Luminal Stem Cell Determinant SOX9 Controls Lineage Plasticity and Progression in Basal-Like Breast Cancer (Sox9-KO). Luminal Stem Cell Determinant SOX9 Controls Lineage Plasticity and Progression in Basal-Like Breast Cancer (Sox9-KO)

Lineage plasticity plays an important role in the development of basal-like breast cancer (BLBC), an aggressive cancer subtype. Although studies suggest BLBC is likely to originate from luminal progenitor cells, it acquires substantial basal cell features and contains a heterogenous collection of cells exhibiting basal, luminal and bipotent phenotypes. Why luminal progenitors are prone to BLBC transformation and what drives luminal-to-basal/bipotent reprogramming remains unclear. Here we show that the transcription factor SOX9 acts as a determinant for ER– luminal stem/progenitor cells (LSPCs). SOX9 controls LSPC activity in part by activating both canonical and non-canonical NF-B signaling. Inactivation of p53 and Rb in a BLBC mouse tumor model leads to upregulation of SOX9, which drives luminal-to-bipotent reprogramming in vivo. SOX9 deletion inhibits the progression of benign, neoplastic lesions to invasive carcinoma. Furthermore, SOX9 is overexpressed and correlated with shorter relapse-free survival in human BLBC. These data show that ER– LSPC determinant SOX9 acts as a lineage-specific driver for BLBC transformation. Overall design: Mammary glands from three Sox9Fl/Fl animals and thee MMTV-iCre; Sox9Fl/Fl animals, in diestrus, were reduced to a single cell suspension sperately. From the Sox9Fl/Fl animals ER-negative luminal cells (Lin-,EpcamHi,CD49fLo,Sca1-negative) were sorted into Trizol LS. From the MMTV-iCre;Sox9Fl/Fl animals the same gating scheme was used, with the addition of the cells being ECFP+, to sort Sox9-null ER-negative luminal cells into Trizol LS. The resulting RNA was analyzed for gene expression differences by microarray.

细胞谱系可塑性在侵袭性癌症亚型——基底样乳腺癌（basal-like breast cancer, BLBC）的发生发展中发挥关键作用。尽管已有研究提示BLBC可能起源于腔道祖细胞，但该肿瘤会获得大量基底细胞特征，且包含一群异质性细胞群体，分别呈现基底细胞、腔道细胞及双潜能细胞表型。目前尚不清楚为何腔道祖细胞易于发生BLBC转化，以及驱动腔道-基底/双潜能重编程的分子机制。本研究发现转录因子SOX9是雌激素受体阴性（ER–）腔道干/祖细胞（luminal stem/progenitor cells, LSPCs）的决定性调控因子。SOX9可通过激活经典型与非经典型核因子κB（NF-κB）信号通路，部分调控LSPC的活性。在BLBC小鼠肿瘤模型中，p53与Rb的失活会导致SOX9表达上调，进而在体内驱动腔道-双潜能细胞重编程。敲除SOX9可抑制良性肿瘤性病变向侵袭性癌的进展。此外，在人类BLBC样本中，SOX9呈过表达状态，且与更短的无复发生存期显著相关。上述研究结果表明，作为ER– LSPC决定性调控因子的SOX9，可作为谱系特异性驱动因子参与BLBC的转化进程。整体实验设计：选取处于动情间期的3只Sox9Fl/Fl小鼠及3只MMTV-iCre; Sox9Fl/Fl小鼠的乳腺组织，分别制备为单细胞悬液。从Sox9Fl/Fl小鼠中，通过分选获得雌激素受体阴性腔道细胞（Lin–、EpcamHi、CD49fLo、Sca1阴性）并加入Trizol LS试剂进行处理。对于MMTV-iCre;Sox9Fl/Fl小鼠，采用相同的门控策略，额外加入ECFP+标记以分选SOX9敲除的雌激素受体阴性腔道细胞，随后同样加入Trizol LS试剂处理。通过微阵列分析对提取的RNA进行基因表达差异检测。