Abstract B50: Regulation of non-small cell lung cancer stem cells by STAT3 and WNT pathways.

Abstract

Abstract Background: Accumulating evidence demonstrates that the malignant phenotype is driven and maintained by cancer stem cells (CSCs), which can self-renew, differentiate, and contribute to drug resistance and tumor metastasis. Our group has identified CSCs in both non-small cell lung cancer cell (NSCLC) lines and patient tumor samples by their enhanced ALDH activity and demonstrated that ALDH+ lung cancer cells are highly tumorigenic and clonogenic. We also found that ALDH1A3 is the major isozyme responsible for the ALDH activity and functionally important for lung CSCs. Aims and Methods: The purpose of our study is to elucidate the mechanisms by which lung CSCs are regulated. We performed a siRNA screen of 40 stem cell pathway genes in a panel of NSCLC lines to identify potential targets related to stem cell self-renewal pathways and other regulators. qRT-PCR, western blot and flow cytometry based Aldefluor assay were used to validate the promising hits. To further explore their biological function in lung CSCs we manipulated their expression genetically or pharmacologically followed by colony formation and tumor formation assays. Results: siRNA screen revealed that knocking down ALDH1A3, Signal Transducers and Activators of Transcription 3 (STAT3), or certain components of WNT and Notch pathway caused a reduction of cell viability in many NSCLC lines. Western blot analysis confirmed that ALDH+ cells contained more activated STAT3 compared to ALDH− lung cancer cells. Inhibition of STAT3 activation by Stattic (a specific STAT3 inhibitor), GSK126 (an EZH2 inhibitor), or siRNA attenuated ALDH1A3 expression, ALDH+ lung cancer cells and tumor cell clonogenicity. In addition, FZD2, DVL3 and LBH were more commonly upregulated in ALDH+ cells across the penal of NSCLC lines. shRNA mediated knockdown of DVL3 in NSCLCs resulted in a significant reduction in ALDH activity, clonogenicity, and tumorigenicity. Conclusions: Our data suggest that ALDH1A3 expression, STAT3 pathway activation (via EZH2), and an active WNT pathway are all essential for maintenance of lung CSCs. Blocking ALDH1A3, WNT or STAT3 pathways appear to be rationale therapeutic strategies for eliminating NSCLC stem cells. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B50. Citation Format: Chunli Shao, Chris DeSevo, Luc Girard, Paul Yenerall, Carmen Behrens, Ignacio Wistuba, John D. Minna. Regulation of non-small cell lung cancer stem cells by STAT3 and WNT pathways. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B50.