Breast cancer and melanoma cells commonly metastasize to the brain using homing mechanisms that are poorly understood. Cancer patients with brain metastases display poor prognosis and survival due to the lack of effective therapeutics and treatment strategies. Recent work using intravital microscopy and preclinical animal models indicates that metastatic cells colonize the brain, specifically in close contact with the existing brain vasculature. However, it is not known how contact with the vascular niche promotes microtumor formation. Here, we investigate the role of connexins in mediating early events in brain colonization using transparent zebrafish and chicken embryo models of brain metastasis. We provide evidence that breast cancer and melanoma cells utilize connexin gap junction proteins (Cx43, Cx26) to initiate brain metastatic lesion formation in association with the vasculature. RNAi depletion of connexins or pharmacological blocking of connexin-mediated cell-cell communication with carbenoxolone inhibited brain colonization by blocking tumor cell extravasation and blood vessel co-option. Activation of the metastatic gene twist in breast cancer cells increased Cx43 protein expression and gap junction communication, leading to increased extravasation, blood vessel co-option and brain colonization. Conversely, inhibiting twist activity reduced Cx43-mediated gap junction coupling and brain colonization. Database analyses of patient histories revealed increased expression of Cx26 and Cx43 in primary melanoma and breast cancer tumors, respectively, which correlated with increased cancer recurrence and metastasis. Together, our data indicate that Cx43 and Cx26 mediate cancer cell metastasis to the brain and suggest that connexins might be exploited therapeutically to benefit cancer patients with metastatic disease.
Dilated dysfunction involving multiple visceral organs has been reported in patients with systemic lupus erythematosus (SLE). Chronic intestinal pseudo-obstruction (CIPO) resulting from intestinal smooth muscle damage has presented in conjunction with ureterohydronephrosis and, more rarely, biliary dilatation (megacholedochus). While the molecular pathogenesis is largely unknown, observed histopathologic features include widespread myositis, myocyte necrosis in the intestinal muscularis propria with subsequent atrophy and fibrosis, preserved myenteric innervations and little vasculitis. High dose immunosuppression usually results in resolution of symptoms with recovery of smooth muscle function, indicative of an autoimmune etiology. We report a patient with SLE who presented with intestinal pseudo-obstruction, ureterohydronephrosis and megacholedochus, and present images that illustrate megaviscera simultaneously involving all 3 visceral organs. Since the co-manifestation of all 3 is unusual and has been reported only once previously, we have termed this rare clinical syndrome generalized megaviscera of lupus (GML). Although the SLE disease-activity parameters responded to aggressive immunomodulative therapy in our patient, clinical evidence of peristaltic dysfunction persisted in all involved viscera. This is a variation from the favorable outcomes reported previously in SLE patients with GML and we attribute this poor clinical outcome to disease severity and, most importantly, delayed clinical presentation. Since inflammation followed by atrophy and fibrosis are key aspects in the pathogenesis and natural history of GML, the poor response in our patient who presented late in the clinical course may be the result of burnt out inflammation with irreversible end-stage fibrosis. Thus, early recognition and timely initiation of treatment may be the key to recover visceral peristaltic function in patients with GML.
Early biomarkers and effective therapeutic strategies are desperately needed to treat pancreatic ductal adenocarcinoma (PDAC), which has a dismal 5-year patient survival rate. Here, we report that the novel tyrosine kinase PEAK1 is upregulated in human malignancies, including human PDACs and pancreatic intraepithelial neoplasia (PanIN). Oncogenic KRas induced a PEAK1-dependent kinase amplification loop between Src, PEAK1, and ErbB2 to drive PDAC tumor growth and metastasis in vivo. Surprisingly, blockade of ErbB2 expression increased Src-dependent PEAK1 expression, PEAK1-dependent Src activation, and tumor growth in vivo, suggesting a mechanism for the observed resistance of patients with PDACs to therapeutic intervention. Importantly, PEAK1 inactivation sensitized PDAC cells to trastuzumab and gemcitabine therapy. Our findings, therefore, suggest that PEAK1 is a novel biomarker, critical signaling hub, and new therapeutic target in PDACs.
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