SOX2 and PI3K Cooperate to Induce and Stabilize a Squamous-Committed Stem Cell Injury State during Lung Squamous Cell Carcinoma Pathogenesis

Bo Ram Kim, Emily Van de Laar, Michael Cabanero, Shintaro Tarumi, Stefan Hasenoeder, Dennis Wang, Carl Virtanen, Takaya Suzuki, Bizhan Bandarchi, Shingo Sakashita, Nhu An Pham, Sharon Lee, Shaf Keshavjee, Thomas K. Waddell, Ming Sound Tsao, Nadeem Moghal

研究成果: Article査読

29 被引用数 (Scopus)

抄録

Although cancers are considered stem cell diseases, mechanisms involving stem cell alterations are poorly understood. Squamous cell carcinoma (SQCC) is the second most common lung cancer, and its pathogenesis appears to hinge on changes in the stem cell behavior of basal cells in the bronchial airways. Basal cells are normally quiescent and differentiate into mucociliary epithelia. Smoking triggers a hyperproliferative response resulting in progressive premalignant epithelial changes ranging from squamous metaplasia to dysplasia. These changes can regress naturally, even with chronic smoking. However, for unknown reasons, dysplasias have higher progression rates than earlier stages. We used primary human tracheobronchial basal cells to investigate how copy number gains in SOX2 and PIK3CA at 3q26-28, which co-occur in dysplasia and are observed in 94% of SQCCs, may promote progression. We find that SOX2 cooperates with PI3K signaling, which is activated by smoking, to initiate the squamous injury response in basal cells. This response involves SOX9 repression, and, accordingly, SOX2 and PI3K signaling levels are high during dysplasia, while SOX9 is not expressed. By contrast, during regeneration of mucociliary epithelia, PI3K signaling is low and basal cells transiently enter a SOX2LoSOX9Histate, with SOX9 promoting proliferation and preventing squamous differentiation. Transient reduction in SOX2 is necessary for ciliogenesis, although SOX2 expression later rises and drives mucinous differentiation, as SOX9 levels decline. Frequent coamplification of SOX2 and PIK3CA in dysplasia may, thus, promote progression by locking basal cells in a SOX2HiSOX9Lostate with active PI3K signaling, which sustains the squamous injury response while precluding normal mucociliary differentiation. Surprisingly, we find that, although later in invasive carcinoma SOX9 is generally expressed at low levels, its expression is higher in a subset of SQCCs with less squamous identity and worse clinical outcome. We propose that early pathogenesis of most SQCCs involves stabilization of the squamous injury state in stem cells through copy number gains at 3q, with the pro-proliferative activity of SOX9 possibly being exploited in a subset of SQCCs in later stages.

本文言語English
論文番号e1002581
ジャーナルPLoS Biology
14
11
DOI
出版ステータスPublished - 2016 11月 23
外部発表はい

ASJC Scopus subject areas

  • 神経科学(全般)
  • 生化学、遺伝学、分子生物学(全般)
  • 免疫学および微生物学(全般)
  • 農業および生物科学(全般)

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