Formation and repair of DNA adducts in vinyl chloride- and vinyl fluoride-induced carcinogenesis

Vinyl chloride is a known human and animal carcinogen that induces angiosarcomas of the liver. We review here studies on the formation and repair of DNA adducts associated with vinyl chloride and vinyl fluoride in exposed and control rodents and unexposed humans. These vinyl halides induce etheno (epsilon) adducts that are identical to those formed after lipid peroxidation. Of these adducts, N2,3-ethenoguanine (epsilon G) is present in greatest amounts in tissues of exposed animals. After exposure to vinyl chloride for four weeks, epsilon G levels attain steady-state concentrations, such that the amount of newly formed adducts equals the number of adducts that are lost each day. We report the first dosimetry of epsilon G in rats exposed to 0, 10, 100 or 1100 ppm vinyl chloride for five days or four weeks. The number of adducts increased in a supralinear manner. Exposure to 10 ppm vinyl chloride for five days caused a two- to threefold increase in epsilon G over that of the controls, while four weeks' exposure resulted in a fivefold increase. This was confirmed with [13C2]vinyl chloride and by measuring exogenous and endogenous adducts in the same animals. Exposure to 100 ppm vinyl chloride for four weeks caused a 25-fold increase in epsilon G levels over that found in control rats, while exposure to 1100 ppm resulted in a 42-fold increase. The amount of endogenous epsilon G was similar in liver DNA from rats and humans. A comparable response to exposure was seen in rats and mice exposed to 0, 25, 250 or 2500 ppm vinyl fluoride for 12 months. There was a very high correlation between epsilon G levels in rat and mouse liver at 12 months and the incidence of haemangiosarcoma at two years. We were able to demonstrate that the target cell population for angiosarcoma, the nonparenchymal cells, contained more epsilon G than hepatocytes, even though nonparenchymal cells are exposed by diffusion of vinyl halide metabolites formed in hepatocytes. The expression of N-methylpurine-DNA glycosylase mRNA was induced in rat liver after exposure to either 25 or 2500 ppm vinyl fluoride. When this induction was investigated in hepatocytes and nonparenchymal cells, it was found that the latter had only 20% of the N-methylpurine-DNA glycosylase mRNA of hepatocytes, and that only the hepatocytes had induction of this expression after exposure to vinyl fluoride. Thus, the target cells for vinyl halide carcinogenesis have much lower expression of this DNA repair enzyme, which has been associated with etheno adduct repair.

Abstract P1-10-08: Development of a first-in-class oral selective ERα covalent antagonist (SERCA) for the treatment of ERαWT and ERαMUT breast cancer

Mutations in estrogen receptor alpha (ERα) are detected in up to 30% of breast cancer patients who have relapsed during endocrine therapy. ERα mutations functionally confer resistance to existing classes of endocrine therapies, likely through gaining constitutive activity. The fact that current ER-directed therapies are only partially effective in the ERα mutant setting, and that a significant proportion of resistant breast cancer metastases continue to remain dependent on ERα signaling for growth/survival, highlights the critical need to develop the next generation of ERα antagonists that can overcome aberrant ERα activity. Using structure-based drug design approaches we have identified a novel class of ERα antagonist referred to as Selective ERα Covalent Antagonist (SERCA) that inactivate both wild-type and mutant ERα by targeting a unique cysteine residue that is not conserved among other steroid hormone receptors. Biophysical, biochemical and cellular analyses confirm the covalent mechanism of action, specific binding to ER and selective inhibition of ERα-dependent transcription of SERCAs. H3B-6545 is a highly selective SERCA that potently antagonizes wild-type and mutant ERα in biochemical and cell based assays demonstrating increased potency over standard of care and other experimental agents. In vivo, H3B-6545 shows superior efficacy to fulvestrant in the MCF-7 xenograft model with once daily oral dosing, achieving maximal antitumor activity at doses >10x below the maximum tolerated dose in mice. In addition, H3B-6545 shows superior antitumor activity to both tamoxifen and fulvestrant in patient derived xenograft models of breast cancer carrying estrogen receptor mutations. In summary, H3B-6545 is a first-in-class, orally available and selective ER covalent antagonist with a compelling pre-clinical profile that is being developed for the treatment of ERα positive breast cancer.

Citation Format: Korpal M, Puyang X, Furman C, Zheng GZ, Banka D, Wu J, Zhang Z, Thomas M, Mackenzie C, Yao H, Rimkunas V, Kumar P, Caleb B, Karr C, Subramanian V, Irwin S, Larsen N, Vaillancourt F, Nguyen T-V, Davis A, Chan B, Hao MH, O'Shea M, Prajapati S, Agoulnik S, Kuznetsov G, Kumar N, Yu Y, Lai G, Hart A, Eckley S, Fekkes P, Bowser T, Joshi JJ, Selvaraj A, Wardell S, Norris J, Smith S, Reynolds D, Mitchell L, Wang J, Yu L, Kim A, Rioux N, Sahmoud T, Warmuth M, Smith PG, Zhu P. Development of a first-in-class oral selective ERα covalent antagonist (SERCA) for the treatment of ERαWT and ERαMUT 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 P1-10-08.

Divergent effects of chronic HIV-1 infection on human thymocyte maturation in SCID-hu mice

We have recently developed a modified SCID-hu mouse model in which the implanted human thymus and liver (hu-thy/liv) and human peripheral T cells become infected with HIV-1 after i.p. inoculation. By using this model, we evaluated the effect of HIV-1 infection on thymic maturation and observed that different HIV-1 strains had divergent effects of thymic maturation. Although minimal effects on continued thymopoiesis in the hu-thy/liv implant were observed after chronic infection with two primary patient isolates, HIV-1(28) and HIV-1(59), and with HIV-1ADA, HIV-1Ba-L, HIV-1JR-CSF, HIV-1JR-FL, and HIV-1SF162, significant thymocyte depletion was detected after infection with HIV-1IIIB and HIV-1RF. Thus, the effect of HIV-1 infection on thymocyte maturation may depend upon the strain of HIV-1 infecting the thymus. Despite the minimal effects on thymopoiesis observed in the hu-thy/liv implanted in SCID-hu mice 6 mo after infection with HIV-1(28), significant changes were seen in the human T cell population circulating in the peripheral blood of these mice. These changes ranged from an inversion of the CD4/CD8 ratio of peripheral human T cells in some SCID-hu mice to the almost complete depletion of peripheral human T cells observed in other SCID-hu mice. Because these effects were associated with the detection of HIV-1 infection of the peripheral human T cells, these modified SCID-hu mice should prove to be a valuable model for investigating the effects of chronic HIV-1 infection on the peripheral human T cell population.

[Therapeutic occlusion of unilateral vertebral artery for unclippable aneurysms; special reference to postoperative brainstem ischemia]

Seven cases of unclippable vertebral artery aneurysms (3 dissecting, 1 fusiform, 2 saccular and 1 giant) are reported. Five of these had subarachnoid hemorrhage, one showed mass effect and the other was found incidentally. Trapping of the involved portion of the vertebral artery was performed in 4 cases, proximal clip occlusion in 2 and proximal balloon occlusion in 1. There were no operative deaths and no rebleeding, but brainstem ischemia developed in 4 cases, two being transient and two permanent. The ischemic complications were possibly due to; (a) hypoperfusion in the transient cases and (b) thromboenbolism, from the partially thrombosed giant aneurysm or thrombosis of the cul-de-sac vertebral artery, in the permanent ones. Preoperative temporary vertebral artery occlusion with an inflatable balloon or postoperative anticoagulant therapy should be considered in the management protocol.

Modulation of natural killer and lymphokine-activated killer cell cytotoxicity by lactoferrin

Natural killer (NK) and lymphokine-activated killer (LAK) cell cytotoxic functions can be strongly augmented by the iron-carrier protein lactoferrin (LF). LF significantly enhances NK and LAK activities when added at the beginning of NK or LAK cytotoxicity assays. LF is effective in augmenting cytotoxic activities at concentrations as low as 0.75 microgram/ml, and higher concentrations of LF induce greater augmentation of NK and LAK. Iron does not appear to be essential for LF to increase NK and LAK, as depleting iron from LF with the chelator deferoxamine does not affect the capacity of LF to increase cytotoxicity. LF is known to have RNase enzymatic activity, and LF enhancement of NK and LAK can be blocked by RNA. However, LFs from two different sources with over 100-fold difference in RNase activity are equally effective in enhancing NK and LAK. Furthermore, purified non-LF RNase does not modulate NK or LAK activity and DNA is as effective as RNA in blocking LF augmentation of NK or LAK cytotoxicity. Therefore, the RNase activity is unlikely to be responsible for LF enhancement of the cytotoxicities. Newborn infants are known to have low NK activity and NK and LAK cells have been implicated in host defense against microbial infections. Thus, maternal milk-derived LF may have a role in boosting antimicrobial immunity in the early stages of life. In adults, LF released from neutrophils may enhance NK and LAK functions in the inflammatory process induced by microbial infections.

Comparative Evaluation of the Q3 and Hybrid III 3-Year-Old Dummies in Biofidelity and Static Out-of-Position Airbag Tests

A comparison of the Q3 and Hybrid III 3-year-old crash test dummies is presented in this paper. The performance of the dummies were compared in sixty biofidelity tests, seventy-seven static out-of-position airbag tests and sixty-three calibration tests. Various time histories and other data pertaining to accelerations, deflections, forces and moments are compared. In addition, the ease of positioning, handling, and the durability of the dummies in various out-of-position test configurations was assessed. Both the Q3 and Hybrid III 3-year-old dummies were calibrated to their respective specifications. The Hybrid III 3-year-old met its calibration requirements, while the Q3 did not always meet its own calibration requirements. The calibration specifications of the Q3 dummy need to be re-examined and possibly refined. The biofidelity of the Q3 and Hybrid III 3-year-old dummies were evaluated in both frontal and lateral test modes. Each dummy was evaluated against its own and the other's specified requirements, when possible. In the frontal test mode, the Hybrid III 3-year-old acceptably met all of its requirements. The Q3 dummy did not meet all of its own frontal biofidelity requirements. Based on these results, the Hybrid III 3-year-old is more biofidelic for primarily frontal loading conditions. With respect to the lateral biofidelity specifications, neither the Hybrid III 3-year-old nor the Q3 dummy met the requirements for the thorax and pelvis tests performed. Both dummies met the head drop requirements. Neither dummy is recommended for lateral loading conditions. For lateral testing where only the head is impacted, the Hybrid III 3-year-old could be used. In general, the responses of both dummies were repeatable in both the frontal and lateral biofidelity tests performed. The Hybrid III 3-year-old and the Q3 dummies were evaluated in static out-of-position airbag tests with three different side airbag systems (two seat-mounted and one door-mounted system), and one frontal passenger airbag system. Throughout this testing, the Q3 resultant head accelerations exhibited an excessive amount of high-frequency noise causing this dummy to be unacceptable for static out-of-position airbag testing. No significant issues were found with the Hybrid III 3-yearold. It was also determined that the Q3 dummy was more difficult to position repeatedly than the Hybrid III 3-yearold. This was due to the dummy's construction and its lack of rigid landmarks.

Effect of HIV infection on pre- and post-liver transplant mortality in patients with organ failure

OBJECTIVES

Organ failure (OF), a leading cause of death in HIV-positive individuals, is common in patients undergoing liver transplantation (LT). We examined the impact of HIV infection on pre- and post-LT mortalities in cirrhotic patients stratified by the number and type of OFs.

METHODS

We performed a cross-sectional study and a retrospective cohort study using the US National Inpatient Sample (NIS) and the United Network for Organ Sharing (UNOS) registry data, respectively. Patients who had not yet undergone LT from the NIS database (2010-2014) and patients undergoing LT from the UNOS database (2003-2016) were included in the study.

RESULTS

Analysis of patients (201 348) from the NIS database showed that one [adjusted odds ratio (aOR) 1.531; 95% confidence interval (CI) 1.160-2.023], two (aOR 1.624; 95% CI 1.266-2.083) or three or more OFs (aOR 1.349; 95% CI 1.165-1.562) were associated with higher pre-LT mortality in HIV-infected patients compared with HIV-negative patients with the corresponding number of OFs. In patients without OF, HIV infection was not associated with increased pre-LT mortality. UNOS data for patients undergoing LT (38 942) showed that the presence of two or more OFs was associated with increased post-LT 1-year mortality in HIV-infected patients compared with non-HIV-infected patients with the corresponding number of OFs (aOR 2.342; 95% CI 1.576-3.480). However, in patients with no OF or only one OF, HIV infection was not associated with increased post-LT 1-year mortality (aOR 1.372; 95% CI 0.911-2.068).

CONCLUSIONS

The results of this study emphasize the importance of preventing OF development, and justify LT for HIV-infected patients with no or only one OF.

A CD10-positive subset of malignant cells is identified in multiple myeloma using PCR with patient-specific immunoglobulin gene primers

Immunophenotypic studies show the presence of CD10-bearing malignant cells in a small subset of multiple myeloma (MM) patients. We used a sensitive PCR-based technique in order to determine the frequency that MM patients contain a malignant subpopulation which expresses this antigen. The immunoglobulin (Ig) heavy chain variable region (VH) gene sequence expressed by the malignant clone in MM can be used as a tumor specific marker. After determining this sequence in six MM patients, patient specific VH oligonucleotide primers from complementarity determining region (CDR) sequences were generated. Bone marrow mononuclear cells from these patients were incubated with two different anti-CD10 antibodies or isotype identical murine IgG controls. Cells were then sorted by flow cytometry into the 1% brightest cells containing > 99.99% CD10-positive cells and two fractions including the 90 and 10% dimmest staining cells. PCR amplification was performed on DNA from approximately 10(4) cells (0.1 microgram) using patient specific CDR1 and CDR3 primers. Detectable PCR product was obtained in each sorted sample although the intensity of the band was much higher in cells lacking CD10 expression (the 90 and 10% dimmest fractions) than in the CD10-bearing (1% brightest) population. These results imply that there is a small population of CD10-bearing clonal cells in most, if not all patients with MM.

Substrate properties of site-specific mutant ubiquitin protein (G76A) reveal unexpected mechanistic features of ubiquitin-activating enzyme (E1)

Ubiquitin-mediated proteolysis proceeds via the formation and degradation of ubiquitin-protein conjugates. Ubiquitin (Ub)-activating enzyme (E1) catalyzes the first, MgATP-dependent step in the conjugative reaction sequence. With wild type ubiquitin, the product of the E1 reaction is a ternary complex (E1-Ub-AMP-Ub) containing one thiol-linked ubiquitin (via the Ub COOH terminus, Gly-76) and one tightly bound ubiquitin adenylate. The thiol-linked ubiquitin is subsequently transferred to the thiol of a ubiquitin-conjugating enzyme (E2 protein); the latter adduct is the proximal donor of ubiquitin to the target protein. A mutant ubiquitin, bearing a Gly to Ala substitution at the COOH terminus (G76A-ubiquitin), was characterized as a substrate for E1. G76A-ubiquitin 1) supported PPi-ATP exchange poorly (500-fold decrease in kcat/K(m); 2) did not produce detectable AMP-Ub with native E1; 3) produced stoichiometric AMP-Ub with thiol-blocked E1; 4) gave a stoichiometric burst of ATP consumption (1 mol/mol E1) with either native or thiol-blocked E1; 5) supported E1-ubiquitin thiol ester formation with native E1; 6) supported several downstream reactions of the proteolytic pathway at approximately 20% of the rate of wild type ubiquitin. These results indicate that G76A-ubiquitin gives a binary E1 thiol ester complex with native E1, due to the failure of the E1-ubiquitin thiol ester to undergo another round of adenylate synthesis; thus AMP-Ub is detected only if adenylate to thiol transfer is prevented by alkylating E1. The inability of G76A-ubiquitin to support ternary complex formation has implications for E1 active site structure. In other experiments, occupancy of the nucleotide/adenylate site of E1, by either MgATP or AMP-Ub, was found to stimulate ubiquitin transthiolation between E1 and E2 proteins. The intermediacy of ubiquitin adenylate thus provides a previously unrecognized catalytic advantage in the E1 mechanism.

The hematopoietic stem cell antigen, CD34, is not expressed on the malignant cells in multiple myeloma

Autologous stem cell transplantation has become an important therapy in multiple myeloma (MM). To develop adequate autograft purging methods, it is necessary to determine whether antigens expressed on early hematopoietic progenitors exist on malignant cells. The Ig heavy chain produced by the MM cells shows evidence of prior somatic mutation without intraclonal diversity. As a result, this sequence can be used as a specific marker to detect all members of the malignant clone. The Ig heavy chain sequence expressed by the MM cells was obtained in five patients with advanced disease. Patient specific oligonucleotide primers were designed based on the complementarity determining regions (CDR) of each MM Ig sequence and used to amplify DNA by polymerase chain reaction for the detection of malignant cells. A highly purified collection of CD34+ cells was obtained after passage of the initial bone marrow cells through an immunoadsorption column and fluorescence-activated cell sorting. Despite an assay sensitivity of 1 tumor cell in 2,500 to 44,000 normal cells, none of the CD34+ samples showed product with the myeloma-specific CDR primers. Therefore, positive selection for cells bearing this antigen should yield a tumor-free autograft capable of providing hematopoietic recovery after myeloablative chemotherapy.