Estrogen promotes the brain metastatic colonization of triple negative breast cancer cells via an astrocyte-mediated paracrine mechanism

Cancer and the metastatic substrate

Seventy percent of cancer patients have detectable metastases when they receive a diagnosis and 90% of cancer deaths result from metastases. These two facts emphasise the urgency for research to study the mechanisms and processes that enable metastasis. We need to develop a greater understanding of the cellular and molecular mechanisms that cause metastasis and also we need to do more. We must also consider the micro- and macro-environmental factors that influence this disease. Studying this environmental context has led us to update the ‘seed and soil’ hypothesis which dates back to the 19th century. This theory describes cancerous cells as seeds and the substrate as the soil in target organs though this may seem antiquated. Nonetheless, the tissue specificity that researchers have recently observed in metastatic colonisation supports the validity of the seed and soil theory. We now know that the metastatic potential of a tumour cell depends on multiple, reciprocal interactions between the primary tumour and distant sites. These interactions determine tumour progression. Studies of metastasis have allowed us to develop treatments that focus on therapeutic effectiveness. These new treatments account for the frequent metastasis of some tumours to target organs such as bones, lungs, brain, and liver. The purpose of this review is first to describe interactions between the cellular and molecular entities and the target organ tumour environment that enables metastasis. A second aim is to describe the complex mechanisms that mediate these interactions.

Stiffness of pancreatic cancer cells is associated with increased invasive potential

Metastasis is a fundamentally physical process in which cells are required to deform through narrow gaps as they invade surrounding tissues and transit to distant sites. In many cancers, more invasive cells are more deformable than less invasive cells, but the extent to which mechanical phenotype, or mechanotype, can predict disease aggressiveness in pancreatic ductal adenocarcinoma (PDAC) remains unclear. Here we investigate the invasive potential and mechanical properties of immortalized PDAC cell lines derived from primary tumors and a secondary metastatic site, as well as noncancerous pancreatic ductal cells. To investigate how invasive behavior is associated with cell mechanotype, we flow cells through micron-scale pores using parallel microfiltration and microfluidic deformability cytometry; these results show that the ability of PDAC cells to passively transit through pores is only weakly correlated with their invasive potential. We also measure the Young's modulus of pancreatic ductal cells using atomic force microscopy, which reveals that there is a strong association between cell stiffness and invasive potential in PDAC cells. To determine the molecular origins of the variability in mechanotype across our PDAC cell lines, we analyze RNAseq data for genes that are known to regulate cell mechanotype. Our results show that vimentin, actin, and lamin A are among the most differentially expressed mechanoregulating genes across our panel of PDAC cell lines, as well as a cohort of 38 additional PDAC cell lines. We confirm levels of these proteins across our cell panel using immunoblotting, and find that levels of lamin A increase with both invasive potential and Young's modulus. Taken together, we find that stiffer PDAC cells are more invasive than more compliant cells, which challenges the paradigm that decreased cell stiffness is a hallmark of metastatic potential.

MicroRNA-588 suppresses tumor cell migration and invasion by targeting GRN in lung squamous cell carcinoma

MicroRNAs (miRNAs) have been demonstrated to be critical in regulating tumor development and progression. The present study investigated the expression of miR-588 using reverse transcription-quantitative polymerase chain reaction analysis in 85 cases of lung squamous cell carcinoma (SCC), and observed the correlation between the expression of miR-588 with clinical pathologic features. The results indicated that the expression of miR-588 was predominantly lower in the tumor samples, compared with non-tumorous samples, and was negatively associated with tumor stages and lymph node invasion. The present study also examined the significance of the expression of miR-588 in SCC using gain- and loss-of-function analyses. It was found that miR-588 inhibited tumor cell migration and invasion. In addition, it was revealed that the overexpression of miR-588 in SCC cells reduced the mRNA and protein levels of progranulin (GRN), whereas miR-588 silencing increased the expression of GRN. A luciferase activity assay showed that miR-588 was able to directly bind to the 3′untranslated region of GRN and regulate its expression. Furthermore, it was found that the expression of GRN was inversely correlated with the expression of miR-588 in 85 paired SCC samples. These results indicated that GRN was involved in the miR-588-mediated suppressive functions in the progression of SCC.

Characterisation of the triple negative breast cancer phenotype associated with the development of central nervous system metastases

Aims

Breast cancer (BC) is the most frequent tumour in women, representing 20–30% of all malignancies, and continues to be the leading cause of cancer deaths among European women. Triple-negative (TN) BC biological aggressiveness is associated with a higher dissemination rate, with central nervous system (CNS) metastases common. This study aims to elucidate the association between gene expression profiles of PTGS2, HBEGF and ST6GALNAC5 and the development of CNS metastases in TNBC.

Methods

This is a case-controlled retrospective study comparing patients (pts) with CNS metastases versus patients without them after adjuvant treatment. The selection of the samples was performed including 30 samples in both case and control groups. Formalin-fixed, paraffin-embedded samples were retrieved from the Hospital 12 de Octubre Biobank. Five 10 µm sections from each FFPE sample were deparaffinised with xylene and washed with ethanol, and the RNA was then extracted with the RecoverAll Kit (Ambion). Gene expression was assessed using TaqMan assays.

Results

A total of 53 patients were included in the study. The average age was 55 years (range 25–85). About 47 patients (88.67%) had ductal histology and presented high grade (III) tumours (40 patients; 75.47%). Eight women in the case group presented first distant recurrence in the CNS (34.80%), local recurrence (three patients, 13.04%), lungs (two patients; 8.7%), bone (one patient; 4.34%) and other locations (seven patients; 30.38%). In the control group, first distant recurrence occurred locally (six patients; 46.1%), in bone (two patients; 15.4%), lungs (one patient; 7.7%) and other sites (four patients; 23.1%). RNA was successfully obtained from 53 out of 60 samples. PTGS2, HBEGF, and ST6GALNAC5 expression values were not related to metastasis location.

Conclusion

TN tumours frequently metastasise to the visceral organs, particularly lungs and brain, and are less common in bone. The literature suggests that expression of the three genes of interest (PTGS2, HBEGF, and ST6GALNAC5) could be different in TNBC patients with CNS metastasis when compared to patients without it. We did not find a differential expression pattern in PTGS2, HBEGF, and ST6GALNAC5 genes in primary TNBC showing CNS metastases. Further studies are needed to clarify the role of these genes in CNS metastases in TNBC patients.

Targeting metastasis

Tumour metastasis, the movement of tumour cells from a primary site to progressively colonize distant organs, is a major contributor to the deaths of cancer patients. Therapeutic goals are the prevention of an initial metastasis in high-risk patients, shrinkage of established lesions and prevention of additional metastases in patients with limited disease. Instead of being autonomous, tumour cells engage in bidirectional interactions with metastatic microenvironments to alter antitumour immunity, the extracellular milieu, genomic stability, survival signalling, chemotherapeutic resistance and proliferative cycles. Can targeting of these interactions significantly improve patient outcomes? In this Review preclinical research, combination therapies and clinical trial designs are re-examined.