Breast cancer (BC) is a highly heterogeneous disease. The treatment of BC is complicated owing to intratumoral complexity. Tissue biopsy and immunohistochemistry are the current gold standard techniques to guide breast cancer therapy; however, these techniques do not assess tumoral molecular heterogeneity. Personalized medicine aims to overcome these biological and clinical complexities. Advances in techniques and computational analyses have enabled increasingly sensitive, specific, and accurate application of liquid biopsy. Such progress has ushered in a new era in precision medicine, where the objective is personalized treatment of breast cancer, early screening, accurate diagnosis and prognosis, relapse detection, longitudinal monitoring, and drug selection. Liquid biopsy can be defined as the sampling of components of tumor cells that are released from a tumor and/or metastatic deposits into the blood, urine, feces, saliva, and other biological substances. Such components include circulating tumor cells (CTCs), circulating tumor DNA (ctDNA) or circulating tumor RNA (ctRNA), platelets, and exosomes. This review aims to highlight the role of liquid biopsy in breast cancer and precision medicine.

Neoadjuvant chemotherapy (NAC) is often used to treat locally advanced disease for tumor downstaging, thus improving the chances of breast-conserving surgery. From the NAC response, it is possible to obtain prognostic information as patients may reach a pathological complete response (pCR). Those who do might have significant advantages in terms of survival rates. Breast cancer (BC) is a heterogeneous disease that requires personalized treatment strategies. The development of targeted therapies depends on identifying biomarkers that can be used to assess treatment efficacy as well as the discovery of new and more accurate therapeutic agents. With the development of new “OMICS” technologies, i.e., genomics, transcriptomics, and proteomics, among others, the discovery of new biomarkers is increasingly being used in the context of clinical practice, bringing us closer to personalized management of BC treatment. The aim of this review is to compile the main biomarkers that predict pCR in BC after NAC.

Breast cancer is a leading cause of central nervous system (CNS) metastases in women, often associated with poor prognosis and limited therapeutic options. However, molecular differences between primary tumors and CNS metastases remain underexplored. We aimed to characterize transcriptomic differences between primary breast tumors and matched CNS metastases and identify immune-related biomarkers associated with metastatic progression and patient outcomes. Transcriptomic profiling was based on 11 matched FFPE sample pairs (primary tumor and CNS metastasis). Paired formalin-fixed paraffin-embedded (FFPE) samples from primary tumors (T1) and CNS metastases (T2) were analyzed using the NanoString nCounter^® platform and the PanCancer IO 360™ Gene Expression Panel. Differential gene expression, Z-score transformation, and heatmap visualization were performed in R. In silico survival analyses for overall survival (OS) and recurrence-free survival (RFS) were conducted using publicly available TCGA and GEO datasets. Forty-five genes were significantly differentially expressed between the T1 and T2 samples. Immune-related genes such as CXCL9, IL7R, CD79A, and CTSW showed consistent downregulation in CNS metastases. High expression of CXCL9 and CD79A was associated with improved OS and RFS, whereas high IL7R and CTSW expression correlated with worse outcomes. These findings indicate immune suppression as a hallmark of CNS colonization. Comparative transcriptomic analysis further underscored the distinct molecular landscapes between primary and metastatic tumors. This study highlights transcriptional signatures associated with breast cancer CNS metastases, emphasizing the role of immune modulation in metastatic progression. The identified genes have potential as prognostic biomarkers and therapeutic targets, supporting the need for site-specific molecular profiling in metastatic breast cancer management.

Toll-like receptors (TLRs) are essential type I transmembrane glycoproteins that play a major role in inflammation and innate immune system. TLRs have been investigated in cancer research due to their dual role in tumor progression. The TLRs signaling pathways can promote survival, cell proliferation and apoptosis and its stimulation may either enhance or inhibit tumor growth and metastasis. The role of TLR4 in cancer biology has been studied but the direct relation between TLR4 and development of many cancer types, including breast cancer, is still obscure. Thus, more studies about TLR4 expression in breast cancer can help to better understanding the involvement of TLR4 in this disease. The aim of this study was to investigate the expression of TLR4 in a rat mammary carcinogenesis model. At 51 days of age, female Sprague-Dawley rats were allocated into three groups: Groups 1 and 2 (n = 12 each) were initiated for mammary carcinogenesis by a single i.g. dose of 7,12-dimethylbenz[a]anthracene (DMBA) (80mg/kg) and Group 3 (n = 6) received a single i.g. dose of sesame oil (DMBA vehicle, 1 ml/kg). Also, group 2 received five s.c. injections per week of Tamoxifen (100 μg/kg) and groups 1 and 2 received similar injections of sesame oil (Tamoxifen vehicle, 0.5 ml/kg) during 12 weeks. At week 13, the animals were euthanized and mammary tumor (groups 1 and 2) and non-altered mammary glands (group 3) were collected and processed for histophatological analysis and TLR4 expression by immunohistochemistry. The TLR4 expression was classified as weak, moderate or strong and the incidence of intensity scores in tumor samples/group was analyzed by Fisher's exact test. Significant differences when p<0.05. Most of mammary tumors were classified as adenocarcinomas with tubular, papillary, cribriform or mixed patterns. Also, the tumors presented an expansive growth pattern with local invasive areas but without metastasis. Besides, a tumor inflammatory response was more intensively observed in G2. The immunoreactivity for TLR4 was significantly stronger in non-altered alveolar and ductal epithelial cells (G1) than in mammary tumor epithelial cells (groups 1 and 2) (p< 0.001 and p = 0.007, respectively). The TLR4 immunoreactivity was more intense in mammary tumor epithelial cells from tamoxifen-treated group than in positive control group (G1), but without a significant difference. In the tumor stroma the positivity for TLR4 was observed mainly in mononuclear inflammatory cells, showing a strong positivity for this marker in groups G1 and G2 when compared to the stromal cells from non-altered mammary tissue (G1, p = 0.028, p< 0,001). This present study show that there is a significant reduction in TLR4 expression in tumor epithelial cells when compared to the normal compartment in this rat DMBA-induced mammary carcinogenesis model. Besides, the intensity of the inflammatory response in the tumor microenvironment can alter the immunoreactivity for TLR4. Citation Format: Joyce Regina Zapaterini, Muriele Bertagna Varuzza, Nelci Antunes Moura, Maria Aparecida Marchesan Rodrigues, Luis Fernando Barbisan. Toll-like receptor 4 immunoreactivity in mammary tumors chemically induced in female Sprague-Dawley rats. []. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl): nr 2720. doi:10.1158/1538-7445.AM2015-2720