E1ASpecifically Enhances Sensitivity to Topoisomerase IIα Targeting Anticancer Drug by Up-Regulating the Promoter Activity

Ewing sarcoma treatment: a gene therapy approach

Ewing sarcoma (ES) is an aggressive malignant tumor, characterized by non-random chromosomal translocations that produce fusion genes. Fusion genes and fusion protein products are promising targets for gene therapy. Therapeutic approaches and strategies vary based on target molecules (nucleotides, proteins) of interest. We present an extensive literature review of active molecules for gene therapy and methods of gene therapy delivery, both of which are necessary for successful treatment.

Polyethylenimine (PEI)-Mediated E1A Increases the Sensitivity of Hepatocellular Carcinoma Cells to Chemotherapy

BACKGROUND The aim of this study was to assess the ability of polyethylenimine (PEI) as an E1A plasmid vector to transfect hepatocellular carcinoma SMMC-7721 cells and to analyze the sensitization effect of E1A on various anti-tumor drugs. MATERIAL AND METHODS PEI-mediated recombinant plasmid psv-E1A with high expression of the E1A gene was introduced into hepatocellular carcinoma SMMC-7721 cells, and the effective transfection of E1A gene was determined by RT-PCR and Western blot analysis. The CCK8 method was used to detect the proliferation inhibition of docetaxel, epirubicin, gemcitabine, and 5-fluorouracil on SMMC-7721 cells before and after the transfection of the E1A gene. RESULTS RT-PCR and Western blot analysis showed that PEI could transfect plasmid psv-E1A with stable expression. After the transfection of E1A gene, the sensitivity of SMMC-7721 cells to docetaxel, epirubicin, gemcitabine, and 5-fluorouracil was increased (P<0.05), and the sensitivity to docetaxel was significantly improved (P<0.01). CONCLUSIONS PEI can transfect plasmid psv-E1A. The E1A gene can increase the sensitivity of hepatocellular carcinoma cells to chemotherapeutic drugs. The mechanism may be related to the increased ability of the E1A gene to inhibit proliferation of hepatocellular carcinoma cells and altering the cell cycle of hepatocellular carcinoma cells.

The anti-tumor activity of E1A and its implications in cancer therapy

The adenovirus type 5 E1A protein (E1A) plays a critical role in anti-cancer gene therapy and has been tested in clinical trials. The expression of E1A significantly reduces tumorigenesis, promotes cell death, and inhibits cancer cell mobility. Chemosensitization is one of the anti-tumor effects of E1A, increasing in vitro and in vivo sensitization of anti-cancer drugs, including cisplatin, gemcitabine, etoposide, doxorubicin, paclitaxel, and tumor necrosis factor-related apoptosis-inducing ligand and histone deacetylase inhibitors in different types of cancer cells. E1A also demonstrates anti-metastasis activity through various molecular mechanisms such as the repression of protease expression, suppression of HER2/neu and downregulation of microRNA (miR-520h). Moreover, E1A has been reported to reprogram transcription in tumor cells and stabilize tumor suppressors such as PP2A/C, p21 and p53. Because E1A plays a potentially significant role in anti-tumor therapy, there exists an urgent need to study the anti-cancer activities of E1A. This paper presents a review of our current understanding of the tumor-suppressive functions and molecular regulation of E1A, as well as the potential clinical applications of E1A.

Efficacy of oncolytic mutants targeting pRb and p53 pathways is synergistically enhanced when combined with cytotoxic drugs in prostate cancer cells and tumor xenografts

Replication-selective oncolytic adenoviruses have proven safety records with promising clinical outcomes. However, strategies to improve efficacy are still required. Here we report greatly improved antitumor efficacy for both attenuated (dl1520) and highly potent (dl922–947) oncolytic mutants in combination with the current standard of care for late-stage hormone-independent prostate cancers, mitoxantrone or docetaxel. In agreement with previous reports, dl922–947 had superior potency compared with dl1520 both as a single agent and in combination with cytotoxic drugs. The dl922–947 mutant caused significant synergistic cell killing in both drug-insensitive and -sensitive prostate cancer cell lines, PC3 and DU145, respectively, when combined with docetaxel or mitoxantrone. The magnitude of the synergistic response was greatest for dl1520 whereas overall efficacy was greatest for dl922–947, and the latter was also more efficacious in vivo in prostate cancer models. In DU145 and PC3 cells increased viral uptake (up to 9- and 8-fold, respectively), E1A expression, and altered cell cycle progression contributed to the synergistic cell killing. A similar trend was also detected in LNCaP cells. Potent E1A expression was essential for the response. In murine xenograft models (DU145 and PC3) tumor growth inhibition was improved when suboptimal doses of docetaxel and viral mutants were combined. These findings demonstrate that the efficacy of highly potent oncolytic mutants such as dl922–947 that target the retinoblastoma protein (pRb) pathway could be further enhanced even with low drug doses, and support the deletion of the E1ACR2 region in future candidate adenoviruses for treatment of hormone-independent prostate cancers.

Interleukin-12 Up-Regulates Fas Expression in Human Osteosarcoma and Ewing's Sarcoma Cells by Enhancing Its Promoter Activity

Interleukin-12 (IL-12) has shown significant antitumor activity in several preclinical animal tumor models. Our previous studies showed that IL-12 inhibited tumor growth in human osteosarcoma and Ewing's sarcoma animal model. Decreased Fas expression in osteosarcoma increased the lung metastatic potential. In this study, we further examined the mechanism of IL-12 antitumor activity and showed that IL-12 significantly increased Fas expression in both human osteosarcoma cells LM7 and Ewing's sarcoma cells TC71. Up-regulation of Fas expression increased their sensitivity to Fas-induced cell apoptosis. Constructs of the Fas promoter linked to a luciferase reporter gene were used to determine the promoter activity. IL-12 increased Fas promoter activity 4.2- and 4.9-fold in TC71 and LM7 cells, respectively. Time course studies have shown that recombinant IL-12 stimulated Fas promoter activity at 2 hours, reached the peak level at 4 hours, and then declined at 24 hours. To investigate whether IL-12 specifically enhanced Fas promoter activity, we determined whether another gene (E1A) was able to stimulate Fas promoter activity. We also evaluated effect of IL-12 on the topoisomerase IIalpha promoter. The results indicated that E1A but not IL-12 stimulated topoisomerase IIalpha promoter activity. E1A failed to increase Fas promoter activity. We also found that kappaB-Sp1 element at position -295 to -286 in Fas promoter was essential for IL-12-induced activation, and nuclear factor-kappaB transcription factor was activated after IL-12 treatment in TC71 cells. These results indicate that IL-12 up-regulates Fas expression in human osteosarcoma and Ewing's sarcoma by enhancing Fas promoter activity. Understanding this mechanism may lead to new therapeutic approaches for the treatment of sarcoma involving the use of IL-12.