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Actinic keratosis (AK) is a carcinoma in situ precursor of cutaneous squamous cell carcinoma (cSCC), the second most common cancer affecting the Caucasian population. AK is frequently present in the sun-exposed skin of the elderly population, UV radiation being the main cause of this cancer, and other risk factors contributing to AK incidence. The dysregulation of microRNAs (miRNAs) observed in different cancers leads to an improper expression of miRNA targets involved in several cellular pathways. The TaqMan Array Human MicroRNA Card assay for miRNA expression profiling was performed in pooled AK compared to healthy skin scraping samples from the same patients. Forty-three miRNAs were modulated in the AK samples. The expression of miR-19b (p < 0.05), -31, -34a (p < 0.001), -126, -146a (p < 0.01), -193b, and -222 (p < 0.05) was validated by RT-qPCR. The MirPath tool was used for MiRNA target prediction and enriched pathways. The top DIANA-mirPath pathways regulated by the targets of the 43 miRNAs are TGF-beta signaling, Proteoglycans in cancer, Pathways in cancer, and Adherens junction (7.30 × 10−10 < p < 1.84 × 10−8). Selected genes regulating the KEGG pathways, i.e., TP53, MDM2, CDKN1A, CDK6, and CCND1, were analyzed. MiRNAs modulated in AK regulate different pathways involved in tumorigenesis, indicating miRNA regulation as a critical step in keratinocyte cancer.

Actinic keratosis (AK) arises on photo-damaged skin and is considered to be the precursor lesion of cutaneous squamous cell carcinoma (cSCC). Many findings support the involvement of β human papillomaviruses (HPVs) in cSCC, while very little is known on γ HPV types. The objective of this study was to characterize the spectrum of PV types in healthy skin (HS) and AK samples of the same immunocompetent individuals using next generation sequencing (NGS). Viral DNA of 244 AK and 242 HS specimens were amplified by PCR using two different sets of primers (FAP59/64 and FAPM1). Purified amplicons were pooled and sequenced using NGS. The study resulted in the identification of a large number of known β and γ PV types. In addition, 27 putative novel β and 16 γ and 4 unclassified PVs were isolated. HPV types of species γ-1 (e.g. HPV4) appeared to be strongly enriched in AK versus HS. The NGS analysis revealed that a large spectrum of known and novel PVs is present in HS and AK. The evidence that species γ-1 HPV types appears to be enriched in AK in comparison to HS warrants further studies to evaluate their role in development of skin (pre)cancerous lesions.

Highlights • A group of mucosal HPVs are the causative agents of cervical cancer and are associated to other cancers. • Certain cutaneous HPVs are involved in the development of cutaneous squamous cell carcinoma. • EVs released by HPV+ cells convey a specific cargo of mRNAs and microRNAs. • The EV delivery from HPV+ cells to non-infected recipient cells may represent a novel mechanism of tumorigenesis promotion., A small group of mucosal Human Papillomaviruses are the causative agents of cervical cancer and are also associated with other types of cancers. Certain cutaneous Human Papillomaviruses seem to have a role as co-factors in the UV-induced carcinogenesis of the skin. The main mechanism of the tumorigenesis induced by Human Papillomaviruses is linked to the transforming activity of the viral E6 and E7 oncoproteins. However, other mechanisms, such as the gene expression control by specific microRNAs expression and deregulation of immune inflammatory mediators, may be important in the process of transformation. In this context, the release of Extracellular Vesicles with a specific cargo (microRNAs involved in tumorigenesis, mRNAs of viral oncoproteins, cytokines, chemokines) appears to play a key role.

The connection between chronic inflammation and risk of cancer has been supported by several studies. The development of cancer might be a process driven by the presence of a specific combination of inflammatory mediators, including cytokines, chemokines and enzymes, in the tumor microenvironment. Virus-induced tumors, like HPV-induced Squamous Cell Carcinomas, represent a paradigmatic example of the interplay between inflammation, as integral part of the innate antiviral response, and malignant transformation. Here, the role of inflammatory microenvironment in the HPV-induced carcinogenesis is addressed, with a specific focus on the involvement of the immune molecules as well as their delivery through the microvesicle cargo possibly correlated to the different HPV genotype. The expression of the inflammatory mediators in HPV positive cells has been analyzed in primary human foreskin keratinocytes and keratinocytes transduced by E6 and E7 from mucosal HPV-16 or cutaneous HPV-38 genotypes. HPV E6 and E7 proteins can modulate the expression of immune mediators in HPV-infected cells and can affect the levels of immune molecules, mainly chemokines, in the extracellular milieu. HPV-16 E6 and E7 oncoproteins have been silenced to confirm the specificity of the modulation of the inflammatory microenvironment. Our results suggest that the expression of HPV oncoproteins allows the modification of the tumor milieu through the synthesis and release of specific pro-inflammatory cytokines and chemokines, affecting the efficacy of the immune response. The microenvironment can also be conditioned by an altered mRNA cargo delivered by extracellular vesicles, thereby efficiently affecting the surrounding cells with possible implication for tumorigenesis and tumor diagnosis.

Human Papilloma Viruses (HPVs) are the causative agents of cervical cancer although other types of cancers are associated with HPV infection. Type I Interferons can interfere with HPV E6- and/or E7-dependent transformation and can affect microRNA (miRNA) expression. Cancer cells show a specific pattern of miRNA expression and HPVs are able to modulate miRNAs expressed in infected cells. Keratinocytes transduced with E6 and E7 from mucosal HPV-16 or cutaneous HPV-38 (K16 and K38) were studied to analyze the involvement of HPV oncoproteins in the anti-proliferative activity of IFN-β. In view of our previous data showing senescence induction by the cytokine in K38 cells, we observe that IFN-β treatment leads to p53-indipendent apoptosis in K16 cells whereas induces senescence in K16 cells if E6 is silenced and p53 expression is restored. The levels of selected miRNAs, deregulated in K16 and K38 cells, can be modulated by IFN-β when E6 and E7 proteins of HPV-16, but not HPV-38, are expressed.

More than 15% of the global cancer burden is attributable to infectious agents. Pathogens that cause persistent infections are strongly associated with cancer, inflammation being a major component of the chronic infections as revealed by basic, clinical and epidemiological studies. Persistent infection and viral oncoproteins induce specific cellular pathways modifications that promote tumorigenesis. Deregulated and continuous immune response leads to severe tissue and systemic damage, impaired tumor surveillance and consequent carcinogenesis promotion by selecting for metastatic and therapeutically resistant tumor phenotypes. In this review, the role of inflammatory microenvironment in the HPV-induced carcinogenesis is addressed, with a specific focus on the involvement of the immune molecules and microRNAs as well as their delivery through the microvesicle cargo.

Human papillomaviruses (HPVs) are the causative agents of cervical cancer and are also associated with other types of cancers. HPVs can modulate microRNAs (miRNAs) expressed by infected cells. The production of extracellular vesicles is deregulated in cancer, and their cargo delivered to the microenvironment can promote tumorigenesis. The involvement of HPV oncoproteins on miRNA expression in cells and exosomes was analyzed in keratinocytes transduced with E6 and E7 from mucosal HPV-16 or cutaneous HPV-38 (K16 and K38).MiRNAs were investigated through the TaqMan Array Human MicroRNA Cards, followed by real-time RT-PCR assay for specific miRNAs. Selected miRNA targets were analyzed by Western blot and correlated to the HPV oncoproteins by specifically silencing E6 and E7 expression. Exosomes, isolated from K16 and K38 supernatants by differential centrifugations, were quantified through the vesicle-associated acetylcholinesterase activity.MiRNAs deregulated in K16 and K38 cells were identified. HPV-16 and/or HPV-38 E6 and E7 single proteins can modify the expression of selected miRNAs involved in the tumorigenesis, in particular miR-18a, -19a, -34a and -590-5p. The analysis of the content of exosomes isolated from HPV-positive cells revealed the presence of E6 and E7 mRNAs and few miRNAs. MiR-222, a key miRNA deregulated in many cancers, was identified in exosomes from K16 cells.HPV E6 and/or E7 oncoprotein expression can induce the deregulation of some miRNAs. Through the production and function of exosomes, HPV oncogenes as well as HPV-deregulated miRNAs can potentiate the virus oncogenic effects in the tumor cell microenvironment.

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.

Human immunodeficiency virus (HIV)-1 Nef is a regulatory protein critically involved in AIDS pathogenesis. We previously demonstrated that extracellular Nef is efficiently internalized by human primary monocyte-derived macrophages (MDMs), thereby activating a number of transcription factors including STATs, MAPKs, IRF-3, and NF-kappaB. Such an activation state leads to the release of inflammatory factors whose paracrine effects deserve deep consideration. Here, we demonstrate that quiescent CD4 lymphocytes undergo cell activation when cultivated in supernatants from autologous MDMs treated with extracellular wt Nef but not with its counterpart mutated in the (72)PxxP(75) polyproline domain. Of a pathogenetic relevance, this effect coupled with the sensitization of quiescent CD4 lymphocytes to HIV-1 infection. By microarray assay, we found that the CCL24/eotaxin-2 gene was up-regulated in MDMs treated with wt Nef but not with the (72)AxxA(75) mutant. In addition, the higher transcription activity correlated with a significant increase of the CCL24/Eotaxin-2 release. Finally, we observed that anti-CCL24/eotaxin-2 antibodies efficiently neutralized the stimulatory effect on CD4 lymphocytes of supernatants from MDMs treated with extracellular Nef. Overall, these data support the idea that CCL24/eotaxin-2 is part of the mechanism of CD4 lymphocyte activation paracrinally induced by Nef.

The inception of tumor microenvironment (TME), a complex and dynamic system constituted by different types of cells engaged by tumor and extracellular matrix surrounding cancer cells, is a way for them to elude the immune surveillance. Dendritic cells (DCs), as a sentinel, are able to recognize alteration in the microenvironment and predispose the immune system response. The relationship between cancer and virus infection is well documented. High-risk Human Papillomavirus (HR-HPV) has a well-characterized transforming property and has been associated with squamous cell carcinoma of the ano-genital and oral tracts. Transforming ability of HR-HPVs is based on the function of E6 and E7 viral oncoproteins, which interact and inactivate p53 and pRb oncosuppressors, respectively. Recently, it was demonstrated that HPV oncoproteins are also able to affect a number of microRNAs (miRNAs) regulating the expression of genes involved in proliferative control. For these reasons DC-based vaccines targeting oncogenic E6 and E7 are ideal candidates to elicit strong immune responses. Here we summarize significant data about the analysis of TME in HPV-induced tumorigenesis. We also report original results produced by cytotoxic T lymphocyte (CTL) in vitro priming against E6 and E7 HPV16 antigens, performed using human monocyte-derived dendritic cells. Dendritic cells, maturated by the exposition to necrotic or apoptotic keratinocytes expressing both oncoproteins of HPV16, show different expression levels of specific maturation markers. Evidence indicating the ability of necrotic keratinocytes to alter the microRNA profile in DCs, macrophages (MΦ) and Langerhans cells (LCs) compared to prototypical stimuli as bacterial lipopolysaccharide was also provided. We can speculate that, based on transformed cells death pathway (i.e. apoptosis versus necrosis), virus-induced immune alterations might show different results in creating an immunotolerogenic microenvironment during the carcinogenesis process.

Background The potential role of the human immunodeficiency virus-1 (HIV-1) accessory protein Nef in the pathogenesis of neuroAIDS is still poorly understood. Nef is a molecular adapter that influences several cellular signal transduction events and membrane trafficking. In human macrophages, Nef expression induces the production of extracellular factors (e.g. pro-inflammatory chemokines and cytokines) and the recruitment of T cells, thus favoring their infection and its own transfer to uninfected cells via exosomes, cellular protrusions or cell-to-cell contacts. Murine cells are normally not permissive for HIV-1 but, in transgenic mice, Nef is a major disease determinant. Both in human and murine macrophages, myristoylated Nef (myr+Nef) treatment has been shown to activate NF-κB, MAP kinases and interferon responsive factor 3 (IRF-3), thereby inducing tyrosine phosphorylation of signal transducers and activator of transcription (STAT)-1, STAT-2 and STAT-3 through the production of proinflammatory factors. Methodology/Principal Findings We report that treatment of BV-2 murine microglial cells with myr+Nef leads to STAT-1, -2 and -3 tyrosine phosphorylation and upregulates the expression of inducible nitric oxide synthase (iNOS) with production of nitric oxide. We provide evidence that extracellular Nef regulates iNOS expression through NF-κB activation and, at least in part, interferon-β (IFNβ) release that acts in concert with Nef. All of these effects require both myristoylation and a highly conserved acidic cluster in the viral protein. Finally, we report that Nef induces the release of neurotoxic factors in the supernatants of microglial cells. Conclusions These results suggest a potential role of extracellular Nef in promoting neuronal injury in the murine model. They also indicate a possible interplay between Nef and host factors in the pathogenesis of neuroAIDS through the production of reactive nitrogen species in microglial cells.

1. Introduction Several lymphotropic viruses manipulate host innate immune response to escape immune recognition and improve viral replication and spreading. From this point of view HIV (Human Immunodeficiency Virus-1) represents a paradigmatic example (for review see Peterlin & Trono, 2003). HIV-1 encodes the classical structural and enzymatic factors of all retroviruses codified from the gag (group-specific antigen), pol (polymerase) and env (envelope) genes. In addition it codes two regulatory proteins that are essential for viral replication (i.e., the transcriptional transactivator Tat and the regulator of virion gene expression Rev) and four accessory proteins (i.e., the ill-named ‘negative effector’ Nef, the viral infectivity factor Vif, the viral protein r Vpr and the viral protein u Vpu). With time has become increasingly clear that the so-called accessory proteins carry out several critical functions for both viral replication and pathogenesis (Malim & Emerman, 2008). In particular, the Nef protein was demonstrated to be an important virulence factor of primate lentiviruses. In fact Nef-defective HIV leads to an attenuated clinical phenotype with reduced viral loads in mouse models, monkeys, and in human disease (Daniel et al., 1992; Deacon et al., 1995; Gulizia et al., 1997; Kestler et al., 1991; Kirchhoff et al., 1995) and nef transgenic mice develop an AIDS-like disease (Hanna et al., 1998) confirming that this viral protein is a major determinant of pathogenicity. Studies on structure and mechanism of action of the protein highlighted its multifunctional properties at cellular and molecular level. The open reading frame encoding Nef is located 3′ of the env gene, overlaps the untranslated sequences of the 3′ viral long terminal repeat and is translated from multiply spliced transcripts. Nef is expressed early and most abundantly during the infection cycle together with Tat and Rev and evidences have been reported of possible expression also before integration of the proviral genome (Wu & Marsh, 2001). It acts as a molecular adaptor inside the cell inducing genetically distinguishable, yet highly HIV-Host Interactions 62 conserved, effects via specific protein-protein interaction motifs (Arold & Baur, 2001; Doms & Trono, 2000; Geyer et al., 2001, Foster et al., 2011). In general, Nefs from all primate lentiviruses (i.e. HIV-1, HIV-2, and SIV) share multiple activities in vitro, but differences between the ability of human and simian immunodeficiency viruses to induce Nef-mediated internalization of the CD3 component of the T-cell receptor complex have been observed and have been correlated with the greater pathogenicity of HIV and the reduction of T-cell activation in simian immunodeficiency virus (SIV) (Schindler et al., 2006). It has been also observed that HIV-1 Nef treatment of uninfected cells in culture causes internalization of the protein in some cell types and/or activates specific intracellular signalling pathways. Interestingly, Nef has been found inside uninfected B cells of lymphoid follicles from infected individuals (Qiao et al., 2006) and recently it has been provided experimental evidencies that it can be transferred to uninfected cells from the infected ones via cellular protrusions and/or exosomes (Lenassi et al., 2010; Muratori et al., 2009; Xu et al., 2009) opening a new road to deepen our insight on the roles of this multifunctional protein. This review will focus on those recent observations trying to provide a unifying reading.

Numerous evidence has demonstrated the involvement in growth control of interferon (IFN) regulatory factor-1 (IRF-1), which shows tumor suppressor activity. IRF-1 is a well-studied member of the IRF transcription factors that reveals functional diversity in the regulation of cellular response by activating expression of a diverse set of target genes, depending on the cell type and on the specific stimuli. IRF-1 gene rearrangements may be a crucial point in the pathogenesis of some cancer types. Furthermore, different aspects of the tumor suppressor function of IRF-1 may be explained, at least in part, by the observations that IRF-1 is a regulator of cell cycle and apoptosis and that its inactivation accelerates cell transformation. Studies on gene knockout mice contributed greatly to the clarification of these multiple IRF-1 functions. We summarize our current knowledge of the antigrowth effect of IRF-1, focusing also on a more general involvement of IRF-1 in mediating negative regulation of cell growth induced by numerous cytokines and other biologic response modifiers.

Numerous microRNAs (miRNAs), small non-coding RNAs encoded in the human genome, have been shown to be involved in cancer pathogenesis and progression. There is evidence that some of these miRNAs possess proapoptotic or proliferation promoting roles in the cell by negatively regulating target mRNAs. Oncogenic viruses are able to produce persistent infection, favoring tumor development by deregulating cell proliferation and inhibiting apoptosis. It has been recently suggested that cellular miRNAs may participate in host–virus interactions, influencing viral replication. Many mammalian viruses counteract this cellular antiviral defense by using viral proteins but also by encoding viral miRNAs involved in virus-induced tumorigenesis. Interferons (IFNs) modulate a number of non-coding RNA genes, especially miRNAs, that may be used by mammalian organisms as a mechanism of IFN system to combat viral infection and related diseases. In particular, IFNs might induce specific cellular miRNAs that target viral transcripts thereby using this strategy as part of their effectiveness against invading viruses. Therefore IFNs, interferon stimulated genes and miRNAs could act synergistically as innate response to virus infection to induce a potent non-permissive cellular environment for virus replication and virus-induced cancer. The relevance of this reviewed research topic is clearly related to the observation that although virus infections are responsible of specific tumors, other unidentified genetic alterations are likely involved in the induction of malignant transformation. The identification of such genetic alterations, i.e. miRNA expression in transformed cells, would be of considerable importance for the analysis of the pathogenesis and for the treatment of cancer induced by specific viruses as well as for the advancement of the current knowledge on the molecular mechanisms underlying virus–host interaction. In this respect, we will review also the important, still little explored, roles of miRNAs acting both as IFN-stimulated anti-viral molecules and as critical regulators of IFNs and IFN-stimulated genes.

Several lines of evidence have demonstrated that IFNs could be relevant in the treatment of certain neoplastic diseases such as carcinomas. In particular, IFN-α, in addition to the anti-proliferative and cytostatic effects, was demonstrated to be capable of inducing cell death by apoptosis both in vivo and in vitro. Numerous protocols have also been proposed which consider the association of IFN-α with other drugs. Among these are retinoids, a class of compounds capable of inducing inhibition of cell growth and differentiation. We address the question here by analyzing the role of cell adhesion in susceptibility to IFN-α, RA and their combination of a human cell line derived from a squamous carcinoma of the cervix, the Bcl-2-negative SiHa cell line. In this context, cytoskeleton components and several surface molecules playing a role in cell substrate and cell-to-cell relationships have been evaluated. We found that RA treatment is capable of improving stress fiber formation, decreasing cell detachment and increasing cell-adhesion capability. However, no variations in the ability to adhere to specific extracellular-matrix molecules were found in RA-treated cells. No quantitative changes were detected in integrins involved as receptors for extracellular matrix molecules (VLA1-VLA5) or in other cell-adhesion-associated molecules (e.g., CD44). By contrast, 2 important molecules involved in cell-adhesion processes appeared to be up-regulated by RA exposure: focal adhesion kinase and E-cadherin, involved in adhesion plaque formation and cell-to-cell contacts, respectively. Keeping in mind the importance of adhesion properties in the cell-growth pathway, our findings could be of interest in the study of carcinoma-cell proliferation and metastatic potential. Int. J. Cancer 76:531–540, 1998.© 1998 Wiley-Liss, Inc.

""Background: HIV-1 Nef is a virulence factor that plays multiple roles during HIV replication. Recently, it has been described. that Nef intersects the CD40 signalling in macrophages, leading to modification in the pattern of secreted factors that. appear able to recruit, activate and render T lymphocytes susceptible to HIV infection. The engagement of CD40 by CD40L. induces the activation of different signalling cascades that require the recruitment of specific tumor necrosis factor. receptor-associated factors (i.e. TRAFs). We hypothesized that TRAFs might be involved in the rapid activation of NF-kB,. MAPKs and IRF-3 that were previously described in Nef-treated macrophages to induce the synthesis and secretion of. proinflammatory cytokines, chemokines and IFNbeta to activate STAT1, -2 and -3.. Methodology\\\/Principal Findings: Searching for possible TRAF binding sites on Nef, we found a TRAF2 consensus binding. site in the AQEEEE sequence encompassing the conserved four-glutamate acidic cluster. Here we show that all the. signalling effects we observed in Nef treated macrophages depend on the integrity of the acidic cluster. In addition, Nef was. able to interact in vitro with TRAF2, but not TRAF6, and this interaction involved the acidic cluster. Finally silencing. experiments in THP-1 monocytic cells indicate that both TRAF2 and, surprisingly, TRAF6 are required for the Nef-induced. tyrosine phosphorylation of STAT1 and STAT2.. Conclusions: Results reported here revealed TRAF2 as a new possible cellular interactor of Nef and highlighted that in. monocytes\\\/macrophages this viral protein is able to manipulate both the TRAF\\\/NF-kB and TRAF\\\/IRF-3 signalling axes,. thereby inducing the synthesis of proinflammatory cytokines and chemokines as well as IFNbeta.""

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.

The induction of transcription of the 2'-5'-oligoadenylate (2-5A) synthetase gene by type I (alpha/beta) and type II (gamma) interferons (IFNs) has been studied in wild-type (w.t.) and IFN-resistant Friend leukemia cells (FLC). Following IFN treatment, new complexes are formed in vitro between the IFN-responsive sequence (IRS) of the 2-5A synthetase gene and cellular proteins. Within minutes after IFN-alpha/beta addition to w.t. FLC, an IRS-protein complex, designated F1, is detected, as already observed in several human cell lines. In response to IFN-gamma, a novel complex, designated Fg, is observed in w.t. FLC. The Fg complex appears within 3 h, while an F1-like complex is faintly visible 10 to 24 h later. In the IFN-alpha/beta-resistant FLC, IFN-gamma induces only the Fg complex and fails to induce F1. Fg formation is correlated with the IFN-gamma-induced transcription of the 2-5A synthetase gene and the appearance of the corresponding enzymatic activity in both w.t. and IFN-alpha/beta-resistant FLC. These findings suggest that F1 and Fg represent two distinct effector complexes by which type I and type II IFNs, respectively, induce 2-5A synthetase.

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.

Inflammation is a critical component of tumorigenesis. Tumor microenvironment participates in the neoplastic process fostering proliferation, survival and migration. Virus-induced tumors, like HPV-induced Squamous Cell Carcinomas, represent a paradigmatic example of the interplay between inflammation, as integral part of the innate antiviral response, and malignant transformation. To study the tumorigenic role of inflammatory mediators in HPV + cells, we analyzed by real time RT-PCR the expression of selected inflammatory cytokines, chemokines and related molecules in human foreskin keratinocytes transduced by E6 and E7 from mucosalHPV-16 (K16) or cutaneousHPV-38 (K38) genotypes comparing them to primary Human Foreskin Keratinocytes. We also performed silencing experiments by using E6/E7 siRNA in HPV + SiHa carcinoma cells to verify the involvement of the viral proteins. IL-1 α and IL-1 β mRNAs are downregulated in K16 and K38 cells, whereas IL-1R1 mRNA level is comparable in all cell lines. IL-6 mRNA level is unchanged in K16 and downregulated in K38. E6/E7 silencing in SiHa confirms the effect specificity. MIP-3 α , CCL-17 and CCl-22 mRNA levels in K16 cells are also deregulated. Deregulation of MIP-3 α mRNA appears to be related to miR-21 over-expression detected in both K16 and K38. The effect of the IFN- β on the levels of these pro-inflammatory mediators will be also discussed. Experiments on paraffin embedded tissues are in progress to verify MIP-3 α deregulation in vivo. Our results suggest that HPV is able to modify the tumor microenvironment through the synthesis and release of specific pro-inflammatory cytokines and chemokines possibly to interfere with the leucocytes trafficking and/or allowing a better tumor growth and infiltration.

Interferon (IFN)-beta induces S-phase slowing and apoptosis in human papilloma virus (HPV)-positive cervical carcinoma cell line ME-180. Here, we show that apoptosis is a consequence of the S-phase lengthening imposed by IFN-beta, demonstrating the functional correlation between S-phase alteration and apoptosis induction. In ME-180 cells, where p53 function is inhibited by HPV E6 oncoprotein, IFN-beta effects on cell cycle and apoptosis occur independently of p53. The apoptosis due to IFN-beta is mediated by the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in a manner dependent on the S-phase deregulation. IFN-beta appears to increase TRAIL expression both directly at the mRNA level and indirectly by augmenting surface protein levels as a consequence of the induced S-phase cell accumulation. Moreover, the alteration of the S-phase due to IFN-beta promotes TRAIL-dependent apoptosis by potentiating cell sensitivity to TRAIL, possibly through induction of a proapoptotic NF-kappaB activity and TRAIL-R2 receptor expression. Interestingly, IFN-beta-induced TRAIL-dependent apoptotic events strongly differ in the requirement of caspase activity. These results show that IFN-beta may induce an apoptotic response by deregulating cell cycle. Understanding the linkage between these mechanisms appears to be of primary importance in the search for new IFN-based therapeutic strategies to circumvent cancer disease or improve clinical outcome.

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.

Increasing evidence indicates that the expression of the human immunodeficiency virus-1 (HIV-1) Nef protein significantly influences the activation state of the host cell. Here we report that Nef specifically activates STAT3 in primary human monocyte-derived macrophages (MDM). This was demonstrated by both single-cycle infection experiments driven by Vesicular Stomatitis virus glycoprotein (VSV-G) pseudotyped HIV-1 and treatment with exogenous recombinant Nef. The analysis of the effects of Nef mutants revealed that domains of the C-terminal flexible loop interacting with the cell endocytotic machinery are involved in the STAT3 activation. In particular, our data suggest that the Nef-dependent STAT3 activation relies on the targeting of Nef to the late endosome/lysosome compartment. In addition, we found that Nef activates STAT3 through a mechanism mediated by the release of soluble factor(s), including MIP-1α, that requires de novo protein synthesis but appears independent from the activation of src tyrosine kinases. The results presented here support the idea that the first intervention of Nef in the intracellular signaling of monocyte-macrophages could generate, by means of the release of soluble factor(s), a secondary wave of activation that could be of a potential pathogenetic significance.

Monocytes/macrophages play a predominant role in the immunologic network by secreting and reacting to a wide range of soluble factors. Human immunodeficiency virus (HIV) infection leads to deep immunologic dysfunctions, also as a consequence of alterations in the pattern of cytokine release. Recent studies on in vivo models demonstrated that the expression of HIV Nef alone mimics many pathogenetic effects of HIV infection. In particular, Nef expression in monocytes/macrophages has been correlated with remarkable modifications in the pattern of secreted soluble factors, suggesting that the interaction of Nef with monocytes/macrophages plays a role in the pathogenesis of acquired immunodeficiency syndrome (AIDS). This study sought to define possible alterations in intracellular signaling induced by Nef in monocytes/macrophages. Results demonstrate that HIV-1 Nef specifically activates both α and β isoforms of the signal transducer and activator of transcription 1 (STAT1). This was observed both by infecting human monocyte-derived macrophages (MDMs) with HIV-1 deletion mutants, and by exploiting the ability of MDMs to internalize soluble, recombinant Nef protein (rNef). STAT1-α activation occurs on phosphorylation of both C-terminal Tyr701 and Ser727 and leads to a strong binding activity. Nef-dependent STAT1 activation is followed by increased expression of both STAT1 and interferon regulatory factor-1, a transcription factor transcriptionally regulated by STAT1 activation. It was also established that Nef-induced STAT1- α/β activation occurs through the secretion of soluble factors. Taken together, the results indicate that HIV-1 Nef could interfere with STAT1-governed intracellular signaling in human monocytes/macrophages.

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.

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.

The clear involvement of the interferon (IFN) system in the regulation of differentiation justifies the advanced IFN clinical trials in “differentiation therapy” of cancer. By employing this strategy, it may be possible to specifically reprogram the phenotype of a tumor cell by inducing its terminal cell differentiation and, thus, the loss of its tumorigenic potential. The effects of IFNs on erythroid differentiation and the related mechanisms are reported. Administration of highly purified preparations of murine IFN-alpha or -beta to Friend leukemia cells, induced to differentiate by dimethyl-sulfoxide, leads to a 100% increase of benzidine-positive cells. Both species of IFN induce a substantial increase in heme, hemoglobin and transferrin receptor levels. The results obtained suggest that in erythroid cells the intracellular heme level may represent a key regulatory factor in the hemoglobin synthesis pathway. It is postulated that IFN induces the enhancing effect on differentiation via a marked increase of heme synthesis and number of transferrin receptors which in turn leads to an enhancement of globin chain synthesis.

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.

Administration of highly purified preparations of murine interferon (IFN)-alpha 1, -alpha 4, -alpha 6, or -beta to Friend leukemia cells induced to differentiate by dimethyl sulfoxide leads to a 100% increase of benzidine-positive (B+) cells. Different efficiencies for the two IFN species have been observed; a 10-fold higher dose of IFN-alpha is needed for stimulation of hemoglobin production and inhibition of cell growth as compared with IFN-beta. Both species of IFN induce a substantial increase in heme, hemoglobin, and transferrin receptor levels. In vitro run-on transcription assays indicate that IFN-beta moderately stimulates transcription of the alpha-globin gene but not the transferrin receptor gene. It is postulated that IFN induces the enhancing effect on differentiation via a marked increase of heme synthesis and number of transferrin receptors, which in turn leads to an enhancement of globin chain synthesis. In this regard, the negative feedback reported in a variety of other cell types for the regulation of transferrin receptor expression by heme does not seem to be operative in maturing Friend erythroleukemia cells, which present evidence for a positive mechanism.

Interferons (IFNs), besides inducing an antiviral state in uninfected cells, are also natural regulatory molecules. They play a key role in the regulation both of cell growth and differentiation, and of development. Up-or down-regulation of oncogenes by IFNs may be one of the mechanisms by which these molecules affect cell physiology. The list of IFN-inducible proteins continues to grow rapidly and future research should identify among these the mediators of the biological effects of IFNs.

The effect of succinylacetone (SA), a highly specific inhibitor of ALA- dehydratase and heme synthesis, on hemoglobin (Hb) production, transferrin receptor (TfR), and ferritin expression was analyzed in differentiating Friend leukemia cells (FLC). This compound exerted a pronounced inhibitory effect not only on heme and Hb synthesis, but also on all the remaining above-mentioned parameters. In particular, SA induced: (1) a reduction of the level of alpha-globin mRNA; (2) a decreased number of exposed TfR molecules, without modification of their affinity for the ligand; (3) a reduced level of TfR RNA, without significant change of TfR gene transcription rate; and (4) a lower ferritin content. The addition of exogenous hemin to differentiating FLC exerted opposite effects, and particularly induced an increase of both the number of TfRs and ferritin content. These findings suggest that in erythroid cells optimal heme synthesis is required to coordinately sustain globin chains synthesis and TfR/ferritin production; thus, the intracellular heme level may represent a key regulatory factor in the Hb synthesis pathway.

Treatment of cells with interferons (IFNs) induces resistance to virus infection. The 2′-5′oligo A (2-5A) synthetase/RNase L is one of the pathways leading to translation inhibition induced by IFN treatment. A murine cDNA encoding the 43-kDa 2-5A synthetase was cloned and sequenced. NIH-3T3 cell clones transfected with this cDNA expressed the enzymatic activity to various extents and exhibited resistance to encephalomyocarditis virus (EMCV) but not to vesicular stomatitis virus replication. The specific resistance to EMCV can be attributed to 2-5A synthetase.

Interferons (IFNs), besides inducing an antiviral state in uninfected cells, are also natural regulatory molecules. They play a key role in the regulation both of cell growth and differentiation, and of development. Up- or down-regulation of oncogenes by IFNs may be one of the mechanisms by which these molecules affect cell physiology. The list of IFN-inducible proteins continues to grow rapidly and future research should identify among these the mediators of the biological effects of IFNs.

The replication of Friend Leukemia virus (FLV) has been investigated in adhesive clones (FF) of Friend Leukemia cells which were selected via cultivation on top of human fibroblast monolayers. In these adhesive clones a shut-down of FLV production is observed under conditions of culture confluency; this finding is not due either to a reduced number of cell divisions nor to a defective expression of FLV genome as assessed by Northern blot and immunofluorescence studies. Ultrastructural studies showed that virus budding and release into the medium is not detectable under these conditions. Conversely, in confluent FF cell monolayers abundant imperfect type-A enveloped particles were visible, possibly originating from stacks of granular endoplasmic reticulum with thickened membranes. It is postulated that the reduced virus production in adhesive FF monolayers is due to as yet undetermined events taking place during virus maturation at a time coincident with that of cell-cell adhesion under conditions of culture confluency.