Breast cancer stem cells: treatment resistance and therapeutic opportunities

Evaluation of the effect of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc radiotherapy (VMAT) techniques on survival response in cell lines with a new radiobiological modeling

BACKGROUND

The optimal radiobiological model, which assesses the biological effects of novel radiotherapy techniques that concurrently modify multiple physical factors, has not yet been defined. This study aimed to investigate the impact of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) on cellular response in head and neck cancer and melanoma models.

METHODS

Clonogenic analysis, DNA double-strand break analysis, apoptosis, and cell cycle analysis were performed on cancer stem cell models, cancer models, and normal tissue cell models to assess radiation sensitivity.

RESULTS

The segmented radiation approach used in IMRT applications enhanced radiosensitivity and cytotoxicity in the cancer models, while changes in dose rate had varying effects on cytotoxicity depending on the tumor cell type. VMAT increased cellular resistance, favoring treatment outcomes.

CONCLUSIONS

The biological processes were influenced differently by dose rate, IMRT, and VMAT depending on the tumor cell type. The selection of the most appropriate technique is crucial in representing new radiotherapy approaches. The obtained data can serve as a model to address clinical questions in daily practice. The integration of non-standard outcomes with standard applications should be considered in clinical settings.

CDK4: a master regulator of the cell cycle and its role in cancer

The cell cycle is regulated in part by cyclins and their associated serine/threonine cyclin-dependent kinases, or CDKs. CDK4, in conjunction with the D-type cyclins, mediates progression through the G₁ phase when the cell prepares to initiate DNA synthesis. Although Cdk4-null mutant mice are viable and cell proliferation is not significantly affected in vitro due to compensatory roles played by other CDKs, this gene plays a key role in mammalian development and cancer. This review discusses the role that CDK4 plays in cell cycle control, normal development and tumorigenesis as well as the current status and utility of approved small molecule CDK4/6 inhibitors that are currently being used as cancer therapeutics.

Growth dynamics of breast cancer stem cells: effects of self-feedback and EMT mechanisms

Breast cancer stem cells (BCSCs) with the ability to self-renew and differentiate have been identified in primary breast cancer tissues and cell lines. The BCSCs are often resistant to traditional radiation and/or chemotherapies. Previous studies have also shown that successful therapy must eradicate cancer stem cells. The purpose of this paper is to develop a mathematical model with self-feedback mechanism to illustrate the issues regarding the difficulties of absolutely eliminating a breast cancer. In addition, we introduce the mechanism of the epithelial-mesenchymal transition (EMT) to investigate the influence of EMT on the effects of breast cancer growth and treatment. Results indicate that the EMT mechanism facilitates the growth of breast cancer and makes breast cancer more difficult to be cured. Therefore, targeting the signals involved in EMT can halt tumor progression in breast cancer. Finally, we apply the experimental data to carry out numerical simulations and validate our theoretical conclusions.

Anticancer properties of novel zinc oxide quantum dot nanoparticles against breast cancer stem-like cells

Cancer stem cells (CSCs) play an essential role in cancer development, metastasis, relapse, and resistance to treatment. In this article, the effects of three synthesized ZnO nanofluids on proliferation, apoptosis, and stemness markers of breast cancer stem-like cells are reported. The antiproliferative and apoptotic properties of ZnO nanoparticles were evaluated on breast cancer stem-like cell-enriched mammospheres by MTS assay and flowcytometry, respectively. The expression of stemness markers, including WNT1, NOTCH1, β-catenin, CXCR4, SOX2, and ALDH3A1 was assessed by real-time PCR. Western blotting was used to analyze the phosphorylation of Janus kinase 2 (JAK2) and Signal Transducer and Activator of Transcription 3 (STAT3). Markers of stemness were significantly decreased by ZnO nanofluids, especially sample (c) with code ZnO-148 with a different order of addition of polyethylene glycol solution at the end of formulation, which considerably decreased all the markers compared to the controls. All the studied ZnO nanofluids considerably reduced viability and induced apoptosis of spheroidal and parental cells, with ZnO-148 presenting the most effective activity. Using CD95L as a death ligand and ZB4 as an extrinsic apoptotic pathway blocker, it was revealed that none of the nanoparticles induced apoptosis through the extrinsic pathway. Results also showed a marked inhibition of the JAK/STAT pathway by ZnO nanoparticles; confirmed by downregulation of Mcl-1 and Bcl-XL expression. The present data demonstrated that ZnO nanofluids could combat breast CSCs via decreasing stemness markers, stimulating apoptosis, and suppressing JAK/STAT activity.

Parathyroid hormone‐related protein inhibition blocks triple‐negative breast cancer expansion in bone through epithelial to mesenchymal transition reversal

Parathyroid hormone‐related protein (PTHrP) plays a major role in skeletal metastasis but its action mechanism has not been fully defined. We previously demonstrated the crucial importance of PTHrP in promoting mammary tumor initiation, growth, and metastasis in a mouse model with a mammary epithelium‐targeted Pthlh gene ablation. We demonstrate here a novel mechanism for bone invasion involving PTHrP induction of epithelial to mesenchymal transition (EMT) and cancer stem cells (CSCs) regulation. Clustered regularly interspaced short palindromic repeats (CRISPR)‐mediated Pthlh gene ablation was used to study EMT markers, phenotype, and invasiveness in two triple‐negative breast cancer (TNBC) cell types (established MDA‐MB‐231 and patient‐derived PT‐TNBC cells). In vitro, Pthlh ablation in TNBC cells reduced EMT markers, mammosphere‐forming ability, and CD44^high/CD24^low cells ratio. In vivo, cells were injected intratibially into athymic nude mice, and therapeutic treatment with our anti‐PTHrP blocking antibody was started 2 weeks after skeletal tumors were established. In vivo, compared to control, lytic bone lesion from Pthlh ‐ablated cells decreased significantly over 2 weeks by 27% for MDA‐MB‐231 and by 75% for PT‐TNBC‐injected mice (p < 0.001). Micro‐CT (μCT) analyses also showed that antibody therapy reduced bone lytic volume loss by 52% and 48% for non‐ablated MDA‐MB‐231 and PT‐TNBC, respectively (p < 0.05). Antibody therapy reduced skeletal tumor burden by 45% and 87% for non‐ablated MDA‐MB‐231 and PT‐TNBC, respectively (p < 0.002) and caused a significant decrease of CSC/EMT markers ALDH1, vimentin, and Slug, and an increase in E‐cadherin in bone lesions. We conclude that PTHrP is a targetable EMT molecular driver and suggest that its pharmacological blockade can provide a potential therapeutic approach against established TNBC‐derived skeletal lesions. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Mesenchymal stem cells in cancer progression and anticancer therapeutic resistance

Increasing evidence indicates that the tumor microenvironment appears to play an increasingly important role in cancer progression and therapeutic resistance. Several types of cells within the tumor stroma had distinct impacts on cancer progression, either promoting or inhibiting cancer cell growth. Mesenchymal stem cells (MSCs) are a distinct type of cells that is linked to tumor development. MSCs are recognized for homing to tumor locations and promoting or inhibiting cancer cell proliferation, angiogenesis and metastasis. Moreover, emerging studies suggests that MSCs are also involved in therapeutic resistance. In this review, we analyzed the existing researches and elaborate on the functions of MSCs in cancer progression and anticancer therapeutic resistance, demonstrating that MSCs may be a viable cancer therapeutic target.

Genome-wide CRISPR/Cas9 screening identifies CARHSP1 responsible for radiation resistance in glioblastoma

Glioblastomas (GBM) is the most common primary malignant brain tumor, and radiotherapy plays a critical role in its therapeutic management. Unfortunately, the development of radioresistance is universal. Here, we identified calcium-regulated heat-stable protein 1 (CARHSP1) as a critical driver for radioresistance utilizing genome-wide CRISPR activation screening. This is a protein with a cold-shock domain (CSD)-containing that is highly similar to cold-shock proteins. CARHSP1 mRNA level was upregulated in irradiation-resistant GBM cells and knockdown of CARHSP1 sensitized GBM cells to radiotherapy. The high expression of CARHSP1 upon radiation might mediate radioresistance by activating the inflammatory signaling pathway. More importantly, patients with high levels of CARHSP1 had poorer survival when treated with radiotherapy. Collectively, our findings suggested that targeting the CARHSP1/TNF-α inflammatory signaling activation induced by radiotherapy might directly affect radioresistance and present an attractive therapeutic target for GBM, particularly for patients with high levels of CARHSP1.

Cancer Stem Cells Are Possible Key Players in Regulating Anti-Tumor Immune Responses: The Role of Immunomodulating Molecules and MicroRNAs

Simple Summary

This review provides a critical overview of the state of the art of the characterization of the immunological profile of a rare component of the tumors, denominated cancer stem cells (CSCs) or cancer initiating cells (CICs). These cells are endowed with the ability to form and propagate tumors and resistance to therapies, including the most innovative approaches. These investigations contribute to understanding the mechanisms regulating the interaction of CSCs/CICs with the immune system and identifying novel therapeutic approaches to render these cells visible and susceptible to immune responses.

Abstract

Cancer cells endowed with stemness properties and representing a rare population of cells within malignant lesions have been isolated from tumors with different histological origins. These cells, denominated as cancer stem cells (CSCs) or cancer initiating cells (CICs), are responsible for tumor initiation, progression and resistance to therapies, including immunotherapy. The dynamic crosstalk of CSCs/CICs with the tumor microenvironment orchestrates their fate and plasticity as well as their immunogenicity. CSCs/CICs, as observed in multiple studies, display either the aberrant expression of immunomodulatory molecules or suboptimal levels of molecules involved in antigen processing and presentation, leading to immune evasion. MicroRNAs (miRNAs) that can regulate either stemness properties or their immunological profile, with in some cases dual functions, can provide insights into these mechanisms and possible interventions to develop novel therapeutic strategies targeting CSCs/CICs and reverting their immunogenicity. In this review, we provide an overview of the immunoregulatory features of CSCs/CICs including miRNA profiles involved in the regulation of the interplay between stemness and immunological properties.

Interleukins as Mediators of the Tumor Cell-Bone Cell Crosstalk during the Initiation of Breast Cancer Bone Metastasis

Patients with advanced breast cancer are at high risk of developing bone metastasis. Despite treatment advances for primary breast cancer, metastatic bone disease remains incurable with a low relative survival. Hence, new therapeutic approaches are required to improve survival and treatment outcome for these patients. Bone is among the most frequent sites of metastasis in breast cancer. Once in the bone, disseminated tumor cells can acquire a dormant state and remain quiescent until they resume growth, resulting in overt metastasis. At this stage the disease is characterized by excessive, osteoclast-mediated osteolysis. Cells of the bone microenvironment including osteoclasts, osteoblasts and endothelial cells contribute to the initiation and progression of breast cancer bone metastasis. Direct cell-to-cell contact as well as soluble factors regulate the crosstalk between disseminated breast cancer cells and bone cells. In this complex signaling network interleukins (ILs) have been identified as key regulators since both, cancer cells and bone cells secrete ILs and express corresponding receptors. ILs regulate differentiation and function of bone cells, with several ILs being reported to act pro-osteoclastogenic. Consistently, the expression level of ILs (e.g., in serum) has been associated with poor prognosis in breast cancer. In this review we discuss the role of the most extensively investigated ILs during the establishment of breast cancer bone metastasis and highlight their potential as therapeutic targets in preventing metastatic outgrowth in bone.

High B3GALT5 expression confers poor clinical outcome and contributes to tumor progression and metastasis in breast cancer

BACKGROUND

Existence of breast cancer stem cells (BCSCs) is implicated in disease relapse, metastasis, and resistance of treatment. β1,3-Galactosyltransferase 5 (B3GALT5) has been shown to be a pro-survival marker for BCSCs. However, little is known about the prognostic significance of B3GALT5 in breast cancer.

METHODS

Paired tissues (tumor part and adjacent non-tumor part) from a cohort of 202 women with breast cancer were used to determine the expression levels of B3GALT5 mRNA by qRT-PCR. Kaplan-Meier and multivariable Cox proportional hazard models were used to assess survival differences in terms of relapse-free survival (RFS) and overall survival (OS). Both breast cancer cells and cancer stem cells (BCSCs) were used to see the in vitro effects of knockdown or overexpression of B3GALT5 on cell migration, invasion, and epithelial-to-mesenchymal transition (EMT). A patient-derived xenograft (PDX) model was used to see the in vivo effects of knockdown of B3GALT5 in BCSCs on tumor growth and metastasis.

RESULTS

Higher expression of B3GALT5 in 202 breast cancer tissues, especially in adjacent non-tumor tissue, correlated with poor clinical outcomes including shorter OS and RFS in all patients, especially those with early stage breast cancer. In vitro studies showed B3GALT5 could enhance cell migration, invasion, mammosphere formation, and EMT. Of note, B3GALT5 upregulated the expression of β-catenin and EMT activator zinc finger E-box binding homeobox 1 (ZEB1) pathway in BCSCs. In vivo studies showed B3GALT5 expression in BCSCs is critical for not only tumor growth but also lymph node and lung metastasis in PDX mice.

CONCLUSION

Our results demonstrated the value of B3GALT5 as a prognostic marker of breast cancer, especially among the early stage patients, and its crucial roles in regulating EMT, cell migration, and stemness thereby promoting breast cancer progression.

Eucannabinolide, a novel sesquiterpene lactone, suppresses the growth, metastasis and BCSCS-like traits of TNBC via inactivation of STAT3

Signal transducer and activator of transcription 3 (STAT3) is an important therapeutic target to triple negative breast cancer (TNBC) treatment. In the present study, we aim to investigate the potential activity of Eucannabinolide (Euc), a novel sesquiterpene lactone separated from Eupatorium cannabinum Linn. against TNBC by targeting STAT3 and expect that Euc will be developed as an inhibitor of STAT3 in the treatment of TNBC. We found that Euc effectively suppressed STAT3 activation at tyrosine 705, inhibited its translocation to nucleus, and decreased its DNA binding capacity. Moreover, introduction of STAT3-short hairpin RNAs or STAT3 inhibitor S3I-201 attenuates the Euc-induced inhibition of cell viability. And, Euc inhibited cell viability, proliferation, metastasis and breast cancer stem cell-like traits but did not induce cytotoxicity in human mammary epithelial cells. The in vivo study similarly demonstrated that administration of Euc inhibited the growth of xenograft tumors and impaired tumor metastasis of a lung metastasis model. The above phenomena were associated with STAT3 dysfunction induced by Euc. In conclusion, Euc elicits the effects of anti-proliferation, anti-metastasis and anti-breast cancer stem cell-like traits in TNBC via targeting STAT3. These data highlight that development of Euc as a STAT3 inhibitor may offer a promising therapeutic strategy for TNBC.

Suppression of Rotenone-Treated Human Breast Cancer Stem Cell Survival Using Survivin Inhibitor YM155 is Associated to Oxidative Stress Modulation

Background:

Despite recent progress in molecular-targeted therapies, breast cancer remains the primary leading cause of cancer related death among women worldwide. Breast cancer stem cells (BCSCs) are believed to be responsible for therapy resistance and cancer recurrence. We recently demonstrated that human BCSCs (CD24-/CD44+) could survive better than their counterpart non-BCSCs (CD24-/CD44-) when treated with rotenone, possibly due to lower levels of reactive oxygen species (ROS) production, high expression of antioxidant manganese superoxide dismutase (MnSOD), and anti-apoptotic survivin. The aim of this study was to verify the role of survivin on human BCSCs survival under oxidative stress modulation by suppressing its expression using YM155, a survivin inhibitor.

Methods:

Human BCSCs (ALDH+ cells) were treated with YM155 for 24 h prior to treatment with rotenone for a further 6 h. We determined intracellular superoxide levels were determined using dihydroethidium assay, survivin and MnSOD expression using qRT-PCR, survivin protein level using ELISA, as well as cell viability using trypan blue exclusion and acridine orange/ethidium bromide apoptosis assay.

Results:

Suppression of survivin expression using YM155 could reduce the survival of rotenone-treated BCSCs, which may be associated with oxidative stress modulation, as shown by increased ROS levels and decreased MnSOD expression. We confirm that survivin is responsible for maintaining BCSCs survival under oxidative stress modulation. Furthermore, YM155 could modulate oxidative stress in BCSCs by reducing MnSOD expression and increasing ROS levels.

Conclusion:

YM155 treatment could be used to overcome BCSCs resistance to oxidative stress-based anticancer therapies.

Nanoparticles in Targeted Alpha Therapy

Recent advances in the field of nanotechnology application in nuclear medicine offer the promise of better therapeutic options. In recent years, increasing efforts have been made on developing nanoconstructs that can be used as carriers for immobilising alpha (α)-emitters in targeted drug delivery. In this publication, we provide a comprehensive overview of available information on functional nanomaterials for targeted alpha therapy. The first section describes why nanoconstructs are used for the synthesis of α-emitting radiopharmaceuticals. Next, we present the synthesis and summarise the recent studies demonstrating therapeutic applications of α-emitting labelled radiobioconjugates in targeted therapy. Finally, future prospects and the emerging possibility of therapeutic application of radiolabelled nanomaterials are discussed.

Landscape analysis of adjacent gene rearrangements reveals BCL2L14-ETV6 gene fusions in more aggressive triple-negative breast cancer

Triple-negative breast cancer (TNBC) accounts for 10 to 20% of breast cancer, with chemotherapy as its mainstay of treatment due to lack of well-defined targets, and recent genomic sequencing studies have revealed a paucity of TNBC-specific mutations. Recurrent gene fusions comprise a class of viable genetic targets in solid tumors; however, their role in breast cancer remains underappreciated due to the complexity of genomic rearrangements in this cancer. Our interrogation of the whole-genome sequencing data for 215 breast tumors catalogued 99 recurrent gene fusions, 57% of which are cryptic adjacent gene rearrangements (AGRs). The most frequent AGRs, BCL2L14-ETV6, TTC6-MIPOL1, ESR1-CCDC170, and AKAP8-BRD4, were preferentially found in the more aggressive forms of breast cancers that lack well-defined genetic targets. Among these, BCL2L14-ETV6 was exclusively detected in TNBC, and interrogation of four independent patient cohorts detected BCL2L14-ETV6 in 4.4 to 12.2% of TNBC tumors. Interestingly, these fusion-positive tumors exhibit more aggressive histopathological features, such as gross necrosis and high tumor grade. Amid TNBC subtypes, BCL2L14-ETV6 is most frequently detected in the mesenchymal entity, accounting for ∼19% of these tumors. Ectopic expression of BCL2L14-ETV6 fusions induce distinct expression changes from wild-type ETV6 and enhance cell motility and invasiveness of TNBC and benign breast epithelial cells. Furthermore, BCL2L14-ETV6 fusions prime partial epithelial-mesenchymal transition and endow resistance to paclitaxel treatment. Together, these data reveal AGRs as a class of underexplored genetic aberrations that could be pathological in breast cancer, and identify BCL2L14-ETV6 as a recurrent gene fusion in more aggressive form of TNBC tumors.

Tumor-infiltrating regulatory T cells, CD8/Treg ratio, and cancer stem cells are correlated with lymph node metastasis in patients with early breast cancer

BACKGROUND

Tumor-infiltrating lymphocytes are an important component of the tumor microenvironment (TME) in breast cancer. They have been linked with tumor pathogenesis in advanced stages. However, little is known about their contribution in early phases. In this study, we analyzed the infiltration of leukocytes and cancer stem cells (CSC) in tumors from patients with early breast cancer.

METHODS

Samples of blood and tumor tissue from 30 patients with breast cancer were collected, and the number of dendritic cells (DC), T cells, and CSC were analyzed by flow cytometry.

RESULTS

Tumor-infiltrating CD4 and CD8 T cells expressed higher levels of cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) compared with peripheral T cells. Regulatory T cells (Treg) were enriched in tumors and overexpressed glucocorticoid-induced TNFR-related protein and CTLA-4. Tumor Treg had a positive correlation with the amount of myeloid DC (mDC) and disease progression. The CD8/Treg ratio was associated with lymph node metastasis and tumor stages. The main subset of DC in early breast tumors was mDC, while plasmacytoid DC were almost absent. CSC were present in most tumors with higher frequencies in patients with lymph node metastasis. CSC were also associated with the amount of tumor-infiltrating Treg.

CONCLUSION

Early breast cancer has an inflammatory milieu characterized by mDC, Treg, and CSC infiltration. The frequencies of Treg, CSC and CD8/Treg ratio were associated with disease progression. The composition of leukocytes and the presence of CSC in early breast tumors should be considered for the development of new therapeutic approaches.

Regulation and New Treatment Strategies in Breast Cancer

Breast cancer classifications are based on the presence or absence of estrogen receptor and progesterone receptor along with the overexpression or amplification of the Her2 receptor. Although the overall 5-year survival rate of breast cancer patients has increased due to the use of targeted therapies, a subset of patients can acquire resistance over time or are unresponsive when presented in the clinic. Novel therapies focusing on molecular pathways and cell cycle regulation currently being used in the clinic may lead to increased response in this subset of patients.

Silencing PSME3 induces colorectal cancer radiosensitivity by downregulating the expression of cyclin B1 and CKD1

Resistance to radiotherapy remains a severe obstacle in the treatment of high-risk colorectal cancer patients. Recent studies have indicated that proteasome activator complex subunit 3 (PSME3) participates in the development and progression of various human malignancies and is proposed to play a role in tumor radioresistance. However, the impact of PSME3 on radioresistance of colorectal cancer has been largely unknown. In the present study, the enhanced expression of PSME3 was observed in colorectal cancer cells and tissue. Upregulation of PSME3 was significantly implicated in lymph node state, lymphovascular invasion, and Dukes' stage. Furthermore, high PSME3 expression was closely linked to poorer overall and progression-free survival in patients with colorectal cancer. The study further demonstrated that the proliferative, invasive and migratory potential of colorectal cancer cells was effectively inhibited in vitro after silencing PSME3. Our results verified that knockdown of PSME3 probably triggered cell cycle arrest at the G2/M phase by downregulation of cyclinB1 and CDK1, thereby enhancing the radiosensitivity of colorectal cancer cells. These data illustrated that PSME3 is a promising biomarker predictive of colorectal cancer prognosis and silencing of PSME3 may provide with a new approach for sensitizing the radiotherapy in colorectal cancer.

Impact statement

It is reported that colorectal cancer (CRC) is the third most common cancer worldwide and the fourth leading cause of cancer-related death. At present, the main treatment method of colorectal cancer is surgery, supplemented by radiotherapy and chemotherapy. Among them, radiotherapy plays an important role in the treatment of locally advanced colorectal cancer, surgery, and chemotherapy. Our study found that down-regulation of PSME3 may enhance the radiosensitivity of CRC cells by triggering cell cycle arrest, which suggests that silence PSME3 may provide a new method for improving the radiosensitivity of CRC. What’more, our research also demonstrated that PSME3 may promote proliferation, invasive and migratory potential of CRC cells, which implies that PSME3 might be a biomarker of CRC for early diagnosis and treatment.

Silencing LGR6 Attenuates Stemness and Chemoresistance via Inhibiting Wnt/β-Catenin Signaling in Ovarian Cancer

Leucine-rich-repeat-containing G protein-coupled receptors (LGRs) have been widely found to be implicated with development and progression in multiple cancer types. However, the clinical significance and biological functions of LGR6 in ovarian cancer remains unclear. In this study, LGR6 expression was mainly examined by immunohistochemistry. Functional assays in vitro and animal experiments in vivo were carried out to explore the effect of LGR6 on cancer stem cell (CSC) characteristics and chemotherapeutic responses in ovarian cancer cells. Luciferase assays and GSEA were used to discern the underlying mechanisms contributing to the roles of LGR6 in ovarian cancer. Here, we reported that LGR6 was upregulated in ovarian cancer, which positively correlated with poor chemotherapeutic response and progression survival in ovarian cancer patients. Loss-of-function assays showed that downregulating LGR6 abrogated the CSC-like phenotype and chemoresistance in vitro. More importantly, silencing LGR6 improved the chemoresistance of ovarian cancer cells to cisplatin in vivo. Mechanistic investigation further revealed that silencing LGR6 inhibited stemness and chemoresistance by repressing Wnt/β-catenin signaling. Collectively, our results uncover a novel mechanism contributing to LGR6-induced chemotherapeutic resistance in ovarian cancer, providing the evidence for LGR6 as a potential therapeutic target in ovarian cancer.

Nucleostemin expression in breast cancer is a marker of more aggressive phenotype and unfavorable patients' outcome: A STROBE-compliant article

Cancer stem cells (CSCs) are postulated to play significant role in the pathogenesis, progression as well as drug resistance of breast cancer. Nucleostemin (NS) is thought to be a key molecule for stemness, and the clinical impact of NS immunoreactivity in breast cancer can indicate its actual role and future therapeutic potentials.The current study is an observational study with an attempt to evaluate the correlation between NS expression (protein and gene expression levels) and different clinicopathological attributes of invasive breast cancer. For that reason, we investigated NS immunohistochemistry expression on commercial tissue microarray (TMA) of 102 patients and 51 archival specimens from patients admitted to Saqr Hospital, Ras Al Khaimah and diagnosed in Al Baraha Hospital, Dubai, UAE. In addition, the association between NS (GNL3) gene expression and different prognostic parameters as well as patient outcome was also evaluated using 2 large publicly available databases.Interestingly, we found NS expression to be associated with less differentiated and more advance stage. In addition, NS expression was significantly higher in larger size (P = .001) and LN-positive tumors (P = .007). Notably, NS expression was significantly correlated to P53 positive (P = .037) status. Furthermore, NS was found to be more expressed in the highly aggressive breast cancer subtypes including human epidermal growth factor receptor 2 (HER-2) and triple negative breast cancer (TNBC) subtypes. Moreover, our results also showed that high GNL3 gene expression to be associated with poor patient outcome and higher chances of tumor recurrence.Our results highlight NS expression as a marker of aggressive phenotype and poor outcome and indicate its possible use as a potential target for CSC-associated breast cancer management.

The Role of Tumor Microenvironment and Impact of Cancer Stem Cells on Breast Cancer Progression and Growth

Breast cancer is not only a mass of genetically abnormal tissue in the breast. This is a well-organized system of a complex heterogeneous tissue. Cancer cells produce regulatory signals that stimulate stromal cells to proliferate and migrate; then, stromal elements respond to these signals by releasing components necessary for tumor development that provide structural support, vasculature, and extracellular matrices. Developing tumors can mobilize a variety of cell types from both local and distant niches via secret chemical factors derived from cancer cells themselves or neighboring cells disrupted by growing neoplasm, such as fibroblasts, immune inflammatory cells, and endothelial cells. CSCs are a group of very few cells that are tumorigenic (able to form tumors) and are defined as those cells within a tumor that can self-renew and lead to tumorigenesis. BCSCs represent a small population of cells that have stem cell characteristics and are related to breast cancer. There are different theories about the origin of BCSCs. BCSCs are responsible for breast carcinoma metastasis. Usually, there is a metastatic spread to the bones, and rarely to the lungs and liver. A phenomenon that allows BCSCs to make the transition from epithelial to mesenchymal expression and thus avoid the effect of cytotoxic agents is the epithelial-mesenchymal transition (EMT). During this process, cells change their molecular characteristics in terms of loss of epithelial characteristics taking the mesenchymal phenotype. This process plays a key role in the progression, invasion, and metastasis of breast tumors.

Natural compound Tetrocarcin-A downregulates Junctional Adhesion Molecule-A in conjunction with HER2 and inhibitor of apoptosis proteins and inhibits tumor cell growth

Overexpression of the tight junction protein Junctional Adhesion Molecule-A (JAM-A) has been linked to aggressive disease in breast and other cancers, but JAM-targeting drugs remain elusive. Screening of a natural compound library identified the antibiotic Tetrocarcin-A as a novel downregulator of JAM-A and human epidermal growth factor receptor-2 (HER2) protein expression in breast cancer cells. Lysosomal inhibition partially rescued the downregulation of JAM-A and HER2 caused by Tetrocarcin-A, and attenuated its cytotoxic activity. Tetrocarcin-A treatment or JAM-A silencing reduced AKT and ERK phosphorylation, inhibited c-FOS phosphorylation at Threonine-232 (its transcriptional regulation site), inhibited nuclear localization of c-FOS, and downregulated expression of the inhibitor of apoptosis proteins (IAP). This was accompanied by Tetrocarcin-A-induced caspase-dependent apoptosis. To begin evaluating the potential clinical relevance of our findings, we extended our studies to other models. Encouragingly, Tetrocarcin-A downregulated JAM-A expression and caused cytotoxicity in primary breast cells and lung cancer stem cells, and inhibited the growth of xenografts in a semi-in vivo model involving invasion across the chicken egg chorioallantoic membrane. Taken together, our data suggest that Tetrocarcin-A warrants future evaluation as a novel cancer therapeutic by virtue of its ability to downregulate JAM-A expression, reduce tumorigenic signaling and induce apoptosis.

MSCs inhibit tumor progression and enhance radiosensitivity of breast cancer cells by down-regulating Stat3 signaling pathway

The acquisition of radioresistance by breast cancer cells during radiotherapy may lead to cancer recurrence and poor survival. Signal transducer and activator of transcription 3 (Stat3) is activated in breast cancer cells and, therefore, may be an effective target for overcoming therapeutic resistance. Mesenchymal stem cells (MSCs) have been investigated for use in cancer treatment. Here, we investigated the potential of MSC conditioned medium (MSC-CM) in sensitizing breast cancer to radiotherapy. It was found that MSC-CM could inhibit the level of activated Stat3, suppress cancer growth, and exhibit synergetic effects with radiation treatment in vitro and in vivo. Furthermore, MSC-CM reduced the ALDH-positive cancer stem cells (CSCs) population, modulated several potential stem cell markers, and decreased tumor migration, as well as metastasis. These results demonstrate that MSC-CM suppresses breast cancer cells growth and sensitizes cancer cells to radiotherapy through inhibition of the Stat3 signaling pathway, thus, providing a novel strategy for breast cancer therapy by overcoming radioresistance.

Hypoxia-inducible factor 1-dependent expression of adenosine receptor 2B promotes breast cancer stem cell enrichment

Breast cancer stem cells (BCSCs), which are characterized by a capacity for unlimited self-renewal and for generation of the bulk cancer cell population, play a critical role in cancer relapse and metastasis. Hypoxia is a common feature of the cancer microenvironment that stimulates the specification and maintenance of BCSCs. In this study, we found that hypoxia increased expression of adenosine receptor 2B (A2BR) in human breast cancer cells through the transcriptional activity of hypoxia-inducible factor 1. The binding of adenosine to A2BR promoted BCSC enrichment by activating protein kinase C-δ, which phosphorylated and activated the transcription factor STAT3, leading to increased expression of interleukin 6 and NANOG, two key mediators of the BCSC phenotype. Genetic or pharmacological inhibition of A2BR expression or activity decreased hypoxia- or adenosine-induced BCSC enrichment in vitro, and dramatically impaired tumor initiation and lung metastasis after implantation of MDA-MB-231 human breast cancer cells into the mammary fat pad of immunodeficient mice. These data provide evidence that targeting A2BR might be an effective strategy to eradicate BCSCs.

Flubendazole elicits anti-metastatic effects in triple-negative breast cancer via STAT3 inhibition

Tumor metastasis remains the cause of 90% of cancer-related deaths. Cancer stem cells (CSC) are thought to be responsible for the aggressive and metastatic nature of triple-negative breast cancers (TNBC), and new therapeutic strategies are being devised to target them. Flubendazole (FLU) is a widely used anthelmintic agent that also exhibits anticancer activity in several cancer types. The aim of this study was to characterize the mechanism of action of FLU on breast cancer stem cell (BCSC)-like properties and metastasis in TNBC. FLU treatment caused a significant induction of apoptosis, accompanied by G2/M phase accumulation, caspase-3/-7 activation and the dysregulation of STAT3 activation in TNBC cells. The latter phenomenon was associated with impairment of cancer stem-like traits, concomitant with a reduction in the CD24^low /CD44^high , CD24^high /CD49f^high subpopulation, ALDH1 activity and mammosphere formation. The BCSC-enriched populations exhibited enhanced metastasis with higher STAT3 activation, while FLU administration inhibited tumor growth, angiogenesis and lung and liver metastasis, coinciding with decreased MMP-2 and MMP-9 levels in circulating blood. FLU kills not only rapid proliferating tumor cells but also effectively eradicates BCSC-like cells in vitro and in vivo. Our findings warrant further investigation of FLU as a treatment for metastatic TNBC.

The Notch Pathway in Breast Cancer Progression

Objective

Notch signaling pathway is a vital parameter of the mammalian vascular system. In this review, the authors summarize the current knowledge about the impact of the Notch signaling pathway in breast cancer progression and the therapeutic role of Notch's inhibition.

Methods

The available literature in MEDLINE, PubMed, and Scopus, regarding the role of the Notch pathway in breast cancer progression was searched for related articles from about 1973 to 2017 including terms such as “Notch,” “Breast Cancer,” and “Angiogenesis.” Results. Notch signaling controls the differentiation of breast epithelial cells during normal development. Studies confirm that the Notch pathway has a major participation in breast cancer progression through overexpression and/or abnormal genetic type expression of the notch receptors and ligands that determine angiogenesis. The cross-talk of Notch and estrogens, the effect of Notch in breast cancer stem cells formation, and the dependable Notch overexpression during breast tumorigenesis have been studied enough and undoubtedly linked to breast cancer development. The already applied therapeutic inhibition of Notch for breast cancer can drastically change the course of the disease.

Conclusion

Current data prove that Notch pathway has a major participation and multiple roles during breast tumor progression. Inhibition of Notch receptors and ligands provides innovative therapeutic results and could become the therapy of choice in the next few years, even though further research is needed to reach safe conclusions.

Functionalized TiO2 nanoparticles labelled with 225Ac for targeted alpha radionuclide therapy

The ²²⁵Ac radioisotope exhibits very attractive nuclear properties for application in radionuclide therapy. Unfortunately, the major challenge for radioconjugates labelled with ²²⁵Ac is that traditional chelating moieties are unable to sequester the radioactive daughters in the bioconjugate which is critical to minimize toxicity to healthy, non-targeted tissues. In the present work, we propose to apply TiO₂ nanoparticles (NPs) as carrier for ²²⁵Ac and its decay products. The surface of TiO₂ nanoparticles with 25 nm diameter was modified with Substance P (5-11), a peptide fragment which targets NK1 receptors on the glioma cells, through the silan-PEG-NHS linker. Nanoparticles functionalized with Substance P (5-11) were synthesized with high yield in a two-step procedure, and the products were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and thermogravimetric analysis (TGA). The obtained results show that one TiO₂-bioconjugate nanoparticle contains in average 80 peptide molecules on its surface. The synthesized TiO₂-PEG-SP(5-11) conjugates were labelled with ²²⁵Ac by ion-exchange reaction on hydroxyl (OH) functional groups on the TiO₂ surface. The labelled bioconjugates almost quantitatively retain ²²⁵Ac in phosphate-buffered saline (PBS), physiological salt and cerebrospinal fluid (CSF) for up to 10 days. The leaching of ²²¹Fr, a first decay daughter of ²²⁵Ac, in an amount of 30% was observed only in CSF after 10 days. The synthesized ²²⁵Ac-TiO₂-PEG-SP(5-11) has shown high cytotoxic effect in vitro in T98G glioma cells; therefore, it is a promising new radioconjugate for targeted radionuclide therapy of brain tumours.

Long non-coding RNA PVT1 predicts poor prognosis and induces radioresistance by regulating DNA repair and cell apoptosis in nasopharyngeal carcinoma

The long non-coding RNA, plasmacytoma variant translocation 1 (PVT1), is highly expressed in a variety of tumors, and is believed to be a potential oncogene. However, the role and mechanism of action of PVT1 in the carcinogenesis and progression of nasopharyngeal carcinomas (NPCs) remains unclear. In this study, for the first time, we have discovered that PVT1 shows higher expression in NPCs than in normal nasopharyngeal epithelial tissue, and patients with NPCs who show higher expression of PVT1 have worse progression-free and overall survivals. Additionally, we observed that the proliferation of NPC cells decreased, and their rate of apoptosis increased; these results indicated that the knockdown of PVT1 expression in the NPC cells induced radiosensitivity. Further, we have shown that the knockdown of PVT1 expression can induce apoptosis in the NPC cells by influencing the DNA damage repair pathway after radiotherapy. In general, our study shows that PVT1 may be a novel biomarker for prognosis and a new target for the treatment of NPCs. Additionally, targeting PVT1 may be a potential strategy for the clinical management of NPC and for the improvement of the curative effect of radiation in NPCs.

LSD1 activation promotes inducible EMT programs and modulates the tumour microenvironment in breast cancer

Complex regulatory networks control epithelial-to-mesenchymal transition (EMT) but the underlying epigenetic control is poorly understood. Lysine-specific demethylase 1 (LSD1) is a key histone demethylase that alters the epigenetic landscape. Here we explored the role of LSD1 in global epigenetic regulation of EMT, cancer stem cells (CSCs), the tumour microenvironment, and therapeutic resistance in breast cancer. LSD1 induced pan-genomic gene expression in networks implicated in EMT and selectively elicits gene expression programs in CSCs whilst repressing non-CSC programs. LSD1 phosphorylation at serine-111 (LSD1-s111p) by chromatin anchored protein kinase C-theta (PKC-θ), is critical for its demethylase and EMT promoting activity and LSD1-s111p is enriched in chemoresistant cells in vivo. LSD1 couples to PKC-θ on the mesenchymal gene epigenetic template promotes LSD1-mediated gene induction. In vivo, chemotherapy reduced tumour volume, and when combined with an LSD1 inhibitor, abrogated the mesenchymal signature and promoted an innate, M1 macrophage-like tumouricidal immune response. Circulating tumour cells (CTCs) from metastatic breast cancer (MBC) patients were enriched with LSD1 and pharmacological blockade of LSD1 suppressed the mesenchymal and stem-like signature in these patient-derived CTCs. Overall, LSD1 inhibition may serve as a promising epigenetic adjuvant therapy to subvert its pleiotropic roles in breast cancer progression and treatment resistance.

Interleukin 7-expressing fibroblasts promote breast cancer growth through sustenance of tumor cell stemness

The tumor microenvironment harbors cancer-associated fibroblasts that function as major modulators of cancer progression. Here, we assessed to which extent distinct cancer-associated fibroblast subsets impact mammary carcinoma growth and cancer cell stemness in an orthotopic murine model. We found that fibroblasts expressing the Cre recombinase under the control of the interleukin 7 promoter occupied mainly the tumor margin where they physically interacted with tumor cells. Intratumoral ablation of interleukin 7-expressing fibroblasts impaired breast tumor growth and reduced the clonogenic potential of cancer cells. Moreover, cDNA expression profiling revealed a distinct oncogenic signature of interleukin 7-producing fibroblasts. In particular, Cxcl12 expression was strongly enhanced in interleukin 7-producing fibroblasts and cell type-specific genetic ablation and systemic pharmacological inhibition revealed that the CXCL12/CXCR4 axis impacts breast tumor cell stemness. Elevated expression of CXCL12 and other stem cell factors in primary human breast cancer-associated fibroblasts indicates that certain fibroblast populations support tumor cell stemness and thereby promote breast cancer growth.

Epithelial Mesenchymal Transition (EMT) in Metastatic Breast Cancer in Omani Women

Breast cancer (BC) in Oman affects younger women and has a more aggressive course. Clinical and biological variables like age, pregnancy, tumor size, type, grade, receptor expression and proliferation predict disease aggression but there is no direct predictor of metastasis except lymphovascular invasion. Epithelial-mesenchymal transition (EMT) is characterized by epithelial cells losing epithelial and acquiring mesenchymal morpho-immunophenotypic characteristics. In tumors, EMT-like transitions may signify a metastatic phenotype and have features in common with cancer stem cells (CSC) which show resistance to chemotherapy. This study aimed to identify EMT and CSC phenotypes in metastatic and non-metastatic breast cancer in Omani women and their association with conventional clinico-pathological predictors of BC. In a retrospective study of ninety-six Omani women with breast cancer, the association of age, pregnancy/lactation, tumor size, type, grade, ductal carcinoma insitu (DCIS), lymphovascular invasion, hormone/ HER2 receptor expression and Ki67 proliferation index (Ki67 PI) was tested with EMT/ CSC phenotype and metastasis. Young age ≤ 40 years, lymphovascular invasion and EMT had a strong association with metastasis; CSC approached significance. Vimentin expression in tumor cells, fibronectin and MMP-11 in stroma were reliable markers of EMT; dual EMT and CSC phenotype (Vim+/ CD44+/ CD 24-/low) had a strong association with apocrine variant, basal-like tumors and triple negative cancers. EMT had a strong association with Ki67 proliferation index (PI) and CSC with HER2-like tumors and distant metastasis. These select markers may be useful in metastasis-prediction in pre-treatment biopsies.

LGR5 promotes cancer stem cell traits and chemoresistance in cervical cancer

Cancer stem cells (CSCs), also known as tumor-initiating cells, contribute to tumorigenesis, resistance to chemoradiotherapy and recurrence in human cancers, suggesting targeting CSCs may represent a potential therapeutic strategy. Leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5) has recently been found to be a bona fide marker of colorectal CSCs. Our previous study showed that LGR5 functions as a tumor promoter in cervical cancer by activating the Wnt/β-catenin pathway. However, very little is known about the function or contribution of LGR5 to cervical CSCs. Here, we have modulated the expression of LGR5 using an overexpression vector or short hairpin RNA in cervical cancer cell lines. We demonstrated that elevated LGR5 expression in cervical cancer cells increased tumorsphere-forming efficiency; conferred chemoresistance to cisplatin treatment; augmented cell migration, invasion and clonogenicity; and elevated the levels of stem cell-related transcription factors in vitro. Furthermore, modulated LGR5⁺ cells, unlike LGR5^- cells, were highly tumorigenic in vivo. In addition, the modulated LGR5⁺ cells could give rise to both LGR5⁺ and LGR5^- cells in vitro and in vivo, thereby establishing a cellular hierarchy. Finally, we found that the increased tumorsphere-forming efficiency induced by LGR5 could be regulated through the inhibition or activation of the Wnt/β-catenin pathway in cervical cancer cells. Taken together, these results indicate that LGR5 has a vital oncogenic role by promoting cervical CSC traits and may represent a potential clinical target.

Shrimp miR-S8 Suppresses the Stemness of Human Melanoma Stem-like Cells by Targeting the Transcription Factor YB-1

Cross-species regulation of gene expression by microRNA is a possible untapped opportunity for miRNA-based therapy. In this study, we report a novel approach to ablate melanoma stem-like cells by targeting the transcription factor YB-1, which is significantly and selectively upregulated in these cells in melanoma. Silencing YB-1 expression was sufficient to significantly inhibit the stemness of melanoma stem-like cells. In exploring YB-1 targeting, we discovered that the shrimp microRNA miR-S8 could suppress human YB-1 expression in melanoma stem-like cells. Mechanistic investigations revealed that miR-S8 recognized the 3'UTR of YB-1 mRNA and mediated its degradation. In tumor cell and xenograft experiments, miR-S8 suppressed the tumorigenic capacity of melanoma stem-like cells by targeting human YB-1. Overall, our results illuminated a novel aspect of miRNA-mediated cross-species gene expression and its use in regulating cancer stem-like cells. Cancer Res; 77(20); 5543-53. ©2017 AACR.

Liquid-phase electron microscopy of molecular drug response in breast cancer cells reveals irresponsive cell subpopulations related to lack of HER2 homodimers

The development of drug resistance in cancer poses a major clinical problem. An example is human epidermal growth factor receptor 2 (HER2) overexpressing breast cancer often treated with anti-HER2 antibody therapies, such as trastuzumab. Since drug resistance is rooted mainly in tumor cell heterogeneity, we examined the drug effect in different subpopulations of SKBR3 breast cancer cells, and compared the results with a drug resistant cell line, HCC1954. Correlative light microscopy and liquid-phase scanning transmission electron microscopy (STEM) were used to quantitatively analyze HER2 responses upon drug binding, whereby many tens of whole cells were imaged. Trastuzumab was found to selectively cross-link and down regulate HER2 homodimers from the plasma membranes of bulk cancer cells. In contrast, HER2 resided mainly as monomers in rare subpopulations of resting- and cancer stem cells (CSCs), and these monomers were not internalized after drug binding. The HER2 distribution was hardly influenced by trastuzumab for the HCC1954 cells. These findings show that resting cells and CSCs are irresponsive to the drug, and thus point towards a molecular explanation behind the origin of drug resistance. This analytical method is broadly applicable to study membrane protein interactions in the intact plasma membrane, while accounting for cell heterogeneity.

Targeting interlukin-6 to relieve immunosuppression in tumor microenvironment

Immunotolerance is one of the hallmarks of malignant tumors. Tumor cells escape from host immune surveillance through various mechanisms resulting in tumor progression and therapeutic resistance. Interlukin-6 is a proinflammatory cytokine involved in many physiological and pathological processes by integrating with multiple intracellular signaling pathways. Aberrant expression of interlukin-6 is associated with the growth, metastasis, and chemotherapeutic resistance in a wide range of cancers. Interlukin-6 exerts immunosuppressive capacity mostly by stimulating the infiltrations of myeloid-derived suppressor cells, tumor-associated neutrophils, and cancer stem-like cells via Janus-activated kinase/signal transducer and activator of transcription 3 pathway in tumor microenvironment. On this foundation, blockage of interlukin-6 signal may provide potential approaches to novel therapies. In this review, we introduced interlukin-6 pathways and summarized molecular mechanisms related to interlukin-6-induced immunosuppression of tumor cell. We also concluded recent clinical studies targeting interlukin-6 as an immune-based therapeutic intervention in patients with cancer.

HET0016 decreases lung metastasis from breast cancer in immune-competent mouse model

Distant metastasis is the primary cause of death in the majority of the cancer types. Recently, much importance has been given to tumor microenvironment (TME) in the development of invasive malignant tumors, as well as the metastasis potential. The ability of tumor cells to modulate TME and to escape immune-mediated attack by releasing immunosuppressive cytokines has become a hallmark of breast cancer. Our study shows the effect of IV formulation of HET0016 (HPßCD-HET0016) a selective inhibitor of 20-HETE synthesis, administered intravenously in immune-competent in vivo mouse model of murine breast cancer. 4T1 luciferase positive cells were implanted to the mammary fat pad in Balb/c mice. Treatment started on day 15, and was administered for 5 days a week for 3 weeks. The development of metastasis was detected via optical imaging. Blood, spleen, lungs, bone marrow and tumor were collected for flow cytometry, to investigate changes in myeloid-derived suppressive cells (MDSCs) populations and endothelial phenotype. Tumor and lungs were collected for protein analysis. Our results show that HPßCD-HET0016: (1) decreased tumor volume and lung metastasis compared to the vehicle group; (2) reduced migration and invasion of tumor cells and levels of metalloproteinases in the lungs of animals treated with HPßCD-HET0016 via PI3K/AKT pathway; and (3) decreased expression of pro-inflammatory cytokines, growth factors and granulocytic MDSCs population in the lung microenvironment in treated animals. Thus, HPßCD-HET0016 showed potential in treating lung metastasis in a preclinical mouse model and needs further investigations on TME.

211At labeled substance P (5-11) as potential radiopharmaceutical for glioma treatment

INTRODUCTION

The purposes of the present work were to label substance P (5-11) with ²¹¹At using a rhodium(III) complex with a bifunctional ligand-2-(1,5,9,13-tetrathiacyclohexadecan-3-yloxy)acetic acid ([16aneS₄]-COOH) and to assess the in vitro stability and toxicity of the obtained radiobioconjugate.

METHODS

Two approaches were evaluated to obtain ¹³¹I/²¹¹At-Rh[16aneS₄]-SP_5-11 radiobioconjugates, based on 2-step and 1-step syntheses. In the first method ¹³¹I/²¹¹At-Rh[16aneS₄]-COOH complexes were obtained that required further coupling to a biomolecule. In the second approach, the bioconjugate [16aneS₄]-SP_5-11 was synthesized and further labeled with ¹³¹I and ²¹¹At through the utilization of a Rh(III) metal cation bridge. The synthesized compounds were analyzed by HPLC, TLC and paper electrophoresis.

RESULTS

The ¹³¹I/²¹¹At-Rh[16aneS₄]-COOH complexes were obtained in high yield and possessed good stability in PBS and CSF. Preliminary studies on coupling of ¹³¹I-Rh[16aneS₄]-COOH to substance P (5-11) in 2-step synthesis showed that this procedure was too long with respect to ²¹¹At half-life, prompting us to improve it by finally using a 1-step synthesis. This strategy not only shortened the labeling time, but also increased final yield of ¹³¹I/²¹¹At-Rh[16aneS₄]-SP_5-11 radiobioconjugates. The stability of both compounds in PBS and CSF was high. Toxicity studies with the ²¹¹At-Rh[16aneS₄]-SP_5-11 demonstrated that radiobioconjugate significantly reduced T98G cell viability in a dose dependent manner reaching 20% of survival at the highest radioactivity 1200kBq/mL.

CONCLUSIONS

The radiobioconjugate ²¹¹At-Rh[16aneS₄]-SP_5-11 revealed its potential in killing glioma T98G cells during in vitro studies; therefore further animal studies to are required to determine its in vivo stability and treatment potential in normal and xenografted mice.

Genome-wide effects of MELK-inhibitor in triple-negative breast cancer cells indicate context-dependent response with p53 as a key determinant

Triple-negative breast cancer (TNBC) is an aggressive, highly recurrent breast cancer subtype, affecting approximately one-fifth of all breast cancer patients. Subpopulations of treatment-resistant cancer stem cells within the tumors are considered to contribute to disease recurrence. A potential druggable target for such cells is the maternal embryonic leucine-zipper kinase (MELK). MELK expression is upregulated in mammary stem cells and in undifferentiated cancers, where it correlates with poor prognosis and potentially mediates treatment resistance. Several MELK inhibitors have been developed, of which one, OTSSP167, is currently in clinical trials. In order to better understand how MELK and its inhibition influence TNBC, we verified its anti-proliferative and apoptotic effects in claudin-low TNBC cell lines MDA-MB-231 and SUM-159 using MTS assays and/or trypan blue viability assays together with analysis of PARP cleavage. Then, using microarrays, we explored which genes were affected by OTSSP167. We demonstrate that different sets of genes are regulated in MDA-MB-231 and SUM-159, but in both cell lines genes involved in cell cycle, mitosis and protein metabolism and folding were regulated. We identified p53 (TP53) as a potential upstream regulator of the regulated genes. Using western blot we found that OTSSP167 downregulates mutant p53 in all tested TNBC cell lines (MDA-MB-231, SUM-159, and BT-549), but upregulates wild-type p53 in the luminal A subtype MCF-7 cell line. We propose that OTSSP167 might have context-dependent or off-target effects, but that one consistent mechanism of action could involve the destabilization of mutant p53.

Predicting and Overcoming Chemotherapeutic Resistance in Breast Cancer

Our understanding of breast cancer and its therapeutic approach has improved greatly due to the advancement of molecular biology in recent years. Clinically, breast cancers are characterized into three basic types based on their immunohistochemical properties. They are triple-negative breast cancer, estrogen receptor (ER) and progesterone receptor (PR)-positive-HR positive breast cancer, and human epidermal growth factor receptor 2 (HER2)-positive breast cancer. Even though these subtypes have been characterized, assessment of a breast cancer's receptor status is still widely used to determine whether or not a targeted therapy could be applied. Moreover, drug resistance is common in all breast cancer types despite the different treatment modalities applied. The development of resistance to different therapeutics is not mutually exclusive. It seems that tumor could be resistant to multiple treatment strategies, such as being both chemoresistant and monoclonal antibody resistant. However, the underlying mechanisms are complicated and need further investigation. In this chapter, we aim to provide a brief review of the different types of breast cancer and their respective treatment strategies. We also review the possible mechanisms of potential drug resistance associated with each treatment type. We believe that a better understanding of the drug resistance mechanisms can lead to a more effective and efficient therapeutic success.

From transformation to metastasis: deconstructing the extracellular matrix in breast cancer

The extracellular matrix (ECM) is a guiding force that regulates various developmental stages of the breast. In addition to providing structural support for the cells, it mediates epithelial-stromal communication and provides cues for cell survival, proliferation, and differentiation. Perturbations in ECM architecture profoundly influence breast tumor progression and metastasis. Understanding how a dysregulated ECM can facilitate malignant transformation is crucial to designing treatments to effectively target the tumor microenvironment. Here, we address the contribution of ECM mechanics to breast cancer progression, metastasis, and treatment resistance and discuss potential therapeutic strategies targeting the ECM.

Low expression of galectin-3 is associated with poor survival in node-positive breast cancers and mesenchymal phenotype in breast cancer stem cells

BACKGROUND

Galectin-3 (Gal3) plays diverse roles in cancer initiation, progression, and drug resistance depending on tumor type characteristics that are also associated with cancer stem cells (CSCs). Recurrence of breast carcinomas may be attributed to the presence of breast CSCs (BCSCs). BCSCs exist in mesenchymal-like or epithelial-like states and the transition between these states endows BCSCs with the capacity for tumor progression. The discovery of a feedback loop with galectins during epithelial-to-mesenchymal transition (EMT) prompted us to investigate its role in breast cancer stemness.

METHOD

To elucidate the role of Gal3 in BCSCs, we performed various in vitro and in vivo studies such as sphere-formation assays, Western blotting, flow cytometric apoptosis assays, and limited dilution xenotransplant models. Histological staining for Gal3 in tissue microarrays of breast cancer patients was performed to analyze the relationship of clinical outcome and Gal3 expression.

RESULTS

Here, we show in a cohort of 87 node-positive breast cancer patients treated with doxorubicin-based chemotherapy that low Gal3 was associated with increased lymphovascular invasion and reduced overall survival. Analysis of in vitro BCSC models demonstrated that Gal3 knockdown by small hairpin RNA (shRNA) interference in epithelial-like mammary spheres leads to EMT, increased sphere-formation ability, drug-resistance, and heightened aldefluor activity. Furthermore, Gal3negative BCSCs were associated with enhanced tumorigenicity in orthotopic mouse models.

CONCLUSIONS

Thus, in at least some breast cancers, loss of Gal3 might be associated with EMT and cancer stemness-associated traits, predicts poor response to chemotherapy, and poor prognosis.

Prostate tumour overexpressed-1 promotes tumourigenicity in human breast cancer via activation of Wnt/β-catenin signalling

Breast cancer is the most common malignancy in females. The presence of cancer stem cells (CSCs) is the main cause of local and distant tumour recurrence and is associated with poor outcome in breast cancer. However, the molecular mechanisms underlying the maintenance of CSCs remain largely unknown. This study demonstrates that prostate tumour overexpressed-1 (PTOV1) enhances the CSC population and augments the tumourigenicity of breast cancer cells both in vitro and in vivo. Moreover, PTOV1 suppresses transcription of Dickkopf-1 (DKK1) by recruiting histone deacetylases and subsequently reducing DKK1 promoter histone acetylation, followed by activation of Wnt/β-catenin signalling. Restoration of DKK1 expression in PTOV1-overexpressing cells counteracts the effects of PTOV1 on Wnt/β-catenin activation and the CSC population. Collectively, these results suggest that PTOV1 positively regulates the Wnt/β-catenin signalling pathway and enhances tumourigenicity in breast cancer; this novel mechanism may represent a therapeutic target for breast cancer. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Differential Roles for DUSP Family Members in Epithelial-to-Mesenchymal Transition and Cancer Stem Cell Regulation in Breast Cancer

Dual-specificity phosphatases (DUSPs) dephosphorylate threonine/serine and tyrosine residues on their substrates. Here we show that DUSP1, DUSP4, and DUSP6 are involved in epithelial-to-mesenchymal transition (EMT) and breast cancer stem cell (CSC) regulation. DUSP1, DUSP4, and DUSP6 are induced during EMT in a PKC pathway signal-mediated EMT model. We show for the first time that the key chromatin-associated kinase PKC-θ directly regulates a subset of DUSP family members. DUSP1, DUSP4, and DUSP6 globally but differentially co-exist with enhancer and permissive active histone post-translational modifications, suggesting that they play distinct roles in gene regulation in EMT/CSCs. We show that nuclear DUSP4 associates with the key acetyltransferase p300 in the context of the chromatin template and dynamically regulates the interplay between two key phosphorylation marks: the 1834 (active) and 89 (inhibitory) residues central to p300’s acetyltransferase activity. Furthermore, knockdown with small-interfering RNAs (siRNAs) shows that DUSP4 is required for maintaining H3K27ac, a mark mediated by p300. DUSP1, DUSP4, and DUSP6 knockdown with siRNAs shows that they participate in the formation of CD44^hi/CD24^lo/EpCAM⁺ breast CSCs: DUSP1 knockdown reduces CSC formation, while DUSP4 and DUSP6 knockdown enhance CSC formation. Moreover, DUSP6 is overexpressed in patient-derived HER2⁺ breast carcinomas compared to benign mammary tissue. Taken together, these findings illustrate novel pleiotropic roles for DUSP family members in EMT and CSC regulation in breast cancer.

Kazinol-E is a specific inhibitor of ERK that suppresses the enrichment of a breast cancer stem-like cell population

Growing evidence shows that cancer stem-like cells (CSLCs) contribute to breast cancer recurrence and to its resistance to conventional therapies. The extracellular signal-regulated kinase (ERK) signaling pathway is a major determinant in the control of diverse cellular processes, including the maintenance of CSLCs. In this study, we found that Kazinol-E, an antioxidant flavan from Broussonetia kazinoki, decreased the CSLC population of a breast cancer cell line, MCF7. The CSLC population, characterized by CD44 high/CD24 low expression or by high Aldehyde dehydrogenase 1 activity, was decreased by a concentration of Kazinol-E that did not affect the growth of bulk-cultured MCF7 cells. Kazinol-E did not decrease EGF-induced ERK phosphorylation in CSLCs, but did block the phosphorylation of an ERK substrate, p90RSK2, at Thr359/Ser363. We further demonstrated that EGF-induced ERK activity was blocked by Kazinol-E in a wild-type K-Ras-expressing non-small cell lung cancer cell line H226B. An in vitro kinase assay with purified ERK1 and p90RSK2 as its substrate demonstrated a direct inhibition of ERK activity by Kazinol E. Additionally, a the molecular docking study provided putative binding modes of Kazinol-E into the ATP binding pocket of ERK1 Collectively, these results suggest that Kazinol-E is a direct inhibitor of ERK1, and more studies are warranted to develop this reagent for therapeutic breast CSLC targeting.

MMGZ01, an anti-DLL4 monoclonal antibody, promotes nonfunctional vessels and inhibits breast tumor growth

Increasing evidence suggests that DLL4 (Delta-like 4)-Notch signaling plays a critical role in cell fate determination and differentiation in tissues. Blocking DLL4-Notch signaling results in inhibition of tumor growth, which is associated with increased nonfunctional vessels and poor perfusion in the tumor. We successfully generated a human DLL4 monoclonal antibody MMGZ01 that binds specifically to DLL4 to disrupt the interaction between DLL4 and Notch1. MMGZ01 showed high affinity to DLL4 to inhibit the DLL4-mediated human umbilical vein endothelial cell (HUVEC) phenotype. Furthermore, MMGZ01 stimulated HUVEC vessel sprouting and tubule formation in vitro. In addition, MMGZ01 had a pronounced effect in promoting immature vessels and reduced breast cancer cell growth in vivo. Finally, MMGZ01 treatment inhibited the proliferation of breast cancer cells, induced tumor cell apoptosis, suppressed mammosphere formation, decreased CD44(+)/CD24(-) cell population, and reduced epithelial mesenchymal transition (EMT). These findings suggest that antagonism of the DLL4-Notch signaling pathway might provide a potential therapeutic approach for breast cancer treatment.

A biotherapy based on PSCs-in-3D spheroid-ameliorated biologics depletes in vivo cancer-sustaining stem cells

CSCs are able to survive routine anticancer procedures and peripheral-immune attack. Here we develop and detail a framework of CSC elimination governed by 3D-biologics. Pluripotent cells-engineered 3D-biologics (PMSB) and control non-3D-biologics were prepared from placenta-based somatic stem cells (PSCs) and inoculated respectively into senile hosts bearing progressive mammary, lung, colon carcinomas and melanoma. We demonstrate that PMSB evokes in vivo central-immune microenvironment with subsequent re-expression of thymosin-α1 ~ β4 in thymic cortex-medulla borderline for rapid MHC-unrestricted renewal of γδT-dominated immunocompetence. The post-renewal γδT-subsets could accurately bind and drive CSCs into apoptosis. Finally, with central/peripheral integral microenvironment renewal and TERT/Wnt/β-catenin pathway blockade, the CSC-subsets are fully depleted, leading to substantial cure of diverse tumors by PMSB inoculation (P < 0.01), yet not by non-3D-biologics. Thus, our study may contribute to open up a new avenue for tumor remission via pluripotent cells-engineered 3D-biologics addressing quick renewal of central-thymus and peripheral immune-microenvironment.

Role of miR-140 in embryonic bone development and cancer

Bone is increasingly viewed as an endocrine organ with key biological functions. The skeleton produces hormones and cytokines, such as FGF23 and osteocalcin, which regulate an extensive list of homoeostatic functions. Some of these functions include glucose metabolism, male fertility, blood cell production and calcium/phosphate metabolism. Many of the genes regulating these functions are specific to bone cells. Some of these genes can be wrongly expressed by other malfunctioning cells, driving the generation of disease. The miRNAs are a class of non-coding RNA molecules that are powerful regulators of gene expression by suppressing and fine-tuning target mRNAs. Expression of one such miRNA, miR-140, is ubiquitous in chondrocyte cells during embryonic bone development. Activity in cells found in the adult breast, colon and lung tissue can silence genes required for tumour suppression. The realization that the same miRNA can be both normal and detrimental, depending on the cell, tissue and time point, provides a captivating twist to the study of whole-organism functional genomics. With the recent interest in miRNAs in bone biology and RNA-based therapeutics on the horizon, we present a review on the role of miR-140 in the molecular events that govern bone formation in the embryo. Cellular pathways involving miR-140 may be reactivated or inhibited when treating skeletal injury or disorder in adulthood. These pathways may also provide a novel model system when studying cancer biology of other cells and tissues.