Li Mi, Lulla Amriti R, Wang Yan, Tsavaschidis Spyros, Wang Fuchenchu, Karakas Cansu, Nguyen Tuyen D T, Bui Tuyen N, Pina Marc A, Chen Mei-Kuang, Mastoraki Sofia, Multani Asha S, Fowlkes Natalie W, Sahin Aysegul, Marshall C Gary, Hunt Kelly K, Keyomarsi Khandan
Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Department of Medicine, Baylor College of Medicine, Houston, Texas.
Cancer Res. 2024 Nov 15;84(22):3864-3880. doi: 10.1158/0008-5472.CAN-23-4130.
Cyclin E is a regulatory subunit of CDK2 that mediates S phase entry and progression. The cleavage of full-length cyclin E (FL-cycE) to low-molecular weight isoforms (LMW-E) dramatically alters substrate specificity, promoting G1-S cell cycle transition and accelerating mitotic exit. Approximately 70% of triple-negative breast cancers (TNBC) express LMW-E, which correlates with poor prognosis. PKMYT1 also plays an important role in mitosis by inhibiting CDK1 to block premature mitotic entry, suggesting it could be a therapeutic target in TNBC expressing LMW-E. In this study, analysis of tumor samples of patients with TNBC revealed that coexpression of LMW-E and PKMYT1-catalyzed CDK1 phosphorylation predicted poor response to neoadjuvant chemotherapy. Compared with FL-cycE, LMW-E specifically upregulates PKMYT1 expression and protein stability, thereby increasing CDK1 phosphorylation. Inhibiting PKMYT1 with the selective inhibitor RP-6306 (lunresertib) elicited LMW-E-dependent antitumor effects, accelerating premature mitotic entry, inhibiting replication fork restart, and enhancing DNA damage, chromosomal breakage, apoptosis, and replication stress. Importantly, TNBC cell line xenografts expressing LMW-E showed greater sensitivity to RP-6306 than tumors with empty vector or FL-cycE. Furthermore, RP-6306 exerted tumor suppressive effects in LMW-E transgenic murine mammary tumors and patient-derived xenografts of LMW-E-high TNBC but not in the LMW-E null models examined in parallel. Lastly, transcriptomic and immune profiling demonstrated that RP-6306 treatment induced interferon responses and T-cell infiltration in the LMW-E-high tumor microenvironment, enhancing the antitumor immune response. These findings highlight the LMW-E/PKMYT1/CDK1 regulatory axis as a promising therapeutic target in TNBC, providing the rationale for further clinical development of PKMYT1 inhibitors in this aggressive breast cancer subtype. Significance: PKMYT1 upregulation and CDK1 phosphorylation in triple-negative breast cancer expressing low-molecular weight cyclin E leads to suboptimal responses to chemotherapy but sensitizes tumors to PKMYT1 inhibitors, proposing a personalized treatment strategy.
细胞周期蛋白E是细胞周期蛋白依赖性激酶2（CDK2）的调节亚基，介导S期进入和进程。全长细胞周期蛋白E（FL-cycE）裂解为低分子量异构体（LMW-E）会显著改变底物特异性，促进G1-S期细胞周期转换并加速有丝分裂退出。大约70%的三阴性乳腺癌（TNBC）表达LMW-E，这与预后不良相关。PKMYT1通过抑制CDK1以阻止过早进入有丝分裂，在有丝分裂中也起重要作用，提示它可能是表达LMW-E的TNBC的一个治疗靶点。在本研究中，对TNBC患者肿瘤样本的分析显示，LMW-E与PKMYT1催化的CDK1磷酸化共表达预示着对新辅助化疗反应不佳。与FL-cycE相比，LMW-E特异性上调PKMYT1表达和蛋白质稳定性，从而增加CDK1磷酸化。用选择性抑制剂RP-6306（伦瑞替尼）抑制PKMYT1可引发LMW-E依赖性抗肿瘤作用，加速过早有丝分裂进入，抑制复制叉重启，并增强DNA损伤、染色体断裂、细胞凋亡和复制应激。重要的是，表达LMW-E的TNBC细胞系异种移植瘤对RP-6306的敏感性高于空载体或FL-cycE肿瘤。此外，RP-6306在LMW-E转基因小鼠乳腺肿瘤和LMW-E高表达TNBC的患者来源异种移植瘤中发挥肿瘤抑制作用，但在同时检测的LMW-E缺失模型中未发挥作用。最后，转录组学和免疫分析表明，RP-6306治疗可在LMW-E高表达的肿瘤微环境中诱导干扰素反应和T细胞浸润，增强抗肿瘤免疫反应。这些发现突出了LMW-E/PKMYT1/CDK1调节轴作为TNBC中一个有前景的治疗靶点，为PKMYT1抑制剂在这种侵袭性乳腺癌亚型中的进一步临床开发提供了理论依据。意义：在表达低分子量细胞周期蛋白E的三阴性乳腺癌中，PKMYT1上调和CDK1磷酸化导致化疗反应欠佳，但使肿瘤对PKMYT1抑制剂敏感，提出了一种个性化治疗策略。
