PD-1-siRNA Delivered by Attenuated Salmonella Enhances the Antitumor Effect of Chloroquine in Colon Cancer

Abstract

The widespread appearance of drug tolerance and the low efficiency of single treatment have severely affected the survival time of the patients with colorectal cancer. Exploring new treatment options and combined treatment strategies have become the key to improving the prognosis. The combination of immunotherapy and chemotherapy have shown good clinical expectations. Here, we studied the cooperative effects of chloroquine, an anti-malarial drug that is now widely used in anti-tumor research, and RNA interference (RNAi) targeting the immune checkpoint molecule Programmed Death-1 (PD-1) delivered with attenuated Salmonella. Our results show that chloroquine can not only significantly inhibit the survival of colon cancer cells and induce apoptosis, but also effectively inhibit cell invasion and migration. The results of in vivo experiments show that chloroquine can increase the expression of PD-1 in tumor tissues. Combining chloroquine and PD-1 siRNA can further inhibit the growth and metastases of colon cancer and induce apoptosis. The mechanism underlying this phenomenon is the occurrence of chloroquine-induced apoptosis and the effective immune response caused by the attenuated Salmonella carrying PD-1 siRNA. This study suggests that the combined application of PD-1-based immunotherapy and anti-cancer drugs has become a new expectation for clinical treatment of colorectal cancer.

FMR1 promotes the progression of colorectal cancer cell by stabilizing EGFR mRNA in an m6A-dependent manner

“…Three FMR1-specific hairpin RNA (Supplementary Data Table S3 ) were designed, annealed and ligated into the linearized vector of pGCsilencerU6/Neo, as described previously [ 23 , 24 ]. The attenuated S. typhimurium phoP/phoQ-null strain LH430 was obtained from S. typhimurium strain SL1344 by deletion of the attenuated S. typhimurium phoP/phoQ null strain LH430 locus.…”

“…Anti-tumor effect of FMR1 shRNA carried by attenuated Salmonella in vivo On the basis of the above results, we used our RNA interference drug platform to further explore the therapeutic application of FMR1. We designed three FMR1 shRNA sequences and inserted them into the pSilencer plasmid, as described above [24] (Fig. 7a).…”

Potential Application of Small Interfering RNA in Gastro-Intestinal Tumors

“…Thus, the interaction PD-1/PD-L1 is responsible for the occurrence of the immune escape of tumor cells. Recently, Lu et al [ 96 ] explored the targeting of PD-1 by a specific siRNA delivered via attenuated Salmonella. This is a rather original delivery system where a plasmid, coding for the sequence of the siRNA of interest, is employed to transform attenuated Salmonella, which is used as an expression carrier for the siRNA.…”

FMR1 promotes the progression of colorectal cancer cell by stabilizing EGFR mRNA in an m6A-dependent manner

“…Three FMR1-speci c hairpin RNA (Supplementary Data Table S3) were designed, annealed and ligated into the linearized vector of pGCsilencerU6/Neo, as described previously [23,24]. The attenuated S. typhimurium phoP/phoQ-null strain LH430 was obtained from S. typhimurium strain SL1344 by deletion of the attenuated S. typhimurium phoP/phoQ null strain LH430 locus.…”

“…On the basis of the above results, we used our RNA interference drug platform to further explore the therapeutic application of FMR1. We designed three FMR1 siRNA sequences and inserted them into the pSilencer plasmid, as described above [24] (Fig. 7a).…”