Morphological Evaluation and Immunohistochemical Analysis of the Reparative Potential of the Buccal Fat Pad.

Background and Objectives: There are many surgical techniques for oroantral communication treatment, one of which is the buccal fat pad. Of particular interest is the high reparative potential of the buccal fat pad, which may be contributed to by the presence of mesenchymal stem cells. The purpose of this work is to evaluate the reparative potential of BFP cells using morphological and immunohistochemical examination. Materials and Methods: 30 BFP samples were provided by the Clinic of Maxillofacial and Plastic Surgery of the Russian University of Medicine (Moscow, Russia) from 28 patients. Morphological examination of 30 BFP samples was performed at the Institute of Clinical Morphology and Digital Pathology of Sechenov University. Hematoxylin-eosin, Masson trichrome staining and immunohistochemical examination were performed to detect MSCs using primary antibodies CD133, CD44 and CD10. Results: During staining with hematoxylin-eosin and Masson's trichrome, we detected adipocytes of white adipose tissue united into lobules separated by connective tissue layers, a large number of vessels of different calibers, as well as the general capsule of BFP. The thin connective tissue layers contained neurovascular bundles. Statistical processing of the results of the IHC examination of the samples using the Mann-Whitney criterion revealed that the total number of samples in which the expression of CD44, CD10 and CD133 antigens was confirmed was statistically significantly higher than the number of samples where the expression was not detected (p < 0.05). Conclusions: During the morphological study of the BFP samples, we revealed statistically significant signs of MSCs presence (p < 0.05), including in the brown fat tissue, which proves the high reparative potential of this type of tissue and can make the BFP a choice option among other autogenous donor materials when eliminating OAC and other surgical interventions in the maxillofacial region.

Triple-negative expression (ALDH1A1-/CD133-/mutant p53-) cases in lung adenocarcinoma had a good prognosis.

Cancer stem cells (CSCs) are major contributors to the malignant transformation of cells because of their capacity for self-renewal. Aldehyde dehydrogenase1A1 (ALDH1A1) and CD133 are promising candidate of CSC markers in non-small cell lung cancer (NSCLC). Furthermore, TP53 is frequently mutated in lung cancer, and the loss of its function is associated with malignant characteristics. However, the relationship between CSCs and mutant p53 in lung adenocarcinoma is not well-established. We examined the expression of ALDH1A1, CD133, and mutant p53 in lung adenocarcinoma patients and conducted a clinicopathological study. Triple-negative cases without ALDH1A1, CD133, and mutant p53 expression in lung adenocarcinoma were shown to have a much better prognosis than others. Our present results suggest that detection of CSC markers and mutant p53 by immunohistochemical staining may be effective in therapeutic strategies for lung adenocarcinoma.

SHH Expression Is Significantly Associated With Cancer Stem Cell Markers in Oral Squamous Cell Carcinoma.

BACKGROUND/AIM: Oral squamous cell carcinoma (OSCC) is a highly invasive malignancy with poor prognosis. Recent reports suggest that Sonic Hedgehog (SHH) plays a key role in tumor progression and worsens the response to therapy, possibly through an association with a cancer stem cell (CSC) phenotype. The objective of our study was to investigate the relationship between SHH expression and CSC markers in OSCC. MATERIALS AND METHODS: A total of 67 OSCC specimens were immunostained for SHH and CSC markers using specific antibodies and expression was correlated with clinicopathological parameters. RESULTS: SHH expression was significantly correlated with CD133 (p=0.026, r=0.272) and SRY-box transcription factor 2 (SOX2; p<0.001, r=0.793). SHH and SOX2 expression were associated with worse survival in OSCC (p=0.003 and p=0.003, respectively). In multivariate analysis SHH and CD44 were independent prognostic biomarkers in patients with OSCC (p=0.001 and p=0.008, respectively). CONCLUSION: Our study revealed that SHH overexpression is closely associated with CSC markers, contributing to tumor progression and worse outcomes of patients with OSCC.

Regulation of gliomagenesis and stemness through acid sensor ASIC1a.

Glioblastoma multiforme (GBM) is the most prevalent and aggressive type of adult gliomas. Despite intensive therapy including surgery, radiation, and chemotherapy, invariable tumor recurrence occurs, which suggests that glioblastoma stem cells (GSCs) render these tumors persistent. Recently, the induction of GSC differentiation has emerged as an alternative method to treat GBM, and most of the current studies aim to convert GSCs to neurons by a combination of transcriptional factors. As the tumor microenvironment is typically acidic due to increased glycolysis and consequently leads to an increased production of lactic acid in tumor cells, in the present study, the role of acid­sensing ion channel 1a (ASIC1a), an acid sensor, was explored as a tumor suppressor in gliomagenesis and stemness. The bioinformatics data from The Cancer Genome Atlas revealed that ASIC1 expression levels in GBM tumor tissues were lower than those in normal brain, and glioma patients with high ASIC1 expression had longer survival than those with low ASIC1 expression. Our immunohistochemistry data from tissue microarray revealed that ASIC1a expression was negatively associated with glioma grading. Functional studies revealed that the downregulation of ASIC1a promoted glioma cell proliferation and invasion, while upregulation of ASIC1a inhibited their proliferation and invasion. Furthermore, ASIC1a suppressed growth and proliferation of glioma cells through G1/S arrest and apoptosis induction. Mechanistically, ASIC1a negatively modulated glioma stemness via inhibition of the Notch signaling pathway and GSC markers CD133 and aldehyde dehydrogenase 1. ASIC1a is a tumor suppressor in gliomagenesis and stemness and may serve as a promising prognostic biomarker and target for GBM patients.

Autograft cellular composition and outcome in myeloma patients: Results of the prospective multicenter GOA study.

BACKGROUND: Autologous stem cell transplantation (auto-SCT) is a widely used treatment option in multiple myeloma (MM) patients. The optimal graft cellular composition is not known. STUDY DESIGN AND METHODS: Autograft cellular composition was analyzed after freezing by flow cytometry in 127 MM patients participating in a prospective multicenter study. The impact of graft cellular composition on hematologic recovery and outcome after auto-SCT was evaluated. RESULTS: A higher graft CD34+ cell content predicted faster platelet recovery after auto-SCT in both the short and long term. In patients with standard-risk cytogenetics, a higher graft CD34+ count (>2.5 × 106 /kg) was linked with shorter progression-free survival (PFS; 28 vs. 46 months, p = 0.04), but there was no difference in overall survival (OS) (p = 0.53). In a multivariate model, a higher graft CD34+ CD133+ CD38- (>0.065 × 106 /kg, p = 0.009) and NK cell count (>2.5 × 106 /kg, p = 0.026), lenalidomide maintenance and standard-risk cytogenetics predicted better PFS. In contrast, a higher CD34+ count (>2.5 × 106 /kg, p = 0.015) predicted worse PFS. A very low CD3+ cell count (≤20 × 106 /kg, p = 0.001) in the infused graft and high-risk cytogenetics remained predictive of worse OS. CONCLUSIONS: Autograft cellular composition may impact outcome in MM patients after auto-SCT. More studies are needed to define optimal graft composition.

Elevated glucose represses lysosomal and mTOR-related genes in renal epithelial cells composed of progenitor CD133+ cells.

Hyperglycemia is one of the major health concern in many parts of the world. One of the serious complications of high glucose levels is diabetic nephropathy. The preliminary microarray study performed on primary human renal tubular epithelial (hRTE) cells exposed to high glucose levels showed a significant downregulation of mTOR as well as its associated genes as well as lysosomal genes. Based on this preliminary data, the expression of various lysosomal genes as well as mTOR and its associated genes were analyzed in hRTE cells exposed to 5.5, 7.5, 11 and 16 mM glucose. The results validated the microarray analysis, which showed a significant decrease in the mRNA as well as protein expression of the selected genes as the concentration of glucose increased. Co-localization of lysosomal marker, LAMP1 with mTOR showed lower expression of mTOR as the glucose concentration increased, suggesting decrease in mTOR activity. Although the mechanism by which glucose affects the regulation of lysosomal genes is not well known, our results suggest that high levels of glucose may lead to decrease in mTOR expression causing the cells to enter an anabolic state with subsequent downregulation of lysosomal genes.

ARE STEM CELL MARKER EXPRESSION AND CD133 ANALYSIS RELEVANT TO DIFFERENTIATE COLORECTAL CANCER?

BACKGROUND: A) CD133+ cytoplasmic B) AXL+ combined C) c-MYC+ nuclear. CD133 and AXL have been described as cancer stem cell markers, and c-MYC as a key regulatory cellular mechanism in colorectal cancer (CRC). AIM: Evaluate the prognostic role of the biomarkers CD133, AXL and c-MYC and their association with clinicopathologic characteristics in colorectal adenocarcinomas and adenomas. METHODS: A total of 156 patients with UICC stage I-IV adenocarcinomas (n=122) and adenomas (n=34) were analyzed. Tissue microarrays (TMA) from primary tumors and polyps for CD133, c-MYC and AXL expression were performed and analyzed for their significance with clinicopathologic characteristics. RESULTS: Poorly differentiated adenocarcinomas and disease progression were independent risk factors for poor overall survival. The median overall survival time was 30 months. Positive CD133 expression (35.9% of all cases), particularly of right-sided CRCs (44.8% of the CD133+ cases), was negatively correlated with death in the univariate analysis, which did not reach significance in the multivariate analysis. c-MYC (15.4% of all cases) was predominantly expressed in advanced-stage patients with distant (non-pulmonary/non-hepatic) metastasis. AXL expression was found only occasionally, and predominantly dominated in adenomas, with less penetrance in high-grade dysplasia. CONCLUSIONS: CD133 expression was not associated with inferior overall survival in CRC. While AXL showed inconclusive results, c-MYC expression in primary CRCs was associated with distant metastasis.

Understanding the Biological Basis of Glioblastoma Patient-derived Spheroids.

BACKGROUND/AIM: Resistance to glioblastoma (GB) therapy is attributed to the presence of glioblastoma stem cells (GSC). Here, we defined the behavior of GSC as it pertains to proliferation, migration, and angiogenesis. MATERIALS AND METHODS: Human-derived GSC were isolated and cultured from GB patient tumors. Xenograft GSC were extracted from the xenograft tumors, and spheroids were created and compared with human GSC spheroids by flow cytometry, migration, proliferation, and angiogenesis assays. Oct3/4 and Sox2, GFAP, and Ku80 expression was assessed by immunoanalysis. RESULTS: The xenograft model showed the formation of two different tumors with distinct characteristics. Tumors formed at 2 weeks were less aggressive with well-defined margins, whereas tumors formed in 5 months were diffuse and aggressive. Expression of Oct3/4 and Sox2 was positive in both human and xenograft GSC. Positive Ku80 expression in xenograft GSC confirmed their human origin. Human and xenograft GSC migrated vigorously in collagen and Matrigel, respectively. Xenograft GSC displayed a higher rate of migration and invasion than human GSC. CONCLUSION: Human GSC were more aggressive in growth and proliferation than xenograft GSC, while xenograft GSC had increased invasion and migration compared to human GSC. A simple in vitro spheroid system for GSC provides a superior platform for the development of precision medicine in the treatment of GB.

Targeting cancer stem cells by disulfiram and copper sensitizes radioresistant chondrosarcoma to radiation.

Overcoming the radiosensitivity of chondrosarcoma (CS), the second most common primary bone tumor, is needed. Radioresistance is attributed to cancer stem cells (CSCs) in many malignancies. Disulfiram (DSF), an FDA-approved anti-alcoholism drug, complexed with Cu (DSF/Cu) can radiosensitize epithelial CSCs. This prompted us to investigate the radiosensitizing effect of DSF/Cu on CS CSCs (CCSCs). The radiosensitizing effects of DSF/Cu on CCSCs were investigated in vitro using cell lines SW1353 and CS-1. Stemness was identified independently by flow cytometry for CCSCs (ALDH+CD133+), sphere-forming ability, and Western blot analysis of stemness gene protein expression. The radiosensitizing effect of DSF/Cu was studied in an orthotopic CS xenograft mouse model by analyzing xenograft growth and residual xenografts for stemness. CCSCs were found to be resistant to single-dose (IR) and fractionated irradiation (FIR). IR and FIR increased CS stemness. Combined with DSF/Cu in vitro and in vivo, IR and FIR eliminated CS stemness. RT + DSF/Cu was safer and more effective than either RT ± DSF in inhibiting growth of orthotopic CS xenografts. In conclusion, DSF/Cu radiosensitizes CCSCs. These results can be translated into clinical trials for CS patients requiring RT for improved outcomes.

Human CD34-negative hematopoietic stem cells: The current understanding of their biological nature.

Hematopoietic stem cell (HSC) heterogeneity and hierarchy are a current topic of interest, having major implications for clinical HSC transplantation and basic research on human HSCs. It was long believed that the most primitive HSCs in mammals, including mice and humans, were CD34 antigen positive (CD34+). However, 2 decades ago, it was reported that murine long-term multilineage reconstituting HSCs were lineage marker negative (Lin-, i.e., c-kit+Sca-1+CD34low/-), known as CD34low/- KSL cells. In contrast, human CD34- HSCs, a counterpart of murine CD34low/- KSL cells, were hard to identify for a long time mainly because of their rarity. We previously identified very primitive human cord blood (CB)-derived CD34- severe combined immunodeficiency (SCID)-repopulating cells (SRCs) using the intra-bone marrow injection method and proposed the new concept that CD34- SRCs (HSCs) reside at the apex of the human HSC hierarchy. Through a series of studies, we identified two positive/enrichment markers: CD133 and GPI-80. The combination of these two markers enabled the development of an ultrahigh-resolution purification method for CD34- as well as CD34+ HSCs and the successful purification of both HSCs at the single-cell level. Cell population purity is a crucial prerequisite for reliable biological and molecular analyses. Clonal analyses of highly purified human CD34- HSCs have revealed their potent megakaryocyte/erythrocyte differentiation potential. Based on these observations, we propose a revised road map for the commitment of human CB-derived CD34- HSCs. This review updates the current understanding of the stem cell nature of human CB-derived primitive CD34- as well as CD34+ HSCs.

Enrichment and Transcriptional Characterization of Stem Cells Isolated from Human Glioblastoma Cell Lines.

Glioblastomas (GBM) are the most frequent and aggressive brain tumors due to their recurrence and resistance to current therapies. These characteristics are associated with the presence of glioma stem cells (GSCs), mainly identified by the detection of the membrane antigens CD133 and CD15. The main source of GSCs has been biopsies of tumors. However, alternatives are sought from cell lines because more homogeneous populations can be obtained with high yields. This chapter describes a method for the enrichment and characterization of GSCs from cell lines derived from human GBM by selective culture with serum-free neural stem cell medium and growth factors. The technique offers alternatives for the enrichment and characterization of GSCs, that could contribute to a better understanding of the biology of GBMs.

Gold nanostar-enhanced electrochemiluminescence immunosensor for highly sensitive detection of cancer stem cells using CD133 membrane biomarker.

Gold nanostars (AuNSs) demonstrate an intense electromagnetic field around tip of branches. In this research, we employed AuNSs-enhanced electrochemiluminescence (ECL) emission from graphitic carbon nitride nanosheets (g-CN nanosheets) to detect CD133 peptide as a cancer stem cell membrane biomarker. In this biosensor, the g-CN nanosheets were decorated with AuNSs (AuNSs@g-CN nanosheets). AuNSs@g-CN nanosheets exhibited strong and stable cathodic ECL emission compared to that of pure g-CN nanosheets. The ECL intensity from the AuNSs@g-CN nanosheets was over 30% higher than that of spherical gold nanoparticles (spherical AuNPs) decorated g-CN nanosheets. The additional ECL enhancement of AuNSs was due to the localized surface plasmon resonance (LSPR) effect located around multiple branch tips of AuNSs. The RSD of ECL curves intensities, obtained from successive potential scans for 10 cycles, were less than 4%, indicating the superior stability of the AuNSs@g-CN nanosheets. Under optimum conditions, the ECL intensity of GCE/AuNSs@g-CN nanosheets/anti-CD133 decreased linearly with CD133 peptide concentration in the range of 0.05-100 ng mL-1. The LOD achieved was 0.257 ng mL-1 (S/N = 3). The applicability of the designed biosensor in real samples was examined through the determination of CD133 peptide in spiked serum samples, from which satisfactory results were obtained.

Drug resistance gene expression and chemotherapy sensitivity detection in Chinese women with different molecular subtypes of breast cancer.

Objective: The aim of the study was to identify specific chemosensitivity drugs for various molecular subtypes of breast tumors in Chinese women, by detecting the expression of drug resistance genes and by using the drug sensitivity test on different molecular subtypes of breast cancers. Methods: The expression of drug resistance genes including Topo II, GST-π, P-gp, LRP, and CD133 were detected with immunohistochemistry in a tissue microarray. Drug sensitivity tests included those for paclitaxel, epirubicin, carboplatin, vinorelbine, and fluorouracil and were conducted on primary cancer tissue cells and cell lines, including the T47D, BT-474, and MDA-MB-231 cells and human breast cancer xenografts in nude mice. Results: The different drug resistant genes Topo II, GST-π, P-gp, and LRP were differentially expressed among different molecular subtypes of breast cancers (P < 0.05). Positive expression of CD133 was highest in basal-like breast cancer (P < 0.05). Kaplan-Meier survival analysis showed that positive expressions of Topo II and CD133 both correlated with shorter disease-free survival (DFS) (P < 0.05) and overall survival (P < 0.05), and positive expression of LRP correlated only with shorter DFS (P < 0.05). BT-474 showed chemosensitivity to paclitaxel and epirubicin, while MDA-MB-231 showed chemosensitivities to paclitaxel, epirubicin, carboplatin, and fluorouracil (T/C ≤ 50%). The basal-like and HER2+ breast cancer primary cells showed chemosensitivities to paclitaxel and epirubicin with significant differences compared with luminal breast cancer primary cells (P < 0.05). Conclusions: The differential expression of drug resistance genes and the differential chemosensitivities of drugs in different molecular subtype of breast cancers suggested that individual treatment should be given for each type of breast cancer.

Enrichment of cancer-initiating cells from colon cancer cells through porous polymeric membranes by a membrane filtration method.

Cancer-initiating cells (CICs) or cancer stem cells (CSCs) are primarily responsible for tumor initiation, growth, and metastasis and represent a few percent of the total tumor cell population. We designed a membrane filtration protocol to enrich CICs (CSCs) from the LoVo colon cancer cell line via nylon mesh filter membranes with 11 and 20 µm pore sizes and poly(lactide-co-glycolic acid)/silk screen (PLGA/silk screen) porous membranes (pore sizes of 20-30 µm). The colon cancer cell solution was filtered through the membranes to obtain a permeate solution. Subsequently, the cell culture medium was filtered through the membranes to collect the recovery solution where the cells attached to the membranes were rinsed off into the recovery solution. Then, the membranes were cultivated in the cultivation medium to collect the migrated cells from the membranes. The cells migrated from any membrane had higher expression of the CSC surface markers CD44 and CD133, had higher colony formation levels, and produced more carcinoembryonic antigen (CEA) than the colon cancer cells cultivated on conventional tissue culture plates (control). We established a method to enrich the CICs (CSCs) of colon cancer cells from migrated cells through porous polymeric membranes by the membrane filtration protocol developed in this study.

[Effectiveness of intraperitoneal chemotherapy for t4 colon cancer]. / Effektivnost' vnutribryushnoi khimioterapii pri rake obodochnoi kishki T4.

OBJECTIVE: To determine the effect of intraperitoneal chemotherapy (IPC) with mitomycin C on expression of intraperitoneal cancer cells markers in patients with T4 colon cancer. MATERIAL AND METHODS: For the period from January 2019 to April 2020, 65 patients with T4 colon cancer were included in prospective comparative study. There were 46 patients in the main group and 19 patients in the control group. In the main group, surgical procedure was followed by IPC with mitomycin C. No IPC was performed in the control group. An effectiveness of IPC was evaluated using CD133, CD24, CD26, CD44, CD184 markers expression in peritoneal lavages. RESULTS: Significant between-group differences were observed for CD133 (p=0.0168), CD24 (p=0.0455) and CD44 (p=0.0012). There was a tendency to decrease in the level of CD184 expression in both groups in the second lavage (p=0.0605). CONCLUSION: IPC in patients with T4 colon cancer can reduce the expression and proliferative potential of free cancer cells.

Molecular analyses of glioblastoma stem-like cells and glioblastoma tissue.

Glioblastoma is a common, malignant brain tumor whose disease incidence increases with age. Glioblastoma stem-like cells (GSCs) are thought to contribute to cancer therapy resistance and to be responsible for tumor initiation, maintenance, and recurrence. This study utilizes both SNP array and gene expression profiling to better understand GSCs and their relation to malignant disease. Peripheral blood and primary glioblastoma tumor tissue were obtained from patients, the latter of which was used to generate GSCs as well as a CD133pos./CD15pos. subpopulation. The stem cell features of GSCs were confirmed via the immunofluorescent expression of Nestin, SOX2, and CD133. Both tumor tissue and the isolated primary cells shared unique abnormal genomic characteristics, including a gain of chromosome 7 as well as either a partial or complete loss of chromosome 10. Individual genomic differences were also observed, including the loss of chromosome 4 and segmental uniparental disomy of 9p24.3→p21.3 in GSCs. Gene expression profiling revealed 418 genes upregulated in tumor tissue vs. CD133pos./CD15pos. cells and 44 genes upregulated in CD133pos./CD15pos. cells vs. tumor tissue. Pathway analyses demonstrated that upregulated genes in CD133pos./CD15pos. cells are relevant to cell cycle processes and cancerogenesis. In summary, we detected previously undescribed genomic and gene expression differences when comparing tumor tissue and isolated stem-like subpopulations.

Prognostic significance of branched-chain amino acid transferase 1 and CD133 in triple-negative breast cancer.

BACKGROUND: Previous studies have shown that branched-chain amino acid transferase 1 (BCAT1) is associated with tumour progression in triple-negative breast cancer (TNBC). Furthermore, CD133 has emerged as a novel cancer stem cell marker for indicating tumour progression. However, the prognostic significance of these two markers remains to be verified. This study was conducted to investigate the correlation between BCAT1 and CD133 expression and clinicopathological features, as well as the prognosis of patients with TNBC. METHODS: The study cohort included 291 patients with TNBC. Tissue microarrays were constructed for both cancer and normal tissues. The expression of BCAT1 and CD133 was detected by immunohistochemical staining, and the levels were evaluated using an H-scoring system. Cut-off points for BCAT1 and CD133 expression were determined using receiver operating characteristic curves. RESULTS: The median follow-up time for the study participants was 68.73 months (range: 1.37-103.6 months). The 5-year disease-free survival (DFS) and overall survival (OS) rates of the 291 patients with TNBC were 72.51 and 82.47%, respectively. Higher levels of BCAT1 and CD133 expression independently indicated shorter DFS and OS. High levels of both BCAT1 and CD133 expression were detected in 36 (12.37%) patients, who had significantly shorter DFS and OS (both P < 0.001) compared to other patients. CONCLUSION: BCAT1 and CD133 can be considered as biomarkers with prognostic significance for TNBC.

Expression of the cancer stem cell marker SSEA1 is associated with poor survival in metastatic high-grade serous carcinoma.

The objective of the present study was to perform a quantitative analysis of cancer stem cell (CSC) marker expression in ovarian carcinoma effusions. The clinical role of SSEA1 in metastatic high-grade serous carcinoma (HGSC) was additionally analyzed. CD133, Nanog, SOX2, Oct3/4, SSEA1, and SSEA4 protein expressions were quantitatively analyzed using flow cytometry (FCM) in 24 effusions. SSEA1 expression by immunohistochemistry was analyzed in 384 HGSC effusions. Highly variable expression of CSC markers by FCM was observed, ranging from 0 to 78% of Ber-EP4-positive cells in the case of CD133, with the largest number of negative specimens seen for SSEA4. SSEA1 expression by immunohistochemistry was found in HGSC cells in 336/384 (89%) effusions, most commonly focally (< 5% of cells). SSEA1 was overexpressed in post-chemotherapy disease recurrence specimens compared with chemo-naïve HGSC effusions tapped at diagnosis (p = 0.029). In univariate survival analysis, higher SSEA1 expression was significantly associated with poor overall survival (p = 0.047) and progression-free survival (p = 0.018), though it failed to retain its prognostic role in Cox multivariate survival analysis in which it was analyzed with clinical parameters (p = 0.059 and p = 0.111 for overall and progression-free survival, respectively). In conclusion, CSC markers are variably expressed in ovarian carcinoma effusions. SSEA1 expression is associated with disease progression and poor survival in metastatic HGSC. Silencing this molecule may have therapeutic relevance in this cancer.

CD133 expressionand clinicopathologic significance in benign and malignant breast lesions.

BACKGROUND/OBJECTIVE: CD133 is the molecular marker of normal stem cells and progenitor cells and also confirmed as a marker for cancer stem cells in various tumors. The aim of this study is to examine the expression of CD133 and assess its clinicopathologic significance in benign and malignant breast lesions. METHODS: We analyzed the distribution of CD133 positive cells in breast usual ductal hyperplasia, atypical ductal hyperplasia (ADH), breast ductal carcinoma in situ (DCIS), and invasive breast carcinomas. We then explored the relationship between the CD133 expression and clinicopathologic features using immuno-histochemical staining. RESULTS: We found that CD133 is not expressed in the cells of normal breast tissue, but the expression rate increased with progression of lesions from usual hyperplasia, through atypical ductal hyperplasia, ductal carcinoma in situ and invasive carcinoma. The positive expression rate of CD133 in breast invasive ductal carcinoma correlated to histological grade, cancer stage, nodal status, metastasis, recurrence, event-free survival and overall survival. There was no significant correlation between CD133 expression and factors such as age, postmenopausal status, histological type, tumor size, estrogen receptor, progesterone receptor and human epidermal growth factor receptor-2 expression. CONCLUSION: CD133 may play an important role in the occurrence and development of breast cancer. CD133 positive breast cancer cells are closely related to invasiveness and its expression may predict a poor prognosis.