Abstract OT3-05-08: PALLAS: PALbociclib CoLlaborative Adjuvant Study: A randomized phase 3 trial of palbociclib with standard adjuvant endocrine therapy versus standard adjuvant endocrine therapy alone for HR+/HER2- early breast cancer

Background:

Cell cycle inhibition is a proven target for novel cancer therapeutics. Palbociclib (P) is an orally active inhibitor of CDK4/6, and arrests the cell cycle at the G1-S transition. P in combination with endocrine therapy (ET) has demonstrated efficacy in phase II and III randomized trials for patients with newly diagnosed and recurrent hormone receptor positive/HER2 negative (HR+/HER2-) metastatic breast cancer (MBC), and is approved in these settings. Given confirmed benefits of P and ET for MBC, the PALLAS study was designed to determine if the addition of P to adjuvant ET improves outcomes over ET alone in HR+/HER2- early breast cancer.

Trial Design:

PALLAS is an international open-label phase III trial randomizing (1:1) patients (pts) to 2 years of P (125 mg daily, 21 days on 7 days off in a 28-day cycle) combined with at least 5 years of provider choice ET (AI, tamoxifen, +/- LHRH agonist), versus ET alone. The primary objective of the study is to compare invasive disease-free survival (iDFS) for the combination of P and ET, versus ET alone. Secondary objectives include comparison of iDFS excluding cancer of non-breast origin, DRFS, LRRFS, OS, as well as safety. The principal objective of the translational investigations is to determine the predictive or prognostic utility of defined genomic subgroups with respect to iDFS and OS. Additional objectives include evaluation of cfDNA and tissue biomarkers predictive of benefit or resistance, pharmacogenomics, adherence, and patient-reported QOL. Eligible pts are pre- or post-menopausal women or men with stage II-III, HR+/HER2- breast cancer. Patients may have already initiated ET, but must be randomized within 12 months of diagnosis and 6 months of initiation of adjuvant ET. Trial sample size is 4600 pts and stage IIA pts will be capped at a total accrual of 1000 pts. Interim analyses for safety, futility/efficacy and sample size re-estimation are planned. PALLAS opened in 9/2015 and accrual is ongoing. Contact information: emayer@partners.org

Key words: palbociclib, CDK4/6 inhibition, HR+/HER2- early breast cancer, adjuvant endocrine therapy.

Citation Format: Mayer E, DeMichele A, Gnant M, Barry W, Pfeiler G, Metzger O, Burstein H, Miller K, Rastogi P, Loibl S, Goulioti T, Zardavas D, Fesl C, Koehler M, Huang-Bartlett C, Huang X, Piccart M, Winer E, Wolff A. PALLAS: PALbociclib CoLlaborative Adjuvant Study: A randomized phase 3 trial of palbociclib with standard adjuvant endocrine therapy versus standard adjuvant endocrine therapy alone for HR+/HER2- early breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT3-05-08.

Abstract P1-07-04: Physical activity, weight and outcomes in patients receiving first-line chemotherapy for metastatic breast cancer: Results from CALGB 40502 (Alliance)

Background: Obesity and inactivity are associated with an increased risk of cancer-related and overall mortality in women with early-stage breast cancer, but there are few data in advanced breast cancer.

Methods: C40502 was a Phase III trial of first-line chemotherapy for patients with metastatic breast cancer (MBC). Participants were randomized to weekly paclitaxel, nab-paclitaxel or ixabepilone. Height and weight at the time of study enrollment were abstracted from medical records. After study activation, the protocol was amended to collect physical activity (PA) data. Participants completed the Nurses' Health Study Exercise Questionnaire, indicating the frequency, type and duration of recreational PA in which they engaged at study enrollment. Metabolic equivalent (MET)-hours of weekly PA (MET-hrs/wk) were calculated using the Ainsworth Compendium. PA was dichotomized to 0-9 or 9+ MET-hrs/wk based on data in early stage breast cancer suggesting that women who engaged in > 9 MET-hrs of PA/wk had lower cancer-specific mortality. Association with clinical endpoints was evaluated using multivariate Cox proportional hazard models adjusting for treatment assignment, age, tumor hormone-receptor status, prior taxane use, disease-free interval and visceral metastases.

Results: 799 patients enrolled in C40502 between 2008 and 2011. Baseline body mass index (BMI) was available for 792 patients and PA data for 500 participants. Median follow up was 60 months. Median age was 56.7 years; 72% of patients had hormone receptor (HR)-positive cancers. Median BMI was 28.6 kg/m2 (IQR: 24.7-33.1 kg/m2). Patients engaged in a median of 3.3 MET-hrs/wk of PA (about 1 hour of moderate-intensity PA/wk) (IQR: 0.7-12.7 MET-hrs/wk). Neither BMI nor PA was significantly associated with progression-free (PFS) or overall survival (OS).

BMI and OutcomesBMI (kg/m2)N (%)PFS (months)Adj HRP valueOS (months)Adj HRP value18.5-24.9209 (26.4)10.0 (9.1-11.2)ref0.4826.1 (23.3-33.2)ref0.5425-29.9248 (31.3)9.0 (7.6-10.3)1.00 (0.83-1.22) 22.0 (20.0-25.4)1.05 (0.85-1.30) ≥30335 (42.3)8.7 (7.7-9.7)0.97 (0.81-1.17) 25.5 (23.1-29.5)0.95 (0.78-1.16) 

PA and OutcomesPA (MET-hrs/wk)N (%)PFS (months)Adj HRP valueOS (months)Adj HRP value0-9344 (68.8)7.9 (7.4-9.2)ref0.1323.6 (20.1-26.8)ref0.21>9156 (31.2)9.8 (8.9-12.0)0.86 (0.71-1.05) 27.4 (22.3-35.6)0.87 (0.70-1.08) 

There was a trend toward longer PFS and OS in patients who reported PA > 9 MET-hrs/wk vs 0-9 MET-hrs/wk, especially in individuals with HR+ cancers (median PFS 11.7 vs 9.2 months [adj HR = 0.84 (0.66-1.05)] and OS 34.0 vs 26.5 months [adj HR = 0.83 (0.66-1.05)] with PA >9 vs 0- 9 MET-hrs/wk).

Conclusions: In some of the first data looking at the relationship between lifestyle factors and outcomes in MBC, there was no relationship between BMI and PFS or OS in patients receiving first-line chemotherapy for advanced disease. A trend toward improved PFS and OS was seen in multivariate analysis in patients who reported higher levels of PA, but results were not statistically significant and could have been influenced by other patient factors. More information is needed regarding the relationship between PA and cancer outcomes, especially in patients with HR+ cancers.

Citation Format: Ligibel JA, Huebner LJ, Rugo HS, Burstein H, Toppmeyer DL, Anders CK, Ma C, Hudis CA, Winer EP, Barry WT. Physical activity, weight and outcomes in patients receiving first-line chemotherapy for metastatic breast cancer: Results from CALGB 40502 (Alliance) [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-07-04.

Abstract P5-18-03: Clinicopathological features among patients with HER2-positive breast cancer with prolonged response to trastuzumab based therapy

Background: HER2-positivity is a predictor of benefit from trastuzumab (TRZ), but fails to depict the observed interpatient variability in terms of treatment (tx) duration. In this study we described the relationship between clinicopathological features and TRZ tx duration.

Methods: A retrospective consecutive series of 343 HER2+ breast cancer (BC) patients (pts) treated with TRZ at the Dana-Farber Cancer Institute from 1999–2008 was identified. 139 pts treated with 1st line TRZ-based tx were selected for analysis. Pts who received any non-TRZ prior tx for metastatic disease were excluded. TRZ tx duration was defined as time from start of 1st line therapy to the 1st day of 2nd line therapy or death. Central nervous system (CNS) progression with TRZ maintenance was not considered change of tx. Pts were divided equally into 3 groups based on the duration of 1st line tx distribution. Short-term responders (STR) were on the 1st line tx for <7 months (m), intermediate responders (IR) 7–15m and long responders (LTR) for >15m. An additional group of extremely LTR (ELTR) was defined as being in the 90th percentile of tx duration (>37m). Descriptive analysis was performed; fisher exact test, Kruskal-Wallis and logistic regression methods were used to compare groups.

Results: Median follow-up time since metastatic diagnosis was 4 years (y) (range 0–11). Median age at diagnosis was 47y (22–83), 25% of stage I-III pts at diagnosis received adjuvant/neoadjuvant TRZ. The median disease free interval (DFI) was 20m (0–172), median number of metastatic sites was 2(1–5), 68% of pts had visceral disease. Median duration of 1st line tx was 10m (2–105). TRZ was given with CT in 86%, hormone tx in 6% and as monotherapy in 9%. 25% of pts developed CNS progression and continued tx. There were only small absolute differences for clinicopathological characteristics among STR, IR and LTR.

Gastrointestinal and Cardiovascular Safety Profiles of Neratinib Monotherapy in Patients with Advanced ErbB2-Positive Breast Cancer

Background: In a phase 2 study, oral neratinib was administered to patients (pts) with advanced breast cancer in 2 cohorts, those with prior trastuzumab treatment (prior T, n=66) and those with no prior trastuzumab treatment (no prior T, n=70). Neratinib demonstrated robust antitumor activity with objective response rates of 26% and 51%, respectively, and was generally tolerable (Burstein et al. Cancer Res 2009;69:72S). Diarrhea, all grades, occurred in 89% of total pts. Characteristics of the diarrhea and left ventricular ejection fraction (LVEF) measurements are described. Methods: Pts were required to have ErbB2 gene amplification in tumor tissue as measured by fluorescence in situ hybridization by independent assessment. Serial LVEF measurements were made with a multigated acquisition scan or echocardiogram. Pts were ineligible if baseline LVEF was <50%. Adverse events were graded based on the NCI Common Terminology Criteria, v 3.0. Pts received oral neratinib 240 mg daily. Results: Data collected by 18 Mar 2009 are reported; the median (range) duration of neratinib treatment was 4.5 (0.2-23.5) months for pts with prior T and 7.8 (0.5-24.2) months for pts with no prior T. Diarrhea, all grades occurred in 93% of the total population (prior T: 97%, no prior T: 89%); grade 3-4 diarrhea occurred in 21% of the total population (prior T: 30%, no prior T: 13%). Median times of onset were 2 and 3 days after first dose of neratinib, respectively, and median durations of diarrhea were 7 and 5 days. In study week 1, 86% and 73% of pts with prior T and no prior T, respectively, had diarrhea; this decreased to 12-14% in months 3 and 4 (Table). Diarrhea was the cause of dose interruptions in 36% of pts with prior T and 11% of pts with no prior T and of dose reductions in 30% of pts with prior T and 5% of pts with no prior T; only 1 pt (prior T) discontinued treatment due to diarrhea. Pts used anti-diarrheal medications for supportive therapy (prior T: 91%, no prior T: 67%). For LVEF measurements, there was little variation from baseline in most pts during the study. Four pts had at least 1 LVEF measurement <50% (2 of these pts had measurements within the institutional range of normal). None had congestive heart failure. One of these pts had grade 3 atrioventricular block and grade 3 bradycardia, which were considered unrelated to neratinib. Discussion: Neratinib treatment was not associated with clinically significant cardiotoxicity. Pts who developed diarrhea with neratinib monotherapy had early onset, but frequency and severity decreased with time on study. Despite the high frequency of diarrhea with neratinib treatment, it was readily managed with supportive therapy and dose interruptions and/or reductions.Time Course of Diarrhea in ErbB2-Positive Breast Cancer Patients Treated With NeratinibStudy PeriodPrior T: No. on StudyPrior T: % With Diarrhea, All Grades*Prior T: % With Diarrhea, Gr 3-4*No Prior T: No. on StudyNo Prior T: % With Diarrhea, All Grades*No Prior T: % With Diarrhea, Gr 3-4*Week 166861770737Week 2-466611170436Month 260331066152Month 34713060120Month 44312058140*For pts with multiple toxicity grades in a period, the maximum grade was reported.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5096.

Dose-dense (DD) doxorubicin and cyclophosphamide (AC) followed by weekly paclitaxel (P) with trastuzumab (T) and lapatinib (L) in HER2/neu-positive breast cancer is not feasible due to excessive diarrhea: updated results

Abstract #2108

Background: DD q 2 weekly (w) AC → P + T x 1 year (y) has an acceptable safely profile w/ congestive heart failure (CHF) rate of 1/70 pts (Dang, JCO 2008). Lapatinib (L) is effective in HER2 (+) BC. We conducted a pilot study of dd AC → w P + T + L to determine its feasibility and cardiac safety.
 Methods: Enrolled pts had HER2 (+) BC; LVEF > 50%. Rx consisted of AC at 60/600 mg/m2 x 4 q 2 w (w/ pegfilgrastim 6 mg day 2) → P at 80 mg/m2 x 12 q w + T x 1 y; L (1000 mg daily beginning w/ P + T and continued x 1 y). MUGA is obtained at baseline and at months (mo) 2, 6, 9, and 18. Rx is considered feasible if 1) > 80% pts can complete the PTL phase without a dose delay or reduction and 2) the cardiac event rate (CHF or cardiac death) is < 4%. Pts can remain on-Rx w/ one dose reduction of L (1000 mg → 750 mg) for a G 3 event or < G 3 toxicity (unacceptable).
 Results: From March 2007 to April 2008, we enrolled 95 pts. Median (med) age was 45 years (range, 28-73). At a med follow-up of 7 months, 90 are evaluable. Of the 90 pts, 34 (37%) withdrew from study during the PTL phase; 29 for a 2nd event of G 3 or unacceptable < G 3 toxicities (15 G 3 diarrhea, 4 G 1/2 diarrhea, 1 G 3 rash, 2 G 2 rash, 1 G 3 dyspnea and also had G 3 diarrhea, 1 G 3 ↑QTc also had G 3 diarrhea, 1 G 3 ↑ALT also had G 3 diarrhea, 1 G 3 paronychia, 1 G 3 pneumonitis, 1 asymptomatic LVEF ↓, 1 myocarditis) and 5 for other reasons (2 personal reason, 1 PCP pneumonia, 1 progression, 1 P hypersensitivity). Overall, 25/90 (27%) pts had G 3 diarrhea and 31/90 (34%) pts required a dose reduction of lapatinib. Med LVEF at baseline is 67% (N=95), at mo 2 is 68% (N=90), at mo 6 is 65% (N=53), and mo 9 is 65% (N=28). To date there are no patient drop-outs due to significant LVEF declines after dd AC; one patient dropped during PTL out due to an asymptomatic LVEF decline.
 Discussion: L at 1000 mg/day is not feasible combined w/ weekly P and T by protocol stipulation (> 20% pts required L dose reduction) primarily due to excessive G 3 diarrhea. These results have led to the modification of Design 2 (Arm D) of ALTTO. We will report updated results.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2108.

Second consensus on medical treatment of metastatic breast cancer

The present consensus manuscript defines evidence-based recommendations for state-of-the-art treatment of metastatic breast cancer depending on disease-associated and biologic variables.

Gene therapy for rheumatoid arthritis

Gene therapy was initially conceived of as a means of replacing defective genes in monogenic disorders such as cystic fibrosis or hemophilia, but has rapidly progressed into areas of medicine that involve a wide range of diseases including cancer, neurodegenerative disorders and autoimmunity. Elucidation of some of the cellular and molecular mechanisms implicated in the pathogenesis of joint inflammation and cartilage and bone destruction in inflammatory joint diseases such as rheumatoid arthritis (RA) have revealed novel targets for gene therapy. Strategies include the inhibition of pro-inflammatory cytokines, blockade of cartilage-degrading enzymes, inhibition of synovial cell activation or apoptosis of synovial cells, and manipulation of the Th1-Th2 cytokine balance. Both viral and non-viral gene transfer vector systems have been used to deliver therapeutic genes systemically or directly to arthritic joints by ex vivo as well as in vivo administration. Animal models of RA have been essential not only for better understanding the mechanisms of RA but also in serving as basic experimental tools to evaluate candidate gene products with anti-arthritic properties and develop therapeutic strategies.

Mutational analysis of the substrate binding pockets of the Rous sarcoma virus and human immunodeficiency virus-1 proteases

Mutations, designed by analysis of the crystal structures of Rous sarcoma virus (RSV) and human immunodeficiency virus type 1 (HIV-1) protease (PR), were introduced into the substrate binding pocket of RSV PR. The mutations substituted nonconserved residues of RSV PR, located within 10 A of the substrate, for those in structurally equivalent positions of HIV-1 PR. Changes in the activity of purified mutants were detected in vitro by following cleavage of synthetic peptides representing wild-type and modified RSV and HIV-1 gag and pol polyprotein cleavage sites. Substituting threonine for valine 104 (V104T), S107N, I44V, Q63M or deletion of residues 61-63 produced enzymes that were 2.5-7-fold more active than the wild type RSV PR. Substituting I42D, M73V, and A100L produced enzymes with lower activity, whereas a mutant that included both M73V and A100L was as active as wild type. Several substitutions altered the specificity for substrate. These include I42D and I44V, which contribute to the S2 and S2' subsites. These proteins exhibited HIV-1 PR specificity for P2- or P2'-modified peptide substrates but unchanged specificity with P4-, P3-, P1-, P1'-, and P3'-modified substrates. Changes in specificity in the S4 subsite were detected by deletion of residues 61-63. These results confirm the hypothesis that the subsites of the substrate binding pocket of the retroviral protease are capable of acting independently in the selection of substrate amino acids.

Proteolysis in the maturation of avian retroviruses does not require calcium

After budding from the plasma membrane, retrovirus particles undergo a process of maturation, which includes changes in morphology caused by several proteolytic cleavages of the precursor of the internal structural proteins, products of the gag gene. Cleavage is mediated by the viral protease, PR. The fact that in most systems cleavage appears to occur only after assembly is complete, suggests that PR may become enzymatically active as a consequence of release of the virion from the cell. Using avian leukosis virus as a model system, we tested the hypothesis that leakage of calcium ions into newly budded virions plays a role in their maturation. We found that in both quail Qt35 cells and monkey COS-1 cells, maturation occurred normally in calcium-free medium and in the presence of EGTA. A calcium ionophore also did not affect maturation. We conclude that calcium influx does not act as a trigger for PR-mediated maturation.

Mutations that alter the activity of the Rous sarcoma virus protease

Mutations designed by analysis of the Rous sarcoma virus (RSV) and human immunodeficiency virus (HIV)-1 protease (PR) crystal structures were introduced into 1) the substrate binding pocket, 2) the substrate enclosing "flaps," and 3) surface loops of RSV PR. Each mutant PR was expressed in Escherichia coli. Changes in activity were detected by following cleavage of a truncated (NC-PR) precursor polypeptide in E. coli and cleavage of synthetic peptide substrates representing RSV and HIV-1 PR cleavage sites in vitro. Mutations in the substrate binding pocket exchanged amino acid residues located close to the substrate in the HIV-1 PR for structurally equivalent residues in the RSV PR. Changing histidine 65 to glycine (H65G) gave an inactive enzyme, while a double mutant R105P,G106V, as well as the triple mutant, H65G,R105P,G106V, produced enzymes which showed significant activity toward a substrate that represented a HIV-1 cleavage site. Mutating the catalytic aspartate (D37S) or an adjacent conserved alanine to threonine (A40T), produced inactive enzymes. In contrast, the substitution A40S was active, but showed a reduced rate of catalysis. Mutations in the flaps of conserved glycines (G69L, G70L) produced inactive PRs. Two extended RSV PR surface loops were shortened to the size found in HIV-1 PR and resulted in drastically reduced activity. These results have confirmed some of the basic predictions made from structural models but have also revealed unexpected roles and interactions in the protein.

Analysis of substrate interactions of the Rous sarcoma virus wild type and mutant proteases and human immunodeficiency virus-1 protease using a set of systematically altered peptide substrates

In the preceding study, mutant Rous sarcoma virus (RSV) proteases are described in which three amino acids found in the human immunodeficiency virus-1 (HIV-1) protease (PR) were substituted into structurally comparable positions (Grinde, B., Cameron, C.E., Leis, J., Weber, I., Wlodawer, A., Burstein, H., Bizub, D., and Skalka, A. M. (1992) J. Biol. Chem. 267, 9481-9490). In this report, the activity of the wild type and these mutant PRs are compared using a set of RSV NC-PR peptide substrates with single amino acid substitutions in each of the P4 to P3' positions. With most substrates, the relative activities of the two active mutants followed that of the RSV PR. Substitutions in the P1 and P1' positions were an exception; in this case, the mutants behaved more like the HIV-1 PR. These results confirm predictions from structural analyses which indicate that residues 105 and 106 of the RSV PR are important in forming the S1 and S1' binding subsites. These results, further analyzed with the aid of computer modeling of the RSV PR with different substrates, provide an explanation for why only partial HIV-1 PR-like behavior was introduced into the above RSV PR mutants.

Processing of avian retroviral gag polyprotein precursors is blocked by a mutation at the NC-PR cleavage site

The avian sarcoma and leukosis viruses (ASLV) encode a protease (PR) at the C terminus of gag which in vivo catalyzes the processing of both gag and gag-pol precursors. The studies reported here were undertaken to determine whether PR is able to cleave these polyproteins while it is still part of the gag precursor or whether the release of its N terminus to form free PR is necessary for full proteolytic activity. To address this question, we created a mutation that disrupts the PR cleavage site between the NC and PR coding regions of the gag gene. This mutation was introduced into a eukaryotic vector that expresses only the gag precursor and into an otherwise infectious clone of ASLV that carries the neo gene as a selectable marker. These constructs were expressed in monkey COS cells or in quail QT35 cells, respectively. Processing was impaired in both systems. Mutant particles were formed, but they contained no mature processed gag proteins. We observed only the uncleaved gag precursor polypeptide Pr76 in one case or Pr76 and a cleaved product of about 60 kDa in the other. Processing of the mutant gag precursor could be complemented in trans by from a wild-type construct, suggesting that the mutation did not induce gross structural alterations in its precursor. Our results suggest that the PR first must be released from its precursor before it can attack other sites in the gag and gag-pol polyproteins and that cleavage at the NC-PR boundary is a prerequisite for the initiation of the PR-directed processing.

Assembly and processing of avian retroviral gag polyproteins containing linked protease dimers

Assembly and maturation of retroviral particles requires the aggregation and controlled proteolytic cleavage of polyprotein core precursors by a precursor-encoded protease (PR). Active, mature retroviral PR is a dimer, and the accumulation of precursors at sites of assembly may facilitate subunit interaction and subsequent activation of this enzyme. In addition, it has been suggested that cellular cytoplasmic components act as inhibitors of PR activity, so that processing is delayed until the nascent virions leave this compartment and separate from the surface of host cells. To investigate the mechanisms that control PR activity during virus assembly, we studied the in vivo processing of retroviral gag precursors that contain tandemly linked PR subunits in which dimerization is concentration independent. Sequences encoding four different linked protease dimers were independently joined to the end of the Rous sarcoma virus (RSV) gag gene in a simian virus 40-based plasmid vector which expresses a myristoylated gag precursor upon transfection of COS-1 cells. Three of these plasmids produced gag precursors that were incorporated into viruslike particles and proteolytically cleaved by the dimers to mature core proteins that were indistinguishable from the processed products of wild-type gag. The amount of viral gag protein that was assembled and packaged in these transfections was inversely related to the relative proteolytic activities of the linked PR dimers. The fourth gag precursor, which contained the most active linked PR dimer, underwent rapid intracellular processing and did not form viruslike particles. In the absence of the plasma membrane targeting signal, processing of all four linked PR dimer-containing gag precursors was completed entirely within the cell. From these results, we conclude that the delay in polyprotein core precursor processing that occurs during normal virion assembly does not depend on a cytoplasmic inhibitor of PR activity. We suggest that dimer formation is not only necessary but may be sufficient for the initiation of PR-directed maturation of gag and gag-pol precursors.

Unique sequences in the env gene of avian hemangioma retrovirus are responsible for cytotoxicity and endothelial cell perturbation

An avian retrovirus isolated from spontaneous cavernous hemangiomas of layer hens codes for an env protein that induces a cytopathic effect on a wide variety of cultured avian and mammalian cells and also causes thrombogenicity of endothelial cells. Sequence analysis of the avian hemangioma inducing virus revealed unique elements in both its env gene and its LTR. We propose that these elements are responsible for the biological and pathogenic characteristics of the virus.

Envelope glycoprotein of avian hemangioma retrovirus induces a thrombogenic surface on human and bovine endothelial cells

Vascular endothelial cells are a target for blood-borne pathogens which may affect their integrity and thromboresistant properties. Here, we report that cultured bovine and human endothelial cells lose their thromboresistance following interaction with the avian hemangioma-inducing retrovirus. We show that the envelope (env) gene product, glycoprotein 85, is responsible for this effect, which appears soon after infection without viral replication or cell transformation. Induction of thrombogenicity is associated with a reduction in prostacyclin release and increased expression of tissue factor. These observations may explain the occurrence of thrombosis frequently observed in association with the hemangiosarcomas induced by avian hemangioma-inducing retrovirus. These unique endothelial cell-virus interactions may also be a model for the pathogenesis of various vascular diseases.

Cytocidal effect caused by the envelope glycoprotein of a newly isolated avian hemangioma-inducing retrovirus

We isolated a field strain of avian hemangioma retrovirus (AHV) which induces a cytopathic effect (CPE) on cultured avian and mammalian cells shortly after infection. The kinetics of cell killing were dependent on the multiplicity of infection. The CPE on avian and mammalian cells was independent of virus replication, because UV-irradiated virus led to cell death as well. Biochemical and genetic experiments indicated that AHV env gene products were responsible for the CPE. Partially purified AHV envelope glycoproteins (gp85), but not those of the Rous sarcoma virus Prague C strain, induced a CPE. Rous-associated virus type 1, in which the env region was replaced by the AHV gp85 region, induced a CPE on avian and mammalian cultured cells. Therefore, we suggest that CPE is induced by AHV via interaction between viral gp85 and the cell membrane. This mode of CPE is unique among avian sarcoma-leukemia viruses.

The human beta-interferon gene enhancer is under negative control

The human beta-interferon gene is regulated by an inducible enhancer element. Analysis of the effect of deletions within this element on beta-interferon transcription indicates that this enhancer is under negative control. Deletion of sequences from the 3' end of the enhancer leads to a dramatic increase in the basal level of beta-interferon mRNA and a decrease in the induction ratio. The remaining 5' region of the enhancer can act as a strong constitutive transcription element, and it shares considerable homology with sequences known to be required for the activity of constitutive viral enhancers. We conclude that the beta-interferon enhancer consists of a constitutive transcription element and a negative regulatory sequence that prevents enhancer activity prior to induction. Thus, derepression of a constitutive transcription element appears to play a key role in the control of human beta-interferon gene expression.

Gonococcal endocarditis during pregnancy: simultaneous cesarean section and aortic valve surgery

Gonococcal endocarditis is a rare and potentially fatal consequence of disseminated gonococcal infection. Presented is the first known case of culture-proved gonococcal and serratia endocarditis in pregnancy. The case was further complicated by fetal distress at 30 weeks' gestation as a result of maternal decompensation from worsening congestive heart failure secondary to rapid destruction of her aortic valve. Consequently, cardiopulmonary bypass with subsequent aortic valve replacement and implantation of a left ventriculoaortic shunt was initiated immediately after an emergency cesarean section.