Senescence and cell death pathways and their role in cancer therapeutic outcome.

Anticancer drug-induced tumor suppression may involve mechanisms of protection against neoplastic transformation that are normally latent in mammalian cells and consist in a genetic program implemented during anti-tumoral defense. This defense program results in the self elimination of cells harboring potentially dangerous mutations by triggering cell death through apoptosis and/or autophagy or in the execution of a program that leads to a permanent growth arrest known as senescence. These responses are considered crucial tumor suppressive mechanisms and their study appears to be essential to develop therapeutical procedures based on the enhancement of the different responses. This review summarizes fundamental knowledge on the underlying mechanisms able to limit excessive or aberrant cellular proliferation and on the prognostic value of both apoptosis and senescence detection. In addition, interesting evidence showing that different drugs induce senescence or cell death depending on the genetic features of the tumor cells as well as on the integrity of the relative pathways is reported.

Immunomodulatory activity of a plant extract containing human papillomavirus 16-E7 protein in human monocyte-derived dendritic cells.

This study reports the immunomodulatory activity on human monocyte derived dendritic cells (MDDCs) of a vaccine preparation shown to be effective against an HPV16-related tumour in an animal model. The vaccine is composed of extract from Nicotiana benthamiana leaves containing HPV16 E7 protein expressed by a potato virus X-derived vector (NbPVX-E7). The effect of the extract was evaluated on MDDC differentiation and maturation by monitoring the phenotypic expression of specific markers. The results show that NbPVX-E7 does not induce monocyte differentiation to dendritic cells, but does induce MDDC maturation. Plant extract does not influence MDDC-uptake of E7-FITC while it significantly improves the Ovalbumin-FITC uptake, considered as a model antigen. Importantly, NbPVX-E7-pulsed MDDCs/PBMCs are able to prime human blood-derived lymphocytes from healthy individuals to induce HPV16 E7-specific cytotoxic activity. This is a propaedeutic study for a possible use of E7-containing plant extract in human immunotherapy of HPV-related lesions.

Purification and Characterization of Antibodies in Single-Chain Format against the E6 Oncoprotein of Human Papillomavirus Type 16.

In Human Papillomaviruses- (HPV-) associated carcinogenesis, continuous expression of the E6 oncoprotein supports its value as a potential target for the development of diagnostics and therapeutics for HPV cancer. We previously reported that the I7 single-chain antibody fragment (scFv) specific for HPV16 E6, expressed as an intrabody by retroviral system, could inhibit significantly the growth of cervical cancer cells in vitro and was even able to reduce tumor development in experimental HPV-related cancer models. Nevertheless, for the development of therapeutic tools to be employed in humans, it is important to achieve maximum safety guarantee, which can be provided by the protein format. In the current study, two anti-16E6 scFvs derived from I7 were expressed in E. coli and purified in soluble form by affinity chromatography. Specificity, sensitivity and stability in physiologic environment of the purified scFvs were demonstrated by binding studies using recombinant 16E6 as an antigen. The scFvs functionality was confirmed by immunofluorescence in cervical cancer cells, where the scFvs were able to recognize the nuclear E6. Furthermore, an antiproliferative activity of the scFvI7nuc delivered in protein format to HPV16-positive cell lines was observed. Our results demonstrate that functional anti-16E6 scFvs can be produced in E. coli, suggesting that such purified antibodies could be used in the diagnosis and treatment of HPV-induced malignancies.

Perspectives in biomolecular therapeutic intervention in cancer: from the early to the new strategies with type I interferons.

Interferon (IFN) was the first cytokine produced by recombinant DNA technology used in wide-spread clinical treatment of infectious diseases as well as malignancies. The IFN clinical potential was clearly realized from the outset. However, IFN represents one of the most controversial drugs of our time, as remarkable cycles of promise and disappointment have affected its development and use. Considerable evidence regarding anti-tumor activities of IFNs has been reported. In this paper we focus on molecular bases of the IFN system that may relate to its antitumor activities. Many of the numerous genes transcriptionally activated by IFNs have been shown to encode proteins that activate immune recognition of tumor cells, directly or indirectly exert tumor suppressor activity and/or control tumor cell cycle and programmed cell death. In addition, a physiological relevant function for endogenous type I IFN in cancer immunoediting process and a new way to IFN clinical use based on gene therapy or vaccine-like approaches have recently been suggested. The identification of selected tissue-specific and/or tumor-specific target pathways as well as of different type I IFN tumor escape and resistance mechanisms may provide novel approaches in the search for new IFN-based therapeutic strategies to circumvent cancer disease or improve clinical outcome. Promising IFN treatment has been recently defined by using novel pharmaceutical preparations with a more favourable pharmacokinetic response, also in combination with other bioreagents or other modalities of therapy. Translational research, linking both basic and clinical research, will lead to a new rationale for the use of IFN in cancer therapy.

Modulation of ferritin H-chain expression in Friend erythroleukemia cells: transcriptional and translational regulation by hemin.

The mechanisms that regulate the expression of the H chain of the iron storage protein ferritin in Friend erythroleukemia cells (FLCs) after exposure to hemin (ferric protoporphyrin IX), protoporphyrin IX, and ferric ammonium citrate (FAC) have been investigated. Administration of hemin increases the steady-state level of ferritin mRNA about 10-fold and that of ferritin protein expression 20-fold. Experiments with the transcriptional inhibitor actinomycin D and transfection studies demonstrate that the increment in cytoplasmic mRNA content results from enhanced transcription of the ferritin H-chain gene and cannot be attributed to stabilization of preexisting mRNAs. In addition to transcriptional effects, translational regulation induces the recruitment of stored mRNAs into functional polyribosomes after hemin and FAC administration, resulting in a further increase in ferritin synthesis. Administration of protoporphyrin IX to FLCs produces divergent transcriptional and translational effects. It increases transcription but appears to suppress ferritin mRNA translation. FAC treatment increases the mRNA content slightly (about twofold), and the ferritin levels rise about fivefold over the control values. We conclude that in FLCs, hemin induces ferritin H-chain biosynthesis by multiple mechanisms: a transcriptional mechanism exerted also by protoporphyrin IX and a translational one, not displayed by protoporphyrin IX but shared with FAC.

Interferon alpha-2b and retinoic acid combined treatment affects proliferation and gene expression of human cervical carcinoma cells.

The in vivo and in vitro antitumor effectiveness of IFNs is well documented. Their combination with differentiating agents, such as retinoic acid, has been demonstrated to be a promising therapy for patients with advanced squamous cell cancer of the skin and the cervix. However, the mechanisms that mediate these antitumor responses are not yet known. We studied the epidermoid cell line ME 180 derived from human cervical carcinoma to test its responsiveness to IFN-alpha-2b (INTRON A) and all-trans-retinoic acid (RA). Both agents have demonstrated ability to inhibit the growth of ME 180 cells in a dose- and time-dependent manner. The antiproliferative effect was further increased by the treatment with IFN-alpha-2b and RA combined. In accordance with this result, we found that the combination of the two agents has the effect of increasing the expression of the 2-5A synthetase gene, which is thought to play a key role in antigrowth responses to IFNs. At increased levels of 2-5A synthetase mRNA corresponds a significant increase in 2-5A synthetase activity. Although RA per se has no effect on the 2-5A synthetase expression, when it is combined with IFN-alpha-2b it appears to be able to potentiate the IFN-induced 2-5A synthetase expression. Moreover, the combination of IFN-alpha-2b and RA produces a similar effect also on the expression of the HLA-A2 gene, which has been shown to be induced in ME 180 cells both by IFN-alpha-2b and RA alone. In view of the possible mechanisms of action of the two agents, it is interesting to note that their combination increases, although transiently, the expression of IRF1, which codes for a transcription factor that regulates IFN gene expression and is thought to be involved in the regulation of IFN-induced effects and in mediating cell death or apoptosis.

Interferon-beta induces S phase slowing via up-regulated expression of PML in squamous carcinoma cells.

Type I Interferon (IFN) and all-trans retinoic acid (RA) inhibit cell proliferation of squamous carcinoma cell lines (SCC). Examinations of growth-affected cell populations show that SCC lines ME-180 and SiHa treated with IFN-beta undergo a specific slower progression through the S phase that seems to trigger cellular death. In combination treatment RA potentiates IFN-beta effect in SCC ME-180 but not in SiHa cell line, partially resistant to RA antiproliferative action. RA added as single agent affects cell proliferation differently by inducing a slight G1 accumulation. The IFN-beta-induced S phase lengthening parallels the increased expression of PML, a nuclear phosphoprotein specifically up-regulated at transcriptional level by IFN, whose overexpression induces cell growth inhibition and tumor suppression. We report that PML up-regulation may account for the alteration of cell cycle progression induced by IFN-beta in SCC by infecting cells with PML-PINCO recombinant retrovirus carrying the PML-3 cDNA under the control of the 5' LTR. In fact PML overexpression reproduces the IFN-beta-induced S phase lengthening. These findings provide important insight into the mechanism of tumor suppressing function of PML and could allow PML to be included in the pathways responsible for IFN-induced cell growth suppression.

TNF-related apoptosis-inducing ligand (TRAIL) as a pro-apoptotic signal transducer with cancer therapeutic potential.

The powerful inducer of apoptosis Apo2L/TNF-related apoptosis-inducing ligand (TRAIL) has generated exciting promise as a potential tumour specific cancer therapeutic agent, since it selectively induces apoptosis in transformed versus normal cells. Interferons (IFNs) are important modulators of TRAIL expression, thus the ligand appears to play an important role in surveillance against viral infection and malignant transformation. In the light of the emerging importance of TRAIL in cancer therapy, we will discuss the molecular basis of the cooperation of TRAIL and IFNs or chemotherapeutic drugs. In particular, we will focus on the data known to date concerning the biochemical pathways leading to TRAIL-induced apoptosis in specific cancer cells and warranting further work to enable the investigation in cancer patients.

Poly(ADP-ribose) polymerase activity is inhibited by 2',5'-oligoadenylates in mouse L-cells.

Down regulation of poly(ADP-ribose)polymerase (ADPRP) activity was observed in mouse LW-cells after treatment with 2'-5'oligoadenylates or with fibroblast interferon and poly(rI) poly(rC). The poly(rI) poly(rC)-induced inhibition of the enzymatic activity correlates with the observed increase of endogenous 2',5'-oligoadenylate cores which were reported to be potent inhibitors of ADPRP in vitro.

Hemin inhibits the interferon-beta-induced antiviral state in established cell lines.

Hemin and other metalloporphyrins are known as very versatile compounds in nature, because they are able to carry out numerous functions in a free state or in association with specific proteins. When Friend murine erythroleukemia cells are treated with IFN-beta plus 100 microM hemin, the antiviral state is not observed, whereas the antiviral effect of IFN-gamma is unaffected by hemin treatment. This inhibitory effect of hemin is not restricted to erythroid cells. In fact, it is also observed in murine L929 and in human cell lines treated with IFN-beta. Neither trivalent iron in other forms nor hemin analogs (such as protoporphyrin IX or Sn(2+)-protoporphyrine IX) mimic this effect. Conversely, Co(3+)-protoporphyrin IX was as effective as hemin. At the transcriptional level, results obtained by run-on assays on nuclei from IFN-treated cells indicate that hemin does not completely inhibit IFN-beta induction of 2-5A synthetase gene(s) at 6 h of treatment but abolishes it at 24 h. In addition, hemin is able to inhibit the accumulation of IFN-induced 2-5A synthetase mRNAs. Experiments carried out to investigate the hemin effect on the early steps of the IFN signaling pathway indicate that hemin interferes with the ability of type I IFN to bind to its receptor, probably by a direct action on the IFN molecule.

Interferons and oncogenes in the control of cell growth and differentiation: working hypothesis and experimental facts.

This short review summarizes available evidence for (i) growth regulatory properties of exogenous as well as recently described autocrine IFNs, (ii) down-regulation of cellular oncogene expression with emphasis on c-myc and (iii) the possible involvement of the IFN-regulated 2-5A pathway at these levels. Initially described as a part of the IFN-induced antiviral mechanism, this double-stranded RNA-activated pathway leads to the preferential degradation of viral mRNAs in IFN-treated virus-infected cells probably through localized activation at the site of virus replication. Such mechanisms could be involved in the regulation of the stability of rapidly turning over mRNAs as for instance c-myc mRNA in IFN-treated cells. Whatever the elegance of the concept, however, experimental evidence is essentially circumstantial; tools developed in our group to strengthen the demonstration are briefly described.

Effect of mouse interferon alpha/beta on the expression of H-2 (class I) antigens and on the levels of 2'-5' oligoadenylate synthetase activity in interferon-sensitive and interferon-resistant Friend leukemia cell tumors in mice.

DBA/2 mice were injected intraperitoneally (i.p.) with interferon-sensitive 745 or interferon-resistant 3C1-8 Friend erythroleukemia cells (FLC) and then injected i.p. with mouse interferon alpha/beta. Interferon enhanced the expression of histocompatibility (H-2) antigens on individual 745 FLC within the peritoneum, but did not alter the expression of H-2 antigens on individual 3C1-8 FLC. Likewise, interferon treatment resulted in an increase in the level of 2'-5' oligo-adenylate (2-5A) synthetase activity in 745 FLC, but did not affect the level of activity in 3C1-8 FLC. These results provide evidence that the phenotype of interferon sensitivity or resistance of FLC does not change within the peritoneum. An incidental finding was that the basal level of 2-5A synthetase activity of in vivo passaged 745 cells was greater than that of 3C1-8 FLC. The finding that injection of mice bearing 745 FLC with antibody to mouse interferon alpha/beta reduced the level of 2-5A synthetase activity in these cells, but did not alter the level of 2-5A activity in 3C1-8 FLC, suggests that endogenous interferon in the peritoneum may have been the responsible factor.

Transcriptional induction of H2 (class I) antigens and beta 2 microglobulin by interferon-gamma in interferon-sensitive and interferon-resistant Friend leukemia cells.

The effect of interferons (IFNs) type I (alpha/beta) and type II (gamma) on the stimulation of H2-Dd (class I) and beta 2 microglobulin genes transcription was analysed in IFN-sensitive (w.t.) and IFN-resistant Friend erythroleukemia cells (FLC). Type I IFN enhances the expression of H2-Dd and beta 2 microglobulin genes in w.t. FLC but does not modulate the expression of these genes in clones resistant to IFN-alpha/beta. IFN type II treatment of w.t. and IFN-alpha/beta resistant cell lines results in an increased expression of H2-Dd and beta 2 microglobulin genes, while being ineffective in the cell clone resistant to both types of IFNs. In this cell system the effect(s) of IFN type II is in part mediated by the induction of IFN-beta. The results reported in the present paper suggest that the IFN-gamma is able per se to increase the expression of H2-Dd and beta 2 microglobulin genes; since a reduced but clearly evident stimulation of the expression of these genes was observed in the FLC clone totally resistant to type I IFN.

Staurosporine inhibits interferon alpha-induced gene expression in Friend erythroleukemia cells through a PKC independent pathway.

Interferons (IFNs) are able to induce an increased transcription of several genes, which can occur within minutes of the binding of IFNs to their receptors. The specific induced transcription is mediated by the interaction of specific transcription factors with regulatory DNA sequences that lie upstream the promoters of IFN induced genes. Phosphorylation of IFN-specific transcription factors is required for activation of transcription. We have studied the antiviral effect and the induction of gene expression by IFN-alpha in Friend Leukemia cells (FLC) in the presence of a series of inhibitors of known kinases. Protein kinase C (PKC)-specific inhibitors, i.e. calphostin C and bisindolylmaleimide, failed to influence the IFN-induced gene expression and the antiviral state. Likewise, little or no effect was found using inhibitors such as H7 or K252a. Chronic exposure of FLC to phorbol ester, that causes down regulation of PKC (the effectiveness of TPA treatment was proven by PKC enzymatic assay), has no effect on IFN-alpha action. In addition, treatment of FLC with staurosporine prevented the induction of IFN-stimulated genes and the establishment of the antiviral state only when this drug was used at high dosage (500 nM). This result indicates that, also in FLC, activation of PKC is not involved in the transcriptional response of the cells to IFN-alpha treatment. The non receptor tyrosine kinases of the JAK family that take part in the IFNs-specific transduction pathways could be the target of the staurosporine specific inhibition of the IFN-alpha action.

Spectrum of biological activity of interferons.

The interferons comprise a group of proteins first identified by their ability to protect cells against virus infections but also capable of influencing cellular physiology. They are synthesized and secreted by a variety of cell types in response to various inducers. Their effects include antiviral action, inhibition of cell proliferation, modulation of cell differentiation and activation of various cell types in immune system. This review aims to summarize the current state of biology of interferon action with special emphasis on those aspects related to the use of these molecules in antitumoral therapy. The antitumor effects of IFNs results from pleiotropic IFN activity exerted either directly on tumor cells (i.e. antiproliferative effects, effects on oncogene expression, on cell differentiation and enhanced expression of cell surface antigens), or via indirect effects (i.e. activation of effector mechanisms of the host as modulation of the expression of the major histocompatibility antigens, effects on macrophages, NK, T and B cells).

Cancer regulator microRNA: potential relevance in diagnosis, prognosis and treatment of cancer.

MicroRNAs (miRNAs) are small (typically 22 nucleotides) non-coding, endogenous, single-stranded RNAs. MiRNA genes are evolutionarily conserved and are located within the introns or exons of protein-coding genes, as well as in intergenic areas. Before the discovery of miRNAs, it had been known that a large part of the genome is not translated into proteins. This so called "junk" DNA was thought to be evolution debris with no function. Recently, the explosive research in this area has established miRNAs as powerful regulators of gene expression. While only about 1,424 human miRNA sequences have been identified so far, genomic computational analysis indicates that as many as 50,000 miRNAs may exist in the human genome, and each may have multiple targets based on similar sequences in the 3'-UTR of mRNA. MiRNAs have been implicated in different areas such as the immune response, neural development, DNA repair, apoptosis, oxidative stress response and others and it is impressive the list of diseases which have recently been found to be associated with abnormal miRNA expression. Here, we focus our attention on the importance of cancer regulator miRNAs. They are divided into oncomiRs and anti-oncomiRs that negatively regulate tumor suppressor genes and oncogenes, respectively. Importantly, the association of miRNAs with cancer has prompted additional functional classification of these short RNAs and their potential relevance in cancer diagnosis, prognosis and treatment.