Melanoma Differentiation Associated Gene-7 (mda-7): A Novel Anti-Tumor Gene for Cancer Gene Therapy

IL-24 is the key effector of Th9 cell-mediated tumor immunotherapy

Th9 cells are powerful effector T cells for cancer immunotherapy. However, the underlying antitumor mechanism of Th9 cells still needs to be further elucidated. Here, we show that Th9 cells express high levels of not only IL-9, but also IL-24. We found that knockout of Il24 gene in Th9 cells promotes Th9 cell proliferation in vitro, but decreases Th9 cell survival in vitro and in vivo. Interestingly, knockout of Il24 gene in Th9 cells decreases the tumor-specific cytotoxicity of Th9 cells in vitro. In addition, immunotherapy with Il24 knockout Th9 cells exhibit less tumor inhibition than regular Th9 cells in mouse tumor models. We found that inhibition of Foxo1 by a specific inhibitor downregulates IL-24 expression in Th9 cells and decreases Th9 cell antitumor efficacy in vivo. Our results identify IL-24 as a powerful antitumor effector of Th9 cells and provide a target in Th9 cell-mediated tumor therapy.

microRNA-205 in prostate cancer: Overview to clinical translation

Prostate cancer (PrCa) is the most common type of cancer among men in the United States. The metastatic and advanced PrCa develops drug resistance to current regimens which accounts for the poor management. microRNAs (miRNAs) have been well-documented for their diagnostic, prognostic, and therapeutic roles in various human cancers. Recent literature confirmed that microRNA-205 (miR-205) has been established as one of the tumor suppressors in PrCa. miR-205 regulates number of cellular functions, such as proliferation, invasion, migration/metastasis, and apoptosis. It is also evident that miR-205 can serve as a key biomarker in diagnostic, prognostic, and therapy of PrCa. Therefore, in this review, we will provide an overview of tumor suppressive role of miR-205 in PrCa. This work also outlines miR-205's specific role in targeted mechanisms for chemosensitization and radiosensitization in PrCa. A facile approach of delivery paths for successful clinical translation is documented. Together, all these studies provide a novel insight of miR-205 as an adjuvant agent for reducing the widening gaps in clinical outcome of PrCa patients.

Oncolytic therapy with vaccinia virus carrying IL-24 for hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is a highly refractory cancer associated with increasing mortality, which currently lacks effective treatment options. Interleukin-24 (IL-24) is a novel tumor suppressor cytokine that can selectively induce cancer cell apoptosis, and it has been utilized as a cancer gene therapy strategy. The vaccinia virus is a promising strategy for cancer therapy, owing to its direct viral lytic effects, as well as a vehicle to overexpress therapeutic transgenes.

METHODS

We constructed a recombinant oncolytic vaccinia viruse (VG9-IL-24) based on vaccinia virus Guang9 (VG9) harboring the IL-24 gene. In vitro, we assessed the replication of VG9-IL-24 in HCC cell lines and normal liver cells and evaluated the cytotoxicity in different cell lines; then, we determined the expression of IL-24 by RT-PCR and ELISA. We examined apoptosis and cell cycle progression in SMMC-7721 cells treated with VG9-IL-24 by flow cytometry. In vivo, we established the SMMC-7721 xenograft mouse model to evaluate the antitumor effects of VG9-IL-24.

RESULTS

In vitro, VG9-IL-24 efficiently infected HCC cell lines, but not normal liver cells, and resulted in a high level of IL-24 expression and significant cytotoxicity. Moreover, VG9-IL-24 induced an increase in the proportion of apoptotic cells and blocked the SMMC-7721 cell cycle in the G2/M phase. In vivo, tumor growth was significantly suppressed and the survival was prolonged in VG9-IL-24-treated mice.

CONCLUSIONS

Vaccinia virus VG9-mediated gene therapy might be an innovative treatment for cancer with tumor-specific lysis and apoptosis-inducing effects. VG9-IL-24 exhibited enhanced antitumor effects and is a promising candidate for HCC therapy.

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.

Strategic Developments & Future Perspective on Gene Therapy for Breast Cancer: Role of mTOR and Brk/ PTK6 as Molecular Targets

Breast cancer is a serious health issue and a major concern in biomedical research. Alteration in major signaling (viz. PI3K-AKT-mTOR, Ras-Raf-MEK-Erk, NF-kB, cyclin D1, JAK-STAT, Wnt, Notch, Hedgehog signaling and apoptotic pathway) contributes to the development of major subtypes of mammary carcinoma such as HER2 positive, TNBC, luminal A and B and normal-like breast cancer. Further, mutation and expression parameters of different genes involved in the growth and development of cells play an important role in the progress of different types of carcinoma, making gene therapy an emerging new therapeutic approach for the management of life-threatening diseases like cancer. The genetic targets (oncogenes and tumor suppressor genes) play a major role in the formation of a tumor. Brk/PTK6 and mTOR are two central molecules that are involved in the regulation of numerous signaling related to cell growth, proliferation, angiogenesis, survival, invasion, metastasis, apoptosis, and autophagy. Since these two proteins are highly upregulated in mammary carcinogenesis, this can be used as targeted genes for the treatment of breast cancer. However, not much work has been done on them. This review highlights the therapeutic significance of Brk and mTOR and their associated signaling in mammary carcinogenesis, which may provide a strategy to develop gene therapy for breast cancer management.

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.

IL-24-Armed Oncolytic Vaccinia Virus Exerts Potent Antitumor Effects via Multiple Pathways in Colorectal Cancer

Colorectal cancer is an aggressive malignancy for which there are limited treatment options. Oncolytic vaccinia virus is being developed as a novel strategy for cancer therapy. Arming vaccinia virus with immunostimulatory cytokines can enhance the tumor cell-specific replication and antitumor efficacy. Interleukin-24 (IL-24) is an important immune mediator, as well as a broad-spectrum tumor suppressor. We constructed a targeted vaccinia virus of Guang9 strain harboring IL-24 (VG9-IL-24) to evaluate its antitumor effects. In vitro, VG9-IL-24 induced an increased number of apoptotic cells and blocked colorectal cancer cells in the G₂/M phase of the cell cycle. VG9-IL-24 induced apoptosis in colorectal cancer cells via multiple apoptotic signaling pathways. In vivo, VG9-IL-24 significantly inhibited the tumor growth and prolonged the survival both in human and murine colorectal cancer models. In addition, VG9-IL-24 stimulated multiple antitumor immune responses and direct bystander antitumor activity. Our results indicate that VG9-IL-24 can inhibit the growth of colorectal cancer tumor by inducing oncolysis and apoptosis as well as stimulating the antitumor immune effects. These findings indicate that VG9-IL-24 may exert a potential therapeutic strategy for combating colorectal cancer.

Apoptin as a Tumor-Specific Therapeutic Agent: Current Perspective on Mechanism of Action and Delivery Systems

Cancer remains one of the leading causes of death worldwide in humans and animals. Conventional treatment regimens often fail to produce the desired outcome due to disturbances in cell physiology that arise during the process of transformation. Additionally, development of treatment regimens with no or minimum side-effects is one of the thrust areas of modern cancer research. Oncolytic viral gene therapy employs certain viral genes which on ectopic expression find and selectively destroy malignant cells, thereby achieving tumor cell death without harming the normal cells in the neighborhood. Apoptin, encoded by Chicken Infectious Anemia Virus' VP3 gene, is a proline-rich protein capable of inducing apoptosis in cancer cells in a selective manner. In normal cells, the filamentous Apoptin becomes aggregated toward the cell margins, but is eventually degraded by proteasomes without harming the cells. In malignant cells, after activation by phosphorylation by a cancer cell-specific kinase whose identity is disputed, Apoptin accumulates in the nucleus, undergoes aggregation to form multimers, and prevents the dividing cancer cells from repairing their DNA lesions, thereby forcing them to undergo apoptosis. In this review, we discuss the present knowledge about the structure of Apoptin protein, elaborate on its mechanism of action, and summarize various strategies that have been used to deliver it as an anticancer drug in various cancer models.

IL-24 Inhibits Lung Cancer Growth by Suppressing GLI1 and Inducing DNA Damage

Aberrant expression of GLI1 is responsible for aggressive tumor behavior and survival due to its effects on the DNA damage response (DDR). We investigated whether interleukin (IL)-24, a tumor suppressor, inhibits GLI1 and the associated DDR pathway in human NSCLCs. IL-24 treatment reduces mRNA and protein expression of GLI1 in lung tumor cells, but not in normal cells. GLI1 reporter assay and mRNA studies demonstrated that IL-24 regulates GLI1 at the post-transcriptional level by favoring mRNA degradation. Associated with GLI1 inhibition was marked suppression of the ATM-mediated DDR pathway resulting in increased DNA damage, as evidenced by γ-H2AX foci and Comet assay. Furthermore, attenuation of GLI1-associated DDR by IL-24 increased caspase-3 and PARP activity, resulting in cancer cell apoptosis. GLI1 inhibition and overexpression confirmed that IL-24-mediated anti-tumor effects involved the GLI-dependent pathway. Finally, we observed that IL-24-mediated alteration in GLI1 is independent of the canonical hedgehog-signaling pathway. Our study provides evidence that IL-24 treatment induces DNA damage, and reduces GLI1 expression and offers an opportunity for testing IL-24-based therapy for inhibiting GLI1 in lung cancer.

Mechanism of internalization of MDA-7/IL-24 protein and its cognate receptors following ligand-receptor docking

Melanoma differentiation associated gene-7 (mda-7/IL-24) is a member of the IL-10 family of cytokines, with ubiquitous direct and "bystander" tumor-selective killing properties. MDA-7/IL-24 protein binds distinct type II cytokine heterodimeric receptor complexes, IL-20R1/IL-20R2, IL-22R1/IL-20R1 and IL-22R1/IL-20R2. Recombinant MDA-7/IL-24 protein induces endogenous mda-7/IL-24 expression in a receptor-dependent manner; since A549 cells that lack a complete set of cognate receptors are not responsive to exogenous protein. The mechanism of MDA-7/IL-24 ligand-receptor biology is not well understood. We explored the interaction of MDA-7/IL-24 with its' receptors and the consequences of ligand-receptor docking. Using both pharmacological and genetic approaches we demonstrate that MDA-7/IL-24 internalization employs the clathrin-mediated endocytic pathway leading to degradation of receptors via the lysosomal/ubiquitin proteosomal pathway. This clathrin-mediated endocytosis is dynamin-dependent. This study resolves a novel mechanism of MDA-7/IL-24 protein "bystander" function, which involves receptor/protein-mediated internalization and receptor degradation.

Cancer terminator viruses (CTV): A better solution for viral-based therapy of cancer

In principle, viral gene therapy holds significant potential for the therapy of solid cancers. However, this promise has not been fully realized and systemic administration of viruses has not proven as successful as envisioned in the clinical arena. Our research is focused on developing the next generation of efficacious viruses to specifically treat both primary cancers and a major cause of cancer lethality, metastatic tumors (that have spread from a primary site of origin to other areas in the body and are responsible for an estimated 90% of cancer deaths). We have generated a chimeric tropism-modified type 5 and 3 adenovirus that selectively replicates in cancer cells and simultaneously produces a secreted anti-cancer toxic cytokine, melanoma differentiation associated gene-7/Interleukin-24 (mda-7/IL-24), referred to as a Cancer Terminator Virus (CTV) (Ad.5/3-CTV). In preclinical animal models, injection into a primary tumor causes selective cell death and therapeutic activity is also observed in non-injected distant tumors, that is, "bystander anti-tumor activity." To enhance the impact and therapeutic utility of the CTV, we have pioneered an elegant approach in which viruses are encapsulated in microbubbles allowing "stealth delivery" to tumor cells that when treated with focused ultrasound causes viral release killing tumor cells through viral replication, and producing and secreting MDA-7/IL-24, which stimulates the immune system to attack distant cancers, inhibits tumor angiogenesis and directly promotes apoptosis in distant cancer cells. This strategy is called UTMD (ultrasound-targeted microbubble-destruction). This novel CTV and UTMD approach hold significant promise for the effective therapy of primary and disseminated tumors.

IL-24 modulates the high mobility group (HMG) A1/miR222 /AKT signaling in lung cancer cells

Interleukin (IL)-24, a novel tumor suppressor/cytokine exhibits antitumor activity against a broad-spectrum of human cancer cells. In a recent study, we showed that IL-24 inhibited AKT in lung cancer cells. However, the molecular mechanism of AKT inhibition by IL-24 remains elusive.The high mobility group (HMG) A1 a member of the non-histone chromosomal proteins and commonly referred to as architectural transcription factor, regulates transcription of various genes involved in cell growth and survival. Overexpression of HMGA1 has been shown to be associated with tumor progression and metastasis in several cancers, including human lung cancer. A recent study demonstrated that HMGA1 activates AKT function by reducing the activity of the protein phosphatase, phosphatase 2A subunit B (PPP2R2A) via the oncogenic micro (mi) RNA-222. Based on this report we hypothesized that IL-24-mediated AKT inhibition involved the HMGA1/miR-222 axis.To test our hypothesis, in the present study we used a H1299 lung cancer cell line that expressed exogenous human IL-24 when induced with doxycycline (DOX). Induction of IL-24 expression in the tumor cells markedly reduced HMGA1 mRNA and protein levels. Using a mechanistic approach, we found that IL-24 reduced miR-222-3p and -5p levels, as determined by qRT-PCR. Associated with HMGA1 and miR-222 inhibition was a marked increase in PPP2R2A, with a concomitant decrease in phosphorylated AKTT308/S473 expression. SiRNA-mediated knockdown of HMGA1 in combination with IL-24 significantly reduced AKT T308/S473 protein expression and greatly reduced cell migration and invasion compared with individual treatments. Further combination of IL-24 and a miR-222-3p inhibitor significantly increased PPP2R2A expression.Our results demonstrate for the first time that IL-24 inhibits AKT via regulating the HMGA1/miR-222 signaling node in human lung cancer cells and acts as an effective tumor suppressor. Thus, a therapy combining IL-24 with HMGA1 siRNA or miR-222-3p inhibitor should present effective treatment of lung cancer.

RNA-binding protein CELF1 promotes tumor growth and alters gene expression in oral squamous cell carcinoma

The RNA binding protein CELF1 (also known as CUGBP1) is emerging as a critical regulator of cancer cell proliferation and apoptosis. Here, to provide a global prospective of CELF1 regulation of oral squamous cell carcinoma, we performed RNA-sequencing in oral cancer cells and CELF1 overexpression analysis in non-malignant human oral keratinocytes. Our approaches identified 1283 mRNAs differentially regulated as a function of CELF1 expression and more importantly CELF1 promoted alternative splicing of several target pre-mRNAs, which are known to be involved in various cancer biological processes. Overexpression of CELF1 in non-malignant human oral keratinocytes protected cells against oxidative damage and altered gene expression patterns. Finally, we provide evidence that reduction of CELF1 protein using a xenograft tumorigenesis mouse model decreased tumor growth. Altogether, these data provided a comprehensive view of the CELF1 mRNA regulatory network in oral cancer and suggests that CELF1 and/or its target mRNAs are viable candidates for therapeutic intervention.

MDA7/IL-24 is an anti-viral factor that inhibits influenza virus replication

Melanoma differentiation associated gene-7 (mda-7)/interleukin- 24 (IL-24) is a secreted cytokine, which plays an essential role in tumor suppression. Although its role as a multifunctional protein affecting broad types of cancers is well described, functions of IL-24 in host defense against virus infection are yet to be determined. In this study, we explored the anti-viral effect of recombinant IL-24 treatment during influenza infection. Infection of human lung adenocarcinoma cells (A549) with the influenza A virus up-regulated IL-24 mRNA and protein expression in a time-dependent manner. Pre-treatment of A549 cells with recombinant IL-24 protein effectively suppressed viral plaque formation. Furthermore, IL-24 treatment of A549 cells reduced viral non-structural protein 1 (NS1) synthesis, whereas IL-24 knockdown resulted in increased viral replication. Interestingly, IL-24 treatment following influenza A virus infection led to up-regulation of interferon (IFN)-induced antiviral signaling. Taken together, our results suggest that IL-24 exerts a potent suppressive effect on influenza viral replication and can be used in the treatment of influenza infection.

Phosphorylation of interleukin (IL)-24 is required for mediating its anti-cancer activity

Interleukin (IL)-24 is a tumor suppressor/cytokine gene that undergoes post-translational modifications (PTMs). Glycosylation and ubiquitination are important for IL-24 protein stabilization and degradation respectively. Little is known about IL-24 protein phosphorylation and its role in IL-24-mediated anti-tumor activities. In this study we conducted molecular studies to determine whether IL-24 phosphorylation is important for IL-24-mediated anti-cancer activity.

Human H1299 lung tumor cell line that was stably transfected with a doxycycline (DOX)-inducible (Tet-on) plasmid vector carrying the cDNA of IL-24-wild-type (IL-24^wt) or IL-24 with all five phosphorylation sites replaced (IL-24^mt) was used in the present study. Inhibition of tumor cell proliferation, cell migration and invasion, and induction of G2/M cell cycle arrest was observed in DOX-induced IL-24^wt-expressing cells but not in IL-24^mt-expressing cells. Secretion of IL-24^mt protein was greatly reduced compared to IL-24^wt protein. Further, IL-24^wt and IL-24^mt proteins markedly differed in their subcellular organelle localization. IL-24^wt but not IL-24^mt inhibited the AKT/mTOR signaling pathway. SiRNA-mediated AKT knockdown and overexpression of myristolyated AKT protein confirmed that IL-24^wt but not IL-24^mt mediated its anti-cancer activity by inhibiting the AKT signaling pathway.

Our results demonstrate that IL-24 phosphorylation is required for inhibiting the AKT/mTOR signaling pathway and exerting its anti-cancer activities.

IL-24 Induces Apoptosis via Upregulation of RNA-Activated Protein Kinase and Enhances Temozolomide-Induced Apoptosis in Glioma Cells

Human interleukin-24 (IL-24) has been found recently to play a tumor-suppressor role in a variety of tumors, including gliomas. However, the exact mechanism of glioma tumor suppression by IL-24 remains unclear. We collected by surgery 30 gliomas at different grades and evaluated IL-24 and double-stranded RNA-activated protein kinase (PKR) expression using fluorescence quantitative real-time PCR and immunohistochemical techniques. Two human glioma cell lines, U87 and U251, were transfected with Ad5F35-IL24 via recombinant adenovirus-mediated gene transfer and apoptosis, as well as PKR and eIF-2α expression analyzed. The results showed that IL-24 and PKR expression decreased with increasing tumor grade. Compared with cells of the control groups, Ad5F35-IL24-infected U87 and U251 cells exhibited a significantly increased apoptosis and elevated PKR, eIF-2α, p-PKR, and p-eIF-2α levels, while the expression of Bcl-2 was decreased. Finally, IL-24 also sensitized apoptosis of glioma cells to temozolomide (TMZ). This study indicates that IL-24 upregulates expression and activation of PKR, further increasing expression and activation of eIF-2α, and decreasing Bcl-2 to promote apoptosis. IL-24 also increases chemosensitivity of glioma cells to TMZ.

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.

IL-24 inhibits lung cancer cell migration and invasion by disrupting the SDF-1/CXCR4 signaling axis

Background

The stromal cell derived factor (SDF)-1/chemokine receptor (CXCR)-4 signaling pathway plays a key role in lung cancer metastasis and is molecular target for therapy. In the present study we investigated whether interleukin (IL)-24 can inhibit the SDF-1/CXCR4 axis and suppress lung cancer cell migration and invasion in vitro. Further, the efficacy of IL-24 in combination with CXCR4 antagonists was investigated.

Methods

Human H1299, A549, H460 and HCC827 lung cancer cell lines were used in the present study. The H1299 lung cancer cell line was stably transfected with doxycycline-inducible plasmid expression vector carrying the human IL-24 cDNA and used in the present study to determine the inhibitory effects of IL-24 on SDF-1/CXCR4 axis. H1299 and A549 cell lines were used in transient transfection studies. The inhibitory effects of IL-24 on SDF1/CXCR4 and its downstream targets were analyzed by quantitative RT-PCR, western blot, luciferase reporter assay, flow cytometry and immunocytochemistry. Functional studies included cell migration and invasion assays.

Principal Findings

Endogenous CXCR4 protein expression levels varied among the four human lung cancer cell lines. Doxycycline-induced IL-24 expression in the H1299-IL24 cell line resulted in reduced CXCR4 mRNA and protein expression. IL-24 post-transcriptionally regulated CXCR4 mRNA expression by decreasing the half-life of CXCR4 mRNA (>40%). Functional studies showed IL-24 inhibited tumor cell migration and invasion concomitant with reduction in CXCR4 and its downstream targets (pAKT^S473, pmTOR^S2448, pPRAS40^T246 and HIF-1α). Additionally, IL-24 inhibited tumor cell migration both in the presence and absence of the CXCR4 agonist, SDF-1. Finally, IL-24 when combined with CXCR4 inhibitors (AMD3100, SJA5) or with CXCR4 siRNA demonstrated enhanced inhibitory activity on tumor cell migration.

Conclusions

IL-24 disrupts the SDF-1/CXCR4 signaling pathway and inhibits lung tumor cell migration and invasion. Additionally, IL-24, when combined with CXCR4 inhibitors exhibited enhanced anti-metastatic activity and is an attractive therapeutic strategy for lung metastasis.

Enhanced SOX2 expression in retinoblastoma tissues and peripheral blood is associated with the clinicopathological characteristics of the disease

The present study aimed to investigate the association between the expression of sex-determining region Y box 2 (SOX2) in retinoblastoma (Rb) tissues and peripheral blood, and the clinicopathological characteristics of Rb. The expression of SOX2 in Rb tissues was detected by immunohistochemical staining and western blot analysis. SOX2 expression in the peripheral blood of children with Rb was determined using quantitative real-time polymerase chain reaction. The correlation between SOX2 expression and the clinicopathological characteristics of Rb was analyzed using χ² tests. The positive rate of SOX2 in Rb tissues was 82.2%, while the expression of SOX2 in the control group tissues was negative. Western blot analysis detected a higher expression of SOX2 in the Rb tissues than in the control group tissues. Poorly differentiated Rb tissues exhibited significantly higher levels of SOX2 expression compared with the well-differentiated Rb tissues. SOX2 expression was higher in the peripheral blood of children with Rb than in individuals from the control group. The level of SOX2 expression in the peripheral blood of the poorly differentiated group was higher than that of the well-differentiated group. Enhanced SOX2 expression in Rb tissues and peripheral blood was closely associated with the clinicopathological characteristics of Rb. Therefore, SOX2 may be a novel target biomarker for the clinical diagnosis and treatment of Rb.

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.

Melanoma differentiation associated gene-7/interleukin-24 induces caspase-3 denitrosylation to facilitate the activation of cancer cell apoptosis

Melanoma differentiation-associated gene-7 (mda-7)/interleukin-24 (IL-24) induces caspase-3 cleavage and subsequent activation via the intrinsic or extrinsic pathway to result in cancer cell-selective apoptosis, but whether mda-7/IL-24 may directly regulate caspase-3 through the post-translational modification remains unknown. Here, we reported that tumor-selective replicating adenovirus ZD55-IL-24 led to caspase-3 denitrosylation and subsequent activation, indicating that caspase-3 denitrosylation played a crucial role in ZD55-IL-24-induced cancer cell apoptosis. To confirm the relationship between caspase-3 denitrosylation and its activation in response to ZD55-IL-24, we treated carcinoma cells with the different nitric oxide (NO) regulators to modulate caspase-3 denitrosylation level, then observed the corresponding caspase-3 cleavage. We found that NO inhibitor 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxy-3-oxide (PTIO) promoted caspase-3 denitrosylation and caspase-3 cleavage, thereby exacerbating ZD55-IL-24-induced cancer cell apoptosis, whereas NO donor sodium nitroprusside (SNP) showed the opposite effect. Moreover, caspase-3 denitrosylation facilitated its downstream target poly ADP-ribose polymerase (PARP) degradation that further increased the apoptotic susceptibility. Although caspase-3 activation controlled by denitrosylation modification has emerged as an important regulator of programmed cell death, the detailed molecular mechanism by which caspase-3 exerts its denitrosylation modification in response to ZD55-IL-24 still needs to be elucidated. Thus, our results demonstrated that ZD55-IL-24 increased Fas expression to enhance thioredoxin reductase 2 (TrxR2), which was responsible for caspase-3 denitrosylation. Collectively, these findings elucidate that ZD55-IL-24 induces caspase-3 denitrosylation through Fas-mediated TrxR2 enhancement, thereby facilitating caspase-3 cleavage and the downstream caspase signaling pathway activation, which provides a novel insight into ZD55-IL-24-induced cancer-specific apoptosis by post-translational modification of the apoptotic executor caspase-3.

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.

Expression of IL-24 and IL-24 receptors in human wound tissues and the biological implications of IL-24 on keratinocytes

Interleukin (IL)-24, also known as melanoma differentiation-associated gene-7, is a cytokine initially identified from cancerous cells and expressed in a range of cell types. It is a regulator of cell differentiation, growth, and apoptosis, and a promising anticancer agent. IL-24 acts via its heterodimic receptors: the IL-20R1 and IL-20R2 complex and the IL-22R1 and IL-20R2 complex. There is limited information on the effect of IL-24 in wound healing. Human acute and chronic wound tissues were used to analyze the transcript levels and histological staining of IL-24 and the IL-24 receptors. The biological response of human keratinocytes to recombinant human IL-24 was evaluated using electric cell-substrate impedance sensing-based methods in conjunction with inhibitors to candidate signaling pathways. IL-24 significantly slowed the migration of keratinocytes (p = 0.01), with only a marginal effect on cellular adhesion. The inhibitory effect of IL-24 on migration was completed reversed following addition of an AKT inhibitor (p = 0.004) but not an SMAD3 pathway inhibitor. Human chronic wound tissues showed raised levels of both IL-24 (p = 0.003) and its receptor (p = 0.0305) compared with acute wound tissues. We conclude that IL-24 appears to promote wound chronicity via its inhibitory effect on the migratory behavior of human keratinocytes, mediated through an AKT-dependent pathway.

IL-2 regulates the expression of the tumor suppressor IL-24 in melanoma cells

Melanoma is notoriously resistant to chemotherapy, but variable responses to biotherapies, including the IFNs and IL-2, provide intriguing avenues for further study. Systemic IL-2 treatment has provided significant clinical benefit in a minority of patients with metastatic melanoma, leading to long-term survival in a few cases. We hypothesize that one previously unidentified mechanism of effective IL-2 therapy is through direct upregulation of the tumor suppressor IL-24 in melanoma tumor cells resulting in growth suppression. In this study, five melanoma cell lines were treated with high dose recombinant human IL-2. Three (A375, WM1341, WM793) showed statistically significant increases in IL-24 protein; two (WM35, MeWo) remained negative for IL-24 message and protein. This increase was abolished by preincubating with anti-IL-2 antibody or blocking with antibodies against the IL-2 receptor chains. These IL-2 responsive melanoma cell lines expressed IL-2Rβ and IL-2Rγ mRNA. The IL-2Rβγ complex was functional, as measured by IL-2-induced signal transducers and activators of transcription activation as well as IL-15 signaling through its shared receptor complex. IL-24 upregulation was observed in response to either IL-2 or IL-15. Cell growth was significantly decreased by treatment of IL-24-positive cells with IL-2 or IL-15, whereas no effect was seen in negative cells. Incubating the IL-24 inducible-cells with anti-IL-24 antibody as well as transfecting with IL-24 small interfering RNA effectively reversed the growth suppression seen with IL-2. Thus, we have shown that one mechanism of clinically effective IL-2 therapy may be the direct action of IL-2 on a biologically distinct subset of melanoma cells leading to upregulation of the tumor suppressor IL-24.

Splice variants of mda-7/IL-24 differentially affect survival and induce apoptosis in U2OS cells

Interleukin-24 (mda-7/IL-24) is a cytokine in the IL-10 family that has received a great deal of attention for its properties as a tumor suppressor and as a potential treatment for cancer. In this study, we have identified and characterized five alternatively spliced isoforms of this gene. Several, but not all of these isoforms induce apoptosis in the osteosarcoma cell line U2OS, while none affect the survival of the non-cancerous NOK cell line. One of these isoforms, lacking three exons and encoding the N-terminal end of the mda-7/IL-24 protein sequence, caused levels of apoptosis that were higher than those caused by the full-length mda-7/IL-24 variant. Additionally, we found that the ratio of isoform expression can be modified by the splice factor SRp55. This regulation suggests that alternative splicing of mda-7/IL-24 is under tight control in the cell, and can be modified under various cellular conditions, such as DNA damage. In addition to providing new insights into the function of an important tumor suppressor gene, these findings may also point toward new avenues for cancer treatment.

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.

MicroRNA-205-directed transcriptional activation of tumor suppressor genes in prostate cancer

BACKGROUND

MicroRNAs (miRNAs) are small noncoding RNAs that regulate the expression of approximately 60% of all human genes. They play important roles in numerous cellular processes, including development, proliferation, and apoptosis. Currently, it is believed that miRNAs elicit their effect by silencing the expression of target genes. In this study, the authors demonstrated that miRNA-205 (miR-205) induced the expression the interleukin (IL) tumor suppressor genes IL24 and IL32 by targeting specific sites in their promoters.

METHODS

The methods used in this study included transfection of small RNAs; quantitative real-time polymerase chain reaction; in situ hybridization; fluorescence-labeled in situ hybridization; cell cycle, apoptosis, cell viability, migratory, clonability, and invasion assays; immunoblotting; and luciferase reporter, nuclear run-on, and chromatin immunoprecipitation assays.

RESULTS

The results revealed that miR-205 was silenced in prostate cancer. Its re-expression induced apoptosis and cell cycle arrest. It also impaired cell growth, migration, clonability, and invasiveness of prostate cancer cells. Micro-RNA-205 induced the expression of tumor suppressor genes IL24 and IL32 at both the messenger RNA and protein levels. The induction of in vitro transcription and enrichment of markers for transcriptionally active promoters in the IL24 and IL32 genes was observed in response to miR-205.

CONCLUSIONS

In this study, a new function for miR-205 was identified that specifically activated tumor suppressor genes by targeting specific sites in their promoters. These results corroborate a newly identified function that miRNAs have in regulating gene expression at the transcriptional level. The specific activation of tumor suppressor genes (eg, IL24, IL32) or other dysregulated genes by miRNA may contribute to a novel therapeutic approach for the treatment of prostate cancer.

HDAC4 inhibits the transcriptional activation of mda-7/IL-24 induced by Sp1

Melanoma differentiation-associated gene/interleukin-24 (mda-7/IL-24) is a cytokine that can activate monocytes and T helper 2 cells. The expression of mda-7/IL-24 gradually fades with the progression of melanoma, and it is undetectable at the metastatic stage. Ectopic expression of mda-7/IL-24 selectively suppresses growth and induces apoptosis in cancer cells with little harm to normal cells. However, the transcriptional regulation of the mda-7/IL-24 gene has not been extensively studied. In this study, we show that the expression of mda-7/IL-24 was upregulated by the histone deacetylase (HDAC) inhibitors trichostatin A (TSA) and sodium butyrate (NaBu), whereas it was downregulated by HDAC4. We also found that the histone acetylation level and the binding of the transcriptional factor Sp1 to the mad-7 promoter were reduced upon HDAC4 treatment. Moreover, the HDAC inhibitor TSA induced histone hyperacetylation and stimulated Sp1 binding to the mda-7/IL-24 promoter, which in turn enhanced the expression of mda-7/IL-24. Therefore, we conclude that histone acetylation modification plays an important role in the regulation of mda-7/IL-24 and that the transcription factor Sp1 participates in this process.

Inhibition of autophagy induced by overexpression of mda-7/interleukin-24 strongly augments the antileukemia activity in vitro and in vivo

Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) is a novel candidate of tumor suppressor that can selectively induce apoptosis experimentally in a spectrum of human cancer cells including leukemia cells. However, a recent study suggests that mda-7/IL-24 promotes the survival of chronic lymphocytic leukemia B-cells. In this study, we showed that mda-7/IL-24 was constitutively expressed in leukemia cell lines and primary acute myeloid leukemia samples. Using a conditionally replicating adenovirus expressing mda-7/IL-24 (ZD55-IL-24), we showed that enforced expression of mda-7/IL-24 in leukemia cells induced autophagy, which was triggered by the upregulation of Beclin-1. Immunofluorescence and coimmunoprecipitation studies suggested that mda-7/IL-24 protein interacts with Beclin-1. Class III PI3K/Beclin-1 complex was shown involved in the mda-7/IL-24-induced autophagy. Moreover, autophagy inhibition by phosphatidylinositol 3-kinase inhibitor, wortmannin, resulted in a reduced Beclin-1 expression and autophagosome formation associated with significantly enhanced cell death. Importantly, the combination of ZD55-IL-24 with wortmannin elicited a strongly enhanced antileukemia efficacy in established leukemia xenografts. These results suggest that mda-7/IL-24-induced autophagy in leukemia cells may provide survival advantage and mda-7/IL-24 combined with agents that disrupt autophagy is a promising new strategy for the treatment of leukemia.

Regulation of Msx2 Gene Expression by Steroid Hormones in Human Nonmalignant and Malignant Breast Cancer Explants Cultured in Vitro

Muscle segment homeobox genes, which regulate developmental programs and are expressed in embryonic and adult tissue, play a role in development of some malignancies. There are no reports on the expression of these families of genes in breast cancer tissue. The aim of this study was to compare expression of Msx2 gene in breast cancer of different genotypes as well as in surrounding nonmalignant tissues. Explants obtained during surgery were divided according to their sex steroid receptor status determined by immunocytochemistry. Four explants obtained from malignant and nonmalignant tissue of each individual patient were incubated in a control medium or with the addition of progesterone (10(-7) M) alone, estradiol 17 beta (10(-5) M) or both. The relative level of Msx2 transcripts was evaluated by a semiquantitative RT-PCR and cell proliferation by Alamar Blue test. Results of RT-PCR analysis showed that the relative expression of Msx2 gene depended on the presence of ER/PR receptors both in nonmalignant and malignant tissues Relative amount of Msx2 mRNA was the highest in surrounding nonmalignant ER+/PR- and ER-/PR+ tissue, whereas in ER-/PR- and ER+/PR+ tissue it was 1.4-1.6-fold lower. Tumorigenesis led to about a twofold decrease in the relative amount of Msx2 mRNA except for ER+/PR+ immunophenotype, where no changes were observed. Addition of estradiol or progesterone to the culture of ER-/PR- type tissue explants did not change significantly the relative amount of Msx2 gene mRNA. An opposite effect was observed in ER+/PR- type of tissue. Addition of estradiol alone, or estradiol and progesterone together to tissue culture explants decreased two to three fold the relative amount of Msx2 gene mRNA in both, malignant and surrounding tissues. Progesterone alone had no effect on Msx2 gene expression in this type of tissue. The most complicated regulation was observed in ER+/PR+ type of tissue. Culture of tissue explants supplemented with estradiol significantly increased the relative amount of Msx2 gene mRNA in the surrounding tissue. Progesterone enhanced the stimulatory effect of estradiol in surrounding tissues but not in the malignant tissue. Increased expression of Msx2 correlated with an increased proliferation in ER-/PR- and ER+/PR+ types, but not in ER+/PR- type of tissues. In conclusion, obtained results provide evidence that estrogen affects Msx2 gene expression. Significant changes in the relative amount of Msx2 gene mRNA and lack of canonical ERE element in 5'-upstream sequence of this gene suggest that regulation takes place indirectly probably by protein-protein interaction. The decrease in the relative amount of Msx2 gene mRNA in ER+/PR- type tumor suggests that progesterone also affects Msx2 gene expression by an indirect mechanism(s).

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.

A novel splicing variant of mouse interleukin (IL)-24 antagonizes IL-24-induced apoptosis

Alternative splicing of mRNA enables functionally diverse protein isoforms to be expressed from a single gene, allowing transcriptome diversification. Interleukin (IL)-24/MDA-7 is a member of the IL-10 gene family, and FISP (IL-4-induced secreted protein), its murine homologue, is selectively expressed and secreted by T helper 2 lymphocytes. A novel splice variant of mouse IL-24/FISP, designated FISP-sp, lacks 29 nucleotides from the 5'-end of exon 4 of FISP. The level of FISP-sp expression is 10% of the level of total primary FISP transcription. Unlike FISP, FISP-sp does not induce growth inhibition and apoptosis. FISP-sp is exclusively localized in endoplasmic reticulum, and its expression is up-regulated by endoplasmic reticulum stress. Our results suggest that the novel splicing variant FISP-sp dimerizes with FISP and blocks its secretion and inhibits FISP-induced apoptosis in vivo.

Adenoviral endoplasmic reticulum-targeted mda-7/interleukin-24 vector enhances human cancer cell killing

We developed several adenoviral vectors designed to target MDA-7 expression to different subcellular compartments [endoplasmic reticulum (ER), mitochondria, nucleus, and cytosol] and evaluated their ability to enhance apoptosis. Adenoviral ER-targeted mda-7/interleukin-24 vector (Ad-ER-mda7) selectively and effectively inhibited the growth and proliferation of lung (A549 and H1299) and esophageal (Seg1 and Bic1) cancer cells by enhancing cell killing. Both Ad-mda7 and Ad-ER-mda7 activated a novel pathway of ER stress-induced apoptosis characterized by unregulated expression of phosphorylated JNK, phosphorylated c-Jun, and phosphorylated RNA-dependent protein kinase. Caspase-4 activation mediated Ad-mda7- and Ad-ER-mda7-induced cell death. In addition, Ad-mda7- and Ad-ER-mda7-mediated growth inhibition correlated with activation of ER molecular markers RNA-dependent protein kinase and JNK both in vitro (in Ad-mda7- or Ad-ER-mda7-treated lung cancer cells) and in vivo. These findings suggest that vectors targeting the ER (Ad-ER-mda7) may be more effective in cancer gene therapy possibly through more effective induction or ER stress pathways.

Killing of human melanoma cells induced by activation of class I interferon-regulated signaling pathways via MDA-7/IL-24

Restoration of the tumor-suppression function by gene transfer of the melanoma differentiation-associated gene 7 (MDA7)/interleukin 24 (IL-24) successfully induces apoptosis in melanoma tumors in vivo. To address the molecular mechanisms involved, we previously revealed that MDA7/IL-24 treatment of melanoma cells down-regulates interferon regulatory factor (IRF)-1 expression and concomitantly up-regulates IRF-2 expression, which competes with the activity of IRF-1 and reverses the induction of IRF-1-regulated inducible nitric oxide synthase (iNOS). Interferons (IFNs) influence melanoma cell survival by modulating apoptosis. A class I IFN (IFN-alpha) has been approved for the treatment of advanced melanoma with some limited success. A class II IFN (IFN-gamma), on the other hand, supports melanoma cell survival, possibly through constitutive activation of iNOS expression. We therefore conducted this study to explore the molecular pathways of MDA7/IL-24 regulation of apoptosis via the intracellular induction of IFNs in melanoma. We hypothesized that the restoration of the MDA7/IL-24 axis leads to upregulation of class I IFNs and induction of the apoptotic cascade. We found that MDA7/IL-24 induces the secretion of endogenous IFN-beta, another class I IFN, leading to the arrest of melanoma cell growth and apoptosis. We also identified a series of apoptotic markers that play a role in this pathway, including the regulation of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and Fas-FasL. In summary, we described a novel pathway of MDA7/IL-24 regulation of apoptosis in melanoma tumors via endogenous IFN-beta induction followed by IRF regulation and TRAIL/FasL system activation.

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.

MDA-7/IL-24, a novel tumor suppressor/cytokine is ubiquitinated and regulated by the ubiquitin-proteasome system, and inhibition of MDA-7/IL-24 degradation enhances the antitumor activity

Steady-state protein levels are determined by the balance between protein synthesis and degradation. Protein half-lives are determined primarily by degradation, and the major degradation pathways involve either lysosomal destruction or an ATP-dependent process involving ubiquitination to target proteins to the proteosome. Studies have shown that multiple tumor-suppressor proteins are ubiquitinated and degraded by the 26S proteasome. In the present study, we investigated whether the tumor suppressor/cytokine melanoma differentiation-associated gene-7/interleukin-24 gene (MDA-7/IL-24) protein is ubiquitinated and its degradation controlled by the proteasome. Treatment of ovarian (2008) and lung (H1299) tumor cells with adenoviral delivery of mda-7 (Ad-mda7) or Ad-mda7 plus the proteosome inhibitor MG132 showed that MDA-7 protein expression was dependent upon proteosome activity. Western blot and immunoprecipitation analyses verified that the MDA-7 protein was ubiquitinated and that ubiquitinated-MDA-7 levels were increased in MG132-treated cells. These results were confirmed using small interfering RNA (siRNA)-mediated knockdown of ubiquitin. Furthermore, ubiquitinated MDA-7 protein was degraded by the 26S proteasome, as MDA-7 accumulation was observed only when cells were treated with MG132 but not with lysosome or protease inhibitors. Inhibition of the catalytic beta-5 subunit of the 20S proteasome using siRNA resulted in MDA-7 protein accumulation. Finally, treatment of tumor cells with Ad-mda7 plus the proteasome inhibitor bortezomib resulted in increased tumor cell killing. Our results show that MDA-7/IL-24 is ubiquitinated and degraded by the 26S proteasome. Furthermore, inhibition of MDA-7 degradation results in enhanced tumor killing, identifying a novel anticancer strategy.

Adenovirus-mediated Il-24 expression suppresses hepatocellular carcinoma growth via induction of cell apoptosis and cycling arrest and reduction of angiogenesis

Previous studies have shown that interleukin (IL)-24 as a novel tumor suppressor gene has tumor-suppressor activity in a broad spectrum of human cancer cells both in vitro and in vivo. In this study, we explored the potential effect of adenovirus-mediated IL-24 gene therapy on human hepatocellular carcinoma (HCC) by using a HCC cell line, SMMC-7721. We constructed a recombinant adenovirus, AdVGFP/IL-24 expressing the marker green fluorescent protein (GFP) and the tumor-suppressor gene, IL-24. We demonstrated that AdVGFP/IL-24 treatment of SMMC-7721 cells in vitro significantly induced HCC cell cytotoxicity and apoptosis, and altered HCC cell cycling with an S-phase reduction and G2/M phase arrest, compared with AdVGFP, without IL-24 expresssion (p < 0.05). Furthermore, we also showed that the treatment of SMMC-7721 tumors by an intratumoral injection of AdVGFP/IL-24 significantly suppressed in vivo HCC growth in athymic nude mice, compared with AdVGFP treatment (p < 0.05). In addition, we also elucidated the molecular mechanism responsible for AdVGFP/IL-24-associated tumor suppression. These include: (1) upregulation of p53-independent apoptosis-associated caspase-3 and (2) downregulation of angiogenesis-associated vascular endothelial growth factor and CD34. Therefore, this study will provide a framework for future clinical applications of AdVGFP/IL-24 in HCC gene therapy.

mda-7 In combination with bevacizumab treatment produces a synergistic and complete inhibitory effect on lung tumor xenograft

Bevacizumab, a humanized monoclonal antibody against vascular endothelial growth factor (VEGF), has shown antitumor activity by inhibiting tumor angiogenesis in preclinical and clinical studies. However, bevacizumab monotherapy does not induce complete tumor regression. Therefore, additional treatments must be combined with bevacizumab to promote tumor regression. We previously showed that melanoma differentiation associated gene-7 (mda-7) protein exerts potent antitumor and antiangiogenic activity. Thus, in this study, we investigated the therapeutic effects of mda-7 in combination with bevacizumab using lung cancer as a model. In vitro, treatment of human umbilical vein endothelial cells with conditioned medium from Ad-mda7 plus bevacizumab-treated lung tumor cells showed reduced VEGF ligand-receptor binding, and decreased cell survival, resulting in growth arrest and apoptosis. In vivo, treatment of subcutaneous lung tumor xenografts with bevacizumab plus Ad-mda7 resulted in significant tumor growth inhibition and improved survival compared to tumor growth in control mice. Furthermore, tumors in all the Ad-mda7 plus bevacizumab-treated mice completely regressed, and these were tumor free through the study's end. Molecular analysis showed enhanced tumor cell apoptosis and reduced VEGF and CD31 expression in Ad-mda7 plus bevacizumab-treated tumors. Thus, Ad-mda7 and bevacizumab treatment produces a synergistic and complete therapeutic effect against human lung cancer.

Vitamin E succinate in combination with mda-7 results in enhanced human ovarian tumor cell killing through modulation of extrinsic and intrinsic apoptotic pathways

Adenovirus-mediated mda-7 (Ad-mda7) gene transfer has been shown to induce apoptosis in various human cancer cells while sparing normal cells. Vitamin E succinate (VES) is also known to exhibit antitumor activity against a number of human cancer cell lines. We hypothesized that a combination of the two agents would produce an enhanced antitumor effect in MDAH2774 human ovarian cancer cells. Treatment of MDAH2774 cells with Ad-mda7 plus VES resulted in enhanced antitumor activity that involved the activation of two apoptotic pathways. Activation of the extrinsic pathway was demonstrated by increased cell-surface Fas expression and cleavage of Bid and caspase-8. Activation of the intrinsic pathway was demonstrated by disruption of mitochondrial potential; and activation of downstream capase-9 and caspase-3 via cytochrome C release. In contrast, the combination of Ad-mda7 plus VES did not show any antitumor activity against normal fibroblasts, indicating selective tumor cell killing. Our in vitro results provide a basis for further preclinical testing of Ad-mda7 plus VES as a potential cancer treatment strategy.

Inhibition of nuclear factor-κB augments antitumor activity of adenovirus-mediated melanoma differentiation-associated gene-7 against lung cancer cells via mitogen-activated protein kinase kinase kinase 1 activation

Nuclear factor-kappaB (NF-kappaB) activation promotes cell survival and growth. Reports show that chemotherapeutic agents and cytokines that are used for cancer therapy activate NF-kappaB expression in tumor cells and its suppression enhanced the antitumor activity. We hypothesized that adenovirus-mediated overexpression of melanoma differentiation-associated gene-7/interleukin-24 (Ad-mda7/IL-24) induces NF-kappaB expression and that inhibition of this expression results in enhanced tumor cell killing. Treatment of human lung tumor (H1299 and A549) cells with Ad-mda7 resulted in NF-kappaB activation in a dose- and time-dependent manner before activation of cell death pathways. To establish that inhibition of Ad-mda7-mediated NF-kappaB activation results in enhanced tumor cell killing, H1299 cells that overexpress the dominant-negative I kappa B alpha (dnI kappa B alpha) were treated with Ad-mda7 in vitro. An enhanced growth arrest and apoptosis was observed in Ad-mda7-treated H1299-dnI kappa B alpha compared with H1299-Neo cells. This Ad-mda7-mediated enhanced killing of H1299-dnI kappa B alpha cells involved cleavage of mitogen-activated protein kinase kinase kinase 1 (MEKK1) and caspase-3 in a feedback loop mechanism. The inhibition of MEKK1 or caspase-3 cleavage in H1299-dnI kappa B alpha cells resulted in reduced Ad-mda7-mediated cell killing. In vivo, the treatment of H1299-dnI kappa B alpha s.c. tumors with Ad-mda7 resulted in increased drug sensitivity and delayed the tumor growth rate compared with Ad-mda7-treated H1299-Neo tumors. Molecular analysis of Ad-mda7-treated H1299-dnI kappa B alpha tumors showed increased MEKK1 cleavage and activation of caspase-3 compared with Ad-mda7-treated H1299-Neo tumors. Our findings thus showed that the NF-kappaB activation induced by Ad-mda7 treatment of lung cancer cells is an intrinsic survival mechanism and that the inhibition of this NF-kappaB expression results in enhanced tumor cell killing.

Combinatorial treatment of non-small-cell lung cancers with gefitinib and Ad.mda-7 enhances apoptosis-induction and reverses resistance to a single therapy

Activation of the epidermal growth factor receptor (EGFR) contributes to the pathogenesis of non-small-cell lung carcinomas (NSCLC) and gefitinib, a selective reversible EGFR inhibitor, is effective in treating patients with NSCLC. However, clinical resistance to gefitinib is a frequent occurrence highlighting the need for improved therapeutic strategies. Melanoma differentiation associated gene-7 (mda-7)/Interleukin-24 (IL-24) (mda-7/IL-24) displays cancer-selective apoptosis induction when delivered via a replication-incompetent adenovirus (Ad.mda-7). In this study, the effect of Ad.mda-7 infection, either alone or in combination with gefitinib, was analyzed in a panel of NSCLC cell lines carrying wild-type EGFR (H-460 and H-2030) or mutant EGFR (H-1650 and H-1975). While H-2030 and H-1650 cells were sensitive, H-460 and H-1975 cells were resistance to growth inhibition by Ad.mda-7, which was reversed by the combination of Ad.mda-7 and gefitinib. This combination increased MDA-7/IL-24 and downstream effector double-stranded RNA-activated protein kinase (PKR) protein expression, promoting apoptosis induction of NSCLC cells. Inhibition of PKR significantly inhibited apoptosis induction by Ad.mda-7 when administered alone but not when used in combination with gefitinib. The combination treatment also augmented inhibition of EGFR signaling. Our findings indicate that a combinatorial treatment with Ad.mda-7 and gefitinib may provide benefit in the treatment of NSCLC, especially in patients displaying resistance to clinically used EGFR inhibitors.

MDA-7/IL-24 suppresses human ovarian carcinoma growth in vitro and in vivo

Background

Previous studies showed that the human melanoma differentiation-associated gene-7 (mda-7), also known as interleukin-24 (IL-24), has potent antitumor activity against human and murine cancer cells. However, the majority of these studies were limited to in vitro testing. In the present study, we investigated the antitumor activity of mda-7/IL-24 against human ovarian cancer cells both in vitro and in vivo.

Results

In vitro, treatment of ovarian cancer cells with an adenoviral vector carrying the mda-7 gene (Ad-mda7) resulted in inhibition of cell proliferation and induction of cell cycle arrest, leading to apoptosis. We did not observe inhibitory activity in Ad-mda7-treated normal cells. In vivo, treatment of subcutaneous tumor xenografts with Ad-mda7 resulted in significant tumor growth inhibition when compared with that in control groups (p < 0.001). Molecular analysis of ovarian tumor tissue lysates treated with Ad-mda7 showed that MDA-7 protein expression was associated with activation of the caspase cascade.

Conclusion

Our results show that treatment of ovarian cancer cells with mda-7/IL-24 results in growth suppression both in vitro and in vivo.

Human interleukin 24 (MDA-7/IL-24) protein kills breast cancer cells via the IL-20 receptor and is antagonized by IL-10

The melanoma differentiation-associated gene-7 (mda-7/IL-24) is a unique member of the interleukin 10 (IL-10) family of cytokines, with ubiquitous tumor cell pro-apoptotic activity. Recent data have shown that IL-24 is secreted as a glycosylated protein and functions as a pro-Th1 cytokine and as a potent anti-angiogenic molecule. In this study, we analyzed the activity of Ad-mda7 and its protein product, secreted IL-24, against human breast cancer cells. We show that Ad-mda7 transduction of human breast cancer cells results in G(2)/M phase cell cycle arrest and apoptotic cell death, which correlates with secretion of IL-24 protein. Neutralizing antibody against IL-24 significantly inhibited Ad-mda7 cytotoxicity. IL-24 and IL-10 both engage their cognate receptors on breast cancer cells resulting in phosphorylation and activation of STAT3, however, IL-10 receptor binding failed to induce cell killing, indicating that tumor cell killing by IL-24 is independent of STAT3 phosphorylation. Treatment with exogenous IL-24 induced apoptosis in breast cancer cells and this effect was abolished by addition of anti-IL-24 antibody or anti-IL-20R1, indicating that bystander cell killing is mediated via IL-24 binding to the IL-20R1/IL-20R2 heterodimeric receptor complex. Co-administration of the related cytokine IL-10 inhibited killing mediated by IL-24 and concomitantly inhibited IL-24 mediated up-regulation of the tumor suppressor proteins, p53 and p27(Kip1). In summary, we have defined a tumor-selective cytotoxic bystander role for secreted IL-24 protein and identified a novel receptor-mediated death pathway in breast cancer cells, wherein the related cytokines IL-24 and IL-10 exhibit antagonistic activity.