Calcium signaling and epigenetics: A key point to understand carcinogenesis.

Calcium (Ca2+) signaling controls a wide range of cellular processes, including the hallmarks of cancer. The Ca2+ signaling system encompasses several types of proteins, such as receptors, channels, pumps, exchangers, buffers, and sensors, of which several are mutated or with altered expression in cancer cells. Since epigenetic mechanisms are disrupted in all stages of carcinogenesis, and reversibly regulate gene expression, they have been studied by different research groups to understand their role in Ca2+ signaling remodeling in cancer cells and the carcinogenic process. In this review, we link Ca2+ signaling, cancer, and epigenetics fields to generate a comprehensive landscape of this complex group of diseases.

Canonical and non-canonical Wnt signaling are simultaneously activated by Wnts in colon cancer cells.

The Wnt signaling pathway is a crucial regulator of the intestinal epithelium homeostasis and is altered in most colon cancers. While the role of aberrant canonical, ß-catenin-dependent Wnt signaling has been well established in colon cancer promotion, much less is known about the role played by noncanonical, ß-catenin-independent Wnt signaling in this type of cancer. This work aimed to characterize the noncanonical signal transduction pathway in colon cancer cells. To this end, we used the prototype noncanonical ligand, Wnt5a, in comparison with Wnt3a, the prototype of a canonical ß-catenin activating ligand. The analysis of the expression profile of Wnt receptors in colon cancer cell lines showed a clear increase in both level expression and variety of Frizzled receptor types expressed in colon cancer cells compared with non-malignant cells. We found that Wnt5a activates a typical Wnt/Ca++ - noncanonical signaling pathway in colon malignant cells, inducing the hyperphosphorylation of Dvl1, Dvl2 and Dvl3, promoting Ca++ mobilization as a result of phospholipase C (PLC) activation via pertussis toxin-sensitive G-protein, and inducing PLC-dependent cell migration. We also found that while the co-receptor Ror2 tyrosine kinase activity is not required for Ca++ mobilization-induced by Wnt5a, it is required for the inhibitory effects of Wnt5a on the ß-catenin-dependent transcriptional activity. Unexpectedly, we found that although the prototype canonical Wnt3a ligand was unique in stimulating the ß-catenin-dependent transcriptional activity, it also simultaneously activated PLC, promoted Ca++ mobilization, and induced Rho kinase and PLC-dependent cell migration. Our data indicate, therefore, that a Wnt ligand can activate at the same time the so-called Wnt canonical and noncanonical pathways inducing the formation of complex signaling networks to integrate both pathways in colon cancer cells.

Resveratrol up-regulates ATP2A3 gene expression in breast cancer cell lines through epigenetic mechanisms.

Resveratrol (RSV) is a phytoestrogen which has been related to chemoprevention of several types of cancer. In this work, we show up to a 6-fold increased expression of ATP2A3 gene induced by RSV that triggers apoptosis and changes of intracellular Ca2+ management in MCF-7 and MDA-MB-231 breast cancer cell lines. We explored epigenetic mechanisms for that RSV-induced ATP2A3 up-regulation. The results indicate that RSV-induced ATP2A3 up-regulation correlates with about 50% of reduced HDAC activity and reduced nuclear HDAC2 expression and occupancy on ATP2A3 promoter, increasing the global acetylation of histone H3 and the enrichment of histone mark H3K27Ac on the proximal promoter of the ATP2A3 gene in MDA-MB-231 cells. We also quantified HAT activity, finding that it can be boosted with RSV treatment; however, pharmacological inhibition of p300, one of the main HATs, did not have significant effects in RSV-mediated ATP2A3 gene expression. Additionally, DNMT activity was also reduced in cells treated with RSV, as well as the expression of Methyl-DNA binding proteins MeCP2 and MBD2. However, analysis of the methylation pattern of ATP2A3 gene promoter showed un-methylated promoter in both cell lines. Taken together, the results of this work help to explain, at the molecular level, how ATP2A3 gene is regulated in breast cancer cells, and the benefits of RSV intake observed in epidemiological data, studies with animals, and in vitro models.

O-GlcNAcylation Is Involved in the Regulation of Stem Cell Markers Expression in Colon Cancer Cells.

The dynamic O-linked-N-acetylglucosamine posttranslational modification of nucleocytoplasmic proteins has emerged as a key regulator of diverse cellular processes including several hallmarks of cancer. However, the role played by this modification in the establishment of CSC phenotype has been poorly studied so far and remains unclear. In this study we confirmed the previous reports showing that colon cancer cells exhibit higher O-GlcNAc basal levels than non-malignant cells, and investigated the role played by O-GlcNAcylation in the regulation of CSC phenotype. We found that the modification of O-GlcNAcylation levels by pharmacological inhibition of the O-GlcNAc-transferase enzyme that adds O-GlcNAc (OGT), but not of the enzyme that removes it (OGA), increased the expression of all stem cell markers tested in our colon malignant cell lines, and induced the appearance of a double positive (CD44+/CD133+) small stem cell-like subpopulation (which corresponded to 1-10%) that displayed very aggressive malignant phenotype such as increased clonogenicity and spheroid formation abilities in 3D culture. We reasoned that OGT inhibition would mimic in the tumor the presence of severe nutritional stress, and indeed, we demonstrated that nutritional stress reproduced in colon cancer cells the effects obtained with OGT inhibition. Thus, our data strongly suggests that stemness is regulated by HBP/O-GlcNAcylation nutrient sensing pathway, and that O-GlcNAc nutrient sensor represents an important survival mechanism in cancer cells under nutritional stressful conditions.

Formación de biopelículas por micoplasmas de importancia médica / Biofilm formation by mycoplasmas of medical importance

El objetivo de este estudio fue evaluar la formación de biopelículas por micoplasmas de interés médico.Métodos. La formación de las biopelículas se realizó en microplacas, fueron enjuagadas con solución PBS para remover las células que no se adhirieron y se tiñeron con soluciónde cristal violeta al 0,5% durante 30 minutos. La formación de biopelículas por parte de Mycoplasma pneumoniae, Mycoplasma fermentans y Mycoplasma penetrans se analizó por medio de microscopía óptica y microscopía electrónica de barrido. Resultados. Los micoplasmas evaluados mostraron la capacidad para formar biopelículas,lo cual se evidenció por medio de la tinción de cristal violeta. Las biopelículas formadas en las microplacas y analizadas por microscopía mostraron agregados de microcolonias. La formación de biopelículas por parte de M. fermentans, M. pneumoniae y M. penetrans se presentó a las 72 horas de incubación. Se comparó la formación de biopelícula y la cuantificación de plancton, y se encontró correlación. Conclusión. Se debe considerar que este estudio se hizo bajo condiciones de laboratorioy que, para trabajos futuros, se recomienda utilizar modelos animales para definir cómo contribuyen estos agregados en la persistencia en los huéspedes. Estos resultados sugierenque la capacidad de M. fermentans, M. pneumoniae y M. penetrans para formar biopelículas puede considerarse un factor de virulencia, y un evento importante en la patogénesis yevolución en infecciones asociadas con el uso de dispositivos médicos.

The purpose of this study was to evaluate the development of biofilms by mycoplasmas of medical importance.Methods: Biofilms grown in microtiter plates were rinsed briefly in PBS to remove non-adherent cells and stained with 0,5% crystal violet solution for 30 minutes. The biofilm formation bymycoplasma species were analyzed by optical and scanning electron microscopy. Results: Three mycoplasma species were assessed for their ability to form biofilms. Crystal violet staining of biofilms in microtiter plates revealed the ability of mycoplasma to form a biofilm. Microscopic analysis of crystalviolet stained biofilms on microtiters indicated aggregation to form microcolonies. Biofilm growth by Mycoplasma fermentans, Mycoplasmapneumoniae and Mycoplasmapenetrans was followed over a time course of 72 hours. Mycoplasma were also analyzed quantitatively for biofilm formation and cell counts compared for both biofilm and plankton cells. Cell counts for biofilms showed a goodcorrelation with results obtained using crystal violet staining. Conclusion: This study has examined biofilm formation under in vitro laboratory conditions.Further studies on animal models will be crucial to determine if biofilms form in vivo and whether they contribute to mycoplasma persistence in thehost. These results suggest that the ability of M. fermentans, M. pneumoniae and M. penetrans to form a biofilm may be a virulence factor, and an important event in the pathogenesis and evolutionin infections associated with the use of medical devices.