Abstract 2936: Ago2 induces Kras signaling and promotes tumor progression in mouse models of lung adenocarcinoma

Lung cancer is the deadliest malignancy in the United States. Non-small cell lung cancer (NSCLC) accounts for 85% of cases, and is frequently driven by activating mutations in the gene encoding the KRAS GTPase (e.g. KRASG12D). Our previous work demonstrated that Argonaute 2 (AGO2)—a component of the RNA induced silencing complex (RISC)—physically interacts with KRAS and stabilizes it at the protein level. In multiple cell lines, AGO2 knockdown reduces KRAS protein level and attenuates cell proliferation. We therefore hypothesized that AGO2 could promote KRASG12D-dependent NSCLC in vivo. To test the hypothesis, we evaluated the impact of Ago2 knockout in the KPC mouse model of NSCLC. In KPC mice, intratracheal delivery of adenoviral Cre drives lung-specific expression of a stop-floxed KRASG12D allele and biallelic ablation of p53. Simultaneous biallelic ablation of floxed Ago2 inhibited KPC lung nodule growth while reducing proliferative index and improving pathological grade. We next applied the KPHetC model, in which the clara cell-specific CCSP-driven Cre activates KRASG12D and ablates a single p53 allele. In these mice, Ago2 ablation also reduced tumor size and grade. In both models, Ago2 knockout inhibited ERK phosphorylation in tumor nodules, indicating impaired KRAS signaling. Furthermore, RNA-seq analysis of KPC nodules demonstrated broadly reduced expression of Kras-related genes. Taken together, our data demonstrate a novel pathogenic role for AGO2 in KRAS-dependent NSCLC. Given the prevalence of this malignancy and current difficulties in therapeutically targeting KRAS signaling, our work has future translational relevance.

Citation Format: Jean C. Tien, Seema Chugh, Andrew E. Goodrum, Yunhui Cheng, Lisha Wang, Rahul Mannan, Xiaoming Wang, Vijaya L. Dommeti, Yuping Zhang, Alice Xu, Fengyu Su, Xuhong Cao, Sunita Shankar, Arul M. Chinnaiyan. Ago2 induces Kras signaling and promotes tumor progression in mouse models of lung adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2936.

AGO2 promotes tumor progression in KRAS-driven mouse models of non-small cell lung cancer

Lung cancer is the deadliest malignancy in the United States. Non-small cell lung cancer (NSCLC) accounts for 85% of cases and is frequently driven by activating mutations in the gene encoding the KRAS GTPase (e.g., KRASG12D). Our previous work demonstrated that Argonaute 2 (AGO2)-a component of the RNA-induced silencing complex (RISC)-physically interacts with RAS and promotes its downstream signaling. We therefore hypothesized that AGO2 could promote KRASG12D-dependent NSCLC in vivo. To test the hypothesis, we evaluated the impact of Ago2 knockout in the KPC (LSL-KrasG12D/+;p53f/f;Cre) mouse model of NSCLC. In KPC mice, intratracheal delivery of adenoviral Cre drives lung-specific expression of a stop-floxed KRASG12D allele and biallelic ablation of p53 Simultaneous biallelic ablation of floxed Ago2 inhibited KPC lung nodule growth while reducing proliferative index and improving pathological grade. We next applied the KPHetC model, in which the Clara cell-specific CCSP-driven Cre activates KRASG12D and ablates a single p53 allele. In these mice, Ago2 ablation also reduced tumor size and grade. In both models, Ago2 knockout inhibited ERK phosphorylation (pERK) in tumor cells, indicating impaired KRAS signaling. RNA sequencing (RNA-seq) of KPC nodules and nodule-derived organoids demonstrated impaired canonical KRAS signaling with Ago2 ablation. Strikingly, accumulation of pERK in KPC organoids depended on physical interaction of AGO2 and KRAS. Taken together, our data demonstrate a pathogenic role for AGO2 in KRAS-dependent NSCLC. Given the prevalence of this malignancy and current difficulties in therapeutically targeting KRAS signaling, our work may have future translational relevance.

Abstract 5099: Evaluating Ago2 as an oncogene in Kras-dependent lung carcinoma

Background: Lung cancer is the deadliest malignancy in the United States. Non-small cell lung cancer (NSCLC) accounts for 85% of cases, and is frequently driven by activating mutations in the gene encoding the KRAS GTPase (e.g. KRASG12D). Our previous work demonstrated that Argonaute 2 (AGO2)—a component of the RNA induced silencing complex (RISC)—physically interacts with KRAS and stabilizes it at the protein level. In NSCLC cell lines, AGO2 knockdown reduces KRAS protein level and attenuates cell proliferation. We hypothesized that AGO2 acts as an oncogene in KRASG12D-dependent NSCLC in vivo.

Methods: To test the hypothesis, we generated a NSCLC model by intercrossing mice harboring a stop-floxed KRASG12D allele with animals containing a tamoxifen-responsive Cre recombinase gene driven by the (clara cell-specific) CCSP promoter. These animals, which frequently die within 10 weeks of tamoxifen treatment, display pulmonary lesions including hyperplasia, adenoma and frank adenocarcinoma. We evaluated whether concomitant ablation of one or both copies of (floxed) AGO2 influenced the NSCLC phenotype. After tamoxifen administration, we monitored mice daily and harvested tissues when mice were clinically moribund or reached 16 weeks of post-treatment. We harvested lungs for gross/ pathological examination and gene/ protein expression analysis.

Results: While pathologically discernable adenocarcinoma was detectable in AGO2+/+ and AGO2f/+ animals, AGO2f/f mice were free of these lesions. Despite this, deletion of AGO2 had no impact on frequency or extent of hyperplastic or adenomatous lesions. Immunohistochemistry demonstrated absence of AGO2 in tumor tissue of AGO2f/f mice.

Conclusion: AGO2 promotes progression but not initiation of cancerous lesions in a mouse model of KRASG12D-dependent NSCLC.

Citation Format: Andrew E. Goodrum, Lisha Wang, Alice Xu, Kristin M. Juckette, Arul M. Chinnaiyan, Jean C. Tien. Evaluating Ago2 as an oncogene in Kras-dependent lung carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5099.