Pelvic and acetabular trauma in amateur equestrian enthusiasts - A retrospective review.

INTRODUCTION: Horse riding related accidents can present with devastating pelvic and acetabular fractures. This study examines the nature, management and treatment outcomes of severe pelvic and acetabular trauma in amateur horse riders presenting to a national tertiary referral centre. We also aim to define certain at-risk groups. METHODS: This was a retrospective descriptive cohort of all patients who were referred to the National Centre for Pelvic and Acetabular trauma resulting from horse riding accidents. All patients who were referred to the National Centre for Pelvic and Acetabular Trauma between January 2018 and July 2020 were included. Professional horse riders were excluded. Clinical and treatment outcome measures were stratified to four different mechanisms of injury: fall from horse (FFH), horse crush (HC), Horse Kick (HK) and Saddle Injury (SI). RESULTS: There were 31 equestrian related injuries referred to our centre between January 2018 and July 2020. One patient was a professional jockey and was thus excluded from the study. Eighteen were female and the mean age at referral was 37 years old. The majority of these were pelvic ring injuries (73%). Fifty per cent of patients required surgical intervention and the majority of these were male. CONCLUSION: Horse riding is a potentially dangerous recreational pursuit with significant risk of devastating injury. Pelvic and acetabular fractures secondary to horse riding are frequently associated with other injuries and the need operative intervention is common in this group. Young women and older men are higher risk groups.

Anatomical reconstruction of first ray instability hallux valgus with a medial anatomical TMTJ1 plate.

BACKGROUND: First tarsometatarsal joint (TMTJ1) arthrodesis is a powerful tool for hallux valgus correction. Past criticism of the TMTJ1 arthrodesis has focused on high non-union rates, and consequent need for delayed weightbearing as prevention. In this study we present a selection and treatment protocol to minimise non-union while allowing early weightbearing. METHODS: All TMTJ1 arthrodesis procedures for hallux valgus performed by the senior surgeon over the period June, 2016 to July, 2019 were included. An anatomically-designed, medial TMTJ1 plate and screw compression was utilised for TMTJ1 arthrodesis. The construct was augmented with synthetic intermetatarsal stabilisation. All patients were kept non-weightbearing for 2 weeks, followed by progressive weightbearing as tolerated for 4 weeks. Minimum follow-up was 1 year. RESULTS: 300 modified Lapidus procedures were performed for hallux valgus with mean IMA 17° (Range: 14-29). Mean age was 58 years, with 93% female. 284 (94%) had an Akin osteotomy, while 222 cases (74%) were associated with another forefoot procedure. Patients began progressive weight bearing as tolerated from 2 weeks. All were fully weight bearing by 8 weeks post-operatively. There was a 100% union rate in this group. Mean AOFAS Hallux MTP-IP scores rose from 59 pre-operatively to 97 post-operatively. One plate was removed due to tibialis anterior impingement. There were no recurrences at final follow-up. CONCLUSIONS: We describe a selection and treatment protocol for TMTJ1 arthrodesis for hallux valgus. This yields high union rates while allowing early weight bearing. LEVEL OF EVIDENCE: 4.

Intravitreal bevacizumab (Avastin) treatment of choroidal neovascularisation in patients with angioid streaks.

OBJECTIVE: To evaluate the safety and efficacy of intravitreal bevacizumab (Avastin) as treatment for choroidal neovascularisation (CNV) associated with angioid streaks METHODS: A non-randomised, interventional case series conducted on eyes with subfoveal CNV associated with angioid streaks. Intravitreal bevacizumab (1.25 mg in 0.05 ml) was injected into nine eyes of six patients between August 2005 and December 2007. Treatment efficacy was assessed based on pre- and post-treatment visual acuity and optical coherence tomography (OCT). RESULTS: With a mean follow-up of 19 months (range 10 to 28 months), the best corrected visual acuity improved by three or more lines in four eyes (44.4%), remained within two lines of baseline in four eyes (44.4%) and decreased by three or more lines in one eye (11.1%). Central foveal thickness (CFT) measured by OCT decreased an average of 67.7 microm (range +11 to -175 microm) with an average improvement in standardised change in macular thickening of 46.6% (range -12% to +84.5%). No injection-related complications or drug-related side effects were observed. CONCLUSIONS: Intravitreal bevacizumab for the treatment of subfoveal CNV secondary to angioid streaks mildly reduced central foveal thickness with a trend toward stabilisation of visual acuity. Additional follow-up and a larger patient cohort are needed to evaluate the long-term effects of this treatment.

Emergency department-based study of risk factors for acute injury from domestic violence against women.

STUDY OBJECTIVES: To evaluate the associations between selected socioeconomic risk factors and acute injury from domestic violence against women. METHODS: We conducted a preliminary matched case-control study to measure the association of selected predictor variables with acute injury from domestic, violence against women. Patients identified as cases were Hispanic or white female emergency department patients, 16 to 65 years of age, with acute injury sustained from physical assault by an intimate male partner. Cases were selected for inclusion in the study if they reported or admitted acute physical assault by their male partners. Controls were selected from non-case female ED patients so as to represent the base population of the cases and enhance comparability. Two controls were matched to each case. The socioeconomic predictor variables examined were the education level, employment status, history of alcohol abuse, and history of drug abuse of the male partner and the education level and cohabitation status of the female partner. RESULTS: Forty-six cases were identified and included in the study. The age range was 16 to 51 years (mean, 33 years). There were 26 (57%) Hispanic and 20 (43%) white cases. The strongest predictor for acute injury from domestic violence in these patients was a history of alcohol abuse by the male partner, as reported by the female partner (odds ratio, 12.9). The remaining predictor variables were weakly associated or not associated with domestic violence. One half of the cases stated that their male partners were intoxicated with alcohol at the time of assault. CONCLUSION: Of the socioeconomic variables examined in this preliminary study, a history of alcohol abuse by the male partner, as reported by the female partner, was the strongest predictor for acute injury from domestic violence. A large-scale, multicenter, ED-based study is needed to clarify the relation between alcohol abuse, other socioeconomic factors, and acute physical assaults against women by their intimate male partners.

Limonoids showing selective toxicity to DNA repair-deficient yeast and other constituents of Trichilia emetica.

Bioactivity-directed fractionation of the MeCOEt extract of Trichilia emetica (Meliaceae) resulted in the isolation of the limonoids nymania 1 (1), drageana 4 (3), trichilin A (4), rohituka 3 (5), and Tr-B (7) and the novel seco-A protolimonoid 8. Of these, nymania 1 and Tr-B showed selective inhibitory activity toward DNA repair-deficient yeast mutants. The isolation, structure elucidation, 13C NMR spectral assignments, and biological activities of these compounds are reported.

Bioactive and other sesquiterpenes from Chiloscyphus rivularis.

Bioassay-directed fractionation of the methyl ethyl ketone extract of Chiloscyphus rivularis yielded five new sesquiterpenes, 12-hydroxychiloscyphone (2), chiloscypha-2,7-dione (3), 12-hydroxychiloscypha-2,7-dione (4), chiloscypha-2,7,9-trione (5), and rivulalactone (6) in addition to the known sesquiterpenes, 4-hydroxyoppositan-7-one (7), chiloscyphone (1), and isointermedeol (8). The structure and stereochemistry of rivulalactone, a novel trinorsesquiterpene, was confirmed by its synthesis starting from 1. Compound 2 showed selective bioactivity in our yeast-based DNA-damaging assay and cytotoxicity to human lung carcinoma cells.

Delayed recognition and infection control for tuberculosis patients in the emergency department.

STUDY OBJECTIVE: The recent increase in tuberculosis (TB) cases may have an important effect on emergency department infection-control measures. We describe infection-control interventions for TB patients admitted through the ED and hypothesize that ED suspicion of TB is associated with more rapid isolation and treatment. DESIGN: Retrospective chart review. SETTING: The ED of a 400-bed urban, university-affiliated county hospital. PARTICIPANTS: Fifty-five patients with TB culture-positive and acid-fast bacillus stain-positive respiratory specimens who were evaluated in the ED during 1991 and 1992. RESULTS: We identified cases from the mycobacteriology log. Demographic and historical data and time elapsed before initiation of infection-control measures and TB therapy were recorded. We assessed the relationships of individual clinical findings and the ED presumptive diagnosis of TB (predictor variables) to time elapsed before isolation and therapy (outcome variables) with the log-rank test. The median time (interquartile range) from ED registration to isolation was 8 hours (range, 3 to 13 hours). An ED presumptive diagnosis of TB was made in 71% of cases and was significantly associated with shorter time elapsed before isolation (5 hours [range, 2 to 10 hours] versus 21 hours [range, 11 to 111 hours]; P < .001) and less time elapsed before therapy (12 hours [range, 9 to 22 hours] versus 128 hours [68 to 374 hours]; P < .001). We found TB exposure, radiographic changes typical of TB, absence of HIV risk factors, presence of cough, and sputum production to be associated with more rapid isolation. CONCLUSION: Among patients with active pulmonary TB in the ED, TB is often unsuspected and isolation measures are often not used. ED suspicion of TB is associated with more rapid isolation and treatment.

Comparative activity of oral and parenteral topotecan in murine tumor models: efficacy of oral topotecan.

Studies were performed using several tumor models to determine the oral efficacy of topotecan. These studies were direct comparisons of oral administration with parenteral treatment by the intravenous, intraperitoneal, or subcutaneous routes. Treatment schedules included bolus treatments at 4- or 7-day intervals and a split-dose regimen (q3hx4) repeated at 4- or 7-day intervals. On the various schedules, the maximally tolerated dose of topotecan was either equivalent to or at most 1.7-fold that of parenteral administration, indicative of excellent oral bioavailability in the mouse. Orally administered topotecan was comparable in efficacy to parenteral treatment in four of five tumor models tested (i.v. L1210 leukemia, i.v. B16 melanoma, i.v. and s.c. Lewis lung carcinoma). The M5076 reticulum cell sarcoma implanted i.p. responded to i.p. and s.c. but not to orally administered topotecan. These studies provide convincing support for the clinical evaluation of orally administered topotecan.

In vitro and in vivo effects of clinically important camptothecin analogues on multidrug-resistant cells.

The cytotoxic alkaloid camptothecin (CPT) and several of its analogues, including the clinically relevant topotecan (TPT), irinotecan (CPT-11), and 9-aminocamptothecin, were evaluated for differential cytotoxic effect and DNA damage induction in multidrug-sensitive (AuxB1) and multidrug-resistant (MDR) (CHRC5) Chinese hamster ovary cells. CPT, 10-hydroxycamptothecin, and 10,11-methylenedioxycamptothecin produced equivalent amounts of cell growth inhibition and/or DNA single-strand breakage in the two cell lines. TPT, SN-38 (the active metabolite of CPT-11), and 9-aminocamptothecin were 12-, 9-, and 10-fold, respectively, less toxic to the MDR than to the wild-type cells. These findings are consistent with differences in yields of DNA single-strand breaks produced in AuxB1 and CHRC5 cells by 2-hr incubations with the various compounds. In both assays, the resistance ratios of the topoisomerase I inhibitors were approximately one-tenth those of known MDR drugs such as vinblastine or amsacrine. Thus, cultured cells that overexpress P-glycoprotein have the potential to develop some level of cross-resistance to all three topoisomerase I inhibitors currently in the clinic. The chemical basis for cross-resistance of cultured MDR cell lines to certain CPT analogues is not yet understood, but is likely more complex than positive charge alone. TPT had a reasonable therapeutic effect on B6D2F1 female mice implanted with MDR sublines of P388 leukemia, compared with its effect on mice implanted with wild-type P388 cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics and pharmacodynamics of topotecan in patients with advanced cancer.

Topotecan, a semisynthetic water-soluble analog of camptothecin, is the first topoisomerase I-directed drug to enter clinical trial in the United States in over 20 yr. In this study, 30-min infusions of topotecan were administered daily for 5 days every 3 weeks at doses ranging from 0.5 to 2.5 mg/m2. Topotecan is reversibly hydrolyzed in a pH-dependent reaction in aqueous solutions to the ring-open hydroxy acid. The disposition of the closed ring lactone has been studied in 26 patients, and the disposition of both lactone and hydroxy acid has been studied in 12 patients. The clearance rate for topotecan lactone was 1220 ml/min/m2, with a range of 300-4760 ml/min/m2. The clearance rate for total topotecan (lactone and hydroxy acid) was 493 ml/min/m2, with a range of 163-815 ml/min/m2. A model for the disposition of lactone and hydroxy acid incorporating both reversible hydrolysis and elimination was developed. We have shown that topotecan is partially hydrolyzed prior to administration in parenteral solutions, and that clearance of the parent compound proceeds in vivo by conversion to hydroxy acid and elimination. Renal clearance accounted for 30 +/- 18% of drug elimination in patients. The relationship between topotecan dose and myelotoxicity is well fit by a sigmoidal Emax model, as is the relationship between total topotecan area under the concentration-time curve and myelotoxicity. The disposition of topotecan was also studied in mice. The clearance rate for total topotecan in mice was 330 ml/min/m2 after administration of topotecan lactone.(ABSTRACT TRUNCATED AT 250 WORDS)

Camptothecin hyper-resistant P388 cells: drug-dependent reduction in topoisomerase I content.

A subline of P388 leukemia made 10-fold resistant to camptothecin (CPT) by serial passage in drug-treated mice was adapted to growth in tissue culture and made hyper-resistant to CPT by passage in the presence of increasing concentrations of the drug. Cells were obtained that were 1,000-fold resistant to CPT, compared to wild-type P388 cells. Neither topoisomerase I mRNA nor 100 kDa topoisomerase I enzyme was detectable in these cells, and topoisomerase I activity extracted from nuclei was less than 4% of that extracted from nuclei of wild-type cells. An immunoreactive 130 kDa protein that could be an altered, inactive form of topoisomerase I was evident in the hyper-resistant cells. In addition, the cells deficient in topoisomerase I contained enhanced topoisomerase II activity. Maintenance of the hyper-resistant phenotype required continued exposure to CPT; growth in its absence led to loss of hyper-resistance, increased topoisomerase I content and activity, and decreased topoisomerase II activity. The sensitivity of the cells to killing by a number of inhibitors of topoisomerases I and II was consistent with these observations. Thus, P388 cells have the potential to become highly resistant to CPT by severely curtailing topoisomerase I expression; in these circumstances, topoisomerase I and II activities are regulated coordinately.

Synergistic cell killing by ionizing radiation and topoisomerase I inhibitor topotecan (SK&F 104864).

Topotecan (SK&F 104864), a water-soluble analogue of the topoisomerase I inhibitor camptothecin, is currently in Phase II clinical trial for solid tumors. We have characterized topotecan in terms of its effect upon gamma-radiation-induced cell killing. In colony formation experiments, subtoxic concentrations of topotecan (2 microM) potentiated radiation-induced killing of exponentially growing Chinese hamster ovary or P388 murine leukemia cultured cells. Survival curve shoulders were reduced; the slopes of the exponential portions of the curves were decreased to a small extent. D37 and D10 (radiation dose resulting in 37 and 10% survival of colony-forming ability) values were reduced by approximately 60 and 50%, respectively, in the case of Chinese hamster ovary cells. In P388 cells, topotecan reduced D37 by 35 to 40% and D10 by 20 to 25%. Potentiation of radiation-induced cell killing by topotecan was absolutely dependent upon the presence of the topoisomerase I inhibitor during the first few (less than 30) min after irradiation. Association of topoisomerase I with this effect was confirmed in studies of Chinese hamster ovary cells previously made resistant to camptothecin (and cross-resistant to topotecan), resulting in decreased cellular content of topoisomerase I. These cells were found to be 2- to 3-fold hypersensitive to gamma-radiation-induced killing. P388 camptothecin-resistant cells were further sensitized to the lethal effects of ionizing radiation by nontoxic treatment with the topoisomerase II inhibitor novobiocin, consistent with increased dependence of topoisomerase I-deficient cells upon topoisomerase II.

Noninvasive assessment of ulnar bending stiffness in women.

The load-carrying capacity of cortical bone is closely related to its geometry and to its fundamental material properties, including mineral content (BMC). Together these determine the bending stiffness EI, where I is the cross-sectional moment of inertia and E is Young's modulus of elasticity. To assess the relationship of BMC and bone width (BW) to EI in healthy women, we used mechanical response tissue analysis (MRTA), a noninvasive method that involves analysis of tissue responses to ulnar vibration. A total of 48 healthy women were enrolled into an older (64 +/- 1y, n = 25) and a younger (25 +/- 0.6y, n = 23) group. BMC and BW of the dominant ulna were measured by single-photon absorptiometry (SPA). EI was determined by MRTA. BMC (0.75 +/- 0.02 versus 0.63 +/- 0.02 g/cm), BMC/BW (0.75 +/- 0.02 versus 0.63 +/- 0.02 g/cm2), and EI (27.7 +/- 1.3 versus 21.3 +/- 1.1 N.m2) were significantly greater (p less than 0.005) in the young subjects. BW did not change with age (1.00 +/- 0.01 versus 1.01 +/- 0.01 cm). In young women, simple correlations of BMC and BW with EI were both significant. By multiple regression analysis only BW independently predicted EI (EI = -0.35 + 39.1 x BMC, R2 = 0.52). In older women BMC and BW correlated with EI, but in multiple regression only BMC was significant (EI = -34.5 + 62.1 x BW; R2 = 0.45). When this analysis of older women included only those whose BMC values were within 2 SD of the young mean, BMC remained the only significant predictor of EI.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo development and in vitro characterization of a subclone of murine P388 leukemia resistant to bis(diphenylphosphine)ethane.

Bis(diphenylphosphine)ethane (DPPE) and its gold coordination complexes have demonstrated antitumor activity in transplantable tumor models. This report describes the development of a P388 cell line (P388/DPPEc) that is resistant to DPPE and its analogues and the in vitro characterization of the cross-resistance of this subline to various antitumor and cytotoxic agents. The P388/DPPE tumor cell line was developed by serial transplantation in DPPE-treated mice. Resistance to DPPE was phenotypically stable. The P388/DPPE subline was cross-resistant to DPPE analogues and metal coordination complexes of DPPE. In addition, P388/DPPE cells were resistant to several mitochondrial uncouplers, including rhodamine-123, tetraphenylphosphonium, and carbonylcyanide-p-trifluro-methoxyphenyl hydrazone. P388/DPPE cells were less capable of sequestering and retaining 123Rh than were sensitive (P388/S) cells. Exposure to Au(DPPE)2+, a gold complex of DPPE with increased antitumor activity, resulted in a depletion of cellular ATP; the depletion was more rapid in the sensitive than the resistant cells. The rate of mitochondrial respiration, as measured by 14CO2 evolution from [6-14C]glucose, was greater in P388/S than in P388/DPPE. As with that evidenced for 123Rh, the cellular uptake of radiolabeled DPPE was decreased in P388/DPPEc cells. The results suggest that the basis for the resistance of this cell line may be an alteration in mitochondrial membrane potential. These data and the striking cross-resistance of P388/DPPE to mitochondrial uncouplers support the hypothesis that mitochondria may be one target involved in the cytotoxic or antitumor activities of these compounds. Mitochondria may also be causally related to the cytotoxic or antitumor activities, in that DPPE may be concentrated in cells via the presence of the inner mitochondrial membrane potential. Thus, P388/DPPE cells can serve as a tool to screen for and evaluate drugs that rely on affecting mitochondrial function, either mechanistically or causally, for their antitumor efficacy.

Synthesis of water-soluble (aminoalkyl)camptothecin analogues: inhibition of topoisomerase I and antitumor activity.

Water-soluble analogues of the antitumor alkaloid camptothecin (1) were prepared in which aminoalkyl groups were introduced into ring A or B. Most of the analogues were prepared by oxidation of camptothecin to 10-hydroxycamptothecin (2) followed by a Mannich reaction to give N-substituted 9-(aminomethyl)-10-hydroxycamptothecins (4-12) or by subsequent modification of Mannich product 4 (13, 15, 17, 19, 21). Others were obtained by modification of the hydroxyl group of 2 (25,26) or by total synthesis (35,42,43). These analogues, as well as some of their synthetic precursors, were evaluated for inhibition of topoisomerase I, cytotoxicity, and antitumor activity. Although there was not a quantitative correlation between these assays, compounds that inhibited topoisomerase I were also cytotoxic and demonstrated antitumor activity in vivo. Further evaluation of the most active water-soluble analogue led to the selection of 9-[(dimethylamino)methyl]-10-hydroxycamptothecin (4, SK&F 104864) for development as an antitumor agent. In addition to its water solubility, ease of synthesis from natural camptothecin, and high potency, 4 demonstrated broad-spectrum activity in preclinical tumor models and is currently undergoing Phase I clinical trials in cancer patients.

Development of a stable camptothecin-resistant subline of P388 leukemia with reduced topoisomerase I content.

A camptothecin-resistant subline of P388 leukemia (P388/CPT) was developed by repeated transplantation of P388 cells in mice treated with therapeutic doses of camptothecin. In mice bearing the resistant tumor, a maximally tolerated dose of camptothecin produced no net reduction in tumor cell burden, in contrast to a 5-log cell kill in the parental P388 (P388/S). The IC50 of camptothecin, as determined by colony formation assays of cultured cells, was 8 times greater for the cloned P388/CPT cell line than for P388/S. P388/CPT cells were not cross-resistant to other antineoplastic agents, including topoisomerase II inhibitors. The type I topoisomerases purified from P388/CPT and P388/S cells were identical with respect to molecular weight, specific activity, in vitro camptothecin sensitivity, and DNA cleavage specificity. Camptothecin induced fewer protein-associated DNA single-strand breaks in the resistant cells than in the wild-type P388 cells. Topoisomerase I mRNA, immunoreactivity, and extractable enzymatic activity were 2-4 times lower for P388/CPT cells than for P388/S cells. As resistance to camptothecin developed, topoisomerase I extractable activity decreased, concomitant with an increase in topoisomerase II extractable activity. Furthermore, the appearance of camptothecin resistance was associated with specific rearrangements of the topoisomerase I gene. These results suggest that development of resistance to inhibitors of topoisomerase I can occur by down-regulation of the target enzyme, thus reducing the production of lethal enzyme-mediated DNA damage. The enhanced topoisomerase II activity in these cells suggests that resistance to camptothecin may be overcome by co-treatment with topoisomerase II inhibitors.

Nonproductive rearrangement of DNA topoisomerase I and II genes: correlation with resistance to topoisomerase inhibitors.

Topoisomerase inhibitors comprise an important group of agents that is used in cancer treatment. Because the development of resistance to cancer chemotherapeutic agents represents a major limitation of cancer chemotherapy, we investigated the mechanism of resistance by murine P388 leukemia to camptothecin (topoisomerase I inhibitor) or amsacrine (topoisomerase II inhibitor). The resistant cells contained reduced levels of topoisomerase activity and messenger RNA. The topoisomerase gene of these cells was rearranged (only in one allele) and hypermethylated. These topoisomerase gene alterations probably resulted in reduced transcription and, thus, enzyme production, which was correlated with resistance to the topoisomerase inhibitor.

Synthesis, tubulin binding, antineoplastic evaluation, and structure-activity relationship of oncodazole analogues.

In an attempt to identify a soluble oncodazole analogue that could be easily formulated, a series of substituted oncodazoles was synthesized and evaluated for tubulin binding affinity, in vitro cytotoxicity against cultured mouse B-16 cells, and ability to prolong lifespan at the maximally tolerated dose in the P388 mouse leukemia model. Biological evaluation of all the isomeric methyloncodazoles demonstrated the thiophene 4'-position to be the only site of significant bulk tolerance, although substitution of this position with polar or charged functional groups abolished biological activity. Simple esters of the 4'-carboxymethyloncodazole were shown to have enhanced antitumor activity and tubulin binding affinity relative to oncodazole. Despite a failure of this study to identify a water-soluble oncodazole with antitumor activity, the structure-activity relationship developed led to a derivative with enhanced activity in the P388 leukemia model and facilitated the preparation of a biologically active photolabile analogue.

A murine model to evaluate the ability of in vitro clonogenic assays to predict the response to tumors in vivo.

The use of the human tumor cloning assay as a predictor of clinical response of human tumors to drugs is predicated on the hypothesis that the in vivo response of a tumor to a drug can be correlated with the in vitro response of cells derived from the tumor. To test this hypothesis, we utilized a murine tumor model in which the in vivo and in vitro responses of a tumor can be accurately and reproducibly compared. Drug activity was assessed in P388 leukemia with the standard in vivo antitumor assay (i.p. tumor/i.p. drug administration) and an in vitro assay wherein the ascites tumor cells are removed from mice, treated with a drug, and directly cloned in soft agar to measure clonogenic capacity. The response of P388 cells to analogues within four separate classes of antitumor agents, anthracyclines, anthraquinones, platinum(II) coordination complexes, and phosphinogold(I) complexes was evaluated. The clonogenic assay failed to discriminate between highly active in vivo antitumor agents and analogues with only marginal in vivo efficacy (i.e., doxorubicin and daunorubicin versus rhodomycins A and B, ametantrone versus NSC 276740, cisplatin versus transplatin, [Au(dppe)2]Cl versus [Au(depe)2]PF6. Furthermore, the in vitro clonogenic assay failed to detect carboplatin which was a highly active agent in vivo. The basis for these discrepancies was explored by a more detailed comparison of doxorubicin and rhodomycin B. In vivo or in vitro drug exposure with subsequent measurement of cell kill by the in vitro clonogenic and in vivo tumorigenic assay demonstrated that the in vitro assay overestimated the cytotoxic potency of the drugs relative to the tumorigenic assay. Treatment of tumors in vivo with doxorubicin at doses below the maximally tolerated dose in mice resulted in multiple log cell kill as measured in vitro or in vivo, whereas rhodomycin B was cytotoxic only at dose levels exceeding its maximally tolerated dose. The results indicate that a subset of tumor stem cells capable of forming colonies in soft agar are significantly more sensitive to the cytotoxic effects of anthracyclines than are in vivo tumorigenic stem cells. Cytotoxic potency as measured by an in vitro soft agar clonogenic assay is not an accurate predictor of in vivo antitumor efficacy even in a model in which ascites tumor cells are directly exposed to i.p. drug. The in vitro cytotoxicity assay is useful only as a nonselective prescreen and must be used in combination with other indicators of tumor cell selectivity and dose-limiting organ toxicity.

Biological characterization and oncogene expression in human colorectal carcinoma cell lines.

To establish well-characterized cellular reagents for the study of colon carcinoma, we have examined 19 human colorectal carcinoma cell lines with regard to morphology, ultrastructure, expression of tumor-associated antigens, proliferative capacity in vitro, anchorage-independent growth, oncogene expression, tumorigenicity and malignant potential. Cell lines examined were cultured under identical conditions, and in vitro and in vivo analyses were performed in parallel on replicate cultures. Three classes of colorectal cell lines were defined according to their tumorigenicity in nude mice. Class-1 lines formed rapidly progressing tumors in nearly all mice at an inoculum of 10(6) cells. Cell lines belonging to class-2 were less tumorigenic, producing tumors later and at a slower growth rate. Class-3 lines were non-tumorigenic under all experimental conditions tested. By Northern analysis, the oncogenes c-myc, H-ras, K-ras, N-ras, myb, fos and p53 were expressed in nearly all cell lines examined. In contrast, transcripts for abl, src and ros were not detected. The best in vitro predictor of tumorigenicity was colony formation in soft agar. There was no detectable correlation between tumorigenicity and metastatic potential, doubling time in vitro, production of tumor-associated markers, xenograft histology or expression of specific oncogenes.