Biomedical subjects

O Fodstad

Publications and source records attributed to O Fodstad.

At least 109 records · Page 6Linked to original sources

PubMed1991

Chromosome 13 alterations in osteosarcoma cell lines derived from a patient with previous retinoblastoma.

Various sublines of cells established from an osteosarcoma that developed in a patient (O.H.) with previous bilateral retinoblastoma were examined for different restriction fragment-length polymorphisms of chromosome 13q, as well as for rearrangements of the retinoblastoma gene using a cDNA probe. The independently established sublines were used to help separate primary and secondary events taking place in tumorigenesis of the osteosarcoma of this patient. Information from the present DNA analysis, taken together with data from cytogenetic and enzymatic studies on chromosome 13 in the cell lines, revealed both common and distinct genetic changes on chromosome 13q. The common changes may indicate the nature of the first and second mutational events in the development of the osteosarcoma. The first, constitutional cancer predisposing mutation seemed to be a base mutation or a small deletion/insertion, and the second event involved a deletion of a larger part of the long arm of chromosome 13. The distinct genetic changes included other deletion and duplication events of chromosome 13q. The existence of multiple sublines with different genetic constitutions provides improved possibilities for gaining insight into the nature of the genetic lesions leading to tumor formation, as these may reflect the clonal variation present in the primary tumor. We also demonstrate the difficulty of inferring from single tumor cell isolates to properties of the primary tumor.

Chromosome Aberrations↗

PubMed1991

Selection of anti-SCLC antibodies for diagnosis of bone marrow metastasis.

The binding profile of 17 monoclonal antibodies (MAbs) to small lung cancer cell lines and normal bone marrow and peripheral blood cells was studied by immunocytochemistry and flow cytometry. At antibody concentrations that stained PJD tumour cells, only four MAbs (MOC1, MOC31, NrLu10, 81A6) were devoid of cross-reactivity with normal cells, whereas significant binding to subtypes of bone marrow and blood cells was seen for 13 antibodies. For the eight most promising MAbs the binding to ten SCLC cell lines was moderate to strong in 47 MAb/cell line combinations, and low or insignificantly in 33 combinations. Three cell lines lacked antigen for all MAbs studied. Flow cytometry was significantly less sensitive than immunocytochemistry in assessing MAb binding to both normal and tumour cells. The antigen expression was for several MAbs higher in exponentially growing tumour cells than in cells in stationary growth phase. Seven of the MAbs, which originally showed low to moderate cross-reactivity with normal cells, were titrated down to the lowest concentrations at which they stained H-146 tumour cells with high levels of antigen expression. At these concentrations five (MLuC1, Oat-1, SM-1, NCC-Lu-243, LAM2) of the seven Mabs showed acceptably low binding to bone marrow cells. At optimal concentrations altogether four to nine of the 17 antibodies studied may be used to detect tumour cell involvement in bone marrow of SCLC patients.

Antibodies, Monoclonal↗

PubMed1990

Nude rat model for studying metastasis of human tumor cells to bone and bone marrow.

Bone metastases reproducibly developed in nude rats after an injection of LOX human malignant melanoma cells into the left ventricle, with hind leg paralyses appearing in all animals within approximately 2 weeks. Manifest metastases were present exclusively in the skeletal system, predominantly in the lumbar portion of the spine, the long bones, and occasionally in the skull. Intracardially injected 125I-labeled tumor cells and monodisperse microspheres were distributed in parallel to the various tissues. Moreover, because the levels of radioactivity were significantly lower in bone than in lung, kidney, and liver, the pattern of metastases could not be explained solely by hemodynamic factors. In chemotherapy experiments, the survival time of rats given left ventricular injections of LOX cells increased in a dose-dependent manner after the animals were treated with dacarbazine. Researchers may find the model useful for studying the biology of bone metastases and for testing the sensitivity of these lesions to drugs.

Age Factors↗

PubMed1989

A human tumor lung metastasis model in athymic nude rats.

Experimental lung metastases regularly developed in athymic Han:rnu/rnu Rowett rats after i.v. injection of LOX human malignant melanoma cells. When 5 x 10(5) tumor cells were injected into 4-week-old rats, 89% of the animals died of lung tumors, with a mean survival time of 18 days. With 5- and 6-week-old rats, however, the fraction of animals that died decreased to 80 and 46%, with mean survival times of 35 and 38 days, respectively. The number of detectable lung colonies in each animal was about 35 in 5- and 6-week-old animals, compared to nearly 300 in 4-week-old rats. In the latter, a correlation was found between the number of tumor cells injected and the number of detectable lung colonies. The capacity of the LOX tumor to grow s.c. and to form experimental lung metastases was, by and large, similar in young nude rats and in nude mice, and no significant difference in morphology between the different tumors in the two species was seen. A high-resolution radiographic method was used to visualize lung colonies in the nude rats, and single tumors with diameters as small as 2-4 mm could be detected. By this method, for the first time, the effect of chemotherapy on a human tumor growing in a visceral organ of a rodent host could be followed by repeat X-ray examinations, mimicking a situation commonly faced in the clinic. This procedure may prove particularly useful for experimental chemotherapy studies, and may be extended to other human tumors that frequently metastasize to the lungs. Indications were obtained that some host-specific differences in tissue-preferenced growth might exist, a possibility that will be further explored.

Animals↗

PubMed1989

Antibodies detecting abnormalities of the retinoblastoma susceptibility gene product (pp110RB) in osteosarcomas and synovial sarcomas.

The retinoblastoma (RB) susceptibility gene is one member of a putative "cancer suppressor gene" family in which loss of gene function is associated with tumor formation. Using antibodies generated against a trypE-RB fusion protein, we previously identified a nuclear phosphoprotein, pp110RB, as the RB gene product. Here we describe three additional polyclonal antibodies that were generated to separate epitopes of pp110RB with three synthetic peptides deduced from the RB cDNA sequence. All four antibodies could specifically recognize the same phosphoprotein in human cells. This protein was phosphorylated on serine and threonine, but not tyrosine, residues. RB homologous proteins with molecular masses of 105-128 kD were detected in other vertebrates, such as monkey, rodent, and chicken, by at least two antibodies, indicating evolutionary conservation of the RB gene. These antibodies were specific and sensitive for monitoring RB gene inactivation as demonstrated by screening several osteosarcoma and synovial sarcoma cell lines. Of nine cell lines examined, three expressed no immunoprecipitable normal RB protein. DNA rearrangement and abnormal RB mRNA were detected in two of these three cell lines, whereas RB protein was absent from one synovial sarcoma cell line in which normal-sized RB mRNA was clearly present. Therefore, direct immunoprecipitation of RB protein can reveal RB gene mutations that are undetectable by DNA and mRNA analysis. These results further support a crucial role for the RB gene in the oncogenesis of some mesenchymal tumors.

Amino Acid Sequence↗

PubMed1989

Immunomagnetic removal of B-lymphoma cells using a novel mono-sized magnetizable polymer bead, M-280, in conjunction with primary IgM and IgG antibodies.

The efficacy of a novel monosized and magnetizable polymer bead, denoted M-280, in immunomagnetic removal of Rael B-lymphoma cells was compared with that of M-450 beads, previously used in bone marrow purging. The M-280 beads which are smaller (diameter 2.8 microns) and contain less iron than the M-450 beads were coated with polyclonal IgG sheep antimouse (SAM) antibody. The two types of immunobeads were equally efficacious when used together with the mouse monoclonal IgG antibodies HH1 or FN1, giving tumor cell depletions of about 3 logs in one cycle of operation. However, when used together with the primary IgM monoclonal antibodies (MoAbs) AB1 or HH2, the new immunobeads were significantly more efficacious than the M-450 immunobeads. To elucidate the underlying mechanism flow cytometric studies and measurements of the binding of the labeled primary MoAbs to the cellular antigens as well as to the immunobeads were carried out. Competition experiments showed that in the case of IgG MoAbs, the SAM beads bind predominantly to the Fc portion, whereas in the case of the IgM MoAbs, the Fab part plays a relatively greater role in the binding. The results indicate that if M-280 immunobeads are used, IgM MoAbs may profitably be included in antibody cocktails together with IgG antibodies in immunomagnetic purging of B-lymphoma cells. They suggest that in the case of cell bound MoAbs, the epitopes on IgG are more accessible to SAM beads than those of surface bound IgM molecules.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗

PubMed1988

Successful clinical use of an anti-HLA-DR monoclonal antibody for autologous bone marrow transplantation.

It has been widely assumed that anti-HLA-DR antibodies react with pluripotent stem cells and cannot be used in bone marrow purging. We report a case of non-Hodgkin's lymphoma in which an anti-HLA-DR antibody (AB4) was used for immunomagnetic purging and the subsequent autologous bone marrow transplantation resulted in rapid marrow engraftment with no serious complications. The results indicate that the AB4 antibody, which binds to an antigen encoded by the B3 gene of the DR region, can be safely used in the clinic in the purging of bone marrow from patients with AB4-positive tumors (non-T-cell acute lymphocytic leukemia, non-Hodgkin's lymphoma, and some cases of acute myelogenous leukemia.

Adult↗

PubMed1988

Kinetics of uptake and degradation of an abrin immunotoxin by melanoma cells and studies of the rates of cellular intoxication.

The mechanism of action of an abrin 9.2.27 antimelanoma antibody conjugate has been studied in 2 human melanoma cell lines, FEMX and LOX, which differ in sensitivity to the immunotoxin (IT) and to native abrin. The IT, which had been affinity purified before use to remove molecules with exposed gal-binding sites on the toxin B-chain, inhibited cellular protein synthesis at a faster rate in the LOX than in the FEMX cells despite the fact that the LOX cells express less specific antigen and bind less IT to the cell surface. Surface-bound abrin-IT, as well as surface-bound specific antibody, disappeared at equal rates from the cell surface of the 2 cell lines. After binding of labelled IT the disappearance of total cell-associated radioactivity, as well as the appearance of TCA-precipitable and TCA-soluble radioactivity in the incubation medium, occurred at faster rates in the LOX than in the FEMX cells. No free abrin or antibody B-chain complex could be detected in the medium or inside the cells. The results indicate that the different sensitivities of the melanoma cell lines reflect different abilities to process endocytosed IT and to translocate the active A-chain to the cytosol. Experiments carried out in the presence of lactose are interpreted to mean that the A-chain may be translocated to the cytosol by two mechanisms, one involving antigen-antibody interaction and one involving the B-chain, and that the lectin binding site contributes to the B-chain-facilitated mechanism.

Abrin↗

PubMed1988

Expression and characteristics of a novel human osteosarcoma-associated cell surface antigen.

The characteristics of a new osteosarcoma-associated cell surface antigen were studied by means of two murine monoclonal antibodies, TP-1 and TP-3, which were found to bind to two different epitopes on the same antigen, a monomeric polypeptide with a molecular weight of approximately 80,000. Immunohistochemical studies showed that the antigen was present in all osteogenic sarcomas tested, in most cases of malignant fibrous histiocytoma, in two malignant hemangiopericytomas and in a few synovial sarcomas, but not in other main groups of sarcomas and nonsarcomatous malignancies. In normal tissues it was detected only in clusters of cells in the adrenal medulla and in proximal kidney tubules. Also endothelial cells in proliferating capillaries in placenta and in most tumors were stained. The antigen was absent in resting but present in actively proliferating osteoblastic cells. The epitopes were resistant to proteolytic and sugar-cleaving enzymes but sensitive to high temperatures and could not be detected in paraffin-embedded specimens. The tissue distribution and properties of the antigen show that it is different from the sarcoma-associated antigens previously studied. In contrast to previous findings with three other anti-sarcoma monoclonal antibodies, no correlation was found between serum alkaline phosphatase activity and the amount of TP-binding substances in the same sera. Nevertheless, an apparently complex association between alkaline phosphatase and the TP-binding antigen seems to exist. Thus, the Mr 80,000 antigen extracted from an osteosarcoma cell line showed enzyme activity, whereas TP-binding molecules precipitated from patient sera contained alkaline phosphatase activity only in a few of the cases studied. Altogether our data suggest that the antigen defined by the TP antibodies may be a marker of osteoblastic differentiation. The pattern of antigen expression in malignant tumors is unique, inasmuch as the antigen is found selectively in sarcomas and in all 31 osteosarcomas tested.

Adrenal Medulla↗

PubMed1988

Extrapulmonary, tissue-specific metastasis formation in nude mice injected with FEMX-I human melanoma cells.

FEMX-I human malignant melanoma cells, originating from a lymph node metastasis in a patient, uniquely and selectively produced extrapulmonary metastases after i.v. injection of cells prepared from xenografts into adult, nude mice. After a lag time of approximately 50 days, metastases were observed in s.c. sites at the back and front of the neck, and in axilla and inguinal regions. Tumor colony formation in lungs were never detected. The interscapular tumors showed a close relationship to brown fat, partly infiltrating this tissue, whereas the other s.c. tumors seemed to be localized to lymph nodes. Mesenterial and mediastinal lymph node metastases were frequently found, together with retroperitoneal tumors along the spine. The normal cells of the adrenal medulla were often replaced by melanoma cells, whereas the cortical tissue was not affected. The conclusion that FEMX-I cells possess an inherent ability for tissue-specific metastasis formation is supported by the metastatic pattern seen after i.p. and intrasplenic injection, as well as after inoculation of the cells in the footpads of the mice. The relatively slowly growing FEMX-I tumors showed the same differentiated morphology as the patient's tumor, independent of the site of growth and the number of passages in the animals. The FEMX-I tumor was easily established as a cell line in vitro. Such cells showed a strongly reduced metastatic capacity, indicating that the in vitro growth conditions had induced alterations in the FEMX-I cells influencing their ability to form site-specific metastases, changes that were shown to be reversible. It is suggested that structures on the surface of the tumor cells, as well as growth factors in the host tissues, may be of importance for the observed tissue specificity. The FEMX-I melanoma, which, as a human tumor in nude mice, has a unique metastatic pattern, offers possibilities for investigating mechanisms involved in site-specific metastasis formation, as well as for testing effects of antimetastatic, chemotherapeutic, and immunotherapeutic agents against human extrapulmonary micro- and macrometastases.

Animals↗

PubMed1988

New indirect approach to the therapeutic use of immunotoxins.

To improve the applicability of immunotoxins (ITs), we have developed a new two-step indirect procedure. The target cells to be killed are first incubated with cell-specific mouse monoclonal antibodies (MAbs). After removal of excess unbound antibody, the cells are incubated in the presence of lactose with an indirect IT, a conjugate of whole abrin and sheep anti-mouse immunoglobulin (SAM) that binds only to cells having primary mouse MAbs on their surfaces. The SAM-abrin IT is affinity purified before use to remove molecules with exposed B-chain-binding sites; it was nontoxic in the absence of the specific mouse MAbs, demonstrating the specificity of the two-step method. We compared the indirect approach, using four different primary MAbs, with the conventional method, in which abrin is coupled directly to the mouse MAbs. In three human cell lines--the melanoma line FEMX, the Burkitt cell line Rael, and the leukemia cell line KM3--the cell kill, measured by a clonogenic assay, was consistently greater with the indirect than with the direct method. In the melanoma and Rael cells, the indirect method gave a higher cell kill than even native abrin. With a mixture of two different antibodies an additive effect was observed with the indirect but not with the direct method. The new approach greatly simplifies the therapeutic application in vitro of ITs, because it permits the use of different primary antibodies, singly or in mixtures, in conjunction with only one or a few general indirect ITs. In efforts to further improve the usefulness of the indirect method, other indirect ITs containing different toxin moieties are being examined. The possibility of employing the indirect principle in vivo is being explored.

Abrin↗

PubMed1988

A new experimental metastasis model in athymic nude mice, the human malignant melanoma LOX.

The human tumor line LOX was established as an s.c. xenograft in nude mice from a lymph-node metastasis of a patient with malignant melanoma. I.v. injection into adult nude mice of single-cell suspensions prepared from xenografts resulted in progressively growing lung tumor colonies that killed the animals. No difference in colony formation was seen between cells taken from lung colonies and s.c. xenografts. An in vitro cell line, LOX-L, was established from lung colonies, and the monolayer cells, detached with EDTA, retained the same ability to form experimental lung metastases. In a total of 14 experiments, 82 of 89 mice receiving 1 X 10(6) viable tumor cells died with a mean survival time of 34.1 +/- 4.8 days. Long-term passaging in vivo and in vitro did not result in any alteration of the lung-colonizing potential of the LOX cells, whereas trypsinization of the cells before i.v. injection reduced lung colony formation. The life span was inversely related to the number of LOX cells injected, permitting estimation of the cell kill caused by chemotherapy. Mice injected i.v. with the LOX cells showed the same relative response to cis-diamminedichloroplatinum (CDDP) and mitozolomide (MZA) as did animals carrying s.c. xenografts. The LOX cells have shown a remarkable stability and similarity to the cells of the patient's tumor with respect to morphology, karyotype and chemosensitivity. The LOX model may be useful for testing effects of therapy on lung micro- and macrometastases, and the activity of antimetastatic agents, as well as for studying mechanisms involved in the metastatic process.

Animals↗

PubMed1988

Sodium thiosulfate fails to increase the therapeutic index of intravenously administered cis-diamminedichloroplatinum (II) in mice bearing murine and human tumors.

Intravenous (i.v.) administration of sodium thiosulfate reduces the toxicity of cis-diamminedichloroplatinum (II) (CDDP). This effect, which allows the use of increased CDDP doses, has been exploited clinically in the intraperitoneal (i.p.) treatment of intraabdominal tumors. Recently, attempts have been made to treat extraperitoneal tumors by concurrent i.v. administration of CDDP and sodium thiosulfate. We have tested this approach in mice bearing systemic L1210 leukemia, s.c. growing Lewis lung carcinoma, C3H mammary carcinoma, and a human sarcoma growing in athymic nude mice. In all cases the antitumor activity of CDDP was substantially reduced in a manner dependent on the thiosulfate dose. Increased doses of CDDP, permitted by reduced toxicity in the presence of thiosulfate, raised the antitumor activity. However, the latter did not exceed that obtained by much lower doses in the absence of thiosulfate. The present experiments in animal models thus fail to support the clinical use of CDDP given i.v. together with its antidote, sodium thiosulfate.

Animals↗

PubMed1988

Preclinical phase II studies in human tumor lines: a European multicenter study.

In an attempt to increase the predictability and to extend the differential capacity of the anticancer drug development program the American National Cancer Institute has recently proposed the introduction of a screening system consisting of human tumor cell lines to select drugs in a disease-oriented fashion rather than by the previously applied drug-oriented strategy. Although this new approach offers great advantages, assay limitations can be identified in testing unknown compounds for antitumor activity in vitro. Human tumor xenografts grown in nude mice may play an additional role in the prediction of clinical activity and the assessment of the spectrum of activity of potential anticancer drugs, because they have a better relationship with the clinical situation of cancer treatment. In a European multicenter collaboration it has been proposed to use panels of human tumor lines from solid tumor types to study: the antitumor activity of three different drugs per tumor type; the reliability of 'preclinical' phase II studies by comparison of the obtained data with results of phase II clinical trials; the feasibility of this joint project, such as the methodology, the reproducibility of experimental data and the introduction of uniform activity criteria. If preclinical phase II studies in human tumor lines generate reliable results, this in vivo screening system will create a unique possibility to better identify promising clinical candidate compounds or analogs of conventional cytostatic agents as well as those tumor types likely to respond to the selected investigational drugs.

Amsacrine↗

PubMed1988

Immunomagnetic removal of B-lymphoma cells from human bone marrow: a procedure for clinical use.

B-lymphoma cells were purged from human bone marrow by incubating the cell suspension with a cocktail of three different pan-B cell mouse IgG1 monoclonal antibodies, and then with immunobeads charged with sheep anti-mouse antibody, followed by magnetic separation. The primary antibodies used, HD37 (CD19), HD6 (CD22), and HH1 (CD37), bind to a very high percentage of the cells in non-Hodgkin's lymphomas of poor prognosis. The secondary antibody is directed against the Fc portion of the IgG antibodies. In model experiments Burkitt's lymphoma cells (Rael) were admixed to mononuclear bone marrow cells in the ratio 1/9. With a ratio of immunobeads/total antibody-binding B cells of 50/1 in a first treatment cycle and repeating the procedure with the same number of beads in a second cycle, a tumor cell depletion of more than 5 logs was achieved, as judged by a clonogenic assay. The concomitant reduction of CFU-GM and CFU-GEMM was about 20%. The purging procedure has been scaled up to clinical use. Equipment suitable for purging patients' marrow specimens, employing standard transfusion facilities, is described. With this equipment the efficacy of tumor cell removal was the same as in the model experiments, and the whole magnetic separation could be completed in 2 hours.

Animals↗

PubMed1987

Studies on the mechanism of action of abrin-9.2.27 immunotoxin in human melanoma cell lines.

Previously we have shown (Godal, A. et al., J. Natl. Cancer Inst., 77: 1247-1253, 1986) that the sensitivities of different melanoma cell lines to a conjugate of abrin with the anti-melanoma antibody 9.2.27 was correlated with their sensitivities to native abrin. To elucidate the underlying mechanism we have compared the binding and toxicity of the conjugate and of native abrin to two melanoma cell lines, FEMX and LOX, which differ in sensitivity to abrin. Abrin was linked by a disulfide bond to the monoclonal antibody 9.2.27, and the conjugate was purified by affinity chromatography to remove molecules with exposed galactose-binding sites on the toxin B-chain. Lactose had no effect on the binding of the immunotoxin (IT) to the cells but nevertheless reduced strongly the toxicity to the LOX cells. The differences in sensitivity to native abrin were much larger than the concurrent differences in binding. Lactose reduced the toxicity of abrin to a far greater extent than the associated reduction in binding to the cell surface. The toxicity of the immunotoxin to the FEMX cells could be prevented by pretreatment with excess 9.2.27 antibody, whereas the more abrin-sensitive LOX cells were protected only to a limited extent. Concurrent treatment of the LOX cells with antibody and lactose acted synergistically and afforded complete protection. It is suggested that the protective effect of lactose against the IT was exerted after internalization into vesicles of IT bound unspecifically to the cell surface and that the toxic moiety of the IT, the abrin A-chain, may be translocated from endocytotic vesicles to the cytosol by two alternative mechanisms, one mediated by the antibody and a second one facilitated by the B-chain and its lectin binding site. The relative significance of these mechanisms seems to differ in different target cell lines depending on their inherent sensitivities to native abrin which in turn largely reflects the ability of the cells to internalize and process surface-bound abrin.

Abrin↗

PubMed1987

Elimination of B-lymphoma cells from human bone marrow: model experiments using monodisperse magnetic particles coated with primary monoclonal antibodies.

Conditions for removing B-lymphoma cells from human bone marrow using "immunobeads" (IBs) were investigated. The IBs were prepared by coupling monoclonal antibodies directly to a new type of monodisperse magnetic polymer particles (M 450). Two monoclonal immunoglobulin M antibodies, AB-1 (CD 19), a B-cell-specific antibody, and AB-4, an HLA-DR-specific antibody, were used. The IBs were incubated with Rael Burkitt lymphoma cells admixed to fresh, mononuclear human bone marrow cells. After incubation for 30 min at 4 degrees C, the IBs were removed using cobalt samarium magnets. The number of remaining clonogenic tumor cells was assayed by the Courtenay and Mills soft agar procedure, and the clonogenic capacity of the bone marrow progenitor cells was measured by granulocyte-monocyte and granulocyte-erythroid-monocyte-megakaryocyte assays. With a ratio of tumor cells to normal bone marrow cells of 0.1 or 0.01 and a ratio of immunobeads to tumor cells in excess of 75, a tumor cell depletion of more than 3 logs was achieved with the AB-4 IBs and slightly less with the AB-1 beads. After two consecutive cycles of purification with the AB-4 beads, no colonies were found, corresponding to more than 6 logs of purification. In the case of the AB-1 beads, 4 to 5 logs of purification were achieved. The concomitant reduction in clonogenic bone marrow progenitor cells was only 30 to 40%. Flow cytometric studies showed that the tumor cell population contained appreciable proportions of cells binding only small amounts of the antibodies used. The results indicate that the IB procedure is highly efficient and capable of removing tumor cells expressing low levels of antigen. Compared to other purging methods in use the procedure described seems to offer several advantages with respect to efficacy, speed, and simplicity. By the use of a panel of suitable antibodies the new immunobead procedure may be potentially useful in autologous bone marrow transplantation of B-lymphomas and non-T-leukemias with poor prognosis.

Antibodies, Monoclonal↗

PubMed1987

Chromosome 13 instability and esterase D expression in an osteosarcoma cell line.

In order to assess the involvement of the 13q14 region in the development of osteosarcoma, both osteosarcoma tumor cells and normal tissue from a retinoblastoma patient previously used in restriction fragment length polymorphism studies, and sarcoma cells and normal fibroblasts from other tumor patients, have been investigated with respect to esterase D (E.C. 3.1.1.1) expression and chromosome pattern. In spite of an increased number of apparently normal chromosomes #13, a 50% reduction in esterase D activity in osteosarcoma cells from the retinoblastoma patient was observed. This suggests that loss of the RB1 gene or an OSRC gene closely linked to the ESD and RB1 gene loci is involved in the development of the osteosarcoma tumor. No reduction in esterase D expression was seen in four other sarcoma cell lines.

Carboxylesterase↗