Interferon-α and antisense K-ras RNA combination gene therapy against pancreatic cancer

The use of adenoviral vectors in gene therapy and vaccine approaches

Adenovirus was first identified in the 1950s and since then this pathogenic group of viruses has been explored and transformed into a genetic transfer vehicle. Modification or deletion of few genes are necessary to transform it into a conditionally or non-replicative vector, creating a versatile tool capable of transducing different tissues and inducing high levels of transgene expression. In the early years of vector development, the application in monogenic diseases faced several hurdles, including short-term gene expression and even a fatality. On the other hand, an adenoviral delivery strategy for treatment of cancer was the first approved gene therapy product. There is an increasing interest in expressing transgenes with therapeutic potential targeting the cancer hallmarks, inhibiting metastasis, inducing cancer cell death or modulating the immune system to attack the tumor cells. Replicative adenovirus as vaccines may be even older and date to a few years of its discovery, application of non-replicative adenovirus for vaccination against different microorganisms has been investigated, but only recently, it demonstrated its full potential being one of the leading vaccination tools for COVID-19. This is not a new vector nor a new technology, but the result of decades of careful and intense work in this field.

Intratumoral IFN-α gene delivery reduces tumor-infiltrating regulatory T cells through the downregulation of tumor CCL17 expression

The effect of IFN-α on the immunosuppressive tumor microenvironment is not fully understood. We previously reported that intratumoral IFN-α gene transduction decreased the frequency of regulatory T cells (Tregs) in the tumor by inducing the secretion of IL-6 from dendritic cells. In this study, we examined whether IFN-α affects the trafficking of Tregs to the tumor. Since CT26 cells expressed CCL17 among Treg-attracting chemokines, we focused on its role in IFN-α-mediated Treg suppression. IFN-α directly suppressed CCL17 production from CT26 cells in vitro, and IFN-α transduction reduced CCL17 expression in tumors in vivo. Next, to investigate whether CCL17 downregulation is related to the suppression of Treg trafficking, CCL17-downregulated CT26 cells produced using short hairpin RNA (CT26-shCCL17) were inoculated into mice. The frequency of Tregs in CT26-shCCL17 tumors was reduced and tumor growth was suppressed. Finally, to examine the combinatorial effect of IFN-α expression with CCL17 downregulation, IFN-α was transduced into CT26-shCCL17 tumors. This resulted in an elevation of CT26-specific CD8⁺ T cells and the complete eradication of tumors. This study shows a novel mechanism of IFN-α-mediated Treg suppression, and combining IFN-α gene therapy with strong CCL17 downregulation could offer a promising strategy for the treatment of cancer.

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-β, and their antitumor effects, impact on immune responses and their use as therapeutic agents. IFN-α/β 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/β, 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/β has been tested, including stimulation through pattern recognition receptors. Gene therapies involving IFN-α/β have also been described. Thus, harnessing type I IFNs as an effective tool for cancer therapy continues to be studied.

Showing the Way: Oncolytic Adenoviruses as Chaperones of Immunostimulatory Adjuncts

Oncolytic adenoviruses (OAds) are increasingly recognized as vectors for immunotherapy in the treatment of various solid tumors. The myriads of advantages of using adenovirus include targeted specificity upon infection and selective replication, which lead to localized viral burst, exponential spread of OAds, and antitumor effect. OAds can also induce a strong immune reaction due to the massive release of tumor antigens upon cytolysis and the presence of viral antigens. This review will highlight recent advances in adenoviral vectors expressing immunostimulatory effectors, such as GM-CSF (granulocyte macrophage colony-stimulating factor), interferon-α, interleukin-12, and CD40L. We will also discuss the combination of OAds with other immunotherapeutic strategies and describe the current understanding of how adenoviral vectors interact with the immune system to eliminate cancer cells.

Oncolytic adenovirus expressing interferon alpha in a syngeneic Syrian hamster model for the treatment of pancreatic cancer

BACKGROUND

The addition of interferon (IFN) alpha to adjuvant chemoradiotherapy regimens resulted in remarkable improvements in survival for pancreatic cancer patients. However, systemic toxicities and insufficient levels of IFN at the tumor sites have limited its widespread adoption in treatment schemes. We have previously developed an IFN-expressing conditionally replicative oncolytic adenovirus and demonstrated its therapeutic effects both in vitro and in vivo. Here, the same vectors were tested in a syngeneic and immunocompetent Syrian hamster model to better understand the roles of adenoviral replication and of the pleiotropic effects of IFN on pancreatic tumor growth suppression.

METHODS

Oncolytic adenoviruses expressing human or hamster IFN were designed and generated. Viral vectors were tested in vitro to determine qualitative and quantitative cell viability, cyclooxygenase 2 (Cox2) promoter activity, and IFN production. For the in vivo studies, subcutaneous hamster pancreatic cancer tumors were treated with 1 intratumoral dose of virus. Similarly, 1 intraperitoneal dose of virus was used to prolong survival in a carcinomatosis model.

RESULTS

All cell lines tested demonstrated Cox2 promoter activity. The oncolytic potential of a replication competent adenovirus expressing the IFN cytokine was clearly demonstrated. These viruses resulted in significant tumor growth suppression and survival increases compared with controls in a hamster model.

CONCLUSION

The profound therapeutic potential of an IFN-expressing oncolytic adenovirus for the treatment of pancreatic cancer was demonstrated in a syngeneic Syrian hamster model. These results strongly suggest the potential application of our viruses as part of combination regimens with other therapeutics.

Suppression of Tregs by anti-glucocorticoid induced TNF receptor antibody enhances the antitumor immunity of interferon-α gene therapy for pancreatic cancer

We have reported that interferon (IFN)-α can attack cancer cells by multiple antitumor mechanisms including the induction of direct cancer cell death and the enhancement of an immune response in several pancreatic cancer models. However, an immunotolerant microenvironment in the tumors is often responsible for the failure of the cancer immunotherapy. Here we examined whether the suppression of regulatory T cells (Tregs) within tumors can enhance an antitumor immunity induced by an intratumoral IFN-α gene transfer. First we showed that an intraperitoneal administration of an agonistic anti-glucocorticoid induced TNF receptor (GITR) monoclonal antibody (mAb), which is reported to suppress the function of Tregs, significantly inhibited subcutaneous tumor growth in a murine pancreatic cancer model. The anti-GITR mAb was then combined with the intratumoral injection of the IFN-α-adenovirus vector. The treatment with the antibody synergistically augmented the antitumor effect of IFN-α gene therapy not only in the vector-injected tumors but also in the vector-uninjected tumors. Immunostaining showed that the anti-GITR mAb decreased Foxp3⁺ cells infiltrating in the tumors, while the intratumoral IFN-α gene transfer increased CD4⁺ and CD8⁺ T cells in the tumors. Therefore, the combination therapy strongly inclined the immune balance of the tumor microenvironment in an antitumor direction, leading to a marked systemic antitumor effect. The CCR5 expression on Tregs was downregulated in the antibody-treated mice, which may explain the decrease of tumor-infiltrating Tregs. The combination of Treg-suppression by GITR mAb and the tumor immunity induction by IFN-α gene therapy could be a promising therapeutic strategy for pancreatic cancer.

Differential expression of IL-17, 22 and 23 in the progression of colorectal cancer in patients with K-ras mutation: Ras signal inhibition and crosstalk with GM-CSF and IFN-γ

Recent studies have suggested that aberrant K-ras signaling is responsible for triggering immunological responses and inflammation-driven tumorigenesis. Interleukins IL-17, IL-22, and IL-23 have been reported in various types of malignancies, but the exact mechanistic role of these molecules remains to be elucidated. Given the role of K-ras and the involvement of interleukins in colorectal tumorigenesis, research efforts are reported for the first time, showing that differentially expressed interleukin IL-17, IL-22, and IL-23 levels are associated with K-ras in a stage-specific fashion along colorectal cancer progression. Specifically, a) the effect of K-ras signaling was investigated in the overall expression of interleukins in patients with colorectal cancer and healthy controls, and b) an association was established between mutant K-ras and cytokines GM-CSF and IFN-γ. The results indicate that specific interleukins are differentially expressed in K-ras positive patients and the use of K-ras inhibitor Manumycin A decreases both interleukin levels and apoptosis in Caco-2 cells by inhibiting cell viability. Finally, inflammation-driven GM-CSF and IFN-γ levels are modulated through interleukin expression in tumor patients, with interleukin expression in the intestinal lumen and cancerous tissue mediated by aberrant K-ras signaling. Collectively, the findings a) indicate that interleukin expression is influenced by ras signaling and specific interleukins play an oncogenic promoter role in colorectal cancer, highlighting the molecular link between inflammation and tumorigenesis, and b) accentuate the interwoven molecular correlations as leads to new therapeutic approaches in the future.

Plasmacytoid dendritic cells in the tumor microenvironment: immune targets for glioma therapeutics

Adenovirus-mediated delivery of the immune-stimulatory cytokine Flt3L and the conditionally cytotoxic thymidine kinase (TK) induces tumor regression and long-term survival in preclinical glioma (glioblastoma multiforme [GBM]) models. Flt3L induces expansion and recruitment of plasmacytoid dendritic cells (pDCs) into the brain. Although pDCs can present antigen and produce powerful inflammatory cytokines, that is, interferon α (IFN-α), their role in tumor immunology remains debated. Thus, we studied the role of pDCs and IFN-α in Ad.TK/GCV+ Ad.Flt3L-mediated anti-GBM therapeutic efficacy. Our data indicate that the combined gene therapy induced recruitment of plasmacytoid DCs (pDCs) into the tumor mass; which were capable of in vivo phagocytosis, IFN-α release, and T-cell priming. Thus, we next used either pDCs or an Ad vector encoding IFN-α delivered within the tumor microenvironment. When rats were treated with Ad.TK/GCV in combination with pDCs or Ad-IFN-α, they exhibited 35% and 50% survival, respectively. However, whereas intracranial administration of Ad.TK/GCV + Ad.Flt3L exhibited a high safety profile, Ad-IFN-α led to severe local inflammation, with neurologic and systemic adverse effects. To elucidate whether the efficacy of the immunotherapy was dependent on IFN-α-secreting pDCs, we administered an Ad vector encoding B18R, an IFN-α antagonist, which abrogated the antitumoral effect of Ad.TK/GCV + Ad.Flt3L. Our data suggest that IFN-α release by activated pDCs plays a critical role in the antitumor effect mediated by Ad.TK/GCV + Ad.Flt3L. In summary, taken together, our results demonstrate that pDCs mediate anti-GBM therapeutic efficacy through the production of IFN-α, thus manipulation of pDCs constitutes an attractive new therapeutic target for the treatment of GBM.

Delivery of interferon alpha using a novel Cox2-controlled adenovirus for pancreatic cancer therapy

BACKGROUND

Combination therapy with interferon alpha (IFN) is correlated with improved survival in patients with pancreatic ductal adenocarcinoma (PDAc) but frequently presents side effects. We designed a novel targeted adenovirus with replication restricted to cyclooxygenase 2 (Cox2)-overexpressing PDAcs and hypothesize that the locally delivered therapeutic gene IFN can augment oncolytic effects while minimizing systemic toxicity.

METHODS

IFN-expressing vectors were tested in vitro with the use of 4 PDAc cell lines with cytocidal effect measured by crystal violet and colorimetrically and IFN production assayed by ELISA. Cox2 promoter activity was checked by a luciferase reporter assay. In vivo, subcutaneous tumor xenografts with 2 PDAc cell lines in nude mice were treated with a single intratumoral viral dose.

RESULTS

All PDAc cell lines were Cox2-positive. Oncolysis from the novel Cox2-controlled virus was comparable or superior to Adwt, the wild-type virus without safety features. The absence of cytocidal effect in Cox2-negative cells with the novel virus indicated cancer specificity. In vivo, stronger tumor suppression from the novel virus was seen when compared with nonreplicating IFN-expressing vectors.

CONCLUSION

We demonstrated the potent therapeutic effects of a novel tumor-specific conditionally replicative IFN-expressing adenovirus. With potential to locally deliver IFN and avoid systemic toxicity, this strategy may therefore expand the application of this robust and promising therapy.

Syngeneic hematopoietic stem cell transplantation enhances the antitumor immunity of intratumoral type I interferon gene transfer for sarcoma

Sarcoma at advanced stages remains a clinically challenging disease. Interferons (IFNs) can target cancer cells by multiple antitumor activities, including the induction of cancer cell death and enhancement of immune response. However, the development of an effective cancer immunotherapy is often difficult, because cancer generates an immunotolerant microenvironment against the host immune system. An autologous hematopoietic stem cell transplantation (HSCT) is expected to reconstitute a fresh immune system, and expand tumor-specific T cells through the process of homeostatic proliferation. Here we examined whether a combination of autologous HSCT and IFNs could induce an effective tumor-specific immune response against sarcoma. First, we found that a type I IFN gene transfer significantly suppressed the cell growth of various sarcoma cell lines, and that IFN-β gene transfer was more effective in inducing cell death than was IFN-α in sarcoma cells. Then, to examine the antitumor effect in vivo, human sarcoma cells were inoculated in immune-deficient mice, and a lipofection of an IFN-β-expressing plasmid was found to suppress the growth of subcutaneous tumors significantly. Finally, the IFN gene transfer was combined with syngeneic HSCT in murine osteosarcoma models. Intratumoral IFN-β gene transfer markedly suppressed the growth of vector-injected tumors and inhibited formation of spontaneous lung and liver metastases in syngeneic HSCT mice, and an infiltration of many immune cells was recognized in metastatic tumors of the treated mice. The treated mice showed no significant adverse events. A combination of intratumoral IFN gene transfer with autologous HSCT could be a promising therapeutic strategy for patients with sarcoma.

Pancreatic cancer: gene therapy approaches and gene delivery systems

IMPORTANCE OF THE FIELD

Due to the absence of early diagnosis, the highly invasive and metastatic features and the lack of effective therapeutic modalities, the prognosis of patients with pancreatic cancer is poor. Gene therapy is currently regarded as a potential and promising therapeutic modality for pancreatic cancer.

AREAS COVERED IN THIS REVIEW

This article summarizes an update of gene therapy approaches and reviews the latest progress in gene delivery systems that have been tested on pancreatic cancer.

WHAT THE READER WILL GAIN

The treatment effectiveness of gene combination therapy is better than that of the regulation of single-gene or single gene therapy approaches. Naked DNA is limited because of degradation by intracellular and extracellular nucleases. Virus vectors show high transfection efficiency but are limited due to immunogenicity, inflammatory response and potential carcinogenicity. Non-viral vectors, such as cationic polymers or inorganic nanoparticles, show an important feature that they can be easily modified, and the progress of materials science will provide more and better non-viral vectors, accordingly improving the efficiency and safety of gene therapy, which will make them the most promising vectors for pancreatic cancer.

Administration route-dependent induction of antitumor immunity by interferon-alpha gene transfer

Type I interferon (IFN) protein is a cytokine with pleiotropic biological functions that include induction of apoptosis, inhibition of angiogenesis, and immunomodulation. We have demonstrated that intratumoral injection of an IFN-alpha-expressing adenovirus effectively induces cell death of cancer cells and elicits a systemic tumor-specific immunity in several animal models. On the other hand, reports demonstrated that an elevation of IFN in the serum following an intramuscular delivery of a vector is able to activate antitumor immunity. In this study, we compared the intratumoral and systemic routes of IFN gene transfer with regard to the effect and safety of the treatment. Intratumoral injection of an IFN-alpha adenovirus effectively activated tumor-responsive lymphocytes and caused tumor suppression not only in the gene-transduced tumors but also in distant tumors, which was more effective than the intravenous administration of the same vector. The expression of co-stimulatory molecules on CD11c(+) cells isolated from regional lymph nodes was enhanced by IFN gene transfer into the tumors. Systemic toxicity such as an elevation of hepatic enzymes was much lower in mice treated by intratumoral gene transfer than in those treated by systemic gene transfer. Our data suggest that the intratumoral route of the IFN vector is superior to intravenous administration, due to the effective induction of antitumor immunity and the lower toxicity.

Intratumoral interferon-alpha gene transfer enhances tumor immunity after allogeneic hematopoietic stem cell transplantation

One of the major challenges in the treatment of solid cancers by allogenic hematopoietic stem cell transfer (alloHSCT) is the specific enhancement of antitumor immunity. Interferon (IFN) is a cytokine with pleiotropic biological functions including an immunomoduration, and our preclinical studies have shown that an intratumoral IFN-alpha gene transfer induced strong local tumor control and systemic tumor-specific immunity. In the present study, we examined whether the IFN-alpha gene transfer could enhance recognition of tumor-associated antigens by donor T cells and augment the antitumor activity of alloHSCT. First, when a mouse IFN-alpha adenovirus vector (Ad-mIFN) was injected into subcutaneous xenografts of syngeneic renal and colon cancer cells, tumor growth was significantly suppressed in a dose-dependent manner. A significant tumor cell death and infiltration of immune cells was recognized in the Ad-mIFN-injected tumors, and the dendritic cells isolated from the tumors showed a strong Th1-oriented response. The antitumor effect of Ad-mIFN was then examined in a murine model of minor histocompatibility antigen-mismatched alloHSCT. The intratumoral IFN-alpha gene transfer caused significant tumor suppression in the alloHSCT recipients, and this suppression was evident not only in the gene-transduced tumors but also in simultaneously inoculated distant tumors which did not receive the vector injection. A cytotoxicity assay showed specific tumor cell lysis by donor T cells responding to IFN-alpha. Graft-versus-host disease was not exacerbated serologically or clinically in the mice treated with IFN-alpha. This combination strategy deserves evaluation in future clinical trials for human solid cancers.

Extracellular matrix interacts with interferon alpha protein: retention and display of cytotoxicity

We have been investigating the efficacy of an intratumoral interferon (IFN)-alpha gene transfer against solid cancers, and found that when the gene is transduced into the subcutaneous tumors, IFN-alpha concentration is markedly increased in the injected tumor but not in the serum. To explain this effective confinement of IFN-alpha to target tissues, we hypothesized that the extracellular matrix in the tumors interacts with IFN-alpha. In this study, a solid-phase-binding assay and immunoprecipitation demonstrated that the IFN-alpha binds directly to matrix proteins. Immunohistochemical staining showed a co-localization of IFN-alpha with pericellular fibronectin. In addition, matrix-bound IFN-alpha protein transduced intracellular signaling and potentiated its cytotoxic activity, suggesting that the retention of IFN-alpha protein on extracellular matrix is likely to play a role in its in vivo biological activity. The data suggest a therapeutic advantage of the intratumoral IFN-alpha gene transfer over the conventional parenteral therapy both in the safety and efficacy.

Local interferon-alpha gene therapy elicits systemic immunity in a syngeneic pancreatic cancer model in hamster

The interferon (IFN) protein is a cytokine with pleiotropic biological functions that include induction of apoptosis, inhibition of angiogenesis and immunomodulation. We previously examined the two antitumor mechanisms, taking advantage of the fact that IFN-alpha did not show cross-species activity in its in vivo effect. In a nude mouse subcutaneous xenograft model using human pancreatic cancer cells, the expression of human IFN-alpha effectively induced cell death of human pancreatic cancer cells, whereas mouse IFN-alpha augmented antitumor immunity by stimulation of natural killer cells. Here, we extended our investigation to a syngeneic pancreatic cancer model, so that the integrated antitumor activity of local IFN-alpha gene therapy, including the antiproliferative, proapoptotic, antiangiogeneic and immunomodulatory effects, can be evaluated rigorously. When a recombinant hamster IFN-alpha adenovirus was injected into syngeneic subcutaneous tumors of hamster pancreatic cancer (PGHAM-1) cells in Syrian hamster, tumor growth was significantly suppressed due to cell death and T cell- and natural killer cell-mediated antitumor immunity. Moreover, in this case, tumor regression was observed not only for the injected subcutaneous tumors but also for the untreated tumors both in the peritoneal cavity and at distant sites. No significant systemic toxicity was observed in the treated hamsters. Moreover, the subcutaneous rechallenge of PGHAM-1 cells was rejected in three of four cured hamsters from the initial tumor challenge. This study further demonstrated that local IFN-alpha gene therapy is a promising therapeutic strategy for pancreatic cancer, due to its multiple mechanisms of antitumor activity and its lack of significant toxicity.

Current update of cytokines in pancreatic cancer: pathogenic mechanisms, clinical indication, and therapeutic values

Pancreatic cancer is the fourth leading cause of cancer death with a 5-year survival less than 5 percent despite rigorous interventions. This largely is due to its late presentation, aggressive metastasis, and a lack of effective adjuvant therapies. Cytokines have been studied in many tumor types, where they have been shown to be an important influence in cancer cell behavior and to have potential as tumor markers, therapeutic targets, or as treatments themselves. Recently, the roles cytokines play in pancreatic cancer have become the subject of intense investigation. However, the story is complicated, largely because of the pleiotropic and overlapping nature of cytokine functions. This article attempts to provide a focused review of recent discoveries in this area by organizing the material along the pathophysiologic tasks a cancer cell must accomplish to achieve malignancy. We examined how cytokines act to create a microenvironment conducive to tumor cell survival and growth, discussed how cytokines affect proliferation, invasion, metastasis, and apoptosis in pancreatic cancer cells, and we summarized how this knowledge has been applied either to target cytokines or use them therapeutically.

Replication-deficient rSV40 mediate pancreatic gene transfer and long-term inhibition of tumor growth

Pancreatic cancer is one of the most aggressive and devastating human malignancies. There is an urgent need for more effective therapy for patients with advanced disease. In this context, genetic therapy potentially represents a rational new approach to treating pancreatic cancer, which could provide an adjunct to conventional options. Because of the promise of recombinant SV40 vectors, we tested their ability to deliver a transgene, and to target a transcript, so as to inhibit pancreatic tumors growth in vivo. BxPC3 and Capan-1 cells were efficiently transduced using SV40 vectors without selection, as compared to synthetic vectors PEI. SV40 vectors were as efficient as adenoviral vectors, and provided long-term transgene expression. Next, we devised a SV40-derived, targeted gene therapy approach of pancreatic cancer, by combining hTR tumor-specific promoter with sst2 somatostatin receptor tumor-suppressor gene. In vitro cell proliferation was strongly impaired following administration of SV(hTR-sst2). SV40-derived sst2-mediated antiproliferative effect was dependent on the local production of somatostatin. In vivo, intratumoral gene transfer of sst2 using rSV40 vectors resulted in a marked inhibition of Capan-1 tumor progression, and proliferation. These results represent the initial steps toward a novel approach to the gene therapy of pancreatic cancer using SV40 as a vector.

Gene therapy developments for pancreatic cancer

Treatment options for pancreatic cancer have limited success and it is therefore an appropriate target for the development of new strategies, including gene therapy. Gene therapy approaches include inhibition of activated oncogenes (KRAS, LSM1) with antisense and RNA interference strategies, replacement of inactivated tumour suppressor genes (TP53, CDKN2A, CDKN1A), targeting of cell signalling pathways, gene-directed prodrug-activation therapies and the use of replication-competent oncolytic viruses. Angiogenesis and apoptosis have also been targeted for gene therapy. Clinical trials of gene therapy have shown only moderate anti-tumour effects. As there are many genetic abnormalities in pancreatic cancer, strategies combining different targets or indeed different modalities of treatment, may be more successful. Identification of new targets and improvements in delivery and targeting may further improve the efficacy of gene therapy in pancreatic cancer.

Adenovirus-mediated interferon alpha gene transfer induces regional direct cytotoxicity and possible systemic immunity against pancreatic cancer

We previously demonstrated a characteristically high sensitivity of pancreatic cancer cells to interferon alpha (IFN-alpha) gene transfer, which induced a more prominent growth suppression and cell death in pancreatic cancer cells than in other types of cancers and normal cells. The IFN-alpha protein can exhibit both direct cytotoxicity and indirect immunological antitumour activity. Here, we dissected and examined the two mechanisms, taking advantage of the fact that IFN-alpha did not show any cross-species activity in its in vivo effect. When a human IFN-alpha adenovirus was injected into subcutaneous xenografts of human pancreatic cancer cells in nude mice, tumour growth was significantly suppressed due to cell death in an adenoviral dose-dependent manner. The IFN-alpha protein concentration was markedly increased in the injected subcutaneous tumour, but leakage of the potent cytokine into the systemic blood circulation was minimal. When a mouse IFN-alpha adenovirus was injected into the same subcutaneous tumour system, all mice showed significant tumour inhibition, an effect that was dependent on the indirect antitumour activities of IFN-alpha, notably a stimulation of natural killer cells. Moreover, in this case, tumour regression was observed not only for the injected subcutaneous tumours but also for the untreated tumours at distant sites. This study suggested that a local IFN-alpha gene therapy is a promising therapeutic strategy for pancreatic cancer, due to its dual mechanisms of antitumour activities and lack of significant toxicity.

Efficient human interferon-alpha gene transfer to neuroendocrine tumor cells with long-term and stable expression

Interferon (IFN)-alpha has been used in the treatment of neuroendocrine (NE) tumors; however, the feasibility of IFN-alpha gene therapy has not been evaluated in NE tumor cells. In this study, human IFN-alpha2 (hIFN-alpha2) gene has been transferred into a NE tumor cell line BON. hIFN-alpha2-expressing BON cells were subcutaneously inoculated in nude mice. The results demonstrated that hIFN-alpha2 exerted significant antiproliferative effects on NE tumor cell lines (BON and LCC18) and other tumor cell lines (CA46 and SW480) as well as porcine aorta cell line. Furthermore, hIFN-alpha2 demonstrated its antineovascular activity in mice tumor and a direct antiangiogenic effect in chicken chorioallantoic membrane assay. hIFN-alpha2-expressing BON cells had a stable and long-term expression. Mice implanted with hIFN-alpha2-expressing BON cells showed a lower incidence, a delayed development and a significantly longer doubling time of the tumor compared to both wild-type (WT) and vector group. In addition, IFN-alpha significantly inhibited cell adhesion of WT BON cells. hIFN-alpha2-expressing BON tumors had a high level of hIFN-alpha2 protein. Finally, mice implanted with a mixture of WT and hIFN-alpha2-expressing BON cells (1:1) presented a delayed tumor development and had an even lower incidence of tumors than those implanted with hIFN-alpha2-expressing BON cells only. The doubling time of tumor was also longest in the mixture group. Our data suggest that hIFN-alpha2 gene therapy might be possible to be used as a new treatment for NE tumor patients. Further studies on the regulation of hIFN-alpha expression are needed, especially in combination with other cytokines, which could lead to a better understanding and improvements of hIFN-alpha gene therapy.