The novel role of the mu opioid receptor in lung cancer progression: a laboratory investigation

Are we causing the recurrence-impact of perioperative period on long-term cancer prognosis: Review of current evidence and practice

Newer developments in the field of chemotherapeutic drug regimes, radiotherapy, and surgical techniques have improved the prognosis of cancer patients tremendously. Today increasing numbers of patients with aggressive disease are posted for surgical resection. The advances in reconstructive flap surgery offer the patient a near normal dignified postresection life. Hence, the expectations from the patients are also on the rise. Anesthetic challenges known in oncosurgery are that of difficult airway, maintenance of hemodynamics and temperature during long surgical hours, pain management, and postoperative intensive care management. But, recently acquired data raised the possibility of the anesthetic technique and conduct of perioperative period as a possible contributory factor in the growth and possible recurrence of the primary tumor. The foundation of the concept is somewhat fragile and not supported by conclusive evidence. In fact, like any other controversial topic in medicine, contradictory reports of the favorable effects of anesthetic technique and medications are plenty in the literature. This is the basis of our article where we have analyzed the current evidence available in the literature and how these and the forthcoming large scale studies may revolutionize the practice of oncoanesthesia.

Increased μ-opioid receptor expression in metastatic lung cancer

BACKGROUND

We and others have previously demonstrated that the μ-opioid receptor (MOR) is overexpressed in several human malignancies. There is a seven-fold increase in MOR in cell lines of human lung cancer. In animal models, overexpression of MOR promotes tumour growth and metastasis. We, therefore, examined whether MOR expression is increased in metastatic lung cancer.

METHODS

In this study, we examined the association between MOR expression and metastasis in archived biopsy samples from patients with lung cancer. Paraffin-embedded patient material was stained using MOR antibody and scored qualitatively by two independent pathologists using a four-point scale.

RESULTS

In human lung cancer and normal adjacent lung samples obtained from 34 lung cancer patients, MOR expression was increased significantly in cancer samples from patients with lung cancer compared with adjacent control tissue (P=0.0242). When the samples from patients with metastatic lung cancer were separated from the cohort of the total number of patients with lung cancer, we observed an approximately two-fold increase in MOR expression (P=0.0013).

CONCLUSIONS

The association between the expression of MOR and the progression of the tumour is consistent with the hypothesis of a direct effect of MOR on cancer progression.

Morphine stimulates cancer progression and mast cell activation and impairs survival in transgenic mice with breast cancer

BACKGROUND

Morphine stimulates angiogenesis and cancer progression in mice. We investigated whether morphine influences tumour onset, development, and animal model survival, and whether µ-opioid receptor (MOR), lymphangiogenesis, mast cell activation, and substance P (SP) are associated with the tumour-promoting effects of morphine.

METHODS

Transgenic mice with a rat C3(1) simian virus 40 large tumour antigen fusion gene which demonstrate the developmental spectrum of human infiltrating ductal breast carcinoma were used. Mice were treated at different ages with clinically relevant doses of morphine or phosphate-buffered saline to determine the effect on tumour development and progression, and on mouse survival. Tumours were analysed for MOR, angiogenesis, lymphangiogenesis, SP, and mast cell activation by immunofluorescent- or laser scanning confocal-microscopy. Cytokine and SP levels were determined by enzyme-linked immunosorbent assay.

RESULTS

Morphine did not influence tumour development when given before the onset of tumour appearance, but significantly promoted progression of established tumours, and reduced survival. MOR-immunoreactivity (ir) was observed in larger but not in smaller tumours. Morphine treatment resulted in increased tumour angiogenesis, peri-tumoural lymphangiogenesis, mast cell activation, and higher levels of cytokines and SP in tumours. SP-ir co-localized with mast cells and elsewhere in the tumours.

CONCLUSIONS

Morphine does not affect the onset of tumour development, but it promotes growth of existing tumours, and reduces overall survival in mice. MOR may be associated with morphine-induced cancer progression, resulting in shorter survival. Mast cell activation by morphine may contribute to increased cytokine and SP levels, leading to cancer progression and refractory pain.

The role of analgesics in cancer propagation

The treatment of cancer pain is paramount to both medical practitioner and patient in order to maximize quality of life. Cancer pain results from direct tumor effects as well as from surgical and medical treatments. Despite therapeutic advancements, morbidity and mortality in cancer care remains high, often from local recurrence or metastasis. Increasing evidence suggests analgesics affect the cellular milieu of malignant and nonmalignant cells and may influence cancer outcomes by directly stimulating tumor growth and inhibiting immune surveillance. Opioids have been shown to cause immunosuppression and stimulate malignant cells in vitro, though adjunct analgesics may additionally promote tumor cell growth. These results have led many to hypothesize that regional analgesic techniques may offer survival advantages to systemic analgesics. Thus far, the data do not support specific analgesic recommendations for the cancer patient, though ongoing prospective, randomized clinical trials are under way to better characterize the safest analgesic regimens for cancer patients.

A retrospective analysis of the effect of intraoperative opioid dose on cancer recurrence after non-small cell lung cancer resection

Preclinical studies have demonstrated that opioid receptor agonists increase the rate of non-small cell lung cancer (NSCLC) growth and metastasis. Following institutional review board approval, we retrieved data on 901 patients who underwent surgery for NSCLC at MD Anderson Cancer Center. Comprehensive demographics, intraoperative data, and recurrence-free survival (RFS) and overall survival (OS) at 3 and 5 years were obtained. Cox proportional analyses were conducted to assess the association between intraoperative opioid exposure and RFS and OS. The median intraoperative fentanyl equivalents dosage was 10.15 μg/kg. The multivariate analysis by stage indicated that a trend toward significance for opioid consumption as a risk factor in stage I patients (P = 0.053). No effect was found on RFS for stage II or III patients. Alternatively, opioid consumption was a risk factor for OS for stage I patients (P = 0.036), whereas no effect was noted for stage II or III patients. Intraoperative opioid use is associated with decreased OS in stage I but not stage II–III NSCLC patients. Until randomized controlled studies explore this association further, opioids should continue to be a key component of balanced anesthesia.

Meta-analysis of the effects of beta blocker on survival time in cancer patients

PURPOSE

This study was to elucidate the potential benefit of beta blockers on cancer survival.

METHODS

We comprehensively searched PubMed, Embase, and the Cochrane Library from their inception to April 2013. Two authors independently screened and reviewed the eligibility of each study and coded the participants, treatment, and outcome characteristics. The primary outcomes were overall survival (OS) and disease-free survival (DFS).

RESULTS

Twelve studies published between 1993 and 2013 were included in the final analysis. Four papers reported results from 10 independent groups, resulting in a total of 18 comparisons based on data obtained from 20,898 subjects. Effect sizes (hazard ratios, HR) were heterogeneous, and random-effects models were used in the analyses. The meta-analysis demonstrated that beta blocker use is associated with improved OS (HR 0.79; 95 % CI 0.67-0.93; p = 0.004) and DFS (HR 0.69; 95 % CI 0.53-0.91; p = 0.009). Although statistically not significant, the effect size was greater in patients with low-stage cancer or cancer treated primarily with surgery than in patients with high-stage cancer or cancer treated primarily without surgery (HR 0.60 vs. 0.78, and 0.60 vs. 0.80, respectively). Although only two study codes were analyzed, the studies using nonselective beta blockers showed that there was no overall effect on OS (HR 0.52, 95 % CI 0.09-3.04).

CONCLUSION

This meta-analysis provides evidence that beta blocker use can be associated with the prolonged survival of cancer patients, especially patients with early-stage cancer treated primarily with surgery.

The Mu opioid receptor promotes opioid and growth factor-induced proliferation, migration and Epithelial Mesenchymal Transition (EMT) in human lung cancer

Recent epidemiologic studies implying differences in cancer recurrence based on anesthetic regimens raise the possibility that the mu opioid receptor (MOR) can influence cancer progression. Based on our previous observations that overexpression of MOR in human non-small cell lung cancer (NSCLC) cells increased tumor growth and metastasis, this study examined whether MOR regulates growth factor receptor signaling and epithelial mesenchymal transition (EMT) in human NSCLC cells. We utilized specific siRNA, shRNA, chemical inhibitors and overexpression vectors in human H358 NSCLC cells that were either untreated or treated with various concentrations of DAMGO, morphine, fentanyl, EGF or IGF. Cell function assays, immunoblot and immunoprecipitation assays were then performed. Our results indicate MOR regulates opioid and growth factor-induced EGF receptor signaling (Src, Gab-1, PI3K, Akt and STAT3 activation) which is crucial for consequent human NSCLC cell proliferation and migration. In addition, human NSCLC cells treated with opioids, growth factors or MOR overexpression exhibited an increase in snail, slug and vimentin and decrease ZO-1 and claudin-1 protein levels, results consistent with an EMT phenotype. Further, these effects were reversed with silencing (shRNA) or chemical inhibition of MOR, Src, Gab-1, PI3K, Akt and STAT3 (p<0.05). Our data suggest a possible direct effect of MOR on opioid and growth factor-signaling and consequent proliferation, migration and EMT transition during lung cancer progression. Such an effect provides a plausible explanation for the epidemiologic findings.

Anesthetic techniques and cancer recurrence after surgery

Many of the most common anesthetics are used in surgical oncology, yet effects on cancer cells are still not known. Anesthesia technique could differentially affect cancer recurrence in oncologic patients undergoing surgery, due to immunosuppression, stimulation of angiogenesis, and dissemination of residual cancer cells. Data support the use of intravenous anesthetics, such as propofol anesthesia, thanks to antitumoral protective effects inhibiting cyclooxygenase 2 and prostaglandins E2 in cancer cells, and stimulation of immunity response; a restriction in the use of volatile anesthetics; restriction in the use of opioids as they suppress humoral and cellular immunity, and their chronic use favors angiogenesis and development of metastases; use of locoregional anesthesia compared with general anesthesia, as locoregional appears to reduce cancer recurrence after surgery. However, these findings must be interpreted cautiously as there is no evidence that simple changes in the practice of anesthesia can have a positive impact on postsurgical survival of cancer patients.

Effects of postoperative epidural analgesia on recurrence-free and overall survival in patients with nonsmall cell lung cancer

STUDY OBJECTIVE

To determine whether postoperative epidural analgesia is associated with better recurrence-free survival and overall survival after lung cancer surgery.

DESIGN

Retrospective study.

SETTING

Academic hospital.

MEASUREMENTS

Data of patients with stage 1, stage 2, and stage 3 nonsmall cell lung cancer, who underwent tumor resection surgery, were studied. Patient data were grouped into three different postoperative pain management interventions: intravenous patient-controlled analgesia, patient-controlled epidural analgesia, and their combination. Univariate and multicovariate Cox proportional hazards models were applied to assess the effects of covariates of interest on overall survival and recurrence-free survival.

MAIN RESULTS

The type of postoperative analgesia used for patients who underwent surgery for nonsmall cell lung cancer did not affect recurrence-free survival or overall survival. However, certain variables, including age ≥ 65 years, male gender, body mass index ≥ 25 kg/m(2), ASA physical status 4, and the need for preoperative blood transfusions, pneumonectomy, and postoperative radiation, were associated with decreased recurrence-free survival and overall survival.

CONCLUSIONS

The type of postoperative analgesia used after surgery for nonsmall cell lung cancer is not associated with better 2-year or 5-year recurrence-free survival or overall survival rates.

Morphine modulates cell proliferation through mir133b &mir128 in the neuroblastoma SH-SY5Y cell line

Neuroblastoma is a childhood cancer with high incidence and high mortality rate. Great efforts are made to find new treatments and molecular markers for diagnosis and prognosis. miRNAs stand for novel strategies to modulate tumor growth, as they can act either as tumor suppressors or as oncogenes. Morphine is an opioid agonist widely used to treat severe and chronic pain, as for example cancer pain. Previous studies have revealed that morphine is able to modify cancer progression, by acting on proliferation or on apoptosis; however, up to date, the available results are contradictory, maybe due to the different doses used, routes of administration and model systems. While some studies show that morphine promotes cell proliferation and metastasis, other authors sustain that morphine effect is mainly antiproliferative and pro-apoptotic. In this study we aim to establish the effect of chronic opiate administration on cell proliferation in the neuroblastoma SH-SY5Y cell line. Low doses of morphine (10nM) promoted cell proliferation in undifferentiated cells and reduced the expression levels of miR133b, while higher doses (1μM) inhibited cell proliferation and correlated with decreased levels of miR133b and miR128 without triggering apoptosis. Naloxone, the classical opioid antagonist, could not fully block the effect of morphine on miR128 expression, so that the observed effect may be mediated by non-opioid mechanisms. Our results represent a further contribution to the hypothesis that a joint regulation of miRNA networks and the specific characteristics of the target tissue may determine the effect of morphine on tumor cell growth.

Does regional anaesthesia and analgesia or opioid analgesia influence recurrence after primary cancer surgery? An update of available evidence

Cancer continues to be a key cause of morbidity and mortality worldwide and its overall incidence continues to increase. Anaesthetists are increasingly faced with the challenge of managing cancer patients, for surgical resection to debulk or excise the primary tumour, or for surgical emergencies in patients on chemotherapy or for the analgesic management of disease- or treatment-related chronic pain. Metastatic recurrence is a concern. Surgery and a number of perioperative factors are suspected to accelerate tumour growth and potentially increase the risk of metastatic recurrence. Retrospective analyses have suggested an association between anaesthetic technique and cancer outcomes, and anaesthetists have sought to ameliorate the consequences of surgical trauma and minimise the impact of anaesthetic interventions. Just how anaesthesia and analgesia impact cancer recurrence and consequent survival is very topical, as understanding the potential mechanisms and interactions has an impact on the anaesthetist's ability to contribute to the successful outcome of oncological interventions. The outcome of ongoing, prospective, randomized trials are awaited with interest.

Opioid requirement, opioid receptor expression, and clinical outcomes in patients with advanced prostate cancer

BACKGROUND

Preclinical studies show that opioids stimulate angiogenesis and tumor progression through the mu opioid receptor (MOR). Although MOR is overexpressed in several human malignancies, the effect of chronic opioid requirement on cancer progression or survival has not been examined in humans.

METHODS

We performed a retrospective analysis on 113 patients identified in the Minneapolis VA Tumor Registry (test cohort) and 480 patients from the national VA Central Cancer Registry (validation cohort) who had been diagnosed with stage IV prostate cancer between 1995 and 2010 to examine whether MOR expression or opioid requirement is associated with disease progression and survival. All opioids were converted to oral morphine equivalents for comparison. Laser scanning confocal microscopy was used to analyze MOR immunoreactivity in prostate cancer biopsies. The effects of variables on outcomes were analyzed in univariable and multivariable models.

RESULTS

In patients with metastatic prostate cancer, MOR expression and opioid requirement were independently associated with inferior progression-free survival (hazard ratio [HR] 1.65, 95% confidence interval [CI] 1.33-2.07, P<.001 and HR 1.08, 95% CI 1.03-1.13, P<.001, respectively) and overall survival (HR 1.55, 95% CI 1.20-1.99, P<.001 and HR 1.05, 95% CI 1.00-1.10, P = .031, respectively). The validation cohort confirmed that increasing opioid requirement was associated with worse overall survival (HR 1.005, 95% CI 1.002-1.008, P = .001).

CONCLUSION

Higher MOR expression and greater opioid requirement are associated with shorter progression-free survival and overall survival in patients with metastatic prostate cancer. Nevertheless, clinical practice should not be changed until prospective randomized trials show that opioid use is associated with inferior clinical outcomes, and that abrogation of the peripheral activities of opioids ameliorates this effect.

In vivo and in vitro inhibition of human liver cancer progress by downregulation of the μ-opioid receptor and relevant mechanisms

Opiates have long been used as analgesics to relieve pain associated with various medical conditions. μ-opioid receptor (MOR) is the main member of the opioid receptor super-family and the excitation or overexpression of MOR promotes the proliferation of many kinds of tumor cells. It was found in our previous studies that MOR was highly expressed in the tissue and cells of human liver cancer. However, the impact of MOR on the progress of human liver cancer remains unknown. The purpose of this study is to investigate the impact of MOR downregulation on the progress of human liver cancer and the mechanisms involved. RNA interfering or specific inhibitor was administered to downregulate the MOR in human hepato-cellular carcinoma cells and it was found that the proliferation of hepatocellular carcinoma cells was significantly inhibited with the increase of the apoptotic rate, while the cell cycle was blocked in G0/G1 phase and the tumor growth in the mice was retarded. In addition, downregulation of MOR resulted in the increase of phosphorylation of the MKK7 expression and JNK activation. On the contrary, blockade of MKK7 pathway can reverse the antitumor role of MOR. In summary, downregulation of MOR is able to inhibit both in vivo and in vitro human liver cancer progress and it shows potential to be used in cancer therapy.

Can anaesthetic and analgesic techniques affect cancer recurrence or metastasis?

Cancer is a leading cause of morbidity and mortality worldwide and the ratio of incidence is increasing. Mortality usually results from recurrence or metastases. Surgical removal of the primary tumour is the mainstay of treatment, but this is associated with inadvertent dispersal of neoplastic cells into the blood and lymphatic systems. The fate of the dispersed cells depends on the balance of perioperative factors promoting tumour survival and growth (including surgery per se, many anaesthetics per se, acute postoperative pain, and opioid analgesics) together with the perioperative immune status of the patient. Available evidence from experimental cell culture and live animal data on these factors are summarized, together with clinical evidence from retrospective studies. Taken together, current data are sufficient only to generate a hypothesis that an anaesthetic technique during primary cancer surgery could affect recurrence or metastases, but a causal link can only be proved by prospective, randomized, clinical trials. Many are ongoing, but definitive results might not emerge for a further 5 yr or longer. Meanwhile, there is no hard evidence to support altering anaesthetic technique in cancer patients, pending the outcome of the ongoing clinical trials.

The effects of anesthetics on tumor progression

More and more cancer patients receive surgery and chronic pain control. Cell-mediated immunosuppression from surgical stress renders perioperative period a vulnerable period for tumor metastasis. Retrospective studies suggest that regional anesthesia reduces the risk of tumor metastasis and recurrence. This benefit may be due to the attenuation of immunosuppression by regional anesthesia. On the other hand, accumulating evidence points to a direct role of anesthetics in tumor progression. A variety of malignancies exhibit increased activity of voltage-gated sodium channels. Blockade of these channels by local anesthetics may help inhibit tumor progression. Opioids promote angiogenesis, cancer cell proliferation and metastasis. It will be interesting to examine the therapeutic potential of peripheral opioid antagonists against malignancy. Volatile anesthetics are organ-protective against hypoxia, however; this very protective mechanism may lead to tumor growth and poor prognosis. In this review, we examine the direct effects of anesthetics in tumor progression in hope that a thorough understanding will help to select the optimal anesthetic regimens for better outcomes in cancer patients.

Methylnaltrexone for the treatment of opioid-induced constipation

Opioids are the drugs of choice for treating moderate-to-severe pain, especially for patients in the end stage of cancer or other advanced illnesses, and also in critical care or for the treatment of chronic pain. Side effects such as nausea, pruritus, dizziness and constipation have to be controlled in order to use these drugs to their full potential. Opioid-induced bowel syndrome and constipation caused by activation of μ-receptors in the gut can have such distressing effects that some patients prefer to forego adequate pain control. Methylnaltrexone is a μ-opioid receptor antagonist that, unlike naltrexone or naloxone, does not pass the blood-brain barrier, and therefore does not impair the centrally mediated analgesic effect of opioids. It is licensed for the treatment of opioid-induced constipation in palliative care in more than 50 countries. This article presents practically relevant pharmacological data, basic research results and evidence from clinical research about methylnaltrexone, and outlines potential future therapeutic options for this promising drug.

Endogenous opiates and behavior: 2011

This paper is the thirty-fourth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2011 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 (Section 16); and immunological responses (Section 17).

Prognostic significance of opioid use in the active treatment of advanced colorectal cancer

This study aimed to evaluate the oncologic significance of opioid use during active treatment for advanced colorectal cancer (CRC). The patients included in this study underwent therapeutic chemotherapy for metastatic and/or recurrent CRC. The primary outcomes measured were the characteristics of CRC patients who were administered opioid to maintain compliance with cancer treatments as well as the impact of opioid use on cancer-specific survival. Of the 245 patients, 117 (48%) were administered opioid during chemotherapy. No significant associations were detected between opioid use and clinicopathological factors, with the exception of age (<65 or ≥65 years; P= 0.0281), pathology (differentiated or undifferentiated; P= 0.0007) and response rate to chemotherapy (P= 0.0056). Patients administered opioid had significantly poorer cancer-specific survival compared to patients who did not receive opioid. The mean cancer-specific survival periods were 606±57 days (chemotherapy with opioid), <636±46 days (chemotherapy without opioid), <1140±95 days (multimodal therapy with opioid) and <1556±160 days (multimodal therapy without opioid). Additionally, oncologic emergencies due to cancer progression were significantly correlated with opioid use (P=0.0002), although no statistically significant differences were detected between the cancer-specific survival period and oncologic emergencies. The use of opioid to maintain compliance with active cancer therapy is advised in modern CRC management. However, CRC patients that were administered opioid may have potential progressive disease, thus clinicians need to be aware of the oncologic emergencies possibly arising during an active CRC therapy.

Anesthesia in patients with cancer disorders

PURPOSE OF REVIEW

Along with the increasing population of elderly people in developed countries, anesthesiologists have increasing opportunities to anesthetize cancer patients in their routine work. However, no guideline of anesthesia procedures for cancer patients is available even though guidelines of operative procedures have been formulated for different types of cancer. This review provides recent findings related to the optimal choice of anesthetics and adequate anesthesia management for cancer patients.

RECENT FINDINGS

The intrinsic weapon fighting cancer cells is competent immune cells, particularly CD4+ T helper 1-type cells, CD8+ cytotoxic T cells, and natural killer cells. However, surgical inflammation, some anesthetics, and inadvertent anesthesia management suppress these effector cells and induce suppressive immune cells, which render cancer patients susceptible to tumor recurrence and metastasis after surgery.

SUMMARY

Accumulated basic and clinical data suggest that total intravenous anesthesia with propofol, cyclooxygenase antagonists, and regional anesthesia can decrease negative consequences associated with perioperative immunosuppression. Volatile anesthesia, systemic morphine administration, unnecessary blood transfusions, intraoperative hypoxia, hypotension, hypothermia, and hyperglycemia should be avoided.

A new approach to reducing postsurgical cancer recurrence: perioperative targeting of catecholamines and prostaglandins

Surgery is a crucial intervention in most cancer patients, but the perioperative period is characterized by increased risks for future outbreak of preexisting micrometastases and the initiation of new metastases-the major cause of cancer-related death. Here we argue that the short perioperative period is disproportionately critical in determining long-term recurrence rates, discuss the various underlying risk factors that act synergistically during this period, and assert that this time frame presents an unexplored opportunity to reduce long-term cancer recurrence. We then address physiologic mechanisms that underlie these risk factors, focusing on excess perioperative release of catecholamines and prostaglandins, which were recently shown to be prominent in facilitating cancer recurrence through their direct impact on the malignant tissue and its microenvironment, and through suppressing antimetastatic immunity. The involvement of the immune system is further discussed in light of accumulating evidence in cancer patients, and given the recent identification of endogenously activated unique leukocyte populations which, if not suppressed, can destroy autologous "immune-resistant" tumor cells. We then review animal studies and human correlative findings, suggesting the efficacy of blocking catecholamines and/or prostaglandins perioperatively, limiting metastasis and increasing survival rates. Finally, we propose a specific perioperative pharmacologic intervention in cancer patients, based on simultaneous β-adrenergic blockade and COX-2 inhibition, and discuss specific considerations for its application in clinical trials, including our approved protocol. In sum, we herein present the rationale for a new approach to reduce long-term cancer recurrence by using a relatively safe, brief, and inexpensive intervention during the perioperative period.

[Perioperative tumour dissemination. 2. Effects of anaesthesia and analgesia]

There has been growing concern over the last few years on the effect that the anaesthetic drugs used during oncological surgery could have on long-term tumour progression. In laboratory studies, it has been observed how some substances used during the anaesthetic procedure influence tumour immunosurveillance, cell proliferation or tumour angiogenesis processes. The possible clinical relevance of the anaesthetic technique used as regards long-term tumour progression and survival is still to be determined. However, based on retrospective studies, it appears that those anaesthetic techniques combined with the use of regional anaesthesia and analgesia may be beneficial compared to those that are maintained on the use of opioids. Further research should help to clarify the long-term clinical relevance of the anaesthetic process during oncological surgery.

μ-Opioid receptor gene A118G polymorphism predicts survival in patients with breast cancer

BACKGROUND

Preclinical studies suggest that opioids may promote tumor growth. Genetic polymorphisms have been shown to affect opioid receptor function and to modify the clinical effects of morphine. In this study we assessed the association between six common polymorphisms in the μ-opioid receptor gene, including the well known A118G polymorphism, and breast cancer survival.

METHODS

A total of 2,039 women ages 23-74 yr (38% African-American, 62% European-American, 55% postmenopausal) diagnosed with breast cancer between 1993-2001 were followed through 2006. Genotyping was performed using the TaqMan platform (Applied Biosystems Inc., Foster City, CA). Kaplan-Meier curves, log-rank tests, and Cox proportional hazard models were used to examine the association between each genotype and survival.

RESULTS

After Bonferroni correction for multiple testing, patient genotype at A118G was associated with breast cancer-specific mortality at 10 yr. Women with one or more copies of the G allele had decreased breast cancer-specific mortality (P < 0.001). This association was limited to invasive cases only; effect size appeared to increase with clinical stage. Cox regression model adjusted for age and ethnicity also showed decreased mortality in A/G and G/G genotypes compared with A/A genotype (hazard ratio = 0.57 [0.38, 0.85] and 0.32 [0.22, 0.49], respectively; P = 0.006).

CONCLUSIONS

These results suggest that opioid pathways may be involved in tumor growth. Further studies examining the association between genetic variants influencing opioid system function and cancer survival are warranted.

Influence of morphine on pericyte-endothelial interaction: implications for antiangiogenic therapy

Morphine stimulates tumor angiogenesis and cancer progression in mice. We examined if morphine influences endothelial-pericyte interaction via platelet-derived growth factor-BB (PDGF-BB) and PDGF receptor-β (PDGFR-β). Clinically relevant doses of morphine stimulated PDGF-BB secretion from human umbilical vein endothelial cells and activated PDGFR-β and mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) phosphorylation in human pericytes. These in vitro effects of morphine were translated into promotion of tumor angiogenesis in a transgenic mice model of breast cancer when treated with clinically used dose of morphine. Increased vessel-associated immunoreactivity of desmin and PDGFR-β was observed on pericytes in tumors of morphine-treated mice. These data suggest that morphine potentiates endothelial-pericyte interaction via PDGF-BB/PDGFR-β signaling and promotes tumor angiogenesis, pericyte recruitment, and coverage of tumor vessels. We speculate that morphine may impair the effectiveness of antiangiogenic therapy by influencing vascular pericyte coverage.

Morphine-induced epidermal growth factor pathway activation in non-small cell lung cancer

BACKGROUND

Epidermal growth factor receptor (EGFR) is coactivated by the μ-opioid receptor (MOR), expressed on non-small cell lung cancer (NSCLC) cells and human lung cancer. We hypothesized that clinically used opioid analgesics that are MOR agonists coactivate EGFR, resulting in growth- and survival-promoting signaling.

METHODS

We used H2009, a human adenocarcinoma NSCLC cell line, with constitutive EGFR phosphorylation, which showed increased expression of MOR and the δ-opioid receptor by reverse transcriptase polymerase chain reaction. We used Western immunoblotting, magnetic bead-based Bio-Plex cytokine assay, immunofluorescent staining, BrdU incorporation enzyme-linked immunosorbent assay, and BioCoat™ Matrigel™ invasion assay to examine cell signaling, cytokine expression, colocalization of MOR and EGFR in human lung cancer, and cell proliferation and invasion, respectively.

RESULTS

Similar to epidermal growth factor (EGF), morphine stimulated phosphorylation of EGFR, Akt/protein kinase B (Akt), and mitogen-activated protein kinase/extracellular signal regulated kinase (MAPK/ERK) signaling in H2009 cells. Opioid receptor (OR) antagonist, naloxone, EGFR tyrosine kinase inhibitor, erlotinib, and silencing of MOR and δ-opioid receptor abrogated morphine- and EGF-induced phosphorylation of signaling, suggestive of OR-mediated coactivation of EGFR. H2009 cells secreted significantly higher levels of cytokines compared with control Beas2B epithelial cells. H2009-conditioned medium stimulated MOR expression in Beas2B cells, suggesting that cytokines secreted by H2009 may be associated with increased OR expression in H2009. We observed colocalization of EGFR and MOR, in human NSCLC tissue. Functionally, morphine- and EGF-induced proliferation and invasion of H2009 cells was ameliorated by naloxone as well as erlotinib.

CONCLUSION

Morphine-induced phosphorylation of EGFR occurs via ORs, leading to downstream MAPK/ERK, Akt phosphorylation, cell proliferation, and increased invasion. Notably, ORs are also associated with EGF-induced phosphorylation of EGFR. Increased coexpression of MOR and EGFR in human lung cancer suggests that morphine may have a growth-promoting effect in lung cancer.

Morphine use in cancer surgery

Morphine is the core of perioperative pain management. However, when it comes to cancer surgery the possibility that this drug might affect tumor recurrence and metastasis has raised concerns. The results of two recent retrospective clinical trials indicated that regional anesthesia/analgesia might be beneficial in prostate and breast cancer surgery. It was proposed that morphine could be responsible for the higher recurrence and mortality rate observed in the general anesthesia/opioid analgesia groups. Nevertheless, the results of several other retrospective studies and one randomized prospective trial failed to confirm any advantage for regional anesthesia/analgesia over general anesthesia and opioid analgesia. Moreover laboratory data on the effect of morphine on cancer are contradictory, ranging from tumor-promoting to anti-tumor effects. Considering that surgical stress and pain promote the recurrence and spread of cancer, choosing a proper analgesic strategy is of high significance. Although the question of whether morphine causes any harm to cancer patients remains unanswered, alternative analgesic regimens could be used concomitant to or instead of morphine to limit its potential adverse effects.