Breast Cancer-Secreted Factors Promote Lung Metastasis by Signaling Systemically to Induce a Fibrotic Premetastatic Niche.

Metastatic cancer is largely incurable and is the main cause of cancer-related deaths. The metastatic microenvironment facilitates formation of metastases. Cancer-associated fibroblasts (CAF) are crucial players in generating a hospitable metastatic niche by mediating an inflammatory microenvironment. Fibroblasts also play a central role in modifying the architecture and stiffness of the extracellular matrix (ECM). Resolving the early changes in the metastatic niche could help identify approaches to inhibit metastatic progression. Here, we demonstrate in mouse models of spontaneous breast cancer pulmonary metastasis that fibrotic changes and rewiring of lung fibroblasts occurred at premetastatic stages, suggesting systemic influence by the primary tumor. Activin A (ActA), a TGFß superfamily member, was secreted from breast tumors and its levels in the blood were highly elevated in tumor-bearing mice. ActA upregulated the expression of profibrotic factors in lung fibroblasts, leading to enhanced collagen deposition in the lung premetastatic niche. ActA signaling was functionally important for lung metastasis, as genetic targeting of ActA in breast cancer cells significantly attenuated lung metastasis and improved survival. Moreover, high levels of ActA in human patients with breast cancer were associated with lung metastatic relapse and poor survival. This study uncovers a novel mechanism by which breast cancer cells systemically rewire the stromal microenvironment in the metastatic niche to facilitate pulmonary metastasis. SIGNIFICANCE: ActA mediates cross-talk between breast cancer cells and cancer-associated fibroblasts in the lung metastatic niche that enhances fibrosis and metastasis, implicating ActA as a potential therapeutic target to inhibit metastatic relapse.

ΔNp63 overexpression promotes oral cancer cell migration through hyperactivated Activin A signaling.

Oral cancer is a common malignant tumor of the oral cavity that affects many countries with a prevalent distribution in the Indian subcontinent, with poor prognosis rate on account of locoregional metastases. Gain-of-function mutations in p53 and overexpression of its related transcription factor, p63 are both widely reported events in oral cancers. However, targeting these alterations remains a far-achieved aim due to lack of knowledge on their downstream signaling pathways. In the present study, we characterize the isoforms of p63 and using knockdown strategy, decipher the functions and oncogenic signaling of p63 in oral cancers. Using Microarray and Chromatin Immunoprecipitation experiments, we decipher a novel transcriptional regulatory axis between p63 and Activin A and establish its functional significance in migration of oral cancer cells. Using an orally bioavailable inhibitor of the Activin A pathway to attenuate oral cancer cell migration and invasion, we further demonstrate the targetability of this signaling axis. Our study highlights the oncogenic role of ΔNp63 - Activin A - SMAD2/3 signaling and provides a basis for targeting this oncogenic pathway in oral cancers.

Reciprocal interactions between innate immune cells and astrocytes facilitate neuroinflammation and brain metastasis via lipocalin-2.

Brain metastasis still encompass very grim prognosis and therefore understanding the underlying mechanisms is an urgent need toward developing better therapeutic strategies. We uncover the intricate interactions between recruited innate immune cells and resident astrocytes in the brain metastatic niche that facilitate metastasis of melanoma and breast cancer. We show that granulocyte-derived lipocalin-2 (LCN2) induces inflammatory activation of astrocytes, leading to myeloid cell recruitment to the brain. LCN2 is central to inducing neuroinflammation as its genetic targeting or bone-marrow transplantation from LCN2-/- mice was sufficient to attenuate neuroinflammation and inhibit brain metastasis. Moreover, high LCN2 levels in patient blood and brain metastases in multiple cancer types were strongly associated with disease progression and poor survival. Our findings uncover a previously unknown mechanism, establishing a central role for the reciprocal interactions between granulocytes and astrocytes in promoting brain metastasis and implicate LCN2 as a prognostic marker and potential therapeutic target.

Concomitant overexpression of Activin A and p63 is associated with poor outcome in oral cancer patients.

BACKGROUND: The present study aims to comprehensively analyze expression of Activin signaling components in oral cancer and to determine the predominant Activin expressed and its influence on prognosis. As our preliminary studies indicated regulation of Activin gene by p63, we also propose to assess its correlation with p63/p53 in oral tumors and its impact on outcome. METHODS: Expression of Activin subunits, receptors, and regulators was assessed by qRT-PCR and Western blotting. Correlation between Activin A and p63/p53 expression was evaluated in oral tumors by immunohistochemistry and their association with clinical outcome was determined by Kaplan-Meier curves and Cox regression. RESULTS: Activin ßA transcripts were upregulated (P = .013) in oral dysplastic and cancer cells compared with normal oral mucosa. Expression of Activin receptors and regulators was also altered. Activin ßA protein was significantly upregulated in oral tumors and adjacent normal tissues compared with normal oral mucosa (P < .0001). Expression of Activin ßA and p63 significantly correlated in oral tumors, correlation being stronger in tumors with high p53 (r = -.394, P = .005). Activin ßA overexpression was associated with advanced tumor stage (P = .021), positive nodes (P = .045), poor recurrence-free survival (P = .013), and overall survival (P = .024), while its concomitant overexpression with p63 was a better predictor of recurrence-free survival (HR = 10.66, CI: 1.41-80.19). CONCLUSIONS: Activin A overexpression is an early event in oral cancer pathogenesis and can independently predict survival. Moreover, in combination with p63 overexpression, it served as a better marker for poor prognosis. Activin A could thus be a promising target for improved outcome in oral cancer patients.