Significance of retinoblastoma and mdm2 gene expression as prognostic markers for soft-tissue sarcoma

The growth regulatory function of the retinoblastoma protein (RB) can be suppressed by mdm2 via RB/mdm2 interaction by perturbation of the RB suppression of the E2F function. The goal of this study was to examine the clinical value of immunohistochemical (IHC) RB detection and its relationship to mdm2 overexpression in a cohort of 198 adult primary soft-tissue sarcomas (STS). RB overexpression reveals, multivariately, a correlation with survival (RR = 1.59, P = 0.037) as well as mdm2 positivity (RR = 2.32, P = 0.0035). Stratification of RB results to mdm2 staining shows a prognostic graduation in four levels. Patients with positivity for both antibodies have the highest risk (RR = 3.30, P = 0.002) and the poorest prognosis (projected 5-year survival rate, 18.6%); those with negativity for both antibodies show the most favourable prognosis (projected 5-year survival rate, 63.4%). Intermediately, an isolated RB overexpression (projected 5-year survival rate, 46.1%) is more favourable than an isolated mdm2 positivity (projected 5-year survival rate, 33.5%). To sum up, this study proves that RB and mdm2 overexpression have an individual and also an additive effect on prognosis in STS. Received: 3 June 1997     

Growth inhibition of human keratinocytes by MC903 (calcipotriol) is linked to dephosphorylation of retinoblastoma gene product

Aim This paper compares the effects of MC903 (calcipotriol) and 1,25-dihydroxyvitamin D₃[1,25(OH)₂D₃; calcitriol] on differentiation and proliferation of normal human keratinocytes cultured in serum-free medium. In order to understand the inhibitory mechanism of MC903, we examined its effect on cell cycle kinetics and the phosphorylation of retinoblastoma gene product (pRB), a tumor suppressor gene products, in normal human keratinocytes. Background The hormonally active form of vitamin D₃, 1,25-dihydroxy vitamin D₃ [1,25(OH)₂D₃], regulates the differentiation and proliferation of epidermal keratinocytes in vitro. MC903 is a novel vitamin D₃ analogue which is at least 100 times less potent than 1,25(OH)₂D₃ in its effects on calcium homeostasis. Methods We analyzed cell differentiation and cell cycle by flow cytometry using a FACScan, and pRB phosphorylation by Western blotting and densitometer. Results MC903 induced growth inhibition and differentiation of human keratinocytes. Cell cycle analysis demonstrated that 10^-6 M of MC903 induced cell cycle arrest in both G1/G0 (62.4 ± 0.7% versus 56.5 ± 1.7% in control, p < 0.01) and G2 + M (19.2 ± 0.3% versus 14.0 ± 0.9% in control, p < 0.01) phase. 10^-6 M of MC903 also increased the depnosphorylated pRB from 25% at 0 h to 84% at 48 h, as well as 1,25(OH)₂D₃. Conclusions Since pRB phosphorylation is supposed to be essential for the progression from G1 to S phase, the inhibition of pRB phosphorylation could be responsible for the G1/G0 growth arrest induced by MC903 in normal human keratinocytes.     

Biochemical characterization and membrane expression of an antigen shared by activated and neoplastic cells of neuroectodermal origin

The reactivity of a mAb (M16) raised against a small cell lung carcinoma line is described. M16 identifies a surface antigen expressed on cells of neuroectodermal origin following activation, as well as neoplastic transformation. M16 antigen expression is increased on retinoblastoma and neuroblastoma cell lines upon ‘in vitro’ stimulation and it is induced ‘in vivo’ on glial cells activated following brain injury. Furthermore, glial tumors show levels of M16 molecule expression increasing with the degree of malignancy, and in a retinoblastoma cell line, the expression of M16 was inversely related to the level of HLA-Class I and N-CAM antigens. The M16 antigen may represent a marker of both activation and neoplastic progression for neuroectodermal cells.     

Retinoma and Phthisis Bulbi of Retinoblastoma 1.Clinical and Genetic Analysis

Retinoma and phthisis bulbi of retinoblastoma are rare entitiesfound in retinoblastoma patients and their relatives.Eleven cases of phthisisbulbi of retinoblastoma and 9 cases of retinoma were identified from 1966 to1991 in our center.The clinic data show that retinoma and phthisis bulbi areclosely related to the retinoblastoma gene.Enucleation should be carried outas soon as possible without hesitation for the phthisis of eyes with retinoblas-toma.Genetic counseling and frequent observation should be paid attention toretinoma patients and their offspring.The mechanism of retinoma developed isdiscussed.We propose that the diversity of second mutation might be thecause of retinoma.Eye Science 1992;8:117-121.     

急性白血病细胞Rb蛋白表达的研究

作者用免疫组化方法检测了40例急性白血病细胞中Rb基因蛋白的表达情况，结果发现，Rb蛋白表达缺失率为37．5％，以M_5亚型多见，占41．6％。结果表明，Rb基因表达状态与急性白血病的类型有关，并影响患者的疗效和预后。     

MR imaging in retinoblastoma

We studied the appearance of retinoblastoma on unenhanced and gadolinium-enhanced images and the accuracy of tumour staging with MR imaging. The MR images were obtained in 18 children with retinoblastoma and compared with histopathological findings after enucleation. The MR imaging included T1-weighted and dual-echo T2-weighted images before, and T1-weighted images after, gadopentetate dimeglumine injection. The contrast between tumour and ipsilateral vitreous strongly increased (57%) after gadolinium on T1-weighted images (p=0.004). Tumour was strongly hypointense as compared with ipsilateral vitreous in all patients using heavily T2-weighted (TE=120 ms) images (p=0.001). The estimated T2 of tumour (mean 96+14 ms) did not correlate with histological grading or degree of calcification. Unenhanced T1-weighted MR images rightfully excluded extrascleral growth in 16 of 16 cases, but its presence was confirmed after enucleation in only one of 2 abnormal MR scans. Invasion of the optic nerve behind the cribriform plate was confirmed in 2 of 3 abnormal gadolinium-enhanced MR scans, but also in 1 of the 15 cases in which MR images were normal. The T2-weighted images were useful in assessing retinal detachment. We conclude that heavily T2-weighted images, unenhanced T1-weighted images and gadolinium-enhanced T1-weighted MR images are complementary in characterizing and staging retinoblastoma.     

Transcription by RNA polymerases I and III: a potential link between cell growth, protein synthesis and the retinoblastoma protein

 The rate of protein synthesis is a critical determinant of cellular growth. Abnormal activation of this process is a frequent feature of transformed and tumour cells. Several distinct components of the translation apparatus have been shown to be deregulated in response to malignant transformation. Indeed, overexpression of certain translation factors has been found to predispose cells to transformation or even initiate it. The latest twist to this story comes from the discovery that the retinoblastoma protein RB plays a major role in restricting the production of tRNA and rRNA. RB is an important tumour suppressor. Its ability to limit the synthesis of these principle determinants of biosynthetic capacity could provide a mechanism for restraining cell growth. The loss of this control may constitute a significant step towards tumour progression. Received: 4 February 1997 / Accepted: 18 July 1997     

Detection of Gangliosides as N-Glycolylneuraminic Acid-specific Tumor-associated Hanganutziu-Deicher Antigen in Human Retinoblastoma Cells

Gangliosides were shown to bear the tumor-associated N -glycolylneuraminic acid (NeuGc)-specific Hanganutziu-Deicher (HD) antigen expressed in human retinoblastoma cells. HD antigenie gangliosides were detected by thin-layer chromatography/enzyme-immunostaining using affinity-purified chicken antibody against GM3 containing NeuGc and horseradish peroxidase-conjugated anti-chicken IgG. One to four species of the antigenic gangliosides were detected from all of 4 cell lines, Y79, WERI-Rb1, TOTL1, and YK, as well as freshly cultured retinoblastoma cells and isolated tumor tissue. All cases contained GMS(NeuGc) as an HD antigen. No HD antigenic ganglioside was detected in normal retinal tissues by the same procedure.     

siRNA介导的E2F-1基因沉默对胃癌细胞MGC803中Rb蛋白表达水平的影响

目的 应用RNA干扰技术研究E2F-1基因沉默在人胃癌MGC803细胞中对Rb蛋白表达的影响.方法 将重组质粒E2F-1-siRNA转染MGC803细胞,筛选稳定株,利用RT-PCR检测转染前后细胞E2F-1 mRNA表达水平,并通过蛋白免疫印记法（Western blot）检测各组细胞E2F-1蛋白的表达水平来验证质粒转入胃癌细胞的情况.采用Western blot检测三组细胞中总Rb蛋白和磷酸化Rb蛋白的表达情况,计算出非磷酸化Rb蛋白表达情况,统计各组间的差异.结果 重组质粒E2F-1-siRNA成功转入胃癌细胞中;有效抑制了E2F-1 mRNA的表达,E2F-1蛋白水平显著下降,与阴性对照组及未转染组相比分别降低了83.2%和84.6%,去磷酸化Rb蛋白分别增加了61.22%（P〈0.05）和66.60%（P〈0.05）,差异有统计学意义.结论 沉默表达E2F-1基因后,可以有效降低Rb蛋白的水平,促进其活化形式去磷酸化Rb蛋白的产生.     

苦参碱对视网膜母细胞瘤细胞survivin和端粒酶活性表达的影响

目的 研究苦参碱对视网膜母细胞瘤(RB)细胞凋亡抑制蛋白survivin和端粒酶活性表达的影响,探讨苦参碱对Rb的作用机制.方法 体外培养视网膜母细胞瘤患者HXO-Rb细胞经不同浓度的苦参碱作用后,采用噻唑蓝比色法测定细胞生长情况,RT-PCR检测survivin RNA水平,聚合酶链法(PCR)检测端粒酶活性.结果 苦参碱在一定范围内可抑制HXO-Rb细胞的生长,使survivin mRNA表达下调.可明显观察到细胞凋亡的形态学改变,端粒酶活性明显下降,细胞凋亡率增加.结论 苦参碱可以增加HXO-RB细胞凋亡,可以减少RB细胞mRNA表达,减弱RB细胞端粒酶活性,影响其周期变化,抑制RB细胞系增殖.其对survivin的抑制,及端粒酶活性的下降可能是诱发RB细胞凋亡的原因.