mda-7 gene transfer sensitizes breast carcinoma cells to chemotherapy, biologic therapies and radiotherapy: correlation with expression of bcl-2 family members

Regulation of IL-24/IL-20R2 complex formation using photocaged tyrosines and UV light

Human interleukin 24 (IL-24) is a multifunctional cytokine that represents an important target for autoimmune diseases and cancer. Since the biological functions of IL-24 depend on interactions with membrane receptors, on-demand regulation of the affinity between IL-24 and its cognate partners offers exciting possibilities in basic research and may have applications in therapy. As a proof-of-concept, we developed a strategy based on recombinant soluble protein variants and genetic code expansion technology to photocontrol the binding between IL-24 and one of its receptors, IL-20R2. Screening of non-canonical ortho-nitrobenzyl-tyrosine (NBY) residues introduced at several positions in both partners was done by a combination of biophysical and cell signaling assays. We identified one position for installing NBY, tyrosine70 of IL-20R2, which results in clear impairment of heterocomplex assembly in the dark. Irradiation with 365-nm light leads to decaging and reconstitutes the native tyrosine of the receptor that can then associate with IL-24. Photocaged IL-20R2 may be useful for the spatiotemporal control of the JAK/STAT phosphorylation cascade.

Adaptation process of engineered cell line FCHO/IL-24 stably secreted rhIL-24 in serum-free suspension culture

Interleukin-24 (IL-24) displays tumor cell-specific proliferation inhibition in vitro and in vivo. Recombinant human IL-24 (rhIL-24) has significantly higher activity, yet significantly lower expression level in mammalian cells than in bacteria. To further realize therapeutic potential of IL-24, we enhanced rhIL-24 expression in mammalian cell systems by adapting engineered Flp-In^TMCHO/IL-24 (FCHO/IL-24) cells (adherent cultured in Ham's F12 medium with 10% serum) to serum-free suspension culture. First, MTT assay showed that among four different media (F12, DMEM/F12, 1640 and DMEM), DMEM/F12 medium was the most suitable media for lower-serum adherent culture. Then, cells were adherently cultured in DMEM/F12 with serum concentration reduced from 10% to 0.5% in a gradient manner. Compared to cells in 10% serum, cells in 0.5% serum displayed significantly lower relative cell viability by 40%, increased G0/G1 phase arrest (8.5 ± 2.4%, p < 0.05), decreased supernatant rhIL-24 concentration by 73%, and altered metabolite profiles, such as glucose, lactate and ammonia concentration. Next, the cells were directly adapted to 0.5% serum suspension culture in 125 mL shake flask at 119 rpm with the optimal cell seeding density of 5 × 10⁵ cells/mL (3.3 times higher than that of adherent culture), under which the concentration of rhIL-24 in culture medium was stable at 3.5 ng/mL. Finally, cells adapted to 0.5% serum proliferated better in serum-free medium Eden™-B300S with higher rhIL-24 expression level compared to CDM4CHO. The successful adaptation of engineered cells FCHO/IL-24 laid foundation for adapting cells from adherent culture to suspension serum-free culture to mass produce rhIL-24 protein for therapeutic purposes.

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.

Therapeutic approaches targeting molecular signaling pathways common to diabetes, lung diseases and cancer

Diabetes mellitus (DM), is the most common metabolic disease and is characterized by sustained hyperglycemia. Accumulating evidences supports a strong association between DM and numerous lung diseases including chronic obstructive pulmonary disease (COPD), fibrosis, and lung cancer (LC). The global incidence of DM-associated lung disorders is rising and several ongoing studies, including clinical trials, aim to elucidate the molecular mechanisms linking DM with lung disorders, in particular LC. Several potential mechanisms, including hyperglycemia, hyperinsulinemia, glycation, inflammation, and hypoxia, are cited as plausible links between DM and LC. In addition, studies also propose a connection between the use of anti-diabetic medications and reduction in the incidence of LC. However, the exact cause for DM associated lung diseases especially LC is not clear and is an area under intense investigation. Herein, we review the biological links reported between DM and lung disorders with an emphasis on LC. Furthermore, we report common signaling pathways (eg: TGF-β, IL-6, HIF-1, PDGF) and miRNAs that are dysregulated in DM and LC and serve as molecular targets for therapy. Finally, we propose a nanomedicine based approach for delivering therapeutics (eg: IL-24 plasmid DNA, HuR siRNA) to disrupt signaling pathways common to DM and LC and thus potentially treat DM-associated LC. Finally, we conclude that the effective modulation of commonly regulated signaling pathways would help design novel therapeutic protocols for treating DM patients diagnosed with LC.

Engineering T Cells to Express Tumoricidal MDA-7/IL24 Enhances Cancer Immunotherapy

Antigen-specific immunotherapy can be limited by induced tumor immunoediting (e.g., antigen loss) or through failure to recognize antigen-negative tumor clones. Melanoma differentiation-associated gene-7/IL24 (MDA-7/IL24) has profound tumor-specific cytotoxic effects in a broad spectrum of cancers. Here we report the enhanced therapeutic impact of genetically engineering mouse tumor-reactive or antigen-specific T cells to produce human MDA-7/IL24. While mock-transduced T cells only killed antigen-expressing tumor cells, MDA-7/IL24-producing T cells destroyed both antigen-positive and negative cancer targets. MDA-7/IL24-expressing T cells were superior to their mock-engineered counterparts in suppressing mouse prostate cancer and melanoma growth as well as metastasis. This enhanced antitumor potency correlated with increased tumor infiltration and expansion of antigen-specific T cells as well as induction of a Th1-skewed immunostimulatory tumor environment. MDA-7/IL24-potentiated T-cell expansion was dependent on T-cell-intrinsic STAT3 signaling. Finally, MDA-7/IL24-modified T-cell therapy significantly inhibited progression of spontaneous prostate cancers in Hi-Myc transgenic mice. Taken together, arming T cells with tumoricidal and immune-potentiating MDA-7/IL24 confers new capabilities of eradicating antigen-negative cancer cell clones and improving T-cell expansion within tumors. This promising approach may be used to optimize cellular immunotherapy for treating heterogeneous solid cancers and provides a mechanism for inhibiting tumor escape. SIGNIFICANCE: This research describes a novel strategy to overcome the antigenic heterogeneity of solid cancers and prevent tumor escape by engineering T lymphocytes to produce a broad-spectrum tumoricidal agent.

Theranostic Tripartite Cancer Terminator Virus for Cancer Therapy and Imaging

Simple Summary

An optimum cancer therapeutic virus should embody unique properties, including an ability to: Selectively procreate and kill tumor but not normal cells; produce a secreted therapeutic molecule (with broad-acting anti-cancer effects on primary and distant metastatic cells because of potent “bystander” activity); and monitor therapy non-invasively by imaging primary and distant metastatic cancers. We previously created a broad-spectrum, cancer-selective and replication competent therapeutic adenovirus that embodies two of these properties, i.e., specifically reproduces in cancer cells and produces a therapeutic cytokine, MDA-7/IL-24, a “cancer terminator virus” (CTV). We now expand on this concept and demonstrate the feasibility of producing a tripartite CTV (TCTV) selectively expressing three genes from three distinct promoters that replicate in the cancer cells while producing MDA-7/IL-24 and an imaging gene (i.e., luciferase). This novel first-in-class tripartite “theranostic” TCTV expands the utility of therapeutic viruses to non-invasively image and selectively destroy primary tumors and metastases.

Abstract

Combining cancer-selective viral replication and simultaneous production of a therapeutic cytokine, with potent “bystander” anti-tumor activity, are hallmarks of the cancer terminator virus (CTV). To expand on these attributes, we designed a next generation CTV that additionally enables simultaneous non-invasive imaging of tumors targeted for eradication. A unique tripartite CTV “theranostic” adenovirus (TCTV) has now been created that employs three distinct promoters to target virus replication, cytokine production and imaging capabilities uniquely in cancer cells. Conditional replication of the TCTV is regulated by a cancer-selective (truncated PEG-3) promoter, the therapeutic component, MDA-7/IL-24, is under a ubiquitous (CMV) promoter, and finally the imaging capabilities are synchronized through another cancer selective (truncated tCCN1) promoter. Using in vitro studies and clinically relevant in vivo models of breast and prostate cancer, we demonstrate that incorporating a reporter gene for imaging does not compromise the exceptional therapeutic efficacy of our previously reported bipartite CTV. This TCTV permits targeted treatment of tumors while monitoring tumor regression, with potential to simultaneously detect metastasis due to the cancer-selective activity of reporter gene expression. This “theranostic” virus provides a new genetic tool for distinguishing and treating localized and metastatic cancers.

Interleukin (IL)-24: Reconfiguring the Tumor Microenvironment for Eliciting Antitumor Response

Interleukin (IL)-24 is a member of the IL-10 family of cytokines. Due to its unique ability to function as both a tumor suppressor and cytokine, IL-24-based cancer therapy has been developed for treating a broad spectrum of human cancers. Majority of the studies reported to date have focused on establishing IL-24 as a cancer therapeutic by primarily focusing on tumor cell killing. However, the ability of IL-24 treatment on modulating the tumor microenvironment and immune response is underinvestigated. In this article, we summarize the biological and functional properties of IL-24 and the benefits of applying IL-24-based therapy for cancer.

Mesenchymal stem cells derived from iPSCs expressing interleukin-24 inhibit the growth of melanoma in the tumor-bearing mouse model

Background

Interleukin-24 (IL-24) is a therapeutic gene for melanoma, which can induce melanoma cell apoptosis. Mesenchymal stem cells (MSCs) show promise as a carrier to delivery anti-cancer factors to tumor tissues. Induced pluripotent stem cells (iPSCs) are an alternative source of mesenchymal stem cells (MSCs). We previously developed a novel non-viral gene targeting vector to target IL-24 to human iPSCs. This study aims to investigate whether MSCs derived from the iPSCs with the site-specific integration of IL-24 can inhibit the growth of melanoma in a tumor-bearing mouse model via retro-orbital injection.

Methods

IL-24-iPSCs were differentiated into IL-24-iMSCs in vitro, of which cellular properties and potential of differentiation were characterized. The expression of IL-24 in the IL-24-iMSCs was measured by qRT-PCR, Western Blotting, and ELISA analysis. IL-24-iMSCs were transplanted into the melanoma-bearing mice by retro-orbital intravenous injection. The inhibitory effect of IL-24-iMSCs on the melanoma cells was investigated in a co-culture system and tumor-bearing mice. The molecular mechanisms underlying IL-24-iMSCs in exerting anti-tumor effect were also explored.

Results

iPSCs-derived iMSCs have the typical profile of cell surface markers of MSCs and have the ability to differentiate into osteoblasts, adipocytes, and chondroblasts. The expression level of IL-24 in IL-24-iMSCs reached 95.39 ng/10⁶ cells/24 h, which is significantly higher than that in iMSCs, inducing melanoma cells apoptosis more effectively in vitro compared with iMSCs. IL-24-iMSCs exerted a significant inhibitory effect on the growth of melanoma in subcutaneous mouse models, in which the migration of IL-24-iMSCs to tumor tissue was confirmed. Additionally, increased expression of Bax and Cleaved caspase-3 and down-regulation of Bcl-2 were observed in the mice treated with IL-24-iMSCs.

Conclusion

MSCs derived from iPSCs with the integration of IL-24 at rDNA locus can inhibit the growth of melanoma in tumor-bearing mouse models when administrated via retro-orbital injection.

Expression, Purification, and Polyethylene Glycol Site-Specific Modification of Recombinant Human Interleukin 24 in Escherichia coli

Interleukin 24 (IL-24) has a broad spectrum of specific antitumor activities without affecting normal cells. The recombinant human IL-24 (rhIL-24) expressed in E. coli has low biological activity due to lack of necessary glycosylation modification. In this study, based on the modification of the non-glycosylated IL-24 with polyethylene glycol (PEG), we aimed to improve the stability and prolong its half-life in vivo. Firstly, the recombinant plasmid containing the hIL-24 cDNA was prepared by the prokaryotic-expression plasmid pET-28a and transformed into E. coli BL21. After induced by isopropyl β-D-thiogalactoside (IPTG), the target protein rhIL-24 was expressed as insoluble inclusion body, which was solubilized and denatured by 6 M guanidine hydrochloride. The denatured rhIL-24 was diluted to refold in the optimized buffer overnight at the protein concentration of 0.1 mg/mL. The refolded rhIL-24 was mainly in the form of soluble aggregate, but high-purity monomer rhIL-24 was obtained through size exchange chromatography with the addition of SDS in elution buffer. The tertiary structure of rhIL-24 was confirmed by fluorescence spectroscopy. Western blot analysis showed that rhIL-24 could be site-specifically modified by mPEG5000-ALD. Methyl thiazolyl tetrazolium (MTT) assay showed no significant difference between mPEG5000-ALD-rhIL-24 and rhIL-24 in inhibiting the growth of melanoma cell line A375 in vitro. Pharmacokinetic studies showed that PEG modification could significantly improve the stability and prolong the half-life of rhIL-24 from 8.41 to 13.2 h. The data strongly suggested that mPEG-ALD 5000 could site-specifically modify rhIL-24 expressed in E. coli. The PEG modification significantly prolonged the half-life of rhIL-24 without reducing its antitumor activity in vitro.

IL-24 Promotes Apoptosis through cAMP-Dependent PKA Pathways in Human Breast Cancer Cells

Interleukin 24 (IL-24) is a tumor-suppressing protein, which inhibits angiogenesis and induces cancer cell-specific apoptosis. We have shown that IL-24 regulates apoptosis through phosphorylated eukaryotic initiation factor 2 alpha (eIF2α) during endoplasmic reticulum (ER) stress in cancer. Although multiple stresses converge on eIF2α phosphorylation, the cellular outcome is not always the same. In particular, ER stress-induced apoptosis is primarily regulated through the extent of eIF2α phosphorylation and activating transcription factor 4 (ATF4) action. Our studies show for the first time that cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) activation is required for IL-24-induced cell death in a variety of breast cancer cell lines and this event increases ATF4 activity. We demonstrate an undocumented role for PKA in regulating IL-24-induced cell death, whereby PKA stimulates phosphorylation of p38 mitogen-activated protein kinase and upregulates extrinsic apoptotic factors of the Fas/FasL signaling pathway and death receptor 4 expression. We also demonstrate that phosphorylation and nuclear import of tumor suppressor TP53 occurs downstream of IL-24-mediated PKA activation. These discoveries provide the first mechanistic insights into the function of PKA as a key regulator of the extrinsic pathway, ER stress, and TP53 activation triggered by IL-24.

Bacterial tRNase-Based Gene Therapy with Poly(β-Amino Ester) Nanoparticles for Suppressing Melanoma Tumor Growth and Relapse

Here, a novel anticancer gene therapy with a bacterial tRNase gene, colicin D or virulence associated protein C (VapC), is suggested using biodegradable polymeric nanoparticles, such as poly(β-amino esters) (PBAEs) as carriers. These genes are meticulously selected, aiming at inhibiting translation in the recipients by hydrolyzing specific tRNA species. In terms of nanoparticles, out of 9 PBAE formulations, a leading polymer, (polyethylene oxide)₄ -bis-amine end-capped poly(1,4-butanediol diacrylate-co-5-amino-1-pentanol) (B4S5E5), is identified that displays higher gene delivery efficacy to cancer cells compared with the leading commercial reagent Lipofectamine 2000. Interestingly, the B4S5E5 PBAE nanoparticles complexed with colicin D or VapC plasmid DNA induce significant toxicity highly specific to cancer cells by triggering apoptosis. In contrast, the PBAE nanoparticles do not induce these cytotoxic effects in noncancerous cells. In a mouse melanoma model of grafted murine B16-F10 cells, it is demonstrated that treatment with PBAE nanoparticles complexed with these tRNase genes significantly reduces tumor growth rate and delays tumor relapse. Moreover, increased stability of PBAE by PEGylation further enhances the therapeutic effect of tRNase gene treatment and improves survival of animals. This study highlights a nonviral gene therapy that is highly promising for the treatment of cancer.

Role of MDA-7/IL-24 a Multifunction Protein in Human Diseases

Subtraction hybridization identified genes displaying differential expression as metastatic human melanoma cells terminally differentiated and lost tumorigenic properties by treatment with recombinant fibroblast interferon and mezerein. This approach permitted cloning of multiple genes displaying enhanced expression when melanoma cells terminally differentiated, called melanoma differentiation associated (mda) genes. One mda gene, mda-7, has risen to the top of the list based on its relevance to cancer and now inflammation and other pathological states, which based on presence of a secretory sequence, chromosomal location, and an IL-10 signature motif has been named interleukin-24 (MDA-7/IL-24). Discovered in the early 1990s, MDA-7/IL-24 has proven to be a potent, near ubiquitous cancer suppressor gene capable of inducing cancer cell death through apoptosis and toxic autophagy in cancer cells in vitro and in preclinical animal models in vivo. In addition, MDA-7/IL-24 embodied profound anticancer activity in a Phase I/II clinical trial following direct injection with an adenovirus (Ad.mda-7; INGN-241) in tumors in patients with advanced cancers. In multiple independent studies, MDA-7/IL-24 has been implicated in many pathological states involving inflammation and may play a role in inflammatory bowel disease, psoriasis, cardiovascular disease, rheumatoid arthritis, tuberculosis, and viral infection. This review provides an up-to-date review on the multifunctional gene mda-7/IL-24, which may hold potential for the therapy of not only cancer, but also other pathological states.

New Insights Into Beclin-1: Evolution and Pan-Malignancy Inhibitor Activity

Autophagy is a functionally conserved self-degradation process that facilitates the survival of eukaryotic life via the management of cellular bioenergetics and maintenance of the fidelity of genomic DNA. The first known autophagy inducer was Beclin-1. Beclin-1 is expressed in multicellular eukaryotes ranging throughout plants to animals, comprising a nonmonophyllic group, as shown in this report via aggressive BLAST searches. In humans, Beclin-1 is a haploinsuffient tumor suppressor as biallelic deletions have not been observed in patient tumors clinically. Therefore, Beclin-1 fails the Knudson hypothesis, implicating expression of at least one Beclin-1 allele is essential for cancer cell survival. However, Beclin-1 is frequently monoallelically deleted in advanced human cancers and the expression of two Beclin-1 allelles is associated with greater anticancer effects. Overall, experimental evidence suggests that Beclin-1 inhibits tumor formation, angiogenesis, and metastasis alone and in cooperation with the tumor suppressive molecules UVRAG, Bif-1, Ambra1, and MDA-7/IL-24 via diverse mechanisms of action. Conversely, Beclin-1 is upregulated in cancer stem cells (CSCs), portending a role in cancer recurrence, and highlighting this molecule as an intriguing molecular target for the treatment of CSCs. Many aspects of Beclin-1's biological effects remain to be studied. The consequences of these BLAST searches on the molecular evolution of Beclin-1, and the eukaryotic branches of the tree of life, are discussed here in greater detail with future inquiry focused upon protist taxa. Also in this review, the effects of Beclin-1 on tumor suppression and cancer malignancy are discussed. Beclin-1 holds significant promise for the development of novel targeted cancer therapeutics and is anticipated to lead to a many advances in our understanding of eukaryotic evolution, multicellularity, and even the treatment of CSCs in the coming decades.

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.

Discovery of a new class of 16-membered (2Z,11Z)-3,11-di(aryl/naphthyl)-1,13-dioxa-5,9-dithia-2,12-diazacyclohexadeca-2,11-dienes as anti-tumor agents

A series of new 16-membered macrocyclic compounds were synthesized and evaluation of in vitro anti-tumor activities on MDAMB-231 cell lines reveal that the macrocycles, 1a, 1f, 1g, 1i and 1k are promising anti-tumor agents.

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.

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.

Insulin-like growth factor binding protein-3 mediates interleukin-24-induced apoptosis through inhibition of the mTOR pathway in prostate cancer

IGF-binding protein-3 (IGFBP-3) has been shown to induce apoptosis in an insulin-like growth factor (IGF)-independent manner in various cell systems, however, the underlying molecular mechanisms remain unknown. In the present study, we showed that IGFBP-3 significantly enhanced interleukin-24 (IL-24)-induced cell death in prostate cancer (PC) cell lines in vitro. Both the addition of IGFBP-3 to cell medium or the enforced expression of IGFBP-3 in the PC cell line inhibited activation of mammalian target of rapamycin (mTOR). Downregulation of mTOR/S6K reduced Mcl-1 protein expression and consequently promoted sensitization to IL-24 treatment. Overexpression of Mcl-1 reduced the level of cleaved poly(ADP-ribose) polymerase (PARP) induced by IL-24 and IGFBP-3, suggesting that the IL-24-induced apop-tosis is realized by way of Mcl-1. We then showed that the combination of IL-24 and IGFBP-3 significantly suppressed PC tumor growth in vivo. We propose that the IGFBP-3 and IL-24 non-toxic mTOR inhibitors can be used as an adjuvant in the treatment of PC.

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.

Characterization of the canine mda-7 gene, transcripts and expression patterns

Human melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) displays potent growth suppressing and cell killing activity against a wide variety of human and rodent cancer cells. In this study, we identified a canine ortholog of the human mda-7/IL-24 gene located within a cluster of IL-10 family members on chromosome 7. The full-length mRNA sequence of canine mda-7 was determined, which encodes a 186-amino acid protein that has 66% similarity to human MDA-7/IL-24. Canine MDA-7 is constitutively expressed in cultured normal canine epidermal keratinocytes (NCEKs), and its expression levels are increased after lipopolysaccharide stimulation. In cultured NCEKs, the canine mda-7 pre-mRNA is differentially spliced, via exon skipping and alternate 5'-splice donor sites, to yield five splice variants (canine mda-7sv1, canine mda-7sv2, canine mda-7sv3, canine mda-7sv4 and canine mda-7sv5) that encode four protein isoforms of the canine MDA-7 protein. These protein isoforms have a conserved N-terminus (signal peptide sequence) and are dissimilar in amino acid sequences at their C-terminus. Canine MDA-7 is not expressed in primary canine tumor samples, and most tumor derived cancer cell lines tested, like its human counterpart. Unlike human MDA-7/IL-24, canine mda-7 mRNA is not expressed in unstimulated or lipopolysaccharide (LPS), concanavalin A (ConA) or phytohemagglutinin (PHA) stimulated canine peripheral blood mononuclear cells (PBMCs). Furthermore, in-silico analysis revealed that canonical canine MDA-7 has a potential 28 amino acid signal peptide sequence that can target it for active secretion. This data suggests that canine mda-7 is indeed an ortholog of human mda-7/IL-24, its protein product has high amino acid similarity to human MDA-7/IL-24 protein and it may possess similar biological properties to human MDA-7/IL-24, but its expression pattern is more restricted than its human ortholog.

Combination of adenoviruses expressing melanoma differentiation-associated gene-7 and chemotherapeutic agents produces enhanced cytotoxicity on esophageal carcinoma

We examined the combinatory antitumor effects of adenoviruses expressing human mda-7/IL-24 gene (Ad-mda-7) and chemotherapeutic agents on nine kinds of human esophageal carcinoma cells. All the carcinoma cells expressed the melanoma differentiation-associated gene-7/interleukin-24 (MDA-7/IL-24) receptor complexes, IL-20R2 and either IL-20R1 or IL-22R1, and were susceptible to Ad-mda-7, whereas fibroblasts were positive only for IL-20R2 gene and resistant to Ad-mda-7-mediated cytotoxicity. Sensitivity of these esophageal carcinoma cells to Ad-mda-7 was however lower than that to Ad expressing the wild-type p53 gene. We thereby investigated a possible combination of Ad-mda-7 and anticancer agents and found that Ad-mda-7 with 5-fluorouracil (5-FU), cisplatin, mitomycin C or etoposide produced greater cytotoxic effects than those by Ad-mda-7 or the agent alone. Half-maximal inhibitory concentration values of the agents in respective cells were decreased by the combination with Ad-mda-7. Cell cycle analyses showed that Ad-mda-7 and 5-FU increased G2/M-phase and S-phase populations, respectively, and the combination augmented sub-G1 populations. Ad-mda-7-treated cells showed cleavages of caspase-8, -9 and -3 and poly (ADP-ribose) polymerase, but the cleavage levels were not different from those of the combination-treated cells. Ad-mda-7 treatments upregulated Akt phosphorylation but suppressed IκB-α levels, whereas 5-FU treatments induced phosphorylation of p53 and extracellular signal-regulated protein kinases 1 and 2. Molecular changes caused by the combination were similar to those by Ad-mda-7 treatments, but the Ad-mda-7-mediated upregulation of Akt phosphorylation decreased with the combination. These data collectively suggest that Ad-mda-7 induced apoptosis despite Akt activation and that the combinatory antitumor effects with 5-FU were produced partly by downregulating the Ad-mda-7-induced Akt activation.

Suppression effect of recombinant adenovirus vector containing hIL-24 on Hep-2 laryngeal carcinoma cells

The melanoma differentiation-associated gene-7 [MDA-7; renamed interleukin (IL)-24] was isolated from human melanoma cells induced to terminally differentiate by treatment with interferon and mezerein. MDA-7/IL-24 functions as a multimodality anticancer agent, possessing proapoptotic, antiangiogenic and immunostimulatory properties. All these attributes make MDA-7/IL-24 an ideal candidate for cancer gene therapy. In the present study, the human MDA-7/IL-24 gene was transfected into the human laryngeal cancer Hep-2 cell line and human umbilical vein endothelial cells (HUVECs) with a replication-incompetent adenovirus vector. Reverse transcription polymerase chain reaction and western blot analysis confirmed that the Ad-hIL-24 was expressed in the two cells. The expression of the antiapoptotic gene, Bcl-2, was significantly decreased and the IL-24 receptor was markedly expressed in Hep-2 cells following infection with Ad-hIL-24, but not in HUVECs. In addition, the expression of the proapoptotic gene, Bax, was induced and the expression of caspase-3 was increased in the Hep-2 cells and HUVECs. Methyl thiazolyl tetrazolium assay indicated that Ad-hIL-24 may induce growth suppression in Hep-2 cells but not in HUVECs. In conclusion, Ad-hIL-24 selectively inhibits proliferation and induces apoptosis in Hep-2 cells. No visible damage was found in HUVECs. Therefore, the results of the current study indicated that Ad-hIL-24 may have a potent suppressive effect on human laryngeal carcinoma cell lines, but is safe for healthy 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.

Molecular targets and signaling pathways regulated by interleukin (IL)-24 in mediating its antitumor activities

Cancer remains a major health issue in the world and the effectiveness of current therapies is limited resulting in disease recurrence and resistance to therapy. Therefore to overcome disease recurrence and have improved treatment efficacy there is a continued effort to develop and test new anticancer drugs that are natural or synthetic - (conventional chemotherapeutics, small molecule inhibitors) and biologic (antibody, tumor suppressor genes, oligonucleotide) product. In parallel, efforts for identifying molecular targets and signaling pathways to which cancer cells are "addicted" are underway. By inhibiting critical signaling pathways that is crucial for cancer cell survival, it is expected that the cancer cells will undergo a withdrawal symptom akin to "de-addiction" resulting in cell death. Thus, the key for having an improved and greater control on tumor growth and metastasis is to develop a therapeutic that is able to kill tumor cells efficiently by modulating critical signaling pathways on which cancer cells rely for their survival.Currently several small molecule inhibitors targeted towards unique molecular signaling pathways have been developed and tested in the clinic. Few of these inhibitors have shown efficacy while others have failed. Thus, targeting a single molecule or pathway may be insufficient to completely block cancer cell proliferation and survival. It is therefore important to identify and test an anticancer drug that can inhibit multiple signaling pathways in a cancer cell, control growth of both primary and metastatic tumors and is safe.One biologic agent that has the characteristics of serving as a potent anticancer drug is interleukin (IL)-24. IL-24 suppresses multiple signaling pathways in a broad-spectrum of human cancer cells leading to tumor cell death, inhibition of tumor angiogenesis and metastasis. Additionally, combining IL-24 with other therapies demonstrated additive to synergistic antitumor activity. Clinical testing of IL-24 as a gene-based therapeutic for the treatment of solid tumors demonstrated that IL-24 is efficacious and is safe. The unique features of IL-24 support its further development as an anticancer drug for cancer treatment.In this review we summarize the current understanding on the molecular targets and signaling pathways regulated by IL-24 in mediating its anticancer activity.

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.

Inhibition of ubiquitin conjugating enzyme UBE2C reduces proliferation and sensitizes breast cancer cells to radiation, doxorubicin, tamoxifen and letrozole

PURPOSE

The objective of this study was to determine radiation, doxorubicin, tamoxifen and letrozole sensitivity of breast cancer cells in response to functional inhibition of the ubiquitin conjugating enzyme UBE2C.

METHODS

Taqman Real time PCR was performed to measure UBE2C levels in breast cancer cell lines and control HBL100 and HEK293T cells. A dominant negative form of UBE2C (DN-UBE2C) was used to functionally inhibit wild type UBE2C. Cell proliferation and anchorage independent growth were measured by colorimetric and soft agar assays, respectively. Radiation, doxorubicin, tamoxifen and letrozole responses of the cell lines were assessed by colorimetric and clonogenic assays.

RESULTS

Overexpression of UBE2C was observed in all breast cancer cell lines tested using quantitative real time PCR. UBE2C expression was found to be highest in MDAMB231 and relatively lowest in MCF7 cells, compared to control cells. Both the growth rate and the anchorage independent growth of MCF7 and MDAMB231 cells transfected with DN-UBE2C were significantly reduced compared to cells transfected with vector alone. MCF7 and MDAMB231 cells expressing DN-UBE2C were significantly more sensitive to different doses of radiation and doxorubicin compared to both wild type and vector alone transfected cells. In addition, DN-UBE2C transfected MCF7 cells were more sensitive to inhibition by tamoxifen and letrozole compared to wild type and vector alone transfected cells.

CONCLUSIONS

Our results show that inhibition of UBE2C sensitizes breast cancer cells to radiation, doxorubicin and hormone blocking agents. UBE2C may, therefore, serve as a potential therapeutic target aimed at inducing radiation and chemo sensitization.

Adenovirus-mediated IL-24 expression enhances the chemosensitivity of multidrug-resistantgastric cancer cells to cisplatin

Chemotherapy is one of the commonly used strategies in gastric cancer, especially for unresectable patients, but it becomes insensitive to repeated administration of even the most effective chemotherapeutic agents, such as cisplatin. Given this, there is an urgent need for developing chemosensitizers to overcome acquired resistance to chemotherapeutic agents. Interleukin-24 (IL-24), a cytokine-tumor suppressor, shows broad-spectrum and tumor-specific antitumor properties, and studies have demonstrated that IL-24 could conspicuously restore the chemosensitivity of MDR cancer cells. Herein, we developed a human MDR gastric cancer cell subline, SGC7901/CDDP, by repeated selection of resistant clones of parental sensitive cells, and further investigated the chemosensitizing effects and the underlying mechanisms of adenovirus-mediated IL-24 (Ad-IL-24) gene therapy plus CDDP for the human MDR gastric cancer cells SGC7901/CDDP in vitro and in vivo. The results demonstrated that the expression of IL-24 mRNA and protein was profoundly downregulated in SGC7901/CDDP cells by RT-PCR and western blot analysis. In addition, the cell viability assay showed that the IC50 of SGC7901/CDDP cells to CDDP, 5-FU, ADM and MTX was significantly enhanced compared to parental sensitive SGC7901 cells. Ad-IL-24-induced IL-24 overexpression decreased the IC50 of the above agents (not MTX), induced G2/M cell cycle arrest, and Ad-IL-24 plus CDDP elicited significant apoptosis and tumor suppression of SGC7901/CDDP cells in vitro and SGC7901/CDDP cell xenograft tumors in vivo, respectively. Moreover, our results demonstrated that the mechanisms of Ad-IL-24-elicited chemosensitizing effects were closely associated with a substantial upregulation of Bax and downregulation of P-gp and Bcl-2 in SGC7901/CDDP cells in vitro and SGC7901/CDDP xenograft tissues in vivo. Thus, this study indicates that overexpression of IL-24 gene can significantly promote chemosensitivity in MDR phenotype SGC7901/CDDP gastric cancer cells.

Chapter One---Cancer terminator viruses and approaches for enhancing therapeutic outcomes

No single or combinatorial therapeutic approach has proven effective in decreasing morbidity or engendering a cure of metastatic cancer. In principle, conditionally replication-competent adenoviruses that induce tumor oncolysis through cancer-specific replication hold promise for cancer therapy. However, a single-agent approach may not be adequate to completely eradicate cancer in a patient because most cancers arise from abnormalities in multiple genetic and signal transduction pathways and targeting disseminated metastases is difficult to achieve. Based on these considerations, a novel class of cancer destroying adenoviruses have been produced, cancer terminator viruses (CTVs), in which cancer-specific replication is controlled by the progression-elevated gene-3 promoter and replicating viruses produce a second transgene encoding an apoptosis-inducing and immunomodulatory cytokine, either melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) or interferon-γ. This review focuses on these viruses and ways to improve their delivery systemically and enhance their therapeutic efficacy.

A conditionally replicating adenovirus carrying interleukin-24 sensitizes melanoma cells to radiotherapy via apoptosis

Combinatorial therapy is the current trend of the development of novel cancer treatments due to the high heterogenous nature of solid tumors. In this study, we investigated the effects of the combined use of a conditionally replicating adenovirus carrying IL-24 (ZD55-IL-24) and radiotherapy on the proliferation and apoptosis of melanoma A375 cells in vitro and in vivo. Compared with either agent used alone, ZD55-IL-24 combined with radiotherapy significantly inhibited cell proliferation, accompanied with increased apoptosis. Radiotherapy did not affect the expression of IL-24 and E1A of ZD55-IL-24-treated cells, but increased the expression of Bax, promoted the activation of caspase-3, while decreasing Bcl-2 levels. Thus, this synergistic effect of ZD55-IL-24 in combination with radiotherapy provides a novel strategy for the development of melanoma therapies, and is a promising approach for further clinical development.

Conditionally replicating adenoviruses carrying mda-7/IL-24 for cancer therapy

BACKGROUND

Melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) suppresses growth and induces apoptosis in a broad range of human cancers without significant cytotoxicity to normal cells. Conditionally replicating adenoviruses (CRAds) not only have the ability to destroy cancer cells but may also be potential vectors for the expression of therapeutic genes.

METHODS

This review provides an overview of specifications for a novel anti-tumor approach CRAds carrying IL-24, and discusses recent progress in this field.

RESULTS

Studies in multiple laboratories report that CRAds carrying IL-24 selectively induced apoptosis in some cancer cells, and enhanced selective toxicity to cancer cells when combined with chemotherapeutic agents.

CONCLUSION

CRAds carrying IL-24 may prove a novel and effective approach for the treatment of cancers.

MDA-7 results in downregulation of AKT concomitant with apoptosis and cell cycle arrest in breast cancer cells

The melanoma differentiation-associated gene-7 (mda-7) is a known mediator of apoptosis in cancer cells but not in normal cells. We hypothesized that MDA-7 interferes with the prosurvival signaling pathways that are commonly altered in cancer cells to induce growth arrest and apoptosis. We also identified the cell signaling pathways that are antagonized by MDA-7 leading to apoptosis. Using an adenoviral expression system, mda-7 was introduced into the breast cancer cell lines SKBr3, MCF-7 and MDA-MB-468, each with a different estrogen receptor (ER) and HER-2 receptor status. Downstream targets of MDA-7 were assessed by reverse phase protein array analysis, western blot analysis and immunofluorescence confocal microscopy. Our results show that MDA-7-induced apoptosis was mediated by caspases in all cell lines tested. However, MDA-7 modulates additional pathways in SKBr3 (HER-2 positive) and MCF-7 (ER positive) cells including downregulation of AKT-GSK3β and upregulation of cyclin-dependent kinase inhibitors in the nucleus. This leads to cell cycle arrest in addition to apoptosis. In conclusion, MDA-7 abrogates tumor-promoting pathways including the activation of caspase-dependent signaling pathways ultimately leading to apoptosis. In addition, depending on the phenotype of the breast cancer cell, MDA-7 modulates cell cycle regulating pathways to mediate cell cycle arrest.

Naturally occurring, tumor-specific, therapeutic proteins

The emerging approach to cancer treatment known as targeted therapies offers hope in improving the treatment of therapy-resistant cancers. Recent understanding of the molecular pathogenesis of cancer has led to the development of targeted novel drugs such as monoclonal antibodies, small molecule inhibitors, mimetics, antisense and small interference RNA-based strategies, among others. These compounds act on specific targets that are believed to contribute to the development and progression of cancers and resistance of tumors to conventional therapies. Delivered individually or combined with chemo- and/or radiotherapy, such novel drugs have produced significant responses in certain types of cancer. Among the most successful novel compounds are those which target tyrosine kinases (imatinib, trastuzumab, sinutinib, cetuximab). However, these compounds can cause severe side-effects as they inhibit pathways such as epidermal growth factor receptor (EGFR) or platelet-derived growth factor receptor, which are also important for normal functions in non-transformed cells. Recently, a number of proteins have been identified which show a remarkable tumor-specific cytotoxic activity. This toxicity is independent of tumor type or specific genetic changes such as p53, pRB or EGFR aberrations. These tumor-specific killer proteins are either derived from common human and animal viruses such as E1A, E4ORF4 and VP3 (apoptin) or of cellular origin, such as TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) and MDA-7 (melanoma differentiation associated-7). This review aims to present a current overview of a selection of these proteins with preferential toxicity among cancer cells and will provide an insight into the possible mechanism of action, tumor specificity and their potential as novel tumor-specific cancer therapeutics.

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.

The development of MDA-7/IL-24 as a cancer therapeutic

The cytokine melanoma differentiation associated gene 7 (mda-7) was identified by subtractive hybridization 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 to non-transformed cells. Based on conserved structure, chromosomal location and cytokine-like properties, MDA-7, was classified as a member of the interleukin (IL)-10 gene family and designated as MDA-7/IL-24. Multiple studies have demonstrated that expression of MDA-7/IL-24 in a wide variety of tumor cell types, but not in corresponding equivalent non-transformed cells, causes their growth arrest and rapid cell death. In addition, MDA-7/IL-24 has been noted to radiosensitize tumor cells which in part is due to the generation of reactive oxygen species (ROS) and ceramide that cause endoplasmic reticulum stress and suppress protein translation. 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, strongly arguing that MDA-7/IL-24 could have significant therapeutic value. This review describes what is presently known about the impact of MDA-7/IL-24 on tumor cell biology and its potential therapeutic applications.

The in vitro and in vivo antitumor activity of adenovirus-mediated interleukin-24 expression for laryngocarcinoma

Interleukin-24 (IL-24)/melanoma differentiation associated gene-7 (mda-7) as a novel tumor-suppressor gene has potent antitumor activities in a broad spectrum of human cancers through the activation of various signaling pathways. However, the suppressive effect of adenovirus-mediated IL-24 (Ad-IL-24) expression on human laryngeal cancers is still elusive. In this study, we explored the therapeutic effect of Ad-IL-24 on human laryngeal cancers in vitro and in vivo in an athymic nude mouse model, using a Hep-2 human laryngocarcinoma cell line, and a WI-38 human diploid cell line served as a normal cell control. We demonstrated that Ad-IL-24 induced significant growth inhibition and apoptosis, upregulated the expression of P21, P27, and Bax, downregulated Bcl-2 expression, and activated caspase-3 in Hep-2 laryngeal tumor cells, while it exerted no direct effect on the in vitro proliferation of WI-38 normal diploid cells. Moreover, intratumoral injections of Ad-IL-24 in nude mice bearing Hep-2 tumors significantly suppressed the laryngeal xengrafted tumor growth and reduced microvessel density (MVD) and VEGF expression in tumors. This retarded tumor growth in vitro and in vivo elicited by Ad-IL-24 was closely associated with the upregulation of proliferation-related molecules P21 and P27, decrease in the ratio of anti- to proapoptotic molecules Bcl-2/Bax, followed by the activation of caspase-3, leading to apoptosis via intrinsic apoptotic pathways, and the reduced expression of proangiogenic factor VEGF involved in the inhibition of tumor angiogenesis. Thus, our results indicate that the potent, selective killing activity of Ad-IL-24 in laryngeal cancer cells, but not in normal cells, makes this vector a potential candidate for laryngeal cancer gene therapy.

Tumour suppressor function of MDA-7/IL-24 in human breast cancer

Introduction

Melanoma differentiation associated gene-7 (MDA-7), also known as interleukin (IL)-24, is a tumour suppressor gene associated with differentiation, growth and apoptosis. However, the mechanisms underlying its anti-neoplastic activity, tumour-specificity and efficacy across a spectrum of human cancers have yet to be fully elucidated. In this study, the biological impact of MDA-7 on the behavior of breast cancer (BC) cells is evaluated. Furthermore, mRNA expression of MDA-7 is assessed in a cohort of women with BC and correlated with established pathological parameters and clinical outcome.

Methods

The human BC cell line MDA MB-231 was used to evaluate the in-vitro impact of recombinant human (rh)-MDA-7 on cell growth and motility, using a growth assay, wounding assay and electric cell impedance sensing (ECIS). Localisation of MDA-7 in mammary tissues was assessed with standard immuno-histochemical methodology. BC tissues (n = 127) and normal tissues (n = 33) underwent RNA extraction and reverse transcription, MDA-7 transcript levels were determined using real-time quantitative PCR. Transcript levels were analyzed against tumour size, grade, oestrogen receptor (ER) status, nodal involvement, TNM stage, Nottingham Prognostic Index (NPI) and clinical outcome over a 10 year follow-up period.

Results

Exposure to rh-MDA-7 significantly reduced wound closure rates for human BC cells in-vitro. The ECIS model demonstrated a significantly reduced motility and migration following rh-MDA-7 treatment (p = 0.024). Exposure to rh-MDA-7 was only found to exert a marginal effect on growth. Immuno-histochemical staining of human breast tissues revealed substantially greater MDA-7 positivity in normal compared to cancer cells. Significantly lower MDA-7 transcript levels were identified in those predicted to have a poorer prognosis by the NPI (p = 0.049) and those with node positive tumours. Significantly lower expression was also noted in tumours from patients who died of BC compared to those who remained disease free (p = 0.035). Low levels of MDA-7 were significantly correlated with a shorter disease free survival (mean = 121.7 vs. 140.4 months, p = 0.0287) on Kaplan-Meier survival analysis.

Conclusion

MDA-7 significantly inhibits the motility and migration of human BC cells in-vitro. MDA-7 expression is substantially reduced in malignant breast tissue and low transcript levels are significantly associated with unfavourable pathological parameters, including nodal positivity; and adverse clinical outcomes including poor prognosis and shorter disease free survival. MDA-7 offers utility as a prognostic marker and potential for future therapeutic strategies.

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.

Interleukin-24 overcomes temozolomide resistance and enhances cell death by down-regulation of O6-methylguanine-DNA methyltransferase in human melanoma cells

Melanoma is the most malignant of skin cancers, highly resistant to chemotherapy and radiotherapy. Temozolomide, a promising new derivative of dacarbazine, is currently being tested for treatment of metastatic melanoma. Resistance to alkylating agents such as temozolomide correlates with increased expression of DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT). Interleukin-24 (IL-24; mda-7) is a tumor suppressor cytokine that selectively inhibits tumor cell growth by inducing apoptosis and cell cycle arrest in melanoma cell lines and solid tumors. This tumor-selective activity has been observed in multiple preclinical animal models and in clinical trials. In this study, we analyzed the ability of Ad-IL-24 and its protein product, IL-24, to overcome temozolomide resistance in human melanoma cells. We have shown that Ad-IL-24 via exogenous IL-24 protein induces combinatorial synergy of temozolomide-induced cell killing in temozolomide-resistant melanoma cells by inhibition of MGMT. Neutralizing antibodies against IL-24 or its receptors significantly blocked the apoptotic activity of IL-24 + MGMT treatment. We show that accumulation of functional p53 is essential for IL-24-induced down-regulation of MGMT. Using either MGMT small interfering RNA, p53 small interfering RNA, or a p53 dominant-negative mutant to block MGMT protein expression resulted in increased sensitization to temozolomide. However, MGMT blockade in combination with IL-24 + temozolomide resulted in loss of combinatorial synergy, indicating that MGMT expression is required for the reversal of temozolomide resistance in melanoma cells. This study shows that IL-24 can play a significant role in overcoming temozolomide resistance and that the clinical efficacy of temozolomide may be improved by using a biochemotherapy combination with IL-24.

mda-7/IL-24 inhibits the proliferation of hematopoietic malignancies in vitro and in vivo

OBJECTIVE

Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) has been consistently shown to exert growth inhibitory effects on various tumor types. However, the majority of these reports were limited to solid tumors. The purpose of this study was to investigate the antitumor activity of mda-7/IL-24 and the underlying mechanism in hematopoietic malignancies.

MATERIALS AND METHODS

We determined the expression of mda-7/IL24 and its heterodimeric receptors in hematopoietic tumor cell lines and then stably transfected mda-7/IL-24 into K562 (leukemia) and Namalwa (lymphoma) cell lines to assess the effects of mda-7/IL-24 on cell proliferation, cell cycle, apoptosis, colony-forming ability, and tumor growth in vivo. Microarray analysis was performed to determine the genes that were differentially regulated by mda-7/IL-24 in K562 cells.

RESULTS

Expression of mda-7/IL-24 or its intact receptor pairs was not detected in the 11 cell lines tested. Ectopic expression of mda-7/IL-24 induced significant (p < 0.05) inhibition of cell growth and colony formation in both K562 and Namalwa cells, and the growth inhibition in K562 cells was associated with G(0)/G(1) cell-cycle arrest. Results of in vivo studies showed good correlation with in vitro inhibition of tumor cell proliferation in both the cell lines. We also showed that the increase in p21(WAF-1) and BCCIP and decrease in cdk6, smurf2, and phosphorylated pRb, which are regulators of cell-cycle progression, might account for G(0)/G(1) cell-cycle arrest in K562 cells.

CONCLUSIONS

The present study demonstrated for the first time the potential antitumor activity of mda-7/IL-24 in chronic myelogenous leukemia and lymphoma.

Development of Ad-mda7/IL-24-resistant lung cancer cell lines

Many cancers can become resistant to repeated administration of even the most effective therapeutic agents. In developing adenoviral mda-7/IL-24 (Ad-mda-7/IL-24) therapy for lung cancer, we have anticipated this potential clinical problem by attempting to identify the molecular mechanisms of Ad-mda7/IL-24 resistance in several Ad-mda7/IL-24-resistant lung cancer cell lines that we have developed. For the present study, we established four Admda7- resistant cell lines by repeated selection of resistant clones of parental Ad-mda7-sensitive A549 cells: two lines (A549R1 and A549R2) resistant to both adenoviral vector and the mda-7 gene and two (A549R3 and A549R4) resistant to the therapeutic mda-7 gene only. As shown by western blot analysis of several known anti-apoptotic proteins, parental A549 and resistant A549R3 cells expressed similar levels of AKT and phosphorylated AKT (p-AKT), whereas resistant A549R3 and A549R4 cells expressed higher levels of bcl-2 and lower levels of bcl-xL than did their parental cells. As shown by flow-cytometric analysis, treating resistant A549R3 and A549R4 cells with a combination of Ad-mda7 and 17-allyl-amino-17-demethoxygeldanamycin (17AAG) (50 nM) for 48 hours enhanced apoptosis. Together, these in vitro findings indicate that an antiapoptotic mechanism may underlie Ad-mda7 resistance and that such resistance can be overcome by addition of 17AAG. Further investigations along these lines are warranted.

Diepoxybutane activates the mitochondrial apoptotic pathway and mediates apoptosis in human lymphoblasts through oxidative stress

Diepoxybutane (DEB) is the most potent metabolite of the environmental chemical 1,3-butadiene (BD), which is prevalent in petrochemical industrial areas. BD is a known mutagen and human carcinogen, and possesses multi-systems organ toxicity. We recently reported that DEB-induced cell death in TK6 lymphoblasts was due to the occurrence of apoptosis, and not necrosis. In this study, we investigated the molecular mechanisms responsible for DEB-induced apoptosis in these cells. Bax and Bak were found to be over-expressed and activated, and the mitochondrial trans-membrane potential was attenuated in cells undergoing DEB-induced apoptosis. Cytochrome c was depleted from the mitochondria of TK6 cells undergoing apoptosis, and was released into the cytosol in Jurkat T-lymphoblasts exposed to the same concentrations of DEB. Executioner caspase 3 was deduced to be activated by initiator caspase 9. DEB-induced reactive oxygen species (ROS) formation, and the ROS scavenger N-acetyl-L-cysteine effectively blocked DEB-induced apoptosis in TK6 cells. Collectively, these results demonstrate that the mitochondrial apoptotic pathway is activated to mediate DEB-induced apoptosis in human TK6 lymphoblasts. These results further demonstrate that DEB-induced apoptosis is also mediated by the DEB-induced generation of ROS. This is the first report to examine the mechanism of DEB-induced apoptosis in human lymphoblasts.

Targeting inhibition of K-ras enhances Ad.mda-7-induced growth suppression and apoptosis in mutant K-ras colorectal cancer cells

Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) is a cancer-specific, growth-suppressing and apoptosis-inducing gene with broad-spectrum antitumor activity. However, when administered by means of a replication-incompetent adenovirus, Ad.mda-7, several colorectal carcinoma cell lines are resistant to its antiproliferative and antisurvival effects. We have presently endeavored to determine if K-ras mutations, present in approximately 40-50% of colorectal cancers and which may mediate resistance to chemotherapy and radiotherapy, represent a predisposing genetic factor mitigating reduced sensitivity to Ad.mda-7. To suppress ras expression, three structurally different replication-incompetent adenoviral vectors were engineered that express (1) an intracellular, neutralizing single-chain antibody (scAb) to p21 ras (Ad.K-ras scAb), (2) an antisense (AS) K-ras gene (Ad.K-ras AS) or (3) both mda-7/IL-24 and a K-ras AS gene in a single bipartite virus (Ad.m7.KAS). Simultaneous inhibition of K-ras and expression of mda-7/IL-24 enhanced killing of colorectal carcinoma cells with mutated K-ras, but not with wild-type K-ras. The extent of killing depended on the degree of K-ras downregulation, with Ad.K-ras AS being generally more efficient than Ad.K-ras scAb in combination with Ad.mda-7. These findings support an effective dual-combinatorial approach for the therapy of colorectal cancers that employs a unique cancer-specific suppressor gene (mda-7/IL-24) with targeted inhibition of oncogene (ras) expression.