Induction of Immune-Stimulating Factors and Oncolysis Upon p14ARF Gene Transfer in Melanoma Cell Lines.

Together with an anti-tumor immune response, oncolysis using a recombinant viral vector promises to eliminate cancer cells by both gene transfer and host-mediated functions. In this study we explore oncolysis induced by nonreplicating adenoviral vectors used for p14ARF and interferon-ß (hIFNß) gene transfer in human melanoma cell lines, revealing an unexpected role for p14ARF in promoting cellular responses predictive of immune stimulation. Oncolysis was confirmed when UACC-62 (p53 wild-type) cells succumbed upon p14ARF gene transfer in vitro, whereas SK-Mel-29 (p53-mutant) benefitted from its combination with hIFNß. In the case of UACC-62, in situ gene therapy in nude mice yielded reduced tumor progression in response to the p14ARF and hIFNß combination. Potential for immune stimulation was revealed where p14ARF gene transfer in vitro was sufficient to induce emission of immunogenic cell death factors in UACC-62 and upregulate pro-immune genes, including IRF1, IRF7, IRF9, ISG15, TAP-1, and B2M. In SK-Mel-29, p14ARF gene transfer induced a subset of these factors. hIFNß was, as expected, sufficient to induce these immune-stimulating genes in both cell lines. This work is a significant advancement for our melanoma gene therapy strategy because we revealed not only the induction of oncolysis, but also the potential contribution of p14ARF to immune stimulation.

Potentiation of combined p19Arf and interferon-beta cancer gene therapy through its association with doxorubicin chemotherapy.

Balancing safety and efficacy is a major consideration for cancer treatments, especially when combining cancer immunotherapy with other treatment modalities such as chemotherapy. Approaches that induce immunogenic cell death (ICD) are expected to eliminate cancer cells by direct cell killing as well as activation of an antitumor immune response. We have developed a gene therapy approach based on p19Arf and interferon-ß gene transfer that, similar to conventional inducers of ICD, results in the release of DAMPS and immune activation. Here, aiming to potentiate this response, we explore whether association between our approach and treatment with doxorubicin (Dox), a known inducer of ICD, could further potentiate treatment efficacy without inducing cardiotoxicity, a critical side effect of Dox. Using central composite rotational design analysis, we show that cooperation between gene transfer and chemotherapy killed MCA205 and B16F10 cells and permitted the application of reduced viral and drug doses. The treatments also cooperated to induce elevated levels of ICD markers in MCA205, which correlated with improved efficacy of immunotherapy in vivo. Treatment of subcutaneous MCA205 tumors associating gene transfer and low dose (10 mg/kg) chemotherapy resulted in inhibition of tumor progression. Moreover, the reduced dose did not cause cardiotoxicity as compared to the therapeutic dose of Dox (20 mg/kg). The association of p19Arf/interferon-ß gene transfer and Dox chemotherapy potentiated antitumor response and minimized cardiotoxicity.

Exploration of p53 plus interferon-beta gene transfer for the sensitization of human colorectal cancer cell lines to cell death.

While treatments for colorectal cancer continue to improve, some 50% of patients succumb within 5 years, pointing to the need for additional therapeutic options. We have developed a modified non-replicating adenoviral vector for gene transfer, called AdRGD-PG, which offers improved levels of transduction and transgene expression. Here, we employ the p53-responsive PG promoter to drive expression of p53 or human interferon-ß (hIFNß) in human colorectal cancer cell lines HCT116wt (wtp53), HCT116-/- (p53 deficient) and HT29 (mutant p53). The HCT116 cell lines were both easily killed with p53 gene transfer, while combined p53 and hIFNß cooperated for the induction of HT29 cell death and emission of immunogenic cell death (ICD) markers. Elevated annexinV staining and caspase 3/7 activity point to cell death by a mechanism consistent with apoptosis. P53 gene transfer alone or in combination with hIFNß sensitized all cell lines to chemotherapy, permitting the application of low drug doses while still achieving significant loss of viability. While endogenous p53 status was not sufficient to predict response to treatment, combined p53 and hIFNß provided an additive effect in HT29 cells. We propose that this approach may prove effective for the treatment of colorectal cancer, permitting the use of limited drug doses.

miR-138-5p induces aggressive traits by targeting Trp53 expression in murine melanoma cells, and correlates with poor prognosis of melanoma patients.

Deregulation of miRNAs contributes to the development of distinct cancer types, including melanoma, an aggressive form of skin cancer characterized by high metastatic potential and poor prognosis. The expression of a set of 580 miRNAs was investigated in a model of murine melanoma progression, comprising non-metastatic (4C11-) and metastatic melanoma (4C11+) cells. A significant increase in miR-138-5p expression was found in the metastatic 4C11+ melanoma cells compared to 4C11-, which prompted us to investigate its role in melanoma aggressiveness. Functional assays, including anoikis resistance, colony formation, collective migration, serum-deprived growth capacity, as well as in vivo tumor growth and experimental metastasis were performed in 4C11- cells stably overexpressing miR-138-5p. miR-138-5p induced an aggressive phenotype in mouse melanoma cell lines leading to increased proliferation, migration and cell viability under stress conditions. Moreover, by overexpressing miR-138-5p, low-growing and non-metastatic 4C11- cells became highly proliferative and metastatic in vivo, similar to the metastatic 4C11+ cells. Luciferase reporter analysis identified the tumor suppressor Trp53 as a direct target of miR-138-5p. Using data sets from independent melanoma cohorts, miR-138-5p and P53 expression were also found deregulated in human melanoma samples, with their levels negatively and positively correlated with prognosis, respectively. Our data shows that the overexpression of miR-138-5p contributes to melanoma metastasis through the direct suppression of Trp53.

Response of human melanoma cell lines to interferon-beta gene transfer mediated by a modified adenoviral vector.

Since melanomas often retain wild type p53, we developed an adenoviral vector, AdRGD-PG, which provides robust transduction and transgene expression in response to p53. Previously, this vector was used for interferon-ß gene transfer in mouse models of melanoma, resulting in control of tumor progression, but limited cell killing. Here, the AdRGD-PG-hIFNß vector encoding the human interferon-ß cDNA (hIFNß) was used to transduce human melanoma cell lines SK-MEL-05 and SK-MEL-147 (both wild type p53). In vitro, cell death was induced in more than 80% of the cells and correlated with elevated annexinV staining and caspase 3/7 activity. Treatment with hIFNß promoted cell killing in neighboring, non-transduced cells, thus revealing a bystander effect. In situ gene therapy resulted in complete inhibition of tumor progression for SK-MEL-147 when using nude mice with no evidence of hepatotoxicity. However, the response in Nod-Scid mice was less robust. For SK-MEL-05, tumor inhibition was similar in nude and Nod-Scid mice and was less efficient than seen for SK-MEL-147, indicating both cell type and host specific responses. The AdRGD-PG-hIFNß vector provides extensive killing of human melanoma cells in vitro and a potent anti-tumor effect in vivo. This study provides a critical advance in the development of our melanoma gene therapy approach.

Distinct Roles of Direct Transduction Versus Exposure to the Tumor Secretome on Murine Endothelial Cells After Melanoma Gene Therapy with Interferon-ß and p19Arf.

Tumor vasculature plays a central role in tumor progression, making it an attractive therapeutic target. In this study, we explore the antiangiogenic potential of our melanoma gene therapy approach combining interferon ß (IFNß) and p19Arf gene transfer. Since these proteins are modulators of tumor vasculature, we explore the impact of IFNß and p19Arf gene transfer on murine endothelial cells (tEnd). Adenovirus-mediated gene transfer of p19Arf to tEnd cells inhibited proliferation, tube formation, migration, and led to increased expression of genes related to the p53 cell death pathway, yet IFNß gene transfer had no significant impact on tEnd viability. Alternatively, tEnd cells were exposed to the factors generated by transduced B16 (mouse melanoma) cells using either coculture or conditioned medium. In either case, transduction of B16 cells with the IFNß vector, whether alone or in combination with p19Arf, resulted in endothelial cell death. Strikingly, treatment of tEnd cells with recombinant IFNß did not induce death, demonstrating that additional factors produced by B16 cells contributed to the demise of tEnd cells. In this work, we have shown that our melanoma gene therapy strategy produces desirable negative effects on endothelial cells, possibly correlating with antiangiogenic activity.

Induction of Oxidants Distinguishes Susceptibility of Prostate Carcinoma Cell Lines to p53 Gene Transfer Mediated by an Improved Adenoviral Vector.

Previously, the authors developed an adenoviral vector, Ad-PG, where transgene expression is regulated by a p53-responsive promoter. When used to transfer the p53 cDNA, a positive feedback mechanism is established. In the present study, a critical comparison is performed between Ad-PGp53 and AdRGD-PGp53, where the RGD motif was incorporated in the adenoviral fiber protein. AdRGD-PGp53 provided superior transgene expression levels and resulted in the killing of prostate carcinoma cell lines DU145 and PC3. In vitro, this effect was associated with increased production of cytoplasmic and mitochondrial oxidants, DNA damage as revealed by detection of phosphorylated H2AX, as well as cell death consistent with apoptosis. Differential gene expression of key mediators of reactive oxygen species pathways was also observed. Specifically, it was noted that induction of known p53-target genes Sestrin2 and PIG3, as well as a novel target, NOX1, occurred in PC3 cells only when transduced with the improved vector, AdRGD-PGp53. The participation of NOX1 was confirmed upon its inhibition using a specific peptide, resulting in reduced cell death. In situ gene therapy also resulted in significantly improved inhibition of tumor progression consistent with oxidant-induced DNA damage only when treated with the novel AdRGD-PGp53 vector. The study shows that the improved adenovirus overcomes limitations associated with other p53-expressing vectors and induces oxidant-mediating killing, thus supporting its further development for cancer gene therapy.

Timp1 Promotes Cell Survival by Activating the PDK1 Signaling Pathway in Melanoma.

High TIMP1 expression is associated with poor prognosis in melanoma, where it can bind to CD63 and ß1 integrin, inducing PI3-kinase pathway and cell survival. Phosphatidylinositol (3,4,5)-trisphosphate (PIP3), generated under phosphatidylinositol-3-kinase (PI3K) activation, enables the recruitment and activation of protein kinase B (PKB/AKT) and phosphoinositide-dependent kinase 1 (PDK1) at the membrane, resulting in the phosphorylation of a host of other proteins. Using a melanoma progression model, we evaluated the impact of Timp1 and AKT silencing, as well as PI3K, PDK1, and protein kinase C (PKC) inhibitors on aggressiveness characteristics. Timp1 downregulation resulted in decreased anoikis resistance, clonogenicity, dacarbazine resistance, and in vivo tumor growth and lung colonization. In metastatic cells, pAKTThr308 is highly expressed, contributing to anoikis resistance. We showed that PDK1Ser241 and PKCßIISer660 are activated by Timp1 in different stages of melanoma progression, contributing to colony formation and anoikis resistance. Moreover, simultaneous inhibition of Timp1 and AKT in metastatic cells resulted in more effective anoikis inhibition. Our findings demonstrate that Timp1 promotes cell survival with the participation of PDK1 and PKC in melanoma. In addition, Timp1 and AKT act synergistically to confer anoikis resistance in advanced tumor stages. This study brings new insights about the mechanisms by which Timp1 promotes cell survival in melanoma, and points to novel perspectives for therapeutic approaches.

Immunomodulatory and antitumor effects of type I interferons and their application in cancer therapy.

During the last decades, the pleiotropic antitumor functions exerted by type I interferons (IFNs) have become universally acknowledged, especially their role in mediating interactions between the tumor and the immune system. Indeed, type I IFNs are now appreciated as a critical component of dendritic cell (DC) driven T cell responses to cancer. Here we focus on IFN-α and IFN-ß, and their antitumor effects, impact on immune responses and their use as therapeutic agents. IFN-α/ß share many properties, including activation of the JAK-STAT signaling pathway and induction of a variety of cellular phenotypes. For example, type I IFNs drive not only the high maturation status of DCs, but also have a direct impact in cytotoxic T lymphocytes, NK cell activation, induction of tumor cell death and inhibition of angiogenesis. A variety of stimuli, including some standard cancer treatments, promote the expression of endogenous IFN-α/ß, which then participates as a fundamental component of immunogenic cell death. Systemic treatment with recombinant protein has been used for the treatment of melanoma. The induction of endogenous IFN-α/ß has been tested, including stimulation through pattern recognition receptors. Gene therapies involving IFN-α/ß have also been described. Thus, harnessing type I IFNs as an effective tool for cancer therapy continues to be studied.

Uncovering the immunotherapeutic cycle initiated by p19Arf and interferon-ß gene transfer to cancer cells: An inducer of immunogenic cell death.

Simultaneous reestablishment of p53/p19Arf and interferon-ß pathways in melanoma cells culminates in a cell death process that displays features of necroptosis along with the release of immunogenic cell death molecules and unleashes an antitumor immune response mediated by natural killer cells, neutrophils as well as CD4+ and CD8+ T lymphocytes.

Intratumoral Immunization by p19Arf and Interferon-ß Gene Transfer in a Heterotopic Mouse Model of Lung Carcinoma.

Therapeutic strategies that act by eliciting and enhancing antitumor immunity have been clinically validated as an effective treatment modality but may benefit from the induction of both cell death and immune activation as primary stimuli. Using our AdRGD-PG adenovector platform, we show here for the first time that in situ gene transfer of p19Arf and interferon-ß (IFNß) in the LLC1 mouse model of lung carcinoma acts as an immunotherapy. Although p19Arf is sufficient to induce cell death, only its pairing with IFNß significantly induced markers of immunogenic cell death. In situ gene therapy with IFNß, either alone or in combination with p19Arf, could retard tumor progression, but only the combined treatment was associated with a protective immune response. Specifically in the case of combined intratumoral gene transfer, we identified 167 differentially expressed genes when using microarray to evaluate tumors that were treated in vivo and confirmed the activation of CCL3, CXCL3, IL1α, IL1ß, CD274, and OSM, involved in immune response and chemotaxis. Histologic evaluation revealed significant tumor infiltration by neutrophils, whereas functional depletion of granulocytes ablated the antitumor effect of our approach. The association of in situ gene therapy with cisplatin resulted in synergistic elimination of tumor progression. In all, in situ gene transfer with p19Arf and IFNß acts as an immunotherapy involving recruitment of neutrophils, a desirable but previously untested outcome, and this approach may be allied with chemotherapy, thus providing significant antitumor activity and warranting further development for the treatment of lung carcinoma.