Chemoresistance in H-Ferritin Silenced Cells: The Role of NF-κB.

Nuclear Factor-κB (NF-κB) is frequently activated in tumor cells contributing to aggressive tumor growth and resistance to chemotherapy. Here we demonstrate that Ferritin Heavy Chain (FHC) protein expression inversely correlates with NF-κB activation in cancer cell lines. In fact, FHC silencing in K562 and SKOV3 cancer cell lines induced p65 nuclear accumulation, whereas FHC overexpression correlated with p65 nuclear depletion in the same cell lines. In FHC-silenced cells, the p65 nuclear accumulation was reverted by treatment with the reactive oxygen species (ROS) scavenger, indicating that NF-κB activation was an indirect effect of FHC on redox metabolism. Finally, FHC knock-down in K562 and SKOV3 cancer cell lines resulted in an improved cell viability following doxorubicin or cisplatin treatment, being counteracted by the transient expression of inhibitory of NF-κB, IκBα. Our results provide an additional layer of information on the complex interplay of FHC with cellular metabolism, and highlight a novel scenario of NF-κB-mediated chemoresistance triggered by the downregulation of FHC with potential therapeutic implications.

Human haematological and epithelial tumor-derived cell lines express distinct patterns of onco-microRNAs.

MicroRNAs post-transcriptionally regulate gene expression thus playing a critical role in a wide range of physiological and pathological processes, including cancer initiation and progression. Moreover, a growing number of evidences highlights that miRNAs themselves are differentially expressed between normal and malignant tissues. In this study, we analysed differences in miRNA expression profile between haematological and epithelial tumor-derived cell lines and explored their role in definying different cancer cells phenotypes. Cancer Focus microRNA PCR Panel was used to analyze eighty-four oncomiRNAs in two human haematological (K562 and HL-60) and in two epithelial (H460 and MCF-7) cancer cell lines. Bioinformatic tools were used to identify miRNA-specific signatures and to discover potentially deregulated pathways. Our analysis led to the identification of i) a large repertoire of miRNAs commonly expressed in the four cell lines, including two equally highly expressed (UPmiRs) and four equally low expressed (DNmiRs); ii) two miRNAs signatures, one associated with the haematological and one with the epithelial cell lines; iii) miRNA signatures specific for the acute or for the chronic myeloid leukemic cells; iv) miRNA signatures specific for the lung or for the breast carcinoma cells. As a whole, these results strengthen the significance of miRNAs profiling in human cancer subtyping, providing the ground for the identification of novel potential biomarkers for specific cancer cell phenotypes.

Ferritin Heavy Subunit Silencing Blocks the Erythroid Commitment of K562 Cells via miR-150 up-Regulation and GATA-1 Repression.

Erythroid differentiation is a complex and multistep process during which an adequate supply of iron for hemoglobinization is required. The role of ferritin heavy subunit, in this process, has been mainly attributed to its capacity to maintain iron in a non-toxic form. We propose a new role for ferritin heavy subunit (FHC) in controlling the erythroid commitment of K562 erythro-myeloid cells. FHC knockdown induces a change in the balance of GATA transcription factors and significantly reduces the expression of a repertoire of erythroid-specific genes, including α- and γ-globins, as well as CD71 and CD235a surface markers, in the absence of differentiation stimuli. These molecular changes are also reflected at the morphological level. Moreover, the ability of FHC-silenced K562 cells to respond to the erythroid-specific inducer hemin is almost completely abolished. Interestingly, we found that this new role for FHC is largely mediated via regulation of miR-150, one of the main microRNA implicated in the cell-fate choice of common erythroid/megakaryocytic progenitors. These findings shed further insight into the biological properties of FHCand delineate a role in erythroid differentiation where this protein does not act as a mere iron metabolism-related factor but also as a critical regulator of the expression of genes of central relevance for erythropoiesis.

Nandrolone and stanozolol induce Leydig cell tumor proliferation through an estrogen-dependent mechanism involving IGF-I system.

Several substances such as anabolic androgenic steroids (AAS), peptide hormones like insulin-like growth factor-I (IGF-I), aromatase inhibitors and estrogen antagonists are offered via the Internet, and are assumed without considering the potential deleterious effects that can be caused by their administration. In this study we aimed to determine if nandrolone and stanozolol, two commonly used AAS, could have an effect on Leydig cell tumor proliferation and if their effects could be potentiated by the concomitant use of IGF-I. Using a rat Leydig tumor cell line, R2C cells, as experimental model we found that nandrolone and stanozolol caused a dose-dependent induction of aromatase expression and estradiol (E2) production. When used in combination with IGF-I they were more effective than single molecules in inducing aromatase expression. AAS exhibited estrogenic activity and induced rapid estrogen receptor (ER)-dependent pathways involving IGF1R, AKT, and ERK1/2 phosphorylation. Inhibitors for these kinases decreased AAS-dependent aromatase expression. Up-regulated aromatase levels and related E2 production increased cell proliferation as a consequence of increased cyclin E expression. The observation that ER antagonist ICI182,780 was also able to significantly reduce ASS- and AAS + IGF-induced cell proliferation, confirmed a role for estrogens in AAS-dependent proliferative effects. Taken together these data clearly indicate that the use of high doses of AAS, as it occurs in doping practice, enhances Leydig cell proliferation, increasing the risk of tumor development. This risk is higher when AAS are used in association with IGF-I. To our knowledge this is the first report directly associating AAS and testicular cancer.

Inhibition of cyclooxygenase-2 down-regulates aromatase activity and decreases proliferation of Leydig tumor cells.

Our recent studies have revealed that estrogens stimulate an autocrine mechanism determining Leydig tumor cell proliferation. Estrogen overproduction is due to an elevated steroidogenic factor-1 (SF-1) expression and cAMP-response element-binding protein (CREB) phosphorylation, both inducing aromatase overexpression. Although we have shown that increased SF-1 expression depends mainly on higher local insulin-like growth factor I production, the mechanisms and factors determining increased CREB activation in Leydig tumor cells are not completely understood. In this study, we investigated the role of cyclooxygenase-2 (COX-2) in CREB dependent-aromatase expression in Leydig tumor cells. We found that COX-2 is expressed in rat and human Leydigiomas as well as in the rat Leydig tumor cell line R2C, but not in normal testis. Our data indicate that in R2C cells the COX-2-derived prostaglandin E2 (PGE2) binds the PGE2 receptor EP4 and activates protein kinase A (PKA) and ultimately CREB. Inhibitors for COX-2 (NS398), EP4 (AH23848), and PKA (H89) decreased aromatase expression and activity as a consequence of a decreased phosphorylated CREB recruitment to the PII promoter of the aromatase gene. The COX-2/PGE2/PKA pathway also seems to be involved in aromatase post-translational activation, an observation that requires further studies. The reduction in aromatase activity was responsible for a drop in estrogen production and subsequent reduction in cyclin E expression resulting in a decrease in tumor Leydig cell proliferation. Furthermore, COX-2 silencing caused a significant decrease in CREB phosphorylation, aromatase expression, and R2C cell proliferation. These novel findings clarify the mechanisms involved in the growth of Leydig cell tumors and should be taken into account in determining new therapeutic approaches.

Ferritin heavy subunit enhances apoptosis of non-small cell lung cancer cells through modulation of miR-125b/p53 axis.

Ferritin is a nanocage protein composed by the variable assembly of 24 heavy and light subunits. As major intracellular iron storage protein, ferritin has been studied for many years in the context of iron metabolism. However, recent evidences have highlighted its role, in particular that of the heavy subunit (FHC), in pathways related to cancer development and progression, such as cell proliferation, growth suppressor evasion, cell death inhibition, and angiogenesis. At least partly, the involvement in these pathways is due to the ability of FHC to control the expression of a repertoire of oncogenes and oncomiRNAs. Moreover, the existence of a feedback loop between FHC and the tumor suppressor p53 has been demonstrated in different cell types. Here, we show that ectopic over-expression of FHC induces the promoter hypermethylation and the down-regulation of miR-125b that, in turn, enhances p53 protein expression in non-small cell lung cancer (NSCLC) cell lines. Notably, analysis by absolute quantitative RT-PCR of FHC, miR-125b, and p53 strongly suggests that this axis might be active in human NSCLC tissue specimens. In vitro, FHC over-expression attenuates survival of NSCLC cells by inducing p53-mediated intrinsic apoptosis that is partially abrogated upon miR-125b re-expression. Overall, our findings demonstrate that FHC acts as a tumor suppressor gene, thus providing a potential molecular strategy for induction of NSCLC apoptotic cell death.

Caffeine Positively Modulates Ferritin Heavy Chain Expression in H460 Cells: Effects on Cell Proliferation.

Both the methylxanthine caffeine and the heavy subunit of ferritin molecule (FHC) are able to control the proliferation rate of several cancer cell lines. While caffeine acts exclusively as a negative modulator of cell proliferation, FHC might reduce or enhance cell viability depending upon the different cell type. In this work we have demonstrated that physiological concentrations of caffeine reduce the proliferation rate of H460 cells: along with the modulation of p53, pAKT and Cyclin D1, caffeine also determines a significant FHC up-regulation through the activation of its transcriptional efficiency. FHC plays a central role in the molecular pathways modulated by caffeine, ending in a reduced cell growth, since its specific silencing by siRNA almost completely abolishes caffeine effects on H460 cell proliferation. These results allow the inclusion of ferritin heavy subunits among the multiple molecular targets of caffeine and open the way for studying the relationship between caffeine and intracellular iron metabolism.

FTH1P3, a Novel H-Ferritin Pseudogene Transcriptionally Active, Is Ubiquitously Expressed and Regulated during Cell Differentiation.

Ferritin, the major iron storage protein, performs its essential functions in the cytoplasm, nucleus and mitochondria. The variable assembly of 24 subunits of the Heavy (H) and Light (L) type composes the cytoplasmic molecule. In humans, two distinct genes code these subunits, both belonging to complex multigene families. Until now, one H gene has been identified with the coding sequence interrupted by three introns and more than 20 intronless copies widely dispersed on different chromosomes. Two of the intronless genes are actively transcribed in a tissue-specific manner. Herein, we report that FTH1P3, another intronless pseudogene, is transcribed. FTH1P3 transcript was detected in several cell lines and tissues, suggesting that its transcription is ubiquitary, as it happens for the parental ferritin H gene. Moreover, FTH1P3 expression is positively regulated during the cell differentiation process.

H-ferritin-regulated microRNAs modulate gene expression in K562 cells.

In a previous study, we showed that the silencing of the heavy subunit (FHC) offerritin, the central iron storage molecule in the cell, is accompanied by a modification in global gene expression. In this work, we explored whether different FHC amounts might modulate miRNA expression levels in K562 cells and studied the impact of miRNAs in gene expression profile modifications. To this aim, we performed a miRNA-mRNA integrative analysis in K562 silenced for FHC (K562shFHC) comparing it with K562 transduced with scrambled RNA (K562shRNA). Four miRNAs, namely hsa-let-7g, hsa-let-7f, hsa-let-7i and hsa-miR-125b, were significantly up-regulated in silenced cells. The remarkable down-regulation of these miRNAs, following FHC expression rescue, supports a specific relation between FHC silencing and miRNA-modulation. The integration of target predictions with miRNA and gene expression profiles led to the identification of a regulatory network which includes the miRNAs up-regulated by FHC silencing, as well as91 down-regulated putative target genes. These genes were further classified in 9 networks; the highest scoring network, "Cell Death and Survival, Hematological System Development and Function, Hematopoiesis", is composed by 18 focus molecules including RAF1 and ERK1/2. We confirmed that, following FHC silencing, ERK1/2 phosphorylation is severely impaired and that RAF1 mRNA is significantly down-regulated. Taken all together, our data indicate that, in our experimental model, FHC silencing may affect RAF1/pERK1/2 levels through the modulation of a specific set of miRNAs and add new insights in to the relationship among iron homeostasis and miRNAs.

H ferritin silencing induces protein misfolding in K562 cells: A Raman analysis.

The redox state of the cell is involved in the regulation of many physiological functions as well as in the pathogenesis of several diseases, and is strictly dependent on the amount of iron in its catalytically active state. Alterations of iron homeostasis determine increased steady-state concentrations of Reactive Oxygen Species (ROS) that cause lipid peroxidation, DNA damage and altered protein folding. Ferritin keeps the intracellular iron in a non-toxic and readily available form and consequently plays a central role in iron and redox homeostasis. The protein is composed by 24 subunits of the H- and L-type, coded by two different genes, with structural and functional differences. The aim of this study was to shed light on the role of the single H ferritin subunit (FHC) in keeping the native correct protein three-dimensional structure. To this, we performed Raman spectroscopy on protein extracts from K562 cells subjected to FHC silencing. The results show a significant increase in the percentage of disordered structures content at a level comparable to that induced by H2O2 treatment in control cells. ROS inhibitor and iron chelator were able to revert protein misfolding. This integrated approach, involving Raman spectroscopy and targeted-gene silencing, indicates that an imbalance of the heavy-to-light chain ratio in the ferritin composition is able to induce severe but still reversible modifications in protein folding and uncovers new potential pathogenetic mechanisms associated to intracellular iron perturbation.

GPER agonist G-1 decreases adrenocortical carcinoma (ACC) cell growth in vitro and in vivo.

We have previously demonstrated that estrogen receptor (ER) alpha (ESR1) increases proliferation of adrenocortical carcinoma (ACC) through both an estrogen-dependent and -independent (induced by IGF-II/IGF1R pathways) manner. Then, the use of tamoxifen, a selective estrogen receptor modulator (SERM), appears effective in reducing ACC growth in vitro and in vivo. However, tamoxifen not only exerts antiestrogenic activity, but also acts as full agonist on the G protein-coupled estrogen receptor (GPER). Aim of this study was to investigate the effect of a non-steroidal GPER agonist G-1 in modulating ACC cell growth. We found that G-1 is able to exert a growth inhibitory effect on H295R cells both in vitro and, as xenograft model, in vivo. Treatment of H295R cells with G-1 induced cell cycle arrest, DNA damage and cell death by the activation of the intrinsic apoptotic mechanism. These events required sustained extracellular regulated kinase (ERK) 1/2 activation. Silencing of GPER by a specific shRNA partially reversed G-1-mediated cell growth inhibition without affecting ERK activation. These data suggest the existence of G-1 activated but GPER-independent effects that remain to be clarified. In conclusion, this study provides a rational to further study G-1 mechanism of action in order to include this drug as a treatment option to the limited therapy of ACC.

Targeting estrogen receptor-α reduces adrenocortical cancer (ACC) cell growth in vitro and in vivo: potential therapeutic role of selective estrogen receptor modulators (SERMs) for ACC treatment.

CONTEXT: Adrenocortical carcinoma (ACC) is a rare tumor with a very poor prognosis and no effective treatment. ACC is characterized by an increased production of IGF-II and by estrogen receptor (ER)-α up-regulation. OBJECTIVE: The objective of this study was to define the role played by ERα in 17ß-estradiol (E2)- and IGF-II-dependent ACC growth and evaluate whether selective estrogen receptor modulators are effective in controlling ACC growth in vivo. EXPERIMENTAL DESIGN: The human adrenocortical cell line H295R was used as an in vitro model and to generate xenograft tumors in athymic nude mice. RESULTS: In H295R cells IGF-II controlled expression of steroidogenic factor-1 that, in turn, increased aromatase transcription and, consequently, estrogen production, inducing cell proliferation. ERα silencing significantly blocked E2- and IGF-II-dependent cell proliferation. This effect was dependent on the regulation of cyclin D1 expression by ERα, activated in response to both E2 and IGF-II. In fact, IGF-II induced ERα activation by phosphorylating serine 118 and 167. Furthermore, we demonstrated that ERα mediated E2-induced nongenomic signaling that stimulated IGF-I receptor (IGF1R), ERK1/2, and AKT phosphorylation, resulting in a ligand-independent activation of the IGF1R-induced pathway. In addition, E2 potentiated this pathway by up-regulating IGF1R expression as a consequence of increased cAMP-responsive element binding protein activation and binding to IGF1R promoter. The estrogen antagonist, hydroxytamoxifen, the active metabolite of tamoxifen, reduced IGF1R protein levels and both E2- and IGF-II-induced cell proliferation. Moreover, H295R xenograft growth was strongly reduced by tamoxifen. CONCLUSION: These findings establish a critical role for ERα in E2- and IGF-II-dependent ACC proliferation and provide a rationale for targeting ERα to control the proliferation of ACC.