Survival and repair durability in patients undergoing concomitant aortic valve reimplantation and mitral valve repair

Objective

The study objective was to determine repair durability and survival in patients with and without connective tissue disorders undergoing concomitant aortic valve reimplantation and mitral valve repair.

Methods

From 2002 to 2019, 68 patients underwent concomitant aortic valve reimplantation and mitral valve repair, including 27 patients with Marfan syndrome (39.7%). Follow-up echocardiograms were analyzed using nonlinear multiphase mixed-effects cumulative logistic regression. The regurgitation grade over time was estimated by averaging patient-specific profiles. Survival and freedom from reoperation were estimated by the Kaplan-Meier method.

Results

At 7 years, 11% of patients had aortic insufficiency greater than mild (severe in 2 patients). There was no difference in greater than mild aortic insufficiency between patients with or without Marfan syndrome (P = .37). Twenty percent of patients had progressed to mitral regurgitation greater than mild (severe in only 1 patient). The prevalence of recurrent mitral regurgitation was higher in those without Marfan syndrome, with greater than mild regurgitation increasing to 24% by 2 years and remaining constant thereafter (P = .04). Freedom from reoperation on the aortic valve or mitral valve was 83% at 10 years and did not differ between Marfan syndrome groups. There were no cases of perioperative mortality. Survival at 5 and 10 years was 94% and 87%, respectively, without a difference between those with and without Marfan syndrome.

Conclusions

Patients can undergo a total repair strategy using combined aortic valve reimplantation and mitral valve repair procedures with a low risk of mortality and complications, with favorable freedom from both residual valve regurgitation and reoperation.

Abstract P2-05-05: Evaluation of pan-HER and c-MET inhibitors tested ex vivo in primary HER2- breast cancer cells with hyperactive c-MET and ErbB family signaling

Background: To elucidate the role of c-Met signaling and its involvement with ErbB signaling as a cancer driver, a new assay using an impedance biosensor, the CELx multi-pathway signaling function (CELx MP) test, was developed. The CELx MP Test measures ex vivo real-time live cell response to specific ErbB and c-Met agonists to diagnose breast tumors with hyperactive HER1, HER2, HER3, HER4, and c-MET signaling activity. A recent study quantified c-MET and ErbB-driven signaling activity in epithelial cell samples derived from fresh breast tumor specimens obtained from 74 HER2- breast cancer patients. Of the cell samples tested, 20 of 74, (27.0%; 95% CI=18%-38%) had both hyperactive c-MET signaling and at least one hyperactive ErbB-family receptor signaling. Using primary breast cancer cells with hyperactive c-MET and ErbB signaling and the CELx MP test, the current study set out to: 1) determine the IC50 values of six pan-HER and five c-MET inhibitors; and 2) characterize the efficacy of combinations of each pan-HER inhibitor with each c-MET inhibitor.

Methods: Epithelial cells from six HER2- tumor specimens with hyperactive c-MET and ErbB-driven signaling were obtained. Real-time live cell response to specific ErbB and c-Met agonists (NRG1b, EGF, or HGF) alone and in combination, with or without one of six pan-HER antagonists (neratinib, lapatinib, ibrutinib, dacomitinib, sapitinib, poziotinib) or one of five c-MET antagonists (tepotinib, cabozantinib, crizotinib, capmatinib, or savolitinib) was quantified using an xCELLigence RTCA impedance biosensor. Each individual drug IC50 was determined using a 1000-fold, 5-point, dose response curve with a single fixed concentration of a corresponding agonist. For the drug combination efficacy studies, fixed concentrations of the agonist mixture and clinically relevant concentrations of combinations of the antagonists were used to determine the percentage inhibition of the ErbB and c-MET signaling.

Results: The IC50 values for the individual c-MET and pan-HER inhibitors ranged from 3.10nM - 28nM and 2.67nM – 137.27nM, respectively. In the drug efficacy studies, an average of at least 80% of the ErbB and c-MET signaling activated by NRG1, EGF, and HGF co-stimulation was inhibited by each combination of c-MET and pan-HER inhibitors.

c-Met Inhibitor Resultsc-MET inhibitorIC50 (nM)Avg Inhibition (%) w/diff ErbBi's   Capmatinib3.1094Savolitinib3.3298Tepotinib14.7096Cabozantinib27.3699Crizotinib28.21100

Pan-HER Inhibitor ResultsPan-HER inhibitorIC50 (nM)Avg Inhibition (%) w/diff c-METi's   Poziotinib2.67100Neratinib4.81100Ibrutinib13.1099Dacomitinib22.06100Sapitinib41.2898Lapatinib137.2780

Conclusions: The CELx MP test using live cells measures IC50 values comparable to those derived using cell-free methods. Every combination of pan-HER and c-MET inhibitors provided comparably high (at least 80%) levels of inhibitory effect ex vivo. This suggests the sub-group of HER2- breast cancer patients diagnosed with coincident hyperactive c-MET and ErbB signaling by the CELx Test may respond to virtually any pan-HER and c-Met inhibitor combination. Studying combinations designed to minimize drug toxicities without sacrificing efficacy should thus be possible.

Citation Format: Laing LG, Burns DJ, Khan S, MacNeil IA, Rich BE, Kharbush SM, Soltani SM, Sullivan BF. Evaluation of pan-HER and c-MET inhibitors tested ex vivo in primary HER2- breast cancer cells with hyperactive c-MET and ErbB family signaling [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-05-05.

Abstract P2-09-22: Use of a functional signal profiling test with high sensitivity and specificity to determine the prevalence of abnormal HER2-driven signaling activity in the HER2-negative breast cancer patient population: New patient group may benefit from HER2 therapy

Background: Biological factors, such as HER2 signaling activity, may be important to measure in addition to expression and amplification of HER2 when identifying patients eligible for HER2 therapies. The CELx HER2 Signaling Function (CELx HSF) Test measures HER2 signaling activity in live tumor cells using a label-free impedance biosensor to identify HER2-negative breast cancer patients likely to be responsive to treatment with anti-HER2 therapies. Previous studies quantified HER2-driven signaling activity in a training set (N=34) of primary tissue samples from HER2-negative breast cancer patients and found 21% of the samples had abnormal HER2 signaling. Other studies confirmed that anti-HER2 therapies, such as trastuzumab, pertuzumab, afatinib, and neratinib, are as effective in inhibiting HER2-driven signaling activity in HER2- tumor cells as they are in HER2+ tumor cells. This study set out to confirm the prevalence of abnormal HER2 signaling amongst HER2-negative breast cancer patients in a larger sample (N=114) and to characterize the sensitivity and specificity of the CELx HSF Test.

Methods: A validation set of de-identified fresh breast tumor specimens were obtained from 114 HER2- breast cancer patients. Real time live cell response to specific HER2 agonists (NRG1b or EGF) with or without an antagonist (HER2 dimerization inhibitor) was measured using an impedance biosensor. From these responses, the net amount of HER2 participation in HER2 signaling initiated by the HER2 agonists was quantified. Samples with HER2 signaling activity levels above a previously determined cut-off value were identified as abnormal.

Results: Of the HER2- breast tumor cell samples tested, 27 of 114 patients (23.7%; 95% CI=17%-32%) had abnormal HER2 signaling activity. Little or no correlation was found between a patient's HER2 signaling activity and their estrogen receptor status or tumor grade. To compare the results obtained from the training set of 34 patients and the current set of 114 patients, the Kolmogorov-Smirnov two-sample test was applied (D=0.17, P-value 0.45) and found no significant difference between the training and validation sets. A normal mixture model was fitted to the new 114 patient data set and found that HER2- breast cancer patients fall into three distinct groups (abnormal, normal, low). Patients falling into the abnormal group had mean HER2 signaling scores 4.5 standard deviations above the mean score of the normal group. A ROC curve constructed with this data projects that both the sensitivity and specificity of the CELx HSF Test would be greater than 90%.

Conclusions: These results confirm that a clinically relevant proportion of HER2- breast cancer patients, approximately 20%, have tumors with abnormal HER2-signaling activity and may benefit from HER2 therapy. With high specificity and sensitivity, the CELx HSF test may be suitable as a companion diagnostic to identify new patients eligible to receive HER2 therapies. An interventional trial to evaluate the efficacy of trastuzumab and pertuzumab in HER2- patients selected with the CELx HSF test is underway.

Citation Format: Laing LG, Burns DJ, MacNeil IA, Rich BE, Myhre S, Soltani S, Sullivan BF. Use of a functional signal profiling test with high sensitivity and specificity to determine the prevalence of abnormal HER2-driven signaling activity in the HER2-negative breast cancer patient population: New patient group may benefit from HER2 therapy [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 P2-09-22.

Compensator design for improved counterbalancing in high speed atomic force microscopy

High speed atomic force microscopy can provide the possibility of many new scientific observations and applications ranging from nano-manufacturing to the study of biological processes. However, the limited imaging speed has been an imperative drawback of the atomic force microscopes. One of the main reasons behind this limitation is the excitation of the AFM dynamics at high scan speeds, severely undermining the reliability of the acquired images. In this research, we propose a piezo based, feedforward controlled, counter actuation mechanism to compensate for the excited out-of-plane scanner dynamics. For this purpose, the AFM controller output is properly filtered via a linear compensator and then applied to a counter actuating piezo. An effective algorithm for estimating the compensator parameters is developed. The information required for compensator design is extracted from the cantilever deflection signal, hence eliminating the need for any additional sensors. The proposed approach is implemented and experimentally evaluated on the dynamic response of a custom made AFM. It is further assessed by comparing the imaging performance of the AFM with and without the application of the proposed technique and in comparison with the conventional counterbalancing methodology. The experimental results substantiate the effectiveness of the method in significantly improving the imaging performance of AFM at high scan speeds.

Indirect identification and compensation of lateral scanner resonances in atomic force microscopes

Improving the imaging speed of atomic force microscopy (AFM) requires accurate nanopositioning at high speeds. However, high speed operation excites resonances in the AFM's mechanical scanner that can distort the image, and therefore typical users of commercial AFMs elect to operate microscopes at speeds below which scanner resonances are observed. Although traditional robust feedforward controllers and input shaping have proven effective at minimizing the influence of scanner distortions, the lack of direct measurement and use of model-based controllers have required disassembling the microscope to access lateral scanner motion with external sensors in order to perform a full system identification experiment, which places excessive demands on routine microscope operators. Further, since the lightly damped instrument dynamics often change from experiment to experiment, model-based controllers designed from offline system identification experiments must trade off high speed performance for robustness to modeling errors. This work represents a new way to automatically characterize the lateral scanner dynamics without addition of lateral sensors, and shape the commanded input signals in such a way that disturbing dynamics are not excited. Scanner coupling between the lateral and out-of-plane directions is exploited and used to build a minimal model of the scanner that is also sufficient to describe the nature of the distorting resonances. This model informs the design of an online input shaper used to suppress spectral components of the high speed command signals. The method presented is distinct from alternative approaches in that neither an information-complete system identification experiment nor microscope modification are required. Because the system identification is performed online immediately before imaging, no tradeoff of performance is required. This approach has enabled an increase in the scan rates of unmodified commercial AFMs from 1-4 lines s(-1) to over 40 lines s(-1).

Fracture-mechanics analysis of fatigue-crack propagation in polymethylmethacrylate

Repeated tension tests on centre-notched sheet specimens show that the rate of growth of fatigue cracks in polymethylmethacrylate is constant if the range of crack-tip stress-intensity factor is constant. Within the limits considered fatigue-crack growth rate was independent of specimen thickness and loading history.

Screening for Inhibitors of Histone Deacetylase by Incorporating a Spraying Method to Micro-Arrayed Compound Screening

We have developed a method of spraying assay reagents onto a target gel in the Micro-Arrayed Compound Screening ( micro ARCS) format. After application of target gels to compound sheets, subsequent reagents can be applied by spraying onto the target gel. The spraying method conserves on assay reagents by up to 10-fold, eliminates the need for casting additional agarose gels, and increases the throughput of a screen by 3-fold. To demonstrate the efficacy of applying the spraying method to micro ARCS, we screened over 600,000 compounds for inhibitors of histone deacetylase (HDAC). Commercially available HDAC substrate and reaction developer were sprayed directly onto the gel to initiate the reaction and to amplify the signal, respectively. Picks in the primary screen were retested at a density of 384 compounds per sheet in the micro ARCS format. IC(50) values for active compounds were confirmed in a 96-well plate assay. The screen identified several small molecule inhibitors of the enzyme, including members of several classes of known HDAC inhibitors. The combination of the high-density format of micro ARCS, the efficiency of the spraying method, and a timed sequence of adding assay reagents permitted a screening throughput of 200,000 tests an hour. We present the details of the screening format and the analysis of the hits from the screen.

Validation of FLIPR membrane potential dye for high throughput screening of potassium channel modulators

A fluorescence-based assay using the FLIPR Membrane Potential Assay Kit (FMP) was evaluated for functional characterization and high throughput screening (HTS) of potassium channel (ATP-sensitive K+ channel; K(ATP)) modulators. The FMP dye permits a more sensitive evaluation of changes in membrane potential with a more rapid response time relative to DiBAC4(3). The time course of responses is comparable to ligand-evoked activation of the channel measured by patch-clamp studies. The pharmacological profile of the K+ channel evaluated by using reference K(ATP) channel openers is in good agreement with that derived previously by DiBAC4(3)-based FLIPR assays. Improved sensitivity of responses together with the diminished susceptibility to artifacts such as those evoked by fluorescent compounds or quenching agents makes the FMP dye an alternative choice for HTS screening of potassium channel modulators.

Complex gel permeation assays for screening combinatorial libraries

Gel permeation methods have been commonly used to screen combinatorial libraries synthesized on a solid support. We report here three screens of combinatorial libraries using gel permeation assays. These include a simple enzymatic assay to identify inhibitors of the influenza enzyme neuraminidase, and two more complex assays designed to screen for inhibitors of the interleukin-8 (IL-8)-IL-8 receptor and the urokinase-urokinase receptor interactions, respectively. The IL-8 ligand-receptor assay makes use of IL-8 receptor-expressing cells attached to a membrane, thus enabling washing steps as part of the assay. The urokinase ligand-receptor assay employs an enzyme-linked immunosorbent assay-type format, previously thought to be amenable only to well-based assays. The results of these three screens are reported here, including the discovery of a novel series of acyclic inhibitors of neuraminidase. The development of complex assays in a gel permeation format allows for the routine screening of combinatorially as well as noncombinatorially made compound collections against virtually any kind of target, and is being widely used in our high throughput screening operations.

Identification and characterization of A-105972, an antineoplastic agent

A high-throughput screening assay was designed to select compounds that inhibit the growth of cultured mammalian cells. After screening more than 60,000 compounds, A-105972 was identified and selected for further testing. A-105972 is a small molecule that inhibits the growth of breast, central nervous system, colon, liver, lung, and prostate cancer cell lines, including multidrug-resistant cells. The cytotoxic IC50 values of A-105972 were between 20 and 200 nM, depending on the specific cell type. The potency of A-105972 is similar in cells expressing wild-type or mutant p53. A majority of cells treated with A-105972 were trapped in the G2-M phases, suggesting that A-105972 inhibits the progression of the cell cycle. Using [3H]A-105972, we found that A-105972 bound to purified tubulin. Unlabeled A-105972 competed with [3H]A-105972 binding with an IC50 value of 3.6 microL. Colchicine partially inhibited [3H]A-105972 binding with an IC50 value of approximately 90 microM, whereas paclitaxel and vinblastine had no significant effect. Tumor cells treated with A-105972 were observed to contain abnormal microtubule arrangement and apoptotic bodies. DNA ladder studies also indicated that A-105972 induced apoptosis. A-105972 caused a mobility shift of bcl-2 on SDS-PAGE, suggesting that A-105972 induced bcl-2 phosphorylation. A-105972 treatment increased the life span of mice inoculated with B16 melanoma, P388 leukemia, and Adriamycin-resistant P388. These results suggest that A-105972 is a small molecule that interacts with microtubules, arrests cells in G2-M phases, and induces apoptosis in both multidrug resistance-negative and multidrug resistance-positive cancer cells. A-105972 and its analogues may be useful for treating cell proliferative disorders such as cancer.

Photoaffinity detection of cAMP binding proteins in ovarian cancer

Identification of individual cyclic AMP binding proteins in tumor cytosolic extracts is possibly owing to the ability of (32)P-labeled 8-azido cyclic AMP to act as an effective analog of cAMP, to bind specifically to its protein effector sites, and on photo activation to incorporate covalently to these sites by means of a highly reactive nitrene derivative. Resolution of labeled proteins can be achieved by SDS-PAGE and visualization by autoradiography (1).

The category access measure of relational processing

Increases in category access (CA) and items recalled per category (IPC) are associated with increases in relational and item-specific processing, respectively. However, it has also been shown that CA increases as recall level increases and that CA scores following relational processing are actually below CA scores for randomly recalled items. These results prompted M. D. Murphy (1979) to suggest that, after adjusting for recall-level differences, relational processing decreases CA scores. Results of Experiment 1, along with a reanalysis of previously published data, showed that relational processing produces lower CA scores than purely item-specific processing (or random recall), but an increase in relational processing produces an increase in CA scores even when the CA and IPC scores are adjusted for recall-level differences. These results suggest a curvilinear relationship between relational processing and CA scores.

Application of QuantiGene nucleic acid quantification technology for high throughput screening

To identify inhibitors of interleukin-8 (IL-8) production, a high throughput assay was developed using the QuantiGene nucleic acid quantification kit that employs branched-chain DNA (bDNA) technology to measure the mRNA directly from cells. Unlike polymerase chain reaction and other technologies that employ target amplification, the QuantiGene system uses signal amplification. To perform the assay, various molecular probes capable of hybridizing with IL-8 mRNA were designed and synthesized. A human lung epithelial cell line was treated with interleukin-1alpha (IL-1alpha) to stimulate the IL-8 gene expression and the mRNA was measured using the QuantiGene system. The QuantiGene assay was sensitive, flexible, and reproducible and achieved equivalent or better sensitivity than promoter-reporter assays, and eliminated the time required for constructing a promoter-reporter system. Our data show that bDNA technology has the potential to be used as a high throughput screening assay.

The category access measure of relational processing

Increases in category access (CA) and items recalled per category (IPC) are associated with increases in relational and item-specific processing, respectively. However, it has also been shown that CA increases as recall level increases and that CA scores following relational processing are actually below CA scores for randomly recalled items. These results prompted M. D. Murphy (1979) to suggest that, after adjusting for recall-level differences, relational processing decreases CA scores. Results of Experiment 1, along with a reanalysis of previously published data, showed that relational processing produces lower CA scores than purely item-specific processing (or random recall), but an increase in relational processing produces an increase in CA scores even when the CA and IPC scores are adjusted for recall-level differences. These results suggest a curvilinear relationship between relational processing and CA scores.

Development of a p38 Kinase Binding Assay for High Throughput Screening

p38 is a member of the mitogen-activated protein kinase (MAPK) family of serine/threonine kinases, which is activated by cellular stressors and has been shown to be a critical enzyme in the synthesis and action of proinflammatory cytokines, tumor necrosis factor-a (TNF-alpha) and interleukin-1beta (IL-1beta). A group of pyridinyl imidazole compounds such as SB202190 have been identified as selective inhibitors of p38 that bind directly to the ATP pocket of the enzyme. These compounds inhibit the p38 kinase activity, block TNF-alpha and IL-1beta secretion both in vivo and in vitro and are found to be effective in animal models of arthritis, bone resorption, and endotoxin shock. We postulated that other classes of compounds capable of competing the binding of pyridinyl imidazole with p38 enzyme could have efficacy in the treatment of inflammatory diseases. Therefore, a simple and robust assay was developed to measure the ability of small molecules to inhibit the binding of tritium-labeled pyridinyl imidazole, SB202190, to recombinant p38 kinase. For assay development, the human p38 gene was cloned in baculovirus and then expressed in insect cells. Tritiated SB202190 was synthesized and used as the p38 ligand for a competitive filter binding assay. This assay has been used successfully to screen both synthetic and combinatorial chemical libraries for other classes of p38 kinase inhibitors.

An analysis of item gains and losses in retroactive interference

The repeated-testing paradigm is used to study both retroactive interference and hypermnesia (the improvement in memory across repeated tests). Considerable theoretical progress has been made by separately analyzing the 2 components of hypermnesia: the recovery of previously unrecalled items on later tests (item gains) and the forgetting of previously recalled items on later tests (item losses). Item gains increase with increases in item-specific processing, whereas item losses decrease with increases in relational processing. The authors suggest that separate analysis of item gains and losses in retroactive interference research may also prove fruitful. Three experiments showed that an interpolated list affects item gains but not losses, whereas processing similarity between the target and interpolated lists affects losses but not gains. These results are interpreted within the relational-item-specific processing framework.

An analysis of item gains and losses in retroactive interference

The repeated-testing paradigm is used to study both retroactive interference and hypermnesia (the improvement in memory across repeated tests). Considerable theoretical progress has been made by separately analyzing the 2 components of hypermnesia: the recovery of previously unrecalled items on later tests (item gains) and the forgetting of previously recalled items on later tests (item losses). Item gains increase with increases in item-specific processing, whereas item losses decrease with increases in relational processing. The authors suggest that separate analysis of item gains and losses in retroactive interference research may also prove fruitful. Three experiments showed that an interpolated list affects item gains but not losses, whereas processing similarity between the target and interpolated lists affects losses but not gains. These results are interpreted within the relational-item-specific processing framework.

Identification and regulation of protein kinase C-delta in human neutrophils

The intracellular mechanisms that regulate the function of human neutrophils are not well understood. Receptor-initiated signaling events result in the production of several second messengers (e.g., Ca2+, diacylglycerol, phosphatidic acid, and arachidonic acid) with the potential to activate members of the protein kinase C (PKC) family of signaling enzymes. The mixture of second messenger signaling molecules produced usually varies, depending on the particular receptor engaged. Previous work suggests that PKC has complex regulatory effects on neutrophil function. This may be due to the presence of multiple isoforms of the enzyme family, responding differentially to the second messengers produced. In studies to identify the PKC isoforms present in human neutrophils, we discovered the presence of the PKC isoform delta in these cells. Like other previously identified isoforms (alpha, beta I, beta II, and zeta), delta is a cytosolic enzyme in unstimulated neutrophils and partially translocates to membrane-containing fractions in cells stimulated by either the PKC activator PMA or the chemoattractant FMLP. Partial purification of cytosolic PKC gave two peaks of activity. The beta isoforms predominated in peak I, while the delta isoform predominated in peak II. The identification of delta indicates that neutrophils contain at least one member of the Ca(2+)-independent, diacylglycerol-dependent subfamily of PKC isoforms. Thus, this isoform may participate in Ca(2+)-independent, but diacylglycerol-dependent signaling events in these cells.

Identification and regulation of protein kinase C-delta in human neutrophils

The intracellular mechanisms that regulate the function of human neutrophils are not well understood. Receptor-initiated signaling events result in the production of several second messengers (e.g., Ca2+, diacylglycerol, phosphatidic acid, and arachidonic acid) with the potential to activate members of the protein kinase C (PKC) family of signaling enzymes. The mixture of second messenger signaling molecules produced usually varies, depending on the particular receptor engaged. Previous work suggests that PKC has complex regulatory effects on neutrophil function. This may be due to the presence of multiple isoforms of the enzyme family, responding differentially to the second messengers produced. In studies to identify the PKC isoforms present in human neutrophils, we discovered the presence of the PKC isoform delta in these cells. Like other previously identified isoforms (alpha, beta I, beta II, and zeta), delta is a cytosolic enzyme in unstimulated neutrophils and partially translocates to membrane-containing fractions in cells stimulated by either the PKC activator PMA or the chemoattractant FMLP. Partial purification of cytosolic PKC gave two peaks of activity. The beta isoforms predominated in peak I, while the delta isoform predominated in peak II. The identification of delta indicates that neutrophils contain at least one member of the Ca(2+)-independent, diacylglycerol-dependent subfamily of PKC isoforms. Thus, this isoform may participate in Ca(2+)-independent, but diacylglycerol-dependent signaling events in these cells.

Protein kinase C isozymes differentially regulate promoters containing PEA-3/12-O-tetradecanoylphorbol-13-acetate response element motifs

To investigate the regulation of promoters containing classical phorbol ester response sequences (PEA-3/12-O-tetradecanoylphorbol-13-acetate response element motifs) by protein kinase C (PKC) isozymes, co-transfections were performed in human dermal fibroblasts with a plasmid containing either the human collagenase promoter or the porcine urokinase plasminogen activator (uPA) promoter linked to the chloramphenicol acetyltransferase gene and a plasmid expressing an individual PKC isozyme. Using this experimental design, seven PKC isozymes were analyzed for their ability to trans-activate the collagenase and uPA promoters. Our results demonstrate that only PKC delta, epsilon, and eta trans-activated the collagenase promoter and that binding of Ap-1 family members to the collagenase 12-O-tetradecanoylphorbol-13-acetate response element (TRE) was not responsible for the isozyme-specific trans-activation. In contrast, the uPA promoter was stimulated by all of the PKC isozymes examined (PKC alpha, betaII, gamma, delta, epsilon, zeta, and eta). These results indicate that PKC isozymes differentially regulate promoters containing PEA-3/TRE motifs and suggest that individual isozymes play unique roles within the cell.

Pharmacokinetics, metabolism and tumour disposition of 8-chloroadenosine 3',5'-monophosphate in breast cancer patients and xenograft bearing mice

BACKGROUND

8-Chloroadenosine 3',5'-monophosphate (8-Cl-cAMP) is undergoing phase I clinical trials as an anticancer drug. However, there is debate as to whether it is a prodrug for its 8-Cl-adenosine metabolite.

DESIGN

Pharmacokinetics, metabolism and tumour disposition studies have been performed in 7 breast cancer patients receiving continuous infusion (28 day) 8-Cl-cAMP (0.54 or 1.08 mg/kg/day) and tumour biopsies were obtained before and on the last day of infusion. Parallel studies were performed in nude mice bearing the HT29 human colon cancer xenograft after continuous infusion (7 day) of active drug doses (50 or 100 mg/kg/day).

RESULTS

Steady state plasma levels (Css) of 8-Cl-cAMP in patients ranged from 0.15-0.72 microM but 8-Cl-adenosine was not detected in plasma. In contrast, 8-Cl-cAMP was not detectable in 3 tumour biopsies but 8-Cl-adenosine was present in 2 samples at high concentrations (1.33 and 2.02 microM). In mice, Css of 8-Cl-cAMP ranged from 3.2-4.6 microM and 8-Cl adenosine was present in plasma only at the higher dose (100 mg/kg/day, peak concentration of 2.3 microM). In the HT29 xenograft, 8-Cl-cAMP levels were considerably lower than in plasma (0.37-1.22 microM) while 8-Cl-adenosine was present at 5.3-21.0 microM and 8-Cl-AMP was found at 11.3-35.7 microM.

CONCLUSIONS

The fate of 8-Cl-cAMP in human tumours is characterised by extensive metabolism to products which are not generally observed in plasma. These data raise the possibility that 8-Cl-cAMP is a prodrug for a product of its metabolism in human tumours.

MARCKS phosphorylation by individual protein kinase C isozymes in insect Sf9 cells

Relatively little is known about the substrate specificity of individual protein kinase C (PKC) isozymes, particularly with respect to physiologically relevant substrates. One class of prominent cellular substrates for PKC is represented by the myristoylated alanine-rich C kinase substrate, or MARCKS, protein. In the present study, we have used a baculovirus expression system to coexpress human MARCKS with eight different isozymes of PKC, to determine which isozymes are capable of phosphorylating MARCKS in intact cells. In Sf9 cells, coexpression of MARCKS with individual PKC isozymes led to the following increases in MARCKS phosphorylation: alpha, 3.6-fold; beta iota, 4.6-fold; beta mu, 2.7-fold; gamma, 4.8-fold; delta, 3.0-fold; epsilon, 4.3-fold; and eta, 4.9-fold. In most cases, stimulation of cells with a phorbol ester led to a slight increase (20-30%) in MARCKS phosphorylation. PKC zeta did not phosphorylate MARCKS to any appreciable extent above control. In addition, in vitro kinetic analysis of PKC zeta showed that it has a 1000-fold lower affinity for a synthetic peptide comprising the MARCKS phosphorylation site domain compared to mixed conventional PKC isozymes from rat brain. These data indicate that MARCKS is a substrate in intact cells for at least seven isozymes of PKC: alpha; beta iota; beta mu; gamma; delta; epsilon; and eta. The isozyme PKC zeta does not appear to phosphorylate MARCKS in vivo or with significant affinity in vitro. Thus, PKC zeta, which is not activated by phorbol esters or diacylglycerol, also appears to behave differently with respect to this class of important cellular PKC substrates.

Cyclic adenosine 3',5'-monophosphate-binding proteins in human ovarian cancer: correlations with clinicopathological features

The regulatory subunits of protein kinase A, or cyclic AMP-binding proteins, were measured in a series of 107 human ovarian tumors (89 malignant, 7 borderline, and 11 benign tumors) and related to tumor clinicopathological features and patient survival. Total cyclic AMP-binding protein levels were not significantly different between malignant tumors and either borderline or benign tumors. However, serous tumors showed significantly higher levels of total cyclic AMP-binding proteins than other malignant tumors (P = 0.007). Poorly differentiated tumors also possessed significantly higher levels of binding proteins as compared with well/moderately differentiated tumors (P < 0.01). Retrospective analysis of follow-up data also revealed a significant trend for patients with high tumor cyclic AMP-binding proteins to have poorer survival (P = 0.03). Individual binding proteins were identified by photoaffinity labeling, and the RI (Mr 48,000) protein was expressed as a percentage of total cyclic AMP-binding proteins detected. The percentage of the RI protein was not significantly different among malignant, borderline, or benign pathologies and was not associated with tumor stage, differentiation, or debulk status. The percentage of RI was significantly increased in serous tumors compared to other common epithelial malignancies (P = 0.01). In malignant tumors there was a significant positive correlation between the percentage of the RI protein and total cyclic AMP-binding proteins (P = 0.01). These data indicate that high tumor levels of cyclic AMP-binding proteins are associated with serous histology, poor differentiation, and poor patient survival.

Protein kinase C chimeras: catalytic domains of alpha and beta II protein kinase C contain determinants for isotype-specific function

Protein kinase C (PKC) is involved in the proliferation and differentiation of many cell types. In human erythroleukemia (K-562) cells, the PKC isoforms alpha and beta II play distinct functional roles. alpha PKC is involved in phorbol 12-myristate 13-acetate-induced cytostasis and megakaryocytic differentiation, whereas beta II PKC is required for proliferation. To identify regions within alpha and beta II PKC that allow participation in these divergent pathways, we constructed chimeras in which the regulatory and catalytic domains of alpha and beta II PKC were exchanged. These PKC chimeras can be stably expressed, exhibit enzymatic properties similar to native alpha and beta II PKC in vitro, and participate in alpha and beta II PKC isotype-specific pathways in K-562 cells. Expression of the beta/alpha PKC chimera induces cytostasis in the same manner as overexpression of wild-type alpha PKC. In contrast, the alpha/beta II PKC chimera, like wild-type beta II PKC, selectively translocates to the nucleus and leads to increased phosphorylation of the nuclear envelope polypeptide lamin B in response to bryostatin-1. Therefore, the catalytic domains of alpha and beta II PKC contain determinants important for alpha and beta II PKC isotype function. These results suggest that the catalytic domain represents a potential target for modulating PKC isotype activity in vivo.

Regulation of phospholipase D by protein kinase C in human neutrophils. Conventional isoforms of protein kinase C phosphorylate a phospholipase D-related component in the plasma membrane

In a variety of intact cells, phorbol esters are known to activate phospholipase D. In a cell-free system consisting of plasma membrane and cytosol from human neutrophils, phorbol esters activated phospholipase D in an adenosine nucleotide triphosphate-dependent manner. ATP gamma S (adenosine 5'-O-(thiotriphosphate)) was 2-3-fold more effective than ATP, while ADP and AppNHp (adenyl-5'-yl imidodiphosphate) were ineffective, and activation was blocked by the kinase inhibitor staurosporine. In cytosol deplete of protein kinase C by chromatography on threnoine-Sepharose, phorbol ester-dependent activation was lost, but was restored upon addition of purified rat brain protein kinase C. The target for phosphorylation was shown to be the plasma membrane plasma membrane was phosphorylated using ATP gamma S/phorbol 12,13-dibutyrate and protein kinase C and was reisolated to remove activators. Upon adding nucleotide-depleted cytosol, activator-independent phospholipase D activity was seen. Using this prephosphorylation protocol, PKC-dependent activation of plasma membranes was found to require micromolar calcium, implicating a conventional protein kinase C. Using recombinant isoforms of protein kinase C, only the conventional isoforms showed significant activation, with the following rank order of potency: beta 1 > alpha > gamma; the beta 2, delta, epsilon, eta, and sigma isoforms showed little or no activity. Thus, conventional isoform(s) of protein kinase C activate neutrophil phospholipase D by phosphorylating a target protein located in the plasma membrane.

Growth inhibition by 8-chloro cyclic AMP of human HT29 colorectal and ZR-75-1 breast carcinoma xenografts is associated with selective modulation of protein kinase A isoenzymes

Significant dose-related inhibition of growth of HT29 human colorectal cancer xenografts and ZR-75-1 breast cancer xenografts in immune-suppressed mice was induced by the cyclic AMP analogue, 8-chloroadenosine 3',5'-cyclic monophosphate (8-Cl-cyclic AMP) when given by alzet mini-pumps over a 7-day period at doses of either 50 or 100 mg/kg/day. Levels and types of cyclic AMP binding proteins were measured by ligand binding and photoaffinity labelling, respectively, in tumours harvested at the end of the treatment period. Compared with levels in tumours from control animals, values of tumour cyclic AMP binding proteins from treated animals were significantly reduced. These effects were associated with an apparent modulation of the types of cyclic AMP binding proteins, 8-Cl-cyclic AMP-treated xenografts displaying a reduced ratio of RI/RII isoforms compared with untreated control tumours.

Activation of protein kinase C family members by the novel polyphosphoinositides PtdIns-3,4-P2 and PtdIns-3,4,5-P3

The effect of phosphoinositides on the activity of protein kinase C (PKC) isotypes was investigated. PKC alpha, beta I, beta II, gamma, delta, epsilon, eta, and zeta were expressed in baculovirus-infected insect cells and purified by column chromatography. The calcium-activated PKC isotypes alpha, beta I, beta II, and gamma were not significantly activated by any of the phosphoinositides investigated (phosphatidylinositol-4-phosphate (PtdIns-4-P), PtdIns-3-P, PtdIns-4,5-P2, PtdIns-3,4-P2, and PtdIns-3,4,5-P3) when added in the presence of concentrations of phosphatidylserine that give maximal stimulation. The calcium-insensitive PKC isotypes delta, epsilon, and theta also showed little response to PtdIns-3-P, PtdIns-4-P, or PtdIns-4,5-P2 when these lipids were added in the presence of phosphatidylserine. In contrast, PtdIns-3,4-P2 and PtdIns-3,4,5-P3 caused a 5-15-fold stimulation of these enzymes compared with phosphatidylserine alone. 50% maximal stimulation of PKC epsilon by PtdIns-3,4,5-P3 occurred when this lipid was present at about 1% of the carrier PtdIns-4,5-P2 (about 100 nM). These lipids had little effect on baculovirus-expressed PKC zeta, which was constitutively active. A short chain version of PtdIns-3,4,5-P3, dioctanoyl-PtdIns-3,4,5-P3, activated PKC delta, epsilon, and eta in the absence of other lipids, whereas a short chain version of PtdIns-4,5-P2, dihexanoyl-PtdIns-4,5-P2, did not. Since PtdIns-3,4-P2 and PtdIns-3,4,5-P3 are nominally absent in unstimulated cells and appear within seconds to minutes of stimulation by various cell activators, these lipids could act as second messengers to activate PKC delta, epsilon, or eta in vivo.

A cell-based reporter assay for the identification of protein kinase C activators and inhibitors

Transmission of extra cellular signals across biological membranes results in the generation of lipid metabolites which in turn influence specific cellular events such as cell growth or differentiation. Many of these lipid messengers can activate protein kinase C (PKC) isozymes of which one function is to perpetuate the extracellular signals to the nucleus by phosphorylating other targets proteins. We have engineered mammalian cell lines to identify and evaluate activators and inhibitors of PKC-dependent and independent signal transduction pathways. The A31 mouse fibroblast cell line, has been stably transfected with a construct containing a triplet repeat of the TPA response element (TRE) upstream of a thymidine kinase promoter fused to the human growth hormone (hGH) gene. A31 cells containing this reporter construct exhibit significant increases in hGH secretion following stimulation by phorbol esters or other mitogens. The levels of hGH secretion are modulated in this system using different pharmacological agents. We demonstrate that this assay can be used to identify specific and general inhibitors as well as activators of the signal transduction pathway mediated by PKC isozymes.

Translocation and downregulation of protein kinase C isoenzymes-alpha and -epsilon by phorbol ester and bryostatin-1 in human keratinocytes and fibroblasts

Protein kinase C isoenzymes can be subdivided into two classes, based on their requirement for calcium. Protein kinase C-alpha, beta I, -beta II, and -gamma are calcium dependent, whereas protein kinase C-gamma, -epsilon, -zeta, -eta, and -theta are calcium independent. We have examined the expression, translocation, downregulation, and activation of calcium-dependent and -independent protein kinase C isoenzymes in human skin keratinocytes and fibroblasts. Human keratinocytes and fibroblasts expressed protein kinase C-alpha, -delta, -epsilon, and -zeta mRNA and protein, whereas protein kinase C-eta (L) was detected only in keratinocytes. Protein kinase C-beta I, -beta II, -gamma, and -theta were not detected in either cell type. The protein kinase C activators 12-0-tetradecanoylphorbol 13-acetate and bryostatin-1 (50 nM, for 5 min) induced translocation of protein kinase C-alpha and -epsilon cytosol to membrane in both keratinocytes and fibroblasts. 12-0-tetradecanoylphorbol 13-acetate and bryostatin-1, for 18 h, induced complete downregulation (i.e., loss) of protein kinase C-alpha and -epsilon in keratinocytes, but only partial downregulation was observed in fibroblasts. The subcellular distribution of protein kinase C-delta, -zeta or protein kinase C-eta, in keratinocytes or fibroblasts, did not change in response to 12-0-tetradecanoylphorbol 13-acetate or bryostatin-1. These data indicate differential expression, subcellular distribution, and regulation of protein kinase C isoenzymes in human skin cells.

Presence of a beta II protein kinase C-selective nuclear membrane activation factor in human leukemia cells

In human promyelocytic (HL60) leukemia cells beta II protein kinase C (PKC) is selectively translocated to the nucleus in response to proliferative stimuli. At the nucleus, beta II PKC directly phosphorylates the nuclear envelope polypeptide lamin B at two consensus PKC phosphorylation sites, Ser395 and Ser405. Phosphorylation of these sites by beta II PKC leads to solubilization of lamin B indicative of mitotic nuclear envelope breakdown in vitro (Hocevar, B.A., Burns, D.J., and Fields, A.P. (1993) J. Biol. Chem. 268, 7545-7552). We have now investigated the molecular basis for beta II PKC-selective nuclear translocation and lamin B phosphorylation using an in vitro reconstitution system. We find that beta II PKC phosphorylates nuclear envelope lamin B at 10-20 times the rate of alpha PKC, whereas both kinases phosphorylate soluble lamin B at similar rates. Comparative tryptic phosphopeptide analysis demonstrates that alpha PKC and beta II PKC phosphorylate identical sites, Ser395 and Ser405, on soluble lamin B. These data suggest that a component(s) of the nuclear envelope confers beta II PKC-selective nuclear activation and lamin B phosphorylation. Extraction of nuclear envelopes with either non-ionic detergent (2% n-octyl glucoside) or organic solvent (CHCl3/CH3OH/H2O; 10:10:3) abolishes beta II PKC-selective phosphorylation of nuclear lamin B. Nuclear membrane extracts reconstitute beta II PKC-selective phosphorylation, indicating the presence of a beta II PKC-selective nuclear membrane activation factor (NMAF). NMAF selectively activates beta II PKC histone H1 kinase activity 3-4-fold above the level achieved with optimal concentrations of Ca2+, diacylglycerol, and phosphatidylserine. Finally, NMAF activity is not affected by exhaustive protease treatment, suggesting that it is a nuclear membrane lipid(s) or lipid metabolite. These data suggest that NMAF plays a physiologic role in the nuclear activation of beta II PKC.

The production of an active protein kinase C-delta in insect cells is greatly enhanced by the use of the basic protein promoter

Occasionally, only a small percentage of recombinant proteins produced in the baculovirus expression system are functionally active. We had previously shown that the majority of protein kinase C-delta (PKC-delta) produced in insect cells was inactive; less than 1% of the expressed enzyme had lipid-dependent kinase activity. In this report, we have attempted to optimize the production of a catalytically active PKC-delta. Under optimum conditions, we were able to increase the levels of PKC-delta from 10-20% to about 65% of the total cellular protein; however, there was no increase in the levels of catalytically active enzyme. Expression of PKC-delta as a fusion protein or as a secreted protein also met with limited success. Under all conditions, expression of PKC-delta proteins under control of the strong polyhedrin promoter resulted in the production of large amounts of inactive enzyme. Expression under the control of the basic protein promoter, Pcor, resulted in the reduction of the levels of recombinant protein by a factor of about four, but the PKC-delta enzyme produced under these conditions was 10- to 15-fold more active. Thus, the earlier temporal expression of PKC-delta in insect cells resulted in the production of more active enzyme.

Identification of nuclear beta II protein kinase C as a mitotic lamin kinase

Multisite phosphorylation of the nuclear lamins is thought to regulate the process of mitotic nuclear envelope breakdown in vivo. Here we investigate the involvement of two proposed human mitotic lamin kinases, beta II protein kinase C (PKC) and p34cdc2/cyclin B kinase, in human lamin B1 phosphorylation in vitro and in intact cells. We find that both kinases can phosphorylate purified soluble lamin B at similar rates. However, beta II PKC phosphorylates interphase nuclear envelope lamin B at more than 200 times the rate of human p34cdc2/cyclin B kinase. beta II PKC-mediated phosphorylation of lamin B is confined to two sites, Ser395 and Ser405, within the carboxyl-terminal domain, whereas human p34cdc2/cyclin B kinase phosphorylates a single site, Ser23, in the amino-terminal domain. A second potential p34cdc2/cyclin B kinase site within the carboxyl-terminal domain, Ser393, is not phosphorylated by human p34cdc2/cyclin B kinase. However, invertebrate p34cdc2/cyclin B kinase from sea star exhibits a different specificity, phosphorylating both amino- and carboxyl-terminal sites. Mitotic human lamin B from intact cells is phosphorylated predominantly in its carboxyl-terminal domain. Comparative tryptic phosphopeptide mapping demonstrates that the beta II PKC site, Ser405, is a prominent target of mitotic lamin B phosphorylation in vivo. beta II PKC translocates to the nucleus during the G2/M phase of cell cycle concomitant with phosphorylation of Ser405, indicating a physiologic role for nuclear beta II PKC activation in mitotic lamin B phosphorylation in vivo. The presence of phosphorylation sites within the carboxyl-terminal domain of mitotic lamin B which are not phosphorylated by either beta II PKC or p34cdc2/cyclin B kinase suggests the involvement of other lamin kinase(s) in G2/M phase lamin B phosphorylation.

Phospholipase D activation in fibroblast membranes by the alpha and beta isoforms of protein kinase C

The regulation of phosphatidylcholine-hydrolyzing phospholipase D (PLD) by protein kinase C (PRC) in membranes of Chinese hamster lung fibroblasts (CCL39) was studied using conventional PKC isoforms alpha, beta and gamma isolated from rat brain and recombinant PKC isoforms. Cells were incubated with [14C]choline to label endogenous phosphatidylcholine before membranes were prepared and assayed for release of [14C]choline. PKC alpha was the most potent activator of PLD, producing a maximal effect at approximately 0.1 microgram/ml. PKC beta also stimulated PLD but was less potent and less efficacious, whereas PKC gamma was ineffective. Stimulation required addition of a PKC activator, but the isoform specificity was the same whether phorbol 12-myristate 13-acetate (PMA) or Ca2+ was used. Recombinant Ca(2+)-independent PKC isoforms delta, epsilon, and zeta failed to stimulate PLD, but recombinant PKC beta 1 stimulated PLD in a manner similar to the purified brain PKC beta. Immunoblot analysis of the soluble fraction of CCL 39 fibroblasts detected only the alpha and zeta isoforms of PKC. The results suggest that PKC alpha and beta are activators of PLD and that PKC alpha is responsible for the activation in these fibroblasts.

Cyclic adenosine 3',5'-monophosphate-binding proteins in human ovarian cancers

The aims of the present study were to characterise an assay for cAMP-binding proteins in ovarian cancer and then to measure levels in a series of tumours with a view to developing a potential prognostic indicator for this disease. Levels and types of binding proteins have been measured in cytosols from 50 ovarian tumours. Binding proteins were detected in all tumours but, as calculated from Scatchard analysis, binding levels ranged from 267 to 12,037 fmol per mg of cytosol protein (mean value of 4248 fmol mg-1). Dissociation constants of binding varied between 0.4 x 10(-8) and 5.9 x 10(-8) (mean value 2.3 x 10(-8)). Types of binding protein were detected by incubation with the photoaffinity ligand 8-N3-[32P]cAMP, followed by polyacrylamide gel electrophoresis and autoradiography. Labelled proteins with molecular weights of 52, 48, 43, 39 and 37 kDa were identified in the cytosols. The proportion and pattern of bands detected varied between different cytosols. The significance of these findings awaits clinical follow-up of the patients.

A comparison of large-scale Sf9 insect cell growth and protein production: stirred vessel vs. airlift

A simple and relatively inexpensive stirred-vessel system for the large-scale growth of insect cells (Sf9) is described. Sf9 cell growth in a stirred-vessel fermentor and an airlift fermentor were compared on the basis of maximum cell density and average population doubling time. Also, both fermentor systems were compared with respect to the large-scale production of a recombinant human protein (protein kinase C-eta). No significant differences in Sf9 cell growth or protein expression levels were apparent between the two fermentor systems. However, large differences in cost and scale-up of each system are discussed with respect to the large-scale production of recombinant proteins.