Targeting opioidergic pathways as a novel biological treatment for advanced pancreatic cancer

Research progress of opioid growth factor in immune-related diseases and cancer diseases

Methionine enkephalin (MENK) has an important role in both neuroendocrine and immune systems. MENK was known as an opioid growth factor (OGF) for its growth regulatory characteristics. OGF interacts with the OGF receptor (OGFr) to inhibit DNA synthesis by upregulating p16 and/or p21, which delays the cell cycle transition from G0/G1 to S phase, and inhibits cell proliferation. In addition, OGF combines with OGFr in immune cells to exert its immunomodulatory activity and regulate immune function. OGF has been studied as an immunomodulator in a variety of autoimmune diseases, including multiple sclerosis, inflammatory bowel disease, diabetes and viral infections, and has been proven to relieve symptoms of certain diseases in animal and in vitro experiments. Also, OGF and OGFr have various anti-tumor molecular mechanisms. OGF can be used as the primary therapy alone or combined with other drugs to treat tumors. This article summarizes the research progress of OGF in immune-related diseases and cancer diseases.

Survival features, prognostic factors, and determinants of diagnosis and treatment among Iranian patients with pancreatic cancer, a prospective study

OBJECTIVES

Investigating the survival features, and determinants of treatment and stage at presentation in Iran.

METHODS

461 patients with pancreatic ductal adenocarcinoma (PC) were prospectively enrolled from Shariati hospital, Tehran, Iran, between 2011-2018. All patients underwent endoscopic ultrasonography, computed tomography scanning, and physical examination. Validated questionnaire was completed for the participants and all were actively followed on monthly basis.

RESULTS

Median survival time was 6.5 months, and 1-, and 5-year survival rates were 26.2%, and 1.5%. Patients who were older (p<0.001), illiterate (p = 0.004), unmarried (p = 0.003), rural inhabitant (p = 0.013), opium user (p = 0.039), and had lower body mass index (BMI) (p = 0.002) had lower overall survival. Tumors located in the head of pancreas were more commonly diagnosed at lower stages (p<0.001). Only 10.4% of patients underwent surgery who were more commonly educated (p<0.001), married (p = 0.005), had a tumor located in the head of pancreas (p = 0.016), and were diagnosed at lower stages (p<0.001). After adjustment for potential confounders and risk factors, rural inhabitance (HR: 1.33 (95% CI: 1.01-1.74)), having more symptoms (HR for each increasing symptom: 1.06 (1.02-1.11)), using opium (HR: 1.51 (1.04-2.20)), having a tumor located in the body of pancreas (HR: 1.33 (1.02-1.75)), and having an advanced tumor stage (HR: 2.07 (1.34-3.19)) remained significantly associated with increased risk of mortality. After the adjusting for potential confounders, we did not find significant relationships between smoking, alcohol intake, and BMI with the risk of death among patients with pancreatic cancer.

CONCLUSIONS

Iranian patients with PC have very poor long-term survival. Besides tumor's stage and location, socioeconomic disparities could affect the probabilities of receiving treatment and/or survival in these patients. Opium use is an independent risk factor for mortality among PC patients in Iran.

Inhibition of the growth of human melanoma cells by methionine enkephalin

Melanoma is an aggressive cancer, the incidence of which is increasing worldwide. Limited therapies are currently available, particularly following metastasis. The aim of the present study was to investigate the inhibiting effect of methionine enkephalin (MENK) on human melanoma via opioid receptors. The results of the present study revealed that MENK markedly regulates the proliferation of A375 cells, causing cell cycle arrest in G0/G1 phase and a decrease in the percentage of cells in S and G2/M phases. Reverse transcription-quantitative polymerase chain reaction demonstrated that MENK treatment increased opioid receptor expression in A375 cells. Furthermore, the expression level of survivin, an inhibitory apoptotic protein, was 1.1% of the level in the control group in the MENK group following 48 h of treatment. In conclusion, the results of the present study revealed, to the best of our knowledge for the first time, that MENK may inhibit growth and induce apoptosis of A375 cells, and describes a potential mechanism underlying these effects. Therefore, MENK should be investigated as a primary therapy for human melanoma cancer and as an adjuvant to other chemotherapies. Further studies are required to develop an optimal strategy for the use of MENK for the treatment of human cancers.

Methionine enkephalin (MENK) improves lymphocyte subpopulations in human peripheral blood of 50 cancer patients by inhibiting regulatory T cells (Tregs)

MENK, a penta-peptide is considered as being involved in the regulatory feedback loop between the immune and neuroendocrine systems, with marked modulation of various functions of human immune cells. The aim of the present work was to investigate change of lymphocyte subpopulations in peripheral blood of 50 cancer patients before and after treatment with MENK. Peripheral blood mononuclear cells (PBMCs) of peripheral blood from 50 cancer patients were isolated by density gradient centrifugation using Ficoll-Paque solution and cultured with MENK. We measured proliferation of total nucleated cells, subpopulations of individual CD4+T cells, CD8+T cells, CD4+CD25+ regulatory T cells (Treg), natural killer cells (NK) before and after treatment with 10(-12)M MENK in cell culture by flow cytometry (FCM). Our results indicated that MENK showed a strong inhibiting effect on Treg cells while it stimulated marked proliferation of other lymphocyte subpopulations. All data obtained were of significance statistically. It was therefore concluded that MENK could work as a strong immune booster with great potential in restoring damaged human immune system and we could consider MENK as a drug to treat cancer patients, whose immune systems are damaged by chemotherapy or radiotherapy. Furthermore we could consider MENK as a chemotherapy additive, which would sustain immune system of cancer patients during the process of chemotherapy to get maximized efficacy with minimized side effect.

Isoquercitrin inhibits the progression of pancreatic cancer in vivo and in vitro by regulating opioid receptors and the mitogen-activated protein kinase signalling pathway

Pancreatic cancer is a common malignant tumour that affects individuals worldwide. In recent years, the incidence and mortality rates of pancreatic cancer have continuously increased. Currently, the primary clinical treatment methods for pancreatic cancer include surgical resection, chemotherapy and radiotherapy. However, these treatment methods rarely produce satisfactory therapeutic outcomes. Extensive research has also proven that the effective components of several traditional Chinese medicines, particularly flavonoids extracted from plants, have significant antitumour effects. Isoquercitrin, which is one of the flavonoids found in Bidens pilosa extracts, has a significant antitumour effect. However, the antitumour effect of isoquercitrin and its mechanism of action remain unclear. The objective of the present study was to investigate the effect of isoquercitrin on the progression of pancreatic cancer and to further understand the biological characteristics of the participation of isoquercitrin in the progression of pancreatic cancer. In vitro, we found that a therapeutic dose of isoquercitrin significantly inhibited proliferation, promoted apoptosis and induced cell cycle arrest within the G1 phase in pancreatic cancer cells. Isoquercitrin activated caspase-3, -8 and -9 and reduced the mitochondrial membrane potential. In addition, isoquercitrin inhibited the expression level of the δ opioid receptor; however, isoquercitrin had no effect on the κ and µ opioid receptors. Furthermore, isoquercitrin inhibited extracellular signal-regulated kinase (ERK) phosphorylation and promoted c-Jun N-terminal kinase (JNK) phosphorylation. In vivo, we found that a therapeutic dose of isoquercitrin significantly inhibited xenograft growth in nude mice. In summary, the present study demonstrated that isoquercitrin inhibits human pancreatic cancer progression in vivo and in vitro and that its molecular mechanism may be closely related to opioid receptors and to the activation of the mitogen-activated protein kinase (MAPK) signalling pathway.

Immunotherapy of cancer via mediation of cytotoxic T lymphocytes by methionine enkephalin (MENK)

The aim of this study was to investigate the immunological mechanisms by which synthetic methionine enkephalin (MENK) exerts therapeutic effects on tumor growth. Our findings in vivo or in vitro show that MENK treatment either in vivo or in vitro could up-regulate the percentages of CD8+T cells, induce markers of activated T cells, increased cytotoxic activity against mouse S180 tumor cells and increase secretion of IFNγ. In addition, the adoptively transferred CD8+T cells, after either in vitro or in vivo treatment with MENK, result in significantly increased survival of S180 tumor-bearing mice and significant shrinkage in tumor growth. Opioid receptors are detected on normal CD8+T cells and exposure to MENK leads to increased expression of opioid receptors. Interaction between MENK and the opioid receptors on CD8+T cells appears to be essential for the activation of CTL, since the addition of naltrexone (NTX), an opioid receptor antagonist, significantly inhibits all of the effects of MENK. The evidence obtained indicates that the MENK-induced T cell signaling is associated with a significant up-regulation of Ca2+ influx into the cytoplasm and the translocation of NFAT2 into nucleus, and these signaling effects are also inhibited by naltrexone.