Etoposide sensitivity of radioresistant human glioma cell lines

PURPOSE

Malignant gliomas display aggressive local behavior and are not cured by existing therapy. Etoposide, a topoisomerase-II-inhibitor agent, is one of the most active and useful antineoplastic agents. However, etoposide is not usually used on these tumors. We undertook an in vitro study to prove that etoposide is a useful drug for malignant gliomas.

METHODS

Five human glioma cell lines were the basis for this study. Following exposure to various concentrations of etoposide, the glioma cell lines were found to be sensitive; the median concentration inhibiting the number of cells by 50% (IC50) was 8.76 microg/ml (range 8-15.8 microg/ml). Since topoisomerase II is the critical target for etoposide, it was of interest to determine the topoisomerase II activity (decatenation of kinetoplast DNA isolated from Cryphtidia fasciculata) and the etoposide-induced inhibition of topoisomerase II activity.

RESULTS

The topoisomerase II activity was homogeneous in glioma cell lines (average of 50% decatenation with 7,000 cells), and topoisomerase II was the target of the etoposide.

CONCLUSIONS

Our results suggest that topoiomerase II-reactive agents may prove to be clinically useful drugs for patients with malignant gliomas.

Human melanoma metastasis related to specific adhesion with lung cells rather than direct growth stimulation

We previously established a model to study human tumor spontaneous metastasis in immunosuppressed newborn rats. Different observations suggested that the development of pulmonary metastases of human melanoma cells in this animal might reflect, at least partially, an organ specificity phenomenon. We thus examined the "soil" property of the rat lung in terms of growth stimulating activity and specific interactions between tumor cells and pulmonary cells. We could not demonstrate any melanoma cell growth-promoting activity in lung conditioned medium. On the other hand, tumor cell adhesion was drastically enhanced when measured on pulmonary fibroblast monolayers or derived extracellular matrix. Adsorption of lysates of 7GP122 highly metastatic melanoma variant on viable total lung cells enabled us to detect at least 10 proteins or protein subunits which could specifically interact with pulmonary cell membranes, while only one of these proteins was detectable when the same experiment was performed with control liver cells. Conversely, we could show that there exist several corresponding structures on pulmonary cells which could adsorb on tumor cells. Thus, specific cell surface adhesion molecules, leading to specific adhesion between melanoma cells and pulmonary cells, may lead to preferential metastatic development in rat lung.

Therapeutic effects of D-aspartic acid beta-hydroxamate (DAH) on Friend erythroleukemia

D-aspartic acid beta-hydroxamate (DAH), an aspartic acid analogue, exerts anti-tumoral activity against murine leukemia L5178Y both in vitro and in vivo. We show here that DAH displays activity against Friend leukemia cells (FLC) in vitro: a concentration of 2 mM results in a total inhibition of cell growth. DAH is also active in vivo against Friend virus (FV-P)-induced erythroleukemia. Treatment with DAH, given for 95 days as a single daily i.p. injection to DBA/2 mice 3 days following FV-P inoculation, induced a marked increase of 212% in the mean survival time (MST) of treated animals. Since FV-P-induced erythroleukemia is characterized by the proliferation of mature erythroid precursors, we examined the effect of DAH treatment on erythroid colony-forming cells (CFU-E) and observed that the number of CFU-E per spleen was 30 times lower in DAH-treated mice than in the controls. To gain further insight into the early effects of DAH treatment on the early phase of Friend disease, we examined the effects of short DAH treatment on spleen size, hematocrit and viremia in FV-P-infected mice. DAH treatment initiated 3 days post infection (p.i.) inhibited splenomegaly, prevented virus-induced polycythemia, and reduced serum viremia. Late DAH treatment (18 days p.i.) induced regression of FVP-induced disease as evidenced by reduction of spleen weight.

Long term in vitro growth of lymphoblastoid cells in the dog

Attempts to grow in vitro cells from canine lymphoid organs led to observation of the occurrence of a spontaneous, delayed and transitory growth of cells in suspension in two lymphoma cultures (out of 20) but also from one (out of 20) dog with unrelated disorder. These cells, with a lymphoblastoid cytological appearance, lack detectable immunoglobulins in cases studied originating from lymphomatous dogs, and have a pseudodiploid canine karyotype. Neither appearing fully immortalized nor showing any tumorigenicity in nude mice or immunosuppressed newborn rats, these may be of lymphoblastoid nature, rather than arising from some tumorous cells. The mechanisms that have triggered the cell growth are still unknown, but such cells could remind of human lymphoblastoid cells, associated with lymphotrophic viruses, still unknown in the dog.

Intra-cranial transplantation of canine malignant lymphomas in the nude mouse

Intra-cranial grafts of two canine lymphomas, previously maintained by serial sub-cutaneous (s.c.) transplantation, were performed in the nude mouse, in an attempt to characterize lymphoma cell lines in that species which could provide a model of human diffuse large cell B non-Hodgkin's lymphomas. In one of them (DL.24N), the metastatic lesions in the lymph nodes and spleen were unexpectedly predominant, whereas the i.c. growth of the tumour cells, detected histologically, did not lead to any clinical manifestation. In the other one (DL.31N), the i.c. tumour growth led to early clinical symptoms, whereas no metastasis outside the central nervous system could be detected. These observations could provide an interesting tool for studies of the metastatic behaviour of lymphomas.

Study of oncogenic potentialities of human melanoma: identification of N-ras oncogene after DNA transfer and tumour induction

The oncogenic potentialities of human melanoma cells derived from two different patients were studied using DNA-mediated gene transfer into NIH 3T3 cells followed by tumor induction into athymic nude nice. 64% of the mice injected subcutaneously with selected cells which had been co-transfected with human melanoma DNA and the selective marker NeoR developed tumors within 3-4 weeks, while up to 100% of those injected with cells transfected three days before with melanoma DNA developed tumors within 4-6 weeks. Southern blots analysis of the tumors indicated that almost all of them contained human sequences. Hybridization with different oncogene probes showed the presence of an human Eco RI N-ras-hybridizing fragment in the primary and secondary derived tumors, indicating that a transforming N-ras oncogene in human melanoma had been transferred to recipient cells and that transformed cells induced tumors in nude mice.

A potent inhibitor of cell proliferation in "middle molecules" isolated from the urine of uremic patients

A potent inhibitor of cell proliferation was found in the urine of a patient with chronic renal failure. This substance included in "middle molecules" (MM) fraction, was obtained by chromatography. This factor was shown to inhibit noticeably the proliferation of various cells : lymphocytes stimulated by allogeneic cells, monolayer cell lines of normal or tumorous origin and leukemic cell lines derived from acute lymphoblastic leukemia. This effect was reversible and thus could not be related to a direct, rapid cytotoxic effect of MM. Such substances could play an important part in uremic symptoms, such as immunodeficiency, anemia, thrombopenia, gastrointestinal or skin manifestations.

[Serological identification of an antigen associated with acute lymphoid leukemia]

Using as references a lymphoblastoid cell line established from the pleural effusion of a lymphosarcoma patient and the corresponding autochtonous reactive serum, absorption typing assays resulted in the identification of a cell surface antigen associated with acute lymphoid leukaemia. This antigen, provisionally termed PON, may also be demonstrated on the cells of some acute myelomonocytic leukaemias and lymphosarcomas.

Mouse red cell rosette formation by subpopulations of human lymphocytes

In six separate experiments, 7-2% of purified peripheral blood lymphocytes from normal donors were shown to form rosettes with mouse erythrocytes. Normal T and B lymphocytes were separated according to their membrane properties, by E-rosette formation or fractionation on anti F (ab')2 column. The results obtained in both the separation procedures used were in good agreement: T lymphocytes were never found to form mouse red cell rosettes. On the contrary, enrichment of suspensions in B lymphocytes resulted in an increased percentage of mouse red-cell rosette-forming cells. Under the technical condition used, peroxidase-positive monocytes were not shown to form such rosettes. However, if all the mouse red cell rosette-forming cells were shown to be of B nature, not all the B lymphocytes form rosettes with mouse erythrocytes and it is not unlikely that this marker could be characteristic for a subset of Ig-bearing B lymphocytes.

Cytotoxic antibodies to human leukaemia cells in normal human sera

Antibodies cytotoxic for human leukaemia cells were demonstrated in the serum of normal individuals: two of them being the fathers of leukaemia children, the third one being a normal unrelated donor. One of these sera (obtained from the father of an eight years old girl with acute myeloblastic leukaemia) appears to react widely with cells from acute leukaemias, both lymphoid and myeloid. On the other hand, the serum obtained from the normal blood donor appears to react almost exclusively with cells from acute lymphoblastic leukaemias, and more especially with those which do not form rosettes with sheep red cells.