Tissue specific expression of suicide genes delivered by nanoparticles inhibits gastric carcinoma growth

Developing an efficient and safe strategy to introduce a therapeutic gene into targeting cells in vivo is a key issue in cancer gene therapy nowadays. Novel non-viral gene carriers, such as nanoparticles, have been shown to be able to deliver DNA into cancer cells efficiently. Suicide gene therapy has been demonstrated to be effective in inhibiting tumor growth, however, the lack of tumor specificity limits its application in clinic. Developing a targeting system for suicide gene is an attractive strategy in cancer gene therapy. In this study, the CMV enhancer and carcinoembryonic antigen (CEA) promoter was fused to a chimeric suicide gene yCDglyTK. This construct was delivered into SGC7901 gastric cancer cells using calcium phosphate nanoparticles (CPNPs). The expression of yCDglyTK in SGC7901 cells was confirmed by RT-PCR and western blot. Immunofluorescence experiments showed that yCDglyTK is only expressed in CEA-positive cancer cells, but not in CEA-negative cells. The expression of yCDglyTK induced cancer cell death following the addition of the prodrug 5-FC, and also elicit "bystander effect" to kill the neighboring cells. Intratumoral injection of CPNP-yCDglyTK complex followed by administration of 5-FC produced marked regression in gastric cancer xenografts. Taken together, our study suggests that the combination of calcium phosphate nanoparticles and suicide gene therapy represents a novel approach for targeting gastric cancer gene therapy.     

A novel fusion suicide gene yeast CDglyTK plays a role in radio-gene therapy of nasopharyngeal carcinoma

To investigate a novel suicide gene for nasopharyngeal carcinoma (NPC) therapy, the yCDglyTK gene was constructed by fusing yeast cytosine deaminase (CD) and herpes simplex type 1 thymidine kinase. The expression of the yCDglyTK gene was detected by RT-PCR and Western blotting, and its bioactivity was demonstrated by an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. An animal study was carried out in which BALB/C nude mice bearing yCDglyTK gene-modified tumors were treated with prodrugs and radiation. Our results revealed that the yCDglyTK gene could be expressed in CNE-2 cells in vitro. In MTT analysis, at the transfection rate of 10%, 66% cells were killed. The synergistic effect of CD and TK showed 91% of yCDglyTK-transfected cells were killed with the treatment of 5-fluorocytosine (5-FC) alone, 60% killed with ganciclovir (GCV) alone, and 75% killed with 5-FC and GCV together. In vivo, the tumor volume in all of the four prodrugs and/or radiation-treated groups were significantly different from that in the PBS-controlled group (P<.01); also yCDglyTK+prodrug+radiation group was different from the other three groups (P<.05). Our findings suggested there was a synergistic antitumor effect when combining suicide gene therapy and radiation, and yCDglyTK has potent antitumor efficacy and may be a candidate suicide gene for cancer therapy.     

Cellular and molecular events associated with the antitumor response induced by the cytosine deaminase/5-fluorocytosine suicide gene therapy system in a rat liver metastasis model

The bacterial cytosine deaminase (CD) gene converts the non-toxic prodrug 5-fluorocytosine (5-FC) into 5-fluorouracil. We have previously shown, in a rat liver metastasis model from colon carcinoma, that intratumoral injection of a CD-expressing plasmid into the animals followed by 5-FC treatment results in the regression of the treated tumor as well as distant uninjected tumors. The aim of this study was to further analyze the mechanisms associated with tumor regression induced upon application of suicide CD/5-FC strategy. Tumor regression was associated with an increased apoptosis, the recruitment of natural killer cells, CD4- and CD8 T lymphocytes within the tumors and an increased expression of several cytokines/chemokines mRNAs. These data indicate that the CD/5-FC suicide strategy is associated with the triggering of cellular and molecular events leading to an efficient antitumor immune response involving both innate and acquired immunity.     

Adipose tissue-derived human mesenchymal stem cells mediated prodrug cancer gene therapy

Human adipose tissue-derived mesenchymal stem cells (AT-MSC) are considered to be a promising source of autologous stem cells in personalized cell-based therapies. Tumor tracking properties of MSC provide an attractive opportunity for targeted transgene delivery into the sites of tumor formation. In the present study, we addressed whether the suicide gene introduction into human AT-MSC could produce a tumor-specific prodrug converting cellular vehicle for targeted chemotherapy. We prepared yeast fusion cytosine deaminase::uracil phosphoribosyltransferase gene-expressing cells [cytosine deaminase (CD)-expressing AT-MSC (CD-AT-MSC)] by retrovirus transduction. We explored their therapeutic potential on a model of human colon cancer in the presence of prodrug 5-fluorocytosine (5-FC). Gene manipulation of human AT-MSC did not sensitize CD-AT-MSC to 5-FC, thus overcoming the inherent disadvantage of suicide effect on cellular vehicle. CD-AT-MSC in combination with 5-FC augmented the bystander effect and selective cytotoxicity on target tumor cells HT-29 in direct coculture in vitro. We confirmed directed migration ability of AT-MSC and CD-AT-MSC toward tumor cells HT-29 in vitro. Moreover, we achieved significant inhibition of s.c. tumor xenograft growth by s.c. or i.v. administered CD-AT-MSC in immunocompromised mice treated with 5-FC. We confirmed the ability of CD-AT-MSC to deliver the CD transgene to the site of tumor formation and mediate strong antitumor effect in vivo. Taken together, these data characterize MSC derived from adipose tissue as suitable delivery vehicles for prodrug converting gene and show their utility for a personalized cell-based targeted cancer gene therapy.     

Systemic administration of a recombinant vaccinia virus expressing the cytosine deaminase gene and subsequent treatment with 5-fluorocytosine leads to tumor-specific gene expression and prolongation of survival in mice.

Suicide gene therapy using the cytosine deaminase (CD) gene and 5-fluorocytosine (5-FC) has shown promising results for the treatment of colon carcinoma cells in vitro. Efficient viral infection and tumor-specific gene delivery is crucial for clinically measurable treatment effects. After proving efficient gene transfer in vitro, we demonstrate here that genes can be delivered to metastatic liver tumors in vivo in a highly selective manner using systemic delivery of a thymidine kinase-deleted (TK-) recombinant vaccinia virus (Western Reserve strain). When the vector was administered systemically in C57BL/6 mice or nude/athymic mice with established disseminated MC38 liver metastases, transgene expression in tumors was usually 1,000 to 10,000-fold higher compared with other organs (n = 160; P < 0.0001). This tumor-specific gene transfer leads to significant tumor responses and subsequent survival benefits after the transfer of the CD gene to liver metastases and subsequent systemic treatment with the prodrug 5-FC (P < 0.0001). We describe reporter gene and survival experiments both in immunocompetent and athymic nude mice, establishing a gene expression pattern over time and characterizing the treatment effects of the virus delivery/prodrug system. Cure rates of up to 30% in animals with established liver metastases show that suicide gene therapy using TK- vaccinia virus as a vector may be a promising system for the clinical application of tumor-directed gene therapy.     

Carcinoembryonic antigen-specific suicide gene therapy of cytosine deaminase/5-fluorocytosine enhanced by the cre/loxP system in the orthotopic gastric carcinoma model

Tumor-specific gene delivery is crucial to achieving successful effects in suicide gene therapy. Carcinoembryonic antigen (CEA) promoter has been widely used for this purpose, but the expression level of tumor-specific promoters such as CEA promoter is generally low. In the previous study, we used the Cre/loxP system and showed that LacZ expression by the CEA promoter was remarkably enhanced and maintained its specificity using the Cre/loxP regulation system. In this study, the Cre/loxP system was first applied to augmentation of selective expression of the cytosine deaminase (CD) gene as a suicide gene therapy in CEA-producing cells. The double infection with AxCEANCre expressing Cre recombinase under the control of the CEA promoter and AxCALNLCD expressing the CD gene under the control of the CAG promoter by the Cre switching system rendered CEA-producing tumor cells 13-fold more sensitive to 5-fluorocytosine (5-FC) compared with the single infection with AxCEACD expressing CD gene driven by the CEA promoter. The therapeutic efficacy of the enhanced CD/5-FC suicide gene therapy was evaluated in orthotopic implantation models of human gastric carcinoma. Adenovirus vectors (1 x 10(9) plaque-forming units) were administered i.p. into mice three times, and then 5-FC was administered i.p. for the next 10 days. Tumor volume and weight in mice treated with AxCEANCre and AxCALNLCD/5-FC were significantly reduced as compared with those in mice treated not only with Mock (AxCALacZ) but also with AxCEACD/5-FC (P < 0.0001). This beneficial effect on tumor burden was also reflected in the overall survival. The survival periods of the mice treated with AxCEANCre and AxCALNLCD/5-FC were longer than those of mice treated with Mock or AxCEACD/5-FC (P < 0.01). These results suggested that application of the Cre/loxP system could provide a new approach for enhanced selective suicide gene therapy of CD/5-FC for the treatment of advanced gastric carcinoma.     

Methylglyoxal suppresses human colon cancer cell lines and tumor growth in a mouse model by impairing glycolytic metabolism of cancer cells associated with down-regulation of c-Myc expression

Methylglyoxal (MG) is a highly reactive dicarbonyl compound exhibiting anti-tumor activity. The anti-tumor effects of MG have been demonstrated in some types of cancer, but its role in colon cancer and the mechanisms underlying this activity remain largely unknown. We investigated its role in human colon cancer and the underlying mechanism using human colon cancer cells and animal model. Viability, proliferation, and apoptosis were quantified in DLD-1 and SW480 colon cancer cells by using the Cell Counting Kit-8, plate colony formation assay, and flow cytometry, respectively. Cell migration and invasion were assessed by wound healing and transwell assays. Glucose consumption, lactate production, and intracellular ATP production also were assayed. The levels of c-Myc protein and mRNA were quantitated by western blot and qRT-PCR. The anti-tumor role of MG in vivo was investigated in a DLD-1 xenograft tumor model in nude mice. We demonstrated that MG inhibited viability, proliferation, migration, and invasion and induced apoptosis of DLD-1 and SW480 colon cancer cells. Treatment with MG reduced glucose consumption, lactate production, and ATP production and decreased c-Myc protein levels in these cells. Moreover, MG significantly suppressed tumor growth and c-Myc expression in vivo. Our findings suggest that MG plays an anti-tumor role in colon cancer. It inhibits cancer cell growth by altering the glycolytic pathway associated with downregulation of c-Myc protein. MG has therapeutic potential in colon cancer by interrupting cancer metabolism.     

The efficacy of combination therapy using adeno-associated virus-mediated co-expression of apoptin and interleukin-24 on hepatocellular carcinoma

Multigene-based combination therapy is an effective practice in cancer gene therapy. Apoptin is a chicken anemia virus-derived, p53-independent, Bcl-2-insensitive apoptotic protein with the ability to specifically induce apoptosis in various human tumor cells. Interleukin-24 (IL-24) displays ubiquitous antitumor property and tumor-specific killing activity. Adeno-associated virus (AAV) is a promising gene delivery vehicle due to its advantage of low pathogenicity and long-term gene expression. In this study, we assessed the efficacy of combination therapy using AAV-mediated co-expression of apoptin and interleukin-24 on hepatocellular carcinoma in vitro and in vivo. Our results showed that AAV-mediated co-expression of IL-24 and apoptin significantly suppressed the growth and induced the apoptosis of HepG2 cells in vitro. Furthermore, AAV-mediated combined treatment of IL-24 and apoptin significantly suppressed tumor growth and induced apoptosis of tumor cells in xenograft nude mice. These data suggest that AAV vectors that co-express apoptin and IL-24 have great potential in cancer gene therapy.     

Oncolytic virus-mediated tumor radiosensitization in mice through DNA-PKcs-specific shRNA

One of the key issues in cancer radiotherapy research is to sensitize tumor cells to the cell killing effects of ionizing radiation while leaving normal tissues intact. One potential approach to achieve this is through tumor-specific targeting of DNA repair genes. In this study, we engineered a replication-deficient adenovirus encoding a mini shRNA gene targeted to the DNA-PKcs gene, which is involved in double strand break DNA repair, and evaluated its anti-tumor efficacy in combination with radiotherapy. Our shRNA-encoding adenovirus showed significant efficacy in down-regulating the levels of the DNA-PKcs protein that was accompanied by increased radiation sensitivity in the human HCT116 colon cancer cells. However, when delivered intratumorally to xenograft human tumors, minimal anti-tumor effects of the virus were seen either alone or in combination with radiation therapy, suggesting an inefficiency of the non-replicative adenovirus in delivering shRNA genes to the tumor mass. When a conditionally replicative adenovirus targeted to telomerase-positive tumor cells was used in conjunction with the DNA-PKcs-targeted shRNA-encoding non-replicative adenovirus, the efficiency of tumor-specific anti-DNA-PKcs shRNA gene expression was enhanced significantly. Most importantly, this enhanced shRNA expression led to significant anti-tumor efficacy of concurrently delivered radiation therapy. Our results suggest our shRNA-based DNA-PKcs- targeting approach in combination with tumor-targeting replicative adenovirus is a promising method to sensitize solid tumors to radiation therapy.     

CD自杀基因联合淋巴细胞趋化因子基因疗法的肿瘤治疗作用及免疫机理研究

本研究以腺病毒作为载体,将大肠杆菌胞嘧啶脱氨酶(CD)基因与小鼠淋巴细胞趋化因子(Ltn)基因体内联合转染,观察了其抗肿瘤效应并分析了免疫机理.小鼠皮下接种结肠腺癌CT26细胞后3天,肿瘤局部注射表达Ltn的重组腺病毒AdLtn和表达CD的重组腺病毒AdCD,然后连续10天给予5一氟胞嘧啶(5-FC)300mg/kg进行治疗,结果表明,联合治疗组荷瘤小鼠皮下肿瘤结节的生长受到明显抑制,小鼠存活期明显长于单用AdLtn治疗组或单用AdCD/5-FC治疗组.经联合治疗后小鼠脾细胞的NK活性和对(37结肠腺癌细胞的CTL杀伤活性明显增强.瘤体细胞FACS分析结果表明,经联合基因治疗后,肿瘤组织CD4~ 、CD8~ 细胞浸润增加,结肠腺癌细胞表达H-2Kd和B7-1分子明显增加.提示经CD自杀基因和Ltn基因联合治疗后,肿瘤细胞免疫原性增加.本研究结果表明联合应用自杀基因和Ltn基因治疗可以提高机体对肿瘤细胞免疫的应答,增加机体的抗肿瘤作用,是肿瘤基因治疗中一条新的途径.     

Liposomal formulation of 5-fluorocytosine in suicide gene therapy with cytosine deaminase--for colorectal cancer

It is generally accepted that successful gene therapy depends on two major factors: tumor-specific expression of a therapeutic gene and the efficient transfer of a therapeutic gene to tumor cells. For gene-directed enzyme prodrug therapy (GDEPT) involving Escherichia coli cytosine deaminase (CD) and 5-fluorocytosine (5-FC), several tumor-specific promoters and virus-based vectors were used. No attention whatsoever was paid to the way of 5-FC delivery to solid tumors, despite the fact that the delivery of drugs to such tumors is generally low because of their insufficient transfer from the blood. To compare the effectiveness of GDEPT with free and liposomal 5-FC, the prodrug was encapsulated in liposomes composed of dipalmitoylphosphatidylcholine (DPPC) and cholesterol (1:1). When the liposomal form of 5-FC was administered i.v., mice treated with a dose of 5mg of liposomal 5-FC/kg body weight for 10 days, showed complete regression of transplanted tumors and complete cure was observed, whereas in animals treated with the same amounts of the free prodrug, 50% tumor regression and only insignificantly prolonged median survival were found. In summary, these results showed a remarkable enhancement of the antitumor effects of the liposomal form of 5-FC in comparison with the free prodrug. Therapy with liposomal 5-FC thus represents a new approach to achieving a high local concentration of the prodrug for suicide gene therapy using E. coli CD.     

Verticillin A overcomes apoptosis resistance in human colon carcinoma through DNA methylation-dependent upregulation of BNIP3

Drug resistance is a major cause of failure in cancer chemotherapy. Therefore, identification and combined use of adjuvant compounds that can overcome drug resistance may improve the efficacy of cancer therapy. We screened extracts of Verticillium species-infected mushrooms for antitumor compounds and identified the compound Verticillin A as an inducer of hepatoma cell apoptosis in vitro and an inhibitor of tumor xenograft growth in vivo. Verticillin A exhibited a potent apoptosis-sensitizing activity in human colon carcinoma cells exposed to TRAIL or Fas in vitro. Furthermore, Verticillin A effectively sensitized metastatic human colon carcinoma xenograft to TRAIL-mediated growth inhibition in vivo. At the molecular level, we observed that Verticillin A induces cell-cycle arrest in the G? phase of the cell cycle in human colon carcinoma cells, markedly upregulating BNIP3 in both hepatoma and colon carcinoma cells. Notably, silencing BNIP3 decreased the sensitivity of tumor cells to Verticillin A-induced apoptosis in the absence or presence of TRAIL. We found that the BNIP3 promoter is methylated in both human hepatoma and colon carcinoma cells and tumor specimens. Verticillin A upregulated the expression of a panel of genes known to be regulated at the level of DNA methylation, in support of the concept that Verticillin A may act by demethylating the BNIP3 promoter to upregulate BNIP3 expression. Taken together, our findings identify Verticillin A as a potent apoptosis sensitizer with great promise for further development as an adjuvant agent to overcome drug resistance in human cancer therapy.     

Antitumor effects of FP3 in combination with capecitabine on PDTT xenograft models of primary colon carcinoma and related lymphatic and hepatic metastases

FP3 is an engineered protein which contains the extracellular domain 2 of VEGF receptor 1 (Flt-1) and extracellular domain 3 and 4 of VEGF receptor 2 (Flk-1, KDR) fused to the Fc portion of human immunoglobulin G 1. Previous studies demonstrated its antiangiogenic effects in vitro and in vivo, and its antitumor activity in vivo. In this study, patient-derived tumor tissue (PDTT) xenograft models of primary colon carcinoma and lymphatic and hepatic metastases were established for assessment of the antitumor activity of FP3 in combination with capecitabine. Xenografts were treated with FP3, capecitabine, alone or in combination. After tumor growth was confirmed, volume and microvessel density in tumors were evaluated. Levels of VEGF, and PCNA in the tumor were examined by immunohistonchamical staining, level of thymidine phosphorylase (TP) was examined by ELISA, and levels of related cell signaling pathways proteins expression were examined by western blotting. FP3 in combination with capecitabine showed significant antitumor activity in three xenograft models (primary colon carcinoma, lymphatic metastasis, and hepatic metastasis). The microvessel density in tumor tissues treated with FP3 in combination with capecitabine was lower than that of the control. Antitumor activity of FP3 in combination with capecitabine was significantly higher than that of each agent alone in three xenograft models (primary colon carcinoma, lymphatic metastasis, and hepatic metastasis). This study indicated that addition of FP3 to capecitabine significantly improved tumor growth inhibition in the PDTT xenograft models of primary colon carcinoma and lymphatic and hepatic metastases.     

Colon cancer cell-derived tumor necrosis factor-alpha mediates the tumor growth-promoting response in macrophages by up-regulating the colony-stimulating factor-1 pathway

The interplay between malignant and stromal cells is essential in tumorigenesis. We have previously shown that colony-stimulating factor (CSF)-1, matrix metalloprotease (MMP)-2, and vascular endothelial growth factor (VEGF)-A production by stromal cells is enhanced by CSF-1-negative SW620 colon cancer cells. In the present study, the mechanisms by which colon cancer cells up-regulate host factors to promote tumorigenesis were investigated. Profiling of tumor cell cytokine expression in SW620 tumor xenografts in nude mice showed increased human tumor necrosis factor (TNF)-alpha mRNA expression with tumor growth. Incubation of macrophages with small interfering (si) RNAs directed against TNF-alpha or TNF-alpha-depleted SW620 cell conditioned medium versus SW620 cell conditioned medium failed to support mouse macrophage proliferation, migration, and expression of CSF-1, VEGF-A, and MMP-2 mRNAs. Consistent with these results, human TNF-alpha gene silencing decreased mouse macrophage TNF-alpha, CSF-1, MMP-2, and VEGF-A mRNA expression in macrophages cocultured with human cancer cells. In addition, inhibition of human TNF-alpha or mouse CSF-1 expression by siRNA reduced tumor growth in SW620 tumor xenografts in mice. These results suggest that colon cancer cell-derived TNF-alpha stimulates TNF-alpha and CSF-1 production by macrophages, and that CSF-1, in turn, induces macrophage VEGF-A and MMP-2 in an autocrine manner. Thus, interrupting tumor cell-macrophage communication by targeting TNF-alpha may provide an alternative therapeutic approach for the treatment of colon cancer.     

Survivin与大肠癌关系的研究进展

Survivin是一个肿瘤特异性的凋亡抑制因子,在细胞中呈周期依赖性表达,调节G2/M期,并可直接抑制Caspase-3和Caspase-7的活性。在肿瘤的发生发展中,Survivin与肿瘤细胞的凋亡负相关,与血管形成和细胞增殖活性正相关。Survivin在包括大肠癌在内的多种肿瘤组织中均高表达。Survivin在大肠癌的生长和转移中起了重要的作用,Survivin表达上调可预示生存期缩短和预后不良。针对Survivin及其受体的肿瘤治疗也取得了很大的进展。提示Survivin可能是大肠癌诊断和治疗的新靶点。     

Inhibition of cell proliferation, induction of apoptosis, reactivation of DLC1, and modulation of other gene expression by dietary flavone in breast cancer cell lines

BACKGROUND: Dietary flavone was previously shown to increase the expression of deleted in liver cancer-1 gene (DLC-1) in HT-29 colon carcinoma cell line [Herzog A, Kindermann B, Doring F, Daniel H, Wenzel U. Pleiotropic molecular effects of the pro-apoptotic dietary constituent flavone in human colon cancer cells identified by protein and mRNA expression profiling. Proteomics 2004;4:2455-64]. DLC-1 that encodes a Rho GTPase-activating protein, functions as a tumor suppressor gene and is frequently inactivated or down-regulated in several common cancers. Restoration of DLC-1 expression suppresses in vitro tumor cells proliferation and tumorigenicity in vivo. METHODS: Here, the effect of flavone was examined in several DLC-1-deficient cell lines derived from different types human cancer using assays for cell proliferation, gene expression and transfer. RESULTS: We show that exposure to 150 microM flavone increased DLC1 expression in breast but not in liver or prostate carcinoma cells or a nonmalignant breast epithelial cell line. Flavone restored the expression of DLC1 in the breast carcinoma cell lines MDA-MB-468, MDA-MB-361, and BT20 as well as in the colon carcinoma cell line HT-29 all of which are DLC-1-negative due to promoter hypermethylation. We further show that flavone inhibited cell proliferation, induced cell cycle arrest at G(2)-M, increased p21(Waf1) gene expression, and caused apoptosis. Microarray analysis of these aggressive and metastatic breast carcinoma cells revealed 29 flavone-responsive genes, among which the DNA damage-inducible GADD genes were up-regulated and the proto-oncogene STMN1 and IGFBP3 were down-regulated. CONCLUSIONS: Flavone-mediated alterations of genes that regulate tumor cell proliferation, cell cycle, and apoptosis contribute to chemopreventive and antitumoral effects of flavone. Alone or in combination with demethylating agents, flavone may be an effective adjunct to chemotherapy in preventing breast cancer metastasis.     

CEA promoter-regulated oncolytic adenovirus-mediated Hsp70 expression in immune gene therapy for pancreatic cancer

Gene therapy is an important means for the comprehensive treatment of pancreatic cancer. Challenges associated with gene therapy include control of vector security and effective genetic screening. In this paper, a CEA promoter-regulated oncolytic adenovirus vector was constructed. The reporter gene assay demonstrated that the viral vector was confirmed to have tumor-specific replication features. In vitro cytology studies showed that the CEA promoter regulated the proliferation of the adenovirus vector carrying the Hsp70 gene (AdCEAp-Hsp70), which significantly increased the expression levels of Hsp70 in the CEA-positive pancreatic cancer cells, resulting in an overall reduction in the survival of cancer cells. In the human pancreatic cancer Panc-1 xenograft model in immune deficient nude mice, the CEA promoter-regulated adenovirus AdCEAp-Hsp70 significantly inhibited tumor growth. In the rat pancreatic cancer DSL-6A/C1 xenograft model in rats, the viral proliferation and high expression levels of Hsp70 promoted the interstitial infiltration of CD4+, CD8+ and gamma/delta T cells into tumors, induced host secretion of the cytokines TGF-β, INF-γ, and IL-6 and had a dual anti-tumor effects that completely inhibited the growth of pancreatic cancer. The results demonstrated that the oncolytic adenovirus under the control of CEA promoter provides additional assurances regarding the safety and efficiency of cancer gene therapy. This gene therapy model improves anti-cancer efficiency and has broad applications and developmental prospects.     

Enforced dual‐specificity tyrosine‐regulated kinase 2 expression by adenovirus‐mediated gene transfer inhibits tumor growth and metastasis of colorectal cancer

Colorectal cancer is one of the most common gastrointestinal tumors with good outcomes; however, with distant metastasis, the outcomes are poor. Novel treatment methods are urgently needed. Our in vitro studies indicate that dual‐specificity tyrosine‐regulated kinase 2 (DYRK2) functions as a tumor suppressor in colorectal cancer by regulating cell survival, proliferation, and apoptosis induction. In addition, DYRK2 expression is decreased in tumor tissues compared to nontumor tissues in colorectal cancer, indicating a correlation with clinical prognosis. In this context, we devised a novel therapeutic strategy to overexpress DYRK2 in tumors by adenovirus‐mediated gene transfer. The present study shows that overexpression of DYRK2 in colon cancer cell lines by adenovirus inhibits cell proliferation and induces apoptosis in vitro. Furthermore, in mouse subcutaneous xenograft and liver metastasis models, enforced expression of DYRK2 by direct or intravenous injection of adenovirus to the tumor significantly inhibits tumor growth. Taken together, these findings show that adenovirus‐based overexpression of DYRK2 could be a novel gene therapy for liver metastasis of colorectal cancer.