Specific CEA-producing colorectal carcinoma cell killing with recombinant adenoviral vector containing cytosine deaminase gene

The targeted gene (KDRP-CD/TK) therapy of breast cancer mediated by SonoVue and ultrasound irradiation in vitro

Suicide gene therapy has become an effective therapy for breast cancer, and ultrasound targeted microbubble destruction (UTMD) has become a popular topic in the gene therapy field. In this study, MCF-7 cells with the KDR promoter and LSl74T cells without the KDR promoter were transfected with the recombinant plasmid pEGFP-KDRP-CD/TK using UTMD. The recombinant plasmid pEGFP-KDRP-CD/TK was transfected into MCF-7 and LS174T cells successfully with no significant difference in transfection efficiency (p>0.05). By RT-PCR, the CD/TK fusion gene was shown to be expressed in MCF-7 cells but not expressed in LS174T cells. In a cytotoxicity experiment, transgenic MCF-7 cells were sensitive to the prodrugs 5-FC and GCV. When both 5-FC and GCV were administered, the rate of cellular inhibition was significantly greater than that achieved when only one of the prodrugs was administered (p<0.001). Moreover, the inhibition rates achieved administering 5-FC, GCV and both 5-FC and GCV were all significantly greater than the gene transfection rate of 21.92±3.64% (p<0.001). However, transgenic LS174T cells were not sensitive to any prodrug. These results demonstrated that UTMD is a safe, effective and targeted gene delivery system. Also, the KDR promoter can drive expression of the CD/TK double suicide gene target in MCF-7 cells, and the targeted killing effect of the KDRP-CD/TK gene on MCF-7 cells in vitro has good synergy with expression of the CD/TK fusion gene.

(1)H-MRS can detect aberrant glycosylation in tumour cells: a study of the HeLa cell line

Glycosylation is the most abundant and diverse form of post-translational modification of proteins. Two types of glycans exist in glycoproteins: N-glycans and O-glycans often coexisting in the same protein. O-glycosylation is frequently found on secreted or membrane-bound mucins whose overexpression and structure alterations are associated with many types of cancer. Mucins have several cancer-associated structures, including high levels of Lewis antigens characterized by the presence of terminal fucose. The present study deals with the identification of MR signals from N-acetylgalactosamine and from fucose in HeLa cells by detecting a low-field signal in one-dimensional (1D) spectra assigned to the NH of N-acetylgalactosamine and some cross peaks assigned to fucose in two-dimensional (2D) spectra. The increase of Golgi pH by treatment with ammonium chloride allowed the N-acetylgalactosamine signal assignment to be confirmed. Behaviour of MR peak during cell growth and comparison with studies from literature taken together made it possible to have more insight into the relationship between aberrantly processed mucin and the presence of non-processed N-acetylgalactosamine residues in HeLa cells. Fucose signals, tentatively ascribed to residues bound to galactose and to N-acetylglucosamine, are visible in both intact cell and perchloric acid spectra. Signals assigned to fucose bound to galactose are more evident in ammonium chloride-treated cells where structural changes of mucin-related Lewis antigens are expected as a result of the higher Golgi pH. A common origin for the N-acetylgalactosamine and fucose resonances attributing them to aberrantly processed mucin can be inferred from the present results.

Antitumor activity of mutant bacterial cytosine deaminase gene for colon cancer

AIM: To evaluate bacterial cytosine deaminase (bCD) mutant D314A and 5-fluorocytosine (5-FC) for treatment of colon cancer in a mouse model.

METHODS: Recombinant lentivirus vectors that contained wild-type bCD gene (bCDwt), and bCD mutant D314A gene (bCD-D314A) with green fluorescence protein gene were constructed and used to infect human colon carcinoma LoVo cells, to generate stable transfected cells, LoVo/null, LoVo/bCDwt or LoVo/bCD-D314A. These were injected subcutaneously into Balb/c nude mice to establish xenograft models. Two weeks post-LoVo cell inoculation, PBS or 5-FC (500 mg/kg) was administered by intraperitoneal (i.p.) injection once daily for 14 d. On the day after LoVo cell injection, mice were monitored daily for tumor volume and survival.

RESULTS: Sequence analyses confirmed the construction of recombinant lentiviral plasmids that contained bCDwt or bCD-D314A. The lentiviral vector had high efficacy for gene delivery, and RT-PCR showed that bCDwt or bCD-D314A gene was transferred to LoVo cells. Among these treatment groups, gene delivery or 5-FC administration alone had no effect on tumor growth. However, bCDwt/5-FC or bCD-D314A/5-FC treatment inhibited tumor growth and prolonged survival of mice significantly (P < 0.05). Importantly, the tumor volume in the bCD-D314A/5-FC-treated group was lower than that in the bCDwt/5-FC group (P < 0.05), and bCD-D314A plus 5-FC significantly prolonged survival of mice in comparison with bCDwt plus 5-FC (P < 0.05).

CONCLUSION: The bCD mutant D314A enhanced significantly antitumor activity in human colon cancer xenograft models, which provides a promising approach for human colon carcinoma therapy.

Targeted killing effects of double CD and TK suicide genes controlled by survivin promoter on gastric cancer cell

Suicide genes such as cytosine deaminase (CD) and herpes simplex virus thymidine kinase (TK) encode products that convert nontoxic substances (prodrugs) into toxic metabolites. Studies in recent years indicated that survivin(sur) expression was associated with the biological behaviors of gastric carcinoma. In the present study, targeted killing effects of double CD and TK suicide genes controlled by survivin promoter on gastric cancer cell were investigated, the recombinant pSCT vector containing CD and TK genes driven by sur promoter was constructed and transfected into SGC-7901 cells. After adding the CCV and 5-FC, the effects of double suicide genes on cell growth, cell cycle and proliferation were determined by MTT assay and flow cytometry (FCM). The results showed that sur promoter could specifically drive the expression of double CD/TK gene in SGC-7901 cells, whereas not in the normal GES-1 cell. After using CCV and 5-FC, the growth of SGC-7901 cells was inhibited. G1 phase proportion was significantly higher in SGC-7901 cells transfected with double suicide genes than the untransfected cells. These results suggest that CD and TK double suicide genes driven by sur promoter could provide a new approach for enhancing selective suicide gene therapy of CD/5-FC for the treatment of advanced gastric carcinoma.

Construction of humanized carcinoembryonic antigen specific single chain variable fragment and mitomycin conjugate

AIM: To construct a new target-oriented conjugate of humanized carcinoembryonic antigen (CEA) specific single chain variable fragment (scFv) and mitomycin (MMC) against colorectal cancer, and to investigate its influence on the growth and apoptosis of colorectal cancer cells.

METHODS: The primer was designed according to the gene sequence described in reference 16, which respectively contains restriction enzyme cleavage sites BamHI and EcoRI in its upstream and downstream. PCR was performed with the plasmid as template containing genes of humanized anti-CEA scFv. The product was digested by BamHI and EcoRI, and connected to an expression vector which also has the restriction enzyme cleavage sites BamHI and EcoR. Expression of the reaction was induced by isopropy-β -D-thiogalactoside (IPTG). Then the expression product was covalently coupled with MMC by dextran T-40. The immunoreactivity of the conjugate against colorectal cancer cells as well as CEA was measured by enzyme linked immunosorbent assay (ELISA). The inhibiting ratio of conjugate on the growth of colorectal cancer cells was also measured by ELISA. The effect of conjugate on the apoptosis of colorectal cancer cells was determined by flow cytometry (FCM).

RESULTS: Restriction endonuclease cleavage and gene sequencing confirmed that the expression vector was successfully constructed. Sodium dodecyl sulfate polyacrylamide gel electropheresis (SDS-PAGE) confirmed that this vector correctly expressed the fusion protein. ELISA confirmed that the conjugate had quite a strong immunoreactivity against colorectal cancer cells and CEA. The conjugate had inhibitory effects on colorectal cancer cells in a concentration-dependent manner and could induce apoptosis of colorectal cancer cells in a concentration-dependent manner.

CONCLUSION: The CEA-scFv-MMC conjugate can be successfully constructed and is able to inhibit the growth and induce apoptosis of colorectal cancer cells.

Antitumor effects of cytosine deaminase and thymidine kinase fusion suicide gene under the control of mdr1 promoter in mdr1 positive leukemia cells

The multidrug resistance (mdr) mediated by P-glycoprotein (P-gp), the mdr1 gene product, is one of the major obstacles in leukemia treatment. The present study was designed to explore a suicide gene therapy approach targeting mdr1 for reversal of P-gp-mediated mdr in the mdr positive K562/A02 cells. To study targeted killing effects of cytosine deaminase (CD)-thymidine kinase (TK) fusion suicide gene on multi-drug resistant leukemia, the CD-TK fusion suicide gene expression vector driven by mdr1 promoter was constructed and transferred into K562 and K562/A02 cells using lipofectintrade mark 2000. RT-PCR was used to demonstrate that there were CD and TK genes expression in K562/A02 cells, but not in K562 cells. MTT analysis showed that, compared with that in K562/CDTK, the survival rate of K562/A02-CDTK cells decreased and at the same time the apoptotic rate increased after treatment with GCV and 5-FC (P < 0.05). In vivo studies showed that the tumor volume in the prodrug treated K562/A02-CDTK groups was significantly less than that in the NS-control and K562-CDTK groups (P < 0.05). These findings show that the CD and TK fusion suicide gene expression driven by mdr1 promoter is effective in killing multidrug resistant K562/A02 cells.

Construction of double suicide genes system controlled by MDR1 promoter with targeted expression in drug-resistant glioma cells

The multiple drug resistance protein (MDR1) is frequently overexpressed in human glioma. The aim of this study is to clone the MDR1 promoter from C6/ADR, construct the double suicide genes expressive vector controlled by MDR1 promoter, and explore its targeted expression in C6/ADR cells. MDR1 promoter from C6/ADR genomic DNA, which was linked with T vector, was amplified by using Polymerase chain reaction (PCR). After cut by NdeI and HindIII, MDR1 promoter was cloned into pcDNA3-TK (thymidine kinase) plasmid. The cytosine deaminase (CD) gene from pcDNA3-CD-TK plasmid was directly cloned into the above vector to construct pcDNA3-MDR1-promoter-CD-TK vector. Then this vector was transfected into C6 and C6/ADR cells respectively by liposome. After selection by G418, the tumor cell lines were stably established. Then these cell lines were examined through PCR and RT-PCR to respectively detect the integration and expression of TK and CD genes. The results showed the length and sequence of MDR1 promoter amplified by PCR were confirmed by DNA sequencing. The pcDNA3-MDR1-promoter-CD-TK expression vectors were constructed successfully. PCR indicated the double suicide genes were integrated into C6 and C6/ADR cells. RT-PCR revealed that CD and TK genes expressed in C6/ADR/CD-TK cells, whereas not in C6/CD-TK cells. In conclusions, construction of expressive vector containing double suicide genes controlled by MDR1 promoter with targeted expression in C6/ADR will provide a sound basis for targeted gene therapy for multidrug resistance (MDR) glioma.

Radioiodine therapy of colon cancer following tissue-specific sodium iodide symporter gene transfer

We investigated the feasibility of using radioiodine therapy in colon carcinoma cells (HCT 116) following tumor-specific expression of the human sodium iodide symporter (hNIS) using the carcinoembryonic antigen (CEA) promoter. HCT 116 cells were stably transfected with an expression vector, in which hNIS cDNA has been coupled to a CEA promoter fragment. This promoter is responsible for tissue-specific expression of CEA in gastrointestinal tract epithelium, and has been shown to target therapeutic genes to colorectal cancer cells. Functional NIS expression was confirmed by iodide uptake assay, Western blot analysis, immunostaining and in vitro clonogenic assay. The stably transfected HCT 116 cells concentrated (125)I about 10-fold in vitro without evidence of iodide organification. In contrast, transfection of control cancer cells without CEA expression did not result in iodide accumulation. Western blot analysis using a hNIS-specific antibody revealed a band of approximately 90 kDa. In addition, immunostaining of stably transfected HCT 116 cells revealed hNIS-specific membrane-associated immunoreactivity. In an in vitro clonogenic assay approximately 95% of stably transfected HCT 116 cells were killed by exposure to (131)I, while only about 5% of NIS-negative control cells were killed. Further, using an adenovirus carrying the NIS gene linked to the CEA promoter, high levels of tumor-specific radioiodide accumulation were induced in HCT 116 cells. In conclusion, a therapeutic effect of (131)I has been demonstrated in colon carcinoma cells following induction of tumor-specific iodide uptake activity by CEA promoter-directed NIS expression in vitro. This study demonstrates the potential of NIS as a therapeutic gene allowing radioiodine therapy of colon cancer following tumor-specific NIS gene transfer.

Screening of human colorectal carcinoma associated antigen genes by SEREX

AIM

To screen and identify the human colorectal carcinoma associated antigen genes.

METHODS

Three human colorectal carcinoma cDNA phage expression libraries were constructed. They were screened from autologous and allogeneic sera of colorectal cancer patients by SEREX (serological identification of antigens by recombinant expression cloning). The sera were pre-absorbed by the extract E. coli XL1-blue. Four different serum-reactive cDNA clones were isolated by immunoscreening from a colon cancer-derived cDNA expression library. Positive clones were amplified by plate culture, the purified lambda phage DNA was cut by Sfi I restriction endonucleases and amplified with PCR in order to identify the insert size of cDNA by electrophresis.

RESULTS

Three cDNA phage expression libraries were constructed. The titer of library was 2.39×10⁶ nfu/L, 2.07×10⁶ nfu/L and 1.86×10⁶ nfu/L respectively, The range of the fragment length of exogenously inserted cDNA was between 0.5-4 kb, the average was 1.4 kb, 1.6 kb and 1.3 kb, respectively. Four gene clones were obtained by SEREX screening, the length of their insert fragments was 2.4 kb, 1.8 kb, 2.3 kb and 2.2 kb, respectively.

CONCLUSION

To screen and identify human colorectal carcinoma cDNA phage expression libraries by SEREX is a useful method to search for human colorectal carcinoma associated antigen genes. It is important for early diagnosis and research of recombinant vaccine for colorectal cancer.

Gastrin receptor antagonist combined with cytosine deaminase suicide gene therapy enhances killing of colorectal carcinoma

AIM

To investigate the killing effect of cytosine deaminase/5-fluorocytosine on colorectal carcinoma when combined with gastrin receptor antagonist.

METHODS

Plasmid G1CEACDNa was transferred into the LoVo cell line using liposomes method. The growth curve of cells was observed when cultured with 5-FC (1 mmol/L) or/and CI-988 (1×10^-8mmol/L) in RPMI-1 640+100 ml/L fatal bovine serum. The killing efficiency was measured by MTT method. The submicroscopic structure of cells was observed by electron microscope, apoptosis was verified by a flow cytometer . CD⁺ LoVo cells were were. inoculated s.c. in athymic nude mice followed by 5-fluorocysine or/and CI-988 treatment for 20 d. these nude mice were killed with their tumor weight determined. Then tumor tissue was stained with hematoxylin and eosin, the submicroscopic structure of cells was observed by electron microscope.

RESULTS

After treated with 5-FC or CI-988,the inhibition rate of CD⁺ LoVo cells was 90 % and 50 %, respectively. When c these two reagents were used in combination, the inhibition rate was 40 % and 97 % on 3 d and 6 d, respectively. By MTT method, combination of CD/5-FC and CI-988 possessed superior killing effect in comparison to single therapy (0.53±0.05 vs 0.49±0.02, 0.38±0.06, F =29.5536, n =5, P <0.01). Electron microscope and flow cytometer verified that cells were apoptosized after exposed to 5-FC (1 mmol/L) and CI-988(1×10^-8 mmol/L) 72 h. Significant anti-tumor effect was observed in nude mice bearing CD+ LoVo cells followed with 5-FC(500mg/kg body weight i.p. injection per day) or CI-988 (10 mg/kg per day orally), the inhibition rate were 69.4% and 49.5%,respectively. When these two reagents were used in combination, the inhibition rate was 81.5 % that was higher compared to single therapy (0.42±0.12 vs 0.69±0.11, 1.22±0.22, F =33.1709, n =5, P <0.05).There were apoptosis bodies in submicroscopic structure.

CONCLUSION

Gastrin receptor antagonist canelevate the killing effect of CD/5-FC on colorectal carcinoma. Apoptosis is possibly one of the reasons of the synergistic action.

Tumor necrosis factor-related apoptosis-inducing ligand gene on human colorectal cancer cell line HT29

AIM: To evaluate the therapeutic efficiency of Tumor Necrosis Factor-related Apoptosis-inducing Ligand (TRAIL) gene on human colorectal cancer cell line HT29.

METHODS: Human embryonal kidney cells transformed by introducing sheared fragments of Ad5 DNA (293 cell) were used for amplification of adenoviral vectors: Ad/GT-TRAIL, Ad/GT-Bax, Ad/GT-LacZ and Ad/PGK-GV16. Human colorectal cancer cell line HT29 was transfected with binary adenovirus-mediated TRAIL gene. Bax gene was used as positive control, LacZ gene was used as the vector control, and cells treated with PBS only were used as a mock control. The morphological changes, cell growth and apoptosis were measured by reversmicroscope, MTT method and flow cytometry.

RESULTS: All adenoviral vectors titer determined by optical absorbency at A260nm were 1 × 10¹⁰ viral particle/ml(vp/ml). Obviously morphological changes of HT29 cells were observed when infected with Ad/GT-TRAIL, and these changes were much more obviously when Ad/PGK-GV16 was coinfected. The cell suppression percentage and the percentage of apoptotic cells were 52.5% and 16.5% respectively when infected with Ad/GT-TRAIL alone, while combining with Ad/PGK-GV16, the growth of HT29 was suppressed by 85.2% and the percentage of apoptotic cells was 35.9%. It showed a significantly enhanced therapeutic efficiency with binary system (P < 0.05).

CONCLUSION: A binary adenoviral vector system provides an effective approach to amplify viral vectors that express potentially toxic gene, TRAIL. Ad/GT-TRAIL showed a significantly enhanced therapeutic efficiency for HT29 when coinfected with Ad/PGK-GV16. Ad/GT-TRAIL could induce apoptosis of HT29 and inhibit its growth.

Killing effect of CD/5-FC system on human colon cancer cell lines SW 480 and LoVo

AIM

To investigate the killing effect of carcinoembryonic antigen (CEA) and tissue-specific cytosine deaminase (CD)/5-fluorocytosine (5-FC) system on human colorectal carcinoma cell lines LoVo and SW480 in vitro.

METHODS

Recombinant retroviral vector G1CEACDNa was constructed, in which the CD gene was controlled under the CEA promoter, and retroviral vector pCD2 were introduced through liposome technique respectively to the human colorectal carcinoma cell lines LoVo and SW480. Expression of CEA was high and low in both the cell lines respectively. The cells were selectively cultured in G418. The proliferative colonies were treated with 5-FC.

RESULTS

After the transfection, LoVo-CEACD cells and LoVo-CD cells were more sensitive to 5-FC than their parental cells (P<0.01, t = 5.688, n = 9; P<0.01, t = 3.136, n = 9), and SW480-CEACD cells and SW480-CD cells were more sensitive than their parental cells as well (P<0.01, t = 3.437, n = 9; P <0.01, t = 3.516, n = 9). Furthermore, the LoVo-CEACD cells were more sensitive to 5-FC than the LoVo-CD cells (P <0.05, t =2.183, n =9) while the SW480-CEACD cells were less sensitive than SW480-CD cells.TheLoVo-CEACD cells displayed a higher anti-tumor effect than SW480-CEACD cells in vitro. The bystander effect in all cells transfected with CD gene were observed in this study.

CONCLUSION

The CEA tissue-specific CD/5-FC system displays an obvious targeting anti-tumor effect on human colorectal carcinoma cell lines LoVo and SW480, but the killing effect on the LoVo-CEACD cells is higher than that on the SW480-CEACD cells in vitro.

Pre-operative radiochemotherapy of locally advanced rectal cancer

AIM: To evaluate results of pre-operative radiochemotherapy followed by surgery for 15 patients with locally advanced un-resectable rectal cancer.

METHODS: 15 patients with advanced non-resectable rectal cancer were treated with pre-operative irriadiation of 40-46 Gy plus concomitant chemotherapy (5-FU + LV and 5’-DFuR) (RCS group). For comparison, 27 similar patients, treated by preoperative radiotherapy (40-50 Gy) plus surgery were served as control (RS group).

RESULTS: No radiochemotherapy or radiotherapy was interrupted and then was delayed because of toxicities in both groups. The radical resectability rate was 73.3% in the RCS group and 37.0% (P = 0.024) in RS group. Sphincter preservation rates were 26.6% and 3.7% respectively (P = 0.028). Sphincter preservation rates of lower rectal cancer were 27.3% and 0.0% respectively (P = 0.014). Response rates of RCS and RS groups were 46.7% and 18.5% (P = 0.053). The tumor downstage rates were 8 (53.3%) and 9 (33.3%) in these groups (P = 0.206). The 3-year overall survival rates were 66.7% and 55.6% (P = 0.485), and the disease free survival rates were 40.1% and 33.2% (P = 0.663). The 3-year local recurrent rates were 26.7% and 48.1% (P = 0.174). No obvious late effects were found in either groups.

CONCLUSION: High resectability is possible following pre-operative radiochemotherapy and can have more sphincters preserved. It is important to improve the quality of the patients’ life even without increasing the survival or local control rates. Preoperative radiotherapy with concomitant full course chemotherapy (5-Fu + LV and 5’-DFuR) is effective and safe.

Comparison of therapeutic efficacy between tumor-derived heat shock protein 70 and interleukine-2

AIM

To compare and analyze the therapeutic effect of tumor-derived heat shock protein 70 and globally accepted interleukin-2, to evaluate the anti-tumor capacity of HSP70, and to provide significant information for HSP70 administration to treat human cancers.

METHODS

Cell Culture, techniques for protein extraction and purification, SDS-PAGE, Western-blot and animal experiment were used in this study.

RESULTS

Both IL-2 and HSP70 showed therapeutic effect in tumor-bearing mice. The best effect was observed in 100 000 U IL-2 and 10 μg HSP70 administrations, and partial efficacy was found in 50000 U IL-2 and 5 μg HSP70 administrations. The effect of 100000 U IL-2 was nearly as good as that of 5 μg HSP70. About 40 % mice receiving HSP70 10 μg administration survived over 90 days, the average survival period of this group was over 56.8 days, whereas the control group was 17.3 days, IL-2 50 000 group, 26.3 days, IL-2 100 000 group, 36.6 days, and 5 μg HSP70 group, 27.7 days. Significant difference was found (P<0.05) when compared with the HSP70 10 μg group and control group.

CONCLUSION

HSP70 has a specific anti-tumor effect and obviously exceeded IL-2 .Those data provide significant information for the treatment of human cancers.

Construction and expression of fusion gene of single chain Fv against human colorectal carcinoma

AIM: To explore the construction of the fusion gene of recombinant ND-1scFv against human colorectal carcinoma and yeast cytosine deaminase and the expression of the fusion protein in E. coli.

METHODS: Yeast cytosine deaminase gene was fused with the 3'terminus of gene of ND-1scFv against human colorectal carcinoma by a 18 bp linker with sequences encoding GSGGSG. To construct ND-1scFv-CD gene, plasmid pET 28 a(+)-ND-1scFv-CD was transformed into E. coli BL-21, and induced by IPTG to express the ND-1scFv-CD fusion protein. The expressed product was purified by affinity chromatography using NI-NTA resin, and its immunity was analyzed by ELISA. The cytotoxic activity of the ADEPT system containing ND-1 scFv-CD/5FC against human colon carcinoma cell line was evaluated by MTT assay.

RESULTS: Sequencing results showed that the ND-1scFv-CD gene consisted of 1 269 bp, including ND-1scFv 732 bp and CD 477 bp. SDS-PAGE analysis showed that the expected molecular weight of fusion protein was 47 Kd. Optical density scanning showed that fusion protein expressed in E. coli accounted to 27% of the total bacterial proteins. ELISA analysis revealed that ND-1scFv-CD reserved similar immunity of ND-1scFv. MTT assay showed scFv-CD/5FC was cytotoxic to human colorectal carcinoma cells.

CONCLUSION: ND-1scFv-CD gene against human colorectal carcinoma was constructed and expressed successfully in E. coli. The fusion protein exhibited good immunity and enzymatic activity.