Loeys-Dietz syndrome (LDS) is a connective tissue disorder that is characterized by a high risk for aneurysmand dissection throughout the arterial tree and phenotypically resembles Marfan syndrome. LDS is caused by heterozygous missense mutations in either TGF-β receptor gene (TGFBR1 or TGFBR2), which are predicted to result in diminished TGF-β signaling; however, aortic surgical samples from patients show evidence of paradoxically increased TGF-β signaling. We generated 2 knockin mouse strains with LDS mutations in either Tgfbr1 or Tgfbr2 and a transgenic mouse overexpressing mutant Tgfbr2. Knockin and transgenic mice, but not haploinsufficient animals, recapitulated the LDS phenotype. While heterozygous mutant cells had diminished signaling in response to exogenous TGF-β in vitro, they maintained normal levels of Smad2 phosphorylation under steady-state culture conditions, suggesting a chronic compensation. Analysis of TGF-β signaling in the aortic wall in vivo revealed progressive upregulation of Smad2 phosphorylation and TGF-β target gene output, which paralleled worsening of aneurysm pathology and coincided with upregulation of TGF-β1 ligand expression. Importantly, suppression of Smad2 phosphorylation and TGF-β1 expression correlated with the therapeutic efficacy of the angiotensin II type 1 receptor antagonist losartan. Together, these data suggest that increased TGF-β signaling contributes to postnatal aneurysm progression in LDS.

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Irradiated tumor cells transduced with the gene encoding the cytokine GM-CSF have been extensively studied as a vaccine formulation capable of priming systemic antitumor immune responses in the tumor-bearing host. In spite of the therapeutic promise of this vaccine strategy demonstrated in both animal models and early-phase clinical trials, clinical development has been limited by difficulties pertaining to the need to establish in culture the tumor of each patient and to perform individualized gene transfer. To circumvent these issues, we generated an HLA-negative human cell line producing large quantities of human GM-CSF for use as a universal bystander cell to be mixed with unmodified autologous tumor cells in the formulation of a vaccine. This line is easily propagated as a suspension culture in defined, serum-free medium. In a mouse model, we find that vaccination with a mixture of autologous tumor cells and an MHC-negative allogeneic GM-CSF-producing bystander cell primes antitumor immune responses that are equivalent or better than those achieved using autologous tumor cells directly transduced to secrete GM-CSF. This strategy greatly simplifies further clinical development of autologous tumor cell-based vaccines.