Detection of Putative Stem-cell Markers in Invasive Ductal Carcinoma of the Breast by Immunohistochemistry: Does It Improve Prognostic/Predictive Assessments?

CD34 Protein: Its expression and function in inflammation

CD34 has spear-headed the field of basic research and clinical transplantation since the first reports of its expression on hematopoietic stem cells (HSCs). Expressed in mice, humans, rats and other species, CD34 has been used for more than 40 years as a hematopoietic stem and progenitor cell marker. It was later found that muscle satellite cells and epidermal precursors can also be identified with the aid of CD34. Despite the usefulness of CD34 as a marker of HSCs, its overall purpose in animal physiology has remained unclear. This review recaptures CD34 structure, evolutionary conservation, proposed functions, and role in lung inflammation, to describe current research findings and to provide guidance for future studies on CD34.

CD34 cells in somatic, regenerative and cancer stem cells: Developmental biology, cell therapy, and omics big data perspective

The transmembrane phosphoglycoprotein protein CD34 has conventionally been regarded as a marker for hematopoietic progenitors. Its expression on these cells has been leveraged for cell therapy applications in various hematological disorders. More recently, the expression of CD34 has also been reported on cells of nonhematopoietic origin. The list includes somatic cells such as endothelial cells, fibrocytes and interstitial cells and regenerative stem cells such as corneal keratocytes, muscle satellite cells, and muscle-derived stem cells. Furthermore, its expression on some cancer stem cells (CSCs) has also been reported. Till date, the functional roles of this molecule have been implicated in a multitude of cellular processes including cell adhesion, signal transduction, and maintenance of progenitor phenotype. However, the complete understanding about this molecule including its developmental origins, its embryonic connection, and associated functions is far from complete. Here, we review our present understanding of the structure and putative functions of the CD34 molecule based upon our literature survey. We also probed various biological databases to retrieve data related to the expression and associated molecular functions of CD34. Such information, upon synthesis, is hence likely to provide the suitability of such cells for cell therapy. Moreover, we have also covered the existing cell therapy and speculated cell therapy applications of CD34⁺ cells isolated from various lineages. We have also attempted here to speculate the role(s) of CD34 on CSCs. Finally, we discuss number of large-scale proteomics and transcriptomics studies that have been performed using CD34⁺ cells.

The Clinical Impact of Cancer Stem Cells

Patients with cancer can go though many stages in their disease, including diagnosis, recurrence, metastasis, and treatment failure. Cancer stem cells (CSCs) are a subgroup of cells within tumors that may explain the mechanism by which tumors recur and progress. CSCs can both self-renew and produce progenitor cells of more differentiated cancer cells as well as heterogeneously demonstrate resistance and the abilities to migrate and metastasize. These "stemness" characteristics are often the result of dysregulation of one or more pathways, which can be detected by various biomarkers. Although there has been considerable laboratory research conducted on CSCs, its relevance to the practicing oncologist may seem questionable. We sought to determine the clinical impact of CSCs on patients. A systematic literature search was conducted to identify analyses containing survival information based on the expression of known CSC biomarkers in any cancer. Overall, 234 survival analyses were identified, of which 82% reported that high expression of CSC biomarker(s) resulted in poor overall survival and/or disease-free survival compared with low or no expression of the biomarker. Elevated stemness biomarker levels were also associated with decreased tumor differentiation, altered TNM stage, and increased metastasis. This analysis would suggest that CSCs have a clinical impact on patients and that practicing oncologists need to start considering incorporating CSC-targeting therapies into their patients' treatment regimens. IMPLICATIONS FOR PRACTICE: Cancer stem cells (CSCs) may occur at any stage of cancer and are implicated in the occurrence of resistance, recurrence, and metastasis. A systematic literature analysis has shown that the presence of CSCs, identified via the upregulation of stemness pathway biomarkers, results in reduced survival across all cancers studied. Several CSC-targeting agents are currently approved, and several others are in clinical trials. Future treatment regimens will likely include CSC-targeting agents to enable the elimination of these holdouts to current therapies.

CD133 in Breast Cancer Cells: More than a Stem Cell Marker

Initially correlated with hematopoietic precursors, the surface expression of CD133 was also found in epithelial and nonepithelial cells from adult tissues in which it has been associated with a number of biological events. CD133 is expressed in solid tumors as well, including breast cancer, in which most of the studies have been focused on its use as a surface marker for the detection of cells with stem-like properties (i.e., cancer stem cells (CSCs)). Differently with other solid tumors, very limited and in part controversial are the information about the significance of CD133 in breast cancer, the most common malignancy among women in industrialized countries. In this review, we summarize the latest findings about the implication of CD133 in breast tumors, highlighting its role in tumor cells with a triple negative phenotype in which it directly regulates the expression of proteins involved in metastasis and drug resistance. We provide updates about the prognostic role of CD133, underlining its value as an indicator of increased malignancy of both noninvasive and invasive breast tumor cells. The molecular mechanisms at the basis of the regulation of CD133 levels in breast tumors have also been reviewed, highlighting experimental strategies capable to restrain its level that could be taken into account to reduce malignancy and/or to prevent the progression of breast tumors.

High GD2 expression defines breast cancer cells with enhanced invasiveness

INTRODUCTION

Breast cancer is the most frequently diagnosed cancer among women. Cancer stem cells (CSCs) are suggested to be responsible for tumor initiation, progression, metastasis, recurrence and drug resistance. This study was conducted to evaluate the clinical significance of GD2, a newly suggested CSC marker and two other traditional CSC markers, CD44 and CD24 in breast cancer patients.

MATERIAL AND METHODS

A total of 168 primary breast cancer tissues were evaluated in terms of GD2, CD44 and CD24 expression using tissue microarray. Then, the correlation of expression levels of these markers with patients' clinicopathological characteristics was assessed.

RESULTS

Higher GD2 expression was mainly found in patients with advanced histological grade (p = 0.02), presence of lymph node invasion (p = 0.04), larger size of tumors (p = 0.04) and older age (p = 0.04). Breast cancer samples with advanced histological grade also showed higher CD44 (p = 0.03) and CD24 expression (p = 0.05). A significant positive association was found between increased CD24 expression and lymph node involvement (p = 0.01). Furthermore, GD2-high/CD44-high/CD24-low phenotype was frequently seen in breast cancer samples with positive lymph node involvement (p = 0.05).

CONCLUSION

In summary, increased expression of GD2 may define more aggressive tumor behavior in breast cancer. GD2 can well be considered as a diagnostic and prognostic marker in breast cancer.