Targeting ubiquitin-independent proteasome with small molecule increases susceptibility in pan-KRAS–mutant cancer models
Shihui Shen, … , Lei Li, Huaiyu Yang
Shihui Shen, … , Lei Li, Huaiyu Yang
Published March 17, 2025
Citation Information: J Clin Invest. 2025;135(6):e185278. https://doi.org/10.1172/JCI185278.
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Research Article Oncology

Targeting ubiquitin-independent proteasome with small molecule increases susceptibility in pan-KRAS–mutant cancer models

Abstract

Despite advances in the development of direct KRAS inhibitors, KRAS-mutant cancers continue to exhibit resistance to the currently available therapies. Here, we identified REGγ as a mutant KRAS–associated factor that enhanced REGγ transcription through the KRAS intermediate NRF2, suggesting that the REGγ-proteasome is a potential target for pan-KRAS inhibitor development. We elucidated a mechanism involving the KRAS/NRF2/REGγ regulatory axis, which links activated KRAS to the ATP- and ubiquitin-independent proteasome. We subsequently developed RLY01, a REGγ-proteasome inhibitor that effectively suppressed tumor growth in KRAS-mutant cancer models and lung cancer organoids. Notably, the combination of RLY01 and the KRASG12C inhibitor AMG510 exhibited enhanced antitumor efficacy in KRASG12C cancer cells. Collectively, our data support the hypothesis that KRAS mutations enhance the capacity of the REGγ-proteasome by increasing REGγ expression, highlighting the potential of ubiquitin-independent proteasome inhibition as a therapeutic approach for pan-KRAS–mutant cancers.

Authors

Shihui Shen, Qiansen Zhang, Yuhan Wang, Hui Chen, Shuangming Gong, Yun Liu, Conghao Gai, Hansen Chen, Enhao Zhu, Bo Yang, Lin Liu, Siyuan Cao, Mengting Zhao, Wenjie Ren, Mengjuan Li, Zhuoya Peng, Lu Zhang, Shaoying Zhang, Juwen Shen, Bianhong Zhang, Patrick K.H. Lee, Kun Li, Lei Li, Huaiyu Yang

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Figure 2

Pan-KRAS–mutant cells exhibit selective sensitivity to REGγ inhibition.

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Pan-KRAS–mutant cells exhibit selective sensitivity to REGγ inhibition. ...
(A) Relative cell viability of HCT8-KRASWT (left) or HCT8-KRASG13D (right) cells with or without REGγ knockdown. Relative cell viability was calculated by setting the values of the shN group (a negative control which was transfected a scramble shRNA) as 100%. Each value represents mean ± SEM (n = 3). *P < 0.05, ****P < 0.0001; P values were measured by 2-way ANOVA with Šidák’s multiple-comparison test. (B) REGγ depletion led to selective toxicity toward KRAS-mutant cancer cell lines. Nineteen KRAS-MUT and eleven KRAS-WT cancer cell lines were transfected with shREGγ or a scrambled shRNA. The percentage cell viability is relative to the untreated controls. Each value represents mean ± SEM (n = 3). **P < 0.01, ****P < 0.0001; P values were measured by 2-way ANOVA with Šidák’s multiple-comparison test. (C) Schematic illustration of the mouse protocol using xenografts derived from colorectal cell lines (HT29, HCT116). (D) Growth curves for HT29 and HCT116 xenografts with or without silencing of REGγ (n = 8). Values represent mean ± SEM. **P < 0.01, ****P < 0.0001; P values were measured by 2-way ANOVA with Tukey’s multiple-comparison test. (E) Representative colony formation images (left) and relative colony numbers (right) of KRAS-MUT cells with or without REGγ knockdown. (F and G) Ectopically expressed REGγ restored the clonogenic growth of REGγ-depleted cells. REGγOE, REGγ overexpression. The relative viability of cultured colonies in A549 (KRASG12S) and HCT116 (KRASG13D) cells is shown. The percentage cell viability is relative to the untreated controls. Each value represents mean ± SEM (n = 3). **P < 0.01, ***P < 0.001, ****P < 0.0001; P values were measured by 2-way ANOVA with Tukey’s multiple-comparison test.