Cariprazine, A Dopamine D₂/D₃ Receptor Partial Agonist, Modulates ABCG2-Mediated Multidrug Resistance in Cancer

Research progress on the roles of dopamine and dopamine receptors in digestive system diseases

Dopamine (DA) is a neurotransmitter synthesized in the human body that acts on multiple organs throughout the body, reaching them through the blood circulation. Neurotransmitters are special molecules that act as messengers by binding to receptors at chemical synapses between neurons. As ligands, they mainly bind to corresponding receptors on central or peripheral tissue cells. Signalling through chemical synapses is involved in regulating the activities of various body systems. Lack of DA or a decrease in DA levels in the brain can lead to serious diseases such as Parkinson's disease, schizophrenia, addiction and attention deficit disorder. It is widely recognized that DA is closely related to neurological diseases. As research on the roles of brain-gut peptides in human physiology and pathology has deepened in recent years, the regulatory role of neurotransmitters in digestive system diseases has gradually attracted researchers' attention, and research on DA has expanded to the field of digestive system diseases. This review mainly elaborates on the research progress on the roles of DA and DRs related to digestive system diseases. Starting from the biochemical and pharmacological properties of DA and DRs, it discusses the therapeutic value of DA- and DR-related drugs for digestive system diseases.

Understanding the Role of Dopamine in Cancer: Past, Present, and Future

Dopamine (DA, 3-hydroxytyramine) is member of the catecholamine family and is classically characterized according to its role in the central nervous system as a neurotransmitter. In recent decades, many novel and intriguing discoveries have been made about the peripheral expression of DA receptors (DRs) and the role of DA signaling in both normal and pathological processes. Drawing from decades of evidence suggesting a link between DA and cancer, the DA pathway (DAP) has recently emerged as a potential target in antitumor therapies. Due to the onerous, expensive, and frequently unsuccessful nature of drug development, the repurposing of dopaminergic drugs for cancer therapy has the potential to greatly benefit patients and drug developers alike. However, the lack of clear mechanistic data supporting the direct involvement of DRs and their downstream signaling components in cancer represents an ongoing challenge that has limited the translation of these drugs to the clinic. Despite this, the breadth of evidence linking DA to cancer and non-tumor cells in the tumor microenvironment (TME) justifies further inquiry into the potential applications of this treatment modality in cancer. Herein, we review the literature characterizing the interplay between the DA signaling axis and cancer, highlighting key findings, and then propose rational lines of investigation to follow.

Newer antipsychotics: Brexpiprazole, cariprazine, and lumateperone: A pledge or another unkept promise?

Antipsychotic agents are used for various indications in the treatment of psychiatric disorders. Despite their proven roles in multiple conditions, the treatment-emergent side effects of antipsychotic medications, such as metabolic side effects, are often the limiting factor for their long-term and short-term uses. Moreover, antipsychotic medications are often criticized for being less effective in treating different disabling symptoms such as negative symptoms of schizophrenia. As a result, the search for safer and more efficacious antipsychotic agents is ongoing. Newer antipsychotic agents are gaining attention related to emerging efficacy and tolerability data in treating neuropsychiatric conditions. In this review, we attempt to appraise the scientific data on psychopharmacology, safety profile, and efficacy of the newer additions to the list of second-generation antipsychotics, namely brexpiprazole, cariprazine, and lumateperone. We conducted a selective review utilizing PubMed, clinicaltrials.gov, and Cochrane databases to gather appropriate publications, keeping broad inclusion criteria. There were no restrictions on the age of the study population or the year of publication. We also cross-referenced articles and references to capture all existing studies. Our review of the current literature indicates that all three antipsychotic agents appear to be promising based on their short-term studies, while long-term studies remain limited. There is also a need for a head to head comparison between the newer antipsychotics with the other antipsychotic agents to ascertain if the newer agents are any better than the others.

Repurposing Antipsychotics for Cancer Treatment

Cancer is a leading cause of death worldwide, with approximately 19 million new cases each year. Lately, several novel chemotherapeutic drugs have been introduced, efficiently inhibiting tumor growth and proliferation. However, developing a new drug is a time- and money-consuming process, requiring around 1 billion dollars and nearly ten years, with only a minority of the initially effective anti-cancer drugs experimentally finally being efficient in human clinical trials. Drug repurposing for cancer treatment is an optimal alternative as the safety of these drugs has been previously tested, and thus, in case of successful preclinical studies, can be introduced faster and with a lower cost into phase 3 clinical trials. Antipsychotic drugs are associated with anti-cancer properties and, lately, there has been an increasing interest in their role in cancer treatment. In the present review, we discussed in detail the in-vitro and in-vivo properties of the most common typical and atypical antipsychotics, along with their mechanism of action.

Computational approaches in cancer multidrug resistance research: Identification of potential biomarkers, drug targets and drug-target interactions

Like physics in the 19th century, biology and molecular biology in particular, has been fertilized and enhanced like few other scientific fields, by the incorporation of mathematical methods. In the last decades, a whole new scientific field, bioinformatics, has developed with an output of over 30,000 papers a year (Pubmed search using the keyword "bioinformatics"). Huge databases of mass throughput data have been established, with ArrayExpress alone containing more than 2.7 million assays (October 2019). Computational methods have become indispensable tools in molecular biology, particularly in one of the most challenging areas of cancer research, multidrug resistance (MDR). However, confronted with a plethora of different algorithms, approaches, and methods, the average researcher faces key questions: Which methods do exist? Which methods can be used to tackle the aims of a given study? Or, more generally, how do I use computational biology/bioinformatics to bolster my research? The current review is aimed at providing guidance to existing methods with relevance to MDR research. In particular, we provide an overview on: a) the identification of potential biomarkers using expression data; b) the prediction of treatment response by machine learning methods; c) the employment of network approaches to identify gene/protein regulatory networks and potential key players; d) the identification of drug-target interactions; e) the use of bipartite networks to identify multidrug targets; f) the identification of cellular subpopulations with the MDR phenotype; and, finally, g) the use of molecular modeling methods to guide and enhance drug discovery. This review shall serve as a guide through some of the basic concepts useful in MDR research. It shall give the reader some ideas about the possibilities in MDR research by using computational tools, and, finally, it shall provide a short overview of relevant literature.

Novel 3-((2-chloroquinolin-3-yl)methylene)indolin-2-one derivatives produce anticancer efficacy in ovarian cancer in vitro

A novel series of 3-((2-chloroquinolin-3-yl)methylene)indolin-2-ones were synthesized, using the ‘molecular hybridization approach’ and evaluated for anticancer efficacy. Eleven 3-((2-chloroquinolin-3-yl)methylene)indolin-2-ones (LM01 to LM11) were synthesized and evaluated for in vitro cytotoxic efficacy in cancer (ovarian, prostate and colon) and two non-cancerous cell lines. Among the 3-((2-chloroquinolin-3-yl)methylene)indolin-2-one derivatives, LM08, with a 6-Cl substitution in the 3-quinolinyl moiety, had selective and potent cytotoxic efficacy in the ovarian cancer cell line A2780. Further mechanistic investigations indicated that LM08 significantly inhibited the clonogenic survival of A2780 cancer cells, which was mediated by inducing apoptosis.

Cancer and the Dopamine D2 Receptor: A Pharmacological Perspective

The dopamine D₂ receptor (D₂R) family is upregulated in many cancers and tied to stemness. Reduced cancer risk has been correlated with disorders such as schizophrenia and Parkinson's disease, in which dopaminergic drugs are used. D₂R antagonists are reported to have anticancer efficacy in cell culture and animal models where they have reduced tumor growth, induced autophagy, affected lipid metabolism, and caused apoptosis, among other effects. This has led to several hypotheses, the most prevalent being that D₂R ligands may be a novel approach to cancer chemotherapy. This hypothesis is appealing because of the large number of approved and experimental drugs of this class that could be repurposed. We review the current state of the literature and the evidence for and against this hypothesis. When the existing literature is evaluated from a pharmacological context, one of the striking findings is that the concentrations needed for cytotoxic effects of D₂R antagonists are orders of magnitude higher than their affinity for this receptor. Although additional definitive studies will provide further clarity, our hypothesis is that targeting D₂-like dopamine receptors may only yield useful ligands for cancer chemotherapy in rare cases.