Opioid receptors beyond pain control: The role in cancer pathology and the debated importance of their pharmacological modulation

Kappa opioid receptor internalisation-induced p38 nuclear translocation suppresses glioma progression

BACKGROUND

Recent studies have implicated a role for perioperative medications in determining patient outcomes after surgery for malignant tumours, including relapse and metastasis.

METHODS

A combined approach spanned molecular, cellular, and organismal levels, including bioinformatics, immunohistochemical staining of clinical and animal samples, RNA sequencing of glioblastoma multiforme (GBM) cells with Ingenuity Pathway Analysis, lentiviral-mediated gene expression modulation, in vitro cell experiments, and in vivo orthotopic tumour transplantation.

RESULTS

We observed a significant correlation between increased kappa opioid receptor (KOP receptor) expression and better prognosis in patients with glioma. Exogenous KOP receptor overexpression in GBM cells in vitro induced cell cycle arrest, suppressed cell growth, and promoted apoptosis. Conversely, reducing KOP receptor expression in GBM cells reduced the proportion of cells in S and G2/M phases, accelerating cell growth. KOP receptor overexpression inhibited glioma cell growth and prolonged survival in mice in vivo, while KOP receptor knockdown had the opposite effect. Mechanistically, internalised KOP receptors were found to bind cytoplasmic p38, facilitating its nuclear translocation and phosphorylation, which influences downstream gene expression. The selective KOP receptor agonist TRK-820 triggered KOP receptor internalisation, activated the p38 pathway, and diminished glioma cell viability in vitro.

CONCLUSIONS

This combined molecular, cellular, and in vivo approach supports use of KOP receptor agonists as potential adjuvant therapeutics for glioma.

Impact of opioids and mu-opioid receptors on oncologic metastasis

Opioids are the most effective and widely used treatments for acute and chronic pain in patients with cancer. This review focuses on the impact of opioids and mu-opioid receptors (MORs) on the stages of oncologic metastasis. Studies have shown that opioids can facilitate tumor progression and are related to a poor prognosis in patients with cancer. As the primary receptor for opioids, MORs play a significant role in regulating malignant tumor transformation and are involved in processes, such as proliferation, angiogenesis, epithelial-mesenchymal transition (EMT), circulating tumor cells (CTCs) and the tumor microenvironment (TME). While clinical trials have investigated the relationship between opioids and patient prognosis, further research is needed to clarify the relationship between opioids, MORs and metastasis.

Opioids and Cancer: Current Understanding and Clinical Considerations

Pain is one of the most common symptoms in patients with cancer. Pain not only negatively affects the quality of life of patients with cancer, but it has also been associated with reduced survival. Pain management is therefore a critical component of cancer care. Prescription opioids remain the first-line approach for the management of moderate-to-severe pain associated with cancer. However, there has been increasing interest in understanding whether these analgesics could impact cancer progression. Furthermore, epidemiological data link a possible association between prescription opioid usage and cancer development. Until more robust evidence is available, patients with cancer with moderate-to-severe pain may receive opioids to decrease suffering. However, future studies should be conducted to evaluate the role of opioids and opioid receptors in specific cancers.

Problems with opioids - beyond misuse

The U.S. is grappling with an opioid epidemic, with millions of adults on long-term opioid therapy (LTOT). Although patients often report pain relief and improved daily function with opioids, research shows no significant differences in short-term outcomes between opioid and non-opioid users, as well as no long-term opioid benefits. This scoping review aims to identify lesser-known side effects of long-term opioid use and increase awareness of them, allowing healthcare providers and patients to better assess the risks and benefits of opioid use. Our data search from PubMed and Google Scholar used keywords related to opioids, chronic pain, hypogonadism, endocrinopathies, cancer progression, cardiovascular events, renovascular events, sleep disturbances, mood disorders and others, narrowing down to English-language full articles published from January 2018 to April 2023. This review emphasizes the probable serious adverse consequences of long-term opioid use on various body systems in patients with chronic pain. Given the lack of long-term benefits and significant adverse effects, our review underscores the critical need for healthcare providers to include these risks in discussions with patients when considering the long-term use of opioid therapy.

Immunomodulatory properties of morphine and the hypothesised role of long-term opioid use in the immunopathogenesis of tuberculosis

Epidemiological studies have shown high tuberculosis (TB) prevalence among chronic opioid users. Opioid receptors are found on multiple immune cells and immunomodulatory properties of opioids could be a contributory factor for ensuing immunosuppression and development or reactivation of TB. Toll-like receptors (TLR) mediate an immune response against microbial pathogens, including Mycobacterium tuberculosis. Mycobacterial antigens and opioids co-stimulate TLRs 2/4/9 in immune cells, with resulting receptor cross-talk via multiple cytosolic secondary messengers, leading to significant immunomodulatory downstream effects. Blockade of specific immune pathways involved in the host defence against TB by morphine may play a critical role in causing tuberculosis among chronic morphine users despite multiple confounding factors such as socioeconomic deprivation, Human immunodeficiency virus co-infection and malnutrition. In this review, we map out immune pathways involved when immune cells are co-stimulated with mycobacterial antigens and morphine to explore a potential immunopathological basis for TB amongst long-term opioid users.

Methadone dose escalation in patients with opioid use disorder and cancer as a strategy for controlling cancer-related pain: A case series

OBJECTIVES

Opioid use disorder (OUD) and cancer gained attention as co-occurring diseases in the last 2 decades due to the possible relationship between opioid prescriptions for cancer pain and the risk of developing substance use disorder in cancer patients. However, little is known about patients previously diagnosed with OUD who develop cancer and how to manage both OUD symptoms and control pain.

METHODS

The present case series deals with this subpopulation and proposes a dose escalation of methadone to control both the cancer-related pain and drug addiction symptoms.

RESULTS

This approach is peculiar because methadone is not used as a first-line treatment in cancer pain management and is not often used as a second-line treatment as well. Our 4 patients experienced good clinical control of symptoms and no major adverse reactions.

SIGNIFICANCE OF RESULTS

The subgroup of patients with OUD who develop cancer could be the perfect population to reconsider the use of methadone as a first-line treatment for cancer pain. Prospective studies are needed to evaluate the efficacy and safety of increasing doses of methadone in these patients to validate our clinical approach.

Involvement of the Opioid Peptide Family in Cancer Progression

Peptides mediate cancer progression favoring the mitogenesis, migration, and invasion of tumor cells, promoting metastasis and anti-apoptotic mechanisms, and facilitating angiogenesis/lymphangiogenesis. Tumor cells overexpress peptide receptors, crucial targets for developing specific treatments against cancer cells using peptide receptor antagonists and promoting apoptosis in tumor cells. Opioids exert an antitumoral effect, whereas others promote tumor growth and metastasis. This review updates the findings regarding the involvement of opioid peptides (enkephalins, endorphins, and dynorphins) in cancer development. Anticancer therapeutic strategies targeting the opioid peptidergic system and the main research lines to be developed regarding the topic reviewed are suggested. There is much to investigate about opioid peptides and cancer: basic information is scarce, incomplete, or absent in many tumors. This knowledge is crucial since promising anticancer strategies could be developed alone or in combination therapies with chemotherapy/radiotherapy.

Harnessing interventions during the immediate perioperative period to improve the long-term survival of patients following radical gastrectomy

Although the incidence and mortality of gastric cancer (GC) have been decreasing steadily worldwide, especially in East Asia, the disease burden of this malignancy is still very heavy. Except for tremendous progress in the management of GC by multidisciplinary treatment, surgical excision of the primary tumor is still the cornerstone intervention in the curative-intent treatment of GC. During the relatively short perioperative period, patients undergoing radical gastrectomy will suffer from at least part of the following perioperative events: Surgery, anesthesia, pain, intraoperative blood loss, allogeneic blood transfusion, postoperative complications, and their related anxiety, depression and stress response, which have been shown to affect long-term outcomes. Therefore, in recent years, studies have been carried out to find and test interventions during the perioperative period to improve the long-term survival of patients following radical gastrectomy, which will be the aim of this review.

Nociceptin/Orphanin FQ receptor expression in primary human umbilical vein endothelial cells is not regulated by exposure to breast cancer cell media or angiogenic stimuli

Background

Opioid receptors are naloxone-sensitive (MOP [mu: μ], DOP [delta: δ], and KOP [kappa: κ]) and naloxone-insensitive Nociceptin/Orphanin FQ (N/OFQ) peptide receptor (NOP). Clinically, most opioid analgesics target MOP. Angiogenesis is the formation of new blood vessels and involves endothelial cell activation, proliferation, and migration. The effect of opioids on this process is controversial with no data for NOP receptor ligands.

Methods

We used patient-derived human umbilical vein endothelial cells (HUVECs) treated with media from the Michigan Cancer Foundation-7 (MCF-7) breast cancer cells or vascular endothelial growth factor (VEGF; 10 ng ml-1) and fibroblast growth factor (FGF; 10 ng ml-1) as angiogenic stimuli. We have measured (i) NOP/MOP messenger RNA, (ii) receptor protein using N/OFQATTO594 and DermorphinATTO488 as fluorescent probes for NOP and MOP, and (iii) NOP/MOP function in a wound healing assay (crude measure of migration that occurs during angiogenesis).

Results

HUVEC lines from 32 patients were used. Using all 32 lines, mRNA for NOP but not MOP was detected. This was unaffected by media from MCF-7 cells or VEGF/FGF. There was no binding of either N/OFQATTO594(NOP) or DermorphinATTO488(MOP) in the absence or presence of angiogenic stimuli (six lines tested). In the absence of MOP mRNA, this was expected. Whilst MCF-7 conditioned medium (not VEGF/FGF) reduced wound healing per se (14 lines tested), there was no effect of N/OFQ (NOP ligand) or morphine (MOP ligand).

Conclusions

Media from MCF-7 breast cancer cells or VEGF/FGF as angiogenic stimuli did not influence NOP translation into receptor protein. MOP was absent. In the absence of constitutive or inducible MOP/NOP, there was no effect on wound healing as a measure of angiogenesis.

The Impact of Perioperative Events on Cancer Recurrence and Metastasis in Patients after Radical Gastrectomy: A Review

Radical gastrectomy is a mainstay therapy for patients with locally resectable gastric cancer (GC). GC patients who are candidates for radical gastrectomy will experience at least part of the following perioperative events: surgery, anesthesia, pain, intraoperative blood loss, allogeneic blood transfusion, postoperative complications, and their related anxiety, depression and stress response. Considerable clinical studies have shown that these perioperative events can promote recurrence and decrease the long-term survival of GC patients. The mechanisms include activation of neural signaling and the inflammatory response, suppression of antimetastatic immunity, increased release of cancer cells into circulation, and delayed adjuvant therapy, which are involved in every step of the invasion-metastasis cascade. Having appreciated these perioperative events and their influence on the risk of GC recurrence, we can now use this knowledge to find strategies that might substantially prevent the deleterious recurrence-promoting effects of perioperative events, potentially increasing cancer-free survival in GC patients.

The other side of the coin: Positive view on the role of opioids in cancer

Opioids have been used for medicinal purposes as an analgesic and recreational purposes as a euphorigenic throughout human history. Cancer patients are often treated with different doses of opioids concurrently with anti-cancer drugs for pain relief without exhibiting excessive adverse effects. The intersection of the biology of pain, opioid therapy, and disease progression represents the crux of the matters and is of potentially great importance in cancer care. For more than 20 years, multiple investigations have focused on the stimulatory effects of opioids on cancer cell growth, while in-depth studies on the inhibitory effects on cancer cell growth development have usually been neglected. This paper reviews the evidence regarding opioid therapies and their anti-cancer effects on various malignancies. Likewise, we have a glimpse into the molecular mechanisms necessary for pinpointing their positive or negative impacts on malignancies to raise awareness and stimulate more excellent dialogue regarding their carcinogenic/anticarcinogenic roles.

Olanzapine-samidorphan combination tablets for the treatment of schizophrenia and bipolar I disorder - what is it, and will it be used?

INTRODUCTION

: Although olanzapine remains one of the most efficacious antipsychotic medications for the treatment of schizophrenia, there are significant tolerability concerns related to its weight and metabolic profile. Olanzapine-samidorphan combination tablets (OLZ/SAM), branded as Lybalvi, is a newly FDA approved formulation aimed at attenuating antipsychotic induced weight gain via modulation of the endogenous opioid system with samidorphan, while retaining the robust antipsychotic efficacy of olanzapine.

AREAS COVERED

: We reviewed the published literature of OLZ/SAM for the management of schizophrenia using the US National Library of Medicine's PubMed.gov resource. Topics covered in this narrative review include the pharmacokinetics, pharmacodynamics, tolerability, and efficacy of OLZ/SAM.

EXPERT OPINION

: OLZ/SAM is an effective and well tolerated pharmacologic option in mitigating olanzapine induced weight gain while retaining olanzapine's efficacy. It has a limited effect on metabolic laboratory parameters and cumulatively tends to limit weight gain rather than promote weight loss. Additional research will be needed to determine its effectiveness compared to alternative strategies to attenuate antipsychotic induced weight gain.

Opioid Receptor-Mediated and Non-Opioid Receptor-Mediated Roles of Opioids in Tumour Growth and Metastasis

Opioids are administered to cancer patients in the period surrounding tumour excision, and in the management of cancer-associated pain. The effects of opioids on tumour growth and metastasis, and their consequences on disease outcome, continue to be the object of polarised, discrepant literature. It is becoming clear that opioids contribute a range of direct and indirect effects to the biology of solid tumours, to the anticancer immune response, inflammation, angiogenesis and importantly, to the tumour-promoting effects of pain. A common misconception in the literature is that the effect of opioid agonists equates the effect of the mu-opioid receptor, the major target of the analgesic effect of this class of drugs. We review the evidence on opioid receptor expression in cancer, opioid receptor polymorphisms and cancer outcome, the effect of opioid antagonists, especially the peripheral antagonist methylnaltrexone, and lastly, the evidence available of a role for opioids through non-opioid receptor mediated actions.

Electroanalysis of Fentanyl and Its New Analogs: A Review

The review describes fentanyl and its analogs as new synthetic opioids and the possibilities of their identification and determination using electrochemical methods (e.g., voltammetry, potentiometry, electrochemiluminescence) and electrochemical methods combined with various separation methods. The review also covers the analysis of new synthetic opioids, their parent compounds, and corresponding metabolites in body fluids, such as urine, blood, serum, and plasma, necessary for a fast and accurate diagnosis of intoxication. Identifying and quantifying these addictive and illicit substances and their metabolites is necessary for clinical, toxicological, and forensic purposes. As a reaction to the growing number of new synthetic opioid intoxications and increasing fatalities observed over the past ten years, we provide thorough background for developing new biosensors, screen-printed electrodes, or other point-of-care devices.

Perioperative pain, analgesics and cancer-related outcomes: where do we stand?

Cancer-related pain is one of the most common and debilitating symptoms among cancer patients. Undertreated cancer-related pain interferes with daily activities and increases morbidity and mortality. While opioids continue to play an essential role in treating moderate to severe cancer-related pain, they are associated with many adverse effects including misuse. While preclinical and retrospective studies have shown a negative association between opioid use and cancer outcomes, randomized control trials demonstrate that opioid use does not influence cancer recurrence. Additionally, analgesics and adjuvants used for perioperatively or chronic pain control are unlikely to improve oncological outcomes. This article focuses on the pharmacological management of cancer-related pain and offers an overview regarding the use of these medications perioperatively and the cancer outcomes.

Long-term Survival after Combined Epidural-General Anesthesia or General Anesthesia Alone: Follow-up of a Randomized Trial

BACKGROUND

Experimental and observational research suggests that combined epidural-general anesthesia may improve long-term survival after cancer surgery by reducing anesthetic and opioid consumption and by blunting surgery-related inflammation. This study therefore tested the primary hypothesis that combined epidural-general anesthesia improves long-term survival in elderly patients.

METHODS

This article presents a long-term follow-up of patients enrolled in a previous trial conducted at five hospitals. Patients aged 60 to 90 yr and scheduled for major noncardiac thoracic and abdominal surgeries were randomly assigned to either combined epidural-general anesthesia with postoperative epidural analgesia or general anesthesia alone with postoperative intravenous analgesia. The primary outcome was overall postoperative survival. Secondary outcomes included cancer-specific, recurrence-free, and event-free survival.

RESULTS

Among 1,802 patients who were enrolled and randomized in the underlying trial, 1,712 were included in the long-term analysis; 92% had surgery for cancer. The median follow-up duration was 66 months (interquartile range, 61 to 80). Among patients assigned to combined epidural-general anesthesia, 355 of 853 (42%) died compared with 326 of 859 (38%) deaths in patients assigned to general anesthesia alone: adjusted hazard ratio, 1.07; 95% CI, 0.92 to 1.24; P = 0.408. Cancer-specific survival was similar with combined epidural-general anesthesia (327 of 853 [38%]) and general anesthesia alone (292 of 859 [34%]): adjusted hazard ratio, 1.09; 95% CI, 0.93 to 1.28; P = 0.290. Recurrence-free survival was 401 of 853 [47%] for patients who had combined epidural-general anesthesia versus 389 of 859 [45%] with general anesthesia alone: adjusted hazard ratio, 0.97; 95% CI, 0.84 to 1.12; P = 0.692. Event-free survival was 466 of 853 [55%] in patients who had combined epidural-general anesthesia versus 450 of 859 [52%] for general anesthesia alone: adjusted hazard ratio, 0.99; 95% CI, 0.86 to 1.12; P = 0.815.

CONCLUSIONS

In elderly patients having major thoracic and abdominal surgery, combined epidural-general anesthesia with epidural analgesia did not improve overall or cancer-specific long-term mortality. Nor did epidural analgesia improve recurrence-free survival. Either approach can therefore reasonably be selected based on patient and clinician preference.

EDITOR’S PERSPECTIVE

β-endorphin at the intersection of pain and cancer progression: Preclinical evidence

We examined the association between endogenous opioid β-endorphin, cancer progression and pain in a transgenic mouse model of breast cancer, with a rat C3(1) simian virus 40 large tumor antigen fusion gene (C3TAg). C3TAg mice develop ductal epithelial atypia at 8 weeks, progression to intra-epithelial neoplasia at 12 weeks, and invasive carcinoma with palpable tumors at 16 weeks. Consistent with invasive carcinoma at 4 months of age, C3TAg mice demonstrate a significant increase in hyperalgesia compared to younger C3TAg or control FVBN mice without tumors. Our data show that the growing tumor contributes to circulating β-endorphin. As an endogenous ligand of mu opioid receptor, β-endorphin has analgesic activity. Paradoxically, we observed an increase in pain in transgenic breast cancer mice with significantly high circulating and tumor-associated β-endorphin. Increased circulating β-endorphin correlates with increasing tumor burden. β-endorphin induced the activation of mitogenic and survival-promoting signaling pathways, MAPK/ERK 1/2, STAT3 and Akt, observed by us in human MDA-MB-231 cells suggesting a role for β-endorphin in breast cancer progression and associated pain.

Oxycodone stimulates normal and malignant hematopoietic progenitors via opioid-receptor-independent-β-catenin activation

Oxycodone is a common type of opioid used for the treatment of moderate to severe pain. Besides its analgesic effects on neuron cells, the effects of oxycodone on other cell types are yet to be elucidated. We previously demonstrated that oxycodone displayed both pro- and anti-cancer effects on bulk cancer cells. This work further investigated the effects of oxycodone on normal and malignant hematopoietic stem cells. Using hematopoietic CD34⁺ cells isolated from normal bone marrow (NBM) or patients with acute myeloid leukemia (AML), we showed that oxycodone activates hematopoietic cells regardless of cell development stage and malignant status. Oxycodone dose-dependently increases colony formation and self-renewal capacity of NBM and AML stem/progenitor cells, and promotes proliferation of AML bulk cells. NBM stem/progenitor cells are more sensitive to oxycodone than AML counterparts. In addition, oxycodone alleviates chemotherapy drug-induced toxicity in AML stem/progenitor cells. Mechanism studies demonstrate that oxycodone acts on hematopoietic cells in an opioid-receptor-independent manner. Oxycodone did not affect epithelial growth factor receptor (EGFR) signaling neither but stimulated Wnt/β-catenin signaling. Rescue studies via depleting β-catenin using genetic and pharmacological approaches confirmed that β-catenin was required for the activation of hematopoietic cells induced by oxycodone. Our work demonstrates 1) the protective role of oxycodone in malignant hematopoietic cells from chemotherapy; 2) stimulatory effects of oxycodone in normal hematopoietic stem cells; and 3) ability of oxycodone in Wnt signaling activation.

Fentanyl stimulates tumor angiogenesis via activating multiple pro-angiogenic signaling pathways

Angiogenesis plays a vital role in tumor progression and metastasis. To better understand the role of anesthesia in tumor biology, we previously reported that bupivacaine displayed the inhibitory effects in endothelial cells. In this work, we demonstrated that fentanyl, an opioid medication commonly used in cancer patients, stimulated tumor angiogenesis. We found that fentanyl at nanomolar concentrations significantly stimulated capillary network formation of human lung tumor-associated endothelial cell (HLT-EC) in a similar manner as vascular endothelial growth factor (VEGF), and furthermore that the stimulatory effect of fentanyl was mainly involved in early stage of HLT-EC vascular structure assembly. Particularly, fentanyl significantly increased HLT-EC growth and migration. Fentanyl also protected HLT-EC from apoptosis induced by growth factor withdrawal. In contrast, the same concentrations of fentanyl did not affect human lung cancer cell growth and survival. Fentanyl stimulated migration of some but not all tested human lung cancer cells. Mechanism analysis suggested that fentanyl activates multiple pro-angiogenic signaling pathways, including VEGFR2/FAK/PI3K/Akt and small GTPases. Our work systematically demonstrates that fentanyl stimulates tumor angiogenesis via activating multiple pro-angiogenic signaling pathways. Our findings highlight the potential adverse effect of fentanyl in cancer patients.