Nuclear localized Akt enhances breast cancer stem-like cells through counter-regulation of p21^Waf1/Cip1 and p27^kip1

Cancer stem-like cells (CSCs) are a rare subpopulation of cancer cells capable of propagating the disease and causing cancer recurrence. In this study, we found that the cellular localization of PKB/Akt kinase affects the maintenance of CSCs. When Akt tagged with nuclear localization signal (Akt-NLS) was overexpressed in SKBR3 and MDA-MB468 cells, these cells showed a 10–15% increase in the number of cells with CSCs enhanced ALDH activity and demonstrated a CD44^+High/CD24^−Low phenotype. This effect was completely reversed in the presence of Akt-specific inhibitor, triciribine. Furthermore, cells overexpressing Akt or Akt-NLS were less likely to be in G0/G1 phase of the cell cycle by inactivating p21^Waf1/Cip1 and exhibited increased clonogenicity and proliferation as assayed by colony-forming assay (mammosphere formation). Thus, our data emphasize the importance the intracellular localization of Akt has on stemness in human breast cancer cells. It also indicates a new robust way for improving the enrichment and culture of CSCs for experimental purposes. Hence, it allows for the development of simpler protocols to study stemness, clonogenic potency, and screening of new chemotherapeutic agents that preferentially target cancer stem cells. Summary: The presented data, (i) shows new, stemness-promoting role of nuclear Akt/PKB kinase, (ii) it underlines the effects of nuclear Akt on cell cycle regulation, and finally (iii) it suggests new ways to study cancer stem-like cells.

癌症干细胞样细胞（Cancer stem-like cells, CSCs）是一类罕见的癌细胞亚群，具备驱动疾病进展与引发癌症复发的能力。本研究发现，蛋白激酶B/Akt激酶（PKB/Akt kinase）的细胞定位会影响CSCs的维持。当携带有核定位信号（nuclear localization signal, NLS）的Akt（即Akt-NLS）在SKBR3与MDA-MB468细胞中过表达时，这些细胞中具备干细胞样乙醛脱氢酶（ALDH）活性的细胞占比提升10%~15%，且呈现出CD44^高表达/CD24^低表达的表型。该效应可被Akt特异性抑制剂曲西立滨（triciribine）完全逆转。进一步研究发现，过表达Akt或Akt-NLS的细胞可通过灭活p21^Waf1/Cip1，减少其处于细胞周期G0/G1期的比例，同时集落形成实验（乳腺球形成实验）结果显示，这类细胞的克隆形成能力与增殖活性均有所增强。综上，本研究数据证实了Akt的细胞内定位对人乳腺癌细胞干细胞干性维持的重要性。该发现同时提供了一种可用于实验研究的、高效富集与培养CSCs的新方法，进而可助力开发更简便的实验方案，用于研究干细胞干性、克隆形成能力，以及筛选可特异性靶向癌症干细胞的新型化疗药物。研究总结如下：（1）揭示了核定位Akt/PKB激酶促进干细胞干性的全新功能；（2）阐明了核定位Akt对细胞周期调控的影响；（3）提出了研究癌症干细胞样细胞的新策略。

搜集汇总

背景与挑战

背景概述

该数据集聚焦于核定位Akt激酶在乳腺癌干细胞样细胞（CSCs）中的作用机制。研究发现，核Akt通过抑制p21和p27来增强CSCs的干细胞特性，如ALDH活性和克隆形成能力，这为乳腺癌研究和治疗提供了新见解。此外，数据强调了核Akt定位对细胞周期调控的影响，并提出了改进CSCs培养和实验方法的应用潜力。