Cancer Stem Cells In Solid Tumors Research Articles

Informed by Cancer Stem Cells of Solid Tumors: Advances in Treatments Targeting Tumor-Promoting Factors and Pathways.

Cancer stem cells (CSCs) represent a subpopulation within tumors that promote cancer progression, metastasis, and recurrence due to their self-renewal capacity and resistance to conventional therapies. CSC-specific markers and signaling pathways highly active in CSCs have emerged as a promising strategy for improving patient outcomes. This review provides a comprehensive overview of the therapeutic targets associated with CSCs of solid tumors across various cancer types, including key molecular markers aldehyde dehydrogenases, CD44, epithelial cellular adhesion molecule, and CD133 and signaling pathways such as Wnt/β-catenin, Notch, and Sonic Hedgehog. We discuss a wide array of therapeutic modalities ranging from targeted antibodies, small molecule inhibitors, and near-infrared photoimmunotherapy to advanced genetic approaches like RNA interference, CRISPR/Cas9 technology, aptamers, antisense oligonucleotides, chimeric antigen receptor (CAR) T cells, CAR natural killer cells, bispecific T cell engagers, immunotoxins, drug-antibody conjugates, therapeutic peptides, and dendritic cell vaccines. This review spans developments from preclinical investigations to ongoing clinical trials, highlighting the innovative targeting strategies that have been informed by CSC-associated pathways and molecules to overcome therapeutic resistance. We aim to provide insights into the potential of these therapies to revolutionize cancer treatment, underscoring the critical need for a multi-faceted approach in the battle against cancer. This comprehensive analysis demonstrates how advances made in the CSC field have informed significant developments in novel targeted therapeutic approaches, with the ultimate goal of achieving more effective and durable responses in cancer patients.

Exploring stage‑specific embryonic antigen 3 involvement in oral cancer progression and as a potential target for taxane‑based chemotherapy.

Despite significant advancements in therapeutic approaches, oral neoplasms remain formidable and life‑threatening conditions that affect a substantial number of individuals worldwide. Within oral malignancies, a subset of cancer stem cells (CSCs) represent a crucial population responsible for tumor initiation and progression. The identification of reliable markers for the detection and characterization of CSCs in solid tumors, particularly in the context of oral cancers, remains an ongoing challenge. Stage‑specific embryonic antigen 3 (SSEA3), previously associated with mesenchymal stem cells and linked to the progression of breast neoplasms and poor prognosis, has yet to be comprehensively elucidated in the context of oral malignancies. The present study aimed to investigate the expression and properties of SSEA3 in 16 distinct subsets of human oral neoplastic cell lines, classified as either CD44 positive (+) or CD44 negative (‑). For the first time, SSEA3 was examined as an indicator of tumorigenicity and resistance to taxane‑derived chemotherapeutic agents. In the majority of oral neoplastic cell lines analyzed, SSEA3 was expressed in a small population of CD44(+) cells. Significantly, SSEA3(+) cells exhibited heightened proliferative activity and upregulated expression of genes associated with stem cells compared with SSEA3(‑) cells. The aforementioned findings suggested that SSEA3 may contribute to the evolution and progression of oral malignancies by fostering tumor growth. Furthermore, SSEA3(+) cells displayed increased sensitivity to taxane‑based pharmaceuticals, indicating the potential for SSEA3 to be a viable target in the treatment schema for oral cavity neoplasms. In conclusion, the present study provides novel insight into the role of SSEA3 in the progression and management of oral neoplasms, potentially paving the way for more effective therapeutic approaches.

Markers and Reporters to Reveal the Hierarchy in Heterogeneous Cancer Stem Cells.

A subpopulation within cancer, known as cancer stem cells (CSCs), regulates tumor initiation, chemoresistance, and metastasis. At a closer look, CSCs show functional heterogeneity and hierarchical organization. The present review is an attempt to assign marker profiles to define the functional heterogeneity and hierarchical organization of CSCs, based on a series of single-cell analyses. The evidences show that analogous to stem cell hierarchy, self-renewing Quiescent CSCs give rise to the Progenitor CSCs with limited proliferative capacity, and later to a Progenitor-like CSCs, which differentiates to Proliferating non-CSCs. Functionally, the CSCs can be tumor-initiating cells (TICs), drug-resistant CSCs, or metastasis initiating cells (MICs). Although there are certain marker profiles used to identify CSCs of different cancers, molecules like CD44, CD133, ALDH1A1, ABCG2, and pluripotency markers [Octamer binding transcriptional factor 4 (OCT4), SOX2, and NANOG] are used to mark CSCs of a wide range of cancers, ranging from hematological malignancies to solid tumors. Our analysis of the recent reports showed that a combination of these markers can demarcate the heterogeneous CSCs in solid tumors. Reporter constructs are widely used for easy identification and quantification of marker molecules. In this review, we discuss the suitability of reporters for the widely used CSC markers that can define the heterogeneous CSCs. Since the CSC-specific functions of CD44 and CD133 are regulated at the post-translational level, we do not recommend the reporters for these molecules for the detection of CSCs. A promoter-based reporter for ABCG2 may also be not relevant in CSCs, as the expression of the molecule in cancer is mainly regulated by promoter demethylation. In this context, a dual reporter consisting of one of the pluripotency markers and ALDH1A1 will be useful in marking the heterogeneous CSCs. This system can be easily adapted to high-throughput platforms to screen drugs for eliminating CSCs.

Blood and Cancer: Cancer Stem Cells as Origin of Hematopoietic Cells in Solid Tumor Microenvironments.

The concepts of hematopoiesis and the generation of blood and immune cells from hematopoietic stem cells are some steady concepts in the field of hematology. However, the knowledge of hematopoietic cells arising from solid tumor cancer stem cells is novel. In the solid tumor microenvironment, hematopoietic cells play pivotal roles in tumor growth and progression. Recent studies have reported that solid tumor cancer cells or cancer stem cells could differentiate into hematopoietic cells. Here, we discuss efforts and research that focused on the presence of hematopoietic cells in tumor microenvironments. We also discuss hematopoiesis from solid tumor cancer stem cells and clarify the notion of differentiation of solid tumor cancer stem cells into non-cancer hematopoietic stem cells.

Abstract SY17-02: Solid tumor cancer stem cells: From bench to bedside

Abstract Stem cells are essential for maintenance of multiple tissues including the intestine, skin, brain and breast. Remarkably, cancers invariably arise in tissues that contain stem cells whose function is to maintain and repair tissues for the life of the animal. Self renewal, the mechanisms by which stem cells regenerate themselves, is the fundamental property by which stem cells maintain themselves. Our laboratory investigates the fundamental molecular mechanisms of self renewal. Our studies have found that stem cells can be identified by the expression of genes required for self renewal AND by the lack of expression of genes that suppress self renewal. The specific components of self renewal pathways in normal and malignant colon and mammary gland stem cells will be discussed. Stem cell pathways contribute to minimal residual disease after cancer therapy will be discussed. Finally, the application of stem cell biology to cancer therapy will be described. Approximately 4-7% of stage 2 colon cancers consist of homogeneous populations of undiffentiated CDX2- cancer cells. Stage 2 colon cancer patients are generally not thought to benefit from adjuvant chemotherapy. However, stage 2 colon cancer patients with CDX 2- cancer do appear to benefit. Citation Format: Michael F. Clarke. Solid tumor cancer stem cells: From bench to bedside [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr SY17-02.

Stem Cell-Associated Heterogeneity in Glioblastoma Is a Result of Intrinsic Tumor Plasticity Shaped by the Microenvironment

Cancer stem cells (CSCs) have been proposed to underlie the hierarchical organization of Glioblastoma (GBM) causing resistance to treatment, however the identity of CSCs in solid tumors remains largely elusive. Here we find that GBM cells expressing cell membrane CSC-associated markers do not represent a clonal entity defined by distinct functional properties and/or transcriptomic profiles, but rather a plastic state that most cancer cells can adopt. We show that phenotypic heterogeneity arises from non-hierarchical, reversible state transitions that are instructed by the microenvironment. While all tested cancer cell subpopulations survive and adjust their phenotype in vivo, their speed of plasticity differs resulting in variable tumor growth rates. Thus CSC-associated phenotypic heterogeneity is a result of stochastic reversible plasticity and increased tumorigenic potential in vivo correlates with fast adapting cell states.

Blockade of Notch3 inhibits the stem-like property and is associated with ALDH1A1 and CD44 via autophagy in non-small lung cancer.

Acquired resistance to standard chemotherapy causes treatment failure in patients with local advanced and advanced non-small lung cancer (NSCLC). Cancer stem cells (CSCs) are a small subpopulation within cancer that is thought to be resistant to conventional chemotherapy. The Notch pathway is one of the most intensively studied for putative therapeutic targets of CSCs in solid tumors. In our study, suppression of Notch3 decreased colony and sphere formation of stem-like property in lung cancer cells. In addition, Notch3 expression was demonstrated to be upregulated in the patients with chemoresistance and related to poor prognosis of NSCLC patients. Our results also showed that CSC markers ALDH1A1 and CD44 were highly expressed in NSCLC patients with chemoresistance and these two markers were positively correlated with Notch3 expression in lung cancer specimens from TCGA database. Furthermore, the lung cancer cells with drug resistance were shown to be associated with activation of autophagy. All the data support a crucial role of Notch3 in the increase of stem-like property in NSCLC cells that might be associated with upregulation of ALDH1A1 and CD44 and activation of autophagy.

CD44 variant 6 is correlated with peritoneal dissemination and poor prognosis in patients with advanced epithelial ovarian cancer.

Cancer stem cells (CSCs) drive tumor initiation and metastasis in several types of human cancer. However, the contribution of ovarian CSCs to peritoneal metastasis remains unresolved. The cell adhesion molecule CD44 has been identified as a major marker for CSCs in solid tumors, including epithelial ovarian cancer. CD44 exists as a standard form (CD44s) and also as numerous variant isoforms (CD44v) generated by alternative mRNA splicing. Here we show that disseminated ovarian tumors in the pelvic peritoneum contain highly enriched CD44v6-positive cancer cells, which drive tumor metastasis and are responsible for tumor resistance to chemotherapy. Clinically, an increased number of CD44v6-positive cancer cells in primary tumors was associated with a shortened overall survival in stage III–IV ovarian cancer patients. Furthermore, a subpopulation of CD44v6-positive cancer cells manifested the ability to initiate tumor metastasis in the pelvic peritoneum in an in vivo mouse model, suggesting that CD44v6-positive cells show the potential to serve as metastasis-initiating cells. Thus, the peritoneal disseminated metastasis of epithelial ovarian cancer is initiated by the CD44v6-positive subpopulation, and CD44v6 expression is a biomarker for the clinical outcome of advanced ovarian cancer patients. Given that a distinct subpopulation of CD44v6-positive cancer cells plays a critical role in peritoneal metastasis, definitive treatment should target this subpopulation of CD44v6-positive cells in epithelial ovarian cancer.

Cancer Stem Cells: Biological Features and Targeted Therapeutics

Advance in stem cells (SCs) has become significant by the isolation of the tissue-specific SCs in a tissue, because it is the beginning of using SC utility for regenerative medicine. Likewise in SCs, a small subpopulation of cancer cells, named cancer stem cells (CSCs), also have similar properties. These properties include indefinite self-renewal potential and sharing similar signaling pathways with normal SCs, because the originality of CSCs is from the mutation of normal SCs. Hierarchically, CSCs in solid tumors may organize from the normal SCs in the highest cellular hierarchy of these cancer cells. The functional assay techniques to assess the differentiation frequency of normal SCs are similarly used in CSCs to sustain tumor growth and recurrence after therapy. In this review, we discuss the different parallels between adult SCs and CSCs in solid cancer disease and applications toward targeted therapy in use of molecular level on CSCs.

Abstract 213: VS-5584 a dual mTORC1/2 and PI3K inhibitor has anti-tumor activity in multiple in vivo xenograft tumor models and enhanced efficacy in combination with cisplatin or docetaxel

Abstract Verastem is developing VS-5584, a potent and selective dual inhibitor of the mammalian target of rapamycin complexes 1 and 2 (mTOR) and Class I phosphatidylinositide 3-kinases (PI3K), for the treatment of advanced cancer. The PI3K/mTOR signaling pathway is a key regulator in cancer progression and in the survival of cancer stem cells (CSCs). VS-5584 has been shown to be an equipotent inhibitor of all four human Class I PI3K isoforms and the mTOR kinase, and PI3K signaling has been implicated in the maintenance of CSCs in solid tumors. In multiple orthogonal in vitro assays, VS-5584 has been shown to preferentially target CSCs and exhibited significant antiproliferative activity across multiple cancer cell lines. Furthermore, oral administration of VS-5584 has been shown to reduce CSCs in xenograft models. The in vivo antitumor efficacy of once daily and intermittent oral administration of VS-5584 was evaluated in multiple xenograft tumor models representing small cell (SCLC) and non-small cell lung cancer (NSCLC), triple negative breast cancer (TNBC) and mesothelioma. Once daily (QD) treatment with VS-5584 demonstrated potent anti-tumor activity, with mean percentage tumor growth inhibition (TGI) ranging from 40% to 97% (P < 0.05). In these models, TGI was dose-dependent with dosages at and above 15 mg/kg showing good antitumor activity (P < 0.05). Interestingly, tumor regression was observed in 33% (3/9) of mice bearing H69 (SCLC) tumors, 60% (6/10) of mice bearing MDA-MB-468 (TNBC) tumors and 50% (5/10) of mice bearing NCI-H226 mesothelioma tumors. This significant antitumor activity was generally observed at well-tolerated dosages. In studies exploring intermittent dosing schedules, efficacy and tolerability were similar or better with a QD 5 days on/2 days off or Monday, Wednesday, Friday schedule compared to continuous daily dosing. We also explored the efficacy of VS-5584 in combination with either cisplatin or docetaxel. In these studies, VS-5584 plus either cisplatin or docetaxel showed significant TGI compared to cisplatin alone in H69 SCLC and docetaxel alone in A549 NSCLC xenograft models (P < 0.05). This potent in vivo anti-tumor activity in xenograft models of NSCLC, SCLC, TNBC and mesothelioma suggests that VS-5584 has the potential for anticancer activity across a variety of cancer types. Intermittent dosing with VS-5584 was sufficient to achieve good efficacy while minimizing side effects, thus allowing a broader therapeutic window compared to QD dosing. VS-5584 in combination with either cisplatin or docetaxel had enhanced anti-tumor activity compared to either chemotherapeutic agent or VS-5584 alone in two in vivo models of lung cancer. VS-5584 is being evaluated in a Phase 1 clinical trial assessing intermittent dosing in subjects with advanced non-hematologic malignancies or lymphoma. Citation Format: Anthony F. Trombino, Vihren N. Kolev, Quentin G. Wright, Qunli Xu, Mahesh V. Padval. VS-5584 a dual mTORC1/2 and PI3K inhibitor has anti-tumor activity in multiple in vivo xenograft tumor models and enhanced efficacy in combination with cisplatin or docetaxel. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 213. doi:10.1158/1538-7445.AM2014-213

Cancer stem cell detection and isolation.

Only 10 % of cancer-related deaths result from primary tumors; most are caused by metastatic tumors. It is believed that the metastatic power of tumor cells is attributed to features of a stem cell-like subpopulation of tumor cells known as cancer stem cells (CSCs). Cancer stem cells are resistant to chemotherapeutic treatments and can induce dormancy in tumor cells for long periods. Detection, isolation, and characterization of CSCs in solid tumors are hallmarks of cancer-targeted therapies in recent years. There are inevitable similarities between normal and cancer stem cells; therefore, finding specific methods or markers to differentiate them is critical to cancer therapies. Considering CSCs involvement in tumor relapse and chemotherapeutic resistance, identification of such cells in tumors is imperative for effective targeted therapy. The present review introduces practical and specific protocols used to isolate CSCs from solid tumors from colon, esophagus, liver, breast, brain, and cervix.

ABCG2 as a potential cancer stem cell marker in breast cancer.

e12007 Background: The identification of cancer stem cell (CSC) markers gives opportunity to develop new target therapies. ABCG2 protein is reported as a predictive marker for breast cancer resistance to chemotherapy and as a potential marker for CSC in solid tumors. Methods: We included prospectively 41 patients with locally advanced or metastatic (LAMBC) invasive ductal carcinomas treated with NACT. The expression of CD44/CD24 and ABCG2 was analyzed by flow cytometry after fresh tumor sample digestion. The mammosphere assay (Mammocult) was carried out in 23 samples. We analyzed the correlation between the percentage of ESA+/ABCG2+ and ESA+/CD44+/CD24- cells within the primary tumor with the number of spheres in culture and their relationship with clinical and pathological parameters. ABCG2+ and ABCG2- cells from four primary tumors and from MDA-MB231 cell line were sorted and cultured in triplicate in Mammocult medium for 7 days. The ability to form sphere was analyzed. Patients’ mean age was 52.8 ± 10.3 yo. The ER, PgR and HER2 positive expression rates were 65%, 58% and 45%, respectively. Patients were treated with docetaxel/anthracycline combination (n = 33) of FEC75 combination (n = 8). Results: Complete pathological response was observed in 10 patients (24%). ER negative patients and patients with lower percentage of ABCG2+ cells within the tumor were more likely to achieve near pCR (44% versus 11%, p = 0.04; and 50% versus 14%, p = 0.04, respectively). We did not observe a significant association between pCR and PgR and HER2 expression or the percentage of CD44+/CD24- cells within the tumor. There was a strong correlation between the percentage of ESA+/ABCG2+ cells and the number of mammospheres in culture (r = 0.63; p= 0.0007). This correlation was not significant comparing to CD44+/CD24- cells. Additionally, ABCG2+ cells from primary tumors and MB-231 cell line form a higher number of spheres in culture than ABCG2- (mean difference = 1.15±0.45 /1000 cells, p = 0.04; mean difference = 0.48±0.04 /1000cells, p = 0.008, respectively). Conclusions: ABCG2 is a potential marker for CSC in breast cancer, and the percentage of ABCG2+ cancer cells within the tumor is a predictive factor for pCR in LAMBC patients subjected to NACT.

Thoughts about cancer stem cells in solid tumors

Cancer chemotherapy efficacy is frequently impaired by either intrinsic or acquired tumor resistance. A fundamental problem in cancer research is identifying the cell type that is capable of sustaining neoplastic growth and its origin from normal tissue cells. In recent years, the cancer stem cell (CSC) theory has changed the classical view of tumor growth and therefore the therapeutic perspective. Overcoming intrinsic and acquired resistance of cancer stem/progenitor cells to current clinical treatments represents a major challenge in treating and curing the most aggressive and metastatic cancers. On the other hand, the identification of CSCs in vivo and in vitro relies on specific surface markers that should allow the sorting cancer cells into phenotypically distinct subpopulations. In the present review, recent papers published on CSCs in solid tumors (breast, prostate, brain and melanoma) are discussed, highlighting critical points such as the choice of markers to sort CSCs and mouse models to demonstrate that CSCs are able to replicate the original tumor. A discussion of the possible role of aldehyde dehydrogenase and CXCR6 biomarkers as signaling molecules in CSCs and normal stem cells is also discussed. The author believes that efforts have to be made to investigate the functional and biological properties of putative CSCs in cancer. Developing diagnostic/prognostic tools to follow cancer development is also a challenge. In this connection it would be useful to develop a multidisciplinary approach combining mathematics, physics and biology which merges experimental approaches and theory. Biological models alone are probably unable to resolve the problem completely.

Abstract 4362: RBM3 overexpression promotes cancer stem cell expansion through activation of Notch-1 signaling

Abstract Cancers are heterogeneous population of cells, a minor portion of which exhibit stem-like characteristics. Recent evidence suggests that these Cancer Stem Cells (CSCs) are responsible for tumor behavior. Recently, we reported that RNA binding protein RBM3 is overexpressed in various tumors of epithelial origin and downregulating its expression results in inhibition of tumor growth. Moreover, RBM3 affects the proliferation of CD34+ hematopoietic stem cell. Overexpression of RBM3 induces NIH-3T3 cells to transform and grow in an anchorage independent manner, and form tumors in athymic nude mice suggesting RBM3 is a proto-oncogene. Given these observations, we sought to determine whether RBM3 expression affects CSCs in solid tumors and its function in tumor initiation and/or metastasis. We have recently demonstrated that Doublecortin like Kinase-I (DCAMKL-1/DCLK1), a microtubule-associated kinase is a marker of quiescent intestinal stem cells. Immunohistochemical analyses of the NIH3T3-RBM3 tumors demonstrated an increase in the number of DCLK-1+ stem cells. Using fluorescence-activated cell sorting, we were able to isolate these DCLK-1+ stem cells from the bulk of the tumor and grow them in tissue culture dishes. We have named these cells as RNA binding protein-Induced Cancer Stem Cells (RICSCs). We next determined the stemness of the DCLK-1+ RICSCs. For this, we performed serial dilutions of the RICSCs starting at 10,000 cells and injected them into the flanks of nude mice. Even when 500 cells were injected, a primary tumor was observed at about 10 weeks; the histological analysis of the tissues revealing metastatic lesions in the lung, liver, bone and spleen. Recent studies with mammary and neuroectodermal tumors have suggested that inappropriate Notch activation promotes self-renewal and transformation of progenitor cells. We observed that there was a significant upregulation of activated Notch-1 expression in the NIH-3T3-RBM3 RICSCs. Inhibition of Notch-1 with a specific inhibitor, DAPT resulted in the arrest of RICSC-mediated tumor growth in nude mice. These data demonstrate that Notch signaling is essential for self-renewal in stem cells thereby affecting tumor growth. Taken together, these data imply that overexpression of RBM3 results in increased dedifferentiation into cancer stem cells that have an aggressive metastatic phenotype. These CSCs have great potentials for aiding in our understanding of oncogenesis and metastatic cascades. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4362. doi:10.1158/1538-7445.AM2011-4362

Abstract 3324: Epithelial mesenchymal transition is associated with chemoresistance of poorly differentiated hepatoma cells

Abstract BACKGROUND: Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths worldwide. It is the most rapidly increasing type of cancers in the US. Chemotherapy has been largely ineffective for HCC treatment, especially in cases with poorly-differentiated HCC. Cancer stem cells (CSCs) are a critical subpopulation that may be responsible for the initiation, progression, metastasis and recurrence of malignancies. CD133 and aldehyde dehydrogenase (ALDH) are useful markers to identify CSCs in solid tumors, such as lung and pancreatic cancers. AIMS: To separate CD133+/ALDHhigh cells in well-defined hepatoma cell lines, and to evaluate chemosentivity based on their CSC marker profile. METHODS: Hepatoma cell lines: HepG2, Hep3B, Huh-7, HLE, HLF and SKHep1 were separated into CD133+/ALDHhigh and CD133−/ALDHlow subpopulations by FACS. The resulting subpopulations were seeded on non-attachable plates for spheroid formation or used for chemosentivity assays. Epithelial mesenchymal transition (EMT) was determined by immunocytochemical staining of E-cadherin and vimentin. Gene expression of procollagen type I (α1) (Procoll-I) and transforming growth factor β1 (TGF-β1) was determined by quantitative RT-PCR. RESULTS: In well-differentiated hepatoma cell lines, HepG2, Hep3B and Huh-7, the positivity for CD133+/ALDHhigh was 1.1, 13.4 and 15.6%; whereas, poorly-differentiated hepatoma cells were almost all negative for these two markers. The positivity for CD133/EpCAM was 2.3, 10.3 and 18.3% in HepG2, Hep3B and Huh-7 cells, whereas it was almost negative in HLE, HLF and SKHep1 cells. FACS-enriched CD133+/ALDHhigh HepG2, Huh-7 and Hep3B cells were able to form spheroids in non-attachable culture plates; whereas their negative counterparts failed. In contrast, CD133−/ALDHlow SKHep1, HLF and HLE cells formed larger spheroids with negative α-feto protein staining. More CD133−/ALDHlow HLE cells survived in the exposure to cisplatin or doxorubicin than their positive counterparts (p<0.05-0.01). Moreover, CD133+/ALDHhigh HepG2, Hep3B and Huh-7 cells were positive for E-cadherin, but negative for vimentin; whereas, their CD133−/ALDHlow cells displayed an opposite expression pattern of E-cadherin and vimentin. CD133−/ALDHlow HLE, HLF and SKHep1 cells were E-cadherin-negative and vimentin-positive. In accordance, mRNA levels of Procoll-I and TGF-β1 in CD133−/ALDHlow HLE cells were one-fold higher than their positive counterparts. CONCLUSIONS: In well-differentiated hepatoma cells, CD133+/ALDHhigh or CD133+/EpCAM+ cells appear to be a CSC/progenitor subpopulation; whereas, in poorly-differentiated hepatoma cell lines which are negative for these CSC markers, EMT may be responsible for their chemoresistance. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3324.