Dopamine receptors in a human colonic cancer cell line (HT29). Some receptor-related biological effects of dopamine

Antipsychotic dopamine receptor antagonists, cancer, and cancer stem cells

Cancer is one of the deadliest diseases in the world. Despite extensive studies, treating metastatic cancers remains challenging. Years of research have linked a rare set of cells known as cancer stem cells (CSCs) to drug resistance, leading to the suggestion that eradication of CSCs might be an effective therapeutic strategy. However, few drug candidates are active against CSCs. New drug discovery is often a lengthy process. Drug screening has been advantageous in identifying drug candidates. Current understanding of cancer biology has revealed various clues to target cancer from different points of view. Many studies have found dopamine receptors (DRs) in various cancers. Therefore, DR antagonists have attracted a lot of attention in cancer research. Recently, a group of antipsychotic DR antagonists has been demonstrated to possess remarkable abilities to restrain and sensitize CSCs to existing chemotherapeutics by a process called differentiation approach. In this review, we will describe current aspects of CSC-targeting therapeutics, antipsychotic DR antagonists, and their extraordinary abilities to fight cancer.

Dopamine functionalized polymeric nanoparticle for targeted drug delivery

A dopamine functionalized, polyaspartamide-based polymeric nanoparticle has been synthesized for selective delivery of drugs to human colon adenocarcinoma cells.

DRD2/DARPP-32 expression correlates with lymph node metastasis and tumor progression in patients with esophageal squamous cell carcinoma

BACKGROUND

Dopamine receptors (DRs) are members of seven transmembrane domain trimeric guanosine 5'-triphosphate (GTP)-binding protein-coupled receptor family. Through dopamine receptor activation, dopamine plays a significant role in regulating gene expression, such as induced tumor cell migration.

MATERIALS AND METHODS

We investigated DRD1 and DRD2 expressions in patients with esophageal squamous cell carcinoma (ESCC) for immunohistochemistry and analyzed differences between DRD1, DRD2, and DARPP-32 expressions of clinicopathological features in 122 patients with ESCC.

RESULTS

DRD1 immunostaining correlated with the pathologic grade (P = 0.0127), and DRD2 immunostaining correlated with the pathologic stage (P = 0.0432) and pN classification (P = 0.0112). A significant correlation was found between DRD1 and DRD2 expression (P = 0.0292). However, no correlation was observed between DRD1/DRD2 expression and DARPP-32 expression (P = 0.4555 and 0.4774, respectively). No correlation was observed between the DRD1/DRD2 expression and patient prognosis. To find the cooperative role between DRD1, DRD2, and DARPP-32 expressions, patients were classified into the different groups. In the DRD2/DARPP-32 combination, the (+/-) group was significantly correlated with pathologic stage (P = 0.0006), lymph node metastasis (P = 0.0001), pT (P = 0.0287), and tumor size (P = 0.0202). Moreover, patients with this combination showed a lower survival rate compared with the other three groups (P = 0.0287).

CONCLUSIONS

We conclude that DRD2/DARPP-32 expression is associated with tumor progression and that DRD2/DARPP-32 expressions may help predict prognosis in patients with ESCC.

Enhancement of dopaminergic agonist bromocriptine of gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine in Wistar rats

The effects of the dopamine agonist 2-bromo-alpha-ergocryptine methanesulfonate (bromocriptine) on the incidence, number and histology of gastric cancer induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in Wistar rats. Rats were given 1 or 2 mg kg-1 body weight of bromocriptine subcutaneously every other day in depot form after 25 weeks of oral treatment with MNNG. Prolonged administration of bromocriptine at both dosages every other day resulted in a significant increase in the incidence and number of gastric cancers of the glandular stomach by week 52. Bromocriptine treatment did not influence the histological type of gastric cancer, but caused a significant increase in the labelling index of epithelial cells of the antrum. These findings indicate that the dopamine agonist bromocriptine promotes gastric carcinogenesis, and that this effect may be related to its effect in increasing proliferation of epithelial cells in the antral mucosa.

Identification and characterization of D1 and D2 dopamine receptors in cultured neuroblastoma and retinoblastoma clonal cell lines

The recent availability of high specific activity radiolabeled dopaminergic antagonists with specificity for dopamine receptor subtypes has allowed us to screen a wide variety of cultured mammalian cell lines for the presence of D1 and D2 dopamine receptors. Specific receptor binding of the D1 selective antagonists [3H]SCH 23390 and [125I]SCH 23982 was detected in membranes prepared from NS20Y cells, a clonal cell line derived from the C1300 murine neuroblastoma. Saturation analysis of [3H]SCH 23390 binding revealed the presence of saturable, high affinity binding sites with a dissociation constant (Kd) of 575 pM and a receptor density of 138 fmol/mg protein (approximately 9000 receptors/cell). Inhibition of [3H]SCH 23390 binding by a series of dopaminergic agonists and antagonists exhibited appropriate stereoselectivity and pharmacological specificity, verifying the D1 nature of this site. Dopamine inhibition of [3H]SCH 23390 binding revealed the presence of high and low affinity agonist binding sites which were converted to a homogeneous low affinity state by the addition of GppNHp. In membranes prepared from the WERI 27 human retinoblastoma cell line, specific receptor binding of the D2 antagonists [3H]methylspiperone and [125I]NAPS was observed. Saturation analysis of [3H]methylspiperone binding revealed the presence of a single class of high affinity, saturable binding sites with a Kd of 140 pM and a Bmax of 223 fmol/mg protein (approximately 2500 receptor sites/cell). Inhibition of [3H]methylspiperone binding by dopaminergic antagonists exhibited a rank order of potency consistent with the identification of a D2 dopamine receptor subtype. In addition, dopamine inhibition of [3H]methylspiperone binding exhibited both high and low affinity agonist binding sites which were converted to low affinity by the addition of GppNHp. These results represent the first direct demonstration of D1 and D2 dopamine receptors in cultured mammalian clonal cell lines. These cells should provide powerful model systems for investigating the molecular mechanisms involved in dopamine receptor/effector coupling and regulation.

Expression of membrane receptors and (proto)oncogenes during the ontogenic development and neoplastic transformation of the intestinal mucosa

The functional relationship between membrane receptors involved in signal transduction and (proto) oncogene expression has been explored during the ontogenic development and differentiation of the intestinal mucosa in man and rat. The present review develops detailed picture of the current understanding of some mechanisms underlying growth and function of normal, immortalized and cancerous intestinal epithelial cells.

Dopamine receptors in pancreatic acinar cells from dog

Dispersed acini from dog pancreas were used to characterize dopamine receptors in a study on the stimulation of cellular cyclic AMP formation and the binding of [3H]dopamine. Dopamine elicited concentration-dependent stimulation of cellular cyclic AMP with a maximal increase occurring at a concentration of 0.1 mM (EC50 = 1 microM). Epinine produced a potent stimulation similar to that by dopamine; the alpha-adrenoceptor agonists (amidephrine and noradrenaline) were less potent. Isoproterenol and apomorphine were ineffective. The effect of dopamine was potently blocked by dopamine receptor antagonists such as cis-(Z)-flupenthixol, haloperidol, fluphenazine, whereas spiperone, sulpiride and domperidone were weakly active. Apomorphine acted as an antagonist to inhibit dopamine-stimulated cellular cyclic AMP formation as well as phenoxybenzamine. Yohimbine, prazosin or clonidine were poorly or not active. The affinity of agents to stimulate cellular cyclic AMP formation or to inhibit dopamine-stimulated cellular cyclic AMP formation was closely related to their affinity to inhibit the binding of [3H]dopamine to pancreatic acini, providing evidence that dopamine binding sites are receptors that mediate the action of dopamine on cAMP accumulation. This was further substantiated by the demonstration of specific binding sites for [3H]cis-(Z)-flupenthixol.