Antitumor activity and toxicity in animals of RR-150 (7-cysteaminomitosane), a new mitomycin derivative.

The experimental antitumor activity of a new mitomycin derivative, 7-cysteaminomitosane (RR-150), was evaluated in mice. When administered i.p. to mice bearing i.p.-implanted tumors, RR-150 was superior to mitomycin C (MMC) in increasing the life span of animals bearing P388 leukemia, B16 melanoma, and a line of L1210 leukemia partially resistant to MMC. RR-150 appeared comparable to MMC in increasing life span of mice bearing Madison 109 lung carcinoma, Colon 26 carcinoma, or parental (nonresistant) L1210 leukemia. Mice immunosuppressed with 550 rads whole-body irradiation prior to i.p. implantation of B16 still benefited (e.g., 40% cure rate) following optimal RR-150 therapy when compared to nonirradiated, B16-implanted mice given RR-150 (e.g., 70% cure rate). RR-150 had inconsistent activity in the treatment of s.c.-implanted tumors. In toxicity evaluations, RR-150 was comparable to MMC in suppression of total while blood cell counts but appeared to be less neutropenic. RR-150 also caused less cumulative leukopenia than did MMC in a weekly chronic dose experiment. Based on serum chemistries, RR-150 did not have significant nephrotoxicity, but there was evidence of possible liver toxicity at doses near the 50% lethal dose. Because of the balance of favorable antitumor and toxicity properties of RR-150, work is under way to prepare a more bioavailable form for advanced evaluation.

Animal models for evaluating the myelosuppressive effects of cancer chemotherapeutic agents.

An important objective of new anticancer drug discovery programs is identification of agents that are less myelosuppressive than those currently available. We have developed several animal models to evaluate these drugs for myelosuppression. Our screening model measures changes in neutrophil counts in mice as an indicator of myelosuppression. This model correctly predicted the myelosuppressive effects of 13 (76%) of 17 known agents. Cisplatin, carboplatin, spiroplatin, and marcellomycin caused no reduction in the neutrophil counts, representing four (24%) of 17 false negatives. Our secondary evaluation system is the more labor-intensive murine CFU-C assay on femoral bone marrow cells from drug-treated mice. Known myelosuppressive drugs such as mitomycin C, doxorubicin, and BCNU, as well as the false negatives from the mouse neutropenia model (cisplatin, carboplatin, spiroplatin, and marcellomycin) caused marked inhibition of colony formation 24 h after dosing; bleomycin was inactive. Advanced evaluations are performed using ferrets in which neutrophil counts can be monitored in the same animal for 28 days after treatment. Mitomycin C, doxorubicin, and BCNU caused significant reductions in the neutrophil counts whereas bleomycin had no effect. Importantly, cisplatin and marcellomycin also caused significant reductions in the neutrophil counts. Although the mouse neutropenia model is a rapid assay, there is potential for false-negative predictions. It is important that other test systems be used for more advanced evaluation of drugs identified by this model as being less myelosuppressive than reference drugs. The mouse CFU-C and ferret hematology models are suitable for this purpose in that they can identify the false-negative predictions as well as identify less myelosuppressive drugs such as bleomycin.

High insulin-like growth factor 1 (IGF-1) and insulin concentrations trigger apoptosis in the mouse blastocyst via down-regulation of the IGF-1 receptor.

Women with polycystic ovary syndrome have significantly higher rates of pregnancy loss, as well as elevated insulin and IGF-1 levels. In this study, preimplantation embryos exposed to high concentrations of IGF-1 or insulin undergo extensive apoptosis of the ICM nuclei. Lack of BAX expression, the caspase inhibitor, zVAD, or the ceramide synthase inhibitor, fumonisin B1, prevents this event, suggesting involvement of programmed cell death effector pathways. In other systems, the IGF-1 concentration regulates IGF-1R expression and thus high concentrations lead to down-regulation of the receptor. Here, data show a decrease in IGF-1 receptor protein expression, both by confocal immunofluorescent microscopy and by Western analysis upon exposure to 130 nM IGF-1. Insulin-stimulated glucose uptake, an event regulated via the IGF-1 receptor, is decreased upon exposure to excess IGF-1, suggesting decreased function of the receptor. The data also show that, by blocking receptor signal transduction or by decreasing receptor expression, the apoptotic event can be recreated, thus strongly suggesting that the mechanism of high IGF-1 induced apoptosis is decreased downstream IGF-1 receptor signaling. This embryotoxic insult by high IGF-1 levels may be responsible for the high incidence of pregnancy loss seen in women with polycystic ovary syndrome.

Tallysomycin S10b: experimental antitumor activity and toxicity.

Tallysomycin S10b (TLM S10b), a structural analog of bleomycin (BLM), was evaluated and compared with BLM for antitumor activity in several murine tumor systems and for toxic effects in mice and rats. Neither TLM S10b nor BLM was effective against IP P388 and L1210 leukemias, whereas both drugs were active against IP P388/J leukemia (a BLM-sensitive subline). TLM S10b and BLM were both active against murine solid tumors, including SC B16 melanoma, IV Lewis lung carcinoma, SC Madison 109 lung carcinoma, SC CD8F1 mammary carcinoma and SC Colon 38 carcinoma. In human tumor xenograft models, TLM S10b was active against a colon tumor and had slight activity against breast and lung tumors. Compared with TLM S10b, BLM had less activity against the colon tumor, comparable activity against the breast tumor, and no effect against the lung tumor. A consensus of the antitumor data indicated that compared with BLM, TLM S10b had comparable or greater activity and was about twice as potent. TLM S10b and BLM had approximately equivalent LD50 values in mice. TLM S10b had minimal effects on WBC counts, blood urea nitrogen levels, and serum glutamic pyruvic transaminase levels in mice during the time periods monitored. These effects were comparable to or less pronounced than those of BLM. Both drugs caused dose-related increases in the whole-lung hydroxyproline content in mice, but the dose-response curves were not parallel. TLM S10b caused a larger increase than BLM at the lower doses and a smaller increase than BLM at the highest doses. In rats, TLM S10b and BLM caused comparable, significant decreases in lung mechanics; however, histopathological examination of the lungs indicated that TLM S10b caused less evidence of pulmonary toxicity than did BLM at comparable dose levels. TLM S10b was, therefore, generally comparable to BLM in causing pulmonary toxicity in mice and showed possibly less pulmonary toxicity in rats, while demonstrating approximately equivalent to four-fold greater potency, depending on the test system. It also appeared that TLM S10b caused less pulmonary toxicity than BLM in both mice and rats at doses approaching maximally tolerated levels. TLM S10b is currently undergoing phase I clinical evaluation.

Semiconstrained total elbow arthroplasty.

Diminution of elbow function may be both embarrassing and severely disabling, especially in patients with multiple arthritic joints. Over the past century, multiple techniques of soft tissue reconstruction of the elbow have been advocated. In general, they do not compare well with total elbow arthroplasty. Arthrolysis has often resulted in little improvement of elbow motion and interposition arthroplasty to instability. Synovectomy may however offer satisfactory relief of disability for the rheumatoid elbow provided that initially there is little evidence of joint destruction. The major problem with rigidly linked total elbow arthroplasty has been a high incidence of prosthetic loosening. Biomechanical analysis has shown that high moments tend to disrupt the osseousmethacrylate junction in the humoral medulary canal. Development of a semi-constrained total elbow prosthesis transfers the developed stress to the collateral soft tissues and reduces prosthetic loosening to approximately 3 per cent. This is about one-tenth of the incidence of loosening of the hinge type arthroplasty. This reduction in prosthetic loosening has been coupled with excellent gains in flexion and estension. However, improvement in forearm rotation has not been predictable, especially in elbows exhibiting preoperative fusion or fibrous ankylosis. Though the semi-counstrained total elbow has only been generally available for 3 years, a review of these results justifies its continued use for elbow reconstruction.

Relationship of pseudopod extension to chemotactic hormone-induced actin polymerization in amoeboid cells.

Aggregation-competent amoeboid cells of Dictyostelium discoideum are chemotactic toward cAMP. Video microscopy and scanning electron microscopy were used to quantitate changes in cell morphology and locomotion during uniform upshifts in the concentration of cAMP. These studies demonstrate that morphological and motile responses to cAMP are sufficiently synchronous within a cell population to allow relevant biochemical analyses to be performed on large numbers of cells. Changes in cell behavior were correlated with F-actin content by using an NBD-phallacidin binding assay. These studies demonstrate that actin polymerization occurs in two stages in response to stimulation of cells with extracellular cAMP and involves the addition of monomers to the cytochalasin D-sensitive (barbed) ends of actin filaments. The second stage of actin assembly, which peaks at 60 sec following an upshift in cAMP concentration, is temporally correlated with the growth of new pseudopods. The F-actin assembled by 60 sec is localized in these new pseudopods. These results indicate that actin polymerization may constitute one of the driving forces for pseudopod extension in amoeboid cells and that nucleation sites regulating polymerization are under the control of chemotaxis receptors.

Preimplantation exposure to high insulin-like growth factor I concentrations results in increased resorption rates in vivo.

BACKGROUND: Women with polycystic ovarian syndrome suffer increased rates of miscarriage. Elevated insulin and insulin-like growth factor I (IGF-I) concentrations have been implicated. Here, we hypothesize that the high concentrations of IGF-I result in miscarriage, represented by decreased normal pregnancy rates and increased resorption rates in a mouse model. METHODS: In-vitro studies: 2-cell embryos were cultured in either 1.3 or 130 nmol/l IGF-I; or 500 nmol/l IGF-I receptor (IGF-IR) sense and antisense oligoprobes for 72 h. Embryos were then transferred into pseudo-pregnant ICR females. In-vivo studies: IGF-I-containing slow-release pellets or mock pellets were implanted within the uterine horn in ICR female mice. For both studies, the recipient females were killed on day 14.5 and the numbers of normal implantation sites versus resorption sites were recorded. RESULTS: In-vitro studies: blastocysts cultured in low IGF-I exhibited significantly higher normal implantation rates than blastocysts cultured in high IGF-I concentrations (P < 0.01). Blastocysts cultured in IGF-IR sense oligoprobes exhibited a significantly higher normal implantation rate than blastocysts cultured in antisense oligoprobes. In-vivo studies: mice implanted with IGF-I-containing pellets exhibited significantly lower normal implantation rates as compared with mock-pellet controls (P < 0.01). CONCLUSIONS: High preimplantation IGF-I concentrations in vitro or in vivo lead to increased resorption rates in the mouse.

Enterobacter endocarditis.

Endocarditis due to Enterobacter species is very rare. We recently cared for a patient who developed E. cloacae endocarditis following mitral valve replacement with a porcine heterograft, and was successfully treated with antibiotic therapy alone. A review of the literature disclosed an additional 17 well-described cases of enterobacter endocarditis. Two-thirds of the patients had underlying cardiac disease. The mitral valve was most frequently involved (10/16 cases) with 4 of the patients having concomitant aortic valve involvement. The overall mortality rate was 44.4%. Antibiotic therapy of enterobacter endocarditis should consist of the combination of a beta-lactam antibiotic and an aminoglycoside with careful monitoring of blood cultures to assure the adequacy of therapy. Resistance of enterobacter to previously susceptible antibiotics may occur during therapy due to induction of a chromosomally-mediated beta-lactamase, necessitating a change in antimicrobial therapy. Valvular surgery is indicated for patients failing medical management.

Pulmonary toxicity studies of bleomycin and talisomycin.

The comparative pulmonary toxicity induced by bleomycin and talisomycin (former trivial name: tallysomycin A) was evaluated by measuring lung hydroxyproline content. Based on published subacute toxicity data, in which talisomycin was found to be four times as toxic as bleomycin, the following doses of each drug were given sc to BDF1 male mice twice weekly for 4 weeks: 2.5, 5, and 10 mg/kg of bleomycin and 0.625, 1.25, 2.5, and 3.75 mg/kg of talisomycin. Equivalent dose-related effects in body weight were produced by bleomycin and talisomycin at a respective dose ratio of 4:1. Similarly, equivalent dose-dependent increases in lung hydroxyproline content, an index of collagen, were produced by bleomycin and talisomycin. Neither drug caused deaths at the doses used.

Myocardial infarction in a patient with factor XI deficiency and a lupus anticoagulant.

A 64-year-old man with both Factor XI deficiency and a lupus anticoagulant who suffered two myocardial infarctions within a 3-month period is described. Although thromboembolic disorders, including myocardial infarction, have been associated with the antiphospholipid syndrome, myocardial infarction in patients with Factor XI deficiency is rare. The potential role of Factor XIa in fibrinolysis is discussed.