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Its high incidence rate underscores the urgent need for a comprehensive understanding of its underlying mechanisms and the development of effective therapeutic strategies. Breast cancer is a heterogeneous disease, characterized by diverse molecular subtypes that exhibit distinct biological behaviors, clinical features, and treatment responses. These subtypes are primarily classified based on the expression of hormone receptors, such as estrogen receptor (ER) and progesterone receptor (PR), as well as the human epidermal growth factor receptor 2 (HER2). Hormone - receptor - positive breast cancers, which express either ER or PR or both, constitute the majority of cases. These tumors are often driven by hormonal signaling pathways and are typically treated with endocrine therapies that target the estrogen signaling axis, such as tamoxifen and aromatase inhibitors [9]. HER2 - positive breast cancers, on the other hand, overexpress the HER2 protein and are associated with a more aggressive clinical course. Targeted therapies against HER2, such as trastuzumab, have significantly improved the prognosis of patients with this subtype [9]. Triple - negative breast cancer (TNBC), which lacks expression of ER, PR, and HER2, is known for its high aggressiveness and limited treatment options, often relying on chemotherapy as the mainstay of treatment [9]. 2. The Role of Cyclin - Dependent Kinases in Breast Cancer Cyclin - dependent kinases (CDKs) are a family of serine/threonine kinases that play crucial roles in regulating the cell cycle progression. In the context of breast cancer, dysregulation of CDK activity is a common feature and contributes to uncontrolled cell proliferation, a hallmark of cancer. CDK4 and CDK6, in particular, are key regulators of the G1 - S phase transition of the cell cycle. They form complexes with cyclin D and phosphorylate the retinoblastoma protein (Rb), leading to the release of transcription factors such as E2F, which then activate genes required for DNA synthesis and cell cycle progression [8]. In hormone - receptor - positive breast cancer, the cyclin D - CDK4/6 - Rb pathway is often hyperactivated. Cyclin D1 is an estrogen - responsive gene, and its overexpression is frequently observed in ER - positive breast tumors. This hyperactivation of the CDK4/6 pathway promotes cell cycle progression and tumor growth, making it an attractive therapeutic target [6]. As a result, CDK4/6 inhibitors have emerged as a new class of targeted therapies for hormone - receptor - positive breast cancer. 3. Ribociclib: A CDK4/6 Inhibitor in Breast Cancer Treatment Ribociclib is a selective oral CDK4/6 inhibitor that has shown promising results in the treatment of hormone - receptor - positive, HER2 - negative advanced breast cancer. By inhibiting CDK4/6 activity, ribociclib blocks the phosphorylation of Rb, thereby preventing the release of E2F and arresting the cell cycle in the G1 phase. This leads to inhibition of tumor cell proliferation and growth [6]. Clinical trials have demonstrated that the combination of ribociclib with endocrine therapies, such as letrozole or fulvestrant, significantly improves progression - free survival (PFS) compared to endocrine therapy alone in patients with advanced hormone - receptor - positive breast cancer [17]. These results have led to the approval of ribociclib by regulatory agencies for the treatment of this patient population, providing a new and effective treatment option. However, despite the initial success of ribociclib, the development of resistance remains a major challenge in the long - term management of breast cancer patients. Understanding the mechanisms underlying ribociclib resistance is crucial for the development of strategies to overcome it and improve patient outcomes. 4. The LAP2 - Emerin - MAN1 (LEM) Domain Family and LEM4 The LAP2 - Emerin - MAN1 (LEM) domain family is a group of inner nuclear membrane proteins that play important roles in nuclear structure, chromatin organization, and gene regulation. These proteins share a conserved LEM domain, which mediates their interaction with chromatin - associated proteins such as Barrier - to - Autointegration Factor (BAF) [3]. LEM4, also known as NET29, is a member of the LEM domain family. It is located at the inner nuclear membrane and has been implicated in various cellular processes, including cell cycle regulation, DNA damage response, and gene expression modulation [3]. Previous studies have shown that LEM4 can interact with several proteins involved in cell cycle control, such as CDK1 and cyclin B1, and regulate their activity. This suggests that LEM4 may play a role in cell cycle progression and tumor development [3]. In the context of breast cancer, the expression and function of LEM4 have not been extensively studied. However, emerging evidence suggests that LEM4 may be involved in the regulation of signaling pathways that are relevant to breast cancer progression and treatment resistance. For example, some studies have indicated that LEM4 can interact with components of the Wnt\/beta - catenin signaling pathway, which is known to be dysregulated in various cancers, including breast cancer [8]. 5. The Wnt/beta - Catenin Signaling Pathway and Its Role in Breast Cancer The Wnt\/beta - catenin signaling pathway is a highly conserved signaling cascade that plays critical roles in embryonic development, tissue homeostasis, and cancer. In the absence of Wnt ligands, beta - catenin is sequestered in a cytoplasmic complex consisting of axin, adenomatous polyposis coli (APC), glycogen synthase kinase - 3beta (GSK - 3beta), and casein kinase 1 (CK1). This complex promotes the phosphorylation and ubiquitination of beta - catenin, leading to its proteasomal degradation [3]. When Wnt ligands bind to their cell surface receptors, Frizzled and low - density lipoprotein receptor - related protein 5\/6 (LRP5\/6), the cytoplasmic complex is disrupted, and beta - catenin is stabilized. Stabilized beta - catenin then translocates into the nucleus, where it forms a complex with transcription factors such as T - cell factor/lymphoid enhancer factor (TCF\/LEF) and activates the transcription of target genes involved in cell proliferation, survival, and differentiation [6]. In breast cancer, dysregulation of the Wnt\/beta - catenin signaling pathway has been frequently observed. Aberrant activation of this pathway can contribute to tumor initiation, progression, and metastasis. For example, overexpression of Wnt ligands, mutations in components of the degradation complex (such as APC or beta - catenin itself), or activation of downstream signaling molecules can lead to constitutive activation of beta - catenin - dependent transcription and promote breast cancer development [8]. Moreover, the Wnt/beta - catenin pathway has been implicated in the regulation of cancer stem cells, which are thought to be responsible for tumor recurrence and treatment resistance [8]. 6. The Potential Link between LEM4, beta - Catenin, and Ribociclib Resistance Given the roles of LEM4 in cell cycle regulation and its potential interaction with the Wnt/beta - catenin signaling pathway, as well as the importance of the Wnt/beta - catenin pathway in breast cancer and treatment resistance, it is reasonable to hypothesize that LEM4 may be involved in the development of ribociclib resistance in breast cancer cells through its interaction with beta - catenin. Previous studies have shown that the Wnt\/beta - catenin pathway can cross - talk with other signaling pathways involved in cell cycle regulation, such as the CDK4/6 - Rb pathway. For example, beta - catenin can directly or indirectly regulate the expression of cyclin D1, a key component of the CDK4/6 - Rb pathway [8]. This suggests that activation of the Wnt\/beta - catenin pathway may bypass the inhibitory effects of CDK4/6 inhibitors, leading to the development of resistance. If LEM4 can promote beta - catenin - dependent transcription activity, it may enhance the expression of genes involved in cell cycle progression and survival, thereby counteracting the cell cycle arrest induced by ribociclib. This would provide a mechanism for breast cancer cells to escape the growth - inhibitory effects of ribociclib and develop resistance. Therefore, the LEM4/beta - catenin axis represents a potential therapeutic strategy to overcome ribociclib resistance in breast cancer cells. Breast cancer is a complex and heterogeneous disease with diverse molecular subtypes. The CDK4\/6 inhibitor ribociclib has shown significant efficacy in the treatment of hormone - receptor - positive breast cancer, but the development of resistance remains a major challenge. LEM4, a member of the LEM domain family, has the potential to interact with the Wnt/beta - catenin signaling pathway, which is dysregulated in breast cancer and implicated in treatment resistance. Understanding the role of the LEM4/beta - catenin axis in ribociclib resistance may provide new insights into the mechanisms of resistance and lead to the development of novel therapeutic strategies to overcome it, ultimately improving the prognosis of breast cancer patients. References [3] Nasiri Kenari F, Saberian M, Abikenari M, Najafi S, Sadeghizadeh M Restoring Tamoxifen Sensitivity in Breast Cancer: The Role of lncRNA MALAT1 and NanoCurcumin as Modulators of Drug Resistance. BioMed Research International. 2025. 2025. 5824748. PMID: 41031251. DOI: 10.1155/bmri/5824748. ƪ·ùÔ­Òò£¬Ê¡ÂÔÆäËü²Î¿¼ÎÄÏ×...... ÒÔÉÏÕâƪIntroductionÆð²Ýʱ¼ä½ö00:02:53 ÈçÐèÊÔÓá¾ÉîÈÝSCIд×÷ÖÇÄÜÌå¡¿£¬Çë΢ÐÅÁªÏµÉîÈÝÕÅÀÏʦ£ºshenrongagent [https://scioriginal.com] #SCIÂÛÎÄ #¿ÆÑÐ #ʵÑé  #²©Ê¿ #Ͷ¸å ¸ü¶àÍƼö£º [MethodÖÇÄÜÌå]£º3·ÖÖÓÆð²ÝSCIÂÛÎÄMethod£¬²¢ÒýÓÃÕæʵ²Î¿¼ÎÄÏ×£¿

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