Study The Anti-tumor Effect Of PA-MSHA On Cetuximab Resistant Colorectal Cancer And The Related Mechanism

Cetuximab,the first FDA-approved antibody for CRC therapy,has been used in combination with standard chemotherapy in locally progressive and metastatic CRC.However,primary and acquired resistance remains a major clinical challenge.One of the recent studies found that a strain of Pseudomonas aeruginosa-mannose sensitive hemagglutinin(PA-MSHA),which with mannose-sensitive hemagglutinin fimbriae,has good anti-cancer properties in many cancers,such as breast,pancreatic,cervical cancer,etc.,but it is less studied in CRC.We found that PA-MSHA could effectively inhibit the migration and invasion of cetuximab-resistant CRC cells and induce apoptosis.Tumor-bearing experiments in nude mice showed that PA-MSHA inhibited tumor growth and increased survival time.These results suggest that PA-MSHA has strong anticancer activity against cetuximab-resistant CRC.To explore the underlying mechanisms,we performed massively parallel sequencing of cetuximab-resistant CRC cells with PA-MSHA treatment and with control vector.The data showed that miR-7-5p was significantly up-regulated after PA-MSHA treatment.In addition,overexpression of miR-7-5p enhanced the anticancer activity of PA-MSHA both in vitro and in vivo.Then,the target gene of miR-7-5p was matched to be Akt3 by bioinformatics analysis and was further confirmed with luciferase reporter assay,and silencing Akt3 could reverse the inhibitory effect of PA-MSHA caused by the inhibitory sequence of miR-7-5p,suggesting that Akt3 is the downstream molecule of miR-7-5p.Further bioinformatics analysis showed that Akt3 was positively correlated with the Wnt-β-catenin pathway.Our data showed that PA-MSHA could downregulate the expression of Akt3,β-catenin and Survivin,and upregulate the expression of E-cadherin.However,the inhibitory sequence of miR-7-5p led to upregulation of Akt3,β-catenin and Survivin,and downregulation of E-cadherin,thereby inhibiting the antitumor effect of PA-MSHA.When interfering with the expression of Akt3,the inhibitory effect disappeared.In conclusion,PA-MSHA downregulates the expression of Akt3 by upregulating miR-7-5p,subsequently inhibites the Wnt-β-catenin signaling pathway,consequently downregulates the expression of Survivin to increase apoptosis and upregulates the expression of E-cadherin to inhibit migration and invasion.Our data provide the theoretical basis for application of PA-MSHA in cetuximab-resistant CRC therapy.