A new approach to hybrid hybridoma construction based on the use of an actinomycin D-resistant myeloma cell line

Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR E. A. Zotikov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 112, No. 11, pp. 511–514, November, 1991.     

mTOR inhibitors blunt the p53 response to nucleolar stress by regulating RPL11 and MDM2 levels

Mechanistic target of rapamycin (mTOR) is a master regulator of cell growth through its ability to stimulate ribosome biogenesis and mRNA translation. In contrast, the p53 tumor suppressor negatively controls cell growth and is activated by a wide range of insults to the cell. The mTOR and p53 signaling pathways are connected by a number of different mechanisms. Chemotherapeutics that inhibit ribosome biogenesis often induce nucleolar stress and activation of p53. Here we have investigated how the p53 response to nucleolar stress is affected by simultaneous mTOR inhibition in osteosarcoma and glioma cell lines. We found that inhibitors of the mTOR pathway including rapamycin, wortmannin, and caffeine blunted the p53 response to nucleolar stress induced by actinomycin D. Synthetic inhibitors of mTOR (temsirolimus, LY294.002 and PP242) also impaired actinomycin D triggered p53 stabilization and induction of p21. Ribosomal protein (RPL11) is known to be required for p53 protein stabilization following nucleolar stress. Treatment of cells with mTOR inhibitors may lead to reduced synthesis of RPL11 and thereby destabilize p53. We found that rapamycin mimicked the effect of RPL11 depletion in terms of blunting the p53 response to nucleolar stress. However, the extent to which the levels of p53 and RPL11 were reduced by rapamycin varied between cell lines. Additional mechanisms whereby rapamycin blunts the p53 response to nucleolar stress are likely to be involved. Indeed, rapamycin increased the levels of endogenous MDM2 despite inhibition of its phosphorylation at Ser-166. Our findings may have implications for the design of combinatorial cancer treatments with mTOR pathway inhibitors.     

P38MAPK regulates caspase-3 by binding to caspase-3 in nucleus of human hepatoma Bel-7402 cells during anti-Fas antibody- and actinomycin D-induced apoptosis

Anti-Fas antibody- and actinomycin D (FA/AD) has been shown to have anti-tumor activity in some tumor cells. However, many of the molecular mechanism of FA/AD-induced apoptosis of human hepatoma Bel-7402 cells have not been fully clarified. In the present study, therefore, the effect of FA/AD in presence or absence of p38MAPK inhibitor SB203580 on the proliferation, apoptosis, p38MAPK, caspase-3, location of p38MAPK and caspase-3, and interaction between p38MAPK and caspase-3 in Bel-7402 cell was investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT), annexin V-FITC/propidium iodide (PI) double staining, electron microscopy, immunoblot, immunofluorescence and immunoprecipitation/immunoblot assay, respectively. We found that FA/AD significantly resulted in the inhibition of proliferation, induction of apoptosis, activation and up-regulation of p38MAPK, activation and up-regulation of caspase-3, translocation of p38MAPK and caspase-3 from cytosol to nucleus, and formation of p38MAPK/caspase-3 complex in Bel-7402 cells. In contrast, SB203580, a p38MAPK-specific inhibitor, apparently blocked induction of apoptosis, activation and up-regulation of p38MAPK, activation and up-regulation of caspase-3, and translocation of p38MAPK and caspase-3 from cytosol to nucleus in FA/AD-treated Bel-7402 cells. Taken together, we conclude that p38MAPK regulates caspase-3 by binding to caspase-3 in nucleus of Bel-7402 cells during FA/AD-induced apoptosis.     

Gestational trophoblastic neoplasia

Gestational trophoblastic neoplasia (GTN) is one of the most curable malignancies because of the intrinsic sensitivity of the tumor to certain antineoplastic agents, effective sensitive assays for human chorionic gonadotropin (hCG), and identification of high‐risk factors that permit individualized treatment. Chemotherapy is the main modality of treatment in patients with GTN. The cure rate in patients with low‐risk GTN is 100%, and is estimated to exceed 80% in patients with high‐risk GTN. Management of GTN is based on staging (anatomical involvement staging) and scoring. Patients with persistent GTN and stage I or score ≤ 6 (low risk) should be managed with single agent chemotherapy (methotraxate or actinomycin), but patients with stage IV or score ≥ 7 (high risk) need combination chemotherapy. Gestational trophoblastic neoplasia is radiosensitive, because radiation has hemostatic and tumorocidal effect on GTN. Therefore, radiotherapy can be used in treatment of some patients with brain hepatic metastasis or in patients where chemotherapy is not possible due to medical problems. Surgery can be used in patients who are resistant to chemotherapy or in hemorrhagic cases. Surgical resection of the tumor is the main form of therapy for placental site trophoblastic tumor. This surgery consists of a hysterectomy for the majority of patients as the disease is confined to the uterus.     

Screening for induction of differentiation and toxicity to blast cells by chemotherapeutic compounds in human myeloid leukemia

Bone marrow cells from 9 patients with acute myeloid leukemia and 1 patient with a blast crisis of chronic myeloid leukemia were cultured to determine their ability to be induced to differentiate by different chemotherapeutic compounds. Five of these 10 patients showed differentiation to granulocytic and/or monocytic cells by culture with medium containing the myeloid cell differentiation-inducing protein MGI-2. Actinomycin D induced differentiation in cells from 2 of the patients who did not show differentiation with MGI-2 containing medium. In these 7 patients there was an increase in the ratio of differentiated myeloid cells to blasts. None of these 10 patients showed induction of differentiation by cytosine arabinoside, adriamycin, or daunomycin, but treatment with these compounds showed in some patients an increase in the ratio of differentiated myeloid cells to blasts. The results indicate that this ratio can be increased by differentiation and also in some patients by toxicity to blast cells. With dexamethasone or vinblastine there was no induction of differentiation and no increase in this ratio in any of the 10 patients tested. After in vivo chemotherapy with low dose cytosine arabinoside, cells from one patient showed a similar response in culture to actinomycin D as cells before chemotherapy, whereas in another patient the cells had acquired the ability to respond to actinomycin D. In contrast, after high-dose in vivo chemotherapy with cytosine arabinoside and daunomycin, cells from a third patient seemed to have lost the ability to differentiate in vitro by MGI-2 containing medium or actinomycin D. The results indicate that pre-screening for differentiation-inducing compounds and compounds that show toxicity to blast cells should be useful to select the appropriate compounds to be used for therapy, and that it is advisable to screen the cells both before and after initiation of therapy.     

抑制C—myc基因表达对移植血管狭窄的影响

目的观察放射菌素D对移植血管中C-myc基因表达及内膜增殖的影响。方法建立大鼠自体静脉移植模型，实验组分别于术前、术后应用不同剂量放射菌素D（0.015，0.15mg/kg），对照组仅做血管移植。分别于术后2h及1周切取移植静脉，应用原位杂交方法检测C-mycmRNA表达，应用计算机图像分析仪测量内膜厚度。结果高剂量组C-mycmRNA表达较对照组明显减少（6.5%，12.5%；P<0.01），移植血管内膜增殖受到明显抑制（18.7，28.5μm；P<0.01）。结论大剂量应用放射菌素D可以抑制C-mycmRNA表达，从而抑制移植血管内膜增殖。早期应答基因C-myc表达在诱导平滑肌细胞增殖中起着重要作用。     

EMA/CO Regimen Chemotherapy for Gestational Trophoblastic Tumor

FromMay,1994toMay,1999,etoposide,methotrexate,actinomycinD,vincristineandcyclophosphamide(EMA/CO)chemotherapywasusedforgestationaltrophoblastictumor(GTT)inNMIHH.Therewere41caseswithcompletedata.Followingisourreport.MaterialsandMethodsDiagnosticStandardofGestationalTroph-oblasticTumorHistologicallyinvasivemolewascharacter-izedbysheetsofanaplasticsyncytiotrophoblastorcytotrophoblastwithchorionicvilliinherhistopathologicalsectionofmyomertrialinvasionandparametriummetastasestissue,andchor…     

Phase II evaluation of dibromodulcitol and actinomycin D,hydroxyurea, and cyclophosphamide in previously untreated patients with malignant melanoma

In this Eastern Cooperative Oncology Group (ECOG) phase II study, dibromodulcitol (DBD) and a combination of actinomycin D, hydroxyurea, and cyclophosphamide (AHC) were compared with methyl-CCNU, the current ECOG standard, in patients who had received no prior chemotherapy for disseminated malignant melanoma. The response rates were 6% (3/50) for AHC, 9% (3/34) for DBD, and 14% (7/49) for methyl-CCNU. Median survival times were 4, 5, and 6 months, respectively. Neither regimen appears to offer any advantage over methyl-CCNU as front-line therapy for patients with disseminated melanoma.     

Salvage chemotherapy with methotrexate,etoposide and actinomycin D in men with metastatic nonseminomatous germ cell tumors with a choriocarcinoma component: A preliminary report

The objective of the present study was to assess the use of salvage chemotherapy using methotrexate, etoposide and actinomycin D (MEA) in men with nonseminomatous germ cell tumor (NSGCT) with a choriocarcinoma component. Nine patients were included. They had initially received bleomycin, etoposide and cisplatin, and high‐dose ifosfamide, carboplatin and etoposide as induction chemotherapies. However, they failed to achieve the normalization of β‐human chorionic gonadotropin (β‐HCG). Therefore, MEA therapy (methotrexate: 450 mg/body on day 1, actinomycin D: 0.5 mg/body on days 1–5, etoposide: 100 mg/body on days 1–5) was subsequently administered. After MEA therapy (median: 3 cycles), serum β‐HCG was normalized in five of the nine patients. Of these five, three achieved long‐term disease‐free survival and one died of disease unrelated to NSGCT, whereas the remaining patient developed disease recurrence and died of disease progression. All four patients who failed to achieve the normalization of β‐HCG died of disease progression. Although several severe toxicities greater than grade 3, which were mainly associated with bone marrow suppression, occurred in all patients, there was no treatment‐related death. Considering the current outcomes, MEA regimen could be an attractive option as a salvage chemotherapy for metastatic NSGCT patients with a choriocarcinoma component showing resistance to intensive conventional chemotherapies.