Calcitonin Receptor-Zonula Occludens-1 Interaction Is Critical for Calcitonin-Stimulated Prostate Cancer Metastasis

Zinc finger protein‑like 1 is a novel neuroendocrine biomarker for prostate cancer

Prostate‑derived calcitonin (CT) and its receptor induce tumorigenicity and increase metastatic potential of prostate cancer (PC). CT‑inducible genes in human prostate were identified by subtraction hybridization. Among these genes, zinc finger protein like 1 (ZFPL1) protein was interesting since it was abundantly expressed in malignant prostates but was almost absent in benign prostates. ZFPL1 expression was upregulated by CT and androgens, and ZFPL1 protein was secreted by prostate tumor cells through exosomal secretion. Serum levels of ZFPL1 in cancer patients were at least 4‑fold higher than those in the sera of cancer‑free individuals. Cell biology of ZFPL1 suggests its localization in Golgi bodies and exosomes, and its colocalization with chromogranin A and CD44. These results suggested that ZFPL1 is secreted by tumor cells of neuroendocrine (NE)/stem cell phenotype. The knockdown of endogenous ZFPL1 in (PC) cells led to a remarkable decrease in cell proliferation, and invasion while increasing their apoptosis. As expected, the overexpression of ZFPL1 in prostate cells had an opposite effect on these functions. The knockdown of ZFPL1 in PC cells also decreased Akt phosphorylation, suggesting the actions of ZFPL1 may be mediated through the PI3K‑Akt pathway. Moreover, the present results revealed that ZFPL1 is released by tumors cells of NE or androgen‑independent phenotype and its serum levels are significantly higher in cancer patients, suggesting that it may serve as a blood‑based non‑invasive biomarker of aggressive PC.

MicroRNA-1297 participates in the repair of intestinal barrier injury in patients with HIV/AIDS via negative regulation of PLCβ1

To explore the role of the miRNA-1297/phospholipase Cβ1 (PLCβ1) axis in intestinal barrier injury. Abnormally expressed miR-1297 and its target gene PLCβ1 as well as their transcriptome sequencing were confirmed by bioinformatics analysis. Next, the intestinal barrier injury was induced by lipopolysaccharide (LPS) in the CCCHIE-2 cells. Subsequently, the impacts of miR-1297 and PLCβ1 on the transcriptome were estimated. QRT-PCR and Western blotting were conducted to detect the relative mRNA and protein expressions, respectively. The cell viability and permeability were analyzed by MTT assay and fluorescent yellow detection. miR-1297 was significantly upregulated in patients with human immunodeficiency virus/acquired immunodeficiency syndrome and targeted PLCβ1. Moreover, overexpressed PLCβ1 was mainly enriched in the transforming growth factor-beta signaling pathway, while the knockdown of miR-1297 was focused on the arginine biosynthesis pathway. The overexpression of miR-1297 could reduce the PLCβ1 expression and inhibit the viability of CCCHIE-2 cells injured by LPS, while the effect of the downregulation of miR-1297 was on the opposite. Western blotting and cell fluorescence localization experiments revealed that the inhibition of miR-1297 increased the expressions of PLCβ1 and ZO-1. In addition, the upregulation of miR-1297 strengthened the permeability in cells injured by LPS, as did the knockdown of PLCβ1. miR-1297 could restrain the repair of intestinal barrier injury via negatively regulating PLCβ1 and its tight junction downstream protein ZO-1 in CCC-HIE-2 cells injured by LPS, which indicated that PLCβ1 and miR-1297 might be important targets for the repair of intestinal barrier injury.

New Frontiers in Molecular Imaging Using Peptide-Based Radiopharmaceuticals for Prostate Cancer

The high incidence of prostate cancer (PCa) increases the need for progress in its diagnosis, staging, and precise treatment. The overexpression of tumor-specific receptors for peptides in human cancer cells, such as gastrin-releasing peptide receptor, natriuretic peptide receptor, and somatostatin receptor, has indicated the ideal molecular basis for targeted imaging and therapy. Targeting these receptors using radiolabeled peptides and analogs have been an essential topic on the current forefront of PCa studies. Radiolabeled peptides have been used to target receptors for molecular imaging in human PCa with high affinity and specificity. The radiolabeled peptides enable optimal quick elimination from blood and normal tissues, producing high contrast for positron emission computed tomography and single-photon emission computed tomography imaging with high tumor-to-normal tissue uptake ratios. Owing to their successful application in visualization, peptide derivatives with therapeutic radionuclides for peptide receptor radionuclide therapy in PCa have been explored in recent years. These developments offer the promise of personalized, molecular medicine for individual patients. Hence, we review the preclinical and clinical literature in the past 20 years and focus on the newer developments of peptide-based radiopharmaceuticals for the imaging and therapy of PCa.

Relationship between apical junction proteins, gene expression and cancer

The apical junctional complex (AJC) is a cell-cell adhesion system present at the upper portion of the lateral membrane of epithelial cells integrated by the tight junction (TJ) and the adherens junction (AJ). This complex is crucial to initiate and stabilize cell-cell adhesion, to regulate the paracellular transit of ions and molecules and to maintain cell polarity. Moreover, we now consider the AJC as a hub of signal transduction that regulates cell-cell adhesion, gene transcription and cell proliferation and differentiation. The molecular components of the AJC are multiple and diverse and depending on the cellular context some of the proteins in this complex act as tumor suppressors or as promoters of cell transformation, migration and metastasis outgrowth. Here, we describe these new roles played by TJ and AJ proteins and their potential use in cancer diagnostics and as targets for therapeutic intervention.

Calcitonin receptor is required for T-antigen-induced prostate carcinogenesis

Expression of calcitonin (CT) and its receptor (CTR) is frequently elevated in prostate cancer (PC) and activation of CT–CTR axis in non- invasive PC cells induces an invasive phenotype. However, the role of CT-CTR axis in prostate carcinogenesis has not been investigated. We employed a transgenic mouse prostate cancer model that uses long probasin promoter to target the expression of T-antigen in the prostate gland (LPB-Tag) along with CTR knock-out mice (CTRKO) to address this question. We cross-bred LPB-Tag mice with CTRKO to obtain four groups of mice. Prostates of these mice were obtained at the age of 90 days, fixed, paraffin-embedded, and used either for the extraction of RNA or for immunofluorescence. Prostate RNAs from different groups were reverse transcribed and used either for transcription profiling or for qRT-PCR. As expected, prostates of mice with LPB-Tag genotype displayed well-grown tumors with histologic features such as loss of normal morphology and nuclear atypia. WT as well as CTRKO mice displayed normal prostate morphology. Interestingly, LPB-Tag-CTRKO prostates also displayed relatively normal morphology which was indistinguishable from the WT. Microarray analysis as well as qRT-PCR suggested that CTRKO genotype reversed T-antigen-induced silencing of RB and PTEN gene expression as well as T-antigen-induced expression of several enzymes associated with lipid metabolism/ cholesterol biosynthesis, several cancer-related and androgen-regulated genes. The results for the first time identify mechanisms associated CTR-induced prostate carcinogenesis, and raise an exciting possibility of using a potent CT antagonist to attenuate progression of prostate cancer.

Expression and activity of the calcitonin receptor family in a sample of primary human high-grade gliomas

Background

Glioblastoma (GBM) is the most common and aggressive type of primary brain cancer. With median survival of less than 15 months, identification and validation of new GBM therapeutic targets is of critical importance.

Results

In this study we tested expression and performed pharmacological characterization of the calcitonin receptor (CTR) as well as other members of the calcitonin family of receptors in high-grade glioma (HGG) cell lines derived from individual patient tumours, cultured in defined conditions.

Previous immunohistochemical data demonstrated CTR expression in GBM biopsies and we were able to confirm CALCR (gene encoding CTR) expression. However, as assessed by cAMP accumulation assay, only one of the studied cell lines expressed functional CTR, while the other cell lines have functional CGRP (CLR/RAMP1) receptors. The only CTR-expressing cell line (SB2b) showed modest coupling to the cAMP pathway and no activation of other known CTR signaling pathways, including ERK_1/2 and p38 MAP kinases, and Ca²⁺ mobilization, supportive of low cell surface receptor expression.

Exome sequencing data failed to account for the discrepancy between functional data and expression on the cell lines that do not respond to calcitonin(s) with no deleterious non-synonymous polymorphisms detected, suggesting that other factors may be at play, such as alternative splicing or rapid constitutive receptor internalisation.

Conclusions

This study shows that GPCR signaling can display significant variation depending on cellular system used, and effects seen in model recombinant cell lines or tumour cell lines are not always reproduced in a more physiologically relevant system and vice versa.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5369-y) contains supplementary material, which is available to authorized users.

Relationship between G proteins coupled receptors and tight junctions

Tight junctions (TJs) are sites of cell-cell adhesion, constituted by a cytoplasmic plaque of molecules linked to integral proteins that form a network of strands around epithelial and endothelial cells at the uppermost portion of the lateral membrane. TJs maintain plasma membrane polarity and form channels and barriers that regulate the transit of ions and molecules through the paracellular pathway. This structure that regulates traffic between the external milieu and the organism is affected in numerous pathological conditions and constitutes an important target for therapeutic intervention. Here, we describe how a wide array of G protein-coupled receptors that are activated by diverse stimuli including light, ions, hormones, peptides, lipids, nucleotides and proteases, signal through heterotrimeric G proteins, arrestins and kinases to regulate TJs present in the blood-brain barrier, the blood-retinal barrier, renal tubular cells, keratinocytes, lung and colon, and the slit diaphragm of the glomerulus.

Characterization of signalling and regulation of common calcitonin receptor splice variants and polymorphisms

The calcitonin receptor (CTR) is a class B G protein-coupled receptor that is a therapeutic target for the treatment of hypercalcaemia of malignancy, Paget's disease and osteoporosis. In primates, the CTR is subject to alternative splicing, with a unique, primate-specific splice variant being preferentially expressed in reproductive organs, lung and kidney. In addition, humans possess a common non-synonymous single-nucleotide polymorphism (SNP) encoding a proline/leucine substitution in the C-terminal tail. In low power studies, the leucine polymorphism has been associated with increased risk of osteoporosis in East Asian populations and, independently, with increased risk of kidney stone disease in a central Asian population. The CTR is pleiotropically coupled, though the relative physiological importance of these pathways is poorly understood. Using both COS-7 and HEK293 cells recombinantly expressing human CTR, we have characterized both splice variant and polymorphism dependent response to CTs from several species in key signalling pathways and competition binding assays. These data indicate that the naturally occurring changes to the intracellular face of CTR alter ligand affinity and signalling, in a pathway and agonist dependent manner. These results further support the potential for these primate-specific CTR variants to engender different physiological responses. In addition, we report that the CTR exhibits constitutive internalization, independent of splice variant and polymorphism and this profile is unaltered by peptide binding.

The Role of the Calcitonin Peptide Family in Prostate Cancer and Bone Metastasis

PURPOSE OF REVIEW

This study is to highlight recent discoveries associated with the role of calcitonin peptide family and their receptors in prostate cancer progression and bone metastasis.

RECENT FINDINGS

Studies have linked adrenomedullin (AM), calcitonin (CT) and calcitonin gene-related peptide (CGRP) to the spread of prostate tumours to the bone. AM can induce a metastatic phenotype in prostate cancer cells through its action on TRPV2 calcium channels and is also capable of influencing localised levels of RANKL in the bone to favour tumourigenesis. CT utilises A-kinase anchoring proteins to indirectly act on PKA and promote metastasis in prostate cancer. The receptor for CT contains a PDZ-binding domain, the deletion of which stops metastasis to the bone in orthotopic prostate models.

SUMMARY

Recent findings show strong evidence for the role of calcitonin peptides and receptors in prostate cancer and bone metastasis. Further research could provide potential prognostic markers and therapeutic targets for prostate cancer patients.

Connexins, important players in the dissemination of prostate cancer cells

Over the past 50years, increasing experimental evidences have established that connexins (Cxs) and gap junctional intercellular communication (GJIC) ensure an important role in both the onset and development of cancerous processes. In the present review, we focus on the impact of Cxs and GJIC during the development of prostate cancer (PCa), from the primary growth mainly localized in acinar glands and ducts to the distant metastasis mainly concentrated in bone. As observed in several other types of solid tumours, Cxs and especially Cx43 exhibit an ambivalent role with a tumour suppressor effect in the early stages and, conversely, a rather pro-tumoural profile for most of invasion and dissemination steps to secondary sites. We report here the current knowledge on the function of Cxs during PCa cells migration, cytoskeletal dynamics, proteinases activities and the cross talk with the surrounding stromal cells in the microenvironment of the tumour and the bones. In addition, we discuss the role of Cxs in the bone tropism even if the prostate model is rarely used to study the complete sequence of cancer dissemination compared to breast cancer or melanoma. Even if not yet fully understood, these recent findings on Cxs provide new insights into their molecular mechanisms associated with progression and bone targeted behaviour of PCa. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve.

Calcitonin receptor increases invasion of prostate cancer cells by recruiting zonula occludens-1 and promoting PKA-mediated TJ disassembly

Almost all primary prostate cancers (PCs) and PC cell lines express calcitonin (CT) and/or its receptor (CTR), and their co-expression positively correlates with their invasiveness. Activation of the CT-CTR axis in non-invasive LNCaP cells induces an invasive phenotype. In contrast, silencing of CT/CTR expression in highly metastatic PC-3M cells markedly reduces their tumorigenicity and abolishes their ability to form distant metastases in nude mice. Our recent studies suggest that CTR interacts with zonula occludens 1 (ZO-1) through PDZ interaction to destabilize tight junctions and increase invasion of PC cells. Our results show that CTR activates AKAP2-anchored cAMP-dependent protein kinase A, which then phosphorylates tight junction proteins ZO-1 and claudin 3. Moreover, PKA-mediated phosphorylation of tight unction proteins required CTR-ZO-1 interaction, suggesting that the interaction may bring CTR-activated PKA in close proximity of tight junction proteins. Furthermore, inhibition of PKA activity attenuated CT-induced loss of TJ functionality and invasion, suggesting that the phosphorylation of TJ proteins is responsible for TJ disassembly. Finally, we show that the prevention of CTR-ZO-1 interaction abolishes CT-induced invasion, and can serve as a novel therapeutic tool to treat aggressive prostate cancers. In brief, the present study identifies the significance of CTR-ZO-1 interaction in progression of prostate cancer to its metastatic form.