CD44+/CD24- breast cancer cells exhibit enhanced invasive properties: an early step necessary for metastasis

Neuroactive steroids activate membrane progesterone receptors to induce sex specific effects on protein kinase activity

Neuroactive steroids (NAS), which are synthesized in the brain from progesterone, exert potent effects on behavior and are used to treat postpartum depression, yet how these compounds induce sustained modifications in neuronal activity are ill-defined. Here, we examined the efficacy of NAS for membrane progesterone receptors (mPRs) δ and ε, members of a family of GPCRs for progestins that are expressed in the CNS. NAS increase PKC activity via the Gq activation of mPRδ with EC50s between 3 and 11nM. In contrast, they activate Gs via mPRε to potentiate PKA activity with similar potencies. NAS also induced the rapid internalization of only mPRδ. In the forebrain of female mice, mPRδ expression levels were 8-fold higher than in males. Consistent with this, the activation of PKC by NAS was evident in acute brain slices from female mice. Collectively, our results suggest that NAS may exert sex-specific effects on intracellular signaling in the brain via the activation of mPRs.

Rat Sarcoma (RAS)-Protein-Targeting Synthetic Cell-Penetrating Peptide as an Anticancer Biomaterial

Various bioactive materials, including peptides, have become potential candidates for slowing cancer growth and metastasis. Among bioactive peptides, a synthetic cell-penetrating peptide referred to as rat sarcoma (RAS)-binding peptide (RBP) was suggested as a potential entity that targets RAS with high affinity in MDA-MB-231 cancer cells. This RAS binding further inhibits the RAS-rapidly accelerated fibrosarcoma (RAF) protein-protein interaction. The current study revealed that RBP effectively suppresses proliferation and extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation by disrupting the RAS-RAF interaction. This intervention not only inhibits cell migration and invasion but also has substantial potential for preventing metastasis. The RAS-RAF-ERK1/2 pathway is a key target for anticancer drug development because of frequent ERK and mitogen-activated protein kinase activation in human cancers. MDA-MB-231, a triple-negative breast cancer cell line, harbors a G13D Kirsten rat sarcoma viral oncogene homolog mutation, making it resistant to many drugs. In addition to its in vitro antitumor activity, RBP was identified as a potent antagonist that substantially arrests tumor growth and invasiveness in in vivo chicken egg and mouse xenograft tumor models. Notably, histopathological analyses revealed increased immune cell infiltration and decreased Ki-67 expression, confirming the ability of RBP to inhibit tumor cell proliferation. Taken together, these findings highlight RBP as a therapeutic anticancer biomaterial capable of impeding the progression and metastasis of RAS-mutated cancers.

Ketomimetic nutrients remodel the glycocalyx and trigger a metabolic defense in breast cancer cells

BACKGROUND

While the triggers for the metastatic transformation of breast cancer (BC) cells remain unknown, recent evidence suggests that intrinsic cellular metabolism could be a crucial driver of migratory disposition and chemoresistance. Aiming to decipher the molecular mechanisms involved in BC cell metabolic maneuvering, we study how a ketomimetic (ketone body-rich, low glucose) nutrient medium can engineer the glycocalyx and metabolic signature of BC cells, to further maneuver their response to therapy.

METHODS

Doxorubicin (DOX) has been used as a model chemotherapeutic in this study. Bioorthogonal imaging was used to assess the degree of sialylation of the glycocalyx along with measurements of drug-induced cytotoxicity and drug internalization. Single cell label-free metabolic imaging has been performed, coupled with measurement of cellular proliferative and migratory abilities, and MS-based metabolomic screens. Transcriptomic analysis of crucial enzymes was performed using total RNA extraction and rt-qPCR.

RESULTS

We found an inverse correlation of glycocalyx sialylation with drug-induced cytotoxicity and drug internalization, where ketomimetic media enhanced sialylation and protected BC cells from DOX. These hypersialylated cells proliferated slower and migrated faster as compared to their counterparts receiving a high glucose media, while exhibiting a preference for glycolysis. These cells also showed pronounced lipid droplet accumulation coupled with an inversion in their metabolomic profile. Enzymatic removal of sialic acid moieties at the glycocalyx revealed for the first time, a direct role of sialic acids as defense guards, blocking DOX entry at the cellular membrane to curtail internalization. Interestingly, the non-cancerous mammary epithelial cells exhibited opposite trends and this differential pattern in cancer vs. normal cells was traced to its biochemical roots, i.e. the expression levels of key enzymes involved in sialylation and fatty acid synthesis.

CONCLUSIONS

Our findings revealed that a ketomimetic medium enhances chemoresistance and invasive disposition of BC cells via two main oncogenic pathways: hypersialylation and lipid synthesis. We propose that the crosstalk between these pathways, juxtaposed at the synthesis of the glycan precursor UDP-GlcNAc, furthers advancement of a metastatic phenotype in BC cells under ketomimetic conditions. Non-cancerous cells lack this dual defense machinery and end up being sensitized to DOX under ketomimetic conditions.

Identification and Pharmacological Targeting of Treatment-Resistant, Stem-like Breast Cancer Cells for Combination Therapy

Tumors frequently harbor isogenic yet epigenetically distinct subpopulations of multi-potent cells with high tumor-initiating potential-often called Cancer Stem-Like Cells (CSLCs). These can display preferential resistance to standard-of-care chemotherapy. Single-cell analyses can help elucidate Master Regulator (MR) proteins responsible for governing the transcriptional state of these cells, thus revealing complementary dependencies that may be leveraged via combination therapy. Interrogation of single-cell RNA sequencing profiles from seven metastatic breast cancer patients, using perturbational profiles of clinically relevant drugs, identified drugs predicted to invert the activity of MR proteins governing the transcriptional state of chemoresistant CSLCs, which were then validated by CROP-seq assays. The top drug, the anthelmintic albendazole, depleted this subpopulation in vivo without noticeable cytotoxicity. Moreover, sequential cycles of albendazole and paclitaxel-a commonly used chemotherapeutic -displayed significant synergy in a patient-derived xenograft (PDX) from a TNBC patient, suggesting that network-based approaches can help develop mechanism-based combinatorial therapies targeting complementary subpopulations.

Statement of significance

Network-based approaches, as shown in a study on metastatic breast cancer, can develop effective combinatorial therapies targeting complementary subpopulations. By analyzing scRNA-seq data and using clinically relevant drugs, researchers identified and depleted chemoresistant Cancer Stem-Like Cells, enhancing the efficacy of standard chemotherapies.

True cancer stem cells exhibit relative degrees of dormancy and genomic stability

BACKGROUND

Cancer stem cells in human tumors have been defined by stem cell markers, embryonal signaling pathways and characteristic biology, ie., namely the ability to repopulate the proliferating population. However, even if these properties can be demonstrated within a tumor cell subpopulation, it does not mean that they are truly hierarchical stem cells because they could have been derived from the proliferating population in a reversible manner.

METHODS

Using a human PDX, Mary-X, that overall expressed a strong cancer stem cell phenotype, the study conducted both GPP-labelled retroviral transfection and fluorescent microsphere uptake studies to distinguish proliferating from dormant cells and array CGH to identify regions of amplifications (gains) and deletions (losses) on the overall Mary-X population and then applied derived probes by FISH on individual cells to identify a genomically stable subpopulation.

RESULTS

Whereas 97-99 % of the cells expressed retroviral GFP and not fluorescent particles and showed numerous gene amplifications and deletions, approximately 1-3 % of the cells showed the opposite. The subpopulation with the retained fluorescent microspheres and exhibiting genomic stability was significantly smaller in size than their GFP-expressing and genomically unstable counterparts. Sorting Mary-X spheroids on the basis of either CD133 or ALDH positivity further enriched for this subpopulation.

CONCLUSIONS

These studies indicate that a truly biological cancer stem cell subpopulation exists that exhibits both dormancy and genomic stability. This subpopulation could not have been derived from the proliferating and resulting genomically unstable population and therefore represents a truly hierarchical stem cell subpopulation capable of only unidirectional differentiation.

Neuroactive steroids activate membrane progesterone receptors to induce sex specific effects on protein kinase activity

Neuroactive steroids (NAS), which are synthesized in the brain from progesterone, exert potent effects on behavior and are used to treat postpartum depression, yet how these compounds induce sustained modifications in neuronal activity are ill-defined. Here, we examined the efficacy of NAS for membrane progesterone receptors (mPRs) δ and ε, members of a family of GPCRs for progestins that are expressed in the CNS. NAS increase PKC activity via G q activation of mPRδ with EC50s between 3-11nM. In contrast, they activate G s via mPRε to potentiate PKA activity with similar potencies. NAS also induced rapid internalization of only mPRδ. In the forebrain of female mice, mPRδ expression levels were 8-fold higher than males. Consistent with this, activation of PKC by NAS was evident in acute brain slices from female mice. Collectively, our results suggests that NAS may exert sex-specific effects on intracellular signaling in the brain via activation of mPRs.

Notch Pathway Deactivation Sensitizes Breast Cancer Stem Cells toward Chemotherapy Using NIR Light-Responsive Nanoparticles

Chemotherapy remains a major therapeutic approach to cancer treatment. However, its effectiveness can be compromised by the heterogeneity of a solid tumor, in which different cancer cell populations display varied responses to chemotherapy. Such an intratumor heterogeneous structure is maintained by the cancer stem-like cells (CSCs) with inherent capacities for self-renewal and differentiation, giving rise to diverse cell populations. To address this, we proposed a combinational strategy in which tumor lesion-targeted Notch signaling regulation was achieved to disrupt CSC-mediated cancer heterogeneity, thereby sensitizing solid tumors toward paclitaxel (PTX). Specifically, gamma-secretase inhibitor LY-411,575 was co-delivered with PTX using a near-infrared (NIR) light-controlled drug delivery system to realize targeted ablation of both differentiated cancer cells and undifferentiated CSCs. By enabling precise regulation of the Notch pathway at the tumor site through NIR light, we observed significantly elevated efficacy of chemotherapy and notable prevention of postsurgical tumor relapse while minimizing systemic side effects. The devised strategy shows promise in addressing the nonspecific inhibition of stemness across various organs, a challenge that hampers the clinical translation of gamma-secretase inhibitors in cancer therapy.

Unveiling patterns in spatial transcriptomics data: a novel approach utilizing graph attention autoencoder and multiscale deep subspace clustering network

BACKGROUND

The accurate deciphering of spatial domains, along with the identification of differentially expressed genes and the inference of cellular trajectory based on spatial transcriptomic (ST) data, holds significant potential for enhancing our understanding of tissue organization and biological functions. However, most of spatial clustering methods can neither decipher complex structures in ST data nor entirely employ features embedded in different layers.

RESULTS

This article introduces STMSGAL, a novel framework for analyzing ST data by incorporating graph attention autoencoder and multiscale deep subspace clustering. First, STMSGAL constructs ctaSNN, a cell type-aware shared nearest neighbor graph, using Louvian clustering exclusively based on gene expression profiles. Subsequently, it integrates expression profiles and ctaSNN to generate spot latent representations using a graph attention autoencoder and multiscale deep subspace clustering. Lastly, STMSGAL implements spatial clustering, differential expression analysis, and trajectory inference, providing comprehensive capabilities for thorough data exploration and interpretation. STMSGAL was evaluated against 7 methods, including SCANPY, SEDR, CCST, DeepST, GraphST, STAGATE, and SiGra, using four 10x Genomics Visium datasets, 1 mouse visual cortex STARmap dataset, and 2 Stereo-seq mouse embryo datasets. The comparison showcased STMSGAL's remarkable performance across Davies-Bouldin, Calinski-Harabasz, S_Dbw, and ARI values. STMSGAL significantly enhanced the identification of layer structures across ST data with different spatial resolutions and accurately delineated spatial domains in 2 breast cancer tissues, adult mouse brain (FFPE), and mouse embryos.

CONCLUSIONS

STMSGAL can serve as an essential tool for bridging the analysis of cellular spatial organization and disease pathology, offering valuable insights for researchers in the field.

USP10 deubiquitinates and stabilizes CD44 leading to enhanced breast cancer cell proliferation, stemness and metastasis

Despite extensive research, strategies to effectively combat breast cancer stemness and achieve a definitive cure remains elusive. CD44, a well-defined cancer stem cell (CSC) marker is reported to promote breast cancer tumorigenesis, metastasis, and chemoresistance. However, mechanisms leading to its enhanced expression and function is poorly understood. Here, we demonstrate that USP10 positively regulates CD44 protein levels and its downstream actions. While USP10 depletion prominently down-regulates CD44 protein levels and functions, its overexpression significantly enhances CD44 protein levels, leading to enhanced cluster tumor cell formation, stemness, and metastasis in breast cancer cells both in vitro and ex vivo in primary human breast tumor cells. USP10 interacts with CD44 and stabilizes it through deubiquitination both in breast cancer cell lines and human breast cancer-derived primary tumor cells. Stabilized CD44 shows enhanced interaction with cytoskeleton proteins Ezrin/Radixin/Moesin and potently activates PDGFRβ/STAT3 signaling which are involved in promoting CSC traits. Using USP10 stably expressing 4T1 cells, we further demonstrate that the USP10-CD44 axis potently promotes tumorigenicity in vivo in mice, while simultaneous depletion of CD44 in these cells renders them ineffective. In line with these findings, we further showed that inhibition of USP10 either through RNAi or the pharmacological inhibitor Spautin-1 significantly mitigated CD44 levels and its downstream function ex vivo in primary breast tumor cells. Finally, we demonstrated that primary breast tumor cells are more susceptible to chemotherapy when co-treated with USP10 inhibitor indicating that the USP10-CD44 axis could be an attractive therapeutic target in combination with chemotherapy in CD44 expressing breast cancers.

Co-Inhibition of tGLI1 and GP130 Using FDA-Approved Ketoconazole and Bazedoxifene Is Synergistic Against the Growth and Metastasis of HER2-Enriched and Triple-Negative Breast Cancers

Breast cancer stem cells (CSCs) are resistant to most cancer therapeutics and contribute to tumor recurrence and metastasis. Two breast CSC-promoting transcription factors, truncated glioma-associated oncogene homolog 1 (tGLI1) and signal transducer and activator of transcription 3 (STAT3), have been reported to be frequently co-expressed in HER2-enriched breast cancer and triple-negative breast cancer (TNBC), undergo protein-protein interactions for gene regulation and activation, and functionally cooperate to promote breast CSCs. STAT3 can be activated by activated interleukin-6 receptor/glycoprotein-130 (IL-6R/GP130). Co-targeting of tGLI1 and IL-6R/GP130 has not been investigated in breast cancer or any tumor type. Here, we report that tGLI1 and GP130 are co-overexpressed in the majority of HER2-enriched breast cancers and TNBCs at 53.8% and 44.4%, respectively. tGLI1+IL-6/IL-6R/GP130 signaling is frequently co-enriched and co-activated in HER2-enriched breast cancer and TNBC when compared to luminal subtypes. tGLI1+GP130 co-overexpression strongly promotes CSCs of HER2-enriched breast cancer and TNBC. FDA-approved tGLI1 inhibitor Ketoconazole and GP130 inhibitor Bazedoxifene synergize against breast cancer proliferation and CSC phenotypes in vitro and reduce TNBC tumor growth and metastatic burden in vivo. Our study demonstrates, for the first time, that co-targeting tGLI1 and IL-6R/GP130/STAT3 signaling pathways is synergistic against HER2-enriched breast cancer and TNBC, warranting future clinical investigations.

Nanomaterial-based detection of circulating tumor cells and circulating cancer stem cells for cancer immunotherapy

Nanomaterials have emerged as transformative tools for detecting circulating tumor cells (CTCs) and circulating cancer stem cells (CCSCs), significantly enhancing cancer diagnostics and immunotherapy. Nanomaterials, including those composed of gold, magnetic materials, and silica, have enhanced the sensitivity, specificity, and efficiency of isolating these rare cells from blood. These developments are of paramount importance for the early detection of cancer and for providing real-time insights into metastasis and treatment resistance, which are essential for the development of personalized immunotherapies. The combination of nanomaterial-based platforms with phenotyping techniques, such as Raman spectroscopy and microfluidics, enables researchers to enhance immunotherapy protocols targeting specific CTC and CCSC markers. Nanomaterials also facilitate the targeted delivery of immunotherapeutic agents, including immune checkpoint inhibitors and therapeutic antibodies, directly to tumor cells. This synergistic approach has the potential to enhance therapeutic efficacy and mitigate the risk of metastasis and relapse. In conclusion, this review critically examines the use of nanomaterial-driven detection systems for detecting CTCs and CCSCs, their application in immunotherapy, and suggests future directions, highlighting their potential to transform the integration of diagnostics and treatment, thereby paving the way for more precise and personalized cancer therapies.

Expression of cancer stem cell markers (CD24, CD44 & ALDH1A3 isoform) in Breast Cancer in Indian population considering clinicopathological characteristics and response to neoadjuvant chemotherapy - a prospective analysis from a university hospital

Cancer stem cells (CSC) are a small number of tumour propagating cells present in the bulk of tumour cells. Expression of biological markers for CSCs viz. cluster of differentiation 24 and 44 (CD24, CD44) and aldehyde dehyodeganse 1 (ALDH1) imply aggressive tumour cell behaviour and poorer outcome, particularly in breast cancer. N = 75 Tumor tissue samples from enrolled breast cancer patients were obtained and subjected to histopathological examination and immunohistochemistry (IHC) after informed consent from patients. In addition to the estrogen receptor, progesterone receptor, Her2 neu receptor, and Ki67 index; IHC was also performed for CD24, CD44 and ALDH1A3 expression. These markers' positivity was correlated with clinical parameters, therapy response and metastasis prognostication. Most patients had higher tumor stage and high nodal burden (81.3% with node positivity; N1-68%, N2 -6.6%, N3-6.6%). Study showed significant association of CD24-/CD44 + group (p = 0.021) with distant metastasis and significant association of CD24-/CD44 + /ALDH1A3 + (p = 0.008) with higher stage (T4 stage). Tumor tissues expressing CD24-/CD44 + /ALDH1A3 + group (p = 0.010) and CD24 + /CD44 + / ALDH1A3 + (p = 0.010) were significantly associated with poor response to treatment. The correlation of CD24-/CD44 + was also statistically significant (p = 0.009). Positive expression of either CD24 and/or CD44 presented with aggressive disease, larger tumours and heavy nodal burden at a younger age. Additionally, ALDH1A3 positivity signified higher metastasis rates. CD24-/CD44 + /ALDH1A3 + and CD24 + /CD44 + / ALDH1A3 + correlated with greater chances of distant metastasis, aggressive disease, limited response to chemotherapy and poorer prognosis. Thus, these observations establish the role of these CSC phenotypes as important factors for prognostic outcomes and predictors of adverse outcomes. CD24-/CD44 + /ALDH1A3 + expression could serve as an important prognostic marker and predictor of adverse outcomes in Indian breast cancer tumour biology.

Loss of myosin light chain kinase induces the cellular senescence associated secretory phenotype to promote breast epithelial cell migration

Overexpression or activation of oncogenes or loss of tumor-suppressor genes can induce cellular senescence as a defense mechanism against tumor development, thereby maintaining cellular homeostasis. However, cancer cells can circumvent this senescent state and continue to spread. Myosin light chain kinase (MLCK) is downregulated in many breast cancers. Here we report that downregulation of MLCK in normal breast epithelial cells induces a senescence-associated secretory phenotype and stimulates migration. The reduction of MLCK results in increased p21Cip1 expression, dependent on p53 and the AKT-mammalian target of rapamycin pathway. Subsequently, p21Cip1 promotes the secretion of soluble ICAM-1, IL-1α, IL-6 and IL-8, thereby enhancing collective cell migration in a non-cell-autonomous manner. These findings provide new mechanistic insights into the role of MLCK in cellular senescence and cancer progression.

T lymphocyte-derived IFN-γ facilitates breast cancer cells to pass the blood-brain barrier: An in vitro study corroborating translational data

The appearance of brain metastasis is the most serious complication of breast cancer with mostly fatal outcomes. To reach the brain, tumor cells need to pass the blood-brain barrier (BBB). The molecular mechanisms underlying penetration of the BBB are largely unknown. Previously we found that tumor-infiltrating T lymphocytes enhance the development of brain metastasis of estrogen receptor-negative (ER-) breast cancer. In the current study, we investigate the contribution of T lymphocytes and the IFN-γ pathway in enabling breast cancer cells to pass the in vitro BBB. CD8+ cells display the strongest stimulatory effect on breast cancer cell passage. We show that inhibition of the IFN-γ receptor in MDA-MB-231 breast cancer cells, or neutralization of soluble IFN-γ, impairs the in vitro trespassing of breast cancer cells. Importantly, we validated our findings using gene expression data of breast cancer patients. The CXCL-9,-10,-11/CXCR3 axis, dependent on IFN-γ signaling activity, was overexpressed in primary breast cancer samples of patients who developed brain metastasis. The data support a role for T-lymphocytes and the IFN-γ pathway in the formation of brain metastasis of ER-breast cancer, and offer targets to design future therapies for preventing breast cancer cells to cross the BBB.

Inhibition of miR-10b treats metastatic breast cancer by targeting stem cell-like properties

Despite advances in breast cancer screening and treatment, prognosis for metastatic disease remains dismal at 30% five-year survival. This is due, in large, to the failure of current therapeutics to target properties unique to metastatic cells. One of the drivers of metastasis is miR-10b, a small noncoding RNA implicated in cancer cell invasion, migration, viability, and proliferation. We have developed a nanodrug, termed MN-anti-miR10b, that delivers anti-miR-10b antisense oligomers to cancer cells. In mouse models of metastatic triple-negative breast cancer, MN-anti-miR10b has been shown to prevent onset of metastasis and eliminate existing metastases in combination with chemotherapy, even after treatment has been stopped. Recent studies have implicated miR-10b in conferring stem cell-like properties onto cancer cells, such as chemoresistance. In this study, we show transcriptional evidence that inhibition of miR-10b with MN-anti-miR10b activates developmental processes in cancer cells and that stem-like cancer cells have increased miR-10b expression. We then demonstrate that treatment of breast cancer cells with MN-anti-miR10b reduces their stemness, confirming that these properties make metastatic cells susceptible to the nanodrug actions. Collectively, these findings indicate that inhibition of miR-10b functions to impair breast cancer cell stemness, positioning MN-anti-miR10b as an effective treatment option for stem-like breast cancer subtypes.

Dual inhibition of the TrkA and JAK2 pathways using entrectinib and pacritinib suppresses the growth and metastasis of HER2-positive and triple-negative breast cancers

HER2-positive and triple-negative breast cancers (TNBC) are difficult to treat and associated with poor prognosis. Despite showing initial response, HER2-positive breast cancers often acquire resistance to HER2-targeted therapies, and TNBC lack effective therapies. To overcome these clinical challenges, we evaluated the therapeutic utility of co-targeting TrkA and JAK2/STAT3 pathways in these breast cancer subtypes. Here, we report the novel combination of FDA-approved TrkA inhibitors (Entrectinib or Larotrectinib) and JAK2 inhibitors (Pacritinib or Ruxolitinib) synergistically inhibited in vitro growth of HER2-positive breast cancer cells and TNBC cells. The Entrectinib-Pacritinib combination inhibited the breast cancer stem cell subpopulation, reduced expression of stemness genes, SOX2 and MYC, and induced apoptosis. The Entrectinib-Pacritinib combination suppressed orthotopic growth of HER2-positive Trastuzumab-refractory breast cancer xenografts and basal patient-derived xenograft (PDXs), reduced tumoral SOX2 and MYC, and induced apoptosis in both mouse models. The Entrectinib-Pacritinib combination inhibited overall metastatic burden, and brain and bone metastases of intracardially inoculated TNBC cells without toxicity. Together, our results demonstrate for the first time that co-inhibition of TrkA and JAK2 synergistically suppresses breast cancer growth and metastasis, thereby providing preclinical evidence that supports future clinical evaluations.

Laminin I mediates resistance to lapatinib in HER2-positive brain metastatic breast cancer cells in vitro

The role of extracellular matrix (ECM) prevalent in the brain metastatic breast cancer (BMBC) niche in mediating cancer cell growth, survival, and response to therapeutic agents is not well understood. Emerging evidence suggests a vital role of ECM of the primary breast tumor microenvironment (TME) in tumor progression and survival. Possibly, the BMBC cells are also similarly influenced by the ECM of the metastatic niche; therefore, understanding the effect of the metastatic ECM on BMBC cells is imperative. Herein, we assessed the impact of various ECM components (i.e., Tenascin C, Laminin I, Collagen I, Collagen IV, and Fibronectin) on brain metastatic human epidermal growth factor receptor 2 (HER2)-positive and triple negative breast cancer (TNBC) cell lines in vitro. The highly aggressive TNBC cell line was minimally affected by ECM components exhibiting no remarkable changes in viability and morphology. On the contrary, amongst various ECM components tested, the HER2-positive cell line was significantly affected by Laminin I with higher viability and demonstrated a distinct spread morphology. In addition, HER2-positive BMBC cells exhibited resistance to Lapatinib in presence of Laminin I. Mechanistically, Laminin I-induced resistance to Lapatinib was mediated in part by phosphorylation of Erk 1/2 and elevated levels of Vimentin. Laminin I also significantly enhanced the migratory potential and replicative viability of HER2-positive BMBC cells. In sum, our findings show that presence of Laminin I in the TME of BMBC cells imparts resistance to targeted therapeutic agent Lapatinib, while increasing the possibility of its dispersal and clonogenic survival.

Neutrophils exposed to a cholesterol metabolite secrete extracellular vesicles that promote epithelial-mesenchymal transition and stemness in breast cancer cells

Small extracellular vesicles (sEVs) are emerging as critical mediators of intercellular communication in the tumor microenvironment (TME). Here, we investigate the mechanisms by which sEVs derived from neutrophils treated with the cholesterol metabolite, 27-hydroxycholesterol (27HC), influence breast cancer progression. sEVs released from 27HC treated neutrophils enhance epithelial-mesenchymal transition (EMT) and stem-like properties in breast cancer cells, resulting in loss of adherence, increased migratory capacity and resistance to cytotoxic chemotherapy. Decreased microRNAs (miRs) within the sEVs resulted in activation of the WNT/β-catenin signaling pathway in recipient cells and suggest that this may be a predominant pathway for stem-like phenotype and EMT. Our findings underscore a novel mechanism by which 27HC-modulated neutrophils contribute to breast cancer pathophysiology through EV-mediated intercellular communication, suggesting potential therapeutic targets in cancer treatment.

The transcriptional landscape of cancer stem-like cell functionality in breast cancer

BACKGROUND

Cancer stem-like cells (CSCs) have been extensively researched as the primary drivers of therapy resistance and tumor relapse in patients with breast cancer. However, due to lack of specific molecular markers, increased phenotypic plasticity and no clear clinicopathological features, the assessment of CSCs presence and functionality in solid tumors is challenging. While several potential markers, such as CD24/CD44, have been proposed, the extent to which they truly represent the stem cell potential of tumors or merely provide static snapshots is still a subject of controversy. Recent studies have highlighted the crucial role of the tumor microenvironment (TME) in influencing the CSC phenotype in breast cancer. The interplay between the tumor and TME induces significant changes in the cancer cell phenotype, leading to the acquisition of CSC characteristics, therapeutic resistance, and metastatic spread. Simultaneously, CSCs actively shape their microenvironment by evading immune surveillance and attracting stromal cells that support tumor progression.

METHODS

In this study, we associated in vitro mammosphere formation assays with bulk tumor microarray profiling and deconvolution algorithms to map CSC functionality and the microenvironmental landscape in a large cohort of 125 breast tumors.

RESULTS

We found that the TME score was a significant factor associated with CSC functionality. CSC-rich tumors were characterized by an immune-suppressed TME, while tumors devoid of CSC potential exhibited high immune infiltration and activation of pathways involved in the immune response. Gene expression analysis revealed IFNG, CXCR5, CD40LG, TBX21 and IL2RG to be associated with the CSC phenotype and also displayed prognostic value for patients with breast cancer.

CONCLUSION

These results suggest that the characterization of CSCs content and functionality in tumors can be used as an attractive strategy to fine-tune treatments and guide clinical decisions to improve patients therapy response.

Comprehensive molecular interaction map of TGFβ induced epithelial to mesenchymal transition in breast cancer

Breast cancer is one of the prevailing cancers globally, with a high mortality rate. Metastatic breast cancer (MBC) is an advanced stage of cancer, characterised by a highly nonlinear, heterogeneous process involving numerous singling pathways and regulatory interactions. Epithelial-mesenchymal transition (EMT) emerges as a key mechanism exploited by cancer cells. Transforming Growth Factor-β (TGFβ)-dependent signalling is attributed to promote EMT in advanced stages of breast cancer. A comprehensive regulatory map of TGFβ induced EMT was developed through an extensive literature survey. The network assembled comprises of 312 distinct species (proteins, genes, RNAs, complexes), and 426 reactions (state transitions, nuclear translocations, complex associations, and dissociations). The map was developed by following Systems Biology Graphical Notation (SBGN) using Cell Designer and made publicly available using MINERVA ( http://35.174.227.105:8080/minerva/?id=Metastatic_Breast_Cancer_1 ). While the complete molecular mechanism of MBC is still not known, the map captures the elaborate signalling interplay of TGFβ induced EMT-promoting MBC. Subsequently, the disease map assembled was translated into a Boolean model utilising CaSQ and analysed using Cell Collective. Simulations of these have captured the known experimental outcomes of TGFβ induced EMT in MBC. Hub regulators of the assembled map were identified, and their transcriptome-based analysis confirmed their role in cancer metastasis. Elaborate analysis of this map may help in gaining additional insights into the development and progression of metastatic breast cancer.

The therapeutic effect of traditional Chinese medicine on breast cancer through modulation of the Wnt/β-catenin signaling pathway

Breast cancer, the most prevalent malignant tumor among women globally, is significantly influenced by the Wnt/β-catenin signaling pathway, which plays a crucial role in its initiation and progression. While conventional chemotherapy, the standard clinical treatment, suffers from significant drawbacks like severe side effects, high toxicity, and limited prognostic efficacy, Traditional Chinese Medicine (TCM) provides a promising alternative. TCM employs a multi-targeted therapeutic approach, which results in fewer side effects and offers a high potential for effective treatment. This paper presents a detailed analysis of the therapeutic impacts of TCM on various subtypes of breast cancer, focusing on its interaction with the Wnt/β-catenin signaling pathway. Additionally, it explores the effectiveness of both monomeric and compound forms of TCM in the management of breast cancer. We also discuss the potential of establishing biomarkers for breast cancer treatment based on key proteins within the Wnt/β-catenin signaling pathway. Our aim is to offer new insights into the prevention and treatment of breast cancer and to contribute to the standardization of TCM.

Chemoresistance to additive PARP/PI3K dual inhibition in triple-negative breast cancer cell lines is associated with adaptive stem cell-like prevalence

Cancer stem-like cells (CSCs) are posited to exhibit specialized oncogenic capacity to drive malignancies. CSCs are distinguished by enhanced hallmarks of cancer, including apoptosis avoidance, phenotypic plasticity and aberrant growth pathway signaling. Standard-of-care chemotherapies targeted to rapidly cycling cells routinely fail to eliminate this resistant subpopulation, leading to disease recurrence and metastasis. Triple-negative breast cancer (TNBC), a highly aggressive subtype of breast cancer, is enriched for tumor-propagating CD44+/CD24-/low CSCs, which are poorly ablated by chemotherapeutics and are associated with poor prognosis. CD44 governs sustained PI3K signaling in breast cancer, which is essential for CSC maintenance. PI3K inhibition can elicit DNA damage and down-regulate BRCA1 expression, which in turn enhance the synthetic lethality of PARP inhibitors. Here, we examined a dual chemotherapeutic approach targeting these pathways by combining a pan-PI3K inhibitor (Buparlisib) and a PARP1 inhibitor (Olaparib) on a panel of TNBC cell lines with distinct mutational profiles and proportions of CSCs. We observed differential sensitivity to this dual inhibition strategy and varying cellular stress and resistance responses across eight TNBC lines. The dual chemotherapeutic effect is associated with a reduction in S-phase cells, an increased in apoptotic cells and elevated expression of cleaved PARP, indicating a provoked replicative stress response. We observed that PARP/PI3K inhibition efficacy was potentiated by repeated administration in some TNBC lines and identified critical treatment schedules, which further potentiated the dual chemotherapeutic effect. Dual inhibition induced small but significant increases in CSC relative abundance as marked by CD44+/CD24-/low or ALDH1+ cells and increased stress and survival signaling in multiple TNBC cell lines, suggesting this sub-population contributes to TNBC chemoresistance. These results suggest the additive effects of PARP and PI3K inhibition against CSC phenotypes may be enhanced by temporally-staged administration in TNBC cells.

CD24 negativity reprograms mitochondrial metabolism to PPARα and NF-κB-driven fatty acid β-oxidation in triple-negative breast cancer

CD24 is a well-characterized breast cancer (BC) stem cell (BCSC) marker. Primary breast tumor cells having CD24-negativity together with CD44-positivity is known to maintain high metastatic potential. However, the functional role of CD24 gene in triple-negative BC (TNBC), an aggressive subtype of BC, is not well understood. While the significance of CD24 in regulating immune pathways is well recognized in previous studies, the significance of CD24 low expression in onco-signaling and metabolic rewiring is largely unknown. Using CD24 knock-down and over-expression TNBC models, our in vitro and in vivo analysis suggest that CD24 is a tumor suppressor in metastatic TNBC. Comprehensive in silico gene expression analysis of breast tumors followed by lipidomic and metabolomic analyses of CD24-modulated cells revealed that CD24 negativity induces mitochondrial oxidative phosphorylation and reprograms TNBC metabolism toward the fatty acid beta-oxidation (FAO) pathway. CD24 silencing activates PPARα-mediated regulation of FAO in TNBC cells. Further analysis using reverse-phase protein array and its validation using CD24-modulated TNBC cells and xenograft models nominated CD24-NF-κB-CPT1A signaling pathway as the central regulatory mechanism of CD24-mediated FAO activity. Overall, our study proposes a novel role of CD24 in metabolic reprogramming that can open new avenues for the treatment strategies for patients with metastatic TNBC.

Unraveling the role of CD24 in Hepatocellular carcinoma: Involvement of inactivated Hippo signaling and SOX4-mediated regulation

Hepatocellular carcinoma (HCC) is a prevalent type of liver cancer, and CD24 gene is reportedly involved in HCC progression. However, the precise regulatory mechanisms of CD24 in HCC remain unclear. In this study, we established a primary HCC mouse model and observed that CD24, induced by inactivation of the Hippo pathway, was highly expressed in HCC. Using a systematic molecular and genomic approach, we identified the Hippo-YAP1-SOX4 pathway as the mechanism through which YAP1 induces CD24 upregulation in HCC cells. CD24 knockdown significantly attenuated YAP1 activation-induced HCC. These findings shed light on the link between CD24 and HCC progression, particularly in the Hippo-inactivated subclass of HCC. Therefore, CD24 may serve as a potential target for specific treatment of this HCC subclass.

The role of telocytes and miR-21-5p in tumorigenicity and metastasis of breast cancer stem cells

BACKGROUND

This study aims to investigate the roles of telocytes on the metastatic properties of breast cancer stem cells (CSCs), and to re-evaluate the effect of miR-21-5p expression on CSCs following the addition of telocytes.

METHODS AND RESULTS

Telocytes from human bone marrow mononuclear cells were isolated/characterised. This was followed by the isolation/characterisation of CSCs from the MDA-MB-231. miR-21-5p was both overexpressed/inhibited in CSCs. Through co-culture studies, EMT transition and oncogenic properties of CSCs were investigated by analysing changes in ALDH1 and vimentin protein levels as well as changes in the ABCC11, SNAI1, LZTFL1, Oct 3/4, E- and N-cadherin gene expression levels. With the inhibition of miR-21-5p, significant increases in LZTFL and ABCC11 were observed with the addition of telocytes. The expression of the LZTFL gene, which decreased with the overexpression of miR-21-5p, increased in CSCs after co-culture with telocytes. While an increase expression of ABCC11, SNAI1, N-Cadherin, vimentin and ALDH was observed in CSCs after overexpression of miR-21-5p, significant decreases in these expressions were observed after co-culture with telocyte.

CONCLUSIONS

In our study, by gene/protein level analysis we demonstrated that telocytes may have the potential to reduce cancer metastasis through miR-21-5p in breast cancer progression and reduce EMT transition.

Targeting signaling pathways in cancer stem cells: A potential approach for developing novel anti-cancer therapeutics

Cancer stem cells (CSCs) have emerged as prime players in the intricate landscape of cancer development, progression, and resistance to traditional treatments. These unique cellular subpopulations own the remarkable capability of self-renewal and differentiation, giving rise to the diverse cellular makeup of tumors and fostering their recurrence following conventional therapies. In the quest for developing more effective cancer therapeutics, the focus has now shifted toward targeting the signaling pathways that govern CSCs behavior. This chapter underscores the significance of these signaling pathways in CSC biology and their potential as pivotal targets for the development of novel chemotherapy approaches. We delve into several key signaling pathways essential for maintaining the defining characteristics of CSCs, including the Wnt, Hedgehog, Notch, JAK-STAT, NF-κB pathways, among others, shedding light on their potential crosstalk. Furthermore, we highlight the latest advancements in CSC-targeted therapies, spanning from promising preclinical models to ongoing clinical trials. A comprehensive understanding of the intricate molecular aspects of CSC signaling pathways and their manipulation holds the prospective to revolutionize cancer treatment paradigms. This, in turn, could lead to more efficacious and personalized therapies with the ultimate goal of eradicating CSCs and enhancing overall patient outcomes. The exploration of CSC signaling pathways represents a key step towards a brighter future in the battle against cancer.

MicroRNA-204 Regulates Angiogenesis and Vasculogenic Mimicry in CD44+/CD24- Breast Cancer Stem-like Cells

Tumors have high requirements in terms of nutrients and oxygen. Angiogenesis is the classical mechanism for vessel formation. Tumoral vascularization has the function of nourishing the cancer cells to support tumor growth. Vasculogenic mimicry, a novel intratumoral microcirculation system, alludes to the ability of cancer cells to organize in three-dimensional (3D) channel-like architectures. It also supplies the tumors with nutrients and oxygen. Both mechanisms operate in a coordinated way; however, their functions in breast cancer stem-like cells and their regulation by microRNAs remain elusive. In the present study, we investigated the functional role of microRNA-204 (miR-204) on angiogenesis and vasculogenic mimicry in breast cancer stem-like cells. Using flow cytometry assays, we found that 86.1% of MDA-MB-231 and 92% of Hs-578t breast cancer cells showed the CD44+/CD24- immunophenotype representative of cancer stem-like cells (CSCs). The MDA-MB-231 subpopulation of CSCs exhibited the ability to form mammospheres, as expected. Interestingly, we found that the restoration of miR-204 expression in CSCs significantly inhibited the number and size of the mammospheres. Moreover, we found that MDA-MB-231 and Hs-578t CSCs efficiently undergo angiogenesis and hypoxia-induced vasculogenic mimicry in vitro. The transfection of precursor miR-204 in both CSCs was able to impair the angiogenesis in the HUVEC cell model, which was observed as a diminution in the number of polygons and sprouting cells. Remarkably, miR-204 mimics also resulted in the inhibition of vasculogenic mimicry formation in MDA-MB-231 and Hs-578t CSCs, with a significant reduction in the number of channel-like structures and branch points. Mechanistically, the effects of miR-204 were associated with a diminution of pro-angiogenic VEGFA and β-catenin protein levels. In conclusion, our findings indicated that miR-204 abrogates the angiogenesis and vasculogenic mimicry development in breast cancer stem-like cells, suggesting that it could be a potential tool for breast cancer intervention based on microRNA replacement therapies.

Green Tea Leaves and Rosemary Extracts Selectively Induce Cell Death in Triple-Negative Breast Cancer Cells and Cancer Stem Cells and Enhance the Efficacy of Common Chemotherapeutics

While incredible medical advancements in chemotherapeutics development for cancer treatment have been made, the majority of these are not selective in their mechanism of action, leading to adverse effects. Given the systemic toxicity associated with these therapies, they are not well suited for long-term use. Natural health products, or NHPs, may provide a way to selectively target the oxidative and metabolic vulnerabilities in cancer cells. White tea (Camelia sinensis) and rosemary (Salvia rosmarinus) are two natural extracts that have been studied extensively for their medicinal properties. However, their anticancer activity and mechanism of action are yet to be fully elucidated. We have examined the extracts' cancer cell-killing ability as well as their interactions with common chemotherapeutics in MDA-MB-231 cells, a triple-negative breast cancer cell line, in vitro. Cell death measurement, morphological and biochemical characterization of apoptotic cell death, mechanisms of action (mitochondrial depolarization and oxidative stress), and immunofluorescence assays to estimate the percentage of cancer stem cells (CSCs) were performed following treatment with Synthite tea extract (STE) and rosemary extract (RE), provided by Synthite Industries Limited alone and in combination with cisplatin and paclitaxel. The key findings in this study are that STE and RE alone demonstrated very efficient anticancer activity against TNBC, and more importantly, the administration of the extracts in conjunction with cisplatin and paclitaxel sensitizes cancer cells to achieve enhanced cell death. In addition, CSCs were found to be sensitive to treatment with STE alone and in combination with RE and exhibited greater sensitivity to combination therapies compared to chemotherapeutic alone. The significance of these observations is that STE and RE, well-tolerated NHPs, have the potential to enhance the efficacy of current chemotherapeutics when combined, as well as prevent relapse for TNBC.

Multiplexed Surface Protein Detection and Cancer Classification Using Gap-Enhanced Magnetic-Plasmonic Core-Shell Raman Nanotags and Machine Learning Algorithm

Cancer is the second leading cause of death attributed to disease worldwide. Current standard detection methods often rely on a single cancer marker, which can lead to inaccurate results, including false negatives, and an inability to detect multiple cancers simultaneously. Here, we developed a multiplex method that can effectively detect and classify surface proteins associated with three distinct types of breast cancer by utilizing gap-enhanced Raman scattering nanotags and machine learning algorithm. We synthesized anisotropic magnetic core-gold shell gap-enhanced Raman nanotags incorporating three different Raman reporters. These multicolor Raman nanotags were employed to distinguish specific surface protein markers in breast cancer cells. The acquired signals were deconvoluted and analyzed using classical least-squares regression to generate a surface protein profile and characterize the breast cancer cells. Furthermore, computational data obtained via finite-difference time-domain and discrete dipole approximation showed the amplification of the electric fields within the gap region due to plasmonic coupling between the two gold layers. Finally, a random forest classifier achieved an impressive classification and profiling accuracy of 93.9%, enabling effective distinguishing between the three different types of breast cancer cell lines in a mixed solution. With the combination of immunomagnetic multiplex target specificity and separation, gap-enhancement Raman nanotags, and machine learning, our method provides an accurate and integrated platform to profile and classify different cancer cells, giving implications for identification of the origin of circulating tumor cells in the blood system.

Rational peptide design for targeting cancer cell invasion

Cell invasion is an important process in cancer progression and recurrence. Invasion and implantation of cancer cells from their original place to other tissues, by disabling vital organs, challenges the treatment of cancer patients. Given the importance of the matter, many molecular treatments have been developed to inhibit cancer cell invasion. Because of their low production cost and ease of production, peptides are valuable therapeutic molecules for inhibiting cancer cell invasion. In recent years, advances in the field of computational biology have facilitated the design of anti-cancer peptides. In our investigation, using computational biology approaches such as evolutionary analysis, residue scanning, protein-peptide interaction analysis, molecular dynamics, and free energy analysis, our team designed a peptide library with about 100 000 candidates based on A6 (acetyl-KPSSPPEE-amino) sequence which is an anti-invasion peptide. During computational studies, two of the designed peptides that give the highest scores and showed the greatest sequence similarity to A6 were entered into the experimental analysis workflow for further analysis. In experimental analysis steps, the anti-metastatic potency and other therapeutic effects of designed peptides were evaluated using MTT assay, RT-qPCR, zymography analysis, and invasion assay. Our study disclosed that the IK1 (acetyl-RPSFPPEE-amino) peptide, like A6, has great potency to inhibit the invasion of cancer cells.

CD24 May Serve as an Immunotherapy Target in Triple-Negative Breast Cancer by Regulating the Expression of PD-L1

PURPOSE

CD24 mediates a "don't eat me" signal to escape the immune environment. However, the correlation between CD24 and PD-L1 is unclear. This study aimed to assess if CD24 can serve as a target for immunotherapy of triple-negative breast cancer (TNBC).

METHODS

Data on CD24 expression in breast cancer were acquired using the Oncomine and UALCAN tools. The role of CD24 expression on the prognosis of patients with TNBC was assessed using Kaplan-Meier analyses. Subsequently, STRING and TISIDB databases were used to construct protein-protein interaction networks and to explore immune-related molecules regulated by CD24. Immunofluorescence and immunohistochemistry assays were conducted to validate CD24 and PD-L1 expression and tumor infiltration lymphocyte (TIL) level. Survival analysis was also performed to explore the effect of CD24 and PD-L1 expression and TIL level in patients with TNBC. ShRNA was also used to explore the regulation role of CD24 on PD-L1 expression.

RESULTS

CD24 expression was significantly higher in breast cancer than in normal tissues, with high expression being significantly associated with a worse prognosis. CD24 was found to be significantly regulated by chemokines, immunoinhibitors, immunostimulators and TILs. Furthermore, CD24 expression showed a significant positive correlation with PD-L1 expression and a negative correlation with TIL level. In association with PD-L1, CD24 was found to positively regulate lymphocyte costimulation, T cell costimulation, and leukocyte activation. Furthermore, CD24 and PD-L1 co-expression contributed to worse survival outcomes. In addition, CD24 expression was found to attenuate the positive effects of high-level TILs on the prognosis of patients with TNBC. CD24 can also regulate the expression of PD-L1 in TNBC cells.

CONCLUSION

CD24 may attenuate the positive effects of high TIL levels on survival and may facilitate the immune escape of TNBC by regulating PD-L1 expression. Thus, it is a potential target for immunotherapy in TNBC.

pH-Responsive Polypropylene Sulfide Magnetic Nanocarrier-Mediated Chemo-Hyperthermia Kills Breast Cancer Stem Cells by Long-Term Reversal of Multidrug Resistance and Chemotherapy Resensitization

Cancer stem cells (CSCs) present a formidable challenge in cancer treatment due to their inherent resistance to chemotherapy, primarily driven by the overexpression of ABC transporters and multidrug resistance (MDR). Despite extensive research on pharmacological small-molecule inhibitors, effectively managing MDR and improving chemotherapeutic outcomes remain elusive. On the other hand, magnetic hyperthermia (MHT) holds great promise as a cancer therapeutic, but there is limited research on its potential to reverse MDR in breast CSCs and effectively eliminate CSCs through combined chemo-hyperthermia. To address these gaps, we developed tumor microenvironment-sensitive, drug-loaded poly(propylene sulfide) (PPS)-coated magnetic nanoparticles (PPS-MnFe). These nanoparticles were employed to investigate hyperthermia sensitivity and MDR reversion in breast CSCs, comparing their performance to that of small-molecule inhibitors. Additionally, we explored the efficacy of combined chemo-hyperthermia in killing CSCs. CSC-enriched breast cancer cells were subjected to low-dose MHT at 42 °C for 30 min and then treated with the chemical MDR inhibitor salinomycin (SAL). The effectiveness of each treatment in inhibiting MDR was assessed by measuring the efflux of the MDR substrate, rhodamine 123 (R123) dye. Notably, MHT induced a prolonged reversal of MDR activity compared with SAL treatment alone. After successfully inhibiting MDR, the breast CSCs were exposed to chemotherapy using paclitaxel to trigger synergistic cell death. The combination of MHT and chemotherapy demonstrated remarkable reductions in stemness properties, MDR reversal, and the effective eradication of breast CSCs in this innovative dual-modality approach.

Targeting breast cancer stem cells through retinoids: A new hope for treatment

Breast cancer is a complex and diverse disease accounting for nearly 30% of all cancers diagnosed in females. But unfortunately, patients develop resistance to the existing chemotherapeutic regimen, resulting in approximately 90% treatment failure. With over half a million deaths annually, it is imperative to explore new therapeutic approaches to combat the disease. Within a breast tumor, a small sub-population of heterogeneous cells, with a unique ability of self-renew and differentiation and responsible for tumor formation, initiation, and recurrence are referred to as breast cancer stem cells (BCSCs). These BCSCs have been identified as one of the main contributors to chemoresistance in breast cancer, making them an attractive target for developing novel therapeutic strategies. These cells exhibit surface biomarkers such as CD44+, CD24-/LOW, ALDH, CD133, and CD49f phenotypes. Higher expression of CD44+ and ALDH activity has been associated with the formation of tumors in various cancers. Moreover, the abnormal regulation of signaling pathways, including Hedgehog, Notch, β-catenin, JAK/STAT, and P13K/AKT/mTOR, leads to the formation of cancer stem cells, resulting in the development of tumors. The growing drug resistance in BC is a significant challenge, highlighting the need for new therapeutic strategies to combat this dreadful disease. Retinoids, a large group of synthetic derivatives of vitamin A, have been studied as chemopreventive agents in clinical trials and have been shown to regulate various crucial biological functions including vision, development, inflammation, and metabolism. On a cellular level, the retinoid activity has been well characterized and translated and is known to induce differentiation and apoptosis, which play important roles in the outcome of the transformation of tissues into malignant. Retinoids have been investigated extensively for their use in the treatment and prevention of cancer due to their high receptor-binding affinity to directly modulate gene expression programs. Therefore, in this study, we aim to summarize the current understanding of BCSCs, their biomarkers, and the associated signaling pathways. Retinoids, such as Adapalene, a third-generation retinoid, have shown promising anti-cancer potential and may serve as therapeutic agents to target BCSCs.

Stem Cell Protein PIWIL2 Promotes EMT Process and Stem Cell-Like Properties in MCF7 Breast Cancer Cell Line

Background

Piwi-like RNA-mediated gene silencing 2 (PIWIL2) is a member of AGO/PIWI gene family, which is enriched in cancer stem cells (CSCs). The purpose of this research was to investigate the overexpression of PIWIL2 and its role in the induction of EMT and CSC properties in MCF7 breast cancer cell line.

Materials and Methods

MCF7 cells were transfected with the human gene PIWIL2 (Hili) under the control of CMV promoter utilizing the neon electroporation method. Subsequently, the selection was conducted using G418, and doubling time was calculated in the transformed and control cells. RT and real-time PCR were also performed to analyze the expression of epithelial and mesenchymal genes and those related to CSCs.

Results

According to the observations from this study, transfecting MCF7 cells with PIWIL2 triggered the conversion of epithelial cells to mesenchymal cells and induced the genes specific for breast CSCs, which was coincident with 9-h reduction in the doubling time of the transfected cells. Furthermore, the molecular analyses revealed a significant reduction in the expression of epithelial markers, while a significant increase was detected in the expression of mesenchymal genes and many CSC biomarkers.

Conclusion

PIWIL2 protein acts as a master regulatory protein that is able to manipulate the transcription through specific signaling pathways, which allow the cells to gain stem cell-like properties.

Dormant tumors circumvent tumor-specific adaptive immunity by establishing a Treg-dominated niche via DKK3

Approximately 30% of breast cancer survivors deemed free of disease will experience locoregional or metastatic recurrence even up to 30 years after initial diagnosis, yet how residual/dormant tumor cells escape immunity elicited by the primary tumor remains unclear. We demonstrate that intrinsically dormant tumor cells are indeed recognized and lysed by antigen-specific T cells in vitro and elicit robust immune responses in vivo. However, despite close proximity to CD8+ killer T cells, dormant tumor cells themselves support early accumulation of protective FoxP3+ T regulatory cells (Tregs), which can be targeted to reduce tumor burden. These intrinsically dormant tumor cells maintain a hybrid epithelial/mesenchymal state that is associated with immune dysfunction, and we find that the tumor-derived, stem cell/basal cell protein Dickkopf WNT signaling pathway inhibitor 3 (DKK3) is critical for Treg inhibition of CD8+ T cells. We also demonstrate that DKK3 promotes immune-mediated progression of proliferative tumors and is significantly associated with poor survival and immunosuppression in human breast cancers. Together, these findings reveal that latent tumors can use fundamental mechanisms of tolerance to alter the T cell microenvironment and subvert immune detection. Thus, targeting these pathways, such as DKK3, may help render dormant tumors susceptible to immunotherapies.

Photodynamic therapy in cancer stem cells - state of the art

Despite significant efforts to control cancer progression and to improve oncology treatment outcomes, recurrence and tumor resistance are frequently observed in cancer patients. These problems are partly related to the presence of cancer stem cells (CSCs). Photodynamic therapy (PDT) has been developed as a therapeutic approach for solid tumors; however, it remains unclear how this therapy can affect CSCs. In this review, we focus on the effects of PDT on CSCs and the possible changes in the CSC population after PDT exposure. Tumor response to PDT varies according to the photosensitizer and light parameters employed, but most studies have reported the successful elimination of CSCs after PDT. However, some studies have reported that CSCs were more resistant to PDT than non-CSCs due to the increased efflux of photosensitizer molecules and the action of autophagy. Additionally, using different PDT approaches to target the CSCs resulted in increased sensitivity, reduction of sphere formation, invasiveness, stem cell phenotype, and improved response to chemotherapy. Lastly, although mainly limited to in vitro studies, PDT, combined with targeted therapies and/or chemotherapy, could successfully target CSCs in different solid tumors and promote the reduction of stemness, suggesting a promising therapeutic approach requiring evaluation in robust pre-clinical studies.

Understanding crosstalk of organ tropism, tumor microenvironment and noncoding RNAs in breast cancer metastasis

Cancer metastasis is one of the major clinical challenges worldwide due to limited existing effective treatments. Metastasis roots from the host organ of origin and gradually migrates to different regional and distant organs. In different breast cancer subtypes, different organs like bones, liver, lungs and brain are targeted by the metastatic tumor cells. Cancer renders mortality to their respective metastasizing sites like bones, brain, liver, and lungs. Metastatic breast cancers are best treated and managed if detected at an early stage. Metastasis is regulated by various molecular activators and suppressors. The conventional theory of 'seed and soil' states that metastatic tumor cells move to tumor microenvironment that has favorable conditions like blood flow for them to grow just like seeds grows when planted in fertile land. Additionally, different coding as well as non-coding RNAs play a very significant role in the process of metastasis by modulating their expression levels leading to a crosstalk of various tumorigenic cascades. Treatments for metastasis is also very critical in controlling this lethal process. Detecting breast cancer metastasis at an early stage is crucial for managing and predicting metastatic progression. In this review, we have compiled several factors that can be targeted to manage the onset and gradual stages of breast cancer metastasis.

γ-Secretase Inhibitor Potentiates the Activity of Suberoylanilide Hydroxamic Acid by Inhibiting Its Ability to Induce Epithelial to Mesenchymal Transition and Stemness via Notch Pathway Activation in Triple-Negative Breast Cancer Cells

Histone deacetylase inhibitors, such as suberoylanilide hydroxamic acid (SAHA), possess great therapeutic value for triple-negative breast cancer patients. However, their inherent ability to induce epithelial to mesenchymal transition in various malignancies has been of greater concern. Herein, we hypothesize that SAHA facilitates epithelial to mesenchymal transition (EMT) via activation of the Notch pathway. From the literature survey, it is evident that histone deacetylase mediates the formation of the co-repressor complex upon interacting with the DNA binding domain, thereby inhibiting the transcription of the Notch downstream genes. Hence, we hypothesize that the use of SAHA facilitates the transcriptional activation of the Notch target genes, by disrupting the co-repressor complex and recruiting the coactivator complex, thereby facilitating EMT. In this study, we have observed that SAHA upregulates the expression profile of the Notch downstream proteins (such as Notch intracellular domain, Hes-1, c-Myc, etc.) and the Notch ligands (such as Jagged-1 and Jagged-2), thereby aberrantly activating the signaling pathway. Therefore, we have focused on combination therapy using a γ-secretase inhibitor LY411575 that would enhance the efficacy of SAHA by blocking the canonical Notch pathway mediated via its intracellular domain. It was observed that co-treatment significantly mediates apoptosis, generates cellular reactive oxygen species, depolarizes mitochondria, and diminishes the stemness properties. Besides, it also mediates autophagy-independent cell death and diminishes the expression of inflammatory cytokines, along with the downregulation in the expression of the Notch downstream genes and mesenchymal markers. Altogether, our study provides a mechanistic basis for combating EMT potentiated by SAHA, which could be utilized as a rational strategy for the treatment of solid tumors, especially triple-negative breast cancer.

Layer-by-layer coated calcium carbonate nanoparticles for targeting breast cancer cells

Breast cancer is resistant to conventional treatments due to the specific tumour microenvironment, the associated acidic pH and the overexpression of receptors that enhance cells tumorigenicity. Herein, we optimized the synthesis of acidic resorbable calcium carbonate (CaCO3) nanoparticles and the encapsulation of a low molecular weight model molecule (Rhodamine). The addition of ethylene glycol during the synthetic process resulted in a particle size decrease: we obtained homogeneous CaCO3 particles with an average size of 564 nm. Their negative charge enabled the assembly of layer-by-layer (LbL) coatings with surface-exposed hyaluronic acid (HA), a ligand of tumour-associated receptor CD44. The coating decreased Rhodamine release by two-fold compared to uncoated nanoparticles. We demonstrated the effect of nanoparticles on two breast cancer cell lines with different aggressiveness - SK-BR-3 and the more aggressive MDA-MB-231 - and compared them with the normal breast cell line MCF10A. CaCO3 nanoparticles (coated and uncoated) significantly decreased the metabolic activity of the breast cancer cells. The interactions between LbL-coated nanoparticles and cells depended on HA expression on the cell surface: more particles were observed on the surface of MDA-MB-231 cells, which had the thickest endogenous HA coating. We concluded that CaCO3 nanoparticles are potential candidates to carry low molecular weight chemotherapeutics and deliver them to aggressive breast cancer sites with an HA-abundant pericellular matrix.

Promyelocytic leukemia protein regulates angiogenesis and epithelial-mesenchymal transition to limit metastasis in MDA-MB-231 breast cancer cells

Promyelocytic leukemia protein (PML) modulates diverse cell functions that contribute to both tumor suppressor and pro-oncogenic effects, depending on the cellular context. We show here that PML knockdown (KD) in MDA-MB-231, but not MCF7, breast cancer cells, prolonged stem-cell-like survival, and increased cell proliferation and migration, which is in line with gene-enrichment results from their RNA sequencing analysis. Of note, increased migration was accompanied by higher levels of the epithelial-mesenchymal transition (EMT) regulator Twist-related protein 2 (TWIST2). We showed here that PML binds to TWIST2 via its basic helix-loop-helix (bHLH) region and functionally interferes with the suppression of the epithelial target of TWIST2, CD24. In addition, PML ablation in MDA-MB-231 cells led to higher protein levels of hypoxia-inducible factor 1-alpha (HIF1a), resulting in a higher cell hypoxic response. Functionally, PML directly suppressed the induction of the HIF1a target gene vascular endothelial growth factor A (VEGFa). In line with these results, tumor xenografts of MDA-MB-231 PML-KD cells had enhanced aggressive properties, including higher microvessel density, faster local growth, and higher metastatic ability, with a preference for lung. Collectively, PML suppresses the cancer aggressive behavior by multiple mechanisms that impede both the HIF-hypoxia-angiogenic and EMT pathways.

Cancer stem cells are prevalent in the basal-like 2 and mesenchymal triple-negative breast cancer subtypes in vitro

Background: Triple-negative breast cancer (TNBC) is an aggressive subtype with the most unfavorable clinical outcomes, in part due to tumor heterogeneity, treatment resistance, and tumor relapse. The TNBC subtypes [basal-like 1 (BL1), basal-like 2 (BL2), mesenchymal (M), and luminal androgen receptor (LAR)] are biologically and clinically distinct entities that respond differently to local and systemic therapies. Therefore, we need to have a better understanding of cancer stemness relating to drug-resistant populations in the TNBC subtypes. Methods: Breast cancer stem cell (BCSC) distribution was investigated using an integrated flow cytometry approach with the ALDEFLUOR™ assay (ALDH) and CD24/CD44 antibodies. In total, 27 commercially available cell lines derived from normal and malignant mammary tissue were characterized into differentiated tumor cells and/or BCSC subpopulations (ALDH-CD44+CD24-/low enriched mesenchymal-like BCSCs, ALDH+non-CD44+CD24-/low enriched epithelial-like BCSCs, and highly purified ALDH+CD44+CD24-/low BCSCs). Results: BCSCs were not only enriched in estrogen receptor (ER) negative (mean, 49.6% versus 6.9% in ER+) and TNBC cell lines (51.3% versus 2.1% in Luminal A), but certain BCSC subpopulations (e.g., enriched mesenchymal-like BCSCs) were also significantly more common in the M (64.0% versus 6.2% in BL1; 64.0% versus 0% in LAR) and BL2 (77.4% versus 6.2% in BL1; 77.4% versus 0% in LAR; 77.4% versus 10.4% in TNBC UNS) TNBC subtypes. In contrast, ALDH status alone was not indicative of ER status or BC subtype. Conclusion: Taken together, these findings demonstrate the enrichment of potentially treatment-resistant BCSC subpopulations in the M and BL2 triple-negative breast cancer subtypes.

Cucurbit[8]uril-based water-dispersible assemblies with enhanced optoacoustic performance for multispectral optoacoustic imaging

Organic small-molecule contrast agents have attracted considerable attention in the field of multispectral optoacoustic imaging, but their weak optoacoustic performance resulted from relatively low extinction coefficient and poor water solubility restrains their widespread applications. Herein, we address these limitations by constructing supramolecular assemblies based on cucurbit[8]uril (CB[8]). Two dixanthene-based chromophores (DXP and DXBTZ) are synthesized as the model guest compounds, and then included in CB[8] to prepare host-guest complexes. The obtained DXP-CB[8] and DXBTZ-CB[8] display red-shifted and increased absorption as well as decreased fluorescence, thereby leading to a substantial enhancement in optoacoustic performance. Biological application potential of DXBTZ-CB[8] is investigated after co-assembly with chondroitin sulfate A (CSA). Benefiting from the excellent optoacoustic property of DXBTZ-CB[8] and the CD44-targeting feature of CSA, the formulated DXBTZ-CB[8]/CSA can effectively detect and diagnose subcutaneous tumors, orthotopic bladder tumors, lymphatic metastasis of tumors and ischemia/reperfusion-induced acute kidney injury in mouse models with multispectral optoacoustic imaging.

Breast cancer brain metastasis: from etiology to state-of-the-art modeling

Currently, breast carcinoma is the most common form of malignancy and the main cause of cancer mortality in women worldwide. The metastasis of cancer cells from the primary tumor site to other organs in the body, notably the lungs, bones, brain, and liver, is what causes breast cancer to ultimately be fatal. Brain metastases occur in as many as 30% of patients with advanced breast cancer, and the 1-year survival rate of these patients is around 20%. Many researchers have focused on brain metastasis, but due to its complexities, many aspects of this process are still relatively unclear. To develop and test novel therapies for this fatal condition, pre-clinical models are required that can mimic the biological processes involved in breast cancer brain metastasis (BCBM). The application of many breakthroughs in the area of tissue engineering has resulted in the development of scaffold or matrix-based culture methods that more accurately imitate the original extracellular matrix (ECM) of metastatic tumors. Furthermore, specific cell lines are now being used to create three-dimensional (3D) cultures that can be used to model metastasis. These 3D cultures satisfy the requirement for in vitro methodologies that allow for a more accurate investigation of the molecular pathways as well as a more in-depth examination of the effects of the medication being tested. In this review, we talk about the latest advances in modeling BCBM using cell lines, animals, and tissue engineering methods.

N-aryltetrahydroisoquinoline derivatives as HA-CD44 interaction inhibitors: Design, synthesis, computational studies, and antitumor effect

Hyaluronic acid (HA) plays a crucial role in tumor growth and invasion through its interaction with cluster of differentiation 44 (CD44), a non-kinase transmembrane glycoprotein, among other hyaladherins. CD44 expression is elevated in many solid tumors, and its interaction with HA is associated with cancer and angiogenesis. Despite efforts to inhibit HA-CD44 interaction, there has been limited progress in the development of small molecule inhibitors. As a contribution to this endeavour, we designed and synthesized a series of N-aryltetrahydroisoquinoline derivatives based on existing crystallographic data available for CD44 and HA. Hit 2e was identified within these structures for its antiproliferative effect against two CD44⁺ cancer cell lines, and two new analogs (5 and 6) were then synthesized and evaluated as CD44-HA inhibitors by applying computational and cell-based CD44 binding studies. Compound 2-(3,4,5-trimethoxybenzyl)-1,2,3,4-tetrahydroisoquinolin-5-ol (5) has an EC₅₀ value of 0.59 μM against MDA-MB-231 cells and is effective to disrupt the integrity of cancer spheroids and reduce the viability of MDA-MB-231 cells in a dose-dependent manner. These results suggest lead 5 as a promising candidate for further investigation in cancer treatment.

Deciphering Common Traits of Breast and Ovarian Cancer Stem Cells and Possible Therapeutic Approaches

Breast cancer (BC) and ovarian cancer (OC) are among the most common and deadly cancers affecting women worldwide. Both are complex diseases with marked heterogeneity. Despite the induction of screening programs that increase the frequency of earlier diagnosis of BC, at a stage when the cancer is more likely to respond to therapy, which does not exist for OC, more than 50% of both cancers are diagnosed at an advanced stage. Initial therapy can put the cancer into remission. However, recurrences occur frequently in both BC and OC, which are highly cancer-subtype dependent. Therapy resistance is mainly attributed to a rare subpopulation of cells, named cancer stem cells (CSC) or tumor-initiating cells, as they are capable of self-renewal, tumor initiation, and regrowth of tumor bulk. In this review, we will discuss the distinctive markers and signaling pathways that characterize CSC, their interactions with the tumor microenvironment, and the strategies they employ to evade immune surveillance. Our focus will be on identifying the common features of breast cancer stem cells (BCSC) and ovarian cancer stem cells (OCSC) and suggesting potential therapeutic approaches.

Hyaluronic Acid-Mediated Phenolic Compound Nanodelivery for Cancer Therapy

Phenolic compounds are bioactive phytochemicals showing a wide range of pharmacological activities, including anti-inflammatory, antioxidant, immunomodulatory, and anticancer effects. Moreover, they are associated with fewer side effects compared to most currently used antitumor drugs. Combinations of phenolic compounds with commonly used drugs have been largely studied as an approach aimed at enhancing the efficacy of anticancer drugs and reducing their deleterious systemic effects. In addition, some of these compounds are reported to reduce tumor cell drug resistance by modulating different signaling pathways. However, often, their application is limited due to their chemical instability, low water solubility, or scarce bioavailability. Nanoformulations, including polyphenols in combination or not with anticancer drugs, represent a suitable strategy to enhance their stability and bioavailability and, thus, improve their therapeutic activity. In recent years, the development of hyaluronic acid-based systems for specific drug delivery to cancer cells has represented a pursued therapeutic strategy. This is related to the fact that this natural polysaccharide binds to the CD44 receptor that is overexpressed in most solid cancers, thus allowing its efficient internalization in tumor cells. Moreover, it is characterized by high biodegradability, biocompatibility, and low toxicity. Here, we will focus on and critically analyze the results obtained in recent studies regarding the use of hyaluronic acid for the targeted delivery of bioactive phenolic compounds to cancer cells of different origins, alone or in combination with drugs.

Convergent Approaches to Delineate the Metabolic Regulation of Tumor Invasion by Hyaluronic Acid Biosynthesis

Metastasis is the leading cause of breast cancer-related deaths and is often driven by invasion and cancer-stem like cells (CSCs). Both the CSC phenotype and invasion are associated with increased hyaluronic acid (HA) production. How these independent observations are connected, and which role metabolism plays in this process, remains unclear due to the lack of convergent approaches integrating engineered model systems, computational tools, and cancer biology. Using microfluidic invasion models, metabolomics, computational flux balance analysis, and bioinformatic analysis of patient data, the functional links between the stem-like, invasive, and metabolic phenotype of breast cancer cells as a function of HA biosynthesis are investigated. These results suggest that CSCs are more invasive than non-CSCs and that broad metabolic changes caused by overproduction of HA play a role in this process. Accordingly, overexpression of hyaluronic acid synthases (HAS) 2 or 3 induces a metabolic phenotype that promotes cancer cell stemness and invasion in vitro and upregulates a transcriptomic signature predictive of increased invasion and worse patient survival. This study suggests that HA overproduction leads to metabolic adaptations to satisfy the energy demands for 3D invasion of breast CSCs highlighting the importance of engineered model systems and multidisciplinary approaches in cancer research.

Maternal Embryonic Leucine Zipper Kinase is Associated with Metastasis in Triple-negative Breast Cancer

Triple-negative breast cancer (TNBC) has high relapse and metastasis rates and a high proportion of cancer stem-like cells (CSC), which possess self-renewal and tumor initiation capacity. MELK (maternal embryonic leucine zipper kinase), a protein kinase of the Snf1/AMPK kinase family, is known to promote CSC maintenance and malignant transformation. However, the role of MELK in TNBC metastasis is unknown; we sought to address this in the current study. We found that MELK mRNA levels were higher in TNBC tumors [8.11 (3.79-10.95)] than in HR+HER2- tumors [6.54 (2.90-9.26)]; P < 0.001]. In univariate analysis, patients with breast cancer with high-MELK-expressing tumors had worse overall survival (P < 0.001) and distant metastasis-free survival (P < 0.01) than patients with low-MELK-expressing tumors. In a multicovariate Cox regression model, high MELK expression was associated with shorter overall survival after adjusting for other baseline risk factors. MELK knockdown using siRNA or MELK inhibition using the MELK inhibitor MELK-In-17 significantly reduced invasiveness, reversed epithelial-to-mesenchymal transition, and reduced CSC self-renewal and maintenance in TNBC cells. Nude mice injected with CRISPR MELK-knockout MDA-MB-231 cells exhibited suppression of lung metastasis and improved overall survival compared with mice injected with control cells (P < 0.05). Furthermore, MELK-In-17 suppressed 4T1 tumor growth in syngeneic BALB/c mice (P < 0.001). Our findings indicate that MELK supports metastasis by promoting epithelial-to-mesenchymal transition and the CSC phenotype in TNBC.

Significance

These findings indicate that MELK is a driver of aggressiveness and metastasis in TNBC.

A human skeletal muscle stem/myotube model reveals multiple signaling targets of cancer secretome in skeletal muscle

Skeletal muscle dysfunction or reprogramming due to the effects of the cancer secretome is observed in multiple malignancies. Although mouse models are routinely used to study skeletal muscle defects in cancer, because of species specificity of certain cytokines/chemokines in the secretome, a human model system is required. Here, we establish simplified multiple skeletal muscle stem cell lines (hMuSCs), which can be differentiated into myotubes. Using single nuclei ATAC-seq (snATAC-seq) and RNA-seq (snRNA-seq), we document chromatin accessibility and transcriptomic changes associated with the transition of hMuSCs to myotubes. Cancer secretome accelerated stem to myotube differentiation, altered the alternative splicing machinery and increased inflammatory, glucocorticoid receptor, and wound healing pathways in hMuSCs. Additionally, cancer secretome reduced metabolic and survival pathway associated miR-486, AKT, and p53 signaling in hMuSCs. hMuSCs underwent myotube differentiation when engrafted into NSG mice and thus providing a humanized in vivo skeletal muscle model system to study cancer cachexia.

TONSL Is an Immortalizing Oncogene and a Therapeutic Target in Breast Cancer

Study of genomic aberrations leading to immortalization of epithelial cells has been technically challenging due to the lack of isogenic models. To address this, we used healthy primary breast luminal epithelial cells of different genetic ancestry and their hTERT-immortalized counterparts to identify transcriptomic changes associated with immortalization. Elevated expression of TONSL (Tonsoku-like, DNA repair protein) was identified as one of the earliest events during immortalization. TONSL, which is located on chromosome 8q24.3, was found to be amplified in approximately 20% of breast cancers. TONSL alone immortalized primary breast epithelial cells and increased telomerase activity, but overexpression was insufficient for neoplastic transformation. However, TONSL-immortalized primary cells overexpressing defined oncogenes generated estrogen receptor-positive adenocarcinomas in mice. Analysis of a breast tumor microarray with approximately 600 tumors revealed poor overall and progression-free survival of patients with TONSL-overexpressing tumors. TONSL increased chromatin accessibility to pro-oncogenic transcription factors, including NF-κB and limited access to the tumor-suppressor p53. TONSL overexpression resulted in significant changes in the expression of genes associated with DNA repair hubs, including upregulation of several genes in the homologous recombination (HR) and Fanconi anemia pathways. Consistent with these results, TONSL-overexpressing primary cells exhibited upregulated DNA repair via HR. Moreover, TONSL was essential for growth of TONSL-amplified breast cancer cell lines in vivo, and these cells were sensitive to TONSL-FACT complex inhibitor CBL0137. Together, these findings identify TONSL as a regulator of epithelial cell immortalization to facilitate cancer initiation and as a target for breast cancer therapy.

SIGNIFICANCE

The chr.8q24.3 amplicon-resident gene TONSL is upregulated during the initial steps of tumorigenesis to support neoplastic transformation by increasing DNA repair and represents a potential therapeutic target for treating breast cancer.