A number of lines of evidence suggest that immunotherapy with the cytokine interleukin-2 (IL-2) may boost the immune system to fight tumors. CD4+ T cells, the cells that orchestrate the immune response, use these cytokines as signaling mechanisms for immune-response stimulation as well as lymphocyte stimulation, growth, and differentiation. Because tumor cells begin as 'self', the immune system may not respond in an effective way to eradicate them. Adoptive cellular immunotherapy can potentially restore or enhance these effects. We illustrate through mathematical modeling the dynamics between tumor cells, immune-effector cells, and IL-2. These efforts are able to explain both short tumor oscillations in tumor sizes as well as long-term tumor relapse. We then explore the effects of adoptive cellular immunotherapy on the model and describe under what circumstances the tumor can be eliminated.

https://www.math.unl.edu/~bdeng1/Teaching/math943/Topics/Cancer%20Modeling/References/Kirshner98.pdf

Modeling immunotherapy of the tumor-immune interaction.

Endogenous melatonin is synthesized from tryptophan via 5-hydroxytryptamine. It is considered an indoleamine from a biochemical point of view because the melatonin molecule contains a substituted indolic ring with an amino group. The circadian production of melatonin by the pineal gland explains its chronobiotic influence on organismal activity, including the endocrine and non-endocrine rhythms. Other functions of melatonin, including its antioxidant and anti-inflammatory properties, its genomic effects, and its capacity to modulate mitochondrial homeostasis, are linked to the redox status of cells and tissues. With the aid of specific melatonin antibodies, the presence of melatonin has been detected in multiple extrapineal tissues including the brain, retina, lens, cochlea, Harderian gland, airway epithelium, skin, gastrointestinal tract, liver, kidney, thyroid, pancreas, thymus, spleen, immune system cells, carotid body, reproductive tract, and endothelial cells. In most of these tissues, the melatonin-synthesizing enzymes have been identified. Melatonin is present in essentially all biological fluids including cerebrospinal fluid, saliva, bile, synovial fluid, amniotic fluid, and breast milk. In several of these fluids, melatonin concentrations exceed those in the blood. The importance of the continual availability of melatonin at the cellular level is important for its physiological regulation of cell homeostasis, and may be relevant to its therapeutic applications. Because of this, it is essential to compile information related to its peripheral production and regulation of this ubiquitously acting indoleamine. Thus, this review emphasizes the presence of melatonin in extrapineal organs, tissues, and fluids of mammals including humans.

Extrapineal melatonin: sources, regulation, and potential functions.

Melatonin, or 5-methoxy-N-acetyltryptamine, is synthesized and released by the pineal gland and locally in the retina following a circadian rhythm, with low levels during the day and elevated levels at night. Melatonin activates two high-affinity G protein-coupled receptors, termed MT1 and MT2, to exert beneficial actions in sleep and circadian abnormality, mood disorders, learning and memory, neuroprotection, drug abuse, and cancer. Progress in understanding the role of melatonin receptors in the modulation of sleep and circadian rhythms has led to the discovery of a novel class of melatonin agonists for treating insomnia, circadian rhythms, mood disorders, and cancer. This review describes the pharmacological properties of a slow-release melatonin preparation (i.e., Circadin®) and synthetic ligands (i.e., agomelatine, ramelteon, tasimelteon), with emphasis on identifying specific therapeutic effects mediated through MT1 and MT2 receptor activation. Discovery of selective ligands targeting the MT1 or the MT2 melatonin receptors may promote the development of novel and more efficacious therapeutic agents.

/pdf/mt1-and-mt2-melatonin-receptors-a-therapeutic-perspective-5dir3keb1a.pdf

MT1 and MT2 Melatonin Receptors: A Therapeutic Perspective

Melatonin, the chief secretory product of the pineal gland, is a direct free radical scavenger, an indirect antioxidant, as well as an important immunomodulatory agent. In both in vitro and in vivo investigations, melatonin protected healthy cells from radiation-induced and chemotherapeutic drug-induced toxicity. Furthermore, several clinical studies have demonstrated the potential of melatonin, either alone or in combination with traditional therapy, to yield a favorable efficacy to toxicity ratio in the treatment of human cancers. This study reviews the literature from laboratory investigations that document the antioxidant and oncostatic actions of melatonin and summarizes the evidence regarding the potential use of melatonin in cancer treatment. This study also provides rationale for the design of larger translational research-based clinical trials.

Melatonin: From Basic Research to Cancer Treatment Clinics

Ionizing radiation is classified as a potent carcinogen, and its injury to living cells is, to a large extent, due to oxidative stress. The molecule most often reported to be damaged by ionizing radiation is DNA. Hydroxyl radicals (*OH), considered the most damaging of all free radicals generated in organisms, are often responsible for DNA damage caused by ionizing radiation. Melatonin, N-acetyl-5-methoxytryptamine, is a well-known antioxidant that protects DNA, lipids, and proteins from free-radical damage. The indoleamine manifests its antioxidative properties by stimulating the activities of antioxidant enzymes and scavenging free radicals directly or indirectly. Among known antioxidants, melatonin is a highly effective scavenger of *OH. Melatonin is distributed ubiquitously in organisms and, as far as is known, in all cellular compartments, and it quickly passes through all biological membranes. The protective effects of melatonin against oxidative stress caused by ionizing radiation have been documented in in vitro and in vivo studies in different species and in in vitro experiments that used human tissues, as well as when melatonin was given to humans and then tissues collected and subjected to ionizing radiation. The radioprotective effects of melatonin against cellular damage caused by oxidative stress and its low toxicity make this molecule a potential supplement in the treatment or co-treatment in situations where the effects of ionizing radiation are to be minimized.

Antioxidative effects of melatonin in protection against cellular damage caused by ionizing radiation.

The biological significance of soluble interleukin-2 receptors in solid tumors.

Endocrine and immune effects of melatonin therapy in metastatic cancer patients

Increase in Soluble Interleukin-2 Receptor and Neopterin Serum Levels during Immunotherapy of Cancer with Interleukin-2

The capillary leak syndrome, responsible for fluid loss into the interstitial space, represents one of the major cardiovascular toxicities of IL-2 during the immunotherapy of cancer. The mechanisms involved in the increased vascular permeability have still to be better understood. The present study was carried out to investigate the role of the complement system in mediating the IL-2 vascular toxicity. The study was performed in metastatic renal cancer patients, treated with IL-2 through a 24-hour i.v. infusion at a daily dose of 3 x 10(6) U/m2 for 5 consecutive days, corresponding to one IL-2 course. Six IL-2 courses were evaluated. C3 and C4 were measured daily during IL-2 infusion, and 2 and 5 days after its interruption. IL-2 administration induced a significant decrease in both C3 and C4 mean levels, which became within the normal range 5 days after the end of IL-2 infusion. These results show that IL-2 administration may directly activate the complement system through the classical pathway, which might play a role in determining the increased vascular permeability.

Activation of the complement system during immunotherapy of cancer with interleukin-2: a possible explanation of the capillary leak syndrome.

Recent experiments suggest the possibility of modulating the efficacy of cancer endocrine therapy by the pineal hormone melatonin (MLT). In particular, it has been demonstrated that MLT may stimulate estrogen receptor (ER) expression and enhance tamoxifen (TMX) effects other than the antiestrogenic action. Therefore, MLT could amplify the efficacy of TMX also in patients with negative ER. On this basis, a randomized study was performed with TMX versus TMX plus MLT in ER-negative metastatic breast cancer patients, who were unable to tolerate further chemotherapy, because of age, low performance status and/or heavy chemotherapeutic pretreatment. The study included 40 ER-negative post-menopausal, metastatic breast cancer patients, who were randomized to receive TMX alone (20 mg/day orally) or TMX plus MLT (20 mg/day orally in the evening). No complete response was seen. Partial response rate was significantly higher in patients treated with TMX and MLT than in those, who received TMX alone (7/19 vs 2/21, p<0.05). Moreover, the percent of survival at 1 year was significantly higher in patients treated with TMX plus MLT than in those treated with TMX alone (12/19 vs 5/21, p<0.01). No MLT-related toxicity was observed; on the contrary, most patients receiving MLT experienced a relief of anxiety and of depression. This preliminary study suggests that the association of the pineal hormone MLT may make TMX effective also in ER-negative metastatic breast cancer patients.

A randomized study of tamoxifen alone versus tamoxifen plus melatonin in estrogen receptor-negative heavily pretreated metastatic breast-cancer patients.

Barni S

Papers

The biological significance of soluble interleukin-2 receptors in solid tumors.

Endocrine and immune effects of melatonin therapy in metastatic cancer patients

Increase in Soluble Interleukin-2 Receptor and Neopterin Serum Levels during Immunotherapy of Cancer with Interleukin-2

Activation of the complement system during immunotherapy of cancer with interleukin-2: a possible explanation of the capillary leak syndrome.

A randomized study of tamoxifen alone versus tamoxifen plus melatonin in estrogen receptor-negative heavily pretreated metastatic breast-cancer patients.