Increased trace amine-associated receptor 1 (TAAR1) expression is associated with a positive survival rate in patients with breast cancer

Molecular Targets for Breast Cancer Therapy

Breast cancer is by far the most common cancer in women, and for a while, it surpassed lung cancer as the most diagnosed cancer, regardless of gender, in 2020 [...].

From odor to oncology: non-canonical odorant receptors in cancer

Odorant receptors, traditionally associated with olfaction as chemoreceptors, have been increasingly recognized for their presence and diverse functions in various non-nasal tissues throughout the body. Beyond their roles in sensory perception, emerging evidence suggests a compelling interplay between odorant receptors and cancer progression as well. Alongside the canonical GPCR odorant receptors, dysregulation of non-canonical odorant receptors such as trace amine-associated receptors (TAARs), formyl peptide receptors (FPRs), and membrane-spanning 4A family (MS4As) has been observed in various cancer types, suggesting their contributions to cancer progression. The roles of these non-canonical chemoreceptors in cancer are complex, with some receptors promoting tumorigenesis and others acting as tumor-suppressing factors upon activation, depending on the cancer type. These findings shed light on the potential of non-canonical odorant receptors as therapeutic targets and prognostic markers in cancer, inviting further exploration to unravel their precise mechanisms of action and implications in cancer biology. In this review, we provide a comprehensive overview of the intricate relationships between these chemoreceptors and various types of cancer, potentially paving the way for innovative odor-based therapeutics. Ultimately, this review discusses the potential development of novel therapeutic strategies targeting these non-canonical chemoreceptors.

Trace Amine-Associated Receptors and Monoamine-Mediated Regulation of Insulin Secretion in Pancreatic Islets

Currently, metabolic syndrome treatment includes predominantly pharmacological symptom relief and complex lifestyle changes. Trace amines and their receptor systems modulate signaling pathways of dopamine, norepinephrine, and serotonin, which are involved in the pathogenesis of this disorder. Trace amine-associated receptor 1 (TAAR1) is expressed in endocrine organs, and it was revealed that TAAR1 may regulate insulin secretion in pancreatic islet β-cells. For instance, accumulating data demonstrate the positive effect of TAAR1 agonists on the dynamics of metabolic syndrome progression and MetS-associated disease development. The role of other TAARs (TAAR2, TAAR5, TAAR6, TAAR8, and TAAR9) in the islet's function is much less studied. In this review, we summarize the evidence of TAARs' contribution to the metabolic syndrome pathogenesis and regulation of insulin secretion in pancreatic islets. Additionally, by the analysis of public transcriptomic data, we demonstrate that TAAR1 and other TAAR receptors are expressed in the pancreatic islets. We also explore associations between the expression of TAARs mRNA and other genes in studied samples and demonstrate the deregulation of TAARs' functional associations in patients with metabolic diseases compared to healthy donors.

Natural products derived from medicinal plants and microbes might act as a game-changer in breast cancer: a comprehensive review of preclinical and clinical studies

Breast cancer (BC) is the most prevalent neoplasm among women. Genetic and environmental factors lead to BC development and on this basis, several preventive - screening and therapeutic interventions have been developed. Hormones, both in the form of endogenous hormonal signaling or hormonal contraceptives, play an important role in BC pathogenesis and progression. On top of these, breast microbiota includes both species with an immunomodulatory activity enhancing the host's response against cancer cells and species producing proinflammatory cytokines associated with BC development. Identification of novel multitargeted therapeutic agents with poly-pharmacological potential is a dire need to combat advanced and metastatic BC. A growing body of research has emphasized the potential of natural compounds derived from medicinal plants and microbial species as complementary BC treatment regimens, including dietary supplements and probiotics. In particular, extracts from plants such as Artemisia monosperma Delile, Origanum dayi Post, Urtica membranacea Poir. ex Savigny, Krameria lappacea (Dombey) Burdet & B.B. Simpson and metabolites extracted from microbes such as Deinococcus radiodurans and Streptomycetes strains as well as probiotics like Bacillus coagulans and Lactobacillus brevis MK05 have exhibited antitumor effects in the form of antiproliferative and cytotoxic activity, increase in tumors' chemosensitivity, antioxidant activity and modulation of BC - associated molecular pathways. Further, bioactive compounds like 3,3'-diindolylmethane, epigallocatechin gallate, genistein, rutin, resveratrol, lycopene, sulforaphane, silibinin, rosmarinic acid, and shikonin are of special interest for the researchers and clinicians because these natural agents have multimodal action and act via multiple ways in managing the BC and most of these agents are regularly available in our food and fruit diets. Evidence from clinical trials suggests that such products had major potential in enhancing the effectiveness of conventional antitumor agents and decreasing their side effects. We here provide a comprehensive review of the therapeutic effects and mechanistic underpinnings of medicinal plants and microbial metabolites in BC management. The future perspectives on the translation of these findings to the personalized treatment of BC are provided and discussed.

The tremendous clinical potential of the microbiota in the treatment of breast cancer: the next frontier

Although significant advances have been made in the diagnosis and treatment of breast cancer (BC) in recent years, BC remains the most common cancer in women and one of the main causes of death among women worldwide. Currently, more than half of BC patients have no known risk factors, emphasizing the significance of identifying more tumor-related factors. Therefore, we urgently need to find new therapeutic strategies to improve prognosis. Increasing evidence demonstrates that the microbiota is present in a wider range of cancers beyond colorectal cancer. BC and breast tissues also have different types of microbiotas that play a key role in carcinogenesis and in modulating the efficacy of anticancer treatment, for instance, chemotherapy, radiotherapy, and immunotherapy. In recent years, studies have confirmed that the microbiota can be an important factor directly and/or indirectly affecting the occurrence, metastasis and treatment of BC by regulating different biological processes, such as estrogen metabolism, DNA damage, and bacterial metabolite production. Here, we review the different microbiota-focused studies associated with BC and explore the mechanisms of action of the microbiota in BC initiation and metastasis and its application in various therapeutic strategies. We found that the microbiota has vital clinical value in the diagnosis and treatment of BC and could be used as a biomarker for prognosis prediction. Therefore, modulation of the gut microbiota and its metabolites might be a potential target for prevention or therapy in BC.

The Expression of Trace Amine-Associated Receptors (TAARs) in Breast Cancer Is Coincident with the Expression of Neuroactive Ligand-Receptor Systems and Depends on Tumor Intrinsic Subtype

Currently, the contribution of trace amine-associated receptors (TAARs) to breast cancer (BC) is recognized, but their associations with various pathological characteristics are not yet understood. There is accumulated transcriptomic data for BC tumors, which are represented in publicly accessible databases. We estimated TAARs' (including TAAR1, TAAR2, TAAR5, TAAR6, TAAR8, and TAAR9) associations with BC stage, grade, and molecular subtypes in these data and identified that the expression of all TAARs was associated with more unfavorable cancer subtypes, including basal-like and HER2-positive tumors. Also, the significant upregulation of all TAARs was demonstrated in circulating tumor cells compared to the metastatic lesions. Considering that co-expressed genes are more likely to be involved in the same biologic processes, we analyzed genes that are co-expressed with TAARs in BC. These gene sets were enriched with the genes of the olfactory transduction pathway and neuroactive ligand-receptor interaction participants. TAARs are co-expressed with G-protein-coupled receptors of monoamine neurotransmitters including dopamine, norepinephrine, and serotonin as well as with other neuroactive ligand-specific receptors. Since TAAR1 is able to modulate the activity of monoamine receptors that are involved in the regulation of BC growth, TAAR1 and potentially other TAARs may be regarded as prospective therapeutic targets for breast cancer.

Study on endogenous inhibitors against PD-L1: cAMP as a potential candidate

The discovery of new anti-cancer drugs targeting the PD-1/PD-L1 pathway has been a research hotspot in recent years. In this study, biological affinity ultrafiltration (BAU), UPLC-HRMS, molecular dynamic (MD) simulations and molecular docking methods were applied to search for endogenous active compounds that can inhibit the binding of PD-L1 to PD-1. We screened dozens of potential cancer related endogenous compounds. Surprisingly, cyclic adenosine monophosphate (cAMP) was found to have a direct inhibitory effect on the PD-1/PD-L1 binding with an in vitro IC₅₀ value of about 36.4 ± 9.3 μM determined by homogeneous time-resolved fluorescence (HTRF) assay. cAMP could recover the proliferation of Jurkat T cells co-cultured with DU-145 cells and may suppress PD-L1 expression of DU-145 cells. cAMP was demonstrated to bind and induce PD-L1 dimerization by FRET assay, and also predicted by MD simulations and molecular docking. The finding of cAMP as a potential inhibitor directly targeting the PD-1/PD-L1 interaction could advance our understanding of the activity of endogenous compounds regulating PD-L1.

Understanding and harnessing triple-negative breast cancer-related microbiota in oncology

Bacterial inhabitants of the body have the potential to play a role in various stages of cancer initiation, progression, and treatment. These bacteria may be distal to the primary tumour, such as gut microbiota, or local to the tissue, before or after tumour growth. Breast cancer is well studied in this context. Amongst breast cancer types, Triple Negative Breast Cancer (TNBC) is more aggressive, has fewer treatment options than receptor-positive breast cancers, has an overall worse prognosis and higher rates of reoccurrence. Thus, an in-depth understanding of the bacterial influence on TNBC progression and treatment is of high value. In this regard, the Gut Microbiota (GM) can be involved in various stages of tumour progression. It may suppress or promote carcinogenesis through the release of carcinogenic metabolites, sustenance of proinflammatory environments and/or the promotion of epigenetic changes in our genome. It can also mediate metastasis and reoccurrence through interactions with the immune system and has been recently shown to influence chemo-, radio-, and immune-therapies. Furthermore, bacteria have also been found to reside in normal and malignant breast tissue. Several studies have now described the breast and breast tumour microbiome, with the tumour microbiota of TNBC having the least taxonomic diversity among all breast cancer types. Here, specific conditions of the tumour microenvironment (TME) - low O2, leaky vasculature and immune suppression - are supportive of tumour selective bacterial growth. This innate bacterial ability could enable their use as delivery agents for various therapeutics or as diagnostics. This review aims to examine the current knowledge on bacterial relevance to TNBC and potential uses while examining some of the remaining unanswered questions regarding mechanisms underpinning observed effects.

Hormonal Crosstalk Between Thyroid and Breast Cancer

Differentiated thyroid cancer and breast cancer account for a significant portion of endocrine-related malignancies and predominately affect women. As hormonally responsive tissues, the breast and thyroid share endocrine signaling. Breast cells are responsive to thyroid hormone signaling and are affected by altered thyroid hormone levels. Thyroid cells are responsive to sex hormones, particularly estrogen, and undergo protumorigenic processes upon estrogen stimulation. Thyroid and sex hormones also display significant transcriptional crosstalk that influences oncogenesis and treatment sensitivity. Obesity-related adipocyte alterations-adipocyte estrogen production, inflammation, feeding hormone dysregulation, and metabolic syndromes-promote hormonal alterations in breast and thyroid tissues. Environmental toxicants disrupt endocrine systems, including breast and thyroid homeostasis, and influence pathologic processes in both organs through hormone mimetic action. In this brief review, we discuss the hormonal connections between the breast and thyroid and perspectives on hormonal therapies for breast and thyroid cancer. Future research efforts should acknowledge and further explore the hormonal crosstalk of these tissues in an effort to further understand the prevalence of thyroid and breast cancer in women and to identify potential therapeutic options.

Nutritional and metabolic signalling through GPCRs

Deregulated metabolism is a well-known feature of several challenging diseases, including diabetes, obesity and cancer. Besides their important role as intracellular bioenergetic molecules, dietary nutrients and metabolic intermediates are released in the extracellular environment. As such, they may achieve unconventional roles as hormone-like molecules by activating cell-surface G-protein-coupled receptors (GPCRs) that regulate several pathophysiological processes. In this review, we provide an insight into the role of lactate, succinate, fatty acids, amino acids, ketogenesis-derived and β-oxidation-derived intermediates as extracellular signalling molecules. Moreover, the mechanisms by which their cognate metabolite-sensing GPCRs integrate nutritional and metabolic signals with specific intracellular pathways will be described. A better comprehension of these aspects is of fundamental importance to identify GPCRs as novel druggable targets.

Body Microbiota and Its Relationship With Benign and Malignant Breast Tumors: A Systematic Review

Breast cancer is the most frequent type of cancer as well as one of the main causes of cancer-related mortality in women. Human microbial dysbiosis, which has been related to a range of malignancies, is one of the variables that may impact the chance of developing breast disorders. In this review, we aimed to investigate the relationship between breast cancer and benign breast tumors with dysbiosis of the microbiome at different body sites. We performed a systematic review of MEDLINE, Scopus, Ovid, and Cochrane Library to identify original articles published until July 2020 that reported studies of breast disease and microbiota. Twenty-four original articles were included in the study, which looked at the features and changes in breast, gut, urine, lymph node, and sputum microbial diversity in patients with benign and malignant breast tumors. In breast cancer, the breast tissue microbiome demonstrated changes in terms of bacterial load and diversity; in benign breast tumors, the microbiome was more similar to a malignant tumor than to normal breast tissue. Triple-negative (TNBC) and triple-positive (TPBC) types of breast cancer have a distinct microbial pattern. Moreover, in breast cancer, gut microbiota displayed changes in the compositional abundance of some bacterial families and microbial metabolites synthesis. Our review concludes that breast carcinogenesis seems to be associated with microbial dysbiosis. This information can be further explored in larger-scale studies to guide new prophylactic, diagnostic, and therapeutic measures for breast cancer.

The involvement of oncobiosis and bacterial metabolite signaling in metastasis formation in breast cancer

Breast cancer, the most frequent cancer in women, is characterized by pathological changes to the microbiome of breast tissue, the tumor, the gut, and the urinary tract. Changes to the microbiome are determined by the stage, grade, origin (NST/lobular), and receptor status of the tumor. This year is the 50th anniversary of when Hill and colleagues first showed that changes to the gut microbiome can support breast cancer growth, namely that the oncobiome can reactivate excreted estrogens. The currently available human and murine data suggest that oncobiosis is not a cause of breast cancer, but can support its growth. Furthermore, preexisting dysbiosis and the predisposition to cancer are transplantable. The breast's and breast cancer's inherent microbiome and the gut microbiome promote breast cancer growth by reactivating estrogens, rearranging cancer cell metabolism, bringing about a more inflammatory microenvironment, and reducing the number of tumor-infiltrating lymphocytes. Furthermore, the gut microbiome can produce cytostatic metabolites, the production of which decreases or blunts breast cancer. The role of oncobiosis in the urinary tract is largely uncharted. Oncobiosis in breast cancer supports invasion, metastasis, and recurrence by supporting cellular movement, epithelial-to-mesenchymal transition, cancer stem cell function, and diapedesis. Finally, the oncobiome can modify the pharmacokinetics of chemotherapeutic drugs. The microbiome provides novel leverage on breast cancer that should be exploited for better management of the disease.

Trace Amine-Associated Receptor 1 (TAAR1) Is a Positive Prognosticator for Epithelial Ovarian Cancer

Trace amine-associated receptor 1 (TAAR1) is a G_αs- protein coupled receptor that plays an important role in the regulation of the immune system and neurotransmission in the CNS. In ovarian cancer cell lines, stimulation of TAAR1 via 3-iodothyronamine (T₁AM) reduces cell viability and induces cell death and DNA damage. Aim of this study was to evaluate the prognostic value of TAAR1 on overall survival of ovarian carcinoma patients and the correlation of TAAR1 expression with clinical parameters. Ovarian cancer tissue of n = 156 patients who were diagnosed with epithelial ovarian cancer (serous, n = 110 (high-grade, n = 80; low-grade, n = 24; unknown, n = 6); clear cell, n = 12; endometrioid, n = 21; mucinous, n = 13), and who underwent surgery at the Department of Obstetrics and Gynecology, University Hospital of the Ludwig-Maximilians University Munich, Germany between 1990 and 2002, were analyzed. The tissue was stained immunohistochemically with anti-TAAR1 and evaluated with the semiquantitative immunoreactive score (IRS). TAAR1 expression was correlated with grading, FIGO and TNM-classification, and analyzed via the Spearman’s rank correlation coefficient. Further statistical analysis was obtained using nonparametric Kruskal-Wallis rank-sum test and Mann-Whitney-U-test. This study shows that high TAAR1 expression is a positive prognosticator for overall survival in ovarian cancer patients and is significantly enhanced in low-grade serous carcinomas compared to high-grade serous carcinomas. The influence of TAAR1 as a positive prognosticator on overall survival indicates a potential prognostic relevance of signal transduction of thyroid hormone derivatives in epithelial ovarian cancer. Further studies are required to evaluate TAAR1 and its role in the development of ovarian cancer.

L-Dopa-Decarboxylase (DDC) Is a Positive Prognosticator for Breast Cancer Patients and Epinephrine Regulates Breast Cancer Cell (MCF7 and T47D) Growth In Vitro According to Their Different Expression of Gi- Protein- Coupled Receptors

A coherence between thyroid dysfunction and breast cancer incidence exists. Thyroid hormone metabolites bind to TAAR1 (trace amine-associated receptor 1) and through that modulate the serotonergic and dopaminergic system. Catecholamines themselves are synthesized by the L-dopa decarboxylase (DDC). The aim of our study was to analyze the influence of catecholamines on the DDC expression in primary breast cancer patients and the role of DDC concerning overall survival (OS). DDC expression was analyzed by immunohistochemistry. The effect of epinephrine on the expression of DDC and the Gi- protein was analyzed on the protein level via Western blot. A viability assay was performed to test the metabolic cell viability. The overexpression of DDC in the primary tumor was associated with longer OS (p = 0.03). Stimulation with epinephrine induced the downregulation of DDC (p = 0.038) and significantly increased viability in T47D cells (p = 0.028). In contrast, epinephrine induced an upregulation of DDC and decreased the proliferation of MCF7 cells (p = 0.028). Epinephrine led to an upregulation of Gi protein expression in MCF7 cells (p = 0.008). DDC is a positive prognostic factor for OS in breast cancer patients, and it is regulated through epinephrine differently in MCF7 and T47D. DDC may represent a novel target for the treatment of breast cancer, especially concerning its interaction with epinephrine.

Metabolite Sensing GPCRs: Promising Therapeutic Targets for Cancer Treatment?

G-protein-coupled receptors constitute the most diverse and largest receptor family in the human genome, with approximately 800 different members identified. Given the well-known metabolic alterations in cancer development, we will focus specifically in the 19 G-protein-coupled receptors (GPCRs), which can be selectively activated by metabolites. These metabolite sensing GPCRs control crucial processes, such as cell proliferation, differentiation, migration, and survival after their activation. In the present review, we will describe the main functions of these metabolite sensing GPCRs and shed light on the benefits of their potential use as possible pharmacological targets for cancer treatment.

Cadaverine and Spermine Elicit Ca2+ Uptake in Human CP Cells via a Trace Amine-Associated Receptor 1 Dependent Pathway

The choroid plexus (CP) constitutes a barrier between the blood and the cerebrospinal fluid (CSF) which regulates the exchange of substances between these two fluids through mechanisms that are not completely understood. Polyamines as spermine, spermidine and putrescine are produced by all cells and are present in the CSF. Interestingly, their levels are altered in some neuronal disorders as Alzheimer's and Parkinson's diseases, thus increasing the interest in their signalling in the central nervous system (CNS). Cadaverine, on the other hand, is synthetized by the intestinal microbiome, suggesting that the presence of this bacterial metabolite in the CSF requires that it is up taken to the CNS across brain barriers. We knew that polyamines are detected by the olfactory signalling cascade operating at the CP, but the receptor involved had not been identified. The zebrafish TAAR13c was the only receptor known to bind a polyamine-cadaverine. Thus, we searched for a human receptor with homology to TAAR13c and found that some human TAARs including TAAR1 showed great homology. Then, we confirmed the expression of TAAR1 mRNA and protein in a human cell line of the CP, and in human CP samples. Calcium imaging assays after TAAR1 knockdown in these cells with a specific siRNA against TAAR1 showed a consistent reduction in the responses of these cells to cadaverine and spermidine, but not to spermine, suggesting that TAAR1 is activated by cadaverine and spermidine, but not spermine.

Modulatory effects of Xihuang Pill on lung cancer treatment by an integrative approach

Lung cancer has a rapidly increasing incidence and remains the highest ranked cancer in terms of mortality worldwide. Xihuang Pill(XHW), a famous four-herb traditional Chinese formulation, has been used to treat lung cancer in China for more than 100 years. It is usually prescribed as a complementary and alternative medicine for cancer therapy. However, the main active ingredients of XHW that treat lung cancer and their regulatory effects remain unclear. Here, we revealed modulatory effects effects of XHW on lung cancer in a mouse model of Lewis lung cancer (LLC) by a comprehensive strategy combining network pharmacology with metabolomics. The results demonstrated that XHW inhibited tumour growth in this model. Additionally, 11 differentially expressed metabolites were identified in the XHW group compared to those in the model group or normal group by untargeted metabolomics. They were enriched in amino acid-related metabolic pathways, and the top three pathways were phenylalanine metabolism; phenylalanine, tyrosine and tryptophan biosynthesis; and aminoacyl-tRNA biosynthesis. A total of 107 active components derived from Niuhuang, Shexiang, Ruxiang and Moyao, directly acted on 13 important targets (NR3C2, AKR1D1, MPO, PNP, NT5E, TAAR1, ADRB2, ADRB1, ADRA1A, ADRA2B, ADRA2A, MAOA and MAOB) to regulate 4 metabolites (L-phenylalanine, l-adrenaline, corticosterone and guanosine). Our results suggested that the key metabolites of XHW involved in the treatment of lung cancer were regulated by a multi-component and multi-target interaction network. This research elucidated the modulatory effect and therapeutic advantages of XHW treatment for lung tumours through an integrated approach.

Systematic expression analysis of WEE family kinases reveals the importance of PKMYT1 in breast carcinogenesis

OBJECTIVES

Many cancer cells depend on G2 checkpoint mechanism regulated by WEE family kinases to maintain genomic integrity. The PKMYT1 gene, as a member of WEE family kinases, participates in G2 checkpoint surveillance and probably links with tumorigenesis, but its role in breast cancer remains largely unclear.

MATERIALS AND METHODS

In this study, we used a set of bioinformatic tools to jointly analyse the expression of WEE family kinases and investigate the prognostic value of PKMYT1 in breast cancer.

RESULTS

The results indicated that PKMYT1 is the only frequently overexpressed member of WEE family kinases in breast cancer. KM plotter data suggests that abnormally high expression of PKMYT1 predicts poor prognosis, especially for some subtypes, such as luminal A/B and triple-negative (TNBC) types. Moreover, the up-regulation of PKMYT1 was associated with HER2-positive (HER2+), basal-like (Basal-like), TNBC statuses and increased classifications of Scarff, Bloom and Richardson (SBR). Co-expression analysis showed PKMYT1 has a strong positive correlation with Polo-like kinase 1 (PLK1), implying they may cooperate in regulating cancer cell proliferation by synchronizing rapid cell cycle with high quality of genome maintenance.

CONCLUSIONS

Collectively, this study demonstrates that overexpression of PKMYT1 is always found in breast cancer and predicts unfavourable prognosis, implicating it as an appealing therapeutic target for breast carcinoma.

TAAR1 levels and sub-cellular distribution are cell line but not breast cancer subtype specific

Trace amine-associated receptors are G protein-coupled receptors of which TAAR1 is the most well-studied. Recently, Vattai et al. (J Cancer Res Clin Oncol 143:1637-1647 https://doi.org/10.1007/s00432-017-2420-8 , 2017) reported that expression of TAAR1 may be a marker of breast cancer (BC) survival, with a positive correlation also suggested between TAAR1 expression and HER2 positivity. Neither a role for TAAR1 in breast tissue, nor in cancer, had previously been suspected. We, therefore, sought to provide independent validation and to further examine these putative relationships. First, a bioinformatic analysis on 58 total samples including normal breast tissue, BC-related cell lines, and tumour samples representing different BC sub-types found no clear correlation between TAAR1 mRNA levels and any BC subtype, including HER2 + . We next confirmed the bioinformatics data correlated to protein expression using a well validated anti-human TAAR1 antibody. TAAR1 mRNA levels correlated with the relative intensity of immunofluorescence staining in six BC cell lines (MCF-7, T47D, MDA-MB-231, SKBR3, MDA-MB-468, BT-474), but not in the MCF-10A immortalized mammary gland line, which had high mRNA but low protein levels. As expected, TAAR1 protein was intracellular in all cell lines. Surprisingly MCF-7, SKBR3, and MDA-MB-468 showed pronounced nuclear localization. The relative protein expression in MCF-7, MDA-MB-231, and MCF-10A lines was further confirmed by semi-quantitative flow cytometry. Finally, we demonstrate that the commercially available anti-TAAR1 antibody has poor selectivity, which likely explains the lack of correlation with the previous study. Therefore, while we clearly demonstrate variable expression and sub-cellular localization of TAAR1 across BC cell lines, we find no evidence for association with BC subtype.

Microbiome-Microbial Metabolome-Cancer Cell Interactions in Breast Cancer-Familiar, but Unexplored

Breast cancer is a leading cause of death among women worldwide. Dysbiosis, an aberrant composition of the microbiome, characterizes breast cancer. In this review we discuss the changes to the metabolism of breast cancer cells, as well as the composition of the breast and gut microbiome in breast cancer. The role of the breast microbiome in breast cancer is unresolved, nevertheless it seems that the gut microbiome does have a role in the pathology of the disease. The gut microbiome secretes bioactive metabolites (reactivated estrogens, short chain fatty acids, amino acid metabolites, or secondary bile acids) that modulate breast cancer. We highlight the bacterial species or taxonomical units that generate these metabolites, we show their mode of action, and discuss how the metabolites affect mitochondrial metabolism and other molecular events in breast cancer. These metabolites resemble human hormones, as they are produced in a "gland" (in this case, the microbiome) and they are subsequently transferred to distant sites of action through the circulation. These metabolites appear to be important constituents of the tumor microenvironment. Finally, we discuss how bacterial dysbiosis interferes with breast cancer treatment through interfering with chemotherapeutic drug metabolism and availability.

Thyronamine regulation of TAAR1 expression in breast cancer cells and investigation of its influence on viability and migration

Objectives

A correlation exists between breast cancer and thyroid disorders, which are common in elderly women. Thyroid hormones are degraded into trace amines, which can bind to the G-protein-coupled receptor trace amine-associated receptor 1 (TAAR1) and thereby activate it. The transformation of thyroid hormones into trace amines is carried out by the ornithine decarboxylase. Previously, we showed that TAAR1 overexpression (IRS ≥6) was associated with a significantly longer OS in primary breast cancer patients during a long-term follow-up of up to 14 years. Aim of the present study was to analyze the regulation of TAAR1 in breast cancer cell lines and the influence of triiodothyronine (T₃), thyronamines, and tetraiodothyroacetic acid (Tetrac) on the expression of TAAR1 in breast cancer cells.

Methods

The effect of T₃, thyronamines, and Tetrac on the expression of TAAR1 in breast cancer cell lines MCF-7 and T47D was analyzed via PCR and Western blot. A MTT assay was performed to test the metabolic cell viability. A scratch assay was performed to analyze cell migration.

Results

Stimulation of MCF-7 cells with 10 nM 3-iodothyronamine (T₁AM) significantly increased TAAR1 protein expression (P=0.008). In T47D cells, TAAR1 expression was significantly upregulated after the addition of 10 µg/mL estradiol to 10 nM T₁AM (P=0.008). A significant (P=0.028) reduction in MCF-7 cell viability through the incubation with T₁AM could be detected. Cell migration of MCF cells was significantly reduced through incubation with 10 nM T₁AM.

Conclusion

A significant upregulation of TAAR1 induced by stimulation with T₁AM may be a sign for an increased decarboxylation of thyroid hormones in breast cancer cells. In addition, there seems to be an influence of estradiol for the T₁AM-induced upregulation of TAAR1 in T47D cells. TAAR1-related cell transduction mechanisms seem to be an interesting target for endocrine treatment options of breast cancer patients.

Cadaverine, a metabolite of the microbiome, reduces breast cancer aggressiveness through trace amino acid receptors

Recent studies showed that changes to the gut microbiome alters the microbiome-derived metabolome, potentially promoting carcinogenesis in organs that are distal to the gut. In this study, we assessed the relationship between breast cancer and cadaverine biosynthesis. Cadaverine treatment of Balb/c female mice (500 nmol/kg p.o. q.d.) grafted with 4T1 breast cancer cells ameliorated the disease (lower mass and infiltration of the primary tumor, fewer metastases, and lower grade tumors). Cadaverine treatment of breast cancer cell lines corresponding to its serum reference range (100–800 nM) reverted endothelial-to-mesenchymal transition, inhibited cellular movement and invasion, moreover, rendered cells less stem cell-like through reducing mitochondrial oxidation. Trace amino acid receptors (TAARs), namely, TAAR1, TAAR8 and TAAR9 were instrumental in provoking the cadaverine-evoked effects. Early stage breast cancer patients, versus control women, had reduced abundance of the CadA and LdcC genes in fecal DNA, both responsible for bacterial cadaverine production. Moreover, we found low protein expression of E. coli LdcC in the feces of stage 1 breast cancer patients. In addition, higher expression of lysine decarboxylase resulted in a prolonged survival among early-stage breast cancer patients. Taken together, cadaverine production seems to be a regulator of early breast cancer.

Trace Amines and Their Receptors

Trace amines are endogenous compounds classically regarded as comprising β-phenylethyalmine, p-tyramine, tryptamine, p-octopamine, and some of their metabolites. They are also abundant in common foodstuffs and can be produced and degraded by the constitutive microbiota. The ability to use trace amines has arisen at least twice during evolution, with distinct receptor families present in invertebrates and vertebrates. The term "trace amine" was coined to reflect the low tissue levels in mammals; however, invertebrates have relatively high levels where they function like mammalian adrenergic systems, involved in "fight-or-flight" responses. Vertebrates express a family of receptors termed trace amine-associated receptors (TAARs). Humans possess six functional isoforms (TAAR1, TAAR2, TAAR5, TAAR6, TAAR8, and TAAR9), whereas some fish species express over 100. With the exception of TAAR1, TAARs are expressed in olfactory epithelium neurons, where they detect diverse ethological signals including predators, spoiled food, migratory cues, and pheromones. Outside the olfactory system, TAAR1 is the most thoroughly studied and has both central and peripheral roles. In the brain, TAAR1 acts as a rheostat of dopaminergic, glutamatergic, and serotonergic neurotransmission and has been identified as a novel therapeutic target for schizophrenia, depression, and addiction. In the periphery, TAAR1 regulates nutrient-induced hormone secretion, suggesting its potential as a novel therapeutic target for diabetes and obesity. TAAR1 may also regulate immune responses by regulating leukocyte differentiation and activation. This article provides a comprehensive review of the current state of knowledge of the evolution, physiologic functions, pharmacology, molecular mechanisms, and therapeutic potential of trace amines and their receptors in vertebrates and invertebrates.

Review and Meta-Analyses of TAAR1 Expression in the Immune System and Cancers

Since its discovery in 2001, the major focus of TAAR1 research has been on its role in monoaminergic regulation, drug-induced reward and psychiatric conditions. More recently, TAAR1 expression and functionality in immune system regulation and immune cell activation has become a topic of emerging interest. Here, we review the immunologically-relevant TAAR1 literature and incorporate open-source expression and cancer survival data meta-analyses. We provide strong evidence for TAAR1 expression in the immune system and cancers revealed through NCBI GEO datamining and discuss its regulation in a spectrum of immune cell types as well as in numerous cancers. We discuss connections and logical directions for further study of TAAR1 in immunological function, and its potential role as a mediator or modulator of immune dysregulation, immunological effects of psychostimulant drugs of abuse, and cancer progression.

TAAR1 induces a disturbed GSK3β phosphorylation in recurrent miscarriages through the ODC

OBJECTIVES

Thyroid hormones play an important role in the maintenance of pregnancy. Their derivates, endogenous amines, act via binding to the trace amine-associated receptor (TAAR1). The aim of our study was to analyse the regulation of TAAR1, serine/threonine kinase (pGSK3β) and ornithine decarboxylase (ODC) in placentas of healthy pregnancies, spontaneous (SM) and recurrent miscarriages (RM) and to investigate the influence of thyroid hormone derivates on TAAR1 expression in trophoblast model cells in vitro.

METHODS

Patients with SM (n = 15) and RM (n = 15) were compared with patients with healthy pregnancies (n = 15) (pregnancy weeks 7-13 each). Immunohistochemistry was applied to analyse placental TAAR1, pGSK3β and ODC expression. Protein expression of the receptors after stimulation with T₃, T₁AM and RO5203548 in BeWo trophoblast model cells was determined via Western blot. Double-immunofluorescence was used to determine placental expression of TAAR1 and ODC.

RESULTS

Levels of TAAR1, pGSK3β and ODC were higher in placentas of RM in comparison to healthy controls. Stimulation of BeWo cells with T₃, T₁AM and RO5203548 significantly increased TAAR1 expression. ODC expression in BeWo cells was upregulated through T₃. Via double-immunofluorescence, TAAR1 and ODC-positive EVT could be detected.

CONCLUSIONS

Upregulation of placental TAAR1 may indicate an increased decarboxylation of thyroid hormones in miscarriages. Patients with RM may have a lack of T₃ through an enhanced transformation of T₃ into T₁AM induced by the ODC. Future investigations could be carried out to analyse what role a prophylactic T₃ substitution plays for patients.