Nanostring mRNA analysis indicated that combinatorial effects were the result of augmented interferon signaling and antigen processing, as well as of heightened leukocyte and dendritic cell functions.<br />Finally, the combination markedly improved antitumor efficacy in vivo compared to monotherapy treatment, with evidence of complete tumor clearance and prolongation of survival.<br />Based on these findings, we hypothesized that pharmacological activation of the cGASSTING pathway would further augment PARP inhibitorinduced inflammatory signaling and consequent antitumor immune responses.<br />We utilized the PARP inhibitor olaparib and the STING agonist ADUS, which has been shown to lead to potent antitumor immunity in multiple tumor models. <br />Combining olaparib with ADUS led to enhanced TBK and STING phosphorylation compared to that achieved by the monotherapies, demonstrating increased STING pathway activation.<br />We next examined whether activation of STING signaling resulted in the production of interferon and T cellattracting chemokines, such as CCL and CXCL.<br />Lowdose ADUS combined with olaparib significantly increased IFN mRNA levels in human MDAMB TNBC cells compared to single treatments, while the higher dose of ADUS did not appear to significantly enhance olaparibinduced IFN production. <br />The <a href="https://pubmed.ncbi.nlm.nih.gov/21453678/">Lucideric acid A</a> copyright holder for this preprint is the authorfunder.<br />In contrast to the combination therapy that led to a rapid induction of immune responses, olaparib monotherapyinduced T cell recruitment and activation was more evident at days. <br />Activated immune cell infiltration following ADUS and olaparib treatment was accompanied by type I IFN production, as evidenced by the significant increase in wholetumor IFN mRNA levels compared to single treatments. <br />These findings demonstrate that the addition of STING agonism to PARP inhibition elicits a superior immune response compared to either monotherapy alone, characterized by increased cytotoxic T cell recruitment and activation, and enhanced DC activation and antigen presentation.<br />Gene set analysis revealed that the topmost upregulated genes in response to the olaparibADUS combination were involved in antigen processing, MHC, interferon and leukocyte pathways. <br />In addition to the topmost upregulated gene sets superfamily gene signatures were highly upregulated in comparison to olaparib and ADUS alone. <br />Differential gene expression is shown by volcano plots. <br />Plotting of the normalized mRNA counts confirmed the significant increase in expression of genes in response to the olaparibADUS combination as compared to single treatments. <br />Among the top most significantly induced genes were the H class II histocompatibility antigen, A REFERENCES. <br />STING agonism enhances STING pathway activation and proinflammatory cytokine production in response to PARP inhibition in TNBC cells.<br />The combination of STING agonism with PARP inhibition upregulates the expression of genes involved in antigen processing, interferon <a href="https://www.targetmol.com/compound/Lucideric%20acid%20A">searchLucideric acid A</a> responses and leukocyte functions.<br />The scores measure the extent to which a gene set is up or downregulated relative to the covariate and they are calculated as the square root of the mean signed squared tstatistic for the genes in a gene set, with tstatistics coming from the linear regression underlying differential expression analysis.<br />Red denotes gene sets whose genes exhibit extensive overexpression with the covariate, blue denotes gene sets with extensive underexpression.<br />The copyright holder for this preprint is the authorfunder.<br />Weight of mice treated with vehicle, olaparib, ADUS or their combination long term.<br />The copyright holder for this preprint is the authorfunder.
