Aldehyde dehydrogenase (ALDH) is a candidate marker for lung cancer cells with stem cell-like properties. Immunohistochemical staining of a large panel of primary non–small cell lung cancer (NSCLC) samples for ALDH1A1, ALDH3A1, and CD133 revealed a significant correlation between ALDH1A1 (but not ALDH3A1 or CD133) expression and poor prognosis in patients including those with stage I and N0 disease. Flow cytometric analysis of a panel of lung cancer cell lines and patient tumors revealed that most NSCLCs contain a subpopulation of cells with elevated ALDH activity, and that this activity is associated with ALDH1A1 expression. Isolated ALDH+ lung cancer cells were observed to be highly tumorigenic and clonogenic as well as capable of self-renewal compared with their ALDH− counterparts. Expression analysis of sorted cells revealed elevated Notch pathway transcript expression in ALDH+ cells. Suppression of the Notch pathway by treatment with either a γ-secretase inhibitor or stable expression of shRNA against NOTCH3 resulted in a significant decrease in ALDH+ lung cancer cells, commensurate with a reduction in tumor cell proliferation and clonogenicity. Taken together, these findings indicate that ALDH selects for a subpopulation of self-renewing NSCLC stem-like cells with increased tumorigenic potential, that NSCLCs harboring tumor cells with ALDH1A1 expression have inferior prognosis, and that ALDH1A1 and CD133 identify different tumor subpopulations. Therapeutic targeting of the Notch pathway reduces this ALDH+ component, implicating Notch signaling in lung cancer stem cell maintenance. Cancer Res; 70(23); 9937–48. ©2010 AACR .

https://cancerres.aacrjournals.org/content/canres/70/23/9937.full.pdf

Aldehyde dehydrogenase activity selects for lung adenocarcinoma stem cells dependent on Notch signaling

A role for cancer stem cells in therapy resistance: cellular and molecular mechanisms.

The majority of breast cancer deaths are because of ineffective treatment of metastatic disease. We previously identified a subpopulation of cells in human breast cancer cell lines that demonstrate high activity of aldehyde dehydrogenase (ALDH) and high expression of CD44. These ALDHhiCD44+ cells displayed enhanced metastatic behavior in vitro and in vivo relative to ALDHlowCD44− cells. The goal of this study was to test the hypothesis that ALDHhiCD44+ breast cancer cells are more resistant to standard cancer therapy, and that inhibiting ALDH activity through all-trans retinoic acid (ATRA) or the specific ALDH inhibitor diethylaminobenzaldehyde (DEAB) sensitizes these cells to treatment. ALDHhiCD44+ and ALDHlowCD44− populations were isolated from MDA-MB-231 and MDA-MB-468 cells lines and exposed to chemotherapy (doxorubicin/paclitaxel) or radiotherapy ± ATRA or DEAB. Cell populations were assessed for differences in survival, colony formation, and protein expression related to therapy resistance and differentiation. Significantly more ALDHhiCD44+ cells survived chemotherapy/radiotherapy relative to ALDHlowCD44− cells (P < 0.001). Glutathione-S-transferase pi, p-glycoprotein, and/or CHK1 were overexpressed in ALDHhiCD44+ populations compared with ALDHlowCD44− populations (P < 0.05). Pre-treatment of cell populations with DEAB or ATRA had no effect on ALDHlowCD44− cells, but resulted in significant initial sensitization of ALDHhiCD44+ cells to chemotherapy/radiotherapy. However, only DEAB had a long-term effect, resulting in reduced colony formation (P < 0.01). ATRA also significantly increased expression of CK8/18/19 in MDA-MB-468 ALDHhiCD44+ cells compared with control (P < 0.05). Our novel findings indicate that ALDHhiCD44+ breast cancer cells contribute to both chemotherapy and radiation resistance and suggest a much broader role for ALDH in treatment response than previously reported.

Inhibition of aldehyde dehydrogenase (ALDH) activity reduces chemotherapy and radiation resistance of stem-like ALDHhiCD44+ human breast cancer cells

Glioblastoma multiforme (GBM) cells are resistant to anticancer drugs. Cancer stem cells (CSCs) are a key mediator of chemoresistance. We have reported that disulfiram (DS), an aldehyde dehydrogenase (ALDH) inhibitor, targets breast CSC-like cells. In this study, the effect of DS and combination of DS and gemcitabine (dFdC) on GBM cells and GBM stem-like cells was investigated. 1-(4,5-Dimethylthiazol-2-yl)-3,5-diphenylformazan (MTT), combination index (CI)-isobologram, western blot, luciferase reporter gene assay, electrophoretic mobility-shift assay and ALDH analysis were used in this study. Disulfiram is cytotoxic in GBM cell lines in a copper (Cu)-dependent manner. Disulfiram/copper enhances the cytotoxicity of dFdC. Combination index-isobologram analysis indicates a synergistic effect between DS/Cu and dFdC. Disulfiram/copper induces reactive oxygen species (ROS), activates JNK and p38 pathways and inhibits nuclear factor-kappa B activity in GBM cell lines. Disulfiram/copper may trigger intrinsic apoptotic pathway via modulation of the Bcl2 family. Disulfiram/copper abolishes stem-like cell population in GBM cell lines. Our findings indicate that the cytotoxicity of DS/Cu and the enhancing effect of DS/Cu on the cytotoxicity of dFdC in GBM stem-like cells may be caused by induction of ROS and inhibition of both ALDH and the NFkB pathway. Both DS and dFdC can traverse the blood–brain barrier. Further study may lead them into GBM chemotherapy.

/pdf/cytotoxic-effect-of-disulfiram-copper-on-human-glioblastoma-3ozmmskor5.pdf

Cytotoxic effect of disulfiram/copper on human glioblastoma cell lines and ALDH-positive cancer-stem-like cells.

Aldehyde dehydrogenase 1 A1 (ALDH1A1) has recently been suggested as a marker for cancer stem or stem-like cancer cells of some human malignancies. The purpose of this study was to investigate the stem cell-related function and clinical significance of the ALDH1A1 in bladder urothelial cell carcinoma. Aldefluor assay was used to isolate ALDH1A1+ cells from bladder cancer cells. Stem cell characteristics of the ALDH1A1+ cells were then investigated by in vitro and in vivo approaches. Immunohistochemistry was done for evaluating ALDH1A1 expression on 22 normal bladder tissues and 216 bladder tumor specimens of different stage and grade. The ALDH1A1+ cancer cells displayed higher in vitro tumorigenicity compared with isogenic ALDH1A1- cells. The ALDH1A1+ cancer cells could generate xenograft tumors that resembled the histopathologic characteristics and heterogeneity of the parental cells. High ALDH1A1 expression was found in 26% (56 of 216) of human bladder tumor specimens and significantly related to advanced pathologic stage, high histologic grade, recurrence and progression, and metastasis of bladder urothelial cell carcinomas (all P < 0.05). Furthermore, ALDH1A1 expression was inversely associated with cancer-specific and overall survivals of the patients (P = 0.027 and 0.030, respectively). Therefore, ALDH1A1+ cell population could be enriched in tumor-initiating cells. ALDH1A1 may serve as a useful marker for monitoring the progression of bladder tumor and identifying bladder cancer patients with poor prognosis who might benefit from adjuvant and effective treatments.

https://cebp.aacrjournals.org/content/cebp/19/2/327.full.pdf

Aldehyde Dehydrogenase 1 A1–Positive Cell Population Is Enriched in Tumor-Initiating Cells and Associated with Progression of Bladder Cancer

Aldehyde dehydrogenase isozymes ALDH1A1 and ALDH3A1 are highly expressed in non small cell lung cancer. Neither the mechanisms nor the biologic significance for such over expression have been studied. We have employed oligonucleotide microarrays to analyze changes in gene profiles in A549 lung cancer cell line in which ALDH activity was reduced by up to 95% using lentiviral mediated expression of siRNA against both isozymes (Lenti 1+3). Stringent analysis methods were used to identify gene expression patterns that are specific to the knock down of ALDH activity and significantly different in comparison to wild type A549 cells (WT) or cells similarly transduced with green fluorescent protein (GFP) siRNA. We confirmed significant and specific down regulation of ALDH1A1 and ALDH3A1 in Lenti 1+3 cells and in comparison to 12 other ALDH genes detected. The results of the microarray analysis were validated by real time RT-PCR on RNA obtained from Lenti 1+3 or WT cells treated with ALDH activity inhibitors. Detailed functional analysis was performed on 101 genes that were significantly different (P < 0.001) and their expression changed by ≥ 2 folds in the Lenti 1+3 group versus the control groups. There were 75 down regulated and 26 up regulated genes. Protein binding, organ development, signal transduction, transcription, lipid metabolism, and cell migration and adhesion were among the most affected pathways. These molecular effects of the ALDH knock-down are associated with in vitro functional changes in the proliferation and motility of these cells and demonstrate the significance of ALDH enzymes in cell homeostasis with a potentially significant impact on the treatment of lung cancer.

/pdf/aldh-isozymes-downregulation-affects-cell-growth-cell-58wogx462j.pdf

Wayne Chou

Papers

ALDH isozymes downregulation affects cell growth, cell motility and gene expression in lung cancer cells.