ABSTRACT
Apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) is silenced by promoter methylation in many types of tumors, yet ASC's role in most cancers remains unknown. Here, we show that ASC is highly expressed in a model of medulloblastoma, the most common malignant pediatric brain cancer; ASC is also expressed in human medulloblastomas. Importantly, while ASC deficiency did not affect normal cerebellar development, ASC knockout mice on the Smoothened (ND2:SmoA1) transgenic model of medulloblastoma exhibited a profound reduction in medulloblastoma incidence and a delayed tumor onset. A similar decrease in tumorigenesis with ASC deficiency was also seen in the hGFAP-Cre:SmoM2 mouse model of medulloblastoma. Interestingly, hyperproliferation of the external granule layer (EGL) was comparable at P20 in both wild-type and ASC-deficient SmoA1 mice. However, while the apoptosis and differentiation markers remained unchanged at this age, proliferation makers were decreased, and the EGL was reduced in thickness and area by P60. This reduction in proliferation with ASC deficiency was also seen in isolated SmoA1 cerebellar granule precursor cells in vitro, indicating that the effect of ASC deletion on proliferation was cell autonomous. Interestingly, ASC-deficient SmoA1 cerebella exhibited disrupted expression of genes in the transforming growth factor-ß pathway and increased level of nuclear Smad3. Taken together, these results demonstrate an unexpected role for ASC in Sonic hedgehog-driven medulloblastoma tumorigenesis, thus identifying ASC as a promising novel target for antitumor therapy.
Subject(s)
Apoptosis Regulatory Proteins/genetics , Cell Proliferation , Cerebellar Neoplasms/genetics , Medulloblastoma/genetics , Adolescent , Adult , Animals , Apoptosis Regulatory Proteins/deficiency , CARD Signaling Adaptor Proteins , Cerebellar Neoplasms/metabolism , Cerebellar Neoplasms/pathology , Child , Child, Preschool , Cytoskeletal Proteins/genetics , Cytoskeletal Proteins/metabolism , Female , Gene Expression Profiling , Gene Expression Regulation, Neoplastic , Humans , In Situ Hybridization , Infant , Male , Medulloblastoma/metabolism , Medulloblastoma/pathology , Mice, Knockout , Mice, Transgenic , Oligonucleotide Array Sequence Analysis , Reverse Transcriptase Polymerase Chain Reaction , Signal Transduction/genetics , Transforming Growth Factor beta/genetics , Transforming Growth Factor beta/metabolism , Young AdultABSTRACT
A specialized serum ferritin assay has been developed for the detection of iron deficiency in epidemiologic studies. An enzyme immunoassay (EIA) was employed to eliminate the need for radioisotopes. The problem of low sensitivity inherent with the EIA for serum ferritin was eliminated by the use of monoclonal immunologic reagents. The working range of the assay is 1-100 micrograms/L with a sensitivity of 0.5 micrograms/L. Excellent agreement in serum ferritin levels was observed between the present method and the two-site immunoradiometric assay (IRMA), while the variability at low ferritin concentrations was significantly less with the EIA. Because only 10 microliter of serum is required for each assay, duplicate measurements can be performed on a single capillary tube of blood. When an automatic microtiter plate reader for optical density measurements is used, 80-100 duplicate determinations can be completed by one technologist in a single working day.
