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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.

Background: MicroRNAs (miRNAs) represent a class of small ( 22 nt), non-codifying RNAs involved in the negative regulation of mRNAs expression. They normally bind the 3' UTR region of mRNAs, either inhibiting translation or promoting mRNA specific degradation. They are involved in the regulation of several cellular processes including proliferation, differentiation, embryonic development and apoptosis. Accumulating evidence indicates a role of miRNAs also in tumorigenesis as it is well known that tumor cells bear a specific and altered pattern of miRNAs expression. Objectives: In an initial attempt, we sought to check the levels of three HPV-associated miRNAs (miR-126, miR-155 and miR-223). We also tested the effect of IFN b treatment on the miRNAs expression and on the putative miRNAs targets expression. Methods: We used primary keratinocytes transformed by both E6 and E7 proteins derived from mucosal or cutaneous HPV (HPV-16 and -38, respectively named K16 and K38). We also used HPV-positive (CaSki, SiHa) or -negative (primary keratinocytes and C33A) cells. MiRNAs expression was checked using a specific TaqMan Small RNA Assay from Applied Biosysthems, mRNAs expression by Sybr-green based RT-PCR and protein expression by Western Blot. Results and Conclusions: Preliminary miRNAs analysis revealed that, if compared to normal keratinocytes, miR-126 and miR-155 are differentially expressed in K16 and K38, being miR-126 under-expressed in K16 and over-expressed in K38; miR-155 is, instead, over-expressed in K16 and under-expressed in K38. Putative miRNA-155 target K-Ras is over-expressed in all HPV positive cells tested, compared to HPV negative C33A squamous carcinoma cell line. IFN b treatment has no effects on K-Ras expression in K16 and, surprisingly, downregulates K-Ras expression in the other HPV positive cells whereas upregulates K-Ras expression in C33A cells. These results indicate a correlation between HPV genotypes and miRNAs expression profiles evidentiating also the ability of the antitumoral agent IFN b to interfere with E6 and/ or E7-induced miRNAs dysregulation.

Interferon regulatory factor 1 (IRF-1) transcription factor binds to DNA sequence elements found in the promoters of type I IFN and IFN-inducible genes. Transient up-regulation of the IRF-1 gene by virus and IFN treatment causes the consequent induction of many IFN-inducible genes involved in cell growth control and apoptosis. We reported recently that IFN-alpha and all-trans retinoic Acid (RA) inhibit the cell proliferation of squamous carcinoma cell line ME-180 by inducing apoptotic cell death. IRF-1 expression correlates with the IFN-alpha-induced apoptosis phenomenon and, surprisingly, with the RA-induced apoptosis phenomenon. To study how these two different ligands cross-talk in the regulation of cellular antitumor responses, the signalling pathways involved in IRF-1 induction were analyzed in RA and/or IFN-alpha-treated ME-180 cells. We provide evidence indicating that RA-induced IRF-1 gene expression is independent of the STAT-1 activation pathway, despite the presence of the IFN-gamma activated sequence element in the gene promoter, but involves nuclear factor-kappa B activation. Thus, here we first describe the activation of nuclear factor-kappa B by both IFN-alpha and RA in the ME-180 cell line. The induced IRF-1 protein is successively able to bind the IFN-stimulated responsive element in the promoter of the target gene 2',5'-oligoadenylate synthetase.

Human papillomaviruses (HPV) constitute a large family of viruses that can be subdivided into mucosal and cutaneous types. Mucosal high-risk HPVs are the aetiological agents of cervical cancer. Certain cutaneous HPVs, also referred as to beta types, were first isolated from patients suffering from a rare autosomal recessive cancer-prone genetic disorder, epidermodysplasia verruciformis (EV), and are consistently detected in non-melanoma skin cancer from EV, immunocompromised and normal individuals. However, a direct role of the beta HPV types in cancer development remains to be proven and the transforming properties of the majority of the cutaneous HPVs have been poorly investigated. One of the best characterized beta HPVs is type 38 which displays transforming properties that can be ascribed to E6 and E7 proteins. Expression of HPV38 E6 and E7 in human keratinocytes or in the skin of transgenic mice induces stabilization of wild type p53. This selectively activates transcription of ?Np73, an isoform of the p53-related protein p73, which in turn inhibits the capacity of p53 to induce the transcription of genes involved in growth suppression and apoptosis. Recently, we have observed that IFN-? inhibits cell proliferation and affects cell cycle in keratinocytes transformed by both mucosal HR-HPV and cutaneous HPVs. In particular, upon long IFN-? treatments, cutaneous HPV38 transformed cells accumulate in G1 phase and undergo senescence. IFN-? appears to induce this senescence process by upregulating the expression of the tumor suppressor PML. Indeed, experiments of gene silencing via specific siRNAs have shown that PML is essential in the execution of senescence program and p53 and p21 pathways appear to be involved. Preliminary results indicate that p53 co-localyzes with IFN-?-induced PML into Nuclear Bodies and that IFN-? affects p53 phosphorylation status targeting p53 transactivating activity of genes involved in cell proliferation control.

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.

Simple Summary This review aims to collect recent studies on the complex relationship between the host innate response to oncogenic viruses (i.e., HPV, HTLV-1, MCPyV, JCPyV, Herpesviruses, HBV, HCV) and tumorigenic processes by focusing mainly on regulatory crosstalks between viral components and the type I IFN system. It is a picture of new mechanisms by which type I IFNs may be affected and, in turn, affect signaling pathways to mediate anti-proliferative and antiviral responses in virus-induced tumorigenic context. Studies on cellular and viral miRNAs machinery, as well as cellular communication and microenvironment modification via classical secretion mechanisms and extracellular vesicle-mediated delivery are described. Abstract Oncogenic viruses favor the development of tumors in mammals by persistent infection and specific cellular pathways modifications by deregulating cell proliferation and inhibiting apoptosis. They counteract the cellular antiviral defense through viral proteins as well as specific cellular effectors involved in virus-induced tumorigenesis. Type I interferons (IFNs) are a family of cytokines critical not only for viral interference but also for their broad range of properties that go beyond the antiviral action. In fact, they can inhibit cell proliferation and modulate differentiation, apoptosis, and migration. However, their principal role is to regulate the development and activity of most effector cells of the innate and adaptive immune responses. Various are the mechanisms by which IFNs exert their effects on immune cells. They can act directly, through IFN receptor triggering, or indirectly by the induction of chemokines, the secretion of further cytokines, or by the stimulation of cells useful for the activation of particular immune cells. All the properties of IFNs are crucial in the host defense against viruses and bacteria, as well as in the immune surveillance against tumors. IFNs may be affected by and, in turn, affect signaling pathways to mediate anti-proliferative and antiviral responses in virus-induced tumorigenic context. New data on cellular and viral microRNAs (miRNAs) machinery, as well as cellular communication and microenvironment modification via classical secretion mechanisms and extracellular vesicles-mediated delivery are reported. Recent research is reviewed on the tumorigenesis induced by specific viruses with RNA or DNA genome, belonging to different families (i.e., HPV, HTLV-1, MCPyV, JCPyV, Herpesviruses, HBV, HCV) and the IFN system involvement.

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.

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.

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.

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.