Essential Role of Aldehyde Dehydrogenase 1A3 for the Maintenance of Non–Small Cell Lung Cancer Stem Cells Is Associated with the STAT3 Pathway

Abstract

Purpose Lung cancer stem cells (CSCs) with elevated aldehyde dehydrogenase (ALDH) activity are self-renewing, clonogenic and tumorigenic. The purpose of our study is to elucidate the mechanisms by which lung CSCs are regulated. Experimental Design A genome-wide gene expression analysis was performed to identify genes differentially expressed in the ALDH+ vs. ALDH− cells. RT-PCR, western blot and Aldefluor assay were used to validate identified genes. To explore the function in CSCs we manipulated their expression followed by colony and tumor formation assays. Results We identified a subset of genes that were differentially expressed in common in ALDH+ cells, among which ALDH1A3 was the most upregulated gene in ALDH+ vs. ALDH− cells. ShRNA-mediated knockdown of ALDH1A3 in NSCLCs resulted in a dramatic reduction in ALDH activity, clonogenicity and tumorigenicity, indicating that ALDH1A3 is required for tumorigenic properties. By contrast, overexpression of ALDH1A3 by itself it was not sufficient to increase tumorigenicity. The ALDH+ cells also expressed more activated Signal Transducers and Activators of Transcription 3 (STAT3) than ALDH− cells. Inhibition of STAT3 or its activator EZH2 genetically or pharmacologically diminished the level of ALDH+ cells and clonogenicity. Unexpectedly, ALDH1A3 was highly expressed in female, never smokers, well differentiated tumors, or adenocarcinoma. ALDH1A3 low expression was associated with poor overall survival. Conclusion Our data show that ALDH1A3 is the predominant ALDH isozyme responsible for ALDH activity and tumorigenicity in most NSCLCs, and that inhibiting either ALDH1A3 or the STAT3 pathway are potential therapeutic strategies to eliminate the ALDH+ subpopulation in NSCLCs.

ALDH1A3, the Major Aldehyde Dehydrogenase Isoform in Human Cholangiocarcinoma Cells, Affects Prognosis and Gemcitabine Resistance in Cholangiocarcinoma Patients

“…In addition, they also found that ALDH1B1 is dramatically upregulated in human colonic adenocarcinoma and therefore considering it as a potential biomarker for human colon cancer (23). Although high ALDH1A3 levels have already been detected in more aggressive forms of breast, bladder, and lung cancers (18,22,26), this work is nevertheless the first, to our knowledge, to report that ALDH1A3 is the main ALDH isoenzyme in intrahepatic cholangiocarcinoma. More importantly, we also found that ALDH1A3 is a critical prognostic factor in 77 patients with intrahepatic cholangiocarcinoma who received hepatectomies among several clinicopathologic features.…”

“…Elevated ALDH activity is also observed in leukemic SC populations in some acute myelogenous leukemia patients (13). ALDH1 serves as a marker of cancer SCs (CSC) in several types of solid tumors, including those of the liver (14), head and neck (15), pancreas (16), lung (17,18), prostate (19), bladder (20), ovary (21), breast (22), and colon (23). On the other hand, the potential of using increased ALDH activities to identify SC subpopulations in cholangiocarcinoma remains to be verified (24).…”

Autophagy Differentially Regulates Distinct Breast Cancer Stem-like Cells in Murine Models via EGFR/Stat3 and Tgfβ/Smad Signaling

“…We next investigated whether altered Stat3 signaling is responsible for the decreased tumorigenicity of ALDH + BCSCs upon deletion of FIP200, as both the BCSC properties and Aldh1a3 levels of ALDH + cells can be regulated by Stat3 signaling (33,34). In FIP200 cKO-MT cells, we observed decreased phospho Stat3 levels (Figure 5A), suggesting that FIP200 is required to sustain Stat3 signaling in PyMT cells.…”

Role of STAT3 in lung cancer

“…99 The CD133-or ALDH-positive cells isolated from NSCLC patient samples contain higher levels of the activated form of STAT3. 100 Treatment of these CD133-positive cells with a specific JAK-STAT inhibitor leads to a downregulation of their self-renewal capability as well as a lowering of their resistance to multiple cancer drugs. 100,101 The mechanism underlying STAT3 function in lung CSCs remains to be investigated.…”