Elvira Crescenzi

The neutrophil gelatinase-associated lipocalin (NGAL), a NF-B-regulated gene, is a survival factor for thyroid neoplastic cells

NF-κB is constitutively activated in primary human thyroid tumors, particularly in those of anaplastic type. The inhibition of NF-κB activity in the human anaplastic thyroid carcinoma cell line, FRO, leads to an increased susceptibility to chemotherapeutic drug-induced apoptosis and to the blockage of their ability to form tumors in nude mice. To identify NF-κB target genes involved in thyroid cancer, we analyzed the secretome of conditioned media from parental and NF-κB-null FRO cells. Proteomic analysis revealed that the neutrophil gelatinase-associated lipocalin (NGAL), a protein involved in inflammatory and immune responses, is secreted by FRO cells whereas its expression is strongly reduced in the NF-κB-null FRO cells. NGAL is highly expressed in human thyroid carcinomas, and knocking down its expression blocks the ability of FRO cells to grow in soft agar and form tumors in nude mice. These effects are reverted by the addition of either recombinant NGAL or FRO conditioned medium. In addition, we show that the prosurvival activity of NGAL is mediated by its ability to bind and transport iron inside the cells. Our data suggest that NF-κB contributes to thyroid tumor cell survival by controlling iron uptake via NGAL.

Nuclear Factor-κB Contributes to Anaplastic Thyroid Carcinomas through Up-Regulation of miR-146a

CONTEXT Micro-RNAs (miRNAs) have been recently involved in the modulation of several biological activities including cancer. Many human tumors show deregulated expression of miRNAs targeting oncogenes and/or tumor suppressors, thus identifying miRNAs as new molecular targets for cancer therapy. OBJECTIVES Nuclear factor (NF)-kappaB is strongly activated in human anaplastic thyroid carcinomas (ATCs). Because the regulation of miRNA expression is under control of RNA polymerase II-dependent transcription factors, we stably inactivated NF-kappaB in the ATC-derived FRO cell line and analyzed its miRNA profile in comparison with the parental counterpart by using a miRNA chip microarray. RESULTS The analysis revealed that a number of miRNAs were differentially expressed in the two cell lines. Among others, the miR-146a showed a strong down-regulation that was confirmed by quantitative real time RT-PCR. The expression of miR-146a was almost undetectable in mouse embryonic fibroblasts isolated from the RelA knockout mice and was restored after reexpression of RelA, thus indicating that miR-146a transcription was controlled by NF-kappaB. The inhibition of miR-146a expression in FRO cells decreased their oncogenic potential and increased the susceptibility to chemotherapeutic drug-induced apoptosis. No difference was found in the growth rate between untransfected and miR-146a-null FRO cells. Importantly, the miR-146a resulted in overexpression of human ATC specimens compared with the normal thyroid tissue. CONCLUSIONS Our results show that NF-kappaB contributes to anaplastic thyroid cancer up-regulating the expression of miR-146a.

Anandamide inhibits Cdk2 and activates Chk1 leading to cell cycle arrest in human breast cancer cells

This study was designed to determine the molecular mechanisms underlying the anti‐proliferative effect of the endocannabinoid anandamide on highly invasive human breast cancer cells, MDA‐MB‐231. We show that a metabolically stable analogue of anandamide, Met‐F‐AEA, induces an S phase growth arrest correlated with Chk1 activation, Cdc25A degradation and suppression of Cdk2 activity. These findings demonstrate that Met‐F‐AEA induced cell cycle blockade relies on modulated expression and activity of key S phase regulatory proteins. The observed mechanism of action, already reported for well‐known chemotherapeutic drugs, provides strong evidence for a direct role of anandamide related compounds in the activation of cell cycle checkpoints.

Low doses of cisplatin or gemcitabine plus Photofrin/photodynamic therapy : Disjointed cell cycle phase-related activity accounts for synergistic outcome in metastatic non-small cell lung cancer cells (H1299)

We compared the effects of monotherapy (photodynamic therapy or chemotherapy) versus combination therapy (photodynamic therapy plus a specific drug) on the non–small cell lung cancer cell line H1299. Our aim was to evaluate whether the additive/synergistic effects of combination treatment were such that the cytostatic dose could be reduced without affecting treatment efficacy. Photodynamic therapy was done by irradiating Photofrin-preloaded H1299 p53/p16-null cells with a halogen lamp equipped with a bandpass filter. The cytotoxic drugs used were cis-diammine-dichloroplatinum [II] (CDDP or cisplatin) and 2′,2′-difluoro-2′-deoxycytidine (gemcitabine). Various treatment combinations yielded therapeutic effects (trypan blue dye exclusion test) ranging from additive to clearly synergistic, the most effective being a combination of photodynamic therapy and CDDP. To gain insight into the cellular response mechanisms underlying favorable outcomes, we analyzed the H1299 cell cycle profiles and the expression patterns of several key proteins after monotherapy. In our conditions, we found that photodynamic therapy with Photofrin targeted G0-G1 cells, thereby causing cells to accumulate in S phase. In contrast, low-dose CDDP killed cells in S phase, thereby causing an accumulation of G0-G1 cells (and increased p21 expression). Like photodynamic therapy, low-dose gemcitabine targeted G0-G1 cells, which caused a massive accumulation of cells in S phase (and increased cyclin A expression). Although we observed therapeutic reinforcement with both drugs and photodynamic therapy, reinforcement was more pronounced when the drug (CDDP) and photodynamic therapy exert disjointed phase-related cytotoxic activity. Thus, if photodynamic therapy is appropriately tuned, the dose of the cytostatic drug can be reduced without compromising the therapeutic response. [Mol Cancer Ther 2006;5(3):776–85]

Central Role of the Scaffold Protein Tumor Necrosis Factor Receptor-associated Factor 2 in Regulating Endoplasmic Reticulum Stress-induced Apoptosis

The endoplasmic reticulum represents the quality control site of the cell for folding and assembly of cargo proteins. A variety of conditions can alter the ability of the endoplasmic reticulum (ER) to properly fold proteins, thus resulting in ER stress. Cells respond to ER stress by activating different signal transduction pathways leading to increased transcription of chaperone genes, decreased protein synthesis, and eventually to apoptosis. In the present paper we analyzed the role that the adaptor protein tumor necrosis factor-receptor associated factor 2 (TRAF2) plays in regulating cellular responses to apoptotic stimuli from the endoplasmic reticulum. Mouse embryonic fibroblasts derived from TRAF2-/- mice were more susceptible to apoptosis induced by ER stress than the wild type counterpart. This increased susceptibility to ER stress-induced apoptosis was because of an increased accumulation of reactive oxygen species following ER stress, and was abolished by the use of antioxidant. In addition, we demonstrated that the NF-κB pathway protects cells from ER stress-induced apoptosis, controlling ROS accumulation. Our results underscore the involvement of TRAF2 in regulating ER stress responses and the role of NF-κB in protecting cells from ER stress-induced apoptosis.

Ataxia Telangiectasia Mutated and p21CIP1 Modulate Cell Survival of Drug-Induced Senescent Tumor Cells: Implications for Chemotherapy

Purpose: Premature or stress-induced senescence is a major cellular response to chemotherapy in solid tumors and contributes to successful treatment. However, senescent tumor cells are resistant to apoptosis and may also reenter the cell cycle. We set out to find a means to specifically induce senescent tumor cells to undergo cell death and not to reenter the cell cycle that may have general application in cancer therapy. Experimental Design: We investigated the mechanisms regulating cell survival in drug-induced senescent tumor cells. Using immunofluorescence and flow cytometry–based techniques, we established the status of the ataxia telangiectasia mutated (ATM) signaling pathway in these cells. We assayed the requirement of ATM signaling and p21CIP1 expression for survival in premature senescent tumor cells using pharmacologic inhibitors and antisense oligonucleotides. Results: The ATM/ATR (ATM- and Rad3-related) signaling pathway was found to be constitutively active in drug-induced senescent tumor cells. We found that blocking ATM/ATR signaling with pharmacologic inhibitors, including the novel ATM inhibitors KU55933 and CGK733, induced senescent breast, lung, and colon carcinoma cells to undergo cell death. We show that the mechanism of action of this effect is directly via p21CIP1, which acts downstream of ATM. This is in contrast to the effects of ATM inhibitors on normal, untransformed senescent cells. Conclusions: Blocking ATM and/or p21CIP1 following initial treatment with a low dose of senescence-inducing chemotherapy is a potentially less toxic and highly specific treatment for carcinomas.

Bcl-2 activates a programme of premature senescence in human carcinoma cells.

The apoptosis regulator Bcl-2 has been shown to modulate cell-cycle progression, favouring a quiescent state over a proliferative state, in both normal and tumour cells. We show here that constitutive expression of Bcl-2 in human carcinoma cells results in a cell-cycle arrest that within a few days can become irreversible. Arrested cells acquire a senescent-like phenotype, which consists of several characteristic morphological alterations and increased activity of senescence-associated beta-galactosidase. The induction of the premature senescence programme is mediated by inhibition of Cdk2 kinase activity, and p27(KIP1) is required to maintain the senescent phenotype. We propose that the ability to activate an endogenous premature senescence programme allows Bcl-2 to suppress tumour growth. These results suggest that the down-regulation of Bcl-2 expression, which has been observed during the development and progression of human carcinoma, is related to the ability of Bcl-2 to severely hamper the growth of carcinoma cells and to induce a permanent cell-cycle arrest, with the features of senescence.

Roscovitine modulates DNA repair and senescence: Implications for combination chemotherapy

Purpose: Treatment of tumor cells by chemotherapy activates a series of responses ranging from apoptosis to premature senescence and repair. Survival responses are characterized by inhibition of cyclin-dependent kinases. Because inhibition of cyclin-dependent kinases represents a distinctive feature of DNA damage–induced prosurvival responses, we investigated the possibility that the cyclin-dependent kinase inhibitor roscovitine modulates drug-induced responses in human adenocarcinoma cells, favoring cell survival. Experimental Design: Sublethal concentrations of doxorubicin were used to induce premature senescence in human adenocarcinoma cells. The effect of the cyclin-dependent kinase inhibitor roscovitine on the doxorubicin-dependent cell cycle checkpoint activation and DNA repair pathways was evaluated. Results: Roscovitine reinforces doxorubicin-dependent G1 checkpoint in A549 and HEC1B cells leading to decreased frequency of double-strand breaks and to the preferential induction of senescence and enhanced clonogenic survival. However, in other tumor cell lines, such as HCT116 and H1299, combined treatment with doxorubicin and roscovitine increases the frequency of double-strand breaks and dramatically sensitizes to doxorubicin. This unexpected effect of roscovitine depends on a novel ability to inhibit DNA double-strand break repair processes and requires inactivation of the pRb pathway. Conclusions: Roscovitine, by hindering DNA repair processes, has the potential to inhibit recovery of mildly damaged tumor cells after doxorubicin treatment and to increase the susceptibility of tumor cells to chemotherapy. However, in some tumor cells, the cell cycle inhibitory function of roscovitine prevails over the DNA repair inhibitory activity, favoring premature senescence and clonogenic growth. These data indicate a novel mechanism underlying combined chemotherapy, which may have wide application in treatment of carcinomas.

NF-κB-dependent cytokine secretion controls Fas expression on chemotherapy-induced premature senescent tumor cells

Induction of a senescent phenotype in tumor cells has been linked to anticancer immune response, however, the molecular mechanisms mediating these phenomenon have not yet been determined. In this study, we present evidence that induction of premature senescence in human cancer cell lines induces Fas expression, and loss of resistance to Fas-induced apoptosis. Triggering of Fas by using the agonistic antibody CH11 or the recombinant ligand APO010, activates an apoptotic pathway responsible for cell death. Secretion of pro-inflammatory cytokines by the senescent cells, particularly TNF-α and IFN-γ, mediates Fas upregulation. Indeed, treatment of proliferating cancer cell lines with TNF-α and IFN-γ, upregulates Fas expression, while blocking TNF-α and IFN-γ by using neutralizing antibodies, decreases Fas expression in senescent cells. We also demonstrate that NF-κB has a central role in controlling the senescence-associated secretory phenotype (SASP) by the premature senescent cells, and that TNF-α and IFN-γ, transcriptionally controlled by NF-κB, are the main mediators of Fas upregulation. Our data suggest the existence of an NF-κB-dependent autocrine loop, mediated by TNF-α and IFN-γ, responsible for expression of Fas on the surface of senescent cells, and for their killing.

Exposure to modeled microgravity induces metabolic idleness in malignant human MCF-7 and normal murine VSMC cells

We investigated the effect of modeled microgravity (MMG) on normal vascular smooth muscle cells (VSMC) and neoplastic human breast cancer cells (MCF‐7). In both cell types, MMG induced partial arrest in G2M and increased p14‐3‐3, HSP70, HSP60 and p21 expression. Cells synchronized by 24 h starvation reentered the normal cycle within 24 h if released in complete medium and exposed to normal gravity, but not if exposed to MMG. Similarly, MMG prevented VSMC and MCF‐7 cells from overcoming growth arrest and re‐synthesizing DNA. This study shows that cells adjust their metabolic rate in response to MMG.