Apoptosis is a form of programmed cell death that is controlled by aspartate-specific cysteine proteases called caspases. In the immune system, apoptosis counters the proliferation of lymphocytes to achieve a homeostatic balance, which allows potent responses to pathogens but avoids autoimmunity. The CD95 (Fas, Apo-1) receptor triggers lymphocyte apoptosis by recruiting Fas-associated death domain (FADD), caspase-8 and caspase-10 proteins into a death-inducing signalling complex. Heterozygous mutations in CD95, CD95 ligand or caspase-10 underlie most cases of autoimmune lymphoproliferative syndrome (ALPS), a human disorder that is characterized by defective lymphocyte apoptosis, lymphadenopathy, splenomegaly and autoimmunity. Mutations in caspase-8 have not been described in ALPS, and homozygous caspase-8 deficiency causes embryonic lethality in mice. Here we describe a human kindred with an inherited genetic deficiency of caspase-8. Homozygous individuals manifest defective lymphocyte apoptosis and homeostasis but, unlike individuals affected with ALPS, also have defects in their activation of T lymphocytes, B lymphocytes and natural killer cells, which leads to immunodeficiency. Thus, caspase-8 deficiency in humans is compatible with normal development and shows that caspase-8 has a postnatal role in immune activation of naive lymphocytes.

Introduction: In the randomized trial of standard-versus high-dose chemoradiotherapy for locally advanced (LA) NSCLC (Radiation Therapy Oncology Group 0617), overall survival (OS) was worse in the high-dose arm. Although heart dose was suggested as a contributing factor, actionable parameters have not been established. We present an analysis of clinical and dosimetric parameters affecting OS in this patient population, focusing on heart dose. Methods: Clinical data were collected on 416 patients with LA NSCLC treated at a single institution, with a subset of 333 available treatment plans recontoured using Radiation Therapy Oncology Group 0617 normal tissue guidelines. Toxicity and dosimetry data were analyzed for 322 patients; multivariate analysis was performed on 251 patients. Dosimetric parameters of radiation to tumor and organs at risk were analyzed with clinical data pertaining to OS, disease-free survival, and toxicity. Results: Patients were treated with radiation therapy to prescribed doses of 50.0 to 84.9 Gy (median 66.0 Gy). Median follow-up was 14.5 months. Median OS was 16.8 months. The 1-and 2-year OS rates were 61.4% and 38.8%, respectively. On multivariate analysis, factors independently associated with worse OS were increasing heart V 50 (volume receiving 50 Gy), heart volume, lung V 5 (proportion of the lung structure [excluding the target volume]) receiving at least 5 Gy), bilateral mediastinal lymph node involvement, and lack of concurrent chemotherapy. When stratified by heart V 50 less than 25% versus 25% or greater, the 1-year OS rates were 70.2% versus 46.8% and the 2-year OS rates were 45.9% versus 26.7% (p < 0.0001). Median heart V 50 was significantly higher (20.8% versus 13.9%, p < 0.0001) for patients with cardiac toxicity with a Common Terminology Criteria for Adverse Events grade of 1 or higher. Conclusions: Heart dose is associated with OS and cardiac toxicity for patients with LA NSCLC treated with chemoradiotherapy.

SUMMARY Holoprosencephaly (HPE), the most common forebrain malformation, is characterized by an incomplete separation of the cerebral hemispheres. Mutations in the homeobox gene SIX3 account for 1.3% of all cases of human HPE. Using zebrafish-based assays, we have now determined that HPE-associated Six3 mutant proteins function as hypomorphs. Haploinsufficiency of Six3 caused by deleting one allele of Six3 or by replacing wild-type Six3 with HPE-associated Six3 mutant alleles was sufficient to recapitulate in mouse models most of the phenotypic features of human HPE. We demonstrate that Shh is a direct target of Six3 in the rostral diencephalon ventral midline (RDVM). Reduced amounts of functional Six3 protein fail to activate Shh expression in the mutant RDVM and ultimately lead to HPE. These results identify Six3 as a direct regulator of Shh expression and reveal a cross-regulatory loop between Shh and Six3 in the ventral forebrain.