No abstract

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.

BackgroundFGF21 is a promising intervention therapy for metabolic diseases as fatty liver, obesity and diabetes. Recent results suggest that FGF21 is highly expressed in hepatocytes under metabolic stress caused by starvation, hepatosteatosis, obesity and diabetes. Hepatic FGF21 elicits metabolic benefits by targeting adipocytes of the peripheral adipose tissue through the transmembrane FGFR1-KLB complex. Ablation of adipose FGFR1 resulted in increased hepatosteatosis under starvation conditions and abrogation of the anti-obesogenic action of FGF21. These results indicate that FGF21 may be a stress responsive hepatokine that targets adipocytes and adipose tissue for alleviating the damaging effects of stress on the liver. However, it is unclear whether hepatic induction of FGF21 is limited to only metabolic stress, or to a more general hepatic stress resulting from liver pathogenesis and injury.MethodsIn this survey-based study, we examine the nature of hepatic FGF21 activation in liver tissues and tissue sections from several mouse liver disease models and human patients, by quantitative PCR, immunohistochemistry, protein chemistry, and reporter and CHIP assays. The liver diseases include genetic and chemical-induced HCC, liver injury and regeneration, cirrhosis, and other types of liver diseases.ResultsWe found that mouse FGF21 is induced in response to chemical (DEN treatment) and genetic-induced hepatocarcinogenesis (disruptions in LKB1, p53, MST1/2, SAV1 and PTEN). It is also induced in response to loss of liver mass due to partial hepatectomy followed by regeneration. The induction of FGF21 expression is potentially under the control of stress responsive transcription factors p53 and STAT3. Serum FGF21 levels correlate with FGF21 expression in hepatocytes. In patients with hepatitis, fatty degeneration, cirrhosis and liver tumors, FGF21 levels in hepatocytes or phenotypically normal hepatocytes are invariably elevated compared to normal health subjects.ConclusionFGF21 is an inducible hepatokine and could be a biomarker for normal hepatocyte function. Activation of its expression is a response of functional hepatocytes to a broad spectrum of pathological changes that impose both cellular and metabolic stress on the liver. Taken together with our recent data, we suggest that hepatic FGF21 is a general stress responsive factor that targets adipose tissue for normalizing local and systemic metabolic parameters while alleviating the overload and damaging effects imposed by the pathogenic stress on the liver. This study therefore provides a rationale for clinical biomarker studies in humans.

ABSTRACTinjected with primary leukemia cells.

Purpose: Peutz-Jeghers syndrome (PJS) is a unique disorder characterized by the development of hamartomas in the gastrointestinal tract as well as increased risks for variety of malignancies. Germ-line mutations of LKB1 cause PJS. We have generated Lkb1 +/-mice, which model human PJS. Rapamycin and its analogues are promising preventive and therapeutic agents that specifically inhibit signaling from mammalian target of rapamycin (mTOR). Hyperactivation of mTOR signaling has been associated with PJS. The objective of the study is to investigate the efficacy of mTOR inhibition in suppressing Peutz-Jeghers polyposis in Lkb1 +/-mice. Experimental Design: We initiated a trial of rapamycin in Lkb1 +/-mice at 9 months of age (after the onset of polyposis) at the dose of 2 mg/kg/d for a 2-month period.We assessed the efficacy of rapamycin by measuring polyp sizes and tumor burden. To examine the effect of rapamycin on mTOR signaling, phosphorylation levels of S6 were evaluated by immunostaining. Results: We observed a significant decrease in mean tumor burden (Student's t test, P = 0.023) as well as total tumor burden in rapamycin-treated group compared with control group. Comparison of the polyp size observed in both rapamycin-treated and control groups showed that rapamycin efficiently decreased the tumor burden of large polyps (>8 mm). This inhibition of rapamycin was associated with a decrease in phosphorylated S6 levels in the polyps. Conclusions: Rapamycin effectively suppresses Peutz-Jeghers polyposis in a mouse model, suggesting that rapamycin or its analogues may represent a new targeted therapy for the treatment of PJS.

BACKGROUNDIntratumoral heterogeneity presents a major obstacle to the widespread implementation of precision medicine. The authors assessed the origin of intratumoral heterogeneity in nonseminomatous germ cell tumor of the testis (NSGCT) and identified distinct tumor subtypes and a potentially lethal phenotype.METHODSIn this retrospective study, all consecutive patients who had been diagnosed with an NSGCT between January 2000 and December 2010 were evaluated. The histologic makeup of primary tumors and the clinical course of disease were determined for each patient. A Fine and Gray proportional hazards regression analysis was used to determine the prognostic risk factors, and the Gray test was used to detect differences in the cumulative incidence of cancer death. In a separate prospective study, next‐generation sequencing was performed on tumor samples from 9 patients to identify any actionable mutations.RESULTSSix hundred fifteen patients were included in this study. Multivariate analysis revealed that the presence of yolk sac tumor in the primary tumor (P = .0003) was associated with an unfavorable prognosis. NSGCT could be divided into 5 subgroups. Patients in the yolk sac‐seminoma subgroup had the poorest clinical outcome (P = .0015). These tumors tended to undergo somatic transformation (P < .0001). Among the 9 NSGCTs that had a yolk sac tumor phenotype, no consistent gene mutation was detected.CONCLUSIONSThe current data suggest that intratumoral heterogeneity is caused in part by differentiation of pluripotent progenitor cells. Integrated or multimodal therapy may be effective at addressing intratumoral heterogeneity and treating distinct subtypes as well as a potentially lethal phenotype of NSGCT. Cancer 2016;122:1836–43. © 2016 The Authors. Cancer published by Wiley Periodicals, Inc. on behalf of American Cancer Society. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

The spectrum of cancers seen in a hospital based Lynch syndrome registry of mismatch repair gene mutation carriers was examined to determine the distribution of cancers and examine excess cancer risk. Overall there were 504 cancers recorded in 368 mutation carriers from 176 families. These included 236 (46.8 %) colorectal and 268 (53.2 %) extracolonic cancers. MLH1 mutation carriers had a higher frequency of colorectal cancers whereas MSH2, MSH6 and PMS2 mutation carriers had more extracolonic cancers although these differences were not statistically significant. Men had fewer extracolonic cancers than colorectal (45.3 vs. 54.7 %), whereas women had more extracolonic than colorectal cancers (59.0 vs. 41.0 %). The mean age at diagnosis overall for extracolonic cancers was older than for colorectal, 49.1 versus 44.8 years (P ≤ 0.001). As expected, the index cancer was colorectal in 58.1 % of patients and among the extracolonic index cancers, endometrial was the most common (13.8 %). A significant number of non-Lynch syndrome index cancers were recorded including breast (n = 5) prostate (n = 3), thyroid (n = 3), cervix (n = 3), melanoma (n = 3), and 1 case each of thymoma, sinus cavity, and adenocarcinoma of the lung. However, standardized incidence ratios calculated to assess excess cancer risk showed that only those cancers known to be associated with Lynch syndrome were significant in our sample. We found that Lynch syndrome patients can often present with cancers that are not considered part of Lynch syndrome. This has clinical relevance both for diagnosis of Lynch syndrome and surveillance for cancers of different sites during follow-up of these patients.

Background Genome-wide association studies of European and East Asian populations have identified lung cancer susceptibility loci on chromosomes 5p15.33, 6p22.1-p21.31 and 15q25.1. We investigated whether these regions contain lung cancer susceptibly loci in African-Americans refined previous association signals by utilizing the reduced linkage disequilibrium observed in African-Americans. Methods 1308 African-American cases and 1241 African-American controls from three centers were genotyped for 760 single nucleotide polymorphisms spanning three regions, and additional SNP imputation was performed. Associations between polymorphisms and lung cancer risk were estimated using logistic regression, stratified by tumor histology where appropriate. Results The strongest associations were observed on 15q25.1 in/near CHRNA5, including a missense substitution (rs16969968: OR = 1.57, 95% CI = 1.25–1.97, P = 1.1 × 10−4) and variants in the 5′-UTR. Associations on 6p22.1-p21.31 were histology-specific and included a missense variant in BAT2 associated with squamous-cell carcinoma (rs2736158: OR = 0.64, 95% CI = 0.48–0.85, P = 1.82 × 10−3). Associations on 5p15.33 were detected near TERT, the strongest of which was rs2735940 (OR = 0.82, 95% CI = 0.73–0.93, P = 1.1 × 10−3). This association was stronger among cases with adenocarcinoma (OR = 0.75, 95% CI = 0.65–0.86, P = 8.1 × 10−5). Conclusions Polymorphisms in 5p15.33, 6p22.1-p21.31 and 15q25.1 are associated with lung cancer in African-Americans. Variants on 5p15.33 are stronger risk factors for adenocarcinoma and variants on 6p21.33 associated only with squamous-cell carcinoma. Impact Results implicate the BAT2, TERT and CHRNA5 genes in the pathogenesis of specific lung cancer histologies.