute expressions than SSTR2, absolute GIPR expression was closest to SSTR2 (mean dCT 3.6 vs. 2.7, P = .01). Absolute OPRK1 and OXTR expression varied greatly by primary tumor type and was close to SSTR2 in small bowel NETs but not pancreatic NETs.

CONCLUSION

Compared with the current treatment standard SSTR2, GIPR has only somewhat lesser absolute gene expression in tumor tissue but much lesser expression in normal tissue, making it a promising new target for NET imaging and therapy.

Endogenous opiates and behavior: 2012

This paper is the thirty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2012 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).