Further characterization of ATP6V0A2-related autosomal recessive cutis laxa.

Autosomal recessive cutis laxa (ARCL) syndromes are phenotypically overlapping, but genetically heterogeneous disorders. Mutations in the ATP6V0A2 gene were found to underlie both, autosomal recessive cutis laxa type 2 (ARCL2), Debré type, and wrinkly skin syndrome (WSS). The ATP6V0A2 gene encodes the a2 subunit of the V-type H(+)-ATPase, playing a role in proton translocation, and possibly also in membrane fusion. Here, we describe a highly variable phenotype in 13 patients with ARCL2, including the oldest affected individual described so far, who showed strikingly progressive dysmorphic features and heterotopic calcifications. In these individuals we identified 17 ATP6V0A2 mutations, 14 of which are novel. Furthermore, we demonstrate a localization of ATP6V0A2 at the Golgi-apparatus and a loss of the mutated ATP6V0A2 protein in patients' dermal fibroblasts. Investigation of brefeldin A-induced Golgi collapse in dermal fibroblasts as well as in HeLa cells deficient for ATP6V0A2 revealed a delay, which was absent in cells deficient for the ARCL-associated proteins GORAB or PYCR1. Furthermore, fibroblasts from patients with ATP6V0A2 mutations displayed elevated TGF-ß signalling and increased TGF-ß1 levels in the supernatant. Our current findings expand the genetic and phenotypic spectrum and suggest that, besides the known glycosylation defect, alterations in trafficking and signalling processes are potential key events in the pathogenesis of ATP6V0A2-related ARCL.

Heterozygous mutations in SIX3 and SHH are associated with schizencephaly and further expand the clinical spectrum of holoprosencephaly.

Schizencephaly (SCH) is a clinically and etiologically heterogeneous cerebral malformation presenting as unilateral or bilateral hemispheric cleft with direct connection between the inner and outer liquor spaces. The SCH cleft is usually lined by gray matter, which appears polymicrogyric implying an associated impairment of neuronal migration. The majority of SCH patients are sporadic, but familial SCH has been described. An initial report of heterozygous mutations in the homeobox gene EMX2 could not be confirmed in 52 patients investigated in this study in agreement with two independent SCH patient cohorts published previously. SCH frequently occurs with additional cerebral malformations like hypoplasia or aplasia of the septum pellucidum or optic nerve, suggesting the involvement of genes important for the establishment of midline forebrain structures. We therefore considered holoprosencephaly (HPE)-associated genes as potential SCH candidates and report for the first time heterozygous mutations in SIX3 and SHH in a total of three unrelated patients and one fetus with SCH; one of them without obvious associated malformations of midline forebrain structures. Three of these mutations have previously been reported in independent patients with HPE. SIX3 acts directly upstream of SHH, and the SHH pathway is a key regulator of ventral forebrain patterning. Our data indicate that in a subset of patients SCH may develop as one aspect of a more complex malformation of the ventral forebrain, directly result from mutations in the SHH pathway and hence be considered as yet another feature of the broad phenotypic spectrum of holoprosencephaly.

Mode of cytotoxic action of T cell-engaging BiTE antibody MT110.

MT110 is an EpCAM/CD3-bispecific antibody construct in clinical development for the treatment of patients with adenocarcinoma expressing EpCAM (CD326). Like other members of this antibody class, MT110 can engage resting, polyclonal CD8(+) and CD4(+) T cells for highly potent redirected lysis of target cells. Here we further explored the mechanism of this action. Complete lysis of EpCAM(+) Kato III gastric cancer cells by previously unstimulated T cells was achieved within 48 h. During this period, a high percentage of CD4(+) and CD8(+) T cells became activated and increased expression of granzyme B. This apparently boosted the capacity for serial target cell lysis as studied at very low effector-to-target ratios. Elimination of cancer cells by MT110-redirected T cells involved membrane damage as was evident from nuclear uptake of propidium iodide and release of the cytosolic enzyme adenylate kinase. Redirected T cells also potently triggered programmed cell death in cancer cells as was evident by membrane blebbing, activation of procaspases 3 and 7, fragmentation of nuclear DNA and cleavage of the caspase substrate poly (ADP ribose) polymerase. Chelation of extracellular calcium fully protected cancer cells from lysis by MT110-redirected T cells, while the pan-caspase inhibitor Z-VAD-FMK blocked activation of procaspases, cleavage of poly (ADP ribose) polymerase and fragmentation of nuclear DNA in cancer cells, but could not prevent nuclear uptake of propidium iodide. Soluble factors did not significantly contribute to cancer cell death. Our study shows that MT110 can efficiently gear up the potential of CD8(+) and CD4(+) T cells for serial lysis, and mediate kill of cancer cells predominantly through poreforming and pro-apoptotic components of cytotoxic T cell granules.

Differential gene expression profile in breast cancer-derived stromal fibroblasts.

BACKGROUND: Breast cancer is characterized by malignant transformation of epithelial cells, but stromal cells also play an important role in tumorigenesis. While tumor-derived fibroblasts display unique phenotypic properties, it is unclear whether they also represent are a specific subpopulation. MATERIALS AND METHODS: Stromal fibroblasts deriving from malignant tissue of 10 women with invasive breast cancer, and from normal breast tissue of 10 women with benign breast disorders, were subjected to differential complementary DNA Microarray Analysis by using a 2,400 gene cDNA array. Individual gene expression pattern were confirmed by RT-PCR. RESULTS: In a cDNA array that allows to analyze the differential gene expression of more than 2,400 genes, the mRNA expression of 135 genes were increased more than 2 fold in fibroblasts from malignant breast tumors. The majority of these genes encode tumor-promoting cytokines, transcription factors and cell-matrix associated proteins. The mRNA expression of 110 genes decreased to less than 0.5 fold. The remaining 2,155 genes were not significantly altered. RT-PCR performed on individual biopsies from breast cancer and normal breast tissues confirmed the validity of the pooled gene expression signature. CONCLUSION: Breast cancer-derived stromal fibroblasts show a distinctive gene expression pattern that differentiates them from normal breast stroma. Our observation of increased expression of tumor promotion-associated genes even in the absence of adjacent malignant epithelium suggests that tumor stroma is comprised of a fibroblastic subpopulation that provides for a microenvironment which supports tumor growth and invasion.

The effect of dexamethasone on polyclonal T cell activation and redirected target cell lysis as induced by a CD19/CD3-bispecific single-chain antibody construct.

BiTE molecules comprise a new class of bispecific single-chain antibodies redirecting previously unstimulated CD8+ and CD4+ T cells for the elimination of target cells. One example is MT103 (MEDI-538; bscCD19xCD3), a CD19-specific BiTE that can induce lysis of normal and malignant B cells at low picomolar concentrations, which is accompanied by T cell activation. Here, we explored in cell culture the impact of the glucocorticoid derivative dexamethasone on various activation parameters of human T cells in response to MT103. In case cytokine-related side effects should occur with BiTE molecules and other T cell-based approaches during cancer therapy it is important to understand whether glucocorticoids do interfere with the cytotoxic potential of T cells. We found that MT103 induced in the presence of target cells secretion by peripheral T cells of interleukin (IL)-2, tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), IL-6, IL-10 and IL-4 into the cell culture medium. Production of all studied cytokines was effectively reduced by dexamethasone at a concentration between 1 and 3x10(-7) M. In contrast, upregulation of activation markers CD69, CD25, CD2 and LFA-1 on both CD4+ and CD8+ T cells, and T cell proliferation were barely affected by the steroid hormone analogue. Most importantly, dexamethasone did not detectably inhibit the cytotoxic activity of MT103-activated T cells against a human B lymphoma line as investigated with lymphocytes from 12 human donors. Glucocorticoids thus qualify as a potential co-medication for therapeutic BiTE molecules and other cytotoxic T cell therapies for treatment of cancer.