A combinatorial approach for selectively inducing programmed cell death in human pancreatic cancer cells

Insights into the Mechanisms of Action of MDA-7/IL-24: A Ubiquitous Cancer-Suppressing Protein

Melanoma differentiation associated gene-7/interleukin-24 (MDA-7/IL-24), a secreted protein of the IL-10 family, was first identified more than two decades ago as a novel gene differentially expressed in terminally differentiating human metastatic melanoma cells. MDA-7/IL-24 functions as a potent tumor suppressor exerting a diverse array of functions including the inhibition of tumor growth, invasion, angiogenesis, and metastasis, and induction of potent "bystander" antitumor activity and synergy with conventional cancer therapeutics. MDA-7/IL-24 induces cancer-specific cell death through apoptosis or toxic autophagy, which was initially established in vitro and in preclinical animal models in vivo and later in a Phase I clinical trial in patients with advanced cancers. This review summarizes the history and our current understanding of the molecular/biological mechanisms of MDA-7/IL-24 action rendering it a potent cancer suppressor.

Amalgamation of PI3K and EZH2 blockade synergistically regulates invasion and angiogenesis: combination therapy for glioblastoma multiforme

Glioblastoma multiforme is known as the primary malignant and most devastating form of tumor in central nervous system of adult population. Amongst all CNS cancers, Glioblastoma multiforme GBM is a rare grade IV astrocytoma and it has the worst prognosis initiated by metastasis to supra-tentorial region of the brain. Current options for the treatment include surgery, radiation therapy and chemotherapy. Substantial information of its pathology and molecular signaling exposed new avenues for generating innovative therapies. In our study, we have undertaken a novel combination approach for GBM treatment. PI3K signaling participates in cancer progression and plays a significant role in metastasis. Here, we are targeting PI3K signaling pathways in glioblastoma along with EZH2, a known transcriptional regulator. We found that targeting transcriptional regulator EZH2 and PI3K affect cellular migration and morphological changes. These changes in signatory activities of cancerous cells led to inhibit its progression in vitro. With further analysis we confirmed the angiogenic inhibition and reduction in stem-ness potential of GBM. Later, cytokine proteome array analysis revealed several participants of metastasis and tumor induced angiogenesis using combination regime. This study provides a significant reduction in GBM progression investigated using Glioblastoma Multiforme U-87 cells with effective combination of pharmacological inhibitors PI-103 and EPZ-6438. This strategy will be further used to combat GBM more innovatively along with the existing therapies.

Suppression of Her2/Neu mammary tumor development in mda-7/IL-24 transgenic mice

Melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) encodes a tumor suppressor gene implicated in the growth of various tumor types including breast cancer. We previously demonstrated that recombinant adenovirus-mediated mda-7/IL-24 expression in the mammary glands of carcinogen-treated (methylnitrosourea, MNU) rats suppressed mammary tumor development. Since most MNU-induced tumors in rats contain activating mutations in Ha-ras, which arenot frequently detected in humans, we presently examined the effect of MDA-7/IL-24 on Her2/Neu-induced mammary tumors, in which the RAS pathway is induced. We generated tet-inducible MDA-7/IL-24 transgenic mice and crossed them with Her2/Neu transgenic mice. Triple compound transgenic mice treated with doxycycline exhibited a strong inhibition of tumor development, demonstrating tumor suppressor activity by MDA-7/IL-24 in immune-competent mice. MDA-7/IL-24 induction also inhibited growth of tumors generated following injection of Her2/Neu tumor cells isolated from triple compound transgenic mice that had not been treated with doxycycline, into the mammary fat pads of isogenic FVB mice. Despite initial growth suppression, tumors in triple compound transgenic mice lost mda-7/IL-24 expression and grew, albeit after longer latency, indicating that continuous presence of this cytokine within tumor microenvironment is crucial to sustain tumor inhibitory activity. Mechanistically, MDA-7/IL-24 exerted its tumor suppression effect on HER2⁺ breast cancer cells, at least in part, through PERP, a member of PMP-22 family with growth arrest and apoptosis-inducing capacity. Overall, our results establish mda-7/IL-24 as a suppressor of mammary tumor development and provide a rationale for using this cytokine in the prevention/treatment of human breast cancer.

Radiogenic Therapy: Novel Approaches for Enhancing Tumor Radiosensitivity

Radiotherapy (RT) is a well established modality for treating many forms of cancer. However, despite many improvements in treatment planning and delivery, the total radiation dose is often too low for tumor cure, because of the risk of normal tissue damage. Gene therapy provides a new adjunctive strategy to enhance the effectiveness of RT, offering the potential for preferential killing of cancer cells and sparing of normal tissues. This specificity can be achieved at several levels including restricted vector delivery, transcriptional targeting and specificity of the transgene product. This review will focus on those gene therapy strategies that are currently being evaluated in combination with RT, including the use of radiation sensitive promoters to control the timing and location of gene expression specifically within tumors. Therapeutic transgenes chosen for their radiosensitizing properties will also be reviewed, these include:

gene correction therapy, in which normal copies of genes responsible for radiation-induced apoptosis are transfected to compensate for the deletions or mutated variants in tumor cells (p53 is the most widely studied example). enzymes that synergize the radiation effect, by generation of a toxic species from endogenous precursors ( e.g., inducible nitric oxide synthase) or by activation of non toxic prodrugs to toxic species ( e.g., herpes simplex virus thymidine kinase/ganciclovir) within the target tissue. conditionally replicating oncolytic adenoviruses that synergize the radiation effect. membrane transport proteins ( e.g., sodium iodide symporter) to facilitate uptake of cytotoxic radionuclides.

The evidence indicates that many of these approaches are successful for augmenting radiation induced tumor cell killing with clinical trials currently underway.

MDA-7/IL-24 functions as a tumor suppressor gene in vivo in transgenic mouse models of breast cancer

Melanoma differentiation associated gene-7/Interleukin-24 (MDA-7/IL-24) is a novel member of the IL-10 gene family that selectively induces apoptosis and toxic autophagy in a broad spectrum of human cancers, including breast cancer, without harming normal cells or tissues. The ability to investigate the critical events underlying cancer initiation and progression, as well as the capacity to test the efficacy of novel therapeutics, has been significantly advanced by the development of genetically engineered mice (GEMs) that accurately recapitulate specific human cancers. We utilized three transgenic mouse models to better comprehend the in vivo role of MDA-7/IL-24 in breast cancer. Using the MMTV-PyMT spontaneous mammary tumor model, we confirmed that exogenously introducing MDA-7/IL-24 using a Cancer Terminator Virus caused a reduction in tumor burden and also produced an antitumor "bystander" effect. Next we performed xenograft studies in a newly created MMTV-MDA-7 transgenic model that over-expresses MDA-7/IL-24 in the mammary glands during pregnancy and lactation, and found that MDA-7/IL-24 overexpression delayed tumor growth following orthotopic injection of a murine PDX tumor cell line (mPDX) derived from a tumor formed in an MMTV-PyMT mouse. We also crossed the MMTV-MDA-7 line to MMTV-Erbb2 transgenic mice and found that MDA-7/IL-24 overexpression delayed the onset of mammary tumor development in this model of spontaneous mammary tumorigenesis as well. Finally, we assessed the role of MDA-7/IL-24 in immune regulation, which can potentially contribute to tumor suppression in vivo. Our findings provide further direct in vivo evidence for the role of MDA-7/IL-24 in tumor suppression in breast cancer in immune-competent transgenic mice.

Gene Therapies for Cancer: Strategies, Challenges and Successes

Gene therapy, which involves replacement of a defective gene with a functional, healthy copy of that gene, is a potentially beneficial cancer treatment approach particularly over chemotherapy, which often lacks selectivity and can cause non-specific toxicity. Despite significant progress pre-clinically with respect to both enhanced targeting and expression in a tumor-selective manner several hurdles still prevent success in the clinic, including non-specific expression, low-efficiency delivery and biosafety. Various innovative genetic approaches are under development to reconstruct vectors/transgenes to make them safer and more effective. Utilizing cutting-edge delivery technologies, gene expression can now be targeted in a tissue- and organ-specific manner. With these advances, gene therapy is poised to become amenable for routine cancer therapy with potential to elevate this methodology as a first line therapy for neoplastic diseases. This review discusses recent advances in gene therapy and their impact on a pre-clinical and clinical level.

Stem cells as cellular vehicles for gene therapy against glioblastoma

Glioblastoma (GBM) is the most common and deadliest primary tumor in adults, with current treatments having limited specific and efficient delivery of therapeutic drugs to tumor sites or cells. Therefore, the development of alternative treatment options is urgently needed. Stem cells are considered as ideal cellular vehicles for gene therapy against glioblastoma. In this paper, we reviewed the recent studies investigating the use of different types of stem cells as cellular vehicles and the gene of interests against the glioblastoma, as well as the future directions of the application of cellular vehicles mediated therapy for glioblastoma.

A combinatory use of adenoviruses expressing melanoma differentiation-associated gene-7 and replication-competent adenoviruses produces synergistic effects on pancreatic carcinoma cells

Type 5 adenoviruses expressing mda-7 gene (Ad-mda-7) induced cell death in various kinds of human tumors, but pancreatic carcinoma cells were relatively resistant to Ad-mda-7-mediated cytotoxicity. We then examined whether infection of Ad-mda-7 together with replication-competent Ad produced combinatory cytotoxic effects. We prepared replication-competent Ad, defective of the E1B55kDa gene or activated by a transcriptional regulatory region of the midkine or the survivin gene of which the expression was up-regulated in human tumors. Type 5 Ad bearing the exogenous regulatory region were further modified by replacing the fiber-knob region with that of type 35 Ad. Pancreatic carcinoma cells were infected with replication-incompetent Ad-mda-7 and the replication-competent Ad. Combinatory effects were examined with the CalcuSyn software and cell cycle analyses. Ad-mda-7 and the replication-competent Ad achieved cytotoxicity to pancreatic carcinoma. A combinatory use of Ad-mda-7 and either Ad defective of the E1B55kDa gene or Ad activated by the regulatory region produced synergistic cytotoxic effects. Cell cycle analyses demonstrated that the combination increased sub-G1 populations. These data collectively suggest that expression of MDA-7 augments cytotoxicity of replication-competent Ad and achieves adjuvant effects on Ad-mediated cell death.

Clusterin silencing sensitizes pancreatic cancer MIA-PaCa-2 cells to gmcitabine via regulation of NF-kB/Bcl-2 signaling

Clusterin (CLU) is known as a multifunctional protein involved in a variety of physiological processes including lipid transport, epithelial cell differentiation, tumorigenesis, and apoptosis. Our recent study has demonstrated that knockdown of clusterin sensitizes pancreatic cancer cell lines to gmcitabine treatment. However the details of this survival mechanism remain undefined. Of the various downstream targets of CLU, we examined activation of the NF-kB transcription factor and subsequent transcriptional regulation of BCL-2 gene in pancreatic cancer cell MIA-PaCa-2. The MIA-PaCa-2 cells were transfected with an antisense oligonucleotide (ASO) against clusterin, which led to a decreased protein level of the antiapoptotic gene BCL-2. Furthermore, inhibition of CLU decreased the function of NF-kB, which is capable of transcriptional regulation of the BCL-2 gene. Inhibiting this pathway increased the apoptotic effect of gmcitabine chemotherapy. Re-activated NF-kB resulted in attenuation of ASO-induced effects, followed by the bcl-2 upregulation, and bcl-2 re-inhibition resulted in attenuation of Re-activated NF-kB -induced effects. Animals injected with ASO CLU in MIA-PaCa-2 cells combined with gmcitabine treatment had fewer tumors than gmcitabine or ASO CLU alone. These findings suggest that knockdown of CLU sensitized MIA-PaCa-2 cells to gmcitabine chemotherapy through modulating NF-Kb/bcl-2 pathway.

Reversing translational suppression and induction of toxicity in pancreatic cancer cells using a chemoprevention gene therapy approach

Pancreatic cancer is an aggressive disease with limited therapeutic options. Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24), a potent antitumor cytokine, shows cancer-specific toxicity in a vast array of human cancers, inducing endoplasmic reticulum stress and apoptosis, toxic autophagy, an antitumor immune response, an antiangiogenic effect, and a significant "bystander" anticancer effect that leads to enhanced production of this cytokine through autocrine and paracrine loops. Unfortunately, mda-7/IL-24 application in pancreatic cancer has been restricted because of a "translational block" occurring after Ad.5-mda-7 gene delivery. Our previous research focused on developing approaches to overcome this block and increase the translation of the MDA-7/IL-24 protein, thereby promoting its subsequent toxic effects in pancreatic cancer cells. We demonstrated that inducing reactive oxygen species (ROS) after adenoviral infection of mda-7/IL-24 leads to greater translation into MDA-7/IL-24 protein and results in toxicity in pancreatic cancer cells. In this study we demonstrate that a novel chimeric serotype adenovirus, Ad.5/3-mda-7, displays greater efficacy in delivering mda-7/IL-24 compared with Ad.5-mda-7, although overall translation of the protein still remains low. We additionally show that d-limonene, a dietary monoterpene known to induce ROS, is capable of overcoming the translational block when used in combination with adenoviral gene delivery. This novel combination results in increased polysome association of mda-7/IL-24 mRNA, activation of the preinitiation complex of the translational machinery in pancreatic cancer cells, and culminates in mda-7/IL-24-mediated toxicity.

MDA-7/IL-24 inhibits cell survival by inducing apoptosis in nasopharyngeal carcinoma

AIMS

Nasopharyngeal carcinoma (NPC) is the most common primary malignancy of the nasopharynx. Due to its local recurrence and distant metastasis, conventional therapy is usually ineffective. MDA-7/IL-24 (melanoma differentiation associated gene 7), a member of the IL10 family of cytokines, inhibits growth of various human cancer cells, but the underlying mechanism is largely unknown. There is no report of mda-7 in nasopharyngeal carcinoma. We aimed to investigate the role of MDA-7/IL-24 in NPC.

METHODS

Immune defective adenoviral vector carrying the gene was produced, infected NPC CNE cells and observed its growth, cell proliferation, apoptosis and the effect of combination with chemotherapy.

RESULTS

The results showed that (1) MDA-7/IL-24 inhibited NPC CNE cell growth and survival; (2) mda-7 induced cell apoptosis and death; (3) MDA-7/IL-24 in collaboration with chemotherapy induced cell apoptosis significantly; (4) MDA-7/IL-24 induced cell apoptosis by down-regulation of anti-apoptosis molecules such as Bcl-2 and Bcl-xl and up-regulation of caspase 3.

CONCLUSION

The results suggested that MDA-7/IL-24 had obvious therapeutic effect in NPC cells. It is verified that adenovirus mediated MDA-7/IL-24 represents a potentially important new approach to NPC therapy.

A novel human interleukin-24 peptide created by computer-guided design contributes to suppression of proliferation in esophageal squamous cell carcinoma Eca-109 cells

Based on the three-dimensional modeling structure of human interleukin-24 (hIL-24) and its most likely active position predicted by solvent accessibility and apparent electrostatic properties, a novel hIL-24 peptide M1 was created by computer-guided molecular design. The cytotoxicity and cell selectivity of M1 were examined in three human carcinoma cell lines and one normal human embryo lung fibroblast cell line (HEL). MTT assay showed that M1 induced growth arrest in two IL-20 receptor complex-positive cancer cell lines (the esophageal squamous cell carcinoma cell line Eca-109 and the melanoma cell line A375), and antibodies against IL-24 or IL-20 receptor complexes significantly neutralized the inhibitory activity. Moreover, M1 had almost no cytotoxicity on the lung cancer A549 cell line, which lacks a full complement of the IL-20 receptor complexes, or on HEL cells that express the IL-20 receptor complexes. These findings demonstrate that M1 could act as an excellent candidate for the induction of growth arrest on receptor complex-positive cancer cells. In summary, the M1 peptide may represent a novel anticancer agent for esophageal squamous cell carcinoma therapy due to its cancer cell selectivity and its relatively low cytotoxicity to normal cells.

MDA-7/IL-24: multifunctional cancer killing cytokine

First identified almost two decades ago as a novel gene differentially expressed in human melanoma cells induced to terminally differentiate, MDA-7/IL-24 has since shown great potential as an anti-cancer gene. MDA-7/IL24, a secreted protein of the IL-10 family, functions as a cytokine at normal physiological levels and is expressed in tissues of the immune system. At supra-physiological levels, MDA-7/IL-24 plays a prominent role in inhibiting tumor growth, invasion, metastasis and angiogenesis and was recently shown to target tumor stem/initiating cells for death. Much of the attention focused on MDA-7/IL-24 originated from the fact that it can selectively induce cell death in cancer cells without affecting normal cells. Thus, this gene originally shown to be associated with melanoma cell differentiation has now proven to be a multi-functional protein affecting a broad array of cancers. Moreover, MDA-7/IL-24 has proven efficacious in a Phase I/II clinical trial in humans with multiple advanced cancers. As research in the field progresses, we will unravel more of the functions of MDA-7/IL-24 and define novel ways to utilize MDA-7/IL-24 in the treatment of cancer.

Enhanced prostate cancer gene transfer and therapy using a novel serotype chimera cancer terminator virus (Ad.5/3-CTV)

Few options are available for treating patients with advanced prostate cancer (PC). As PC is a slow growing disease and accessible by ultrasound, gene therapy could provide a viable option for this neoplasm. Conditionally replication-competent adenoviruses (CRCAs) represent potentially useful reagents for treating PC. We previously constructed a CRCA, cancer terminator virus (CTV), which showed efficacy both in vitro and in vivo for PC. The CTV was generated on a serotype 5-background (Ad.5-CTV) with infectivity depending on Coxsackie-Adenovirus Receptors (CARs). CARs are frequently reduced in many tumor types, including PCs thereby limiting effective Ad-mediated therapy. Using serotype chimerism, a novel CTV (Ad.5/3-CTV) was created by replacing the Ad.5 fiber knob with the Ad.3 fiber knob thereby facilitating infection in a CAR-independent manner. We evaluated Ad.5/3-CTV in comparison with Ad.5-CTV in low CAR human PC cells, demonstrating higher efficiency in inhibiting cell viability in vitro. Moreover, Ad.5/3-CTV potently suppressed in vivo tumor growth in a nude mouse xenograft model and in a spontaneously induced PC that develops in Hi-myc transgenic mice. Considering the significant responses in a Phase I clinical trial of a non-replicating Ad.5-mda-7 in advanced cancers, Ad.5/3-CTV may exert improved therapeutic benefit in a clinical setting.

Heat-shock protein 90 inhibitors synergistically enhance melanoma differentiation-associated gene-7-mediated cell killing of human pancreatic carcinoma

Pancreatic cancer is one of the intractable diseases and an effective therapeutic strategy is required to improve the prognosis. We examined possible antitumor effects of adenoviruses expressing melanoma differentiation-associated gene-7/interleukin-24 (Ad-mda-7) and a heat-shock protein 90 (Hsp90) inhibitor to human pancreatic carcinoma cells. Ad-mda-7 and an Hsp90 inhibitor, geldanamycin (GA), produced cytotoxic effects, and a combinatory use of Ad-mda-7 and GA further achieved synergistic effects. Administration of N-acetyl-L-cysteine, an inhibitor of reactive oxygen species, eliminated Ad-mda-7- and GA-mediated cytotoxicity. Ad-mda-7 augmented phosphorylated AKT levels but GA did not influence the phosphorylation. GA-treated cells showed cleavage of poly-(ADP-ribose) polymerase but not caspase-3, and upregulated Hsp70 and LC3A/B II levels, whereas Ad-mda-7-treated cells did not. GA treatments augmented ubiquitination and markedly increased melanoma differentiation-associated gene-7 (MDA-7) expression levels. These findings suggest that Ad-mda-7-mediated cytotoxicity is dependent on reactive oxygen species but independent of apoptosis or autophagy, and that GA-mediated cytotoxicity was linked with caspase-independent apoptosis and/or autophagy. A mechanism underlying the combinatory effects of Ad-mda-7 and GA remained complex and the synergism is attributable to multiple factors including increased MDA-7 protein stability by GA.

Novel mechanism of MDA-7/IL-24 cancer-specific apoptosis through SARI induction

Subtraction hybridization combined with induction of cancer cell terminal differentiation in human melanoma cells identified melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) and SARI (suppressor of AP-1, induced by IFN) that display potent antitumor activity. These genes are not constitutively expressed in cancer cells and forced expression of mda-7/IL-24 (Ad.mda-7) or SARI (Ad.SARI) promotes cancer-specific cell death. Ectopic expression of mda-7/IL-24 induces SARI mRNA and protein in a panel of different cancer cells, leading to cell death, without harming corresponding normal cells. Simultaneous inhibition of K-ras downstream extracellular signal-regulated kinase 1/2 signaling in pancreatic cancer cells reverses the translational block of MDA-7/IL-24 and induces SARI expression and cell death. Using SARI-antisense-based approaches, we demonstrate that SARI expression is necessary for mda-7/IL-24 antitumor effects. Secreted MDA-7/IL-24 protein induces antitumor "bystander" effects by promoting its own expression. Recombinant MDA-7/IL-24 (His-MDA-7) induces SARI expression, supporting the involvement of SARI in the MDA-7/IL-24-driven autocrine loop, culminating in antitumor effects. Moreover, His-MDA-7, after binding to its cognate receptors (IL-20R1/IL-20R2 or IL-22R/IL-20R2), induces intracellular signaling by phosphorylation of p38 MAPK, leading to transcription of a family of growth arrest and DNA damage inducible (GADD) genes, culminating in apoptosis. Inhibition of p38 MAPK fails to induce SARI following Ad.mda-7 infection. These findings reveal the significance of the mda-7/IL-24-SARI axis in cancer-specific killing and provide a potential strategy for treating both local and metastatic disease.

Combining histone deacetylase inhibitors with MDA-7/IL-24 enhances killing of renal carcinoma cells

In the present study we show that histone deacetylase inhibitors (HDACIs) enhance the anti-tumor effects of melanoma differentiation associated gene-7/interleukin 24 (mda-7/IL-24) in human renal carcinoma cells. Similar data were obtained in other GU tumor cells. Combination of these two agents resulted in increased autophagy that was dependent on expression of ceramide synthase 6, with HDACIs enhancing MDA-7/IL-24 toxicity by increasing generation of ROS and Ca²⁺. Knock down of CD95 protected cells from HDACI and MDA-7/IL-24 lethality. Sorafenib treatment further enhanced (HDACI + MDA-7/IL-24) lethality. Anoikis resistant renal carcinoma cells were more sensitive to MDA-7/IL-24 that correlated with elevated SRC activity and tyrosine phosphorylation of CD95. We employed a recently constructed serotype 5/3 adenovirus, which is more effective than a serotype 5 virus in delivering mda-7/IL-24 to renal carcinoma cells and which conditionally replicates (CR) in tumor cells expressing MDA-7/IL-24 by virtue of placing the adenoviral E1A gene under the control of the cancer-specific promoter progression elevated gene-3 (Ad.5/3-PEG-E1A-mda-7; CRAd.5/3-mda-7, Ad.5/3-CTV), to define efficacy in renal carcinoma cells. Ad.5/3-CTV decreased the growth of renal carcinoma tumors to a significantly greater extent than did a non-replicative virus Ad.5/3-mda-7. In contralateral uninfected renal carcinoma tumors Ad.5/3-CTV also decreased the growth of tumors to a greater extent than did Ad.5/3-mda-7. In summation, our data demonstrates that HDACIs enhance MDA-7/IL-24-mediated toxicity and tumor specific adenoviral delivery and viral replication of mda-7/IL-24 is an effective pre-clinical renal carcinoma therapeutic.

MDA-7/IL-24 suppresses tumor adhesion and invasive potential in hepatocellular carcinoma cell lines

Melanoma differentiation associated gene-7 (MDA-7)/interleukin‑24 (IL-24) has been considered as a tumor-suppressor gene, which suppresses the growth and induces the apoptosis of cancer cells. In the present study, we investigated the effect and mechanisms of MDA-7/IL-24 regarding the inhibition of metastasis of HepG2 and BEL-7402 human hepatocellular carcinoma (HCC) cells in vitro. We established MDA-7/IL-24-overexpressing HepG2 and BEL-7402 cell lines and found that MDA-7/IL-24 overexpression inhibited tumor cell adhesion and invasion, and induced G2/M arrest in tumor cells. To explore its mechanism of action, western blotting and real-time-PCR assay were used to investigate the expression of E-cadherin, CD44, ICAM-1, matrix metalloproteinase (MMP)-2 and -9, CyclinB, Twist, survivin, p-ERK and p-Akt. ELISA assay was used to measure the secretion of TGF-β, and a reporter gene assay was used to detected the transcriptional activity of NF-κB and AP-1 in HepG2 and BEL-7402 cells. The results showed that MDA-7/IL-24 overexpression decreased the expression of CD44, ICAM-1, MMP-2/-9, CyclinB, Twist, survivin, TGF-β and p-Akt, transcriptional activity of NF-κB, and increased the expression of E-cadherin and p-ERK and transcriptional activity of AP-1 in HepG2 and BEL-7402 cells. Our results revealed that MDA-7/IL-24 mediated the inhibition of adhesion and invasion in HepG2 and BEL-7402 cells by suppressing metastasis-related gene expression. Thus, MDA-7/IL-24 may be used as a novel cancer-suppressor gene for the therapy of human HCC.

Cancer targeting gene-viro-therapy for pancreatic cancer using oncolytic adenovirus ZD55-IL-24 in immune-competent mice

Cancer targeting gene-viro-therapy (CTGVT) may prove to be an effective treatment for pancreatic cancer (PC). This study was intended to explore the anti-tumor effect of ZD55-IL-24 (oncolytic adenovirus ZD55 harboring IL-24) on PC in immune-competent mice. The expression of gene harbored by oncolytic adenovirus ZD55 in PC cells was detected by reporter-gene assays. The in vitro anti PC ability of ZD55-IL-24 was tested by MTT, crystal violet staining and apoptosis assays. The in vivo anti PC effect of ZD55-IL-24 was further observed in an immune-competent mice model by detecting anti-tumor immunity and induction of apoptosis. The expression of gene harbored by ZD55 in PC cells was significantly higher than that harbored by the replicated-deficient adenovirus, and the amount of gene expression was time-dependent and dose-dependent. Both ZD55-IL-24 and ZD55 inhibited PC cells growth, but the anti-tumor effect of ZD55-IL-24 was significantly stronger than that of ZD55, and the ability of ZD55-IL-24 in inducing PC apoptosis was significantly stronger than that of ZD55. The tumor-forming rate of group ZD55-IL-24 was the lowest, and the tumor-growing rate was also significantly lower than that of group ZD55 in immune-competent PC models. Moreover, ZD55-IL-24 mediated more anti-cancer immunity effects by induction of stronger T-lymphocytes response to PC cells, higher levels of γ-IFN and IL-6 cytokines. ZD55-IL-24-mediated CTGVT could inhibit PC growth not only by inducing oncolysis and apoptosis but enhancing the anti-cancer immune effects by inducing T cell response to PC and up-regulating γ-IFN and IL-6 cytokine in immune-competent mice. This may serve as a candidate therapeutic approach for the treatment of PC.

Histone deacetylase inhibitors interact with melanoma differentiation associated-7/interleukin-24 to kill primary human glioblastoma cells

We presently demonstrate that histone deacetylase inhibitors (HDACIs) enhance toxicity of melanoma differentiation-associated gene-7/interleukin 24 (mda-7/IL-24) in invasive primary human glioblastoma multiforme (GBM) cells. Additionally, a method is described to augment the efficacy of adenoviral delivery of mda-7/IL-24 in these cells. HDACIs synergized with melanoma differentiation-associated (MDA)-7/IL-24 killing GBM cells. Enhanced lethality correlated with increased autophagy that was dependent on the expression of ceramide synthase 6. HDACIs interacted with MDA-7/IL-24 prolonging generation of reactive oxygen species and Ca(2+). Quenching of reactive oxygen species and Ca(2+) blocked HDACI and MDA-7/IL-24 killing. In vivo MDA-7/IL-24 prolonged the survival of animals carrying orthotopic tumors, and HDACIs enhanced survival further. A serotype 5/3 adenovirus more effectively delivers mda-7/IL-24 to GBM tumors than a serotype 5 virus. Hence, we constructed a serotype 5/3 adenovirus that conditionally replicates in tumor cells expressing MDA-7/IL-24, in which the adenoviral early region 1A (E1A) gene was driven by the cancer-specific promoter progression elevated gene-3 [Ad.5/3 (INGN 241)-PEG-E1A-mda-7; also called Ad.5/3-CTV (cancer terminator virus)]. Ad.5/3-CTV increased the survival of mice carrying GBM tumors to a significantly greater extent than did a nonreplicative virus Ad.5/3-mda-7. Ad.5/3-CTV exhibited no toxicity in the brains of Syrian hamsters. Collectively our data demonstrate that HDACIs enhance MDA-7/IL-24 lethality, and adenoviral delivery of mda-7/IL-24 combined with tumor-specific viral replication is an effective preclinical GBM therapeutic.

Critical role of lysine 123 in the ubiquitin-mediated degradation of MDA-7/IL-24

Melanoma differentiation-associated gene-7/interleukin-24 (MDA-7/IL-24) uniquely takes on multiple anticancer functions, such as direct tumor cell cytotoxicity, immune stimulation, and antiangiogenic activities. MDA-7/IL-24 protein levels depend on proteasome degradation. Western blotting and coimmunoprecipitation analyses verified that the MDA-7/IL-24 protein was ubiquitinated and degraded by the 26S proteasome in Hela cells, which was confirmed by protein accumulation treated with proteasome inhibitor MG132. MDA-7/IL-24 contains 10 lysine sites: K63, K69, K78, K119, K123, K136, K179, K189, K203, and K206. Site-directed mutagenesis in these sites reveals that lysine 123 is the major internal lysine involvement of MDA-7/IL-24 ubiquitination. Our results further demonstrated that the mutation of lysine 123 to arginine led to the inhibition of ubiquitin-mediated degradation and the recovery of MDA-7/IL-24 protein level. At the same time, the apoptosis-inducing activity of K123R mutant was obviously stronger than wild-type MDA-7/IL-24 detected by 4'-6-diamidino-2-phenylindole (DAPI) assay and annexin V analysis. In addition, K123R mutant tilted the balance between antiapoptotic protein Bcl-2 and proapoptotic protein Bax, which subsequently induced the cleavage of caspase signaling cascade and initiated cell apoptosis. Together, lysine 123 is mainly implicated in the ubiquitination and degradation of MDA-7/IL-24. Inhibition of degradation and ubiquitination of MDA-7/IL-24 through mutation of lysine 123 result in enhanced stability of MDA-7/IL-24 and exhibits persistent tumor suppression activity compared with the wild type.

Synergistic antitumor effect of TRAIL and IL-24 with complete eradication of hepatoma in the CTGVT-DG strategy

The ZD55-tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and ZD55-interleukin (IL)-24 were constructed by inserting TRAIL or IL-24 gene separately into the oncolytic adenovirus named ZD55 (with adenovirus E1B-55kD deletion). The resulting ZD55-TRAIL and ZD55-IL-24 were used in combination to treat xenograft tumors in nude mice model. The results showed that it can not only completely eliminate BEL7404 hepatoma xenograft but also have excellent antitumor effect against gaster, lung, prostate, and breast carcinomas. It was also found that ZD55-TRAIL could not only suppress the tumor growth promoting effect by ZD55-IL-24 at lower dosage, but also substantially reduce the cancer cell viability in their combined use. This is because ZD55-IL-24 and ZD55-TRAIL could mutually enhance each other's antitumor effect greatly. All these findings conspicuously showed the synergistic antitumor effect of TRAIL and IL-24, which is also the reason for the antitumor effect by the combined use of TRAIL and IL-24 in vitro and also in vivo.

MDA-7/IL-24 induces Bcl-2 denitrosylation and ubiquitin-degradation involved in cancer cell apoptosis

MDA-7/IL-24 was involved in the specific cancer apoptosis through suppression of Bcl-2 expression, which is a key apoptosis regulatory protein of the mitochondrial death pathway. However, the underlying mechanisms of this regulation are unclear. We report here that tumor-selective replicating adenovirus ZD55-IL-24 leads to Bcl-2 S-denitrosylation and concomitant ubiquitination, which take part in the 26S proteasome degradation. IL-24-siRNA completely blocks Bcl-2 ubiquitination via reversion of Bcl-2 S-denitrosylation and protects it from proteasomal degradation which confirmed the significant role of MDA-7/IL-24 in regulating posttranslational modification of Bcl-2 in cancer cells. Nitric oxide (NO) is a key regulator of protein S-nitrosylation and denitrosylation. The NO donor, sodium nitroprusside (SNP), down-regulates Bcl-2 S-denitrosylation, attenuates Bcl-2 ubiquitination and subsequently counteracts MDA-7/IL-24 induced cancer cell apoptosis, whereas NO inhibitor 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxy-3-oxide (PTIO) shows the opposite effect. At the same time, these NO modulators fail to affect Bcl-2 phosphorylation, suggesting that NO regulates Bcl-2 stability in a phosphorylation-independent manner. In addition, Bcl-2 S-nitrosylation reduction induced by ZD55-IL-24 was attributed to both iNOS decrease and TrxR1 increase. iNOS-siRNA facilitates Bcl-2 S-denitrosylation and ubiquitin-degradation, whereas the TrxR1 inhibitor auranofin prevents Bcl-2 from denitrosylation and ubiquitination, thus restrains the caspase signal pathway activation and subsequent cancer cell apoptosis. Taken together, our studies reveal that MDA-7/IL-24 induces Bcl-2 S-denitrosylation via regulation of iNOS and TrxR1. Moreover, denitrosylation of Bcl-2 results in its ubiquitination and subsequent caspase protease family activation, as a consequence, apoptosis susceptibility. These findings provide a novel insight into MDA-7/IL-24 induced growth inhibition and carcinoma apoptosis.

Enhanced delivery of mda-7/IL-24 using a serotype chimeric adenovirus (Ad.5/3) in combination with the Apogossypol derivative BI-97C1 (Sabutoclax) improves therapeutic efficacy in low CAR colorectal cancer cells

Adenovirus (Ad)-based gene therapy represents a potentially viable strategy for treating colorectal cancer. The infectivity of serotype 5 adenovirus (Ad.5), routinely used as a transgene delivery vector, is dependent on Coxsackie-adenovirus receptors (CAR). CAR expression is downregulated in many cancers thus preventing optimum therapeutic efficiency of Ad.5-based therapies. To overcome the low CAR problem, a serotype chimerism approach was used to generate a recombinant Ad (Ad.5/3) that is capable of infecting cancer cells via Ad.3 receptors in a CAR-independent manner. We evaluated the improved transgene delivery and efficacy of Ad.5/3 recombinant virus expressing melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24), an effective wide-spectrum cancer-selective therapeutic. In low CAR human colorectal cancer cells RKO, wild-type Ad.5 virus expressing mda-7/IL-24 (Ad.5-mda-7) failed to infect efficiently resulting in lack of expression of MDA-7/IL-24 or induction of apoptosis. However, a recombinant Ad.5/3 virus expressing mda-7/IL-24 (Ad.5/3-mda-7) efficiently infected RKO cells resulting in higher MDA-7/IL-24 expression and inhibition of cell growth both in vitro and in nude mice xenograft models. Addition of the novel Bcl-2 family pharmacological inhibitor Apogossypol derivative BI-97C1 (Sabutoclax) significantly augmented the efficacy of Ad.5/3-mda-7. A combination regimen of suboptimal doses of Ad.5/3-mda-7 and BI-97C1 profoundly enhanced cytotoxicity in RKO cells both in vitro and in vivo. Considering the fact that Ad.5-mda-7 has demonstrated significant objective responses in a Phase I clinical trial for advanced solid tumors, Ad.5/3-mda-7 alone or in combination with BI-97C1 would be predicted to exert significantly improved therapeutic efficacy in colorectal cancer patients.

Enhanced apoptosis-inducing function of MDA-7/IL-24 RGD mutant via the increased adhesion to tumor cells

Melanoma differentiation-associated gene-7 (mda-7)/interleukin-24 (IL-24) has shown potent tumor cell apoptosis inducing capacity in multiple cancers. However, the apoptosis induction capacity of mda-7/IL-24 was low and directly correlated with the adhesion to tumor cells.Cell adhesion molecule integrin α(v)β(3) expressed on the surface of several types of solid tumor cells, and they bind to arginine-glycine-aspartic acid (RGD) which enhanced the adhesion to tumor cells. This rout was exploited to construct a tumor-targeting gene RGD-IL-24 which can express RGD-MDA-7/IL-24 protein that includes the cell adhesive sequence (164)Arg-(165)Gly-(166)Asp (A Glycine residue was inserted into the recombinant MDA-7/IL-24 between Arg164 and Asp165 to form a RGD motif). We successfully got the MDA-7/IL-24 mutant by overlapping polymerase chain reaction (PCR) and evaluated its therapeutic efficacy for tumor cell lines MCF-7, HeLa, HepG2, and normal human lung fibroblast (NHLF) line. And we found that the expression of pCDNA3.1/RGD-IL-24 was same to the expression of pCDNA3.1/IL-24. The RGD-IL-24 enhanced the apoptosis-inducing function in tumor cells, but not in normal cells. In tumor cell lines, the apoptosis-inducing activities of RGD-IL-24 was significantly higher than IL-24 detecting by MTT assay, Annexin V, and Hoechst 33258 analysis. Further, pCDNA3.1/RGD-IL-24 showed a significant increase in the ratio of pro-apoptotic (bax) to anti-apoptotic (bcl-2) proteins in tumor cell lines, but not in NHLF cell line. Together, these results suggest that RGD-IL-24 can enhance the apoptosis of tumor cells and may provide a promising drug in tumor therapy.

Recombinant adenovirus vector-mediated human MDA-7 gene transfection suppresses hepatocellular carcinoma growth in a mouse xenograft model

Hepatocellular carcinoma is one of the most common tumors in the world. The purpose of the present study was to investigate the inhibitory effects of adenoviral transduction of human melanoma differentiation-associated gene-7 (MDA-7) gene on hepatocellular carcinoma, so as to provide a theoretical basis for gene therapy of the disease. The human MDA-7 gene was cloned into replication-defective adenovirus specific to HepG2 cells using recombinant virus technology. RT-PCR and Western blotting assays were used to determine the expression of human MDA-7 mRNA and MDA-7 protein in HepG2 cells in vitro. Induction of apoptosis by overexpression of the human MDA-7 gene was determined by flow cytometry. In-vivo efficacy of adenoviral delivery of the human MDA-7 gene was assessed in nude mice bearing HepG2 cell lines in vivo by determining inhibition of tumor growth, VEGF and CD34 expression, and microvascular density (MVD). The results showed that AdGFP/MDA-7 induced apoptosis of HepG2 cells in vitro and significantly inhibited tumor growth in vivo (P < 0.05). The intratumoral MVD decreased significantly in the treated tumors (P < 0.05). We conclude the recombination adenovirus AdGFP/MDA-7 can effectively express biologically active human MDA-7, which leads to inhibition of hepatocellular carcinoma growth.

mda-7/IL-24: a unique member of the IL-10 gene family promoting cancer-targeted toxicity

Melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) is a unique member of the IL-10 gene family that displays nearly ubiquitous cancer-specific toxicity, with no harmful effects toward normal cells or tissues. mda-7/IL-24 was cloned from human melanoma cells by differentiation induction subtraction hybridization (DISH) and promotes endoplasmic reticulum (ER) stress culminating in apoptosis or toxic autophagy in a broad-spectrum of human cancers, when assayed in cell culture, in vivo in human tumor xenograft mouse models and in a Phase I clinical trial in patients with advanced cancers. This therapeutically active cytokine also induces indirect antitumor activity through inhibition of angiogenesis, stimulation of an antitumor immune response, and sensitization of cancer cells to radiation-, chemotherapy- and antibody-induced killing.

Developing an effective gene therapy for prostate cancer: New technologies with potential to translate from the laboratory into the clinic

Prostate cancer is the second leading cause of cancer-related deaths in men in the U.S. At present, no single or combination therapy has shown efficacy in decreasing disease progression in patients with metastatic disease. A potentially viable approach for treating late-stage prostate cancer is gene therapy. Adenoviruses (Ad) are the most commonly used mode of gene delivery, but progress using this vector has been hampered by concerns over the safety and practicality of viruses including conditionally replicating Ads (CRAds), particularly for intravenous delivery, and the inefficiency of non-viral transfection techniques. Major challenges for effective gene therapy using Ads are the limited infectivity of regular Ad serotype 5 (Ad5) and the inability to specifically deliver the therapeutic directly into diseased tissue without trapping in the liver or elimination by the immune system. The shortcoming in using Ad5 is mostly attributed to a reduction in Coxsackie-adenovirus receptors (CAR) on the surface of cancer cells, which can be mitigated by generating tropism-modified Ads permitting CAR-independent infection of tumor cells. The limitations of systemic gene delivery can now be overcome by using a novel targeted-delivery approach such as ultrasound (US) contrast agents (microbubbles) to deliver effective therapeutic reagents, Ads, or recombinant proteins, combined with ultrasound-targeted microbubble destruction (UTMD), to develop a site-specific therapy in immune competent transgenic mouse models. These unique strategies for enhancing the efficacy of gene therapy provide a direct path to translation from the laboratory into the clinic for developing an effective gene therapy of prostate cancer.

Enhancing mda-7/IL-24 therapy in renal carcinoma cells by inhibiting multiple protective signaling pathways using sorafenib and by Ad.5/3 gene delivery

We have determined whether an adenovirus that comprises the tail and shaft domains of a serotype 5 virus and the knob domain of a serotype 3 virus expressing MDA-7/IL-24, Ad.5/3-mda-7, more effectively infects and kills renal carcinoma cells (RCCs) compared to a serotype 5 virus, Ad.5-mda-7. RCCs are a tumor cell type that generally does not express the receptor for the type 5 adenovirus; the coxsackie and adenovirus receptor (CAR). Ad.5/3-mda-7 infected RCCs to a much greater degree than Ad.5-mda-7. MDA-7/IL-24 protein secreted from Ad.5/3-mda-7-infected RCCs induced MDA-7/IL-24 expression and promoted apoptosis in uninfected "bystander" RCCs. MDA-7/IL-24 killed both infected and bystander RCCs via CD95 activation. Knockdown of intracellular MDA-7/IL-24 in uninfected RCCs blocked the lethal effects of conditioned media. Infection of RCC tumors in one flank, with Ad.5/3-mda-7, suppressed growth of infected tumors and reduced the growth rate of uninfected tumors implanted on the opposite flank. The toxicity of the serotype 5/3 recombinant adenovirus to express MDA-7/IL-24 was enhanced by combined molecular or small molecule inhibition of MEK1/2 and PI3K; inhibition of mTOR, PI3K and MEK1/2; or use of the multi-kinase inhibitor sorafenib. In RCCs, combined inhibition of cytoprotective cell signaling pathways enhanced the MDA-7/IL-24-induction of CD95 activation, with greater mitochondrial dysfunction due to loss of MCL-1 and BCL-XL expression, and tumor cell death. Treatment of RCC tumors in vivo with sorafenib also enhanced Ad.5/3-mda-7 toxicity and prolonged animal survival. Future combinations of these approaches hold promise for developing a more effective therapy for kidney cancer.

A serotype 5/3 adenovirus expressing MDA-7/IL-24 infects renal carcinoma cells and promotes toxicity of agents that increase ROS and ceramide levels

Agents that generate reactive oxygen species (ROS) are recognized to enhance MDA-7/IL-24 lethality. The present studies focused on clarifying how such agents enhanced MDA-7/IL-24 toxicity in renal cell carcinoma cells (RCCs). Infection of RCCs with a tropism-modified serotype 5/3 adenovirus expressing MDA-7/IL-24 (Ad.5/3-mda-7) caused plasma membrane clustering of CD95 and CD95 association with pro-caspase 8, effects that were enhanced by combined exposure to 17-N-allylamino-17-demethoxygeldanamycin (17AAG), As(2)O(3), or fenretinide and that correlated with enhanced cell killing. Knockdown of CD95 or expression of cellular FADD (Fas-associated protein with death domain)-like interleukin-1β-converting enzyme inhibitory protein, short form (c-FLIP-s) blocked enhanced killing. Inhibition of ROS generation, elevated cytosolic Ca(2+), or de novo ceramide synthesis blocked Ad.5/3-mda-7 ± agent-induced CD95 activation and the enhancement of apoptosis. Ad.5/3-mda-7 increased ceramide levels in a PERK-dependent fashion that were responsible for elevated cytosolic Ca(2+) levels that promoted ROS generation; 17AAG did not further enhance cytokine-induced ceramide generation. In vivo, infection of RCC tumors with Ad.5/3-mda-7 suppressed the growth of infected tumors that was enhanced by exposure to 17AAG. Our data indicate that in RCCs, Ad.5/3-mda-7-induced ceramide generation plays a central role in tumor cell killing and inhibition of multiple signaling pathways may have utility in promoting MDA-7/IL-24 lethality in renal cancer.

The role of Akt activation in the response to chemotherapy in pancreatic cancer

The PI3K/Akt signaling pathway is constitutively activated in some pancreatic cancers; when activated, it inhibits chemotherapy-mediated apoptosis. We examined whether Akt activity correlates with apoptotic resistance to chemotherapy in pancreatic cancer.

MATERIALS AND METHODS

A panel of human pancreatic cancer cells was evaluated for basal Akt activity as well as response to three chemotherapies. Chemotherapy-induced cell death was evaluated following either up- or down-regulation of Akt activity. Evaluation of phosphorylation of p21Cip/Waf1, a downstream target of Akt, was also evaluated.

RESULTS

There was a broad distribution among pancreatic cancer cell lines by Akt activity, as well as sensitivity to the three chemotherapeutic agents with no apparent correlation. Phosphorylation of p21Cip/Waf1, but not change in total levels, correlated with the chemosensitizing effect of Akt inhibition to paclitaxel.

CONCLUSIONS

Basal Akt activity does not appear to be a useful predictor for selection of pancreatic cancers in targeting Akt to broadly induce chemosensitivity.

MDA-7/IL-24 as a cancer therapeutic: from bench to bedside

The novel cytokine melanoma differentiation associated gene-7 (mda-7) was identified by subtractive hybridization in the mid-1990s as a protein whose expression increased during the induction of terminal differentiation, and that was either not expressed or was present at low levels in tumor cells compared with non-transformed cells. On the basis of conserved structure, chromosomal location and cytokine-like properties, MDA-7, has now been classified as a member of the expanding interleukin (IL)-10 gene family and designated as MDA-7/IL-24. Multiple studies have shown that the expression of MDA-7/IL-24 in a wide variety of tumor cell types, but not in the corresponding equivalent non-transformed cells, causes their growth arrest and ultimately cell death. In addition, MDA-7/IL-24 has been noted to be a radiosensitizing cytokine, which is partly because of the generation of reactive oxygen species and ceramide that cause endoplasmic reticulum stress. Phase I clinical trial data has shown that a recombinant adenovirus expressing MDA-7/IL-24 [Ad.mda-7 (INGN-241)] was safe and had measurable tumoricidal effects in over 40% of patients, which strongly argues that MDA-7/IL-24 may have significant therapeutic value. This review describes what is known about the impact of MDA-7/IL-24 on tumor cell biology and its potential therapeutic applications.

Enhanced cytotoxicity of IL-24 gene-modified dendritic cells co-cultured with cytokine-induced killer cells to hepatocellular carcinoma cells

As a novel human cytokine found recently, IL-24 could selectively kill tumor cells by multiple ways. Dendritic cells (DCs) are the major antigen-presenting cells. Recent studies have revealed that IL-24 can promote the antigen-presenting function of DCs. In this study, we evaluated the antitumor effect and mechanism of co-cultured cytokine-induced killer (CIK) cells and autologous DCs modified with IL-24 gene on hepatocellular carcinoma (HCC) cells. DCs and CIK cells were prepared routinely from human peripheral blood mononuclear cells. Recombinant adenovirus AdVGFP/IL-24 (Ad-IL24) was constructed expressing IL-24. IL-24 gene was transduced into DCs via Ad-IL24, the cells obtained were named DC-IL-24. We demonstrated that the expression rates of CD80, CD83, CD1a, HLA-DR, CD40, CXCR4 on DC-IL-24 were significantly increased compared with those of the control group. DC-IL-24 produced markedly higher levels of IL-24, IL-12 and TNF-alpha as compared with those of DCs. On comparison with non-transfected DCs co-cultured with CIK cells, transfected DCs co-cultured with CIK cells had a significant higher lytic activity against SMMC7721 cells, a HCC cell line.

Enhanced cytotoxicity of IL-24 gene-modified dendritic cells co-cultured with cytokine-induced killer cells to hepatocellular carcinoma cells

As a novel human cytokine found recently, IL-24 could selectively kill tumor cells by multiple ways. Dendritic cells (DCs) are the major antigen-presenting cells. Recent studies have revealed that IL-24 can promote the antigen-presenting function of DCs. In this study, we evaluated the antitumor effect and mechanism of co-cultured cytokine-induced killer (CIK) cells and autologous DCs modified with IL-24 gene on hepatocellular carcinoma (HCC) cells. DCs and CIK cells were prepared routinely from human peripheral blood mononuclear cells. Recombinant adenovirus AdVGFP/IL-24 (Ad-IL24) was constructed expressing IL-24. IL-24 gene was transduced into DCs via Ad-IL24, the cells obtained were named DC-IL-24. We demonstrated that the expression rates of CD80, CD83, CD1a, HLA-DR, CD40, CXCR4 on DC-IL-24 were significantly increased compared with those of the control group. DC-IL-24 produced markedly higher levels of IL-24, IL-12 and TNF-alpha as compared with those of DCs. On comparison with non-transfected DCs co-cultured with CIK cells, transfected DCs co-cultured with CIK cells had a significant higher lytic activity against SMMC7721 cells, a HCC cell line.

Inhibition of multiple protective signaling pathways and Ad.5/3 delivery enhances mda-7/IL-24 therapy of malignant glioma

We have explored the mechanism by which inhibition of multiple cytoprotective cell-signaling pathways enhance melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) toxicity toward invasive primary human glioblastoma multiforme (GBM) cells, and whether improving adenoviral infectivity/delivery of mda-7/IL-24 enhances therapeutic outcome in animals containing orthotopic xenografted GBM cells. The toxicity of a serotype 5 recombinant adenovirus to express MDA-7/IL-24 (Ad.5-mda-7) was enhanced by combined molecular or small molecule inhibition of mitogen-activated extracellular regulated kinase (MEK)1/2 and phosphatidyl inositol 3-kinase (PI3K) or AKT; inhibition of mammalian target of rapamycin (mTOR) and MEK1/2; and the HSP90 inhibitor 17AAG. Molecular inhibition of mTOR/PI3K/MEK1 signaling in vivo also enhanced Ad.5-mda-7 toxicity. In GBM cells of diverse genetic backgrounds, inhibition of cytoprotective cell-signaling pathways enhanced MDA-7/IL-24-induced autophagy, mitochondrial dysfunction and tumor cell death. Due partly to insufficient adenovirus serotype 5 gene delivery this therapeutic approach has shown limited success in GBM. To address this problem, we employed a recombinant adenovirus that comprises the tail and shaft domains of a serotype 5 virus and the knob domain of a serotype 3 virus expressing MDA-7/IL-24, Ad.5/3-mda-7. Ad.5/3-mda-7 more effectively infected and killed GBM cells in vitro and in vivo than Ad.5-mda-7. Future combinations of these approaches hold promise for developing an effective therapy for GBM.

Anticancer genes: inducers of tumour-specific cell death signalling

Recent studies have revealed a new class of genes encoding proteins with specific anticancer activity. Upon ectopic expression, these factors cause cell death specifically in tumour cells by apoptosis, autophagy or mitotic catastrophe, yet normal cells are spared. Some of these genes or their encoded proteins are in clinical development and show promising results, and their signalling pathways are currently under intense investigation. Defining these genes as anticancer genes, we review what is known about their functions, the specific cell death signals they induce and the status of cancer therapy approaches that emulate their function. Systematic screening for such anticancer genes might lead to the identification of a repertoire of signalling pathways directed against cellular alterations that are specific for tumour cells.

OSU-03012 enhances Ad.7-induced GBM cell killing via ER stress and autophagy and by decreasing expression of mitochondrial protective proteins

The present studies focused on determining whether the autophagy-inducing drug OSU-03012 (AR-12) could enhance the toxicity of recombinant adenoviral delivery of melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) in glioblastoma multiforme (GBM) cells. The toxicity of a recombinant adenovirus to express MDA-7/IL-24 (Ad.mda-7) was enhanced by OSU-03012 in a diverse panel of primary human GBM cells. The enhanced toxicity correlated with reduced ERK1/2 phosphorylation and expression of MCL-1 and BCL-XL, and was blocked by molecular activation of ERK1/2 and by inhibition of the intrinsic, but not the extrinsic, apoptosis pathway.  Both OSU-03012 and expression of MDA-7/IL-24 increased phosphorylation of PKR-like endoplasmic reticulum kinase (PERK) that correlated with increased levels of autophagy and expression of dominant negative PERK blocked autophagy induction and tumor cell death. Knockdown of ATG5 or Beclin1 suppressed OSU-03012 enhanced MDA-7/IL-24-induced autophagy and blocked the lethal interaction between the two agents. Ad.mda-7-infected GBM cells secreted MDA-7/IL-24 into the growth media and this conditioned media induced expression of MDA-7/IL-24 in uninfected GBM cells. OSU-03012 interacted with conditioned media to kill GBM cells and knockdown of MDA-7/IL-24 in these cells suppressed tumor cell killing. Collectively, our data demonstrate that the induction of autophagy and mitochondrial dysfunction by a combinatorial treatment approach represents a potentially viable strategy to kill primary human GBM cells.

Enhanced delivery of mda-7/IL-24 using a serotype chimeric adenovirus (Ad.5/3) improves therapeutic efficacy in low CAR prostate cancer cells

Gene therapy is being examined as a potential strategy for treating prostate cancer. Serotype 5 adenovirus (Ad.5) is routinely used as a vector for transgene delivery. However, the infectivity of Ad.5 is dependent on Coxsackie-adenovirus receptors (CARs); many tumor types show a reduction in this receptor in vivo, thereby limiting therapeutic gene transduction. Serotype chimerism is one approach to circumvent CAR deficiency; this strategy is used to generate an Ad.5/3-recombinant Ad that infects cancer cells through Ad.3 receptors in a CAR-independent manner. In this report, the enhanced transgene delivery and efficacy of Ad.5/3-recombinant virus was evaluated using an effective wide-spectrum anticancer therapeutic melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24). Our data show that in low CAR human prostate cancer cells (PC-3), a recombinant Ad.5/3 virus delivering mda-7/IL-24 (Ad.5/3-mda-7) is more efficacious than an Ad.5 virus encoding mda-7/IL-24 (Ad.5-mda-7) in infecting tumor cells, expressing MDA-7/IL-24 protein, inducing cancer-specific apoptosis, inhibiting in vivo tumor growth and exerting an antitumor 'bystander' effect in a nude mouse xenograft model. Considering the fact that Ad.5-mda-7 has shown significant objective responses in a phase I clinical trial for solid tumors, Ad.5/3-mda-7 is predicted to exert enhanced therapeutic benefit in patients with prostate cancer.

PERK-dependent regulation of ceramide synthase 6 and thioredoxin play a key role in mda-7/IL-24-induced killing of primary human glioblastoma multiforme cells

Melanoma differentiation associated gene-7(mda-7) encodes IL-24, a cytokine that can selectively trigger apoptosis in transformed cells. Recombinant mda-7 adenovirus (Ad.mda-7) effectively kills glioma cells, offering a novel gene therapy strategy to address deadly brain tumors. In this study, we defined the proximal mechanisms by which Ad-mda-7 kills glioma cells. Key factors implicated included activation of the endoplasmic reticulum stress kinase protein kinase R-like endoplasmic reticulum kinase (PERK), Ca(++) elevation, ceramide generation and reactive oxygen species (ROS) production. PERK inhibition blocked ceramide or dihydroceramide generation, which were critical for Ca(++) induction and subsequent ROS formation. Activation of autophagy and cell death relied upon ROS formation, the inhibition of which ablated Ad.mda-7-killing activity. In contrast, inhibiting TRX induced by Ad.MDA-7 enhanced tumor cytotoxicity and improved animal survival in an orthotopic tumor model. Our findings indicate that mda-7/IL-24 induces an endoplasmic reticulum stress response that triggers production of ceramide, Ca(2+), and ROS, which in turn promote glioma cell autophagy and cell death.

Cisplatin enhances protein kinase R-like endoplasmic reticulum kinase- and CD95-dependent melanoma differentiation-associated gene-7/interleukin-24-induced killing in ovarian carcinoma cells

Melanoma differentiation associated gene-7/interleukin 24 (mda-7/IL-24) is a unique interleukin (IL)-10 family cytokine displaying selective apoptosis-inducing activity in transformed cells without harming normal cells. The present studies focused on defining the mechanism(s) by which recombinant adenoviral delivery of MDA-7/IL-24 inhibits cell survival of human ovarian carcinoma cells. Expression of MDA-7/IL-24 induced phosphorylation of protein kinase R-like endoplasmic reticulum kinase (PERK) and eukaryotic initiation factor2alpha (eIF2alpha). In a PERK-dependent fashion, MDA-7/IL-24 reduced ERK1/2 and AKT phosphorylation and activated c-Jun NH(2)-terminal kinase (JNK) 1/2 and p38 mitogen-activated protein kinase (MAPK). MDA-7/IL-24 reduced MCL-1 and BCL-XL and increased BAX levels via PERK signaling; cell-killing was mediated via the intrinsic pathway, and cell killing was primarily necrotic as judged using Annexin V/propidium iodide staining. Inhibition of p38 MAPK and JNK1/2 abolished MDA-7/IL-24 toxicity and blocked BAX and BAK activation, whereas activation of mitogen-activated extracellular-regulated kinase (MEK) 1/2 or AKT suppressed enhanced killing and JNK1/2 activation. MEK1/2 signaling increased expression of the MDA-7/IL-24 and PERK chaperone BiP/78-kDa glucose regulated protein (GRP78), and overexpression of BiP/GRP78 suppressed MDA-7/IL-24 toxicity. MDA-7/IL-24-induced LC3-green fluorescent protein vesicularization and processing of LC3; and knockdown of ATG5 suppressed MDA-7/IL-24-mediated toxicity. MDA-7/IL-24 and cisplatin interacted in a greater than additive fashion to kill tumor cells that was dependent on a further elevation of JNK1/2 activity and recruitment of the extrinsic CD95 pathway. MDA-7/IL-24 toxicity was enhanced in a weak additive fashion by paclitaxel; paclitaxel enhanced MDA-7/IL-24 + cisplatin lethality in a greater than additive fashion via BAX. Collectively, our data demonstrate that MDA-7/IL-24 induces an endoplasmic reticulum stress response that activates multiple proapoptotic pathways, culminating in decreased ovarian tumor cell survival.

MDA-7/IL-24-induced cell killing in malignant renal carcinoma cells occurs by a ceramide/CD95/PERK-dependent mechanism

Melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) is a novel cytokine displaying selective apoptosis-inducing activity in transformed cells without harming normal cells. The present studies focused on clarifying the mechanism(s) by which glutathione S-transferase (GST)-MDA-7 altered cell survival of human renal carcinoma cells in vitro. GST-MDA-7 caused plasma membrane clustering of CD95 and the association of CD95 with procaspase-8. GST-MDA-7 lethality was suppressed by inhibition of caspase-8 or by overexpression of short-form cellular FLICE inhibitory protein, but only weakly by inhibition of cathepsin proteases. GST-MDA-7-induced CD95 clustering (and apoptosis) was blocked by knockdown of acidic sphingomyelinase or, to a greater extent, ceramide synthase-6 expression. GST-MDA-7 killing was, in parallel, dependent on inactivation of extracellular signal-regulated kinase 1/2 and on CD95-induced p38 mitogen-activated protein kinase and c-jun NH(2)-terminal kinase-1/2 signaling. Knockdown of CD95 expression abolished GST-MDA-7-induced phosphorylation of protein kinase R-like endoplasmic reticulum kinase. GST-MDA-7 lethality was suppressed by knockout or expression of a dominant negative protein kinase R-like endoplasmic reticulum kinase that correlated with reduced c-jun NH(2)-terminal kinase-1/2 and p38 mitogen-activated protein kinase signaling and maintained extracellular signal-regulated kinase-1/2 phosphorylation. GST-MDA-7 caused vacuolization of LC3 through a mechanism that was largely CD95 dependent and whose formation was suppressed by knockdown of ATG5 expression. Knockdown of ATG5 suppressed GST-MDA-7 toxicity. Our data show that in kidney cancer cells GST-MDA-7 induces ceramide-dependent activation of CD95, which is causal in promoting an endoplasmic reticulum stress response that activates multiple proapoptotic pathways to decrease survival.

Enhancement of tumor cell death by combining cisplatin with an oncolytic adenovirus carrying MDA-7/IL-24

AIM

The aim of this study was to creatively implement a novel chemo-gene-virotherapeutic strategy and further strengthen the antitumor effect in cancer cells by the combined use of ZD55-IL-24 and cisplatin.

METHODS

ZD55-IL-24 is an oncolytic adenovirus that harbors interleukin 24 (IL-24), which has a strong antitumor effect and was identified and evaluated by PCR, RT-PCR, and Western blot analysis. Enhancement of cancer cell death using a combination of ZD55-IL-24 and cisplatin was assessed in several cancer cell lines by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and cytopathic effect (CPE) assay. Apoptosis induction by treatment with ZD55-IL-24 and/or cisplatin was detected in BEL7404 and SMMC7721 by morphological evaluation, apoptotic cell staining, and flow cytometry analysis. In addition, negative effects on normal cells were evaluated in the L-02 cell line using the MTT assay, the CPE assay, morphological evaluation, apoptotic cell staining, and flow cytometry analysis.

RESULTS

The combination of ZD55-IL-24 and cisplatin, which is superior to ZD55-IL-24, cisplatin, and ZD55-EGFP, as well as ZD55-EGFP plus cisplatin, resulted in a significantly increased effect. Most importantly, conjugation of ZD55-IL-24 with cisplatin had toxic effects equal to that of cisplatin and did not have overlapping toxicities in normal cells.

CONCLUSION

This study showed that ZD55-IL-24 conjugated with cisplatin exhibited a remarkably increased cytotoxic and apoptosis-inducing effect in cancer cells and significantly reduced the toxicity in normal cells through the use of a reduced dose.

Chemoprevention by perillyl alcohol coupled with viral gene therapy reduces pancreatic cancer pathogenesis

Pancreatic cancer is one of the deadliest of cancers. Even with aggressive therapy, the 5-year survival rate is <5%, mandating development of more effective treatments. Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) shows potent antitumor activity against most cancers displaying safety with significant clinical efficacy. However, pancreatic cancer cells display inherent resistance to mda-7/IL-24 that is the result of a "protein translational block" of mda-7/IL-24 mRNA in these tumor cells. We now show that a dietary supplement perillyl alcohol (POH) has significant chemopreventive effects for pancreatic cancer and, when coupled with adenovirus-mediated mda-7/IL-24 gene therapy (Ad.mda-7), effectively eliminates s.c. and i.p. xenografts of human pancreatic cancer cells in nude mice, promoting enhanced survival. The combination of POH and Ad.mda-7 efficiently abrogates the mda-7/IL-24 protein translational block, resulting in MDA-7/IL-24 protein production and growth suppression. Of direct translational relevance, clinically achievable concentrations of POH with Ad.mda-7, both of which have been found safe and without toxic effects in human trials, were used. This novel and innovative approach combining a dietary agent and a virally delivered therapeutic cytokine provides a means of both preventing and treating human pancreatic cancer with significant clinical translational potential.