A SIRPα-Fc fusion protein enhances the antitumor effect of oncolytic adenovirus against ovarian cancer.

Oncolytic viruses armed with therapeutic transgenes of interest show great potential in cancer immunotherapy. Here, a novel oncolytic adenovirus carrying a signal regulatory protein-α (SIRPα)-IgG1 Fc fusion gene (termed SG635-SF) was constructed, which could block the CD47 'don't eat me' signal of cancer cells. A strong promoter sequence (CCAU) was chosen to control the expression of the SF fusion protein, and a 5/35 chimeric fiber was utilized to enhance the efficiency of infection. As a result, SG635-SF was found to specifically proliferate in hTERT-positive cancer cells and largely increased the abundance of the SF gene. The SF fusion protein was effectively detected, and CD47 was successfully blocked in SK-OV3 and HO8910 ovarian cancer cells expressing high levels of CD47. Although the ability to induce cell cycle arrest and cell death was comparable to that of the control empty SG635 oncolytic adenovirus in vitro, the antitumor effect of SG635-SF was significantly superior to that of SG635 in vivo. Furthermore, CD47 was largely blocked and macrophage infiltration distinctly increased in xenograft tissues of SK-OV3 cells but not in those of CD47-negative HepG2 cells, indicating that the enhanced antitumor effect of SG635-SF was CD47-dependent. Collectively, these findings highlight a potent antitumor effect of SG635-SF in the treatment of CD47-positive cancers.

Mesothelin-targeting chimeric antigen receptor-modified T cells by piggyBac transposon system suppress the growth of bile duct carcinoma.

Chimeric antigen receptor modified T cell-based immunotherapy is revolutionizing the field of cancer treatment. However, its potential in treating bile duct carcinoma has not been fully explored. Herein, we developed the second-generation mesothelin-targeting chimeric antigen receptor-modified T cells with the 4-1BB co-stimulatory module by the piggyBac transposon system. Mesothelin-targeting chimeric antigen receptor was expressed by 66.0% of mesothelin-targeting chimeric antigen receptor-modified T cells post electrophoretic transfection and stimulation with K562-meso cells; the expressions of activation markers were tested by flow cytometry assay and showed greater activation of mesothelin-targeting chimeric antigen receptor-modified T cells than control T cells (CD107α: 71.9% vs 48.6%; CD27: 92.1% vs 61.8%; CD137: 55.5% vs 8.4%; CD28: 98.0% vs 82.1%; CD134: 37.5% vs 10.4%). Furthermore, mesothelin-targeting chimeric antigen receptor-modified T cells exerted cytotoxicity toward mesothelin-expressing EH-CA1b and EH-CA1a cells in an effector-to-target ratio-dependent manner, while leaving mesothelin-negative GSC-SD and EH-GB1 cells and normal liver L02 cells almost unharmed. Mesothelin-targeting chimeric antigen receptor-modified T cells secreted cytokines at higher levels when co-cultured with mesothelin-positive EH-CA1a and EH-CA1b cells than with mesothelin-negative GSC-SD and EH-GB1 cells. Enhanced cytotoxicity and cytokine secretion of mesothelin-targeting chimeric antigen receptor-modified T cells compared to control T cells were also observed when co-cultured with 293-meso cells (interferon γ: 85.1% ± 1.47% vs 8.3% ± 2.50%, p = 0.000; tumor necrosis factor α: 90.9% ± 4.67% vs 18.5% ± 3.62%, p = 0.0004; interleukin 2: 60.8% ± 2.00% vs 15.6% ± 2.06%, p = 0.002; interleukin 6: 6.4% ± 2.95% vs 1.7% ± 0.63%, p = 0.055). In addition, mesothelin-targeting chimeric antigen receptor-modified T cells showed greater inhibitory and proliferative capability than control T cells within EH-CA1a cell xenografts. This study shows the potential of mesothelin-targeting chimeric antigen receptor-modified T cells in treating bile duct carcinoma.

11R-P53 and GM-CSF Expressing Oncolytic Adenovirus Target Cancer Stem Cells with Enhanced Synergistic Activity.

Targeting cancer stem cells with oncolytic virus (OV) holds great potential for thorough elimination of cancer cells. Based on our previous studies, we here established 11R-P53 and mGM-CSF carrying oncolytic adenovirus (OAV) SG655-mGMP and investigated its therapeutic effect on hepatocellular carcinoma stem cells Hep3B-C and teratoma stem cells ECCG5. Firstly, the augmenting effect of 11R in our construct was tested and confirmed by examining the expression of EGFP with Fluorescence and FCM assays after transfecting Hep3B-C and ECCG5 cells with OVA SG7605-EGFP and SG7605-11R-EGFP. Secondly, the expressions of 11R-P53 and GM-CSF in Hep3B-C and ECCG5 cells after transfection with OAV SG655-mGMP were detected by Western blot and Elisa assays, respectively. Thirdly, the enhanced growth inhibitory and augmented apoptosis inducing effects of OAV SG655-mGMP on Hep3B-C and ECCG5 cells were tested with FCM assays by comparing with the control, wild type 5 adenovirus, 11R-P53 carrying OVA in vitro. Lastly, the in vivo therapeutic effect of OAV SG655-mGMP toward ECCG5 cell-formed xenografts was studied by measuring tumor volumes post different treatments with PBS, OAV SG655-11R-P53, OAV SG655-mGM-CSF and OAV SG655-mGMP. Treatment with OAV SG655-mGMP induced significant xenograft growth inhibition, inflammation factor AIF1 expression and immune cells infiltration. Therefore, our OAV SG655-mGMP provides a novel platform to arm OVs to target cancer stem cells.

New Strategies for the Treatment of Solid Tumors with CAR-T Cells.

Recent years, we have witnessed significant progresses in both basic and clinical studies regarding novel therapeutic strategies with genetically engineered T cells. Modification with chimeric antigen receptors (CARs) endows T cells with tumor specific cytotoxicity and thus induce anti-tumor immunity against malignancies. However, targeting solid tumors is more challenging than targeting B-cell malignancies with CAR-T cells because of the histopathological structure features, specific antigens shortage and strong immunosuppressive environment of solid tumors. Meanwhile, the on-target/off-tumor toxicity caused by relative expression of target on normal tissues is another issue that should be reckoned. Optimization of the design of CAR vectors, exploration of new targets, addition of safe switches and combination with other treatments bring new vitality to the CAR-T cell based immunotherapy against solid tumors. In this review, we focus on the major obstacles limiting the application of CAR-T cell therapy toward solid tumors and summarize the measures to refine this new cancer therapeutic modality.

Argonaute 2 promotes angiogenesis via the PTEN/VEGF signaling pathway in human hepatocellular carcinoma.

AIM: Argonaute2 (AGO2) protein is the active part of RNA-induced silencing complex, cleaving the target mRNA strand complementary to their bound siRNA. An increasing number of miRNAs has been identified as essential to angiogenesis of hepatocellular carcinoma (HCC). In this study we investigated how AGO2 affected HCC angiogenesis. METHODS: Human HCC cell lines HepG2, Hep3B, Huh7, SMMC-7721, Bel-7404, MHCC97-H and LM-3, and human umbilical vein endothelial cells (HUVEC) were tested. The expression of AGO2 in HCC cells was knocked down with siRNA and restored using recombinant adenovirus expressing Ago2. The levels of relevant mRNAs and proteins were examined using RT-PCR, Western blot and EILSA. Nude mice were implanted with Huh7 or SMMC-7721 cells, and tumor volumes were measured. After the mice were euthanized, the xenograft tumors were used for immunohistological analysis. RESULTS: In 6 HCC cell lines, AGO2 protein expression was significantly correlated with VEGF expression (r=+0.79), and with VEGF secretion (r=+0.852). Knockdown of Ago2 in Huh7 cells and SMMC-7721 cells substantially decreased VEGF expression, whereas the restoration of AGO2 reversed both VEGF expression and secretion. Furthermore, knockdown of Ago2 significantly up-regulated the expression of PTEN (a tumor suppressor involved in the inhibition of HCC angiogenesis), and vice versa. Moreover, the specific PTEN inhibitor bisperoxovanadate (7, 14, 28 nmol/L) dose-dependently restored the expression of VEGF and the capacity of HCC cells to induce HUVECs to form capillary tubule structures. In the xenograft nude mice, knockdown of Ago2 markedly suppressed the tumor growth and decreased PTEN expression and CD31-positive microvascular in the xenograft tumors. CONCLUSION: A direct relationship exists between the miRNA processing machinery AGO2 and HCC angiogenesis that is mediated by the AGO2/PTEN/VEGF signaling pathway. The results suggest the high value of Ago2 knockdown in anti-angiogenesis therapy for HCC.