Development of double strand RNA mPEI nanoparticles and application in treating invasive breast cancer

The immunostimulant effects of the rice ragged stunt virus genome on the growth and metastasis of breast cancer in mouse model

There are multiple treatment strategies that have been reported for breast cancer, while new and effective therapies against it are still necessary. Stimulating the immune system and its components against cancer cells is one of the unique treatment strategies of immunotherapy and long dsRNAs are immunostimulant in this regard. Based on bioinformatics approaches, a fragment of the Rice ragged stunt RNA virus genome was selected and synthesized according to its immunogenicity. Based on the in vitro transcription technique, dsRNA was synthesized and its binding ability to the PEI/PEI-Ac Polyethylenimine (PEI) or Acetylated polyethylenimine (PEI-Ac) was verified by the gel retardation assay. Then, the PEI-Ac was synthesized by adding acetyl groups to the PEI, and the results of the 1H NMR method indicated its successful synthesis. After cancer induction by 4 T1 cells in Balb/C mice, intraperitoneal (IP) and intratumoral (IT) treatment by the PEI/PEI-Ac-dsRNA were performed and the tumor growth inhibition was evaluated. Results demonstrated that PEI/PEI-Ac-dsRNA can lead to a decrease in tumor weight and volume in both the IP and IT routes. Also, by using macro-metastatic nodule counting and hematoxylin and eosin (H&E) staining we showed that PEI/PEI-Ac-dsRNA can prevent micro and macro-metastasis in the lung. Therefore, the PEI/PEI-Ac-dsRNA acts as an effective inhibitor of growth and metastasis of the breast cancer models. We showed that viral dsRNA can exert its antitumor properties by stimulating TNF-α and IFN-γ. In general, our results revealed that dsRNA derived from the plant virus genome stimulates the intrinsic immune system and can be a potential immune stimulant drug for cancer treatment.

PD-L1 silencing inhibits triple-negative breast cancer development and upregulates T-cell-induced pro-inflammatory cytokines

Triple-negative breast cancer (TNBC) is an invasive tumor with a high incidence of distant metastasis and poor prognosis. In TNBC cells, high PD-L1 expression can induce an immunosuppressive tumor microenvironment, repressing the anti-tumoral immune responses. Although FDA-approved agents targeting the PD-1/PD-L1 axis are potent to eliminate tumoral cells, their immune-related adverse events have become worrisome. As the regulator of gene expression, siRNAs can directly target PD-L1 in breast cancer cells. The gene modification of tumoral PD-L1 can reduce our reliance on the current method of targeting the PD-L1/PD-1 axis. We initiated the study with bioinformatics analysis; the results indicated that TNBC and the MDA-MB-231 cells significantly overexpressed PD-L1 compared to other breast cancer subtypes and cell lines. Our results demonstrated that PD-L1 silencing substantially reduced PD-L1 expression at mRNA and protein levels in MDA-MB-231 cells. Moreover, our results demonstrated that PD-L1 knockdown reduced cancer cell proliferation and induced apoptosis via intrinsic and extrinsic apoptosis pathways. We observed that PD-L1 silencing effectively inhibited the migration of TNBC cells. Further investigation also displayed that silencing of PD-L1 in breast cancer cells induced T-cell cytotoxic function by upregulating the gene expression of pro-inflammatory cytokines, i.e., IL-2, IFN-γ, and TNF-α, and downregulating the gene expression of anti-inflammatory cytokines, i.e., IL-10, and TGF-β, in a co-culture system.