Amplification and functional characterization of MUC1 promoter and gene-virotherapy via a targeting adenoviral vector expressing hSSTR2 gene in MUC1-positive Panc-1 pancreatic cancer cells in vitro.

Mucin1 (MUC1) promoter has been cloned from the 5' flanking region of the MUC1 gene in breast carcinoma, functionally characterized and applied in gene therapy of breast and esophageal carcinoma. In the present study, we amplified a 786 base pair (bp) MUC1 promoter by two-step nest PCR, and identified the activity and tumor-specificity using an enhanced green fluorescent protein (EGFP) gene as a reporter gene by fluorescence microscopy and flow cytometry analysis in Panc-1, primary normal pancreatic (PNPC), and cervical cancer HeLa cell lines. Subsequently, the human somatostatin receptor subtype 2 (hSSTR2) gene driven by MUC1 promoter was cloned into the pAdTrack to produce recombinant adenovirus AdMUC1-hSSTR2. The anticancer effect of AdMUC1-hSSTR2 was determined in Panc-1. The results demonstrated that there was no AdMUC1-hSSTR2-induced apoptosis, but a significant cell proliferation inhibition even without somatostatin (SST) analogue Octreotide, involved in the up-regulation of the cyclin-dependent kinase (CDK) inhibitors p21 and p27. Moreover, the anticancer effect could not be augmented by the addition of Octreotide, revealing a mechanism that was independent from induction of Octreotide. Therefore, this adenovirus system can be used as a novel, potent and specific tool for gene-targeting therapy in the MUC1 positive pancreatic carcinoma as shown in Panc-1.

Reversal of the phenotype by K-rasval12 silencing mediated by adenovirus-delivered siRNA in human pancreatic cancer cell line Panc-1.

AIM: To investigate the in vitro antitumor effect of adenovirus-mediated small interfering RNAs (siRNAs) on pancreatic cancer and the associated mechanism. METHODS: A 63-nucleotide (nt) oligonucleotide encoding K-ras(val12) and specific siRNA were introduced into pSilencer 3.1-H1, then the H1-RNA promoter and siRNA coding insert were subcloned into pAdTrack to get plasmid pAdTrackH1-K-ras(val12). After homologous recombination in bacteria and transfections of such plasmids into a mammalian packaging cell line 293, siRNA expressing adenovirus AdH1-K-ras(val12) was obtained. Stable suppression of K-ras(val12) was detected by Northern blot and Western blot. Apoptosis in Panc-1 cells was detected by flow cytometry. RESULTS: We obtained adenovirus AdH1-K-ras(val12) carrying the pSilencer 3.1-H1 cassette, which could mediate gene silencing. Through siRNA targeted K-ras(val12), the oncogenic phenotype of cancer cells was reversed. Flow cytometry showed that apoptotic index of Panc-1 cells was significantly higher in the AdH1-K-ras(val12)-treatment group (18.70% at 72 h post-infection, 49.55% at 96 h post-infection) compared to the control groups (3.47%, 3.98% at 72 and 96 h post-infection of AdH1-empty, respectively; 4.21%, 3.78% at 72 and 96 h post-infection of AdH1-p53, respectively) (P<0.05). CONCLUSION: These results demonstrate that adenoviral vectors can be used to mediate RNA interference (RNAi) to induce persistent loss of functional phenotypes. In gene therapy, the selective down-regulation of only the mutant version of a gene allows for highly specific effects on tumor cells, while leaving the normal cells untouched. In addition, the apoptosis of pancreatic cancer cell line Panc-1 can be induced after AdH1-K-ras(val12) infection. This kind of adenovirus based on RNAi might be a promising vector for cancer therapy.