Purpose: Mesothelin (MSLN) is a tumor-associated antigen, being investigated as a biomarker and therapeutic target in malignant pleural mesothelioma (MPM). The biologic function of MSLN overexpression in MPM is unknown. We hypothesized that MSLN may promote tumor invasion in MPM, a tumor characterized primarily by regional aggressiveness and rare distant metastases.Experimental Design: Human and murine MPM cells with MSLN forced expression and short hairpin RNA knockdown were examined for proliferation, invasion, and matrix metalloproteinase (MMP) secretion. The influence of MSLN overexpression on MPM cell invasion was assessed in an orthotopic mouse model and in patient samples.Results: MSLN expression promotes MPM cell invasion and MMP secretion in both human and murine MPM cells. In an orthotopic MPM mouse model characterized by our laboratory, MPM cells with MSLN overexpression preferentially localized to the tumor invading edge, colocalized with MMP-9 expression, and promoted decreased survival without an increase in tumor burden progression. In a tissue microarray from epithelioid MPM patients (n ¼ 139, 729 cores), MSLN overexpression correlated with higher MMP-9 expression at individual core level. Among stage III MPM patients (n ¼ 72), high MSLN expression was observed in 26% of T2 tumors and 51% of T3 tumors.Conclusions: Our data provide evidence elucidating a biologic role for MSLN as a factor promoting tumor invasion and MMP-9 expression in MSLN expressing MPM. As regional invasion is the characteristic feature in MSLN expressing solid cancers (MPM, pancreas, and ovarian), our observations add rationale to studies investigating MSLN as a therapeutic target. Clin Cancer Res; 18(9); 2478-89. Ó2012 AACR.

The fibroblast growth factor (FGF)-FGF receptor (FGFR) signaling system plays critical roles in a variety of normal developmental and physiological processes. It is also well documented that dysregulation of FGF-FGFR signaling may have important roles in tumor development and progression. The FGFR4–FGF19 signaling axis has been implicated in the development of hepatocellular carcinomas (HCCs) in mice, and potentially in humans. In this study, we demonstrate that FGFR4 is required for hepatocarcinogenesis; the progeny of FGF19 transgenic mice, which have previously been shown to develop HCCs, bred with FGFR4 knockout mice fail to develop liver tumors. To further test the importance of FGFR4 in HCC, we developed a blocking anti-FGFR4 monoclonal antibody (LD1). LD1 inhibited: 1) FGF1 and FGF19 binding to FGFR4, 2) FGFR4–mediated signaling, colony formation, and proliferation in vitro, and 3) tumor growth in a preclinical model of liver cancer in vivo. Finally, we show that FGFR4 expression is elevated in several types of cancer, including liver cancer, as compared to normal tissues. These findings suggest a modulatory role for FGFR4 in the development and progression of hepatocellular carcinoma and that FGFR4 may be an important and novel therapeutic target in treating this disease.

No abstract

The extracellular Ca(2+)-sensing receptor (CaR) plays an essential role in mineral homeostasis. Studies to generate CaR-knockout (CaR(-/-)) mice indicate that insertion of a neomycin cassette into exon 5 of the mouse CaR gene blocks the expression of full-length CaRs. This strategy, however, allows for the expression of alternatively spliced CaRs missing exon 5 [(Exon5(-))CaRs]. These experiments addressed whether growth plate chondrocytes (GPCs) from CaR(-/-) mice express (Exon5(-))CaRs and whether these receptors activate signaling. RT-PCR and immunocytochemistry confirmed the expression of (Exon5(-))CaR in growth plates from CaR(-/-) mice. In Chinese hamster ovary or human embryonic kidney-293 cells, recombinant human (Exon5(-))CaRs failed to activate phospholipase C likely due to their inability to reach the cell surface as assessed by intact-cell ELISA and immunocytochemistry. Human (Exon5(-))CaRs, however, trafficked normally to the cell surface when overexpressed in wild-type or CaR(-/-) GPCs. Immunocytochemistry of growth plate sections and cultured GPCs from CaR(-/-) mice showed easily detectable cell-membrane expression of endogenous CaRs (presumably (Exon5(-))CaRs), suggesting that trafficking of this receptor form to the membrane can occur in GPCs. In GPCs from CaR(-/-) mice, high extracellular [Ca(2+)] ([Ca(2+)](e)) increased inositol phosphate production with a potency comparable with that of wild-type GPCs. Raising [Ca(2+)](e) also promoted the differentiation of CaR(-/-) GPCs as indicated by changes in proteoglycan accumulation, mineral deposition, and matrix gene expression. Taken together, our data support the idea that expression of (Exon5(-))CaRs may compensate for the loss of full-length CaRs and be responsible for sensing changes in [Ca(2+)](e) in GPCs in CaR(-/-) mice.