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

Recent advances in oncolytic virus therapy for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a highly refractory cancer and the fourth leading cause of cancer-related mortality worldwide. Despite the development of a detailed treatment strategy for HCC, the survival rate remains unsatisfactory. Oncolytic virus has been extensively researched as a new cancer therapeutic agent in the treatment of HCC. Researchers have designed a variety of recombinant viruses based on natural oncolytic diseases, which can increase the targeting of oncolytic viruses to HCC and their survival in tumors, as well as kill tumor cells and inhibit the growth of HCC through a variety of mechanisms. The overall efficacy of oncolytic virus therapy is known to be influenced by anti-tumor immunity, toxic killing effect and inhibition of tumor angiogenesis, etc. Therefore, a comprehensive review of the multiple oncolytic mechanisms of oncolytic viruses in HCC has been conducted. So far, a large number of relevant clinical trials are under way or have been completed, and some encouraging results have been obtained. Studies have shown that oncolytic virus combined with other HCC therapies may be a feasible method, including local therapy, chemotherapy, molecular targeted therapy and immunotherapy. In addition, different delivery routes for oncolytic viruses have been studied so far. These studies make oncolytic virus a new and attractive drug for the treatment of HCC.

WT1 Inhibits Human Renal Carcinoma Cell Proliferation and Induces G2/M Arrest by Upregulating IL-24 Expression

The transcription factor Wilms’ tumor 1 (WT1) is involved in development, tissue homeostasis, and disease. However, the exact roles and the mechanisms of WT1 in renal carcinoma are not well understood. Therefore, in this study, we evaluated the ability of WT1 to block proliferation in renal carcinoma cells in vitro. Experimental analysis showed that WT1 overexpression inhibited the proliferation of renal carcinoma A498 cells and promoted arrest at the G2/M checkpoint. RNA-Seq identified differentially expressed genes, including IL-24, related to both the cell proliferation and the cell cycle. WT1 overexpression upregulated IL-24 expression, and IL-24 overexpression induced G2/M arrest. ChIP-Seq identified JUN as a direct target of WT1 in A498 cells, in which positive regulation was shown by RT-qPCR. It has been shown that the transcription factor JUN can regulate IL-24 expression, and therefore, we hypothesize that WT1 might regulate the IL-24 through JUN. Furthermore, analysis based on TCGA datasets showed that the expression of WT1-regulated genes, including TXNIP and GADD45A, was significantly correlated with the stage and histological grade of tumors, with high levels linked to favorable prognoses. Our results demonstrated that the overexpression of WT1 upregulates IL-24, leading to G2/M checkpoint arrest to reduce proliferation. These results indicate that regulation of IL-24 by WT1 inhibits proliferation and may represent a potential target for treating renal carcinoma.

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.

TCDD-induced IL-24 secretion in human chorionic stromal cells inhibits placental trophoblast cell migration and invasion

Environmental pollutant dioxins are potentially harmful to pregnant women and can lead to severe adverse outcomes in pregnancy, such as spontaneous abortion and stillbirth. However, little is currently known about the underlying toxicological mechanism. Our previous study reported that the IL-24 gene is a dioxin response gene during 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) treatment. Here, we further tested the effect of TCDD on IL-24 expression in human chorionic stromal cells. We also investigated the effect of IL-24 on the behaviors of human placental trophoblast cells and predicted the potential mechanism underlying these behaviors using functional network analysis. We found that TCDD stimulates IL-24 expression in human chorionic stromal cells in an AhR (aromatic hydrocarbon receptor)-related manner. We also found that IL-24 inhibits the migration and invasion of human placental trophoblast cells, the possible mechanism of which involves thirteen key proteins and mitochondrial function. Our findings suggest that IL-24 is a potential factor induced by TCDD to regulate trophoblast cell invasion, which potentially involves in TCDD-induced abortion.

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.

Novel fusion protein NGR-sIL-24 for targetedly suppressing cancer cell growth via apoptosis

Pro-apoptotic peptides have attracted much attention as promising anticancer agents due to their high activity. However, poor cellular uptake of the peptides is often associated with limited therapeutic application. Cell-penetrating homing peptides (CPHPs) were found to increase cell internalization as well as anticancer efficacy of the peptide conjugates. In this study, we developed a novel recombinant fusion protein composed of sIL-24 peptide as a pro-apoptotic moiety and asparagine-glycine-arginine (NGR) motif as a CD13-targeting CPHP component. In silico analysis demonstrated that flexible GGGGS linker provided the best structure and stability for our designed fusion protein. Cell adhesion experiments showed a significant binding affinity toward high CD13-expressing cells (U937 and A549) for NGR-sIL-24. Moreover, confocal microscopy revealed that NGR strongly facilitated the binding and cellular uptake of sIL-24 in U937 and A549 cancer cells. NGR-sIL-24 treatment markedly inhibited the growth of U937 and A549 cancer cells in a dose and time-dependent manner, without affecting the normal cell line MRC-5. Flow cytometric analysis and Hoechst 33342 staining exhibited potent apoptosis induction in U937 and A549 cells treated with NGR-sIL-24. Further mechanism elucidation uncovered that apoptotic death promoted by NGR-sIL-24 was attributed to upregulation of BiP/GRP78, Bax/Bcl-2, GADD34, cytochrome c release, and cleavage of caspase-3, suggesting NGR-sIL-24 penetration into cancerous cells and subsequent apoptosis induction, mainly through endoplasmic reticulum (ER) stress-dependent and mitochondria-dependent signaling pathways. Our results indicate that the designed recombinant fusion protein NGR-sIL-24 may serve as a potential targeted therapy agent for cancers with high expression of CD13.

The clinical significance of Mda-7/IL-24 and C-myb expression in tumor tissues of patients with diffuse large B cell lymphoma

Diffuse large B cell lymphoma (DLBCL) is the most common type of non-Hodgkin's lymphoma in adults. Mda-7/IL-24 had been identified as a differentiation inducer of B phenotype lymphoma cells. Previous studies have revealed that knockdown of C-myb also leads to the terminal differentiation of B cell lymphoma. The aim of the present study was to investigate the association between the expression of Mda-7/IL-24 and C-myb, and their prognostic significance for DLBCL patients. The tumor tissues were collected from 72 cases of DLBCL patients and detected with reverse transcription-quantitative polymerase chain reaction, western blotting and immunohistochemistry assays. The results showed that, the expression of Mda-7/IL-24 mRNA and protein was lower while the expression of C-myb was higher in DLBCL tissues, compared with the specimens of normal lymph node tissues. Furthermore, C-myb expression was negatively correlated with Mda-7/IL-24 expression at mRNA and protein levels in DLBCL tissues. The expression of Mda-7/IL-24 and C-myb in DLBCL tissues was associated with some clinicopathological parameters such as clinical stage, infiltration in bone marrow, Ki67 expression level in the tumor tissues and overall survival rates. These results indicated that low expression of Mda-7/IL-24, along with high expression of C-myb, are predictor for poor prognosis of DLBCL patients, suggesting that Mda-7/IL-24 and C-myb may be potential targets for clinical treatment of DLBCL.

Enhanced tumor growth inhibition by mesenchymal stem cells derived from iPSCs with targeted integration of interleukin24 into rDNA loci

Induced pluripotent stem cells (iPSCs) are a promising source of mesenchymal stem cells (MSCs) for clinical applications. In this study, we transformed human iPSCs using a non-viral vector carrying the IL24 transgene pHrn-IL24. PCR and southern blotting confirmed IL24 integration into the rDNA loci in four of 68 iPSC clones. We then differentiated a high expressing IL24-iPSC clone into MSCs (IL24-iMSCs) that showed higher expression of IL24 in culture supernatants and in cell lysates than control iMSCs. IL24-iMSCs efficiently differentiated into osteoblasts, chondrocytes and adipocytes. Functionally, IL24-iMSCs induced in vitro apoptosis in B16-F10 melanoma cells more efficiently than control iMSCs when co-cultured in Transwell assays. In vivo tumor xenograft studies in mice demonstrated that IL24-iMSCs inhibited melanoma growth more than control iMSCs did. Immunofluorescence and histochemical analysis showed larger necrotic areas and cell nuclear aggregation in tumors with IL24-iMSCs than control iMSCs, indicating that IL24-iMSCs inhibited tumor growth by inducing apoptosis. These findings demonstrate efficient transformation of iPSCs through gene targeting with non-viral vectors into a rDNA locus. The ability of these genetically modified MSCs to inhibit in vivo melanoma growth is suggestive of the clinical potential of autologous cell therapy in 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.

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.

Lentivirus‑mediated MDA7/IL24 expression inhibits the proliferation of hepatocellular carcinoma cells

MDA7/IL24 is a member of the IL-10 gene family that functions as a cytokine. Notably, supra-physiological endogenous MDA7 levels have been indicated to suppress tumor growth and induce apoptosis in different cancer types. In the present study, MDA7 roles were investigated during the proliferation of hepatocellular carcinoma (HCC) cells and the molecular mechanisms underlying this process. A lentiviral vector expressing MDA7/IL24 (LV-MDA7/IL24) was constructed and used to infect HCC SMMC-7721 cells. The expression levels of MDA7/IL24 in these cells were determined using RT-qPCR and western blot analysis. The effects of LV-MDA7/IL24 on cell proliferation were analyzed using MTT and colony formation assays. Furthermore, the influence of LV-MDA7/IL24 on cell apoptosis and cell cycle distribution were detected using flow cytometry. The underlying molecular mechanisms were investigated using microarray and western blot analysis. The expression of MDA7/IL24 was confirmed to be significantly increased in the cells infected with LV-MDA7/IL24 compared with that the negative-control infected group. Lentivirus-mediated MDA7/IL24 expression was found to inhibit HCC cell proliferation and colony formation, and it also induced cell arrest and apoptosis. Microarray analysis and western blotting results indicated that multiple cancer-associated pathways and oncogenes are regulated by MDA7/IL24, including cell cycle regulatory and apoptosis activation pathway. In conclusion, it was determined that MDA7/IL24 inhibits the proliferation and reduces the tumorigenicity of HCC cells by regulating cell cycle progression and inducing apoptosis, indicating that it may be used as a potential prognostic and therapeutic target in HCC.

Low expression of Mda-7/IL-24 and high expression of C-myb in tumour tissues are predictors of poor prognosis for Burkitt lymphoma patients

Objectives Burkitt lymphoma is one of the most common types of haematopoietic malignancy in children and adolescents. Mda-7/IL-24 had been identified as a differentiation inducer of Burkitt lymphoma cells. Previous studies have revealed that knockdown of C-myb can also lead to the terminal differentiation of Burkitt lymphoma cells. The aim of the present study was to investigate the correlation between the expression of Mda-7/IL-24 and C-myb, as well as their prognostic significance, for Burkitt lymphoma patients. Methods The tumour tissues were collected from 59 cases of Burkitt lymphoma patients and detected with Western blotting and immunohistochemistry. Results The results showed that the expression of Mda-7/IL-24 was lower, whereas the expression of C-myb was higher in Burkitt lymphoma tissues compared to specimens of normal lymph node tissues. Furthermore, C-myb expression was negatively correlated with Mda-7/IL-24 expression at the protein level in Burkitt lymphoma tissues and cell lines. Both the expression of Mda-7/IL-24 and C-myb in Burkitt lymphoma tissues was associated with some clinicopathological parameters, such as clinical stage, infiltration in the bone marrow, Ki67 and overall survival rates. Conclusion These results indicated that low expression of Mda-7/IL-24 along with high expression of C-myb are predictors for poor prognosis of Burkitt lymphoma patients; this outcome suggests that Mda-7/IL-24 and C-myb might be potential targets for clinical treatment of Burkitt lymphoma.

ABBREVIATIONS

Mda-7/IL-24: melanoma differentiation associated gene7/interleukin 24; FCM: flow cytometry; Ecog: Eastern Cooperative Oncology Group; IPI: International lymphoma prognosis index.

Macrophages promote the growth and invasion of endometrial stromal cells by downregulating IL-24 in endometriosis

Macrophages play an important role in the origin and development of endometriosis. Estrogen promoted the growth of decidual stromal cells (DSCs) by downregulating the level of interleukin (IL)-24. The aim of this study was to clarify the role and mechanism of IL-24 and its receptors in the regulation of biological functions of endometrial stromal cells (ESCs) during endometriosis. The level of IL-24 and its receptors in endometrium was measured by immunohistochemistry.In vitroanalysis was used to measure the level of IL-24 and receptors and the biological behaviors of ESCs. Here, we found that the expression of IL-24 and its receptors (IL-20R1 and IL-20R2) in control endometrium was significantly higher than that in eutopic and ectopic endometrium of women with endometriosis. Recombinant human IL-24 (rhIL-24) significantly inhibited the viability of ESCs in a dosage-dependent manner. Conversely, blocking IL-24 with anti-IL-24 neutralizing antibody promoted ESCs viability. In addition, rhIL-24 could downregulate the invasiveness of ESCsin vitro. After co-culture, macrophages markedly reduced the expression of IL-24 and IL-20R1 in ESCs, but not IL-22R1. Moreover, macrophages significantly restricted the inhibitory effect of IL-24 on the viability, invasion, the proliferation relative gene Ki-67, proliferating cell nuclear antigen (PCNA) and cyclooxygenase2 (COX-2), and the stimulatory effect on the tumor metastasis suppressor gene CD82 in ESCs. These results indicate that the abnormally low level of IL-24 in ESCs possibly induced by macrophages may lead to the enhancement of ESCs’ proliferation and invasiveness and contribute to the development of endometriosis.

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

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

Notch1 downregulation combined with interleukin-24 inhibits invasion and migration of hepatocellular carcinoma cells

AIM: To confirm the anti-invasion and anti-migration effects of down-regulation of Notch1 combined with interleukin (IL)-24 in hepatocellular carcinoma (HCC) cells.

METHODS: γ-secretase inhibitors (GSIs) were used to down-regulate Notch1. HepG2 and SMMC7721 cells were seeded in 96-well plates and treated with GSI-I or/and IL-24 for 48 h. Cell viability was measured by MTT assay. The cellular and nuclear morphology was observed under a fluorescence microscope. To further verify the apoptotic phenotype, cell cultures were also analyzed by flow cytometry with Annexin V-FITC/propidium iodide staining. The expression of Notch1, SNAIL1, SNAIL2, E-cadherin, IL-24, XIAP and VEGF was detected by Western blot. The invasion and migration capacities of HCC cells were detected by wound healing assays. Notch1 and Snail were down-regulated by RNA interference, and the target proteins were analyzed by Western blot. To investigate the mechanism of apoptosis, we analyzed HepG2 cells treated with siNotch1 or siCON plus IL-24 or not for 48 h by caspase-3/7 activity luminescent assay.

RESULTS: GSI-I at a dose of 2.5 μmol/L for 24 h caused a reduction in cell viability of about 38% in HepG2 cells. The addition of 50 ng/mL IL-24 in combination with 1 or 2.5 μmol/L GSI-I reduced cell viability of about 30% and 15%, respectively. Treatment with IL-24 alone did not induce any cytotoxic effect. In SMMC7721 cells with the addition of IL-24 to GSI-I (2.5 μmol/L), the reduction of cell viability was only about 25%. Following GSI-I/IL-24 combined treatment for 6 h, the apoptotic rate of HepG2 cells was 47.2%, while no significant effect was observed in cells treated with the compounds employed separately. Decreased expression of Notch1 and its associated proteins SNAIL1 and SNAIL2 was detected in HepG2 cells. Increased E-cadherin protein expression was noted in the presence of IL-24 and GSI-I. Furthermore, the increased GSI-I and IL-24 in HepG2 cell was associated with downregulation of MMP-2, XIAP and VEGF. In the absence of treatment, HepG2 cells could migrate into the scratched space in 24 h. With IL-24 or GSI-I treatment, the wound was still open after 24 h. And the distance of the wound closure strongly correlated with the concentrations of IL-24 and GSI-I. Treatment of Notch-1 silenced HepG2 cells with 50 ng/mL IL-24 alone for 48 h induced cytotoxic effects very similar to those observed in non-silenced cells treated with GSI-I/IL-24 combination. Caspase-3/7 activity was increased in the presence of siNotch1 plus IL-24 treatment.

CONCLUSION: Down-regulation of Notch1 by GSI-I or siRNA combined with IL-24 can sensitize apoptosis and decrease the invasion and migration capabilities of HepG2 cells.

Advances in research of tumor microenvironment in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is not just composed of liver cancer cells; it contains several cell types and extracellular matrix that interact with each other, creating a complex interaction network within a permissive microenvironment. The tumor microenvironment in HCC can not only support liver cancer cell growth but also promote tumor invasion through the stimulation of cancer cell proliferation, migration, and invasion and activation of angiogenesis, which together determine the phenotype of HCC. In this review, we provide an overview of current knowledge on the role of the tumor microenvironment in HCC and its application in prognosis prediction and treatment.

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.