Identification of CD44v6(+)/CD24- breast carcinoma cells in primary human tumors by quantum dot-conjugated antibodies

The clinical significance of CD44v6 in malignant and benign primary bone tumors

BACKGROUND

The objective of this study was to assess the expression profile of CD44v6, a potential cancer stem cell marker, and its diagnostic and predictive significance in three distinct types of primary bone tumors.

METHODS

In this study, we utilized real-time qRT-PCR and immunohistochemistry to examine the gene and protein levels of CD44v6 in a total of 138 fresh bone tissues. This included 69 tumor tissues comprising osteosarcoma (N = 23), chondrosarcoma (N = 23), and GCT (N = 23), as well as 69 corresponding non-cancerous tumor margins. Furthermore, we investigated the circulating level of CD44v6 by isolating peripheral blood mononuclear cells from 92 blood samples. Among these, 69 samples were obtained from patients diagnosed with primary bone tumors, while the remaining 23 samples were from healthy donors. The primary objectives of our investigation were to assess the correlation between CD44v6 expression levels and clinic-pathological features of the patients, as well as to evaluate the diagnostic and predictive values of CD44v6 in this context.

RESULTS

In patients with osteosarcoma and chondrosarcoma tumors, both the gene and protein expression of CD44v6 were found to be significantly higher compared to the GCT group. Furthermore, the circulating level of CD44v6 was notably elevated in patients diagnosed with osteosarcoma and chondrosarcoma in comparison to the GCT group and patients with malignant tumor characteristics. Additionally, we observed a strong correlation between the gene and protein levels of CD44v6 and important tumor indicators such as tumor grade, metastasis, recurrence, and size at the tumor site. CD44v6 shows potential in differentiating patients with bone tumors from both control groups and tumor groups with severe and invasive characteristics from those with non-severe features. Importantly, the expression level of CD44v6 also demonstrated predictive value for determining tumor grade and the likelihood of recurrence.

CONCLUSION

CD44v6 is likely to play a role in the development of primary bone tumors and has the potential to serve as a diagnostic biomarker for bone cancer. However, to obtain more accurate and conclusive findings, further mechanistic investigations involving larger population samples are necessary.

Comparison of mammosphere formation from stem-like cells of normal breast, malignant primary breast tumors, and MCF-7 cell line

BACKGROUND

Mammosphere formation assay has become a versatile tool to quantify the activity of putative breast cancer stem cells in non-adherent in vitro cultures. However, optimizing the suspension culture system is crucial to establish mammosphere cultures from primary breast tumors.

METHODS

This study aimed at determining the self-renewal and sphere-forming potential of breast cancer stem-like cells derived from human primary invasive ductal carcinoma and normal breast tissue samples, and MCF-7 breast cancer cell line using an optimal suspension culture system. Mammosphere-forming efficiency of the mammospheres generated from the tissue samples and cell line were compared. We evaluated the expression of CD44⁺/CD24^-/^low and CD49f⁺/EpCAM^-/^low phenotypes in the stem-like cells by flow cytometry. CK-18, CK-19, α-SMA, and EpCAM marker expression was assessed using immunohistochemical staining.

RESULTS

Breast epithelial cells isolated from the three samples formed two-dimensional spheroids in suspension cultures. Interestingly, mammospheres formed from patient-derived primary breast tumors were enriched in breast cancer stem-like cells with the phenotype CD44⁺/CD24^-/^low and exhibited a relatively more number of large spheres when compared to the normal breast stem cells. MCF-7-derived SCs were more aggressive and resulted in the formation of a significantly higher number of spheroids. The expression of CK-18/CK-19 and α-SMA/EpCAM proteins was confirmed in breast cancer tissues.

CONCLUSIONS

Thus, the use of primary tumor specimens and breast cancer cell lines as suitable models for elucidating the breast cancer stem cell activity was validated using mammosphere culture system.

Stem cell therapy: A paradigm shift in breast cancer treatment

As per the latest Globocan statistics, the high prevalence rate of breast cancer in low- and middle-income countries has led to it becoming the most common cancer to be diagnosed, hence posing a major public health challenge. As per this data, more than 11.7% of the estimated new cancer cases in 2020 were due to breast cancer. A small but significant subpopulation of cells with self- renewing ability are present in the tumor stroma and have been given the nomenclature of cancer stem cells (CSCs). These cells display a high degree of plasticity owing to their ability to transition from the slowly cycling quiescent phase to the actively proliferating phenotype. This attribute of CSCs allows them to differentiate into various cell types having diverse functions. Breast CSCs have a pivotal role in development, metastasis, treatment resistance and relapse of breast cancers. This review focuses on the pathways regulating breast CSC maintenance and the current strategies that are being explored for directing the development of novel, targeted, therapeutic approaches for limiting and eradicating this aberrant stem cell population.

Making radiation therapy more effective in the era of precision medicine

Cancer has become a leading cause of death and constitutes an enormous burden worldwide. Radiation is a principle treatment modality used alone or in combination with other forms of therapy, with 50%–70% of cancer patients receiving radiotherapy at some point during their illness. It has been suggested that traditional radiotherapy (daily fractions of approximately 1.8–2 Gy over several weeks) might select for radioresistant tumor cell sub-populations, which, if not sterilized, give rise to local treatment failure and distant metastases. Thus, the challenge is to develop treatment strategies and schedules to eradicate the resistant subpopulation of tumorigenic cells rather than the predominant sensitive tumor cell population. With continued technological advances including enhanced conformal treatment technology, radiation oncologists can increasingly maximize the dose to tumors while sparing adjacent normal tissues, to limit toxicity and damage to the latter. Increased dose conformality also facilitates changes in treatment schedules, such as changes in dose per treatment fraction and number of treatment fractions, to enhance the therapeutic ratio. For example, the recently developed large dose per fraction treatment schedules (hypofractionation) have shown clinical advantage over conventional treatment schedules in some tumor types. Experimental studies suggest that following large acute doses of radiation, recurrent tumors, presumably sustained by the most resistant tumor cell populations, may in fact be equally or more radiation sensitive than the primary tumor. In this review, we summarize the related advances in radiotherapy, including the increasing understanding of the molecular mechanisms of radioresistance, and the targeting of these mechanisms with potent small molecule inhibitors, which may selectively sensitize tumor cells to radiation.

Engineering a Nanostructured Nucleolin-Binding Peptide for Intracellular Drug Delivery in Triple-Negative Breast Cancer Stem Cells

Five peptide ligands of four different cell surface receptors (nucleolin, CXCR1, CMKLR1, and CD44v6) have been evaluated as targeting moieties for triple-negative human breast cancers. Among them, the peptide F3, derived from phage display, promotes the fast and efficient internalization of a genetically fused green fluorescent protein (GFP) inside MDA-MB-231 cancer stem cells in a specific receptor-dependent fashion. The further engineering of this protein into the modular construct F3-RK-GFP-H6 and the subsequent construct F3-RK-PE24-H6 resulted in self-assembling polypeptides that organize as discrete and regular nanoparticles. These materials, 15-20 nm in size, show enhanced nucleolin-dependent cell penetrability. We show that the F3-RK-PE24-H6, based on the Pseudomonas aeruginosa exotoxin A (PE24) as a core functional domain, is highly cytotoxic over target cells. The combination of F3, the cationic peptide (RK)n, and the toxin domain PE24 in such unusual presentation appears as a promising approach to cell-targeted drug carriers in breast cancers and addresses selective drug delivery in otherwise difficult-to-treat triple-negative breast cancers.

Effect of c-Met and CD44v6 Expression in Resistance to Chemotherapy in Esophageal Squamous Cell Carcinoma

BACKGROUND

c-Met relies on CD44v6 for its activation and signaling in several cancer cell lines. However, the correlation of c-Met and CD44v6 expression and its biological significance in esophageal squamous cell carcinoma (ESCC) remains unknown.

METHODS

Expression of c-Met and CD44v6 was examined by immunohistochemistry (IHC) in 147 ESCC specimens. We analyzed the impact of c-Met and CD44v6 expression on clinicopathological parameters, including chemoresistance or prognosis in ESCC.

RESULTS

High expression of c-Met and CD44v6 in cancerous lesions was identified in 49.7% and 50.3% of all patients, respectively. The c-Met-high group comprised more advanced pT and pM stages than the c-Met-low group. In addition, more patients in the c-Met-high group received neoadjuvant chemotherapy (NACT) than the c-Met-low group (64.4% vs. 43.2%, P = 0.010). On the other hand, the CD44v6-high group was associated with more advanced pT/pN stages and a poorer clinical response to NACT (response rate 53.5% vs. 77.8%, P = 0.025) than the CD44v6-low group. Double-positive immunostaining of c-Met and CD44v6 was identified in 28.6% of all cases, and multivariate analysis of overall survival (OS) identified them (hazard ratio 1.79, 95% confidence interval 1.03-3.04, P = 0.038) as independent prognostic factors in addition to pN and pM stage.

CONCLUSIONS

c-Met/CD44v6 were associated with tumor progression or chemoresistance. Double-positive expression of c-Met and CD44v6 negatively impacted patient prognosis in ESCC, implying that c-Met and CD44v6 are candidates for targeted therapy in ESCC.

How can nanotechnology help the fight against breast cancer?

In this review we provide a broad overview on the use of nanotechnology for the fight against breast cancer (BC). Nowadays, detection, diagnosis, treatment, and prevention may be possible thanks to the application of nanotechnology to clinical practice. Taking into consideration the different forms of BC and the disease status, nanomaterials can be designed to meet the most forefront objectives of modern therapy and diagnosis. We have analyzed in detail three main groups of nanomaterial applications for BC treatment and diagnosis. We have identified several types of drugs successfully conjugated with nanomaterials. We have analyzed the main important imaging techniques and all nanomaterials used to help the non-invasive, early detection of the lesions. Moreover, we have examined theranostic nanomaterials as unique tools, combining imaging, detection, and therapy for BC. This state of the art review provides a useful guide depicting how nanotechnology can be used to overcome the current barriers in BC clinical practice, and how it will shape the future scenario of treatments, prevention, and diagnosis, revolutionizing the current approaches, e.g., reducing the suffering related to chemotherapy.

In vivo tracking of adipose tissue grafts with cadmium-telluride quantum dots

Background

Fat grafting, or lipofilling, represent frequent clinically used entities. The fate of these transplants is still not predictable, whereas only few animal models are available for further research. Quantum dots (QDs) are semiconductor nanocrystals which can be conveniently tracked in vivo due to photoluminescence.

Methods

Fat grafts in cluster form were labeled with cadmium-telluride (CdTe)-QD 770 and transplanted subcutaneously in a murine in vivo model. Photoluminescence levels were serially followed in vivo.

Results

Tracing of fat grafts was possible for 50 days with CdTe-QD 770. The remaining photoluminescence was 4.9%±2.5% for the QDs marked fat grafts after 30 days and 4.2%± 1.7% after 50 days. There was no significant correlation in the relative course of the tracking signal, when vital fat transplants were compared to non-vital graft controls.

Conclusions

For the first-time fat grafts were tracked in vivo with CdTe-QDs. CdTe-QDs could offer a new option for in vivo tracking of fat grafts for at least 50 days, but do not document vitality of the grafts.

ERN1 and ALPK1 inhibit differentiation of bi-potential tumor-initiating cells in human breast cancer

Cancers are heterogeneous by nature. While traditional oncology screens commonly use a single endpoint of cell viability, altering the phenotype of tumor-initiating cells may reveal alternative targets that regulate cellular growth by processes other than apoptosis or cell division. We evaluated the impact of knocking down expression of 420 kinases in bi-lineage triple-negative breast cancer (TNBC) cells that express characteristics of both myoepithelial and luminal cells. Knockdown of ERN1 or ALPK1 induces bi-lineage MDA-MB-468 cells to lose the myoepithelial marker keratin 5 but not the luminal markers keratin 8 and GATA3. In addition, these cells exhibit increased β-casein production. These changes are associated with decreased proliferation and clonogenicity in spheroid cultures and anchorage-independent growth assays. Confirmation of these assays was completed in vivo, where ERN1- or ALPK1-deficient TNBC cells are less tumorigenic. Finally, treatment with K252a, a kinase inhibitor active on ERN1, similarly impairs anchorage-independent growth of multiple breast cancer cell lines. This study supports the strategy to identify new molecular targets for types of cancer driven by cells that retain some capacity for normal differentiation to a non-tumorigenic phenotype. ERN1 and ALPK1 are potential targets for therapeutic development.

Surface Markers for the Identification of Cancer Stem Cells

Cancer stem cells have genetic and functional characteristics that can turn them resistant to standard cancer therapeutic targets. Identification of these cells is challenging and is mostly done by detecting the expression of their antigens in a group of stem cells. Currently, there are a significant number of surface markers available which can detect the cancer stem cells by directly targeting their specific antigens present in cells. These markers possess differential expression patterns and sub-localizations in cancer stem cells when compared to non-neoplastic stem cells and somatic cells. In addition to molecular markers, multiple analytical methods and techniques including functional assays, cell sorting, filtration approaches, and xenotransplantation methods are used to identify cancer stem cells. This chapter will overview the functional significance of cancer stem cells, its biological correlations, specific markers, and detection methods.

P-cadherin: a useful biomarker for axillary-based breast cancer decisions in the clinical practice

Axillary lymph node metastases represent the most powerful breast cancer prognostic factor, dictating disease staging and clinical therapeutic decisions. Nonetheless, breast cancer patients with positive lymph nodes still exhibit a heterogeneous behavior regarding disease progression. Stem-like subpopulations of cancer cells show high migratory and metastatic capacity, thus we hypothesize that breast cancer stem cell markers evaluation in metastasized lymph nodes could provide a more accurate prediction of patient's prognosis. Therefore, the expression profile of P-cadherin, CD44, and CD49f, which have been already associated to stem cell properties in breast cancer, has been evaluated by immunohistochemistry in a series of 135 primary tumors and matched axillary lymph node metastases from 135 breast cancer patients. Taking in consideration the expression of the stem cell markers only in axillary nodes, P-cadherin was the only biomarker significantly associated with poor disease-free and overall patient's survival. Moreover, although a concordant expression between primary tumors and matched lymph nodes has been found in the majority of the cases, a small but significant percentage displayed divergent expression (18.2-26.2%). Remarkably, although CD44 and CD49f changes between primary tumors and lymph node metastasis did not impact survival, the cases that were positive for P-cadherin in lymph node metastases being negative in the primary tumor, presented the worst disease-free and overall survival of the whole series. Accordingly, negative cases for this marker in the lymph nodes with positive expression in the matched breast carcinoma demonstrated a better prognosis, which overlapped with tumors that were negative in both sites. P-cadherin and CD49f gain of expression was mainly found in triple-negative carcinomas. Our results indicate for the first time that the evaluation of P-cadherin expression in lymph node metastases is an important predictor of disease outcome, being a putative valuable marker for axillary-based breast cancer decisions in the clinical practice.

Breast cancer stem-like cells: clinical implications and therapeutic strategies

Breast cancer is the most frequently diagnosed cancer in women, being also the leading cause of cancer death among female population, including in Romania. Resistance to therapy represents a major problem for cancer treatment. Current cancer treatments are both expensive and induce serious side effects; therefore ineffective therapies are both traumatic and pricy. Characterizing predictive markers that can identify high-risk patients could contribute to dedicated/personalized therapy to improve the life quality and expectancy of cancer patients. Moreover, there are some markers that govern specific tumor molecular features that can be targeted with specific therapies for those patients who are most likely to benefit. The identification of stem cells in both normal and malignant breast tissue have lead to the hypothesis that breast tumors arise from breast cancer stem-like cells (CSCs), and that these cells influence tumor’s response to therapy. CSCs have similar self-renewal properties to normal stem cells, however the balance between the signaling pathways is altered towards tumor formation In this review, we discuss the molecular aspects of breast CSCs and the controversies regarding their use in the diagnosis and treatment decision of breast cancer patients.

Let-7a regulates mammosphere formation capacity through Ras/NF-κB and Ras/MAPK/ERK pathway in breast cancer stem cells

Breast cancer stem cells (BCSCs) have the greatest potential to maintain tumorigenesis in all subtypes of tumor cells and were regarded as the key drivers of tumor. Recent evidence has demonstrated that BCSCs contributed to a high degree of resistance to therapy. However, how BCSCs self renewal and tumorigenicity are maintained remains obscure. Herein, our study illustrated that overexpression of let-7a reduced cell proliferation and mammosphere formation ability of breast cancer stem cells(BCSCs) in a KRas-dependent manner through different pathways in vitro and in vivo. To be specific, we provided the evidence that let-7a was decreased, and reversely the expression of KRas was increased with moderate expression in early stages (I/II) and high expression in advanced stages (III/IV) in breast cancer specimens. In addition, the negative correlation between let-7a and KRas was clearly observed. In vitro, we found that let-7a inhibited mammosphere-forming efficiency and the mammosphere-size via NF-κB and MAPK/ERK pathway, respectively. The inhibitory effect of let-7a on mammosphere formation efficiency and the size of mammospheres was abolished after the depletion of KRas. On the contrary, enforced expression of KRas rescued the effect of let-7a. In vivo, let-7a inhibited the growth of tumors, whereas the negative effect of let-7a was rescued after overexpressing KRas. Taken together, our findings suggested that let-7a played a tumor suppressive role in a KRas-dependent manner.

Inhibition of Tumor Growth and Metastasis in Pancreatic Cancer Models by Interference With CD44v6 Signaling

BACKGROUND & AIMS

Cancer cells with high metastatic potential and stem cell-like characteristics express the cell surface marker CD44. CD44 isoforms that include the v6 exon are co-receptors for the receptor tyrosine kinases MET and Vascular Endothelial Growth factor Receptor-2 (VEGFR-2). We studied CD44v6 signaling in several pancreatic cancer cell lines, and its role in tumor growth and metastasis in several models of pancreatic cancer.

METHODS

We analyzed the effects of v6 peptides that interfere with the co-receptor functions of CD44v6 for MET and VEGFR-2 in tumors and metastases grown from cells that express different CD44 isoforms, including CD44v6. The peptides were injected into rats with syngeneic tumors and mice with orthotopic or xenograft tumors. We also tested the effects of the peptides in mice with xenograft tumors grown from patient tumor samples and mice that express an oncogenic form of RAS and develop spontaneous pancreatic cancer (KPC mice). We measured levels of CD44v6 messenger RNA (mRNA) in pancreatic cancer tissues from 136 patients.

RESULTS

Xenograft tumors grown from human cancer cells injected with v6 peptides were smaller and formed fewer metastases in mice. The v6 peptide was more efficient than the MET inhibitor crizotinib and/or the VEGFR-2 inhibitor pazopanib in reducing xenograft tumor growth and metastasis. Injection of KPC mice with the v6 peptide increased their survival time. Injection of mice and rats bearing metastases with the v6 peptide induced regression of metastases. Higher levels of CD44v6 mRNA in human pancreatic tumor tissues were associated with increased expression of MET, tumor metastasis, and shorter patient survival times.

CONCLUSIONS

Peptide inhibitors of CD44v6 isoforms block tumor growth and metastasis in several independent models of pancreatic cancer. The v6 peptides induced regression of metastases. Levels of CD44v6 mRNA are increased, along with those of MET mRNA, in patients with metastatic pancreatic tumors, compared with nonmetastatic tumors; the increased levels correlated with shorter patient survival time.

Regulation of stem cells-related signaling pathways in response to doxorubicin treatment in Hs578T triple-negative breast cancer cells

Different molecular changes have been previously associated with therapeutic response and recurrent disease, however, the detailed mechanism of action in triple-negative breast cancer subtype remains elusive. In this study, we investigated the cellular and molecular signaling of two claudin-low triple-negative breast cancer cells to doxorubicin and docetaxel treatment. Whole human transcriptomic evaluation was used to identify the subsequent changes in gene expression, while biological effects were measured by means of proliferation and anchorage-independent growth assays. Microarray analysis revealed changes in stem cell-related signaling pathways, suggesting that doxorubicin treatment affects the balance between self-renewal and differentiation. While the treatment reduced the proliferation, aggregation and mammosphere forming ability of stem-like cells derived from Hs578T cell line, stem-like cells derived from MDA-MB-231 cells were not significantly affected. Our results suggest that claudin-low triple-negative breast cancer cells might predominantly alter stem cell-related signaling pathways to promote stem-like cells activity as an innate resistance mechanism to doxorubicin treatment.

The Role of CD44 in Disease Pathophysiology and Targeted Treatment

The cell-surface glycoprotein CD44 is involved in a multitude of important physiological functions including cell proliferation, adhesion, migration, hematopoiesis, and lymphocyte activation. The diverse physiological activity of CD44 is manifested in the pathology of a number of diseases including cancer, arthritis, bacterial and viral infections, interstitial lung disease, vascular disease, and wound healing. This diversity in biological activity is conferred by both a variety of distinct CD44 isoforms generated through complex alternative splicing, posttranslational modifications (e.g., N- and O-glycosylation), interactions with a number of different ligands, and the abundance and spatial distribution of CD44 on the cell surface. The extracellular matrix glycosaminoglycan hyaluronic acid (HA) is the principle ligand of CD44. This review focuses both CD44-hyaluronan dependent and independent CD44 signaling and the role of CD44–HA interaction in various pathophysiologies. The review also discusses recent advances in novel treatment strategies that exploit the CD44–HA interaction either for direct targeting or for drug delivery.

Development of pathological diagnostics of human kidney cancer by multiple staining using new fluorescent Fluolid dyes

New fluorescent Fluolid dyes have advantages over others such as stability against heat, dryness, and excess light. Here, we performed simultaneous immunostaining of renal tumors, clear cell renal cell carcinoma (RCC), papillary RCC, chromophobe RCC, acquired cystic disease-associated RCC (ACD-RCC), and renal angiomyolipoma (AML), with primary antibodies against Kank1, cytokeratin 7 (CK7), and CD10, which were detected with secondary antibodies labeled with Fluolid-Orange, Fluolid-Green, and Alexa Fluor 647, respectively. Kank1 was stained in normal renal tubules, papillary RCC, and ACD-RCC, and weakly or negatively in all other tumors. CK7 was positive in normal renal tubules, papillary RCC, and ACD-RCC. In contrast, CD10 was expressed in renal tubules and clear cell RCC, papillary RCC, AML, and AC-RCC, and weakly in chromophobe RCC. These results may contribute to differentiating renal tumors and subtypes of RCCs. We also examined the stability of fluorescence and found that fluorescent images of Fluolid dyes were identical between a tissue section and the same section after it was stored for almost three years at room temperature. This indicates that tissue sections can be stored at room temperature for a relatively long time after they are stained with multiple fluorescent markers, which could open a door for pathological diagnostics.

Quantitative and spatial image analysis of tumor and draining lymph nodes using immunohistochemistry and high-resolution multispectral imaging to predict metastasis

Immunohistochemistry is an essential tool for clinical and translational research laboratories. It is mostly used as a qualitative measure of morphology and cell types within tissue. We have developed a high-resolution multispectral imaging method to expand the uses of immunohistochemistry by making it quantitative. In this chapter we describe the technology, both hardware and software, that we use for this method and give examples of applications.

Nanobiosensors: role in cancer detection and diagnosis

The ability to detect many cancers at an early stage in its clinical course has the potential to improve patient outcomes in terms of morbidity and mortality. Nanosized components incorporated into existing clinical diagnostic and detection systems as well as novel nanobiosensors have demonstrated improved sensitivity and specificity compared with traditional cancer testing approaches. Nanoparticles, nanowires, nanotubes, and nanocantilevers are examples of four nanobiosensor systems that have been used experimentally in the context of detection and diagnosis of prostate, breast, pancreatic, lung, and brain cancers over the past few years. Nanobiosensors will begin to transition into clinically validated tests as experimental and engineering techniques advance. This paper presents examples of some such nanobiosensors for cancer diagnosis and detection.

Multispectral Imaging

The field of anatomic pathology has changed significantly over the last decades and, as a result of the technological developments in molecular pathology and genetics, has had increasing pressures put on it to become quantitative and to provide more information about protein expression on a cellular level in tissue sections. Multispectral imaging (MSI) has a long history as an advanced imaging modality and has been used for over a decade now in pathology to improve quantitative accuracy, enable the analysis of multicolor immunohistochemistry, and drastically reduce the impact of contrast-robbing tissue autofluorescence common in formalin-fixed, paraffin-embedded tissues. When combined with advanced software for the automated segmentation of different tissue morphologies (eg, tumor vs stroma) and cellular and subcellular segmentation, MSI can enable the per-cell quantitation of many markers simultaneously. This article covers the role that MSI has played in anatomic pathology in the analysis of formalin-fixed, paraffin-embedded tissue sections, discusses the technological aspects of why MSI has been adopted, and provides a review of the literature of the application of MSI in anatomic pathology.

Cancer stem cells: the challenges ahead

Cancer stem cells (CSCs) have been proposed as the driving force of tumorigenesis and the seeds of metastases. However, their existence and role remain a topic of intense debate. Recently, the identification of CSCs in endogenously developing mouse tumours has provided further support for this concept. Here I discuss the challenges in identifying CSCs, their dependency on a supportive niche and their role in metastasis, and propose that stemness is a flexible — rather than fixed — quality of tumour cells that can be lost and gained.

Noninvasive identification of viable cell populations in docetaxel-treated breast tumors using ferritin-based magnetic resonance imaging

Background

Cancer stem cells (CSCs) are highly tumorigenic and are responsible for tumor progression and chemoresistance. Noninvasive imaging methods for the visualization of CSC populations within tumors in vivo will have a considerable impact on the development of new CSC-targeting therapeutics.

Methodology/Principal Findings

In this study, human breast cancer stem cells (BCSCs) transduced with dual reporter genes (human ferritin heavy chain [FTH] and enhanced green fluorescence protein [EGFP]) were transplanted into NOD/SCID mice to allow noninvasive tracking of BCSC-derived populations. No changes in the properties of the BCSCs were observed due to ferritin overexpression. Magnetic resonance imaging (MRI) revealed significantly different signal intensities (R₂* values) between BCSCs and FTH-BCSCs in vitro and in vivo. In addition, distinct populations of pixels with high R₂* values were detected in docetaxel-treated FTH-BCSC tumors compared with control tumors, even before the tumor sizes changed. Histological analysis revealed that areas showing high R₂* values in docetaxel-treated FTH-BCSC tumors by MRI contained EGFP+/FTH+ viable cell populations with high percentages of CD44+/CD24− cells.

Conclusions/Significance

These findings suggest that ferritin-based MRI, which provides high spatial resolution and tissue contrast, can be used as a reliable method to identify viable cell populations derived from BCSCs after chemotherapy and may serve as a new tool to monitor the efficacy of CSC-targeting therapies in vivo.

Accurate sensitivity of quantum dots for detection of HER2 expression in breast cancer cells and tissues

Here we introduce novel optical properties and accurate sensitivity of Quantum dot (QD)-based detection system for tracking the breast cancer marker, HER2. QD525 was used to detect HER2 using home-made HER2-specific monoclonal antibodies in fixed and living HER2(+) SKBR-3 cell line and breast cancer tissues. Additionally, we compared fluorescence intensity (FI), photostability and staining index (SI) of QD525 signals at different exposure times and two excitation wavelengths with those of the conventional organic dye, FITC. Labeling signals of QD525 in both fixed and living breast cancer cells and tissue preparations were found to be significantly higher than those of FITC at 460-495 nm excitation wavelengths. Interestingly, when excited at 330-385 nm, the superiority of QD525 was more highlighted with at least 4-5 fold higher FI and SI compared to FITC. Moreover, QDs exhibited exceptional photostability during continuous illumination of cancerous cells and tissues, while FITC signal faded very quickly. QDs can be used as sensitive reporters for in situ detection of tumor markers which in turn could be viewed as a novel approach for early detection of cancers. To take comprehensive advantage of QDs, it is necessary that their optimal excitation wavelength is employed.

Drug Resistant Breast Cancer Cell Line Displays Cancer Stem Cell Phenotype and Responds Sensitively to Epigenetic Drug SAHA

Cancer stem cell (CSC) population in solid human breast tumor was identified by CD44(+)/CD24(-) phenotype, characterized by high tumorigenicity, invasiveness and drug resistance. In this study, we characterized drug resistant breast cancer cell line-MCF-7/Adr and a number of breast cancer cell lines using flow cytometry, immunofluorescence, mammosphere formation assay and migration assay, examining their CSC immunophenotypes, presence of CSC proteins, tumorigenicity in vitro and migratory rates, respectively. Our results show that MCF-7/Adr cells uniformly display CSC characteristics yet retain low migratory rate. They are also able to self-renew and differentiate under floating culture conditions. Furthermore, MCF-7/Adr is selectively sensitive to epigenetic drug, suberoylanilide hydroxamic acid (SAHA), losing drug resistance and changes morphology yet retaining CSC immunophenotypes. In conclusion, we show that resistant breast cancer cell line MCF-7/Adr demonstrates uniform CSC like characteristics and are sensitive to epigenetic drug treatment.

Downregulation of AKT reverses platinum resistance of human ovarian cancers in vitro

Platinum resistance is the most crucial problem for treatment of ovarian cancer. Increasing evidence points towards AKT overexpression as a mechanistic reason for this clinical condition. The present study evaluates the effect of overexpression and downregulation of AKT on the sensitivity to cisplatin in a platinum-resistant human ovarian cancer cell line and the corresponding platinum-sensitive parental cell line. A2780 and A2780cis ovarian cancer cell lines were stably transfected with an AKT-sense and AKT-antisense plasmid. Successful transfection was evaluated by western blot analysis. Cytotoxic effects of cisplatin were evaluated by metabolic (MTT) and clonogenicity assays as well as by FACS analysis. AKT overexpression (confirmed by western blotting) converted platinum-sensitive A2780 into platinum-resistant cells as shown by MTT assay. Importantly, platinum resistance of A2780cis cells could be reversed by downregulation of AKT, as demonstrated by MTT and clonogenicity assays and FACS analysis. Our data provide strong evidence that cisplatin resistance in ovarian cancer is mediated by AKT overexpression and can be overcome by AKT downregulation, thus, providing a rationale for clinical phase II/III studies combining AKT inhibitors with cisplatin.

In situ identification of CD44+/CD24- cancer cells in primary human breast carcinomas

Breast cancer cells with the CD44+/CD24− phenotype have been reported to be tumourigenic due to their enhanced capacity for cancer development and their self-renewal potential. The identification of human tumourigenic breast cancer cells in surgical samples has recently received increased attention due to the implications for prognosis and treatment, although limitations exist in the interpretation of these studies. To better identify the CD44+/CD24− cells in routine surgical specimens, 56 primary breast carcinoma cases were analysed by immunofluorescence and confocal microscopy, and the results were compared using flow cytometry analysis to correlate the amount and distribution of the CD44+/CD24− population with clinicopathological features. Using these methods, we showed that the breast carcinoma cells displayed four distinct sub-populations based on the expression pattern of CD44 and CD24. The CD44+/CD24− cells were found in 91% of breast tumours and constituted an average of 6.12% (range, 0.11%–21.23%) of the tumour. A strong correlation was found between the percentage of CD44+/CD24− cells in primary tumours and distant metastasis development (p = 0.0001); in addition, there was an inverse significant association with ER and PGR status (p = 0.002 and p = 0.001, respectively). No relationship was evident with tumour size (T) and regional lymph node (N) status, differentiation grade, proliferative index or HER2 status. In a multivariate analysis, the percentage of CD44+/CD24− cancer cells was an independent factor related to metastasis development (p = 0.004). Our results indicate that confocal analysis of fluorescence-labelled breast cancer samples obtained at surgery is a reliable method to identify the CD44+/CD24− tumourigenic cell population, allowing for the stratification of breast cancer patients into two groups with substantially different relapse rates on the basis of CD44+/CD24− cell percentage.

Tapping the potential of quantum dots for personalized oncology: current status and future perspectives

Cancer is one of the most serious health threats worldwide. Personalized oncology holds potential for future cancer care in clinical practice, where each patient could be delivered individualized medicine on the basis of key biological features of an individual tumor. One of the most urgent problems is to develop novel approaches that incorporate the increasing molecular information into the understanding of cancer biological behaviors for personalized oncology. Quantum dots are a heterogeneous class of engineered fluorescent nanoparticles with unique optical and chemical properties, which make them promising platforms for biomedical applications. With the unique optical properties, the utilization of quantum dot-based nanotechnology has been expanded into a wide variety of attractive biomedical applications for cancer diagnosis, monitoring, pathogenesis, treatment, molecular pathology and heterogeneity in combination with cancer biomarkers. Here, we focus on the clinical application of quantum dot-based nanotechnology in personalized oncology, covering topics on individualized cancer diagnosis and treatment by in vitro and in vivo molecular imaging technologies, and in-depth understanding of the biological behaviors of tumors from a nanotechnology perspective. In addition, the major challenges in translating quantum dot-based nanotechnology into clinical application and promising future directions in personalized oncology are also discussed.

Cancer stem cell markers in breast neoplasias: their relevance and distribution in distinct molecular subtypes

The identification and characterization of cancer stem cells might lead to more effective control of neoplastic disease, by directing therapies to the most aggressive cells. For that reason, the identification of cancer stem cells (CSCs) in breast tumours is one of the priorities in breast cancer research, which has resulted in many studies attempting to identify their presence based on the expression of specific molecular markers. In this review, we describe the main molecular markers that have been identified as being able to recognise CSCs in breast carcinomas, the major molecular pathways that regulate CSCs and their association with the different molecular subtypes.

Relationship between characteristics of CD44+/ki-67- colorectal cancer stem cells and clinicopathological characteristics in patients with colorectal cancer

AIM: To investigate the number, location, distribution and staining features of CD44⁺/ki-67^- colorectal cancer stem cells and to analyze their relation with clinicopathological characteristics in patients with colorectal carcinoma.

METHODS: Streptavidin-HRP immunohistochemical staining, double immunohistochemical staining and hematoxylin-eosin staining were performed to detect the expression of CD44 and ki-67 in 10 cases of normal mucosal tissue, 15 cases of adenoma with atypical hyperplasia, 59 cases of colorectal carcinoma, and human colon cancer cell line SW620. The number, location, distribution and staining features of CD44⁺/ki-67^- colorectal cancer stem cells were observed, and their relation with clinicopathological characteristics was analyzed.

RESULTS: The number of CD44⁺/ki-67^- tumor cells accounted for 0.1%-25.0% (average 5.82%) of all tumor cells, and the cells were mainly distributed in the sides of the basal membrane or common wall of glands. These cells had round or oval nuclei that were consistent in size, and contained deep stained chromatin and less cytoplasm. These features are consistent with those of stem cells in the intestinal crypts. The number of CD44⁺/ki-67^- tumor cells was significantly correlated with depth of cancer infiltration (χ² = 1.851, P < 0.05) and lymph node metastasis (χ² = -4.113, P < 0.01).

CONCLUSION: CD44⁺/ki-67^- are suitable specific markers for tumor stem cells and can be used for tumor stem cell isolation, targeted therapy, individualized treatment, prediction of tumor metastasis, and estimation of prognosis in patients with colorectal cancer.

Quantum dots affect expression of CD133 surface antigen in melanoma cells

BACKGROUND

In novel treatment approaches, therapeutics should be designed to target cancer stem cells (CSCs). Quantum dots (QDs) are a promising new tool in fighting against cancer. However, little is known about accumulation and cytotoxicity of QDs in CSCs.

METHODS

Accumulation and cytotoxicity of CdTe-MPA (mercaptopropionic acid) QDs in CSCs were assessed using flow cytometry and fluorescence-activated cell sorting techniques as well as a colorimetric cell viability assay.

RESULTS

We investigated the expression of two cell surface-associated glycoproteins, CD44 and CD133, in four different cancer cell lines (glioblastoma, melanoma, pancreatic, and prostate adenocarcinoma). Only the melanoma cells were positive to both markers of CD44 and CD133, whereas the other cells were only CD44-positive. The QDs accumulated to a similar extent in all subpopulations of the melanoma cells. The phenotypical response after QD treatment was compared with the response after ionizing radiation treatment. The percentage of the CD44(high-)CD133(high) subpopulation decreased from 72% to 55%-58% for both treatments. The stem-like subpopulation CD44(high)CD133(low/-) increased from 26%-28% in the untreated melanoma cells to 36%-40% for both treatments.

CONCLUSION

Treatment of melanoma cells with QDs results in an increase of stem-like cell subpopulations. The changes in phenotype distribution of the melanoma cells after the treatment with QDs are comparable with the changes after ionizing radiation.

Quantum dots and carbon nanotubes in oncology: a review on emerging theranostic applications in nanomedicine

Cancer is one of the main causes of death in the world, and according to the WHO it is projected to continue rising. Current diagnostic modalities for the detection of cancer include the use of x-rays, magnetic resonance imaging and positron emission tomography, among others. The treatment of cancer often involves the use (or combination) of chemotherapeutic drugs, radiotherapy and interventional surgery (for solid and operable tumors). The application of nanotechnology in biology and medicine is advancing rapidly. Recent evidence suggests that quantum dots (QDs) can be used to image cancer cells as they display superior fluorescent properties compared with conventional chromophores and contrast agents. In addition, carbon nanotubes (CNTs) have emerged as viable candidates for novel chemotherapeutic drug delivery-platforms. The unique photothermal properties of CNTs also allow them to be used in conjunction with near infrared radiation and lasers to thermally ablate cancer cells. Furthermore, mounting evidence indicates that it is possible to conjugate QDs to CNTs, making it possible to exploit their novel attributes in the realm of cancer theranostics (diagnostics and therapy). Here we review the current literature pertaining to the applications of QDs and CNTs in oncology, and also discuss the relevance and implications of nanomedicine in a clinical setting.

Emerging nanoproteomics approaches for disease biomarker detection: a current perspective

Availability of genome sequence of human and different pathogens has advanced proteomics research for various clinical applications. One of the prime goals of proteomics is identification and characterization of biomarkers for cancer and other fatal human diseases to aid an early diagnosis and monitor disease progression. However, rapid detection of low abundance biomarkers from the complex biological samples under clinically relevant conditions is extremely difficult, and it requires the development of ultrasensitive, robust and high-throughput technological platform. In order to overcome several technical limitations associated with sensitivity, dynamic range, detection time and multiplexing, proteomics has started integrating several emerging disciplines such as nanotechnology, which has led to the development of a novel analytical platform known as 'nanoproteomics'. Among the diverse classes of nanomaterials, the quantum dots, gold nanoparticles, carbon nanotubes and silicon nanowires are the most promising candidates for diagnostic applications. Nanoproteomics offers several advantages such as ultralow detection, short assay time, high-throughput capability and low sample consumption. In this article, we have discussed the application of nanoproteomics for biomarker discovery in various diseases with special emphasis on various types of cancer. Furthermore, we have discussed the prospects, merits and limitations of nanoproteomics.

Dueling models in head and neck tumor formation

The two leading models that have been used to explain tumor progression in head and neck squamous cell carcinoma (HNSCC) are the stochastic clonal evolution model, in which many tumor cells are individually capable of recapitulating the entire tumor mass, and the cancer stem hierarchy model, in which only rare totipotential tumor stem cells can recapitulate the tumor. In this issue, Cameron et al use cell surface marker and clonal cell analyses in combination with a xenotransplant approach to provide data that support the stochastic clonal evolution model in HNSCC. This interpretation is subject, however, to limitations inherent in the experimental approach employed. Understanding the basis of tumor progression in HNSCC as well as other cancers should be further explored because of important implications for effective treatments.

PTEN loss accelerates KrasG12D-induced pancreatic cancer development

KRAS mutations are found in ∼90% of human pancreatic ductal adenocarcinomas (PDAC). However, mice genetically engineered to express Kras(G12D) from its endogenous locus develop PDACs only after a prolonged latency, indicating that other genetic events or pathway alterations are necessary for PDAC progression. The PTEN-controlled phosphatidylinositol 3-kinase (PI3K)/AKT signaling axis is dysregulated in later stages of PDAC. To better elucidate the role of PTEN/PI3K/AKT signaling in Kras(G12D)-induced PDAC development, we crossed Pten conditional knockout mice (Pten(lox/lox)) to mice with conditional activation of Kras(G12D). The resulting compound heterozygous mutant mice showed significantly accelerated development of acinar-to-ductal metaplasia (ADM), malignant pancreatic intraepithelial neoplasia (mPanIN), and PDAC within a year. Moreover, all mice with Kras(G12D) activation and Pten homozygous deletion succumbed to cancer by 3 weeks of age. Our data support a dosage-dependent role for PTEN, and the resulting dysregulation of the PI3K/AKT signaling axis, in both PDAC initiation and progression, and shed additional light on the signaling mechanisms that lead to the development of ADM and subsequent mPanIN and pancreatic cancer.

The quantitative detection of total HER2 load by quantum dots and the identification of a new subtype of breast cancer with different 5-year prognosis

Accurate classification is fundamental for breast cancer (BC) personalized care. Current BC classification based on the either traditional morphological staging or molecular signatures seems inefficient to reveal the"true"behaviors of invasive BC evolution. An appropriate approach combining the macro- and micro-pathologic information might be more useful academically as well as clinically. Here we explore a holistic approach by integrating a key molecular prognostic indicator of BC, HER2, with quantitative determination using quantum dots (QDs)--based nanotechnology and spectral analysis, and a key macropathologic indicator, tumor size, resulting a new indicator, total HER2 load. This indicator might better reveal BC heterogeneity and new subtypes of BC with different 5-year disease-free survival compared with current methods, which could be helpful in formulating a more personalized targeted therapy for BC. Furthermore, this mode integrating macro- and micro-pathological indicators might help gain new insights into invasive BC biological behaviors.