Hui-Kuo G. Shu

Id2 Promotes Apoptosis by a Novel Mechanism Independent of Dimerization to Basic Helix-Loop-Helix Factors

ABSTRACT Members of the helix-loop-helix (HLH) family of Id proteins have demonstrated roles in the regulation of differentiation and cell proliferation. Id proteins inhibit differentiation by HLH-mediated heterodimerization with basic HLH transcription factors. This blocks their sequence-specific binding to DNA and activation of target genes that are often expressed in a tissue-specific manner. Id proteins can also act as positive regulators of cell proliferation. The different mechanisms proposed for Id-mediated promotion of entry into S phase also involve HLH-mediated interactions affecting regulators of the G1/S transition. We have found that Id2 augments apoptosis in both interleukin-3 (IL-3)-dependent 32D.3 myeloid progenitors and U2OS osteosarcoma cells. We could not detect a similar activity for Id3. In contrast to the effects of Id2 on differentiation and cell proliferation, Id2-mediated apoptosis is independent of HLH-mediated dimerization. The ability of Id2 to promote cell death resides in its N-terminal region and is associated with the enhanced expression of a known component of the programmed cell death pathway, the proapoptotic gene BAX.

Near complete surgical resection predicts a favorable outcome in pediatric patients with nonbrainstem, malignant gliomas: Results from a single center in the magnetic resonance imaging era

Because few reports on outcome in patients with pediatric malignant gliomas during the magnetic resonance imaging era were available, the authors studied the outcomes of children with these tumors at their institution.

Overexpression of E2F1 in glioma-derived cell lines induces a p53-independent apoptosis that is further enhanced by ionizing radiation

Glioma cell lines show variable responses to radiation in a manner influenced by their p53 status. Irradiation of glioma cell lines does not generally induce apoptosis. When wild-type p53 is present, these cells undergo a G1 arrest that is closely associated with increased radiosensitivity as measured by clonogenic survival. Previously, others have shown that dysregulated overexpression of E2F1 induces apoptosis in cell lines with either functional or inactivated p53. We found that regardless of p53 status, apoptosis induced by overexpression of E2F1 in glioma cell lines was further enhanced by treatment with ionizing radiation. BAX induction did not follow E2F1 overexpression or irradiation in the glioma cell lines tested. Thus, the apoptotic response of glioma-derived cells to irradiation can be enhanced by E2F1 by a mechanism that does not involve the induction of BAX.

Radical pleurectomy/decortication and intraoperative radiotherapy followed by conformal radiation with or without chemotherapy for malignant pleural mesothelioma

OBJECTIVES We performed a retrospective review of the efficacy and morbidity of radical pleurectomy/decortication and intraoperative radiotherapy followed by external beam radiation therapy with or without chemotherapy for diffuse malignant pleural mesothelioma. METHODS A total of 32 patients with diffuse malignant pleural mesothelioma were initially evaluated between January 1995 and September 2000. Three patients were excluded from analysis because of unresectable disease. Two patients died postoperatively, and one patient had recurrent disease previously treated at an outside institution. Of the remaining 26 patients included in the analysis, 24 received intraoperative radiotherapy. External beam radiation therapy was generally started 1 to 2 months after resection and delivered by means of 3-dimensional conformal radiation therapy or with inverse treatment planning intensity-modulated radiation therapy. When given, chemotherapy consisted of 2 to 3 cycles of cyclophosphamide, doxorubicin (Adriamycin), and cisplatin initiated 1 to 2 months after completion of radiation. RESULTS At the time of data analysis, 5 of 26 patients were alive. The median follow-up was 9.7 months (range, 2-67.6 months). The median overall survival and progression-free interval from the time of the operation were 18.1 and 12.2 months, respectively. The Kaplan-Meier estimates of overall survival and freedom from progression at 1 year were 64% and 50%, respectively. The site of failure was mostly locoregional. However, there were 4 abdominal failures and 1 contralateral lung failure. CONCLUSIONS Radical pleurectomy/decortication with aggressive radiotherapy with or without chemotherapy might offer an alternative treatment option to those who cannot tolerate extrapleural pneumonectomy.

Bax can associate with ferritin heavy chain (FHC) resulting in inhibition of bax-mediated apoptosis

Materials and Methods: A yeast two-hybrid system was used with the Bax BH3 domain serving as the “bait” to find potential interacting proteins from a HeLa cell cDNA library. A glutathione-S-transferase (GST)-FHC and a histidine (His)-tagged Bax were bacterially expressed and isolated using either glutathione or nickel beads. In vitro translation of FHC was performed using rabbit reticulocyte lysate with T7 transcribed FHC RNA. A hemaglutinin (HA)-tagged Bax was expressed stably under the control of a tetracycline promoter in GM701, a human fibroblast cell line (GM701/tet-Bax). In vitro associations were demonstrated by mixing either GST-FHC bound to glutathione beads with purified His-Bax or HA-Bax bound to anti-HA antibody:protein A sepharose bead with in vitro translated FHC and assessing on immunoblots for bound Bax or FHC, respectively. Transient transfections into 293T cells were performed using a standard calcium phosphate precipitation method with the pcDNA-3 vector used to express the genes of interest. In vivo association was detected by performing immunoprecipitation (IP) with anti-FHC antibody using 293T lysates transiently expressing HA-Bax and FHC, and subsequently, immunoblotting this IP using anti-HA antibody to detect Bax in the complex. Apoptosis was assessed 24 hours following either transfection in 293T cells or withdrawal of tetracycline in the GM701/tet-Bax cells by determining the percentage of propidium iodide-stained cells with sub-diploid DNA content on a fluorescence-activated cell sorter.