A recombinant adenovirus vector expressing human IFN-λ1 inhibits the growth of orthotopic gastric cancer and its possible mechanism
Objective To investigate the inhibitory effects of a recombinant adenovirus vector ex-pressing human IFN-λ1 （ r-Ad-hIFN-λ1） on the growth of orthotopic gastric cancer and to analyze its possi-ble mechanism in a nude mice model of orthotopic human gastric carcinoma .Methods Orthotopic trans-plantation was performed to establish the nude mice model of orthotopic gastric cancer .Thirty mice were ran-domly divided into three groups including PBS control group , Ad-Lac Z empty vector group and r-Ad-hIFN-λ1 experiment group .The mice in each group were given the corresponding interventions once a week for three times.The sizes of tumor were detected by using B-mode ultrasound at different time points to draw growth curves .The expression of IFN-λ1 at mRNA level in skeletal muscle tissues was analyzed by RT-PCR.Western blot assay and immunohistochemical staining were used to detect IFN-λ1 protein in gastric tumor samples .The apoptosis of cells in paraffin-embedded tumor tissues was detected by TUNEL .The per-centages of natural killer （ NK） cells in spleen tissues were analyzed by flow cytometry .Results Compared with control group and empty vector group , the mice in r-Ad-hIFN-λ1 experiment group showed the smallest tumor size [（331.25±6.00） mm3, （322.92±5.92） mm3 vs （248.39±7.60） mm3; P〈0.05].hIFN-λ1 was transfected into skeletal muscle successfully and expressed in gastric cancer tissue .Highly expressed hIFN-λ1 was observed in cytoplasm of tumor cells from experiment group by immunohistochemical staining . The apoptotic index of tumor tissues for experiment group was 0.700±0.059 which was significant different from that of control group （0.271±0.026, P〈0.05） and empty vector group （0.333±0.028, P〈0.05）. The percentage of NK cells in spleens from mice in experiment group [（26.49±1.89）%] was significantly higher than that of control group [（13.94 ±1.31）%, P〈0.05）] and empty vector group [（19.12 ±1.69）%, P〈0.05）].Conclusion Transfection of r-Ad-hIFN-λ1 and expression of hIFN-λin skeletal muscle could significantly inhibit the growth of gastric cancer by inducing tumor cells ′apoptosis and enhan-cing NK cells. 
 
Key words: 
IFN-λ1;  Recombination; Gastric cancer; Apoptosis; Immunization