Targeting the PLEKHA4-DDX3X axis reverses CDK4/6 inhibitor resistance in HR⁺/HER2⁻ breast cancer

@article{yujie2026targeting,
  title = {{Targeting the PLEKHA4-DDX3X axis reverses CDK4/6 inhibitor resistance in HR⁺/HER2⁻ breast cancer}},
  author = {ZHOU Yujie and DING Youpeng and LIU Cuicui and YU Keda},
  journal = {Zhongguo aizheng zazhi},
  year = {2026},
  month = sep,
  url = {http://www.china-oncology.com/zh/article/doi/10.19401/j.cnki.1007-3639.2026.09.003/},
  note = {CC BY-NC-ND},
}

TY  - JOUR
TI  - Targeting the PLEKHA4-DDX3X axis reverses CDK4/6 inhibitor resistance in HR⁺/HER2⁻ breast cancer
AU  - ZHOU Yujie
AU  - DING Youpeng
AU  - LIU Cuicui
AU  - YU Keda
PY  - 2026
DA  - 2026/09/01
JO  - Zhongguo aizheng zazhi
UR  - http://www.china-oncology.com/zh/article/doi/10.19401/j.cnki.1007-3639.2026.09.003/
AB  - MethodsA clinical cohort of 351 patients with treatment-naive HR⁺/HER2⁻ breast cancer enrolled between 2009 and 2016 was included, of whom 95 with complete transcriptomic data, endocrine therapy information, and follow-up data were included in the final analysis. Unsupervised consensus clustering was performed on transcriptomic data, and subtype stratification was combined with survival analysis and clinicopathological correlation analysis. In vitro, MCF-7 and T47D breast cancer cell lines with stable PLEKHA4 overexpression or knockdown were constructed. Cell counting kit-8 (CCK-8) assay, colony formation assay and flow cytometry cell cycle detection were applied to evaluate cellular sensitivity to abemaciclib and ribociclib. An orthotopic mammary fat pad xenograft model in female BALB/c nude mice was established, treated with abemaciclib to observe tumor growth, and immunohistochemistry was used to detect the expression of proliferation-related proteins. Immunoprecipitation-mass spectrometry, reciprocal co-immunoprecipitation, immunofluorescence co-localization, and Western blot were conducted to analyze the downstream interacting molecules regulated by PLEKHA4. Fresh surgical tumor specimens were collected to generate PDO, which was treated with gradient concentrations of CDK4/6 inhibitors to verify differential drug response. Immunofluorescence and tissue immunohistochemistry were performed to detect the expression levels of PLEKHA4 and DDX3X in resistant tumors.ResultsEndocrine-resistant patients were divided into two distinct molecular subtypes according to transcriptomic profiles. Subtype R1 was characterized by high-frequency PIK3CA mutations, while subtype R2 exhibited robust Wnt pathway activation with a low PIK3CA mutation rate of only 21%, accompanied by markedly upregulated PLEKHA4. There were no statistical differences in conventional clinicopathological indicators including age, tumor stage and Ki-67 proliferation index between the two subgroups, whereas relapse-free survival showed a significant discrepancy (P=0.001 1). In vitro experiments demonstrated that elevated PLEKHA4 significantly blunted cellular sensitivity to CDK4/6 inhibitors and accelerated G1-S cell cycle transition; PLEKHA4 knockdown restored drug cytotoxicity. In vivo xenograft models revealed that silencing PLEKHA4 markedly suppressed tumor proliferation and strengthened the anti-tumor efficacy of abemaciclib, accompanied by downregulation of pRb and Cyclin D1 expression along with the Ki-67 proliferation index. Mechanistic assays verified that PLEKHA4 directly bound to DDX3X in the cytoplasm and upregulated DDX3X protein abundance. Validation in PDO and paired primary tumor specimens showed significantly higher expression of PLEKHA4 and DDX3X in CDK4/6 inhibitor resistant samples, which could act as potential predictive biomarkers; Whether targeted inhibition of DDX3X can reverse drug resistance remains to be verified by further functional experiments.ConclusionThis study originally identified a novel Wnt-activated, low-frequency PI3K mutation molecular subtype of endocrine-resistant HR⁺/HER2⁻ breast cancer based on domestic clinical cohort data. For the first time, PLEKHA4 was confirmed that as the core driver conferring dual resistance to endocrine therapy and CDK4/6 inhibitors, and fully elucidated a brand-new mechanism in which the PLEKHA4-DDX3X axis induces therapeutic resistance via modulating cell cycle progression. PLEKHA4 can serve as a convenient clinical biomarker for therapeutic stratification, and the combination of DDX3X inhibitors and CDK4/6 inhibitors is a potential intervention direction worthy of subsequent exploration. This research improves the molecular classification system of drug-resistant HR⁺ breast cancer, and supplies theoretical support and translational evidence for precise individualized management of refractory breast tumors.Background and purposeHormone receptor-positive/human epidermal growth factor receptor 2-negative (HR⁺/HER2⁻) breast cancer accounts for 75% of all breast malignancies. Endocrine therapy combined with CDK4/6 inhibitors serves as the standard first-line regimen for advanced patients, yet intrinsic drug resistance greatly impairs clinical benefits. Previous studies on therapeutic resistance mainly focused on the PIK3CA-mutant subtype, while the molecular heterogeneity of endocrine resistance has not been systematically analyzed. The Wnt-activated resistant subtype and its core driver genes remain largely unreported, and the biological function of PLEKHA4 in breast cancer drug resistance is unclear. Based on a large domestic HR⁺ breast cancer clinical cohort, this study aims to define a novel molecular subtype of endocrine resistance, identify PLEKHA4 as the key gene mediating dual resistance to endocrine agents and CDK4/6 inhibitors, clarify the molecular mechanism regulated by the PLEKHA4-DDX3X signaling axis, validate predictive biomarkers via patient-derived organoid (PDO), and explore feasible combination strategies to reverse drug resistance.
SN  - 1007-3639
ER  -