Human Mammary Epithelial Cells Research Articles

Cold plasma irradiation of chitosan: A straight pathway to selective antitumor therapy

Plasma-activated chitosan (PAC) colloids for cancer treatment were obtained by using the cold atmospheric plasma technique. Chitosan solutions were irradiated by plasma ignited in argon gas and in a mixture of argon with nitrogen and oxygen gases in certain ratios. The structural modifications of chitosan and the chemical species generated in plasma were investigated by EPR, LC-MS/MS, XRD, and NanoSight methods. The cell viability test showed a selective cytotoxic effect on human breast carcinoma cells (MCF-7), while the human mammary epithelial cells (MCF-10A) were left unharmed. The cytotoxic effect was attributed mainly to chitooligosaccharides, but also to a synergistic effect with other compounds generated in very low concentrations in plasma, such as glyceric acid, ethyl acetate, or tricarballylic acid. The plasma irradiation improved the antioxidant activity and mucoadhesivity, while not affecting the hemocompatibility investigated by a standard hemolysis ex vivo test on mice blood. Moreover, the in vivo biocompatibility investigation at intraperitoneal administration of PAC in mice showed no statistically significant changes in the hematologic, biochemical, and immune system parameters, and no morphologic alterations of the liver and kidney. All these data indicate the cold plasma activation of chitosan as a straight method to produce biocompatible, antitumor systems.

Development and Characterization of a Human Mammary Epithelial Cell Culture Model for the Blood–Milk Barrier—A Contribution from the ConcePTION Project

It is currently impossible to perform an evidence-based risk assessment for medication use during breastfeeding. The ConcePTION project aims to provide information about the use of medicines during lactation. The study aimed to develop and characterize an in vitro model of the blood–milk barrier to determine the extent of the milk transfer of xenobiotics, relying on either on human mammary epithelial cells (hMECs) or immortalized cell lines derived from breast tissue. The hMECs were cultured and characterized for epithelial markers; further, the ability to form an epithelial barrier was investigated. Drug transporter functionality in the cultured hMECs was analyzed with specific probe substrates. The hMECs showed an epithelial morphology and the expression of epithelial markers and tight junctions. They formed a reproducible tight barrier with a transepithelial electrical resistance greater than 400 Ωcm2, unlike immortalized cell lines. Different levels of mRNA expression were detected for 81 genes of membrane transporters. Functional assays showed no evidence for the transporter-mediated secretion of medicines across the hMECs. Nevertheless, the hMEC-based in vitro model covered a 50-fold range of permeability values, differentiating between passive transcellular and paracellular-mediated transport. The cultured hMECs proved to be a promising in vitro model for biorelevance; the wide characterization of hMECs makes them useful for studying medicine partitioning in milk.

Activation of Mammary Epithelial and Stromal Fibroblasts upon Exposure to Escherichia coli Metabolites.

Breast cancer is the leading cause of cancer death among women worldwide. The mammary gland is composed of various types of cells including luminal cells, fibroblasts, immune cells, adipocytes, and specific microbiota. The reciprocal interaction between these multiple types of cells can dictate the initiation and progression of cancer, as well as metastasis and response to therapy. In the present report, we have shown that Escherichia coli-conditioned media (E-CM) can directly activate human mammary luminal epithelial cells (HMLEs), by inducing epithelial-to-mesenchymal transition (EMT), a process associated with increased proliferation and invasion capacities, as well as stemness features. Additionally, it has been shown that E-CM has an indirect pro-carcinogenic effect, mediated by the activation of normal breast fibroblasts (NBFs). Indeed, E-CM upregulated various markers of active fibroblasts (FAP-α, GPR77, and CD10), and enhanced the proliferation, migration, and invasion capacities of NBFs. Furthermore, E-CM induced an inflammatory response in NBFs by activating the pro-inflammatory NF-kB transcription factor and several of its downstream target cytokines including IL-1β, IL-6, and IL-8. This E-CM-dependent activation of NBFs was confirmed by showing their paracrine pro-carcinogenic effects through inducing EMT and stemness features in normal breast epithelial cells. Interestingly, similar effects were obtained by recombinant human IL-1β. These results provide the first indication that E. coli can initiate breast carcinogenesis through the activation of breast stromal fibroblasts and their paracrine pro-carcinogenic effects.

The Apoptotic, Cytotoxic, and Anti-migration Effects of Sodium Deoxycholate in a Breast Cancer Cell Line and its Modulation on PON1 as a Predictive Risk Marker.

Breast cancer is the most prevalent cancer among women and is usually treated with antineoplastic drugs. The present study examines the influence of sodium deoxycholate on the molecular pathways underlying apoptosis, cytotoxicity, and the modulation of PON1 in the MCF-7 breast cancer cell line. Various doses were administered to test the hypothesis that it could potentially affect cancer cells. The study examined the cytotoxic effect of sodium deoxycholate on MCF-7 cells and human mammary epithelial cells (CRL-4010) using the MTT method to detect its anticancer properties. Subsequently, the efficacy of the active dose on DNA fragmentation and apoptosis was examined using the apoptotic DNA ladder and Western blot methods. Additionally, oxidative stress index and cell migration tests were conducted. Notably, sodium deoxycholate did not cause DNA damage despite demonstrating cytotoxic effects on cells. The study found that sodium deoxycholate increased the levels of several pro-apoptotic proteins, leading to apoptosis. Moreover, it markedly diminishes the activity of paraoxonase and arylesterase of PON1, which are predictive risk markers for cancer. Furthermore, it was found to delay cell migration in a time-dependent manner. These findings suggest that sodium deoxycholate exhibits an antimetastatic effect in breast cancer cells, could be a valuable subject for further cancer research.

An adaptive Epithelial-Mesenchymal Transition Program Enables Basal Epithelial Cells to Bypass Stress-Induced Stasis and Contributes to Metaplastic Breast Cancer Progenitor State.

Human mammary epithelial cell (HMEC) cultures encounter a stress-associated barrier termed stasis, during which most cells adopt a senescence-like phenotype. From these cultures, rare variants emerge from the basal epithelial population, re-initiating growth. Variants exhibit pre-malignant properties, including an aberrant epigenetic program that enables continued proliferation and acquisition of genetic changes. Following oncogenic transformation, variants produce tumors that recapitulate the histopathological characteristics of metaplastic breast cancer (MBC), a rare subtype characterized by squamous and mesenchymal differentiation. Using the conventional serum-free HMEC culture system, we probed the capacity for phenotypic plasticity inherent to basal epithelial cell populations from human breast tissue as they navigated stasis and emerged as variant populations. We observed robust activation of a TGF-β-dependent epithelial-mesenchymal transition (EMT) program in basal epithelial cells during stasis, followed by subsequent attenuation of this program in emerging variants. Inhibiting the TGF-β pathway or depleting the EMT regulators Snail or Slug allowed basal epithelial cells to collectively bypass stasis, demonstrating that cellular dysfunction and arrest resulting from TGF-β and EMT activation are central to this in vitro barrier. The spontaneous emergence of variants from stasis cultures was associated with a restricted EMT trajectory, which diverted cells away from a complete mesenchymal state characterized by irreversible growth arrest, and instead limited variants to epithelial and intermediate EMT states associated with greater proliferative capacity and stemness. Epigenetic mechanisms, which contributed to the dysregulated growth control characteristic of the variant phenotype, also contributed to the constrained EMT program in variants. By overcoming the cellular dysfunction and growth arrest resulting from TGF-β and EMT activation, variants exhibited increased oncogenic transformation efficiency compared to pre-stasis basal epithelial cells. Inhibiting the TGF-β pathway prior to stasis significantly reduced EMT in the basal epithelial population, alleviated selective pressure driving variant emergence, and enhanced oncogenic transformation efficiency, resulting in tumors with markedly diminished metaplastic differentiation. This study reveals how adaptive EMT reprogramming governs basal epithelial cell fate decisions and contributes to the development of MBC progenitors by restricting access to terminal mesenchymal states that induce growth arrest and, instead, favoring intermediate states with enhanced tumorigenic potential.

Multi‐Zone Visco‐Node‐Pore Sensing: A Microfluidic Platform for Multi‐Frequency Viscoelastic Phenotyping of Single Cells

AbstractThis study introduces multi‐zone visco‐Node‐Pore Sensing (mz‐visco‐NPS), an electronic‐based microfluidic platform for single‐cell viscoelastic phenotyping. mz‐visco‐NPS implements a series of sinusoidal‐shaped contraction zones that periodically deform a cell at specific strain frequencies, leading to changes in resistance across the zones that correspond to the cell's frequency‐dependent elastic G′ and viscous G″ moduli. mz‐visco‐NPS is validated by measuring the viscoelastic changes of MCF‐7 cells when their cytoskeleton is disrupted. mz‐visco‐NPS is also employed to measure the viscoelastic properties of human mammary epithelial cells across the entire continuum of epithelial transformation states, from average‐ and high‐risk primary epithelial cells, to immortal non‐malignant (MCF‐10A), malignant (MCF‐7), and metastatic (MDA‐MB‐231) cell lines. With a throughput of 600 cells per hour and demonstrated ease‐of‐use, mz‐visco‐NPS reveals a remarkable level of single‐cell heterogeneity that would otherwise be masked by ensemble averaging.

The chromatin remodeler DEK promotes proliferation of mammary epithelium and is associated with H3K27me3 epigenetic modifications.

The DEK chromatin remodeling protein was previously shown to confer oncogenic phenotypes to human and mouse mammary epithelial cells using in vitro and knockout mouse models. However, its functional role in normal mammary gland epithelium remained unexplored. We developed two novel mouse models to study the role of Dek in normal mammary gland biology in vivo . Mammary gland-specific Dek over-expression in mice resulted in hyperproliferation of cells that visually resembled alveolar cells, and a transcriptional profile that indicated increased expression of cell cycle, mammary stem/progenitor, and lactation-associated genes. Conversely, Dek knockout mice exhibited an alveologenesis or lactation defect, resulting in dramatically reduced pup survival. Analysis of previously published single-cell RNA-sequencing of mouse mammary glands revealed that Dek is most highly expressed in mammary stem cells and alveolar progenitor cells, and to a lesser extent in basal epithelial cells, supporting the observed phenotypes. Mechanistically, we discovered that Dek is a modifier of Ezh2 methyltransferase activity, upregulating the levels of histone H3 trimethylation on lysine 27 (H3K27me3) to control gene transcription. Combined, this work indicates that Dek promotes proliferation of mammary epithelial cells via cell cycle deregulation. Furthermore, we report a novel function for Dek in alveologenesis and histone H3 K27 trimethylation.

Polyploid Giant Cancer Cells: A Distinctive Feature in the Transformation of Epithelial Cells by High-Risk Oncogenic HCMV Strains.

Human cytomegalovirus (HCMV) infection is common in tumor tissues across different types of cancer. While HCMV has not been recognized as a cancer-causing virus, numerous studies hint at its potential role in cancer development where its presence in various cancers corresponds with the hallmarks of cancer. Herein, we discuss and demonstrate that high-risk HCMV-DB and BL strains have the potential to trigger transformation in epithelial cells, including human mammary epithelial cells (HMECs), ovarian epithelial cells (OECs), and prostate epithelial cells (PECs), through the generation of polyploid giant cancer cells (PGCCs). A discussion is provided on how HCMV infection creates a cellular environment that promotes oncogenesis, supporting the continuous growth of CMV-transformed cells. The aforementioned transformed cells, named CTH, CTO, and CTP cells, underwent giant cell cycling with PGCC generation parallel to dedifferentiation, displaying stem-like characteristics and an epithelial-mesenchymal transition (EMT) phenotype. Furthermore, we propose that giant cell cycling through PGCCs, increased EZH2 expression, EMT, and the acquisition of malignant traits represent a deleterious response to the cellular stress induced by high-risk oncogenic HCMV strains, the latter being the origin of the transformation process in epithelial cells upon HCMV infection and leading to adenocarcinoma of poor prognosis.

Theranostics Using MCM-41-Based Mesoporous Silica Nanoparticles: Integrating Magnetic Resonance Imaging and Novel Chemotherapy for Breast Cancer Treatment.

Advanced breast cancer remains a significant oncological challenge, requiring new approaches to improve clinical outcomes. This study investigated an innovative theranostic agent using the MCM-41-NH2-DTPA-Gd3⁺-MIH nanomaterial, which combined MRI imaging for detection and a novel chemotherapy agent (MIH 2.4Bl) for treatment. The nanomaterial was based on the mesoporous silica type, MCM-41, and was optimized for drug delivery via functionalization with amine groups and conjugation with DTPA and complexation with Gd3+. MRI sensitivity was enhanced by using gadolinium-based contrast agents, which are crucial in identifying early neoplastic lesions. MIH 2.4Bl, with its unique mesoionic structure, allows effective interactions with biomolecules that facilitate its intracellular antitumoral activity. Physicochemical characterization confirmed the nanomaterial synthesis and effective drug incorporation, with 15% of MIH 2.4Bl being adsorbed. Drug release assays indicated that approximately 50% was released within 8 h. MRI phantom studies demonstrated the superior imaging capability of the nanomaterial, with a relaxivity significantly higher than that of the commercial agent Magnevist. In vitro cellular cytotoxicity assays, the effectiveness of the nanomaterial in killing MDA-MB-231 breast cancer cells was demonstrated at an EC50 concentration of 12.6 mg/mL compared to an EC50 concentration of 68.9 mg/mL in normal human mammary epithelial cells (HMECs). In vivo, MRI evaluation in a 4T1 syngeneic mouse model confirmed its efficacy as a contrast agent. This study highlighted the theranostic capabilities of MCM-41-NH2-DTPA-Gd3⁺-MIH and its potential to enhance breast cancer management.

Manuka Honey Inhibits Human Breast Cancer Progression in Preclinical Models.

Manuka honey (MH) exhibits potential antitumor activity in preclinical models of a number of human cancers. Treatment in vitro with MH at concentrations ranging from 0.3 to 5.0% (w/v) led to significant dose-dependent inhibition of proliferation of human breast cancer MCF-7 cells, but anti-proliferative effects of MH were less pronounced in MDA-MB-231 breast cancer cells. Effects of MH were also tested on non-malignant human mammary epithelial cells (HMECs) at 2.5% w/v, and it was found that MH reduced the proliferation of MCF-7 cells but not that of HMECs. Notably, the antitumor activity of MH was in the range of that exerted by treatment of MCF-7 cells with the antiestrogen tamoxifen. Further, MH treatment stimulated apoptosis of MCF-7 cells in vitro, with most cells exhibiting acute and significant levels of apoptosis that correlated with PARP activation. Additionally, the effects of MH induced the activation of AMPK and inhibition of AKT/mTOR downstream signaling. Treatment of MCF7 cells with increased concentrations of MH induced AMPK phosphorylation in a dose-dependent manner that was accompanied by inhibition of phosphorylation of AKT and mTOR downstream effector protein S6. In addition, MH reduced phosphorylated STAT3 levels in vitro, which may correlate with MH and AMPK-mediated anti-inflammatory properties. Further, in vivo, MH administered alone significantly inhibited the growth of established MCF-7 tumors in nude mice by 84%, resulting in an observable reduction in tumor volume. Our findings highlight the need for further research into the use of natural compounds, such as MH, for antitumor efficacy and potential chemoprevention and investigation of molecular pathways underlying these actions.

Enhanced Stability of α-Mangostin-Rich Extract and Selective Cytotoxicity against Cancer Cells via Encapsulation in Antioxidant Nanoparticles (AME@NanoAOX).

α-Mangostin-rich extract (AME) shows promise as a functional ingredient for cancer chemotherapy. Here, we encapsulated AME in our originally designed antioxidant nanoparticles (NanoAOX) to increase its solubility and prevent oxidative degradation (AME@NanoAOX). In this study, two types of self-assembled polymers containing nitroxide radicals were engineered. These polymers were self-assembled into nanoscale particles in aqueous media, entrapping AME (abbreviated as AME@NanoAOX(B) and AME@NanoAOX(G)). These formulations considerably improved the stability of AME against oxidative degradation and exhibited different release profiles of α-mangostin under different pH conditions. Furthermore, AME-encapsulated nanoparticles exhibited potent cytotoxicity against various cancer cell lines, including human breast cancer (MCF-7), human lung cancer (A549), human colon cancer (Caco-2), human cervical cancer (HeLa), and human liver cancer (HepG2) cell lines, with minimal cytotoxicity in normal human mammary epithelial cells (hTERT-HME1), thus providing a high selectivity index (SI). These results indicated the promising feature of AME-encapsulated antioxidant nanoparticles (AME@NanoAOX) for cancer chemotherapy.

Overexpression of CDHR2 inhibits proliferation of breast cancer cells by inhibiting the PI3K/Akt pathway

To investigate the mechanism by which CDHR2 overexpression inhibits breast cancer cell growth and cell cycle pragression via the PI3K/Akt signaling pathway. Bioinformatic analysis was performed to investigate CDHR2 expression in breast cancer and its correlation with survival outcomes of the patients. Immunohistochemistry was used to examine CDHR2 expressions in surgical specimens of tumor and adjacent tissues from 10 patients with breast cancer. CDHR2 expression levels were also detected in 5 breast cancer cell lines and a normal human mammary epithelial cell line using qRT-PCR and Western blotting. Breast cancer cell lines MDA-MB-231 and MCF7 with low CDHR2 expression were transfected with a CDHR2-overexpressing plasmid, and the changes in cell proliferation and cell cycle were evaluated using CCK-8 assay, EdU assay, and cell cycle assay; the changes in expressions of PI3K/Akt signaling pathway and cell cycle pathway proteins were detected with Western blotting. Bioinformatic analysis showed low CDHR2 expression level in both breast cancer and adjacent tissues without significant difference between them (P > 0.05), but breast cancer patients with a high expression of CDHR2 had a more favorable prognosis. Immunohistochemistry, qRT-PCR and Western blotting showed that the expression of CDHR2 was significantly down-regulated in breast cancer tissues and breast cancer cells (P < 0.01), and its overexpression strongly inhibited cell proliferation, caused cell cycle arrest, and significantly inhibited PI3K and Akt phosphorylation and the expression of cyclin D1. Overexpression of CDHR2 inhibits proliferation and causes cell cycle arrest in breast cancer cells possibly by inhibiting the PI3K/Akt signaling pathway.

Polymeric Micellar Nanoparticles Enable Image-guided Drug Delivery in Solid Tumors.

We report the development of a nanotechnology to co-deliver chemocoxib A with a reactive oxygen species (ROS)-activatable and COX-2 targeted pro-fluorescent probe, fluorocoxib Q (FQ) enabling real time visualization of COX-2 and CA drug delivery into solid cancers, using a di-block PPS 135 - b -POEGA 17 copolymer, selected for its intrinsic responsiveness to elevated reactive oxygen species (ROS), a key trait of the tumor microenvironment. FQ and CA were synthesized independently, then co-encapsulated within micellar PPS 135 - b -POEGA 17 co-polymeric nanoparticles (FQ-CA-NPs), and were assessed for cargo concentration, hydrodynamic diameter, zeta potential, and ROS-dependent cargo release. The uptake of FQ-CA-NPs in mouse mammary cancer cells and cargo release was assessed by fluorescence microscopy. Intravenous delivery of FQ-CA-NPs to mice harboring orthotopic mammary tumors, followed by vital optimal imaging, was used to assess delivery to tumors in vivo . The CA-FQ-NPs exhibited a hydrodynamic diameter of 109.2 ± 4.1 nm and a zeta potential (σ) of -1.59 ± 0.3 mV. Fluorescence microscopy showed ROS-dependent cargo release by FQ-CA-NPs in 4T1 cells, decreasing growth of 4T1 breast cancer cells, but not affecting growth of primary human mammary epithelial cells (HMECs). NP-derived fluorescence was detected in mammary tumors, but not in healthy organs. Tumor LC-MS/MS analysis identified both CA (2.38 nmol/g tumor tissue) and FQ (0.115 nmol/g tumor tissue), confirming the FQ-mediated image guidance of CA delivery in solid tumors. Thus, co-encapsulation of FQ and CA into micellar nanoparticles (FQ-CA-NPs) enabled ROS-sensitive drug release and COX-2-targeted visualization of solid tumors.

The basement membrane regulates the cellular localization and the cytoplasmic interactome of Yes-Associated Protein (YAP) in mammary epithelial cells.

The Hippo pathway, a signaling cascade involved in the regulation of organ size and several other processes, acts as a conduit between extracellular matrix (ECM) cues and cellular responses. We asked whether the basement membrane (BM),a specialized ECM component known to induce quiescence and differentiation in mammary epithelial cells, would regulate the localization, activity, and interactome of YAP, a Hippo pathway effector. To address this question, we used a broad range of experimental approaches, including 2D and 3D cultures of both mouse and human mammary epithelial cells, as well as the developing mouse mammary gland. In contrast to malignant cells, nontumoral cells cultured with a reconstituted BM (rBM)displayed higher concentrations of YAP in the cytoplasm. Incidentally, when in the nucleus of rBM-treated cells, YAP resided preferentially at the nuclear periphery. In agreement with our cell culture experiments, YAP exhibited cytoplasmic predominance in ductal cells of developing mammary epithelia, where a denser BM is found. Conversely, terminal end bud (TEB)cells with a thinner BM displayed higher nucleus-to-cytoplasm ratios of YAP. Bioinformatic analysis revealed that genes regulated by YAP were overrepresented in the transcriptomes of microdissected TEBs. Consistently, mouse epithelial cells exposed to the rBM expressed lower levels of YAP-regulated genes, although the protein level of YAP and Hippo components were slightly altered by the treatment. Mass spectrometry analysis identified a differential set of proteins interacting with YAP in cytoplasmic fractions of mouse epithelial cells in the absence or presence of rBM. In untreated cells, YAP interactants were enriched in processes related to ubiquitin-mediated proteolysis, whereas in cells exposed to rBM YAP interactants were mainly key proteins related to amino acid, amino sugar, and carbohydrate metabolism. Collectively, we unraveled that the BM induces YAP translocation or retention in the cytoplasm of nontumoral epithelial cells and that in the cytoplasm YAP seems to undertake novel functions in metabolic pathways.

Loss of RAB25 Cooperates with Oncogenes in the Transformation of Human Mammary Epithelial Cells (HMECs) to Give Rise to Claudin-Low Tumors.

The loss of RAB25 expression-RAS superfamily of GTPase characteristic of numerous breast cancers-corresponds with H-RAS point mutations, particularly in triple-negative breast cancers (TNBC), a subtype associated with a poor prognosis. To address the poorly understood factors dictating the progression of TNBC tumors, we examine the cooperative effects that loss of RAB25 expression in human mammary epithelial cell (HMEC) lines with H-RAS mutations confers in tumorigenesis. HMECs were immortalized by transduction with LXSN CDK4 R24C, a mutant form of cyclin-dependent kinase, followed by transduction with hTERT, a catalytic subunit of the telomerase enzyme. We found that with the loss of RAB25 and overexpression of mutant H-RAS61L, immortal HMECs transformed toward anchorage-independent growth and acquired an increased ability to migrate. Furthermore, cells express low CD24, high CD44, and low claudin levels, indicating stem-like properties upon transformation. Besides, loss of RAB25 and overexpression of H-RAS61L resulted in increased expression of transcription factors Snail and Slug that drive these cells to lose E-cadherin and undergo epithelial-mesenchymal transition (EMT). This study confirms that loss of RAB25 and overexpression of mutant H-RAS can drive HMECs toward a mesenchymal stem-like state. Our findings reveal that RAB25 functions as a tumor suppressor gene, and loss of RAB25 could serve as a novel biomarker of the claudin-low type of TNBC.

PI 3-Kinase and the Histone Methyl-Transferase KMT2D Collaborate to Induce Arp2/3-Dependent Migration of Mammary Epithelial Cells.

Breast cancer develops upon sequential acquisition of driver mutations in mammary epithelial cells; however, how these mutations collaborate to transform normal cells remains unclear in most cases. We aimed to reconstitute this process in a particular case. To this end, we combined the activated form of the PI 3-kinase harboring the H1047R mutation with the inactivation of the histone lysine methyl-transferase KMT2D in the non-tumorigenic human mammary epithelial cell line MCF10A. We found that PI 3-kinase activation promoted cell-cycle progression, especially when growth signals were limiting, as well as cell migration, both in a collective monolayer and as single cells. Furthermore, we showed that KMT2D inactivation had relatively little influence on these processes, except for single-cell migration, which KMT2D inactivation promoted in synergy with PI 3-kinase activation. The combination of these two genetic alterations induced expression of the ARPC5L gene that encodes a subunit of the Arp2/3 complex. ARPC5L depletion fully abolished the enhanced migration persistence exhibited by double-mutant cells. Our reconstitution approach in MCF10A has thus revealed both the cell function and the single-cell migration, and the underlying Arp2/3-dependent mechanism, which are synergistically regulated when KMT2D inactivation is combined with the activation of the PI 3-kinase.

Isolation and Culture of Primary Human Mammary Epithelial Cells.

The mammary gland is a fundamental structure of the breast and plays an essential role in reproduction. Human mammary epithelial cells (HMECs), which are the origin cells of breast cancer and other breast-related inflammatory diseases, have garnered considerable attention. However, isolating and culturing primary HMECs in vitro for research purposes has been challenging due to their highly differentiated, keratinized nature and their short lifespan. Therefore, developing a simple and efficient method to isolate and culture HMECs is of great scientific value for the study of breast biology and breast-related diseases. In this study, we successfully isolated primary HMECs from small amounts of mammary tissue by digestion with a mixture of enzymes combined with an initial culture in 5% fetal bovine serum-DMEM containing the Rho-associated kinase (ROCK) inhibitor Y-27632, followed by culture expansion in serum-free keratinocyte medium. This approach selectively promotes the growth of epithelial cells, resulting in an optimized cell yield. The simplicity and convenience of this method make it suitable for both laboratory and clinical research, which should provide valuable insights into these important areas of study.

Abstract PO1-16-04: Targeting PKMYT1 Kinase as a Therapeutic Strategy for Treatment of Triple Negative Breast Cancer with Low Molecular Weight Cyclin E (LMW-E) Expression

Abstract Purpose: Low molecular weight isoforms of cyclin E (LMW-E) have been implicated in various human cancers, including triple negative breast cancer (TNBC), and are associated with a poor prognosis. However, targeted therapies for TNBC based on biomarkers are currently lacking. This study aims to investigate LMW-E as a potential therapeutic target in TNBC and evaluate the efficacy of RP-6306, a selective inhibitor of the Protein Kinase, Membrane Associated Tyrosine/Threonine 1 (PKMYT1), in LMW-E-positive breast tumors. Experimental Design: Immunohistochemical (IHC) analysis was performed on pre-treatment tumor specimens from TNBC patients (n=36) to assess the correlation between LMW-E expression, CDK1 phosphorylation at Threonine 14 (pT14), and pathologic complete response to neoadjuvant chemotherapy. LMW-E inducible human mammary epithelial cells (hMEC) and breast cancer cell lines were used to investigate the regulatory effect of LMW-E on PKMYT1, the kinase responsible for CDK1 phosphorylation at T14, and the response to RP-6306, a first in-class and selective inhibitor of PKMYT1. Patient-derived xenograft (PDX) models and transgenic mouse mammary tumor virus (MMTV) models of TNBC expressing human LMW-E (hLMW-E) were also utilized to assess LMW-E as a biomarker for predicting response to RP-6306. Results. Analysis of TNBC tumor biopsies revealed a significant positive correlation between LMW-E expression and CDK1 pT14, and both biomarkers were associated with a lack of pathological complete response to neoadjuvant chemotherapy. In vitro results using LMW-E inducible hMECs and breast cancer cell lines demonstrated that LMW-E up-regulates PKMYT1 and CDK1 pT14, acting as a PKMYT1 binding protein and enhancing PKMYT1 protein stability. High LMW-E protein levels predicted a favorable response to RP-6306, resulting in the accumulation of sub-G1 and polyploid cells, decreased tolerance to replication stress, increased DNA damage, chromosomal breakage, and apoptosis. In vivo treatment of TNBC PDX models and hLMW-E transgenic tumors with RP-6306 resulted in a significant reduction in tumor volume only in mice harboring high LMW-E tumors, while low cyclin E models showed no response. Immunohistochemical analysis confirmed increased γ-H2AX and decreased CDK1-pT14 and Ki67 levels, indicating the efficacy of RP-6306 in both PDX and transgenic models. Conclusion: This study highlights the regulatory axis from LMW-E to PKMYT1 and its predictive value for pathological complete response in TNBC patients receiving neoadjuvant chemotherapy. The selective PKMYT1 kinase inhibitor RP-6306 consistently induced DNA damage and inhibited tumor growth in in vitro and in vivo pre-clinical breast tumor models. Co-expression of LMW-E and CDK1-pT14 in TNBC can be used to stratify patients whose tumors are likely to respond to RP-6306, emphasizing its therapeutic significance. Citation Format: Mi Li, Amriti Lulla, Cansu Karakas, Spiridon Tsavaschidis, Yan Wang, Tuyen Nguyun, Tuyen Bui, Gary Marshall, Kelly Hunt, Khandan Keyomarsi. Targeting PKMYT1 Kinase as a Therapeutic Strategy for Treatment of Triple Negative Breast Cancer with Low Molecular Weight Cyclin E (LMW-E) Expression [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-16-04.

249 Defining the Role of Hedgehog Signaling in Breast Cancer Risk of non-Hispanic Black Women

OBJECTIVES/GOALS: The molecular basis of increased risk of triple negative breast cancer in non-Hispanic Black women represents a critical knowledge gap that this research is designed to address; successful completion of this work could lead to better prevention, earlier stage diagnoses, and possible discovery of novel therapeutic strategies for this population. METHODS/STUDY POPULATION: We have recently generated a living tissue cohort of 11 non-Hispanic Black and 25 non-Hispanic White women who underwent breast surgery at Mayo Clinic. Gene expression profiling of normal breast tissue from this cohort has identified a pattern of gene expression differences that have been associated with the development of basal breast cancer and are also reflective of Hedgehog (Hh) signaling. We will identify protein-based biomarkers for Hedgehog signaling within normal breast tissue using immunohistochemistry methods. We will culture primary human mammary epithelial cells and further separate luminal and myoepithelial cells using flow cytometry to then decipher Hedgehog signaling. RESULTS/ANTICIPATED RESULTS: We anticipate identifying and localizing protein-based biomarkers for Hedgehog signaling within myoepithelial cells of non-Hispanic Black women. Using our findings, we aim to create a biomarker risk model for triple negative breast cancer and validate this model within a separate and larger cohort of women to predict breast cancer risk. DISCUSSION/SIGNIFICANCE: In addition to immediate benefits from improved risk prediction, the proposed work has the potential to provide new insight into the driving forces underlying basal breast carcinogenesis and the distinct biological differences that distinguish non-Hispanic Black women from non-Hispanic White women.

Dipeptidyl-peptidase 9 regulates the dynamics of tumorigenesis and metastasis in breast cancer

The cytosolic dipeptidyl-aminopeptidase 9 (DPP9) cleaves protein N-termini post-proline or -alanine. Our analysis of DPP9 mRNA expression from the TCGA ‘breast cancer’ data set revealed that low/intermediate DPP9 levels are associated with poor overall survival of breast cancer patients. To unravel the impact of DPP9 on breast cancer development and progression, the transgenic MMTV-PyMT mouse model of metastasizing breast cancer was used. In addition, tissue- and time-controlled genetic deletion of DPP9 by the Cre-loxP recombination system was done. Despite a delay of tumor onset, a higher number of lung metastases were measured in DPP9-deficient mice compared to controls. In human mammary epithelial cells with oncogenic RAS pathway activation, DPP9 deficiency delayed tumorigenic transformation and accelerated TGF-β1 induced epithelial-to-mesenchymal transition (EMT) of spheroids. For further analysis of the mechanism, primary breast tumor cells were isolated from the MMTV-PyMT model. DPP9 deficiency in these cells caused cancer cell migration and invasion accompanied by EMT. In absence of DPP9, the EMT transcription factor ZEB1 was stabilized due to insufficient degradation by the proteasome. In summary, low expression of DPP9 appears to decelerate mammary tumorigenesis but favors EMT and metastasis, which establishes DPP9 as a novel dynamic regulator of breast cancer initiation and progression.