Epigenetic deregulation in breast cancer microenvironment: Implications for tumor progression and therapeutic strategies.

Breast cancer comprises a substantial proportion of cancer diagnoses in women and is a primary cause of cancer-related mortality. While hormone-responsive cases generally have a favorable prognosis, the aggressive nature of triple-negative breast cancer presents challenges, with intrinsic resistance to established treatments being a persistent issue. The complexity intensifies with the emergence of acquired resistance, further complicating the management of breast cancer. Epigenetic changes, encompassing DNA methylation, histone and RNA modifications, and non-coding RNAs, are acknowledged as crucial contributors to the heterogeneity of breast cancer. The unique epigenetic landscape harbored by each cellular component within the tumor microenvironment (TME) adds great diversity to the intricate regulations which influence therapeutic responses. The TME, a sophisticated ecosystem of cellular and non-cellular elements interacting with tumor cells, establishes an immunosuppressive microenvironment and fuels processes such as tumor growth, angiogenesis, and extracellular matrix remodeling. These factors contribute to challenging conditions in cancer treatment by fostering a hypoxic environment, inducing metabolic stress, and creating physical barriers to drug delivery. This article delves into the complex connections between breast cancer treatment response, underlying epigenetic changes, and vital interactions within the TME. To restore sensitivity to treatment, it emphasizes the need for combination therapies considering epigenetic changes specific to individual members of the TME. Recognizing the pivotal role of epigenetics in drug resistance and comprehending the specificities of breast TME is essential for devising more effective therapeutic strategies. The development of reliable biomarkers for patient stratification will facilitate tailored and precise treatment approaches.

Novel model of triple-negative breast cancer produces viable circulating tumor cells and rapid lung metastasis for functional testing in vivo.

Breast cancer metastases are the main reason for women´s highest cancer mortality. Even though tumor cell dissemination via circulating tumor cells (CTC) released from the primary site is a very ineffective process, distant metastases appear in 46% of triple-negative breast cancer (TNBC) patients corresponding to the disease aggressiveness. Laboratory models for functional testing which mimic the spread of metastatic cells are needed for efficient investigation of the underlying mechanisms and therapeutic intervention. Here, we describe novel isogenic variants LMC3 and CTC3 of human TNBC cell line MDA-MB-231 that were derived by repeated injection of tumor cells into the tail vein of immunodeficient mice and subsequent selection of metastatic cells from lung metastases. These variants have increased migration potential, altered expression profiles, and elevated tumorigenic potential. Moreover, cell line CTC3 readily produces metastases in the lungs and bone marrow and detectable viable circulating tumor cells in the blood. This model enables rapid and cost-efficient strategies for biomarker exploration and novel intervention approaches to limit the CTC presence in the blood and hence tumor dissemination.

The third dimension of tumor microenvironment-The importance of tumor stroma in 3D cancer models.

Recent advances in the three-dimensional (3D) cancer models give rise to a plethora of new possibilities in the development of anti-cancer drug therapies and bring us closer to personalized medicine. Three-dimensional models are undoubtedly more authentic than traditional two-dimensional (2D) cell cultures. Nowadays, they are becoming preferentially used in most cancer research fields due to their more accurate biomimetic characteristics. On the contrary, they still lack the cellular and matrix complexity of the native tumor microenvironment (TME). This review focuses on the description of existing 3D models, the incorporation of TME and fluidics into these models, and their perspective in the future research. It is clear that such an improvement would need not only biological but also technical progress. Therefore, the modern approach to anti-cancer drug discovery should involve various fields.

DNA Methylation Mediates EMT Gene Expression in Human Pancreatic Ductal Adenocarcinoma Cell Lines.

Due to abundant stroma and extracellular matrix, accompanied by lack of vascularization, pancreatic ductal adenocarcinoma (PDAC) is characterized by severe hypoxia. Epigenetic regulation is likely one of the mechanisms driving hypoxia-induced epithelial-to-mesenchymal transition (EMT), responsible for PDAC aggressiveness and dismal prognosis. To verify the role of DNA methylation in this process, we assessed gene expression and DNA methylation changes in four PDAC cell lines. BxPC-3, MIA PaCa-2, PANC-1, and SU.86.86 cells were exposed to conditioned media containing cytokines and inflammatory molecules in normoxic and hypoxic (1% O2) conditions for 2 and 6 days. Cancer Inflammation and Immunity Crosstalk and Human Epithelial to Mesenchymal Transition RT² Profiler PCR Arrays were used to identify top deregulated inflammatory and EMT-related genes. Their mRNA expression and DNA methylation were quantified by qRT-PCR and pyrosequencing. BxPC-3 and SU.86.86 cell lines were the most sensitive to hypoxia and inflammation. Although the methylation of gene promoters correlated with gene expression negatively, it was not significantly influenced by experimental conditions. However, DNA methyltransferase inhibitor decitabine efficiently decreased DNA methylation up to 53% and reactivated all silenced genes. These results confirm the role of DNA methylation in EMT-related gene regulation and uncover possible new targets involved in PDAC progression.

Decitabine potentiates efficacy of doxorubicin in a preclinical trastuzumab-resistant HER2-positive breast cancer models.

Acquired drug resistance and metastasis in breast cancer (BC) are coupled with epigenetic deregulation of gene expression. Epigenetic drugs, aiming to reverse these aberrant transcriptional patterns and sensitize cancer cells to other therapies, provide a new treatment strategy for drug-resistant tumors. Here we investigated the ability of DNA methyltransferase (DNMT) inhibitor decitabine (DAC) to increase the sensitivity of BC cells to anthracycline antibiotic doxorubicin (DOX). Three cell lines representing different molecular BC subtypes, JIMT-1, MDA-MB-231 and T-47D, were used to evaluate the synergy of sequential DAC + DOX treatment in vitro. The cytotoxicity, genotoxicity, apoptosis, and migration capacity were tested in 2D and 3D cultures. Moreover, genome-wide DNA methylation and transcriptomic analyses were employed to understand the differences underlying DAC responsiveness. The ability of DAC to sensitize trastuzumab-resistant HER2-positive JIMT-1 cells to DOX was examined in vivo in an orthotopic xenograft mouse model. DAC and DOX synergistic effect was identified in all tested cell lines, with JIMT-1 cells being most sensitive to DAC. Based on the whole-genome data, we assume that the aggressive behavior of JIMT-1 cells can be related to the enrichment of epithelial-to-mesenchymal transition and stemness-associated pathways in this cell line. The four-week DAC + DOX sequential administration significantly reduced the tumor growth, DNMT1 expression, and global DNA methylation in xenograft tissues. The efficacy of combination therapy was comparable to effect of pegylated liposomal DOX, used exclusively for the treatment of metastatic BC. This work demonstrates the potential of epigenetic drugs to modulate cancer cells' sensitivity to other forms of anticancer therapy.

Chemotherapy-triggered changes in stromal compartment drive tumor invasiveness and progression of breast cancer.

BACKGROUND: Chemotherapy remains a standard treatment option for breast cancer despite its toxic effects to normal tissues. However, the long-lasting effects of chemotherapy on non-malignant cells may influence tumor cell behavior and response to treatment. Here, we have analyzed the effects of doxorubicin (DOX) and paclitaxel (PAC), commonly used chemotherapeutic agents, on the survival and cellular functions of mesenchymal stromal cells (MSC), which comprise an important part of breast tumor microenvironment. METHODS: Chemotherapy-exposed MSC (DOX-MSC, PAC-MSC) were co-cultured with three breast cancer cell (BCC) lines differing in molecular characteristics to study chemotherapy-triggered changes in stromal compartment of the breast tissue and its relevance to tumor progression in vitro and in vivo. Conditioned media from co-cultured cells were used to determine the cytokine content. Mixture of BCC and exposed or unexposed MSC were subcutaneously injected into the immunodeficient SCID/Beige mice to analyze invasion into the surrounding tissue and possible metastases. The same mixtures of cells were applied on the chorioallantoic membrane to study angiogenic potential. RESULTS: Therapy-educated MSC differed in cytokine production compared to un-exposed MSC and influenced proliferation and secretory phenotype of tumor cells in co-culture. Histochemical tumor xenograft analysis revealed increased invasive potential of tumor cells co-injected with DOX-MSC or PAC-MSC and also the presence of nerve fiber infiltration in tumors. Chemotherapy-exposed MSC have also influenced angiogenic potential in the model of chorioallantoic membrane. CONCLUSIONS: Data presented in this study suggest that neoadjuvant chemotherapy could possibly alter otherwise healthy stroma in breast tissue into a hostile tumor-promoting and metastasis favoring niche. Understanding of the tumor microenvironment and its complex net of signals brings us closer to the ability to recognize the mechanisms that prevent failure of standard therapy and accomplish the curative purpose.

The Role of BRCA1/2-Mutated Tumor Microenvironment in Breast Cancer.

Taking into account the factors of high incidence rate, prevalence and mortality, breast cancer represents a crucial social and economic burden. Most cases of breast cancer develop as a consequence of somatic mutations accumulating in mammary epithelial cells throughout lifetime and approximately 5-10% can be ascribed to monogenic predispositions. Even though the role of genetic predispositions in breast cancer is well described in the context of genetics, very little is known about the role of the microenvironment carrying the same aberrant cells impaired by the germline mutation in the breast cancer development and progression. Based on the clinical observations, carcinomas carrying mutations in hereditary tumor-suppressor genes involved in maintaining genome integrity such as BRCA1/2 have worse prognosis and aggressive behavior. One of the mechanisms clarifying the aggressive nature of BRCA-associated tumors implies alterations within the surrounding adipose tissue itself. The objective of this review is to look at the role of BRCA1/2 mutations in the context of breast tumor microenvironment and plausible mechanisms by which it contributes to the aggressive behavior of the tumor cells.

Gamma spectrometric measurements of depth-related radionuclide distribution in walls.

The method for depth-related radionuclide distribution was evolved for approximate determination of the spatial lay-out of radionuclides in materials. The method is based on different attenuation coefficients for various energies of gamma radiation. For each material, the attenuation coefficient decreases with rising energy of radiation. It is therefore possible to assess the location of radionuclides in a material owing to attenuation on the track which a photon has to pass through the material. In this case, gamma lines with energies 609 and 1764 keV produced by nuclide (214)Bi were used for depth-related radionuclide distribution. This application should be suitable for locating radionuclides in the walls of buildings where high dose rates from gamma radiation occur. These doses are caused by natural radionuclides, mainly radium daughters. The presence of radionuclides in houses poses a high risk associated with inhalation of radon and its decay products. For suitable remediation, it is necessary to know the radionuclide depth distribution.