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Bone metastasis is an incurable complication of breast cancer. In advanced stages, patients with estrogen-positive tumors experience a significantly higher incidence of bone metastasis (>87%) compared to estrogen-negative patients (<56%). To understand the mechanism of this bone-tropism of ER + tumor, and to identify liquid biopsy biomarkers for patients with high risk of bone metastasis, the secreted extracellular vesicles and cytokines from bone-tropic breast cancer cells are examined in this study. Both exosomal miR-19a and Integrin-Binding Sialoprotein (IBSP) are found to be significantly upregulated and secreted from bone-tropic ER + breast cancer cells, increasing their levels in the circulation of patients. IBSP is found to attract osteoclast cells and create an osteoclast-enriched environment in the bone, assisting the delivery of exosomal miR-19a to osteoclast to induce osteoclastogenesis. Our findings reveal a mechanism by which ER + breast cancer cells create a microenvironment favorable for colonization in the bone. These two secreted factors can also serve as effective biomarkers for ER + breast cancer to predict their risks of bone metastasis. Furthermore, our screening of a natural compound library identifies chlorogenic acid as a potent inhibitor for IBSP-receptor binding to suppress bone metastasis of ER + tumor, suggesting its preventive use for bone recurrence in ER + patients. Bone metastasis is a major complication of breast cancer (BC) and ER + tumors have a higher incidence of bone metastasis than ER − tumors. Here, the authors report that miR‐19a in exosomes and the bone matrix protein, IBSP, are upregulated and secreted by bone tropic ER + BC cells, where they cooperatively induce osteoclastogenesis and promote bone colonization.

Smoking has a profound impact on tumor immunity, and nicotine, which is the major addictive component of smoke, is known to promote tumor progression despite being a non-carcinogen. In this study, we demonstrate that chronic exposure of nicotine plays a critical role in the formation of pre-metastatic niche within the lungs by recruiting pro-tumor N2-neutrophils. This pre-metastatic niche promotes the release of STAT3-activated lipocalin 2 (LCN2), a secretory glycoprotein from the N2-neutrophils, and induces mesenchymal-epithelial transition of tumor cells thereby facilitating colonization and metastatic outgrowth. Elevated levels of serum and urine LCN2 is elevated in early-stage breast cancer patients and cancer-free females with smoking history, suggesting that LCN2 serve as a promising prognostic biomarker for predicting increased risk of metastatic disease in female smoker(s). Moreover, natural compound, salidroside effectively abrogates nicotine-induced neutrophil polarization and consequently reduced lung metastasis of hormone receptor-negative breast cancer cells. Our findings suggest a pro-metastatic role of nicotine-induced N2-neutrophils for cancer cell colonization in the lungs and illuminate the therapeutic use of salidroside to enhance the anti-tumor activity of neutrophils in breast cancer patients.

Mechanisms for breast cancer metastasis remain unclear. Whether truncated glioma-associated oncogene homolog 1 (TGLI1), a transcription factor known to promote angiogenesis, migration and invasion, plays any role in metastasis of any tumor type has never been investigated. In this study, results of two mouse models of breast cancer metastasis showed that ectopic expression of TGLI1, but not GLI1, promoted preferential metastasis to the brain. Conversely, selective TGLI1 knockdown using antisense oligonucleotides led to decreased breast cancer brain metastasis (BCBM) in vivo. Immunohistochemical staining showed that TGLI1, but not GLI1, was increased in lymph node metastases compared to matched primary tumors, and that TGLI1 was expressed at higher levels in BCBM specimens compared to primary tumors. TGLI1 activation is associated with a shortened time to develop BCBM and enriched in HER2-enriched and triple-negative breast cancers. Radioresistant BCBM cell lines and specimens expressed higher levels of TGLI1, but not GLI1, than radiosensitive counterparts. Since cancer stem cells (CSCs) are radioresistant and metastasis-initiating cells, we examined TGLI1 for its involvement in breast CSCs and found TGLI1 to transcriptionally activate stemness genes CD44, Nanog, Sox2, and OCT4 leading to CSC renewal, and TGLI1 outcompetes with GLI1 for binding to target promoters. We next examined whether astrocyte-priming underlies TGLI1-mediated brain tropism and found that TGLI1-positive CSCs strongly activated and interacted with astrocytes in vitro and in vivo. These findings demonstrate, for the first time, that TGLI1 mediates breast cancer metastasis to the brain, in part, through promoting metastasis-initiating CSCs and activating astrocytes in BCBM microenvironment.

Cancer stem-like cells (CSCs) are associated with cancer progression, metastasis, and recurrence, and may also represent a subset of circulating tumor cells (CTCs). In our prior study, CTCs in advanced prostate cancer patients were found to express CD117/c-kit in a liquid biopsy. Whether CD117 expression played an active or passive role in the aggressiveness and migration of these CTCs remained an open question. In this study, we show that CD117 expression in prostate cancer patients is associated with decreased overall and progression-free survival and that activation and phosphorylation of CD117 increases in prostate cancer patients with higher Gleason grades. To determine how CD117 expression and activation by its ligand stem cell factor (SCF, kit ligand, steel factor) alter prostate cancer aggressiveness, we used C4-2 and PC3-mm human prostate cancer cells, which contain a CD117+ subpopulation. We demonstrate that CD117+ cells display increased proliferation and migration. In prostaspheres, CD117 expression enhances sphere formation. In both 2D and 3D cultures, stemness marker gene expression is higher in CD117+ cells. Using xenograft limiting dilution assays and serial tumor initiation assays, we show that CD117+ cells represent a CSC population. Combined, these data indicate that CD117 expression potentially promotes tumor initiation and metastasis. Further, in cell lines, CD117 activation by SCF promotes faster proliferation and invasiveness, while blocking CD117 activation with tyrosine kinase inhibitors (TKIs) decreased progression in a context-dependent manner. We demonstrate that CD117 expression and activation drives prostate cancer aggressiveness through the CSC phenotype and TKI resistance.

Breast cancer displays disparities in mortality between African Americans and Caucasian Americans. However, the exact molecular mechanisms remain elusive. Here, we identify miR-1304-3p as the most upregulated microRNA in African American patients. Importantly, its expression significantly correlates with poor progression-free survival in African American patients. Ectopic expression of miR-1304 promotes tumor progression in vivo. Exosomal miR-1304-3p activates cancer-associated adipocytes that release lipids and enhance cancer cell growth. Moreover, we identify the anti-adipogenic gene GATA2 as the target of miR-1304-3p. Notably, a single nucleotide polymorphism (SNP) located in the miR-1304 stem-loop region shows a significant difference in frequencies of the G allele between African and Caucasian American groups, which promotes the maturation of miR-1304-3p. Therefore, our results reveal a mechanism of the disparity in breast cancer progression and suggest a potential utility of miR-1304-3p and the associated SNP as biomarkers for predicting the outcome of African American patients. The molecular mechanisms explaining racial disparity in breast cancer mortality are not completely elucidated. Here, the authors show that an African-associated SNP in American breast cancer patients, leads to higher levels of microRNA miR-1304-3p which promotes cancer by increasing lipids availability.

The tumor suppressor p53 negatively regulates a number of genes, including the proto-oncogene c-Myc, in addition to activating many other genes. One mechanism of the p53-mediated c-Myc repression may involve transcriptional regulation. However, it is not clear whether microRNAs (miRNAs) play a role in the p53-mediated posttranscriptional regulation of c-Myc. In this study, we show that a putative tumor suppressor, miR-145, is expressed through the phosphoinositide-3 kinase (PI-3K)/Akt and p53 pathways. Importantly, p53 transcriptionally induces the expression of miR-145 by interacting with a potential p53 response element (p53RE) in the miR-145 promoter. We further show that c-Myc is a direct target for miR-145. Although miR-145 silences the expression of c-Myc, anti-miR-145 enhances its expression. This specific silencing of c-Myc by miR-145 accounts at least in part for the miR-145-mediated inhibition of tumor cell growth both in vitro and in vivo. Finally, the blockade of miR-145 by anti-miR-145 is able to reverse the p53-mediated c-Myc repression. Together, these results define the role of miR-145 in the posttranscriptional regulation of c-Myc by p53 and suggest that, as a new member of the p53 regulatory network, miR-145 provides a direct link between p53 and c-Myc in this gene regulatory network.

Obesity is a known risk factor for many cancers, yet recent studies reveal a paradoxical association between low body mass index (BMI) and increased brain metastasis in lung cancer—referred to as the “obesity paradox,” with unclear molecular mechanism(s). Here, we show a significantly higher incidence of brain metastasis in low-BMI lung cancer patients compared to those with high-BMI or other cancer brain metastasis in a pan-analysis of 7628 patients. Mechanistically, low BMI activates ghrelin-GHSR signaling, increasing neuronal neuropeptide Y (NPY) secretion, which promotes tumor metabolic reprogramming via NPY-Y5R, facilitating brain colonization. Elevated plasma ghrelin levels in cancer-free low-BMI subjects suggest its potential as a prognostic biomarker for predicting brain metastasis. Notably, targeting NPY-Y5R or reversing low BMI effectively suppresses brain metastasis, supporting its pro-metastatic role. These findings provide a strong rationale for developing targeted interventions to treat or prevent brain metastasis in lung cancer patients with low BMI. Low body mass index (BMI) is associated with increased brain metastasis risk in lung cancer patients. Here, the authors report that low-BMI increases neuronal secretion of neuropeptide Y (NPY), thereby activating the NPY receptor on lung tumor cells, leading to tumor metabolic reprogramming and brain metastasis.

Background Identifying treatments for triple-negative breast cancer (TNBC) remains a critical medical need. We have found that Interleukin 13 receptor alpha 2 (IL-13RA2), EphA2, EphA3 and EphB2 receptors are over-expressed collectively in majority of patients with breast cancer and its brain metastases. We are pursuing the novel idea of targeting these four tumor-associated receptors identified by us with one pharmaceutical compound. A compound, called QUAD, was designed and constructed, which binds all four targeted receptors. Methods We have examined the presence of IL-13RA2, EphA2, EphA3 and EphB2 receptors in breast cancer cells in vitro, tissue micro-arrays including involved lymph nodes, and in paired primary tumor—brain metastases, including two subtypes of breast cancer. We also tested the activity of the quadrivalent ligand, QUAD, conjugated to a derivative of maytansine, DM1, in vitro and in vivo. Results We have found that the four target receptors are frequently over-expressed in breast cancer, including TNBC and (HER2)-positive breast cancers and related metastases to the brain. This is based on the observed expression levels for the genes and the gene products; a combined expression of our target of interest approaches 100% of specimens’ positivity. Furthermore, several TNBC cell lines were killed at low concentrations of QUAD-DM1 conjugate. MDA-MB-231 tumors growing in mammary pads of athymic mice responded significantly to a dose of 12 mg/kg (3x). MDA-MB-231-BrM tumors growing intracranially also responded to 4 µg/mouse (1x) of QUAD-DM1. Conclusions QUAD-DM1 is a novel multivalent drug conjugate that appears to be highly suitable for the treatment of breast cancer and related brain metastases. The drug candidate can be administered systemically, due to its favorable toxicity profile, or loco-regionally.