Chment analysis (GSEA) working with Hallmark gene sets (Liberzon et al., 2015) to interrogate the pathways perturbed by Arid1a knockout. We observed that 25 gene sets were downregulated, and surprisingly, only two gene sets have been upregulated in AKC lesions (Figure 1C, Figure 1–figure supplement 4, and Supplementary file 1, false discovery rate (FDR) 0.1). It is actually worth noting that among the 27 gene sets two are particularly linked with Kras activation: KRAS_SIGNALING_UP (the gene set upregulated upon Kras activation) and KRAS_SIGNALING_DN (the gene set downregulated upon Kras activation). The gene set KRAS_SIGNALING_UP was downregulated even though the gene set KRAS_SIGNALING_DN was upregulated (Figure 1C and Figure 1–figure supplement 4). This observation suggests that the activities of Kras ATR Source signaling are partially impaired by Arid1a deficiency. In addition, we observed that the Tp53 signaling pathway was suppressed in AKC lesions (Figure 1D). It has been properly established that upregulation of the Tp53-related pathway is closely linked with apoptosis or senescence. ARID1A mutations have also been shown to be mutually exclusive with TP53 mutations in endometrial cancer (Wu et al., 2017). To establish no matter if Arid1a is involved inside the regulation of apoptosis, senescence, or each, we further examined the activity of associated pathways in Arid1a KO lesions. Interestingly, we identified that the senescence-associated signaling pathway is significantly suppressed in lesions from AKC mice (Figure 1E). In contrast, the pathway activity associated with apoptosis was not drastically changed (Figure 1–figure supplement 3B). These observations led us to hypothesize that Arid1a deficiency could market PanIN lesion progression via the attenuation of Kras-induced senescence. Moreover, senescent cells feature senescence-associated secretory phenotype (SASP), like higher levels of inflammatory cytokines and immune modulators. With all the attenuation of senescence promoted by Arid1a deficiency, we anticipated to observe lowered inflammatory response within the GSEA. Certainly, we observed that many signaling pathways associated with inflammation, which includes TNF signaling, IL6 TAT3 signaling, IL2 TAT5 signaling, IFN- signaling, and IFN- signaling, had been drastically suppressed in Arid1a KO lesions (Figure 1C, Figure 1–figure supplement four, and Supplementary file 1).In vivo, ex vivo, and in vitro verification with the attenuation of Krasinduced senescence by Arid1a deficiencyTo Cereblon site confirm the effect of Arid1a deficiency on Kras-induced senescence, we performed senescenceassociated beta-galactosidase (SA–Gal) staining on lesions from KC and AKC mice. SA–Gal-positive lesions had been observed in five out of seven (71 ) KC mice. In contrast, only one out of six (17 ) AKC mice showed SA–Gal-positive lesions. Amongst the mice with SA–Gal-positive lesions, the percentage of SA–Gal-positive lesions in KC mice was about twice of that in AKC mice (Figure 2A,B). These information confirmed that Arid1a knockout indeed lowered Kras-induced senescence. To additional confirm the effects of Arid1a knockout on senescence, we performed an ex vivo culture experiment using acinar cells isolated from AKC and KC mice. SA–Gal staining was performed to examine the senescence of acinar cells. As shown in Figure 2C,D, resulting from flat morphology of senescent cells along with the massive cell-size variation, we can’t accurately quantify the number of SA–Gal-negative cells. Instead of making use of the percentage of senescenc.