The tumor microenvironment plays a pivotal role in the tumorigenesis, progression, and metastatic spread of many cancers including breast. There is now increasing evidence to support the observations that a bidirectional interplay between breast cancer cells and stromal cells exists within the tumor and the tumor microenvironment both at the primary tumor site and at the metastatic site. This interaction occurs through direct cell to cell contact, or by the release of autocrine or paracrine factors which can activate pro-tumor signaling pathways and modulate tumor behavior. In this review, we will highlight recent advances in our current knowledge about the multiple interactions between breast cancer cells and neighboring cells (fibroblasts, endothelial cells, adipocytes, innate and adaptive immune cells) in the tumor microenvironment that coordinate to regulate metastasis. We also highlight the role of exosomes and circulating tumor cells in facilitating breast cancer metastasis. We discuss some key markers associated with stromal cells in the breast tumor environment and their potential to predict patient survival and guide treatment. Finally, we will provide some brief perspectives on how current technologies may lead to the development of more effective therapies for the clinical management of breast cancer patients.

The prolactin inducible protein (PIP) is expressed to varying degrees in more than 90% of breast cancers (BCs). Although high levels of PIP expression in BC has been shown to correlate with better prognosis and patient response to chemotherapy, some studies suggest that PIP may also play a role in metastasis. Here, we investigated the role of PIP in BC using the well-established 4T1 and E0771 mouse BC cell lines. Stable expression of PIP in both cell lines did not significantly alter their proliferation, migration, and response to anticancer drugs in vitro compared to empty vector control. To assess the effect of PIP expression on breast tumorigenesis in vivo, the 4T1 syngeneic transplantable mouse model was utilized. In immunocompetent syngeneic BALB/c mice, PIP-expressing 4T1 primary tumors displayed delayed tumor onset and reduced tumor growth, and this was associated with higher percentages of natural killer cells and reduced percentages of type 2 T-helper cells in the tumor environment. The delayed tumor onset and growth were abrogated in immunodeficient mice, suggesting that PIP-mediated modulation of primary tumor growth involves an intact immune system. Paradoxically, we also observed that PIP expression was associated with a higher number of 4T1 colonies in the lungs in both the immunocompetent and immunodeficient mice. Gene expression analysis of PIP-expressing 4T1 cells (4T1-PIP) revealed that genes associated with tumor metastasis such as CCL7, MMP3 and MMP13, were significantly upregulated in 4T1-PIP cells when compared to the empty vector control (4T1-EV) cells. Collectively, these studies strongly suggest that PIP may possess a double-edge sword effect in BC, enhancing both antitumor immunity as well as metastasis.

A taxa de mortalidade (TM) representa um dos principais indicadores da qualidade da assistência a pessoa com câncer de mama (CM), mostrando-se como um instrumento fundamental no delineamento e revisão das políticas voltadas à pessoa acometida pela doença. A abordagem terapêutica, por sua vez, representa um dos eixos primordiais à redução da mortalidade pela doença. Assim, o objetivo deste estudo é caracterizar o perfil da mortalidade por CM no Brasil, bem como propor uma nova alternativa terapêutica, baseada no uso de produtos naturais. Para isso, realizou-se um estudo documental-retrospectivo, descrevendo a distribuição da TM por CM no Brasil, durante o período de 1987 a 2016, considerando fatores como sexo e faixa etária; em consonância, também foi realizado um estudo experimental, de caráter quanti-qualitativo, para avaliar o potencial citotóxico da (S)-(+) carvona e da (R)-(-)-carvona em linhagens celulares de CM. Assim, constatou-se que a TM por CM no Brasil apresenta uma tendência crescente ao longo dos anos, independe de sexo e faixa etária. No entanto, observou-se que no sexo feminino houve um maior número de mortes e, no sexo masculino, uma maior progressão da TM ao longo dos anos. Ademais, a amplificação da mortalidade por CM ocorreu em conformidade com o aumento da idade, revelando uma relação de proporcionalidade entre esses dois fatores. Com relação à análise experimental, constatou-se que tanto a (S)-(+) carvona como a (R)-(-)-carvona revelaram-se citotóxicas às linhagens celulares de CM, apresentando um efeito dependente da concentração.

Prolactin-inducible protein (PIP) is a multifunctional glycoprotein that is highly expressed and found in the secretions of apocrine glands, such as salivary, lacrimal, and sweat glands including the mammary glands. PIP has been implicated in various diseases, including breast cancer, gross cystic disease of the breast, keratoconus of the eye and the autoimmune Sjögren’s syndrome. Here we have generated a <i>Pip</i> knockout (KO) mouse using the CRISPR/Cas9 system. The Cas9 protein and two single guide RNAs targeting specific regions for both exons 1 and 2 of the <i>Pip</i> gene were microinjected into mouse embryos. The deletions and insertions promoted by CRISPR/Cas9 system on the <i>Pip</i> gene successfully disrupted PIP protein coding, as confirmed by PCR genotyping, sequencing and ultimately Western blot analysis. This mouse model was generated in the inbred C57Bl/6J mouse, which exhibits lower genetic variation. This novel CRISPR <i>Pip</i> KO mouse model will be not only be useful for future studies to interrogate the multifunctional role of PIP in physiological processes but will facilitate a broader understanding of the function of PIP <i>in vivo</i> while providing unprecedented insight into its role in a spectrum of diseases attributed to the deregulation of the <i>PIP</i> gene.

The tight junction membrane protein claudin 1 and the adherens junction protein E-cadherin play critical roles in cell–cell communication and in cell signaling. As a result, their protein levels and distribution in cancer have been a focus of cancer researchers in recent years. The loss of sensitivity to contact inhibition and the establishment of invasive properties in cancer are thought to be a result of the mislocalization of these membrane proteins to the cytoplasm. However, reports on their distribution and levels have been inconsistent. It is therefore critical that the techniques used to determine the cellular localization of these proteins be both consistent and reliable. This study was undertaken to determine the optimal fixation method, methanol or formalin, for the detection of claudin 1 and E-cadherin by immunofluorescence in five different human breast cancer cell lines. Both methods exhibited staining of the cell membrane and cytoplasm, but the strongest and most distinct signals were obtained using methanol fixation. Interestingly, cell-specific differences were also observed that appeared to be associated with levels of claudin 1 and E-cadherin as seen by Western blotting. Therefore, when evaluating cellular localization of the junction proteins claudin 1 and E-cadherin, expression level and cell type differences must be considered: