Radiosensitization of breast cancer cells by TRAIL-endostatin-targeting gene therapy

Co-overexpression of TRAIL and Smac sensitizes MDA-MB-231 cells to radiation through apoptosis depending on mitochondrial pathway

Pro-apoptosis in cancer cells has been proposed as a beneficial therapeutic strategy for potentiating the anticancer effects of radiotherapy. TNF-related apoptosis inducing ligand (TRAIL) and Second mitochondria derived activator of caspase (Smac) can induce cell apoptosis. Herein, we designed a conditionally replicating adenoviral co-overexpression vector of TRAIL and Smac regulated by the Egr1 promoter, in which hTERT, E1A-E1B and E1B55K genes were inserted to achieve enhanced tumor targeting characteristics. After breast cancer MDA-MB-231 cells were infected and irradiated, cellular proliferation and colony formation were measured, apoptotic rate was detected by FCM after AnnexinV-FITC/PI staining. To explore the molecular mechanisms of apoptosis, mRNA and protein levels of TRAIL, Smac, Cytochrome c (Cyt c), death receptor 5 (DR5), caspase-8, -9 and -3 were measured by quantitative real-time PCR, ELISA and Western blot, and caspase-3 activity was detected using caspase-3 activity kits. The results showed that TRAIL and/or Smac overexpression enhanced proliferation inhibition and radio-sensitivity through apoptosis. In addition, the combination of IR and overexpression of TRAIL and/or Smac can activate more apoptosis in tumor cells, and the transcriptional levels and protein expressions of Cyt c, DR5, caspase-8, -9 and -3 had similar regularity with apoptotic changes, indicating the molecular mechanisms of TRAIL and Smac involves the mitochondrial pathway. Our findings may have implications for novel radiotherapy plans for breast tumor treatment.

Synergistic Suppression Effect on Tumor Growth of Colorectal Cancer by Combining Radiotherapy With a TRAIL-Armed Oncolytic Adenovirus

The combination of gene therapy and radiation is a promising new treatment for cancer. This study aimed to clarify the synergistic effect of targeted oncolytic adenovirus (radiotherapy-tumor necrosis factor-related apoptosis-inducing ligand) and radiotherapy on colorectal cancer cells and elucidate the mechanisms of the underlying antitumor activity. Viability, cell cycle status, and apoptosis of treated colorectal cancer cells were determined via MTT and flow cytometric assays. The molecular mechanism underlying apoptotic pathway activation was elucidated through Western blot analysis of caspase-8, caspase-3, and PARP proteins. Combination treatment with radiotherapy-tumor necrosis factor-related apoptosis-inducing ligand and radiotherapy displayed significantly greater antitumor activity than either of the monotherapies. The primary mechanism behind the antitumor activity in the SW480 and Lovo colorectal cancer cell lines was apoptosis induction through the caspase pathway and G1 phase arrest. In an SW480 xenograft model of colorectal cancer, the combination therapy achieved a significantly greater reduction in tumor volume than the monotherapies. Overall, in this study, we demonstrate that the oncolytic radiotherapy-tumor necrosis factor-related apoptosis-inducing ligand construct can sensitize human colorectal cancer cells to radiation-induced apoptosis both in vitro and in vivo. Therefore, our findings point toward a novel synergistic approach to colorectal cancer treatment.

TRAIL overexpression co-regulated by Egr1 and HRE enhances radiosensitivity of hypoxic A549 cells depending on its apoptosis inducing role

Ionizing radiation can upregulate the expression levels of TRAIL and enhance tumor cell apoptosis. While Early growth response 1 (Egr1) gene promoter has radiation inducible characteristics, the expression for exogenous gene controlled by Egr1 promoter could be enhanced by ionizing radiation, but its efficiency is limited by tissue hypoxia. Hypoxia response elements (HREs) are important hypoxic response regulatory sequences and sensitivity enhancers. Therefore, we chose TRAIL as the gene radiotherapy to observe whether it is regulated by Egr1 and HER and its effects on A549 cells and its mechanism. The pcDNA3.1-Egr1-TRAIL (pc-E-hsT) and pcDNA3.1-HRE/Egr1-TRAIL (pc-H/E-hsT) plasmids containing Egr1-hsTRAIL and HRE/Egr1-hsTRAIL were transfected into A549 cells, the cells were treated by hypoxia and radiation. The TRAIL mRNA in the cells and protein concentration in the culture supernatants were measured by RT-PCR and ELISA, respectively. Mean lethal dose D0 value was evaluated with colony forming assay. The cell apoptotic rates were analyzed by FCM and TUNEL assay. Expression of DR4, DR5 and cleaved caspase-3 proteins were analyzed by western blotting. It showed that TRAIL mRNA expression and TRAIL concentration all significantly increased under hypoxia and/or radiation. D0 value of pc-H/E‑hsT transfected cells under hypoxia was lowest, indicating more high radiosensitivity. Hypoxia could not cause the pc-E-hsT transfected cell apoptotic rate increase, but there were promoting effects in pc-H/E-hsT transfected cells. DR4 had not obvious change in pc-E-hsT and pc-H/E-hsT transfected cells under normoxic and hypoxic condition, otherwise, DR5 and cleaved caspase-3 increased mostly in pc-H/E-hsT transfected cells under hypoxic condition. TRAIL overexpression was co-regulated by Egr1 and HRE. TRAIL might promote hypoxic A549 cell radiosensitivity and induce apoptosis depending on DR5 to caspase-3 pathways.

Inhibiting effect of Endostar combined with ginsenoside Rg3 on breast cancer tumor growth in tumor-bearing mice

OBJECTIVE

To study the inhibiting effect of Endostar combined with ginsenoside Rg3 on breast cancer tumor growth in tumor-bearing mice.

METHODS

Female mice were selected as experimental animals, and breast cancer tumor-bearing mouse models were established and then divided into groups A, B, C and D that respectively received saline, recombinant human endostatin, ginsenosides Rg3 and recombinant human endostatin combined with Rg3 intervention; 7 d, 14 d and 21 d after intervention, tumor tissue volume was measured; 21 d after intervention, mice were killed, tumor tissue was collected, and mRNA contents of angiogenesis molecules, invasion molecules, autophagy marker molecules and autophagy signaling pathway molecules were detected.

RESULTS

At 7 d, 14 d and 21 d after intervention, tumor tissue volume of groups B, C and D was lower than that of group A, and tumor tissue volume of group D was lower than that of groups B and C; mRNA contents of VEGFA, VEGFB, VEGFC, MMP2, MMP9, p62, mTOR, PI3K, Akt, JNK and Beclin-1 in tumor tissue of groups B, C and D were significantly lower than those of group A, and LC3-II/LC3-I was significantly higher than that of group A; mRNA contents of VEGFA, VEGFB, VEGFC, MMP2, MMP9, p62, mTOR, PI3K, Akt, JNK and Beclin-1 in tumor tissue of group D were significantly lower than those of groups B and C, and LC3-II/LC3-I was higher than that of groups B and C.

CONCLUSIONS

Endostar combined with ginsenoside Rg3 has stronger inhibiting effect on breast cancer tumor growth in tumor-bearing mice than single drug, and it can inhibit angiogenesis and cell invasion, and enhance cell autophagy.

EGR-1/Bax pathway plays a role in vitamin E δ-tocotrienol-induced apoptosis in pancreatic cancer cells

The anticancer activity of δ-tocotrienol, a bioactive vitamin E present in whole grain cereals, annatto beans and palm fruit, is strongly dependent on its effect on the induction of apoptosis. δ-Tocotrienol-induced apoptosis is associated with consistent induction in the expression of the proapoptotic protein Bcl-2-associated X protein (Bax). The molecular mechanism by which δ-tocotrienol regulates Bax expression is unknown. We carried out a DNA microarray study that identified δ-tocotrienol induction of the zinc finger transcription factor EGR-1 in pancreatic cancer cells. Here, we provide evidence linking δ-tocotrienol-induced apoptosis in pancreatic cancer cells to EGR-1 regulation of Bax expression. Forced expression of EGR-1 induces Bax expression and apoptosis in pancreatic cancer cells. In contrast, knockdown of δ-tocotrienol-induced EGR-1 by small interfering RNA attenuated δ-tocotrienol-induced Bax expression and reduced δ-tocotrienol-induced apoptosis. Further analyses showed that de novo protein synthesis was not required for δ-tocotrienol-induced EGR-1 expression, suggesting a direct effect of δ-tocotrienol on EGR-1 expression. Furthermore, a chromatin immunoprecipitation assay demonstrated that EGR-1 binds to the Bax gene promoter. Finally, δ-tocotrienol treatment induced Bax expression and activated EGR-1 in the pancreatic neoplastic cells of the PDX-Cre Kras genetically engineered model of pancreatic cancer. Our study provides the first evidence for EGR-1 as a direct target of vitamin E δ-tocotrienol, suggesting that EGR-1 may act as a proapoptotic factor in pancreatic cancer cells via induction of Bax.

Expression of Smac induced by the Egr1 promoter enhances the radiosensitivity of breast cancer cells

Breast cancer is one of the most prevalent cancers worldwide. Moreover, despite advances in antineoplastic therapies, induction of tumor cell death without off-target cytotoxicity remains a challenge. However, recent developments in localized radiotherapy and gene therapy have provided an opportunity to explore the potential for these strategies to be additive for the induction of cell death in tumor cells. Here, a novel adenoviral shuttle vector containing the proapoptotic gene Smac under the control of the ionizing radiation (IR)-induced Egr1 promoter was constructed. Following the transient transfection of the construct into MCF-7 and MDA-MB-435 breast cancer cell lines, acute and abundant expression of Smac was observed in response to IR treatment. Further analysis confirmed that the induction of Smac expression resulted in a decrease in cell viability, a slower rate of cell growth, a higher level of apoptosis and altered cell cycle progression. Using a clonogenic assay, IR-induced Smac expression was also found to significantly sensitize Smac-expressing cells to radiation-induced cell death. Taken together, these data suggest that Smac expression driven by the Egr1 promoter has the potential to serve as a radiotherapy-dependent gene therapy agent.

Repair of radiation damage of U2OS osteosarcoma cells is related to DNA-dependent protein kinase catalytic subunit (DNA-PKcs) activity

The present study was to investigate the effects of DNA-PKcs deficiencies on radiation sensitivity of human osteosarcoma U2OS cells to γ-ray and to explore the underlying molecular mechanism. In vitro, U2OS cells were transfected with different DNA-PKcs siRNAs or control siRNAs to establish stably siRNA-transfected cell lines U2OS-Si and U2OS-Sc, respectively. Cell viability and apoptosis after irradiation were analyzed using cell counting kit (CCK-8) and flow cytometric assay, respectively. Expressions of apoptosis-related and oxidative stress-responded proteins were assessed using Western blot. The tumorigenesis activity was examined in nude mice xenograft osteosarcoma mode. Results showed that DNA-PKcs siRNA significantly could inhibit U2OS viability and cell proliferation after exposure to irradiation. Compared with the U2OS and U2OS-Sc cells, the U2OS-Si cells induced higher apoptosis rate and loss of mitochondrial membrane potentials, accompanying with more reactive oxygen species (ROS) and malondialdehyde (MDA) production, increased DNA double-strand breaks (DSBs) induced by irradiation. Protein levels of the anti-apoptotic Bcl-2 were downregulated most obviously in U2OS-Si cells after irradiation, while pro-apoptotic factor Bax and caspase-3 upregulated. Moreover, the antioxidants protein expression levels of Nuclear factor-erythroid 2-related factor 2 (Nrf2) and its target heme oxygenase-1 (HO-1) were also significantly reduced in parallel to DNA-PKcs inhibition in U2OS-Si cells. In nude mice xenograft model, DNA-PKcs siRNA remarkably inhibited tumor growth and dissemination. In conclusion, DNA-PKcs siRNA might have a potential for osteosarcoma treatment by sensitizing osteosarcoma cells to γ-ray through modulation on oxidative stress-mediated DNA DSBs repair and mitochondrial pathway apoptosis.