NCoA3 upregulation in breast cancer­associated adipocytes elicits an inflammatory profile.

Nuclear receptor coactivator 3 (NCoA3) is a transcriptional coactivator of NF­κB and other factors, which is expressed at relatively low levels in normal cells and is amplified or overexpressed in several types of cancer, including breast tumors. NCoA3 levels have been shown to be decreased during adipogenesis; however, its role in tumor­surrounding adipose tissue (AT) remains unknown. Therefore, the present study assessed the modulation of NCoA3 in breast cancer­associated adipocytes and evaluated its association with the expression of inflammatory markers. 3T3­L1 adipocytes were stimulated with conditioned medium from human breast cancer cell lines and the expression levels of NCoA3 were evaluated by reverse transcription­quantitative (q)PCR. NF­κB activation was measured by immunofluorescence, and tumor necrosis factor and monocyte chemoattractant protein 1 levels were analyzed by qPCR and dot blot assays. The results obtained from the in vitro model were supported using mammary AT (MAT) from female mice, MAT adjacent to tumors from patients with breast cancer and bioinformatics analysis. The results revealed that adipocytes expressing high levels of NCoA3 were mainly associated with a pro­inflammatory profile. In 3T3­L1 adipocytes, NCoA3 downregulation or NF­κB inhibition reversed the expression of inflammatory molecules. In addition, MAT from patients with a worse prognosis exhibited high levels of this coactivator. Notably, adipocyte NCoA3 levels could be modulated by inflammatory signals from tumors. The modulation of NCoA3 levels in synergy with NF­κB activity in MAT in a tumor context could be factors required to establish breast cancer­associated inflammation. As adipocytes are involved in the development and progression of breast cancer, this signaling network deserves to be further investigated to improve future tumor treatments.

Megakaryocyte-stromal cell interactions: Effect on megakaryocyte proliferation, proplatelet production, and survival.

Bone marrow stromal cells provide a proper environment for the development of hematologic lineages. The incorporation of different stromal cells into in vitro culture systems would be an attractive model to study megakaryopoiesis and thrombopoiesis. Our objective was to evaluate the participation of different types of stromal cells in in vitro megakaryopoiesis, thrombopoiesis, and megakaryocyte (MK) survival. CD34-positive progenitors from umbilical cord blood were differentiated into MK precursors and then cocultured with umbilical vein endothelial cells (HUVECs), bone marrow mesenchymal stem cells (MSCs), skin fibroblasts (SFs) (all human), or the mouse fibroblast cell line L929. The number of MKs (CD61-positive cells) was increased in the presence of HUVECs and SFs, whereas L929 cells decreased total and mature MK counts. With respect to thrombopoiesis, HUVECs increased proplatelet (PP)-producing MKs, while MSCs, L929 cells, and SFs had the opposite effect (immunofluorescence staining and microscopic analysis). MK survival was enhanced in MSC and SF co-cultures, as assessed by evaluation of pyknotic nuclei. However, HUVECs and L929 did not prevent apoptosis of MKs. Reciprocally, the cloning efficiency of MSCs was decreased in the presence of MKs, while the ability of stromal cells (either MSCs or SFs) to produce the extracellular matrix proteins type III collagen, fibronectin, dermatan sulfate, heparan sulfate, and prolyl 4-hydroxylase subunit ß was preserved. These data indicate that each stromal cell type performs distinctive functions that differentially modulate MK growth and platelet production and, at the same time, that MKs also modify stromal cell behavior. Overall, our results highlight the relevance of considering the influence of stromal cells in MK research as well as the close interplay of different cell types within the bone marrow milieu.

Extract from Aloysia polystachya Induces the Cell Death of Colorectal Cancer Stem Cells.

Cancer stem cells (CSCs) are an important player in the resistance of cancers to therapy. In this work, we determined the flavonoids composition and biological action of Aloysia polystachya (AP) extracts in colorectal cancer. The chemical characterization of extracts was performed by HPLC. Assays of cytotoxicity, apoptosis, migration and invasion, metalloproteases activity, clonogenic growth, tumorspheres formation, Hoechts efflux, pluripotency marker expression and sensitization to chemotherapeutic drugs were performed in vitro in human HCT116 and murine CT26 colorectal cancer cells. The AP toxicity and effect in tumor growth administered alone or in combination with 5- Fluorouracile was analyzed in vivo, including histopathological studies. We found that AP extracts induced in vitro the apoptosis of colorectal cancer cell lines decreasing the CSC proportion. Moreover, they were capable to kill 5-Fluorouracile resistant side population cells. At not toxic doses in vivo, AP extracts inhibited tumor growth. Regarding the ability to reduce the CSC population, AP extracts deserves to be investigated as a useful therapy for colorectal cancer treatment.

GPR75 receptor mediates 20-HETE-signaling and metastatic features of androgen-insensitive prostate cancer cells.

PURPOSE: Recent studies have shown that 20-hydroxyeicosatetraenoic acid (20-HETE) is a key molecule in sustaining androgen-mediated prostate cancer cell survival. Thus, the aim of this study was to determine whether 20-HETE can affect the metastatic potential of androgen-insensitive prostate cancer cells, and the implication of the newly described 20-HETE receptor, GPR75, in mediating these effects. METHODS: The expression of GPR75, protein phosphorylation, actin polymerization and protein distribution were assessed by western blot and/or fluorescence microscopy. Additionally, in vitro assays including epithelial-mesenchymal transition (EMT), metalloproteinase-2 (MMP-2) activity, scratch wound healing, transwell invasion and soft agar colony formation were used to evaluate the effects of 20-HETE agonists/antagonists or GPR75 gene silencing on the aggressive features of PC-3 cells. RESULTS: 20-HETE (0.1 nM) promoted the acquisition of a mesenchymal phenotype by increasing EMT, the release of MMP-2, cell migration and invasion, actin stress fiber formation and anchorage-independent growth. Also, 20-HETE augmented the expression of HIC-5, the phosphorylation of EGFR, NF-κB, AKT and p-38 and the intracellular redistribution of p-AKT and PKCα. These effects were impaired by GPR75 antagonism and/or silencing. Accordingly, the inhibition of 20-HETE formation with N-hydroxy-N'-(4-n-butyl-2-methylphenyl) formamidine (HET0016) elicited the opposite effects. CONCLUSIONS: The present results show for the first time the involvement of the 20-HETE-GPR75 receptor in the activation of intracellular signaling known to be stimulated in cell malignant transformations leading to the differentiation of PC-3 cells towards a more aggressive phenotype. Targeting the 20-HETE/GPR75 pathway is a promising and novel approach to interfere with prostate tumor cell malignant progression.

The inflammatory cytokine TNF contributes with RAC3-induced malignant transformation.

RAC3 is a coactivator of steroid receptors and NF-κB. It is usually overexpressed in several tumors, contributes to maintain cancer stem cells and also to induce them when is overexpressed in non-tumoral cells. In this work, we investigated whether the inflammatory cytokine TNF may contribute to the transforming effects of RAC3 overexpression in the non-tumoral HEK293 cell line. The study model included the HEK293 tumoral transformed cell line constitutively overexpressing RAC3 by stable transfection and control non-tumoral cells transfected with an empty vector. The HeLa and T47D tumoral cells that naturally overexpress RAC3 were used as positive control. We found that TNF potentiated RAC3-induced mesenchymal transition, involving an increased E-Cadherin downregulation, Vimentin and SNAIL upregulation and enhanced migratory behavior. Moreover, concerning the molecular mechanisms by which TNF potentiates the RAC3 transforming action, they involve the IKK activation, which in addition induced the ß-Catenin transactivation. Our results demonstrate that although RAC3 overexpression could be a signal strong enough to induce cancer stem cells, the inflammatory microenvironment may be playing a key role contributing to the migratory and invasive phenotype required for metastasis and cancer persistence.

High RAC3 expression levels are required for induction and maintaining of cancer cell stemness.

RAC3 is a transcription coactivator, usually overexpressed in several tumors and required to maintain the pluripotency in normal stem cells. In this work we studied the association between RAC3 overexpression on cancer cell stemness and the capacity of this protein to induce cancer stem properties in non tumoral cells. We performed in vitro and in vivo experiments using two strategies: by overexpressing RAC3 in the non tumoral cell line HEK293 and by silencing RAC3 in the human colorectal epithelial cell line HCT116 by transfection. Furthermore, we analysed public repository microarrays data from human colorectal tumors in different developmental stages. We found that RAC3 overexpression was mainly associated to CD133+ side-population of colon cancer cells and also to early and advanced stages of colon cancer, involving increased expression of mesenchymal and stem markers. In turn, RAC3 silencing induced diminished tumoral properties and cancer stem cells as determined by Hoechst efflux, tumorspheres and clonogenic growth, which correlated with decreased Nanog and OCT4 expression. In non tumoral cells, RAC3 overexpression induced tumoral transformation; mesenchymal phenotype and stem markers expression. Moreover, these transformed cells generated tumors in vivo. Our results demonstrate that RAC3 is required for maintaining and induction of cancer cell stemness.

[Autophagy. A strategy for cell survival]. / Autofagia, una estrategia de supervivencia celular.

Autophagy is a process of recycling parts of the cell. As described in this review, it occurs naturally in order to preserve cells from the accumulation of toxins, damaged molecules and organelles, and to allow processes of tissue development and differentiation. In the course of autophagy, the processing of the substrates to be recycled generates ATP, thus providing an alternative source of energy in stress situations. In this sense, under hostile conditions such as hypoxia or lack of nutrients, the autophagy process can be exacerbated leading to cell death. Some alterations in its functioning may involve the development of various pathologies, including liver damage, cancer and neurodegenerative diseases.

Autofagia, una estrategia de supervivencia celular / Autophagy. A strategy for cell survival

La autofagia es un proceso de reciclado de partes de la célula. Como se describe en esta revisión, ocurre naturalmente preservando a las células de la acumulación de toxinas, moléculas y organelas dañadas y además permite los procesos de desarrollo y diferenciación de los tejidos. En el transcurso de la autofagia, el procesamiento de los sustratos a reciclar genera ATP, lo que constituye una fuente alternativa de energía en situaciones de estrés. En este sentido, bajo condiciones hostiles como hipoxia o falta de nutrientes, el proceso puede dispararse de modo exacerbado llevando a la muerte celular. Algunas alteraciones en su funcionamiento pueden involucrar el desarrollo de diversas patologías, tales como el daño hepático, el cáncer y las enfermedades neurodegenerativas.

Autophagy is a process of recycling parts of the cell. As described in this review, it occurs naturally in order to preserve cells from the accumulation of toxins, damaged molecules and organelles, and to allow processes of tissue development and differentiation. In the course of autophagy, the processing of the substrates to be recycled generates ATP, thus providing an alternative source of energy in stress situations. In this sense, under hostile conditions such as hypoxia or lack of nutrients, the autophagy process can be exacerbated leading to cell death. Some alterations in its functioning may involve the development of various pathologies, including liver damage, cancer and neurodegenerative diseases.

Cyclin D1 is a NF-κB corepressor.

NF-κB regulates the expression of Cyclin D1 (CD1), while RAC3 is an NF-κB coactivator that enhances its transcriptional activity. In this work, we investigated the regulatory role of CD1 on NF-κB activity. We found that CD1 inhibits NF-κB transcriptional activity through a corepressor function that can be reverted by over-expressing RAC3. In both, tumoral and non-tumoral cells, the expression pattern of RAC3 and CD1 is regulated by the cell cycle, showing a gap between the maximal expression levels of each protein. The individual increase, by transfection, of either CD1 or RAC3 enhances cell proliferation. However the simultaneous and constitutive over-expression of both proteins has an inhibitory effect. Our results suggest that the relative amounts of CD1 and RAC3, and the timing of expression of these oncogenes could tilt the balance of tumor cell proliferation in response to external signals.

[Rapamycin effect on senescence and autophagy processes in human cell lines]. / Efectos de la rapamicina en los procesos de senescencia y autofagia en líneas celulares humanas.

Autophagy and senescence are both processes that firstly avoid tumor development through the inhibition of proliferation of damaged cells. However, autophagy does not imply cell death, because it is also a mechanism of cell survival under stress conditions. Concerning senescence, although these cells do not proliferate, they produce growth factors that contribute to the proliferative response of other cells. Rapamycin is an immunosupressor used in transplanted patients that inhibits the mTOR transduction signal pathway. This pathway is involved in the control of the energetic and nutritional state of the cell allowing protein synthesis and inhibiting autophagy when it is active. In this paper, the action of rapamycin over these processes was investigated and we found that a low concentration of this drug induces the senescence of a normal cell line, while a higher concentration induces autophagy of a transformed cell line. We have also determined that the oncogen RAC3 inhibits autophagy and that its expression is diminished by rapamycin. Therefore, our results contribute to a better understanding of the molecular mechanisms by which this drug is effective, given the relevance of rapamycin for potential tumor therapy.

Nuclear factor (NF)-κB controls expression of the immunoregulatory glycan-binding protein galectin-1.

The inflammatory response is a self-limiting process which involves the sequential activation of signaling pathways leading to the production of both pro- and anti-inflammatory mediators. Galectin-1 (Gal-1), an endogenous lectin found in peripheral lymphoid organs and inflammatory sites, elicits a broad spectrum of biological functions predominantly by acting as a potent anti-inflammatory factor and as a suppressive agent for T-cell responses. However, the molecular pathways underlying Gal-1 expression and function remain poorly understood. Here we identified a regulatory loop linking Gal-1 expression and function to NF-κB activation. NF-κB-activating stimuli increased Gal-1 expression on T cells, an effect which could be selectively prevented by inhibitors of NF-κB signaling. Accordingly, transient transfection of the p65 subunit of NF-κB was sufficient to induce high Gal-1 expression. Using in silico studies and chromatin immunoprecipitation analysis we have identified a functional NF-κB binding site within the first intron of the LGALS1 gene. In addition, our results show that exogenous Gal-1 can attenuate NF-κB activation, as shown by inhibition of IκB-α degradation induced by pro-inflammatory stimuli, higher cytoplasmic retention of p65, lower NF-κB DNA binding activity and impaired transcriptional activation of target genes. The present study suggest a novel regulatory loop by which NF-κB induces expression of Gal-1, which in turn may lead to negative control of NF-κB signaling.

[RAC3 overexpression is a transforming and proliferative signal that contributes to tumoral development]. / La sobreexpresión de RAC3 es una señal transformante y proliferativa que contribuye al desarrollo tumoral.

RAC3 has been firstly characterized as a nuclear receptor coactivator that is found in limited amounts in normal cells, but is over-expressed in tumors and is also an NF-kB coactivator. Although the mechanisms involved in its over-expression are not clear, it is well known that it enhances resistance to apoptosis. In this work, we investigated if there are any additional mechanisms by which RAC3 may contribute to tumor development and if TNF-a, an inflammatory cytokine that is found at high levels in cancer could increase RAC3 levels. We found that enhancement of RAC3 levels by transfection of HEK293 cells with a RAC3 expression vector induces a significant increase of cell proliferation not only in the presence, but also in the absence of serum growth factors. Moreover, the cells were transformed showing an anchorage independent growth, similar to that observed in tumoral cells. The treatment of HEK293 cells with TNF-a induced an increase in the protein levels of RAC3 and this was blocked by an NF-kB specific inhibitor, suggesting that this transcription factor is involved in the cytokine effect. We conclude that RAC3, in addition to is anti-apoptotic action, is a transforming factor that promotes the proliferation and growth independent of anchorage, and that its levels could be elevated by the action of inflammatory cytokines that are involved in the anti-tumoral response.

Imatinib resistance in multidrug-resistant K562 human leukemic cells.

The multidrug resistance phenotype (MDR) is one of the major causes of failure in cancer chemotherapy and it is associated with the over-expression of P-glycoprotein (P-gp or MDR1) in tumor cell membranes. A constitutive NF-kappaB activity has been observed in several haematological malignancies and this is associated with its anti-apoptotic role. In the present work, the relationship between NF-kappaB and MDR phenotype was evaluated in wild type K562 human leukemic cells (K562-WT) and in its vincristine-resistant counterpart, K562-Vinc cells. These data showed that K562-Vinc cells, which express an active P-gp, exhibited MDR phenotype. The resistant indexes (IC(50)(K562-Vinc)/IC(50)(K562-WT)) for structurally unrelated drugs like imatinib, doxorubicin and colchicine were 8.0+/-0.3, 2.8+/-0.4 and 44.8+/-8.8, respectively. The imatinib resistance was reversed by P-gp blockade suggesting the involvement of P-gp in imatinib transport. We observed that NF-kappaB was constitutively activated in both cell lines but in a lesser extent in K562-Vinc. The inhibition of NF-kappaB with BAY 11-7082 increased the cytotoxicity of imatinib in K562-Vinc cells but not in K562-WT. Further, the co-administration of imatinib and BAY 11-7082 sensitized multidrug-resistant K562 cells to cell death as detected by increased percentage of annexin V positive cells. The induced cell death in K562-Vinc cells was associated with activation of caspases 9 and 3. Finally, we provide data showing that BAY 11-7082 down-regulates the expression of P-gp suggesting that the activity of NF-kappaB could be functionally associated to this protein in K562 cells. Our results indicate that the vincristine-resistant K562 cells which developed MDR phenotype, exhibited resistance to imatinib associated with a functional P-gp over-expression. This resistance could be partially overcome by the inhibition of NF-kappaB pathway.

[RAC3 nuclear receptor co-activator has a protective role in the apoptosis induced by different stimuli]. / El coactivador de receptores nucleares RAC3 tiene un rol protector de la apoptosis inducida por distintos estímulos.

RAC3 belongs to the family of p160 nuclear receptors coactivators and it is over-expressed in several tumors. We have previously shown that RAC3 is a NF-kappaB coactivator. In this paper, we investigated the role of RAC3 in cell-sensitivity to apoptosis, using H2O2 in the human embryonic kidney cell line (HEK293), and tumor necrosis factor-related apoptosis inducing ligand (TRAIL) in a human chronic myeloid leukemia cell line (K562) naturally resistant to TRAIL. We observed that the tumoral K562 cells have high levels of RAC3 if compared with the non-tumoral HEK293 cells. The normal or transfected coactivator over-expression inhibits apoptosis through a diminished caspase activity and AIF nuclear translocation, increased NF-kappaB, AKT and p38, and decreased ERK activities. In contrast, inhibition of RAC3 by siRNA induced sensitivity of K562 to TRAIL-induced apoptosis. Such results suggest that over-expression of RAC3 contributes to tumor development through molecular mechanisms that do not depend strictly on acetylation and/or steroid hormones, which control cell death. This could be a possible target for future tumor therapies.

RAC3 down-regulation sensitizes human chronic myeloid leukemia cells to TRAIL-induced apoptosis.

The nuclear receptor coactivator RAC3 plays important roles in many biological processes and tumorigenesis. We found that RAC3 is over-expressed in human chronic myeloid leukemia cells K562, which are normally resistant to TRAIL-induced apoptosis. RAC3 down-regulation by siRNA rendered these cells sensitive to TRAIL-induced cell death. In addition to the up-regulation of TRAIL receptors, the process involves Bid, caspases and PARP activation, loss of mitochondrial membrane potential, and release of AIF, cytochrome c and Smac/DIABLO to the cytoplasm. We conclude that RAC3 is required for TRAIL resistance and that this anti-apoptotic function is independent of its role in hormone receptor signaling.

El coactivador de receptores nucleares RAC3 tiene un rol protector de la Apoptosis inducida por distintos estímulos / RAC3 nuclear receptor co-activator has a protective role in the apoptosis induced by different stimuli

RAC3 pertenece a la familia de coactivadores de receptores nucleares p160, y se encuentra sobreexpresado en varios tumores. Demostramos previamente que RAC3 es coactivador del factor de transcripción anti-apoptótico NF-kB. En este trabajo investigamos su rol en la apoptosis inducida por H2O2 en una línea celular no tumoral derivada de riñón embrionario humano (HEK293), y por el ligando inductor de apoptosis relacionado a TNF (TRAIL) en una línea de leucemia mieloide crónica humana (K562), naturalmente resistente a la muerte por este estímulo. Observamos que las células tumorales K562 poseen niveles altos de RAC3 comparados con las células no tumorales HEK293. La sobreexpresión normal de coactivador o por transfección, inhibe la apoptosis mediante una disminución de la activación de caspasas, translocación del factor inductor de apoptosis (AIF) al núcleo, aumento de la actividad de NF-kB y las quinasas AKT y p38 y disminución de la quinasa ERK. Lo opuesto fue observado por disminución de RAC3 mediante la técnica de ARN interferente (RNAi) en K562, aumentando así la apoptosis inducida por TRAIL. Estas evidencias sugieren que una sobreexpresión de RAC3 contribuye al desarrollo de tumores, participando en las cascadas que controlan la muerte celular por mecanismos no estrictamente dependientes de hormonas esteroideas y/o de acetilación, constituyendo esto un posible blanco de ataque para el tratamiento de tumores.

RAC3 belongs to the family of p160 nuclear receptors coactivators and it is over-expressed in several tumors. We have previously shown that RAC3 is a NF-kB coactivator. In this paper, we investigated the role of RAC3 in cell-sensitivity to apoptosis, using H2O2 in the human embryonic kidney cell line (HEK293), and tumor necrosis factor-related apoptosis inducing ligand (TRAIL) in a human chronic myeloid leukemia cell line (K562) naturally resistant to TRAIL. We observed that the tumoral K562 cells have high levels of RAC3 if compared with the non-tumoral HEK293 cells. The normal or transfected coactivator over-expression inhibits apoptosis through a diminished caspase activity and AIF nuclear translocation, increased NF-kB, AKT and p38, and decreased ERK activities. In contrast, inhibition of RAC3 by siRNA induced sensitivity of K562 to TRAIL-induced apoptosis. Such results suggest that over-expression of RAC3 contributes to tumor development through molecular mechanisms that do not depend strictly on acetylation and/or steroid hormones, which control cell death. This could be a possible target for future tumor therapies.

Suprachiasmatic astrocytes as an interface for immune-circadian signalling.

The hypothalamic suprachiasmatic nuclei (SCN), the site of a mammalian circadian clock, exhibit a dense immunoreactivity for glial fibrillary acidic protein (GFAP), a specific marker for astrocytes. Although there is evidence of a circadian variation in GFAP-IR in the hamster SCN and of the participation of glial cells in input and output mechanisms of the clock, the role of these cells within the circadian system is not clearly understood. The fact that astroglia can express and respond to cytokines suggests that they could work as mediators of immune signals to the circadian system. In the present study, we have found a daily variation of GFAP-IR in the mouse SCN, peaking during the light phase. In addition, we have identified GFAP and nuclear factor-kappaB (NF-kappaB) in glial cells within the SCN and in primary cultures of the mouse SCN. Moreover, SCN glia cultures were transfected with an NF-kappaB/luc construct whose transcriptional activity was increased with lipopolysaccharide 2 mug/ml, tumor necrosis factor-alpha 20 ng/ml, or interleukin-1alpha 100 ng/ml, after 12 hr of stimulation. These results suggest that the glial cells of the SCN can mediate input signals to the mouse circadian system coming from the immune system via NF-kappaB signaling.

Toxoplasma gondii Hsp90 is a potential drug target whose expression and subcellular localization are developmentally regulated.

Two replicative forms characterize the asexual cycle of the protozoan parasite Toxoplasma gondii: rapidly growing tachyzoites and slowly dividing encysted bradyzoites. The mechanisms that regulate the transition between these two stages are not clearly understood. However, stress inducers that also activate heat shock protein expression can trigger formation of bradyzoites in vitro. Here, we studied the association of the T.gondii Hsp90 with modulation of parasite differentiation and response to stress stimuli using RH DeltaUPRT parasites and the cystogenic strain ME49 and a clone derivative of that strain, PK. Our results show that Hsp90 transcript and protein levels increase under stress or bradyzoite differentiation conditions. Moreover, fluorescence microscopy studies revealed that Hsp90 is present in the cytosol of tachyzoites and both in the nucleus and cytosol of mature bradyzoites, suggesting a correlation between its subcellular organization and these two developmental stages. To further characterize the role for Hsp90 in bradyzoite differentiation, T.gondii tachyzoite mutants that are defective in differentiation showed the same staining pattern as tachyzoites under differentiation conditions. In addition, geldanamycin, a benzoquinone ansamycin antibiotic capable of binding and disrupting the function of Hsp90, blocked conversion both from the tachyzoite to bradyzoite and the bradyzoite to tachyzoite stage, suggesting an essential role for this protein in the regulation of stage interconversion. These results thus suggest Hsp90 may play a role in stage switch.