Endostatin-cytosine deaminase fusion protein suppresses tumor growth by targeting neovascular endothelial cells

Bi-Functional Radiotheranostics of 188Re-Liposome-Fcy-hEGF for Radio- and Chemo-Therapy of EGFR-Overexpressing Cancer Cells

Epidermal growth factor receptor (EGFR) specific therapeutics is of great importance in cancer treatment. Fcy-hEGF fusion protein, composed of yeast cytosine deaminase (Fcy) and human EGF (hEGF), is capable of binding to EGFR and enzymatically convert 5-fluorocytosine (5-FC) to 1000-fold toxic 5-fluorocuracil (5-FU), thereby inhibiting the growth of EGFR-expressing tumor cells. To develop EGFR-specific therapy, ¹⁸⁸Re-liposome-Fcy-hEGF was constructed by insertion of Fcy-hEGF fusion protein onto the surface of liposomes encapsulating of ¹⁸⁸Re. Western blotting, MALDI-TOF, column size exclusion and flow cytometry were used to confirm the conjugation and bio-activity of ¹⁸⁸Re-liposome-Fcy-hEGF. Cell lines with EGFR expression were subjected to treat with ¹⁸⁸Re-liposome-Fcy-hEGF/5-FC in the presence of 5-FC. The ¹⁸⁸Re-liposome-Fcy-hEGF/5-FC revealed a better cytotoxic effect for cancer cells than the treatment of liposome-Fcy-hEGF/5-FC or ¹⁸⁸Re-liposome-Fcy-hEGF alone. The therapeutics has radio- and chemo-toxicity simultaneously and specifically target to EGFR-expression tumor cells, thereby achieving synergistic anticancer activity.

Structural studies of the protein endostatin in fusion with BAX BH3 death domain, a hybrid that presents enhanced antitumoral activity

Endostatin (ES) is an antiangiogenic protein that exhibits antitumor activity in animal models. However, the activity observed in animals was not observed in human clinical trials. ES-BAX is a fusion protein composed of two functional domains: ES, which presents specificity and is internalized by activated endothelial cells and the proapoptotic BH3 domain of the protein BAX, a peptide inductor of cellular death when internalized. We have previously shown (Chura-Chambi et al., Cell Death Dis, 5, e1371, 2014) that ES-BAX presents improved antitumor activity in relation to wild-type ES. Secondary and tertiary structures of ES-BAX are similar to ES, as indicated by homology-modeling studies and molecular dynamics simulations. Tryptophan intrinsic fluorescence and circular dichroism spectroscopy corroborate these data. ¹⁵ N HSQC NMR indicates that ES-BAX is structured, but some ES residues have suffered chemical shift perturbations, suggesting that the BH3 peptide interacts with some parts of the ES protein. ES and ES-BAX present similar stability to thermal denaturation. The production of stable hybrid proteins can be a new approach to the development of therapeutic agents presenting specificity for tumoral endothelium and improved antitumor effect.

Targeted BikDD expression kills androgen-dependent and castration-resistant prostate cancer cells

Targeted gene therapy is a promising approach for treating prostate cancer after the discovery of prostate cancer-specific promoters such as prostate-specific antigen, rat probasin, and human glandular kallikrein. However, these promoters are androgen dependent, and after castration or androgen ablation therapy, they become much less active or sometimes inactive. Importantly, the disease will inevitably progress from androgen-dependent (ADPC) to castration-resistant prostate cancer (CRPC), at which treatments fail and high mortality ensues. Therefore, it is critical to develop a targeted gene therapy strategy that is effective in both ADPC and CRPC to eradicate recurrent prostate tumors. The human telomerase reverse transcriptase-VP16-Gal4-WPRE integrated systemic amplifier composite (T-VISA) vector we previously developed, which targets transgene expression in ovarian and breast cancer, is also active in prostate cancer. To further improve its effectiveness based on androgen response in ADPC progression, the ARR2 element (two copies of androgen response region from rat probasin promoter) was incorporated into T-VISA to produce AT-VISA. Under androgen analog (R1881) stimulation, the activity of AT-VISA was increased to a level greater than or comparable to the cytomegalovirus promoter in ADPC and CRPC cells, respectively. Importantly, AT-VISA demonstrated little or no expression in normal cells. Systemic administration of AT-VISA-BikDD encapsulated in liposomes repressed prostate tumor growth and prolonged mouse survival in orthotopic animal models as well as in the transgenic adenocarcinoma mouse prostate model, indicating that AT-VISA-BikDD has therapeutic potential to treat ADPC and CRPC safely and effectively in preclinical setting.

5-Fluorocytosine combined with Fcy-hEGF fusion protein targets EGFR-expressing cancer cells

Human epithelial cancers account for approximately 50% of all cancer deaths. This type of cancer is characterized by excessive activation and expression of the epidermal growth factor receptor (EGFR). The EGFR pathway is critical for cancer cell proliferation, survival, metastasis and angiogenesis. The EGF-EGFR signaling pathway has been validated as an important anticancer drug target. Increasing numbers of targeted therapies against this pathway have been either approved or are currently under development. Here, we adopted a prodrug system that uses 5-fluorocytosine (5-FC) and human EGF (hEGF) fused with yeast cytosine deaminase (Fcy) to target EGFR-overexpressing cancer cells and to convert 5-FC to a significantly more toxic chemotherapeutic, 5-fluorouracil (5-FU). We cloned and purified the Fcy-hEGF fusion protein from Pichia pastoris yeast. This fusion protein specifically binds to EGFR with a similar affinity as hEGF, approximately 10 nM. Fcy-hEGF binds tightly to A431 and MDA-MB-468 cells, which overexpress EGFR, but it binds with a lower affinity to MDA-MB-231 and MCF-7, which express lower levels of EGFR. Similarly, the viability of EGFR-expressing cells was suppressed by Fcy-hEGF in the presence of increasing concentrations of 5-FC, and the IC(50) values for A431 and MDA-MB-468 were approximately 10-fold lower than those of MDA-MB-231 and MCF-7. This novel prodrug system, Fcy-hEGF/5-FC, might represent a promising addition to the available class of inhibitors that specifically target EGFR-expressing cancers.

Targeted endostatin-cytosine deaminase fusion gene therapy plus 5-fluorocytosine suppresses ovarian tumor growth

There are currently no effective therapies for cancer patients with advanced ovarian cancer, therefore developing an efficient and safe strategy is urgent. To ensure cancer-specific targeting, efficient delivery, and efficacy, we developed an ovarian cancer-specific construct (Survivin-VISA-hEndoyCD) composed of the cancer specific promoter survivin in a transgene amplification vector (VISA; VP16-GAL4-WPRE integrated systemic amplifier) to express a secreted human endostatin-yeast cytosine deaminase fusion protein (hEndoyCD) for advanced ovarian cancer treatment. hEndoyCD contains an endostatin domain that has tumor-targeting ability for anti-angiogenesis and a cytosine deaminase domain that converts the prodrug 5-fluorocytosine (5-FC) into the chemotherapeutic drug, 5-fluorouracil. Survivin-VISA-hEndoyCD was found to be highly specific, selectively express secreted hEndoyCD from ovarian cancer cells, and induce cancer-cell killing in vitro and in vivo in the presence of 5-FC without affecting normal cells. In addition, Survivin-VISA-hEndoyCD plus 5-FC showed strong synergistic effects in combination with cisplatin in ovarian cancer cell lines. Intraperitoneal (i.p.) treatment with Survivin-VISA-hEndoyCD coupled with liposome attenuated tumor growth and prolonged survival in mice bearing advanced ovarian tumors. Importantly, there was virtually no severe toxicity when hEndoyCD is expressed by Survivin-VISA plus 5-FC compared with CMV plus 5-FC. Thus, the current study demonstrates an effective cancer-targeted gene therapy that is worthy of development in clinical trials for treating advanced ovarian cancer.

Mc-hES, a novel plasmid carrying human endostatin gene, inhibits nasopharyngeal carcinoma growth

Conventional plasmids for gene therapy produce low-level and short-term gene expression. Here, we first created minicircle carrying endostatin (mc-hES) for measurement of transfection efficiency. Compared with pcDNA-hES, MC-mediated endostatin gene transfer in vitro resulted in seven-fold greater endostatin expression levels in transfected cells and inhibited the growth of Human umbilical vein endothelial cells (HUVEC) more efficiently. HUVEC cell migration and tube-formation assays suggested that MC-mediated endostatin gene has significant anti-migration and anti-tube-formation capacity than that in pcDNA-hES. In vivo experiments showed that after transfection, mc-hES inhibited the growth of nasopharyngeal carcinoma xenografts. The tumor inhibition rates of mc-hES and pcDNA-hES were 60.8% and 26.9%, respectively (P<0.05). MC-mediated intratumoral endostatin expression in vivo was 2.2-17.9 times higher than pcDNA-hES in xenografted mice and lasted for 20 days. Our results suggest that minicircle DNA vectors might be a promising vector for biotherapy and should be further investigated.

Dual targeting of tumor angiogenesis and chemotherapy by endostatin-cytosine deaminase-uracil phosphoribosyltransferase

Several antiangiogenic drugs targeting VEGF/VEGF receptor (VEGFR) that were approved by the Food and Drug Administration for many cancer types, including colorectal and lung cancer, can effectively reduce tumor growth. However, targeting the VEGF signaling pathway will probably influence the normal function of endothelial cells in maintaining homeostasis and can cause unwanted adverse effects. Indeed, emerging experimental evidence suggests that VEGF-targeting therapy induced less tumor cell-specific cytotoxicity, allowing residual cells to become more resistant and eventually develop a more malignant phenotype. We report an antitumor therapeutic EndoCD fusion protein developed by linking endostatin (Endo) to cytosine deaminase and uracil phosphoribosyltransferase (CD). Specifically, Endo possesses tumor antiangiogenesis activity that targets tumor endothelial cells, followed by CD, which converts the nontoxic prodrug 5-fluorocytosine (5-FC) to the cytotoxic antitumor drug 5-fluorouracil (5-FU) in the local tumor area. Moreover, selective targeting of tumor sites allows an increasing local intratumoral concentration of 5-FU, thus providing high levels of cytotoxic activity. We showed that treatment with EndoCD plus 5-FC, compared with bevacizumab plus 5-FU treatment, significantly increased the 5-FU concentration around tumor sites and suppressed tumor growth and metastasis in human breast and colorectal orthotropic animal models. In addition, in contrast to treatment with bevacizumab/5-FU, EndoCD/5-FC did not induce cardiotoxicity leading to heart failure in mice after long-term treatment. Our results showed that, compared with currently used antiangiogenic drugs, EndoCD possesses potent anticancer activity with virtually no toxic effects and does not increase tumor invasion or metastasis. Together, these findings suggest that EndoCD/5-FC could become an alternative option for future antiangiogenesis therapy.

Human mesenchymal stem cells overexpressing pigment epithelium-derived factor inhibit hepatocellular carcinoma in nude mice

The poor outcome of cancer gene therapy in clinical trials relates in part to insufficient gene delivery to tumor sites. Mesenchymal stem cells (MSCs) represent a new tool for the delivery of therapeutic agents to tumor cells. This study used an orthotopic nude mice model of hepatocellular carcinoma (HCC) to evaluate the potential of genetically modified human MSCs (hMSCs), to function as an effective delivery vehicle for therapeutic genes. hMSCs derived from the bone marrow were efficiently engineered to express human pigment epithelium-derived factor (PEDF) by lentiviral transduction, then tested in vitro for high-level expression and bioactivity of the transgenic protein. The preferential homing of hMSCs toward HCC was confirmed by in vitro and in vivo migration assays. in vivo efficacy experiments showed that intravenous (i.v.) injection of PEDF-expressing hMSCs significantly suppressed both the growth of primary liver tumors and the development of pulmonary metastases. Moreover, hMSCs-based PEDF gene delivery moderately increased the systemic levels of human PEDF. Immunohistochemistry of primary liver tumors demonstrated lower microvessel density in mice treated with hMSCs-PEDF than in control mice. This is the first study to show the potential of hMSCs as an effective delivery vehicle for therapeutic genes in the treatment of HCC.

EPOX inhibits angiogenesis by degradation of Mcl-1 through ERK inactivation

PURPOSE

Antiangiogenic therapy is considered as an effective strategy for controlling the growth and metastasis of tumors. Among a myriad of biological activities described for xanthone derivatives, the anticancer activity is quite remarkable, but the molecular mechanism is not clearly resolved. In the present study, we investigated the antiangiogenic mechanism of 3,6-di(2,3-epoxypropoxy)xanthone (EPOX), a novel Mcl-1 targeting drug.

EXPERIMENTAL DESIGN

To evaluate the antiangiogenic activity of EPOX, we did cell viability, cell cycle, tube formation assay in vitro, and Matrigel plug assay in vivo. To evaluate the effect of EPOX on the endothelial signaling pathway, we did immunoblotting, immunoprecipitation, and immunofluorescence analysis. Intracellular glutathione levels were determined with the use of monochlorobimane, a glutathione-specific probe.

RESULTS

EPOX induced endothelial cell apoptosis in association with proteasome-dependent Mcl-1 degradation. Down-regulation of Mcl-1 resulted in an increase in Mcl-1-free Bim, activation of Bax, and then signaling of mitochondria-mediated apoptosis. Additionally, glutathione depletion and extracellular signal-regulated kinase (ERK) inactivation was observed in EPOX-treated cells. Glutathione supplementation reversed the inhibitory effects of EPOX on ERK, which increases the phosphorylation of Mcl-1 at T(163.) Overexpression of mitogen-activated protein/ERK kinase (MEK) partially reversed the effect of EPOX on Mcl-1 dephosphorylation, ubiquitination, and degradation, further implicating ERK in the regulation of Mcl-1 stability.

CONCLUSIONS

This study provides evidence that EPOX induces glutathione depletion, ERK inactivation, and Mcl-1 degradation on endothelial cells, which leads to inhibition of angiogenesis. Our results suggest that EPOX is a novel antiangiogenic agent, making it a promising lead compound for further development in the treatment of angiogenesis-related pathologies.

Construction of a survivin promoter-mediated adeno-associated virus expression vector carrying a fusion gene constituted with cytosine deaminase and survivin mutant

AIM: To construct a recombinant survivin promoter (SurP)-mediated adeno-associated virus expression vector carrying a fusion gene constituted with cytosine deaminase (CD) gene and glycin-linked survivin mutant (glySurMut), and to examine the expression of CDglySurMut fusion protein in cancer cells transfected with this vector.

METHODS: The CD gene and glySurMut fragments were amplified by polymerase chain reaction (PCR), and cloned into the adeno-associated virus expression vector PAM with survivin promoter (PAM/SurP). The recombinant vector was transformed into E.coli DH5α. and the positive clones were selected. The plasmid DNA was identified using restriction enzyme analysis and sequencing. The recombinant vector pAM/SurP-CDglySurMut was transfected into gastric cancer cells MKN45. The expression of fusion protein in cancer cells was detected using Western blot.

RESULTS: The CD gene and glySurMut were cloned from E.coli and gastric cancer cells, respectively. The restrictive enzyme analysis and sequencing showed that the fusion gene of CD and glySurMut was successfully inserted into the PAM/SurP vector. Western blot showed that the recombinant vector expressed the CDglySurMut fusion protein in gastric cancer cells.

CONCLUSION: Our results show the pAM/SurP-CDglySurMut vector can efficiently express the recombinant CDglySurMut fusion protein in gastric cancer cells, thus provides experiment evidence for targeting cancer gene therapy using this pAM/SurP-CDglySurMut vector.

IKKbeta suppression of TSC1 function links the mTOR pathway with insulin resistance

The proinflammatory cytokine TNFalpha is one of the factors that links obesity-derived chronic inflammation with insulin resistance. Activation of mTOR signaling pathway has been found to suppress insulin sensitivity through serine phosphorylation and the inhibition of IRS1 by mTOR and its downstream effector, S6K1. It remains elusive that whether the mTOR pathway has a role in TNFalpha-mediated insulin resistance. In the present study, we demonstrated that TNFalpha-IKKbeta-mediated inactivation of TSC1 resulted in increasing phosphorylation of IRS1 serine 307 and serine 636/639, impaired insulin-induced glucose uptake, tyrosine phosphorylation of IRS1, and the association between IRS1 and PI3K p85. Furthermore, a higher expression of pIKKbeta (S181), pTSC1(S511), and pS6(S240/244) was found in livers obtained from both C57BL/6J mice on a high-fat diet and B6.V-Lepob/J mice. Collectively, dysregulation of the TSC1/ TSC2/mTOR signaling pathway by IKKbeta is a common molecular switch for both cancer pathogenesis and diet- and obesity-induced insulin resistance.

Construction of FCU1 recombinant adenovirus vector and its killing effect on colon cancer cells

AIM: To construct a recombinant adenovirus vector containing fusion suicide gene FCU1, and study the cytotoxic effect of prodrug 5-FC on colon cancer cells.

METHODS: Restriction fragment of FCU1 was inserted into pDC316 vector with EcoRⅠ and SalⅠ. Recombinant plasmid pDC316-FCU1 was confirmed by restriction enzyme digestion and sequencing. Thereafter, pDC316-FCU1 was cotransfected with adenovirus backbone pBHG into 293 cells to establish the recombinant adenovirus Ad5-FCU1 by homologous recombination. The cytotoxic effect of prodrug 5-FC on the infected HCT116 cells was determined with MTT assay.

RESULTS: Recombinant plasmid pDC316-FCU1was constructed successfully. After pDC316-FCU1 together with adenovirus backbone pBHG was cotransfected into 293 cells, significant virus plaques were observed, which showed the successful homologous recombination and virus packaging in 293 cells. The titer of the purified Ad-FCU1 was 2 × 10¹² PFU/L. Nontoxic prodrug 5-FC has significant cytotoxic effect on HCT116 cells infected with pAd5-FCU1. The survival of HCT116/FCU1 cells was minimal, while that of the control cells was close to 90%, when 5-FC was used at 100 μmol/L.

CONCLUSION: Recombinant adenovirus Ad5-FCU1 containing fusion suicide gene FCU1 is established successfully, which has significant killing effect on colon cancer cells in vitro.

Targeted expression of BikDD eradicates pancreatic tumors in noninvasive imaging models

Pancreatic cancer is an aggressive malignancy with morbidity rates almost equal to mortality rates because of the current lack of effective treatment options. Here, we describe a targeted approach to treating pancreatic cancer with effective therapeutic efficacy and safety in noninvasive imaging models. We developed a versatile expression vector "VISA" (VP16-GAL4-WPRE integrated systemic amplifier) and a CCKAR (cholecystokinin type A receptor) gene-based, pancreatic-cancer-specific promoter VISA (CCKAR-VISA) composite to target transgene expression in pancreatic tumors in vivo. Targeted expression of BikDD, a potent proapoptotic gene driven by CCKAR-VISA, exhibited significant antitumor effects on pancreatic cancer and prolonged survival in multiple xenograft and syngeneic orthotopic mouse models of pancreatic tumors with virtually no toxicity.