Generation of MCF-7 cells with aggressive metastatic potential in vitro and in vivo.

Epithelial-mesenchymal transition (EMT) is a cellular development program characterized by loss of cell adhesion and increased cell mobility. It is essential for numerous processes including metastasis. In this study we have generated "aggressive" MCF-7 breast cancer cells (MCF-7-EMT), which show significantly increased invasion in contrast to wild type MCF-7 (MCF-7 WT) cells. In addition, we have analyzed, whether these cell lines differ in their metastatic behavior in vivo and in expression of invasion and/or EMT-relevant genes. Invasive behavior of different human breast cancer cell lines was tested. "Aggressive" MCF-7 cells (MCF-7-EMT) were generated using coculture and mammosphere culture techniques. To analyze whether or not MCF-7-EMT cells in contrast to MCF-7 WT cells form metastases in vivo, we assessed metastases in a nude mouse model. mRNA expression profiles of MCF-7 WT cells and MCF-7-EMT cells were compared using the Affymetrix micro array technique. Expression of selected genes was validated using real-time PCR. In addition, protein expression of epithelial marker E-cadherin (CDH1) and mesenchymal markers N-cadherin (CDH2), Vimentin (VIM), and TWIST was compared. The breast cancer cell lines showed different invasive behavior from hardly any invasion to a stronger cell movement. Coculture with osteoblast-like MG63 cells led to significantly increased cell invasion rates. The highest increase was shown using MCF-7 WT cells. Generated MCF-7-EMT cells showed significantly increased invasion as compared to MCF-7 WT cells. In 8 of 10 mice bearing orthotopically growing MCF-7-EMT tumors, we could detect metastases in liver and lung. In mice bearing MCF-7 WT tumors (n = 10), no metastases were found. MCF-7 WT cells and MCF-7-EMT cells were different in expression of 325 genes. Forty-four of the most regulated 50 invasion and/or EMT-related genes were upregulated and 6 genes were downregulated in MCF-7-EMT cells. Protein expression of mesenchymal markers CDH2, VIM, and TWIST was clearly increased in MCF-7-EMT cells. Protein expression of epithelial marker CDH1 was clearly decreased. With the breast cancer cell lines, MCF-7-EMT and MCF-7 WT cells, we have an excellent model of cells for further studies of EMT and invasion in vitro and in vivo.

Kisspeptin-10 inhibits stromal-derived factor 1-induced invasion of human endometrial cancer cells.

OBJECTIVES: The cross talk between metastatic cancer cells and target sites is critical for the development and progression of metastases. Disruption of this interaction will allow to design mechanism-based effective and specific therapeutic interventions for metastases. We have established a coculture system of cells derived from different tumor entities and MG63 human osteoblastlike cells to analyze tumor cell invasion. Recently, we have shown that breast cancer cell invasion was dramatically increased when cocultured with MG63 cells.Using this model, we have now analyzed whether stromal-derived factor 1 (SDF-1) is responsible for human endometrial cancer cell invasion and whether kisspeptin-10 (KP-10) treatment affects SDF-1-induced invasion of endometrial cancer cells in vitro. METHODS: Invasion was quantified by assessment of endometrial cancer cell migration rate through an artificial basement membrane in a modified Boyden chamber during coculture with MG63 cells or after treatment with SDF-1α, SDF-1ß, or the combination of both SDF-1 isoforms. In addition, the role of SDF-1 in invasion of endometrial cancer cells was analyzed by blocking SDF-1 secretion during coculture with MG64 cells. Furthermore, the effects of KP-10 treatment on MG63 coculture-driven and SDF-1-induced invasion were analyzed. RESULTS: Endometrial cancer cell invasion was significantly increased when cocultured with MG63 cells. Treatment with KP-10 reduced the ability to invade a reconstituted basement membrane and to migrate in response to the cellular stimulus. This effect was significant in a dose window of 10(-13) to 10(-11) mol/L. During coculture, SDF-1 protein expression of MG63 cells was significantly increased. The MG63 coculture-induced increase of endometrial cancer cell invasion could be blocked by anti-SDF-1 antibodies. Treatment of endometrial cancer cells in monoculture (without MG63) with SDF-1α, SDF-1ß, or the combination of both isoforms resulted in a significant increase of endometrial cancer cell invasion. The SDF-1-induced increase of endometrial cancer cell invasion was significantly reduced after treatment with KP-10. CONCLUSIONS: Our findings suggest that SDF-1 plays a major role in endometrial cancer invasion. Stromal-derived factor 1-induced invasion can be inhibited by KP-10 treatment.

Antiproliferative effects of kisspeptin­10 depend on artificial GPR54 (KISS1R) expression levels.

Kisspeptins are peptides derived from the metastasis suppressor gene KISS1 interacting with GPR54 as their corresponding receptor. The KISS1/GPR54 system is one regulator of cellular motility mechanisms leading to decreased migration and invasion. Its role in cell proliferation processes is not clearly understood. In this study, breast cancer cell lines, T47D, ZR75-1, MDA­MB­231, MDA­MB­435s, MDA­MB­453, HCC 70, HCC 1806, HCC 1937 and MCF­7, were investigated for their endogenous GPR54 expression by immunocytochemistry, RT­PCR and western blot analysis. The effect of kisspeptin­10 on proliferation was measured in MDA­MB­231, MDA­MB­435s, HCC 1806 and MCF­7 cells. Further experiments on proliferation were carried out with cells transfected with GPR54. All of the tested breast cancer cell lines expressed GPR54 in different amounts. No effects on proliferation were detected in the breast cancer cells expressing the receptor endogenously. In transfected neuronal cells overexpressing GPR54, proliferation was significantly inhibited by kisspeptin­10. The results indicate that the antiproliferative action of kisspeptin depends on the nature of GPR54 expression. The effect was detected in an artificial system of cells transfected with GPR54 and not in cells expressing the receptor endogenously. Thus, the antiproliferative action of kisspeptin seems not to be important for pathophysiological processes.

Kisspeptin-10 inhibits bone-directed migration of GPR54-positive breast cancer cells: Evidence for a dose-window effect.

OBJECTIVES: The KiSS-1 gene product is absent or expressed at low level in metastatic breast cancer compared with their nonmetastatic counterparts. A deca-peptide derived from the KiSS-1 gene product, designated kisspeptin-10 (Kp-10), activates a receptor coupled to Gαq subunits (GPR54 or KiSS-1R). In this study we have analyzed whether Kp-10 treatment affects bone-directed migration of GPR54-positive breast cancer cells. METHODS: GPR54 expression was analyzed using immune cytochemistry. Bone-directed breast cancer cell invasion was measured by assessment of the breast cancer cell migration rate through an artificial basement membrane. Chemokine receptor CXCR4 and stromal cell-derived factor-1 (SDF-1) mRNA expression was quantified using semi-quantitative RT-PCR. CXCR4 protein expression and SDF-1 protein secretion were measured using the western blot technique. RESULTS: Breast cancer cell invasion was increased when cocultured with MG63 osteoblast-like cells. Treatment with KP-10 reduced the ability to invade a reconstituted basement membrane and to migrate in response to the cellular stimulus. This effect was significant in a dose-window of 10⁻9 M to 10⁻¹¹ M. Searching for the molecular mechanisms we found that KP-10 treatment significantly reduces expression of the chemokine receptor CXCR4 by the breast cancer cells. In addition, expression and secretion of its ligand SDF-1 by the MG63 cells were significantly reduced. Furthermore, SDF-1-induced CXCR4 signaling was down-regulated. CONCLUSIONS: These data represent the first report that KP-10 inhibits bone-directed migration of GPR54-positive breast cancer cells. In addition, we found evidence for a KP-10 dose-window effect. Furthermore, the SDF-1/CXCR4 system seems to be involved in the anti-migratory action of KP-10.

Interaction of androsterone and progesterone with inhibitory ligand-gated ion channels: a patch clamp study.

Gamma-aminobutyric acid receptor type A (GABA(A)) receptor channels mediate fast inhibitory neurotransmission throughout the central nervous system while the expression of ionotropic glycine receptors is mainly restricted to the spinal cord and brain stem. Neuroactive steroids are well known as positive allosteric modulators of GABA(A) receptor function. Furthermore, there have been hints for an interaction of neuroactive steroids with ionotropic glycine receptors. The aim of the study was to characterize the effect of androsterone and progesterone on alpha(1) and alpha(1)beta glycine receptor and alpha(1)beta(2)gamma(2) GABA(A) receptor channels and to examine the molecular interactions between ligands and receptors. Electrophysiological recordings were performed on HEK 293 cells using the patch clamp technique in combination with an ultrafast perfusion system. A direct activation of inhibitory ionotropic receptors was observed for androsterone at GABA(A) receptor channels. A coactivation of currents elicited by nonsaturating agonist concentrations was observed with androsterone and progesterone at glycine and GABA(A) receptor channels. We could show that association of beta subunits with alpha subunits affects the sensitivity of glycine receptors to androsterone. In contrast to previous reports in which recombinant glycine receptors were inhibited by progesterone, a potentiating effect was revealed by our experiments. At concentrations of 0.1 mM and higher, there were also hints to a channel block-like mechanism. In conclusion, different molecular mechanisms of interaction between neuroactive steroids and GABA as well as glycine receptors could be identified and quantitatively described. Our data clarify the role of steroid compounds in the modulation of inhibitory receptor channel function.

Molecular analysis of the A322D mutation in the GABA receptor alpha-subunit causing juvenile myoclonic epilepsy.

Juvenile myoclonic epilepsy (JME) belongs to the most common forms of hereditary epilepsy, the idiopathic generalized epilepsies. Although the mode of inheritance is usually complex, mutations in single genes have been shown to cause the disease in some families with autosomal dominant inheritance. The first mutation in a multigeneration JME family has been recently found in the alpha1-subunit of the GABAA receptor (GABRA1), predicting the single amino acid substitution A322D. We further characterized the functional consequences of this mutation by coexpressing alpha1-, beta2- and gamma2-subunits in human embryonic kidney (HEK293) cells. By using an ultrafast application system, mutant receptors have shown reduced macroscopic current amplitudes at saturating GABA concentrations and a highly reduced affinity to GABA compared to the wild-type (WT). Dose-response curves for current amplitudes, activation kinetics, and GABA-dependent desensitization parameters showed a parallel shift towards 30- to 40-fold higher GABA concentrations. Both deactivation and resensitization kinetics were considerably accelerated in mutant channels. In addition, mutant receptors labelled with enhanced green fluorescent protein (EGFP) were not integrated in the cell membrane, in contrast to WT receptors. Therefore, the A322D mutation leads to a severe loss-of-function of the human GABAA receptor by several mechanisms, including reduced surface expression, reduced GABA-sensitivity, and accelerated deactivation. These molecular defects could decrease and shorten the resulting inhibitory postsynaptic currents (IPSCs) in vivo, which can induce a hyperexcitability of the postsynaptic membrane and explain the occurrence of epileptic seizures.

Militarinone A induces differentiation in PC12 cells via MAP and Akt kinase signal transduction pathways.

The fungal metabolite militarinone A (MILI A) promotes neurite outgrowth in PC12 cells. This study was conducted to investigate the signaling pathways involved in the cellular differentiation processes induced by the compound, with a focus on cascades implicated with nerve growth factor (NGF)-mediated neuritogenesis. MILI A possessed pronounced amphiphilic properties. The compound rapidly accumulated in the cell membrane and was slowly released into the cytoplasma. In primed PC12 cells, an early activation of protein kinase B (Akt), representing a downstream target of phosphoinositol 3 (PI3) kinase, and a delayed phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2), and of transcription factor cAMP responsive element binding protein (CREB) was found. The NGF-dependent activation of c-Jun amino terminal kinase (SAPK/JNK1) was potentiated. Morphological differentiation of cells and the phosphorylation of specific signal molecules were blocked by the MAP kinase (MEK1) inhibitor PD098059, the PI3-kinase (PI3K) inhibitor wortmannin and the adenylyl cyclase inhibitor 9-cyclopentyladenine.