Aldehyde Dehydrogenase Isoform 1 Research Articles

Sulforaphane has an additive anticancer effect to FOLFOX in highly metastatic human colon carcinoma cells.

Colorectal cancer (CRC) is one of the most common malignancies worldwide. Patients with CRC may need chemotherapy (CTx) in a neoadjuvant, adjuvant or palliative setting through the course of the disease. Unfortunately, its effect is limited by chemoresistance and chemotoxicity. Novel more effective and non‑toxic CTx regimens are needed to further improve CRC treatment outcomes. Thus, the present study was designed to test the hypothesis that non‑toxic sulforaphane (SF) is effective against CRC and has additive effects in combination with conventional 5‑fluorouracil, oxaliplatin and folinic acid (FOLFOX) CTx invitro. Highly metastatic human colon cancer cells, CX‑1, and fibroblasts were treated with FOLFOX ± SF. Cell viability was assessed using an MTT assay. The level of apoptosis and the expression of apoptotic proteins were measured by TUNEL assay and quantitative PCR analysis. Aldehyde dehydrogenase isoform 1 (ALDH1) and multidrug resistance protein 2 (MRP2) levels were evaluated. The ability of cells to form spheroids was measured in three‑dimensional cell culture. SF alone and in combination with FOLFOX effectively decreased the viability of the CX‑1 cells, promoted apoptosis within the CX‑1 cells, prevented cellular spheroid formation and decreased ALDH1 activity. However, SF promoted MRP2 expression and protein levels. In conclusion, SF together with conventional FOLFOX has additive anticancer effects against highly metastatic human CRC invitro.

Aldehyde Dehydrogenase Isoform 1 Predicts a Poor Prognosis of Acute Cerebral Infarction.

To investigate the prognostic potential of serum aldehyde dehydrogenase isoform 1 (ALDH1) level in acute cerebral infarction, and the molecular mechanism in mediating neurological deficits, a total of 120 acute cerebral infarction cases within 72 h of onset were retrospectively analyzed. Serum ALDH1 level in them was detected by qRT-PCR. Receiver operating characteristic (ROC) and Kaplan–Meier curves were depicted for assessing the diagnostic and prognostic potentials of ALDH1 in acute cerebral infarction, respectively. An in vivo acute cerebral infarction model in rats was established by performing MCAO, followed by evaluation of neurological deficits using mNSS and detection of relative levels of ALDH1, Smad2, Smad4, and p21 in rat brain tissues. Pearson's correlation test was carried out to verify the correlation between ALDH1 and mNSS and relative levels of Smad2, Smad4, and p21. Serum ALDH1 level increased in acute cerebral infarction patients. A high level of ALDH1 predicted a poor prognosis of acute cerebral infarction patients. In addition, ALDH1 was sensitive and specific in distinguishing acute cerebral infarction cases, presenting a certain diagnostic potential. mNSS was remarkably higher in acute cerebral infarction rats than that of controls. Compared with sham operation group, relative levels of ALDH1, Smad2, and Smad4 were higher in brain tissues of modeling rats, whilst p21 level was lower. ALDH1 level in brain tissues of modeling rats was positively correlated to mNSS, and mRNA levels of Smad2 and Smad4, but negatively correlated to p21 level. Serum ALDH1 level is a promising prognostic and diagnostic factor of acute cerebral infarction, which is correlated to 90-day mortality. Increased level of ALDH1 in the brain of cerebral infarction rats is closely linked to neurological function, which is associated with the small mothers against decapentaplegic (Smad) signaling and p21.

ITGA7, CD133, ALDH1 are inter-correlated, and linked with poor differentiation, lymph node metastasis as well as worse survival in surgical cervical cancer.

AimIntegrin alpha 7 (ITGA7) regulates cancer stemness and metastasis in several malignancies, while its role in cervical cancer is obscure. Therefore, the current study aimed to investigate the correlation among ITGA7, cluster of differentiation 133 (CD133), and aldehyde dehydrogenase isoform 1 (ALDH1), as well as their relation to tumor features and survival in cervical cancer patients.MethodsA total of 133 surgical cervical cancer patients were enrolled. Tumor ITGA7, CD133, and ALDH1 expressions were determined by immunohistochemistry (IHC). Furthermore, the clinicopathological features, disease‐free survival (DFS), and overall survival (OS) were collected.ResultsITGA7 expression positively related to CD133 expression (p = 0.040) and ALDH1 expression (p < 0.001). Besides, ITGA7 (p = 0.001), CD133 (p = 0.016), and ALDH1 (p = 0.009) high expressions linked with poor tumor differentiation; meanwhile, ITGA7 (p = 0.010) and ALDH1 (p = 0.004) high expressions correlated with more prevalence of lymph node metastasis. However, ITGA7, CD133, or ALDH1 expression was not associated with other clinicopathological features. Inspiringly, it was worth noting that ITGA7 (p = 0.009), CD133 (p = 0.041), and ALDH1 (p = 0.035) high expressions predicted unfavorable DFS; meanwhile, both ITGA7 (p = 0.021) and ALDH1 (p = 0.023) high expressions but not CD133 expression (p = 0.169) forecasted exasperated OS.ConclusionITGA7, CD133, ALDH1 are inter‐correlated, and linked with poor differentiation, lymph node metastasis as well as worse survival in surgical cervical cancer.

CAIX-Mediated Control of LIN28/let-7 Axis Contributes to Metabolic Adaptation of Breast Cancer Cells to Hypoxia.

Solid tumors, including breast cancer, are characterized by the hypoxic microenvironment, extracellular acidosis, and chemoresistance. Hypoxia marker, carbonic anhydrase IX (CAIX), is a pH regulator providing a selective survival advantage to cancer cells through intracellular neutralization while facilitating tumor invasion by extracellular acidification. The expression of CAIX in breast cancer patients is associated with poor prognosis and metastases. Importantly, CAIX-positive hypoxic tumor regions are enriched in cancer stem cells (CSCs). Here we investigated the biological effects of CA9-silencing in breast cancer cell lines. We found that CAIX-downregulation in hypoxia led to increased levels of let-7 (lethal-7) family members. Simultaneously with the increase of let-7 miRNAs in CAIX-suppressed cells, LIN28 protein levels decreased, along with downstream metabolic pathways: pyruvate dehydrogenase kinase 1 (PDK1) and phosphorylation of its substrate, pyruvate dehydrogenase (PDH) at Ser-232, causing attenuation of glycolysis. In addition to perturbed glycolysis, CAIX-knockouts, in correlation with decreased LIN28 (as CSC reprogramming factor), also exhibit reduction of the further CSC-associated markers NANOG (Homeobox protein NANOG) and ALDH1 (Aldehyde dehydrogenase isoform 1). Oppositely, overexpression of CAIX leads to the enhancement of LIN28, ALDH1, and NANOG. In conclusion, CAIX-driven regulation of the LIN28/let-7 axis augments glycolytic metabolism and enhances stem cell markers expression during CAIX-mediated adaptation to hypoxia and acidosis in carcinogenesis.

Long noncoding RNA MACC1-AS1 promotes the stemness of hepatocellular carcinoma cells by antagonizing miR-145.

ObjectivesThis work aimed to investigate the roles of long noncoding (lnc)RNA MACC1-AS1 (MACC1 antisense RNA 1) in progression of hepatocellular carcinoma (HCC).MethodsReal-time quantitative PCR, western blot, spheroid formation, aldehyde dehydrogenase isoform 1 (ALDH1) activity analysis, luciferase reporter assay, and RNA pull-down analysis were used to examine MACC1-AS1–mediated effects on HCC cell stemness.ResultsMACC1-AS1 was highly expressed in HCC tissues and cells. MACC1-AS1 positively regulated the expression of stemness master regulators and inhibited spheroid-forming ability and ALDH1 activity. Furthermore, MACC1-AS1 promoted the stemness of HCC cells by antagonizing microRNA (miR)-145 activity. Overexpression of miR-145 also attenuated HCC cell stemness.ConclusionsThis work revealed a novel MACC1-AS1/miR-145 axis that regulates the stemness of HCC cells.

The Effect of P-Glycoprotein (P-gp), Nuclear Factor-Kappa B (Nf-κb), and Aldehyde Dehydrogenase-1 (ALDH-1) Expression on Metastases, Recurrence and Survival in Advanced Breast Cancer Patients

Objective::To investigate the level of three drug resistance proteins; P-glycoprotein 1 (P-gp), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and aldehyde dehydrogenase isoform 1 (ALDH1) expression and their relationship to metastasis, recurrence and survival in advanced breast cancer patients that received neoadjuvant chemotherapy.Methods:This study is a combination of prospective and retrospective cohort study involving one hundred and thirty one cases of advanced stage invasive breast cancer that have received neoadjuvant chemotherapy. Initial biopsy specimens (incisional biopsy or core biopsy) were taken from paraffin blocks. Immunohistochemistry (IHC) was used to detect P-gp, NF-κB, and ALDH1 expression. Prospectively analysed patients were followed for five years and evaluated for recurrence and death.Results:The expression of P-gp has no significant statistical correlation to metastases (p = 0.659), recurrence (p = 0.862) and survival (p = 0.835) in advanced stage breast cancer patients who received neoadjuvant chemotherapy. Similarly, ALDH1 was not correlated to metastases (p=0.120), recurrence (p = 0.186) and survival (p = 0.254) statistically. We found that NF-κB expression showed a significant correlation to metastases (p=0.004), recurrence (p = 0.016) and overall survival (p = 0.041) in advanced stage breast cancer patients after neoadjuvant chemotherapy.Conclusion:NF-κB expression is a potential marker that can be used to assess or to predict increasing risk of metastases, recurrence and survival in advanced stage breast cancer patients who receive neoadjuvant chemotherapy.

Lymphocyte-predominant triple-negative breast carcinomas in premenopausal patients: Lower expression of basal immunohistochemical markers

ObjectivesTriple-negative breast carcinomas (TNBCs) correspond to a molecular heterogeneous disease defined by lack of estrogen and progesterone receptor expression, and the absence of overexpression and/or amplification of HER2. Recent data indicate that clinical outcome in TNBC is affected by tumor-infiltrating lymphocytes, suggesting that they can benefit from immunotherapies. We selected 116 consecutive premenopausal patients with TNBC to compare the immunohistochemical profile of the group rich in tumor-infiltrating lymphocytes with those without this characteristic. Materials and methodsWe reviewed all the original histological sections to assess pathological features, and to select a representative area for tissue microarrays and immunohistochemical study. Estrogen and progesterone receptors, HER2 and Ki-67 were evaluated in whole histological sections. The following markers were analyzed in tissue microarrays sections: androgen receptor, cytokeratin 5/6, cytokeratin 14, epidermal growth factor receptor (EGFR), vimentin, p16, claudin-3, -4, and -7, p63, and aldehyde dehydrogenase isoform 1 (ALDH1). Lymphocyte-predominant breast cancer (LPBC) was defined by the presence of more than 50% of lymphocytes in the intratumoral stroma. ResultsTwenty-six (22.4%) patients present tumors classified as LPBC and 90 (77.6%) as non-LPBC. The two groups were similar regarding age of patients, tumor grade and Ki-67 positive cells. LPBC cases presented lower frequency of expression of the basal cytokeratins, EGFR, and basal-like immunoprofile. There was a trend to higher expression of ALDH1 by stromal intratumoral cells. The expression of all other markers were similar in the two groups. ConclusionsLymphocyte-predominant TNBC in premenopausal patients are mostly of non-basal phenotype.

Immunohistochemical Expression of CD56 and ALDH1 in Common Salivary Gland Tumors.

Natural killer (NK) cells, of which CD56 is a specific marker, play an important role in host defense against tumors. Cancer stem cells, of which aldehyde dehydrogenase isoform 1 (ALDH1) is an immunohistochemical marker, are a group of tumorigenic cells which are involved in migration and tumor recurrences. We aimed to evaluate the expression of ALDH1 and CD56 in common salivary gland tumors, as well as their relationship with each other and with a number of clinicopathologic factors. Forty-five paraffin blocks of salivary gland tumors (pleomorphic adenoma, mucoepidermoid carcinoma and adenoid cystic carcinoma, 15 samples each) were selected. Malignant tumors were classified into two groups: low-grade (including mucoepidermoid carcinoma grade I) and high-grade (including mucoepidermoid carcinoma grade III and adenoid cystic carcinoma). Immunohistochemical staining for ALDH1 and CD56 markers was performed. Data were analyzed using SPSS (20) and the Chi-square test. CD56 expression was significantly higher in benign and high-grade malignant tumors (P=0.01). ALDH1 overexpressed in all three salivary tumors, but not to statistically significant degree (P=0.54). There was no statistically significant correlation between ALDH1 and CD56 expression with demographic factors (age, gender, or location of tumor; P>0.05). It appears that the number of NK cells and their function change in different types of salivary gland tumors (benign/malignant) and stroma. NK cells are important components of the anti-tumor system; therefore immune dysfunction is associated with tumor progression in tumors of the salivary gland. ALDH1 overexpression suggests its role in tumorogenesis, but ALDH1 is not involved in the morphogenesis of salivary gland tumors.

Aldehyde dehydrogenase isoform 1 (ALDH1) expression as a predictor of radiosensitivity in laryngeal cancer

Aldehyde dehydrogenase isoform 1 (ALDH1) has been shown to be a marker of cancer stem cells (CSCs). These stem cells may be responsible for tumour perpetuation as well as local and distant invasion. Several studies have shown that CSCs are more chemoradiotherapy (CRT)-resistant and may be responsible for tumour recurrence. Other studies, in contrast, have found ALDH1 expression to be indicative of a better prognosis. We retrospectively evaluated 84 patients diagnosed and treated for laryngeal cancer between 2006 and 2011. All patients underwent curative-intent radiotherapy or CRT at our institution. 57 of the 84 tumour samples contained sufficient material for ALDH1 assessment. ALDH1 expression was detected in 17.5% (10/57) of the tissue samples. None of the tumours from stage I patients tested positive for ALDH1. The relapse rate in ALDH1+patients was 10 versus 51.2% for ALDH1-. No differences in overall survival were observed between the groups; however, disease-free survival was 90% for the ALDH1+group versus 48.9% for ALDH1- patients (p=0.034). The patients in this study with ALDH1+tumours had better outcomes than their counterparts with ALDH1- tumours. This finding suggests that not all CSCs are resistant to conventional cancer treatments. It may also imply that new methods of correctly identifying these cells are needed.

Cancer stem cell markers in lung cancer

Abstract Purpose Lung cancer is responsible for most cancer-related deaths. There are two broad types of lung tumors, usually classified as small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). Current clinicopathological staging systems provide the advantage of standardized criteria for assessing tumor stage, and a relationship between advancing tumor stage and poor prognosis has been established for NSCLC. However, these staging systems have not led to clear criteria for selection of therapy for individual patients with NSCLC. The concept of therapy based on anatomical location, as used in staging systems, is poorly associated with the cancer stem cell (CSC) characteristics of individual tumor tissues. CSCs may have self-renewal and multipotent differentiation abilities and be responsible for tumor initiation, progression, and metastasis; they are highly resistant to chemoradiotherapy. Therefore, research into CSCs will provide the basis for developing of novel diagnostic and therapeutic strategies. We review aldehyde dehydrogenase isoform 1 (ALDH1), CD133, CD44 and CD166 as CSC markers, as weel as the Wnt/β-catenin pathway, KRAS, and the embryonic stem cell (ESC) signature. Study selection PubMed databases were searched for relevant articles. Results The positivity rate for ALDH1 immunohistochemical (IHC) staining is 19% in patients with stage I NSCLC [1]. The positivity rates for CD133 are 19–48.9% [2–4] and for CD44 are 50.4–67.3% in patients with NSCLC [5,6]. Conclusions CSCs have been identified in lung cancer and will provide new therapeutic targets for lung cancer. Research on these cells could improve the prognosis of lung cancer.

Cancer stem cells are enriched in Fanconi anemia head and neck squamous cell carcinomas.

Fanconi anemia (FA) patients have an increased risk of head and neck squamous cell carcinoma (HNSCC) at a higher rate with no apparent risk factors. HNSCC of FA patients is an aggressive tumor characterized by multifocal origin, early metastases and frequent recurrences. Given that cancer stem cells (CSC) drive tumorigenesis, tumor recurrence and metastasis, in this study, we characterized the CSC population in FA and sporadic HNSCC. The Aldefluor assay was used to characterize and isolate CSC with high aldehyde dehydrogenase (ALDH) activity (ALDHpos) in cell lines derived from FA and sporadic HNSCC. Isolated ALDHpos and ALDHneg cells were examined for the expression of stemness genes using reverse transcription-polymerase chain reaction (RT-PCR) array. Tumor cell-derived FA and sporadic HNSCC were examined for their ability to form tumorspheres in vitro. Stem-like cell population in FA and sporadic HNSCC in human and mouse xenograft tumors were evaluated using ALDH isoform 1 (ALDH1) immunohistochemistry. FA-HNSCC cell lines harbor a greater proportion of ALDHpos cells (15–31%) compared to sporadic HNSCC (10%). Expression of Nanog, Oct-3/4 and Stella, molecular markers of undifferentiated embryonic stem (ES) cells were detected in the ALDHpos FA-HNSCC cells and not in the ALDHneg cells. FA-HNSCC cell lines revealed enhanced in vitro tumorsphere formation compared to sporadic HNSCC cells. A higher percentage of ALDH1pos tumor cells are noted in the human and mouse xenograft tumors of FA-HNSCC compared to sporadic HNSCC tumors. FA-HNSCC are highly enriched for CSC and may serve as a model to develop CSC-targeted therapies for HNSCC.

Enrichment and functional characterization of cancer stem cells from squamous cell carcinoma of head and neck by suspension culture

Initiation, growth, recurrence, and metastasis of head and neck squamous cell carcinoma (HNSCC) have been related to the cancer stem cells (CSC) that can be identified by their aldehyde-dehydrogenase-isoform-1 (ALDH-1) activity. In this study, we try to prove that suspension culture can enrich ALDH-1 high expression cells within HNSCC cell lines and the enriched cells possess cancer stem cell properties. Cells from five HNSCC cell lines were cultured in ultra-low attachment plates in serum-free Quantum 263 medium supplemented with 10 ng/ml EGF and 10 ng/ml bFGF, and ALDH-1 expression level was evaluated by ALDEFLUOR assay. ALDH-1 high expression cells were separated by FACS sorting, and their phenotypical and functional properties were characterized. Spheroids can be formed from all five HNSCC cell lines (UD-SCC1, UT-SCC22, UM-SCC11B, UT-SCC9 and UT-SCC24A) under anchorage independent culture condition. The proportion of ALDH1 high expression cells were highly increased in speroids derived cells (SDCs) compared with their monolayers (P < 0.05). The clones formed by ALDH1 high expression cells on average contained 197 (197 ± 47) cells compared with 33 (33 ± 16) cells in clones generated from ALDH1 low expression cells (P < 0.01). Single ALDH1 high expression cell could significantly better regenerate a spheroid (UT-SCC9: 17.1%, UD-SCC1:19.3%), whereas under the same conditions single ALDH1 low expression cells regenerated only in one case a spheroid (P < 0.01). SDCs from all five tested cell lines also showed a significantly increased invasion capacity (P < 0.05). We also found that the mRNA levels of Oct-4, Sox2, and Nanog were all significantly increased in the SDC. The reactive oxygen species (ROS) levels in SDCs from UD-SCC1 and UT-SCC24A were significantly increased compared with their monolayer counterpart [(26.3 ± 4.9)% vs (8.6 ± 1.7)% and (72.1 ± 6.1)% vs (23.7 ± 7.5)%, P < 0.05)]. Cancer stem cells can be enriched by suspension culture, which may be of importance in investigation of their contribution to therapy resistance, tumor recurrence and metastasis.

Antidiabetic Drug Metformin Prevents Progression of Pancreatic Cancer by Targeting in Part Cancer Stem Cells and mTOR Signaling

Epidemiologic studies have shown that diabetes mellitus is associated positively with increased risk of pancreatic ductal adenocarcinoma (PDAC), and recent meta-analysis studies showed that metformin, reduces the risk of pancreatic cancer (PC). We tested the effects of metformin on pancreatic intraepithelial neoplasia (PanIN) and their progression to PDAC in p48Cre/+.LSL-KrasG12D/+ transgenic mice. Mice fed control diet showed 80% and 62% incidence of PDAC in males and females, respectively. Male mice showed 20% and 26%, and female mice showed 7% and 0% PDAC incidence with 1000- and 2000-ppm metformin treatments, respectively. Both doses of metformin decreased pancreatic tumor weights by 34% to 49% (P < 0.03–0.001). The drug treatment caused suppression of PanIN 3 (carcinoma in situ) lesions by 28% to 39% (P < .002) and significant inhibition of carcinoma spread in the pancreas. The pancreatic tissue and/or serum of mice fed metformin showed a significant inhibition of mammalian target of rapamycin (mTOR), extracellular signal-regulated kinases (ERK), phosphorylated extracellular signal-regulated kinases (pErk), and insulin-like growth factor 1 (IGF-1) with an increase in phosphorylated 5′ adenosine monophosphate kinase (pAMPK), tuberous sclerosis complex 1 (TSC1, TSC2), C-protein and an autophagy related protein 2 (ATG2). The cancer stem cell (CSC) markers were significantly decreased (P < 0.04–0.0002) in the pancreatic tissue. These results suggest that biologic effects of metformin are mediated through decreased CSC markers cluster of differentiation 44 (CD44 and CD133), aldehyde dehydrogenase isoform 1 (ALDH1), and epithelial cell adhesion molecule (EPCAM) and modulation of the mTOR signaling pathway. Our preclinical data indicate that metformin has significant potential for use in clinical trials for PC chemoprevention.

In vitro and in vivo expression of aldehyde dehydrogenase 1 in oral squamous cell carcinoma

Aldehyde dehydrogenase isoform 1 (ALDH1) is a useful marker of cancer-initiating cells (CICs) in various organs. In this study, we investigated whether alterations in ALDH1 immunostaining and enzymatic activity in tumor cell populations predicted clinicopathological factors of prognostic importance for cancer progression and contributed to the characteristics of CICs in cisplatin-treated oral squamous cell cancer (OSCC) cells. We evaluated the association between the proportion of ALDH1-positive tumor cells and the clinicopathological features in 90 patients with OSCC. We also examined ALDH1 enzymatic activity, ABCG2 expression, invasive capacity and the ability to self-renew in OSCC cells treated with or without cisplatin. The clinicopathological results showed that elevated ALDH1 expression correlated with local recurrence. In in vitro experiments, the percentage of cells exhibiting ALDH1 enzymatic activity significantly increased among cisplatin-surviving cells (CiSCs) according to flow cytometry. Furthermore, CiSCs demonstrated upregulated expression of ABCG2, their invasive capacity increased, and their ability to generate cancer spheres was enhanced. An increased population of cells exhibiting ALDH1 immunostaining is a predictive marker of local recurrence. ALDH1 expression and activity contributes to the characteristics of CICs in OSCC.

Evidence for Epithelial-Mesenchymal Transition in Cancer Stem Cells of Head and Neck Squamous Cell Carcinoma

Initiation, growth, recurrence, and metastasis of head and neck squamous cell carcinomas (HNSCC) have been related to the behavior of cancer stem cells (CSC) that can be identified by their aldehyde-dehydrogenase-isoform-1 (ALDH1) activity. We quantified and enriched ALDH1+ cells within HNSCC cell lines and subsequently characterized their phenotypical and functional properties like invasion capacity and epithelial-mesenchymal transition (EMT). Spheroid culture enriched CSC from five HNSCC cell lines by up to 5-fold. In spheroid-derived cells (SDC) and the parental monolayer-derived cell line ALDH1, CD44, CD24, E-Cadherin, α-SMA, and Vimentin expression was compared by flow-cytometry and immunofluorescence together with proliferation and cell cycle analysis. Invasion activity was evaluated by Matrigel assay and expression of stemness-related transcription factors (TF) Nanog, Oct3/4, Sox2 and EMT-related genes Snail1 and 2, and Twist by real-time PCR. All cell lines formed spheroids that could self-renew and be serially re-passaged. ALDH1 expression was significantly higher in SDC. ALDH1+ cells showed increased colony-formation. The proportion of cells with a putative CSC marker constellation of CD44+/CD24− was highly variable (0.5% to 96%) in monolayer and spheroid cultures and overlapped in 0%–33% with the CD44+/CD24−/ALDH1+ cell subset. SDC had significantly higher invading activity. mRNA of the stemness-related genes Sox2, Nanog, and Oct3/4 was significantly increased in SDC of all cell lines. Twist was significantly increased in two while Snail2 showed a significant increase in one and a significant decrease in SDC of two cell lines. SDC had a higher G0 phase proportion, showed high-level expression of α-SMA and Vimentin, but significantly decreased E-Cadherin expression. HNSCC-lines harbor potential CSC, characterized by ALDH1 and stemness marker TF expression as well as properties like invasiveness, quiescence, and EMT. CSC can be enriched by anchorage-independent culture techniques, which may be important for the investigation of their contribution to therapy resistance, tumor recurrence and metastasis.

Distinct Expression Levels and Patterns of Stem Cell Marker, Aldehyde Dehydrogenase Isoform 1 (ALDH1), in Human Epithelial Cancers

Aldehyde dehydrogenase isoform 1 (ALDH1) has been proved useful for the identification of cancer stem cells. However, our knowledge of the expression and activity of ALDH1 in common epithelial cancers and their corresponding normal tissues is still largely absent. Therefore, we characterized ALDH1 expression in 24 types of normal tissues and a large collection of epithelial tumor specimens (six cancer types, n = 792) by immunohistochemical staining. Using the ALDEFUOR assay, ALDH1 activity was also examined in 16 primary tumor specimens and 43 established epithelial cancer cell lines. In addition, an ovarian cancer transgenic mouse model and 7 murine ovarian cancer cell lines were analyzed. We found that the expression levels and patterns of ALDH1 in epithelial cancers are remarkably distinct, and they correlate with their corresponding normal tissues. ALDH1 protein expression levels are positively correlated with ALDH1 enzymatic activity measured by ALDEFLUOR assay. Long-term in vitro culture doesn't significantly affect ALDH1 activity in epithelial tumor cells. Consistent with research on other cancers, we found that high ALDH1 expression is significantly associated with poor clinical outcomes in serous ovarian cancer patients (n = 439, p = 0.0036). Finally, ALDHbr tumor cells exhibit cancer stem cell properties and are resistant to chemotherapy. As a novel cancer stem cell marker, ALDH1 can be used for tumors whose corresponding normal tissues express ALDH1 in relatively restricted or limited levels such as breast, lung, ovarian or colon cancer.

ALDH1 as a Functional Marker of Cancer Stem and Progenitor Cells

Stem cells have now been described in a variety of tissues, even in those where the cells' turn over rate is slow, such as the brain and the resting mammary gland. There is also accumulating evidence that tumors are derived from and are maintained by a rare population of dysregulated stem cells. However, discrepancies in the markers used and reported have slowed down the functional characterization of these somatic stem cells. To circumvent this challenging issue, universal stem cell markers with properties common to all stem cell types must be discovered and exploited. In line with this idea, the measurement of aldehyde dehydrogenase isoform 1 (ALDH1) activity shows promising potential as a universal marker for the identification and isolation of stem cells from multiple sources. Herein, we review the available data reporting utilization of ALDH1 activity as a means to identify and isolate stem cells and cancer stem cells, with a special focus on the mammary gland and breast cancer.