Development of minimally invasive biomarker assays for early detection and effective clinical management of pancreatic cancer is urgently needed to reduce high morbidity and mortality associated with this malignancy. We hypothesized that if aberrantly expressing microRNAs (miRNA) in pancreatic adenocarcinoma tissues are detected in blood plasma, then plasma profiling of these miRNAs might serve as a minimally invasive early detection biomarker assay for this malignancy. By using a modified protocol to isolate and quantify plasma miRNAs from heparin-treated blood, we show that miRNA profiling in plasma can differentiate pancreatic adenocarcinoma patients from healthy controls. We have profiled four miRNAs, miR-21, miR-210, miR-155, and miR-196a, all implicated in the development of pancreatic cancer with either proven or predicted target genes involved in critical cancerassociated cellular pathways. Of these, miR-155 has recently been identified as a candidate biomarker of early pancreatic neoplasia, whereas elevated expression of miR196a has been shown to parallel progression of disease. The results revealed a sensitivity of 64% and a specificity of 89% with the analyses of plasma levels for this panel of four miRNAs. The area under the receiver operating characteristic curve were estimated at 0.82 and 0.78 without and with leave-one-out cross-validation scheme, respectively. These observations, although a "proof of principle" finding at this time, show the feasibility of developing plasma miRNA profiling as a sensitive and specific blood-based biomarker assay for pancreatic cancer that has the potential of translation to the clinic with additional improvements in the future.

The Hippo/YAP pathway is an emerging signaling cascade involved in the regulation of stem cell activity and organ size. Alterations in Hippo signaling are also a common feature of human epithelial malignancies, although the molecular bases for this misregulation are unclear. As most of the current knowledge has been derived from work in the fruit fly, our understanding of mammalian Hippo/YAP signaling is still incomplete. To identify novel components of this pathway, we performed an RNAi-based kinome screen in human cells. Our screen identified several kinases not previously associated with Hippo signaling that strongly regulate the activity of the Hippo transducer YAP. Some of these kinases control processes such as response to stress, boundary formation, cell cycle and adhesion, and reflect novel inputs that may impinge on Hippo signaling and growth control. One of the hits, LKB1 (also known as Stk11), is a common tumor suppressor whose mechanism of action is only partially understood. We demonstrate that LKB1 acts through its substrates of the PAR-1 family (MARK1-4) to regulate the localization of the baso-lateral polarity complex and the activity of the core Hippo kinases. Murine and human LKB1-deficient tumors exhibit mislocalization of the basolateral determinant Scribble, reduced Hippo kinase activity, and enhanced YAP-driven transcription. Using xenograft assays and genetic analysis, we demonstrate that YAP is functionally important for the tumor suppressive effects of LKB1. Our results identify an important signaling axis that links YAP activation with LKB1 mutations, and have significant implications for the treatment of LKB1-mutant human malignancies. Additionally, our findings provide novel insight into the nature of inputs that speak to the Hippo/YAP signaling cascade.

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KIT gain of function mutations play an important role in the pathogenesis of gastrointestinal stromal tumors (GISTs). Imatinib is a selective tyrosine kinase inhibitor of ABL, platelet-derived growth factor receptor (PDGFR), and KIT and represents a new paradigm of targeted therapy against GISTs. Here we report for the first time that, after imatinib treatment, an additional specific and novel KIT mutation occurs in GISTs as they develop resistance to the drug. We studied 12 GIST patients with initial near-complete response to imatinib. Seven harbored mutations in KIT exon 11, and 5 harbored mutations in exon 9. Within 31 months, six imatinib-resistant rapidly progressive peritoneal implants (metastatic foci) developed in five patients. Quiescent residual GISTs persisted in seven patients. All six rapidly progressive imatinib-resistant implants from five patients show an identical novel KIT missense mutation, 1982T3 C, that resulted in Val654Ala in KIT tyrosine kinase domain 1. This novel mutation has never been reported before, is not present in pre-imatinib or post-imatinib residual quiescent GISTs, and is strongly correlated with imatinib resistance. Allelic-specific sequencing data show that this new mutation occurs in the allele that harbors original activation mutation of KIT.

White adipose tissue (WAT) overgrowth in obesity is linked with increased aggressiveness of certain cancers. Adipose stromal cells (ASCs) can become mobilized from WAT, recruited by tumours and promote cancer progression. Mechanisms underlying ASC trafficking are unclear. Here we demonstrate that chemokines CXCL1 and CXCL8 chemoattract ASC by signalling through their receptors, CXCR1 and CXCR2, in cell culture models. We further show that obese patients with prostate cancer have increased epithelial CXCL1 expression. Concomitantly, we observe that cells with ASC phenotype are mobilized and infiltrate tumours in obese patients. Using mouse models, we show that the CXCL1 chemokine gradient is required for the obesity-dependent tumour ASC recruitment, vascularization and tumour growth promotion. We demonstrate that αSMA expression in ASCs is induced by chemokine signalling and mediates the stimulatory effects of ASCs on endothelial cells. Our data suggest that ASC recruitment to tumours, driven by CXCL1 and CXCL8, promotes prostate cancer progression.