Contemporary approach to cardiogenic shock care: a state-of-the-art review

Cardiogenic shock (CS) is a time-sensitive and hemodynamically complex syndrome with a broad spectrum of etiologies and clinical presentations. Despite contemporary therapies, CS continues to maintain high morbidity and mortality ranging from 35 to 50%. More recently, burgeoning observational research in this field aimed at enhancing the early recognition and characterization of the shock state through standardized team-based protocols, comprehensive hemodynamic profiling, and tailored and selective utilization of temporary mechanical circulatory support devices has been associated with improved outcomes. In this narrative review, we discuss the pathophysiology of CS, novel phenotypes, evolving definitions and staging systems, currently available pharmacologic and device-based therapies, standardized, team-based management protocols, and regionalized systems-of-care aimed at improving shock outcomes. We also explore opportunities for fertile investigation through randomized and non-randomized studies to address the prevailing knowledge gaps that will be critical to improving long-term outcomes.

Machine Learning Multicenter Risk Model to Predict Right Ventricular Failure After Mechanical Circulatory Support: The STOP-RVF Score

Importance

The existing models predicting right ventricular failure (RVF) after durable left ventricular assist device (LVAD) support might be limited, partly due to lack of external validation, marginal predictive power, and absence of intraoperative characteristics.

Objective

To derive and validate a risk model to predict RVF after LVAD implantation.

Design, Setting, and Participants

This was a hybrid prospective-retrospective multicenter cohort study conducted from April 2008 to July 2019 of patients with advanced heart failure (HF) requiring continuous-flow LVAD. The derivation cohort included patients enrolled at 5 institutions. The external validation cohort included patients enrolled at a sixth institution within the same period. Study data were analyzed October 2022 to August 2023.

Exposures

Study participants underwent chronic continuous-flow LVAD support.

Main Outcome and Measures

The primary outcome was RVF incidence, defined as the need for RV assist device or intravenous inotropes for greater than 14 days. Bootstrap imputation and adaptive least absolute shrinkage and selection operator variable selection techniques were used to derive a predictive model. An RVF risk calculator (STOP-RVF) was then developed and subsequently externally validated, which can provide personalized quantification of the risk for LVAD candidates. Its predictive accuracy was compared with previously published RVF scores.

Results

The derivation cohort included 798 patients (mean [SE] age, 56.1 [13.2] years; 668 male [83.7%]). The external validation cohort included 327 patients. RVF developed in 193 of 798 patients (24.2%) in the derivation cohort and 107 of 327 patients (32.7%) in the validation cohort. Preimplant variables associated with postoperative RVF included nonischemic cardiomyopathy, intra-aortic balloon pump, microaxial percutaneous left ventricular assist device/venoarterial extracorporeal membrane oxygenation, LVAD configuration, Interagency Registry for Mechanically Assisted Circulatory Support profiles 1 to 2, right atrial/pulmonary capillary wedge pressure ratio, use of angiotensin-converting enzyme inhibitors, platelet count, and serum sodium, albumin, and creatinine levels. Inclusion of intraoperative characteristics did not improve model performance. The calculator achieved a C statistic of 0.75 (95% CI, 0.71-0.79) in the derivation cohort and 0.73 (95% CI, 0.67-0.80) in the validation cohort. Cumulative survival was higher in patients composing the low-risk group (estimated <20% RVF risk) compared with those in the higher-risk groups. The STOP-RVF risk calculator exhibited a significantly better performance than commonly used risk scores proposed by Kormos et al (C statistic, 0.58; 95% CI, 0.53-0.63) and Drakos et al (C statistic, 0.62; 95% CI, 0.57-0.67).

Conclusions and Relevance

Implementing routine clinical data, this multicenter cohort study derived and validated the STOP-RVF calculator as a personalized risk assessment tool for the prediction of RVF and RVF-associated all-cause mortality.

Design and Rationale for the Direct Oral Anti-Coagulant Apixaban in Left Ventricular Assist Devices (DOAC LVAD) Study

Implantable left ventricular assist devices (LVAD) therapy is used to improve quality of life, alleviate symptoms, and extend survival in patients with advanced heart failure (HF). LVAD patients require chronic anticoagulation to reduce the risk of thromboembolic complications and frequently experience bleeding events. Apixaban is a direct oral anticoagulant which has become first-line therapy for patients with non-valvular atrial fibrillation and venous thromboembolism; however, its safety in LVAD patients has not been well-characterized. The evaluation of the hemocompatibility of the Direct Oral Anti-Coagulant apixaban in Left Ventricular Assist Devices (DOAC LVAD) trial is a Phase 2, open label trial of LVAD patients randomized to either apixaban or warfarin therapy. Patients randomized to apixaban will be started on a dose of 5 mg twice daily, while those randomized to warfarin will be managed to an INR goal of 2.0-2.5. All patients will be treated with aspirin 81mg daily. We plan to randomize and follow up to 40 patients for 24 weeks to evaluate the primary outcome of freedom from death or hemocompatibility related adverse events (HRAEs) (stroke, device thrombosis, bleeding, aortic root thrombus, and arterial non-CNS thromboembolism). DOAC LVAD will establish the feasibility of apixaban anticoagulant therapy in LVAD patients. Clinicaltrials.gov: NCT04865978.

Commercial ChIP-Seq Library Preparation Kits Performed Differently for Different Classes of Protein Targets

Background

Chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-Seq) is a powerful method commonly used to study global protein-DNA interactions including both transcription factors and histone modifications. We have found that the choice of ChIP-Seq library preparation protocol plays an important role in overall ChIP-Seq data quality. However, very few studies have compared ChIP-Seq libraries prepared by different protocols using multiple targets and a broad range of input DNA levels.

Results

In this study, we evaluated the performance of 4 ChIP-Seq library preparation protocols (New England Biolabs [NEB] NEBNext Ultra II, Roche KAPA HyperPrep, Diagenode MicroPlex, and Bioo [now PerkinElmer] NEXTflex) on 3 target proteins, chosen to represent the 3 typical signal enrichment patterns in ChIP-Seq experiments: sharp peaks (H3K4me3), broad domains (H3K27me3), and punctate peaks with a protein binding motif (CTCF). We also tested a broad range of different input DNA levels from 0.10 to 10 ng for H3K4me3 and H3K27me3 experiments.

Conclusions

Our results suggest that the NEB protocol may be better for preparing H3K4me3 (and potentially other histone modifications with sharp peak enrichment) libraries; the Bioo protocol may be better for preparing H3K27me3 (and potentially other histone modifications with broad domain enrichment) libraries, and the Diagenode protocol may be better for preparing CTCF (and potentially other transcription factors with well-defined binding motifs) libraries.  For ChIP-Seq experiments using novel targets without a known signal enrichment pattern, the NEB protocol might be the best choice, as it performed well for each of the 3 targets we tested across a wide array of input DNA levels.

174. Temporizing Surgical Measures for Deep Mechanical Circulatory Support Device Infections: Case Series Report

Background

Durable mechanical circulatory support device (MCSD) use continues to grow. MCSD deep-seated infections are a serious complication. Removal of the infected hardware is not always possible.

Methods

Single institution retrospective review of all culture-proven deep MCSD infection (pump and/or driveline) from 2009–2019. Patients were managed with intravenous (IV) and oral (PO) antibiotics; definitive surgical interventions included incision and drainage (I&D), device replacement, and heart transplant; and temporizing surgical measures were chronic chest tube (CCT) drainage for pump pocket and mediastinum and antibiotic impregnated bead implantation for driveline infection. Outcomes were analyzed.

Results

Total of 29 patients identified, 23 (79%) were male. Median age at device implantation was 44 years (20–68). MCSD were 18 (62%) destination therapy and 11 (38%) bridge to transplant. MCSD included 1 Heartmate I, 17 Heartmate II, 1 Heartmate III, 4 Heartware HVAD, and 6 Syncardia TAH. The median time to infection of 258 days (43–1551), affecting pump in 8 (28%), pump + driveline in 13 (44%), and driveline in 8 (28%). Microorganisms were S. aureus in 17 (60%, MRSA 11 and MSSA 6); coag-negative staphylococci in 3 (10%); Viridans streptococci in 1; Serratia marcescens in 3; P. aeruginosa in 2; Klebsiella oxytoca in 1; Mycobacterium abscessus in 1 and C. albicans in 1. Antibiotics are given to 28 patients, 23 (80%) with initial IV for a median of 6 weeks (1–14) and 5 (17%) with initial PO, for a median of 7 weeks (2–20). Nineteen patients (83%) on IV received PO antibiotics after. 17 patients (61%) remained on chronic suppression antibiotics (13 PO, 2 IV, 2 PO and IV). Twenty-six (90%) patients had I&D, 6 (21%) had device replacement and 11 (38%) had transplant. Of 21 patients with pump infection 16 (76%) had CCT drainage of pump pocket site or mediastinum for a median of 116 days (range 10–887 days). Of 21 patients with driveline infections, 6 (29%) had antibiotic impregnated bead implants. Overall survival at 90 days was 28/29 (95%) and 24/29 (83%) at 1 year. Infection-related mortality in Table 1.

Conclusion

Deep MCSD infection remains a challenging clinical problem. CCT drainage (for pump) and antibiotic-impregnated bead implant (for driveline) may be temporizing options for patients unable to undergo timely device replacement or heart transplant.

Disclosures

All authors: No reported disclosures.

Surgical Treatment of Heart Failure

More than 5 million Americans suffer from heart failure and more than 250,000 die annually. Cardiac surgery, as applied to advanced heart failure, has evolved significantly in the past 50 years. Current therapeutic interventions are focused on the appropriate assessment of myocardial dysfunction as a means to select the right patient for the appropriate procedure using state-of-the-art myocardial viability testing and metabolic testing to determine candidacy for conventional interventions, mechanical devices, or transplant. Advances in mechanical circulatory support with more efficient and less morbid ventricular assist devises offer the potential to change the trajectory of this growing epidemiologic dilemma.

Infections in Patients with a Total Artificial Heart Are Common but Rarely Fatal

Patients who received a total artificial heart (TAH) at Virginia Commonwealth University (VCU) between January 1, 2010 and December 31, 2011 were identified from the VCU Mechanical Circulatory Support Clinical Database. Retrospective data extraction from the medical records was performed from the time of TAH implantation until heart transplantation or death. Infections were classified as confirmed or suspected. Twenty-seven men and five women, mean age 49.5 years (range 24-68 years) received a TAH. The mean duration of TAH support was 225 days (range 1-1,334 days). Of the 32 patients, 4 (12.5%) died and 28 (87.5 %) underwent heart transplantation. Causes of death were pneumonia (n = 1), TAH malfunction (n = 1), refractory cardiogenic shock (n = 1), and respiratory failure (n = 1). Seventy documented and 13 suspected infections developed in 25 patients (78%). The most common sources of infection were urinary tract (n = 26), respiratory tract (n = 18), and bloodstream (n = 11). There were five pump infections and two driveline infections. The number of infections per patient ranged from 0 to 10. Sixteen different pathogens were identified; the most common were: Klebsiella pneumoniae (n = 15), coagulase-negative Staphylococci (n = 10), Enterococcus species (n = 9), and Enterobacter species (n = 8). Mortality directly attributable to infection was infrequent.

The total artificial heart

The total artificial heart (TAH) is a form of mechanical circulatory support in which the patient's native ventricles and valves are explanted and replaced by a pneumatically powered artificial heart. Currently, the TAH is approved for use in end-stage biventricular heart failure as a bridge to heart transplantation. However, with an increasing global burden of cardiovascular disease and congestive heart failure, the number of patients with end-stage heart failure awaiting heart transplantation now far exceeds the number of available hearts. As a result, the use of mechanical circulatory support, including the TAH and left ventricular assist device (LVAD), is growing exponentially. The LVAD is already widely used as destination therapy, and destination therapy for the TAH is under investigation. While most patients requiring mechanical circulatory support are effectively treated with LVADs, there is a subset of patients with concurrent right ventricular failure or major structural barriers to LVAD placement in whom TAH may be more appropriate. The history, indications, surgical implantation, post device management, outcomes, complications, and future direction of the TAH are discussed in this review.

Mechanical circulatory support devices in the ICU

The medical community has used implantable mechanical circulatory support devices at increasing rates for patients dying from heart failure and cardiogenic shock. Newer-generation devices offer a more durable and compact option when compared with bulky early-generation devices. This article is a succinct introduction and overview of the hemodynamic principles and complications after device implantation for ICU clinicians. We review the concepts of device physiology, clinical pearls for perioperative management, and common medical complications after device implantation.

Implantation of the syncardia total artificial heart

With advances in technology, the use of mechanical circulatory support devices for end stage heart failure has rapidly increased. The vast majority of such patients are generally well served by left ventricular assist devices (LVADs). However, a subset of patients with late stage biventricular failure or other significant anatomic lesions are not adequately treated by isolated left ventricular mechanical support. Examples of concomitant cardiac pathology that may be better treated by resection and TAH replacement includes: post infarction ventricular septal defect, aortic root aneurysm / dissection, cardiac allograft failure, massive ventricular thrombus, refractory malignant arrhythmias (independent of filling pressures), hypertrophic / restrictive cardiomyopathy, and complex congenital heart disease. Patients often present with cardiogenic shock and multi system organ dysfunction. Excision of both ventricles and orthotopic replacement with a total artificial heart (TAH) is an effective, albeit extreme, therapy for rapid restoration of blood flow and resuscitation. Perioperative management is focused on end organ resuscitation and physical rehabilitation. In addition to the usual concerns of infection, bleeding, and thromboembolism common to all mechanically supported patients, TAH patients face unique risks with regard to renal failure and anemia. Supplementation of the abrupt decrease in brain natriuretic peptide following ventriculectomy appears to have protective renal effects. Anemia following TAH implantation can be profound and persistent. Nonetheless, the anemia is generally well tolerated and transfusion are limited to avoid HLA sensitization. Until recently, TAH patients were confined as inpatients tethered to a 500 lb pneumatic console driver. Recent introduction of a backpack sized portable driver (currently under clinical trial) has enabled patients to be discharged home and even return to work. Despite the profound presentation of these sick patients, there is a 79-87% success in bridge to transplantation.

Persistent anemia after implantation of the total artificial heart

BACKGROUND

The total artificial heart (TAH) replaces the heart with 2 pneumatic pumps and 4 tilting disk mechanical valves. It was hypothesized that patients receiving TAH support have persistent hemolysis that resolves after heart transplantation (HT).

METHODS AND RESULTS

Hematocrit (HCT) was compared in patients on TAH to left ventricular assist device (LVAD) support for bridge to HT. Data were compared with t tests. The TAH (n = 36; mean age 47 ± 13 years) and LVAD patients (n = 14; mean age 53 ± 12 years) were supported for a median of 83 (interquartile range [IQR] 43-115) and 106 days (IQR 84-134), respectively. Hematocrit was similar between the TAH and LVAD patients (34 ± 6% vs 37 ± 5%; P = .07) at baseline. After placement, TAH patients had lower HCT at 2 (20 ± 2% vs 24 ± 3%), 4 (22 ± 3% vs 26 ± 3%), 6 (22 ± 4% vs 30 ± 4%), and 8 weeks (23 ± 4% vs 33 ± 5%; P < .001 for all). There were no differences in HCT at 1 (30 ± 4% vs 29 ± 7%; P = .42) and 3 months (35 ± 7% vs 35 ± 4%; P = .98) after removal of the devices for HT. TAH patients had undetectable haptoglobin in 96% of assessments, increased lactate dehydrogenase (1,128 ± 384 units/L), and detectable plasma free hemoglobin in 40% of measurements (21 ± 15 mg/dL). High sensitivity C-reactive protein (52 ± 50 mg/dL) was elevated, and reticulocyte production index was decreased (1.6 ± 0.6).

CONCLUSIONS

Patients implanted with a TAH have persistent anemia that resolves only after HT. The association of hemolysis, ineffective erythropoiesis, and inflammation with the TAH warrants further study.

NANOG promotes cancer stem cell characteristics and prostate cancer resistance to androgen deprivation

Cancer cell molecular mimicry of stem cells (SC) imbues neoplastic cells with enhanced proliferative and renewal capacities. In support, numerous mediators of SC self-renewal have been evinced to exhibit oncogenic potential. We have recently reported that shRNA-mediated knockdown of the embryonic stem cell (ESC) self-renewal gene NANOG significantly reduced the clonogenic and tumorigenic capabilities of various cancer cells. In this study, we sought to test the potential pro-tumorigenic functions of NANOG, particularly, in prostate cancer (PCa). Using quantitative RT-PCR, we first confirmed that PCa cells expressed NANOG mRNA primarily from the NANOGP8 locus on chromosome 15q14. We then constructed a lentiviral promoter reporter in which the -3.8 kb NANOGP8 genomic fragment was used to drive the expression of green fluorescence protein (GFP). We observed that NANOGP8-GFP⁺ PCa cells exhibited cancer stem cell (CSC) characteristics such as enhanced clonal growth and tumor regenerative capacity. To further investigate the functions and mechanisms of NANOG in tumorigenesis, we established tetracycline-inducible NANOG overexpressing cancer cell lines, including both prostate (Du145 and LNCaP) and breast (MCF-7) cancer cells. NANOG induction promoted drug-resistance in MCF-7 cells, tumor regeneration in Du145 cells, and, most importantly, castration-resistant tumor development in LNCaP cells. These pro-tumorigenic effects of NANOG were associated with key molecular changes, including an upregulation of molecules such as CXCR4, IGFBP5, CD133 and ALDH1. The present gain-of-function studies, coupled with our recent loss-of-function work, establish the integral role for NANOG in neoplastic processes and shed light on its mechanisms of action.

Implantable mechanical circulatory support: demystifying patients with ventricular assist devices and artificial hearts

Engineering advancements have expanded the role for mechanical circulatory support devices in the patient with heart failure. More patients with mechanical circulatory support are being discharged from the implanting institution and will be seen by clinicians outside the immediate surgical or heart-failure team. This review provides a practical understanding of device design and physiology, general troubleshooting, and limitations and complications for implantable left ventricular assist devices (pulsatile-flow and continuous-flow pumps) and the total artificial heart.

TEVAR for acute uncomplicated aortic dissection: immediate repair versus medical therapy

Medical management remains the standard treatment modality for acute uncomplicated descending aortic dissections. Intervention (by either open surgery or an endovascular approach) is currently reserved for patients who present with or subsequently develop complications (ie, complicated dissections). Despite the success of medical therapy in the acute management of uncomplicated dissection, long-term morbidity and mortality are far from ideal. The introduction of thoracic endovascular aortic repair (TEVAR) has been associated with reductions in morbidity and mortality in the treatment of complicated dissections. There is limited data regarding TEVAR for acute uncomplicated dissections. Early results from the INSTEAD (Investigation of Stent Grafts in Patients with Type B Aortic Dissection) trial, a randomized trial for TEVAR in subacute/chronic uncomplicated dissections, were not favorable. The ADSORB (Acute Uncomplicated Aortic Dissection Type B: Evaluating Stent-Graft Placement or Best Medical Treatment Alone) trial, a randomized trial for TEVAR in acute dissections, is currently underway. Nonetheless, current data available, including multiple reports proposing a variety of predictive factors, suggest that there may be a subset of higher-risk patients with acute uncomplicated dissections who could benefit from TEVAR.

Highly purified CD44+ prostate cancer cells from xenograft human tumors are enriched in tumorigenic and metastatic progenitor cells

CD44 is a multifunctional protein involved in cell adhesion and signaling. The role of CD44 in prostate cancer (PCa) development and progression is controversial with studies showing both tumor-promoting and tumor-inhibiting effects. Most of these studies have used bulk-cultured PCa cells or PCa tissues to carry out correlative or overexpression experiments. The key experiment using prospectively purified cells has not been carried out. Here we use FACS to obtain homogeneous CD44(+) and CD44(-) tumor cell populations from multiple PCa cell cultures as well as four xenograft tumors to compare their in vitro and in vivo tumor-associated properties. Our results reveal that the CD44(+) PCa cells are more proliferative, clonogenic, tumorigenic, and metastatic than the isogenic CD44(-) PCa cells. Subsequent molecular studies demonstrate that the CD44(+) PCa cells possess certain intrinsic properties of progenitor cells. First, BrdU pulse-chase experiments reveal that CD44(+) cells colocalize with a population of intermediate label-retaining cells. Second, CD44(+) PCa cells express higher mRNA levels of several 'stemness' genes including Oct-3/4, Bmi, beta-catenin, and SMO. Third, CD44(+) PCa cells can generate CD44(-) cells in vitro and in vivo. Fourth, CD44(+) PCa cells, which are AR(-), can differentiate into AR(+) tumor cells. Finally, a very small percentage of CD44(+) PCa cells appear to undergo asymmetric cell division in clonal analyses. Altogether, our results suggest that the CD44(+) PCa cell population is enriched in tumorigenic and metastatic progenitor cells.

Plasmolemmal potassium gradient does not affect lung protection by an ATP-regulated potassium channel opener

BACKGROUND

We have previously shown that metabolic arrest induced with ATP-regulated potassium channel openers (PCOs) can improve lung preservation by adding Aprikalim (a PCO, Rhone-Poulene Roher) to modified Euro-Collins solution for pulmonary artery flush. Because the membrane hyperpolarizing effects of a PCO potentially competes with the depolarizing effects of a hyperkalemic solution, this study evaluated the effects of the potassium gradient on PCO-mediated lung protection.

STUDY DESIGN

Twenty rabbits underwent lung protection in four groups. Group 1 underwent harvest and reperfusion as a "no ischemia" control. Groups 2, 3, and 4 underwent harvest followed by 18 hours of cold ischemic storage before reperfusion. Groups 1 and 4 received Euro Collins as the pulmonary flush at induction of ischemia. Group 2 received Euro Collins plus Aprikalim (100 microM); and group 3 received lactated Ringer's plus Aprikalim. After ischemic storage, the lungs were reperfused with autologous blood for 2 hours. Every 30 minutes, the lungs were given a 10-minute 100% fractional inspired oxygen (F(i)O(2)) challenge to measure maximal gas exchange as an indication of graft function.

RESULTS

Repeated measures ANOVA showed Aprikalim improved graft function after 18 hours of cold ischemia (p < 0.0001). No significant differences were found when Aprikalim was used in either Euro-Collins (group 2) or lactated Ringer's (group 3) solution.

CONCLUSIONS

The ability of the PCO Aprikalim to preserve gas exchange in a model of hypothermic pulmonary ischemia-reperfusion injury was not affected by the plasmolemmal potassium gradient. This is consistent with recent findings in myocardial protection studies that the protective effects of PCOs may be intracellular.

KCNE2 protein is expressed in ventricles of different species, and changes in its expression contribute to electrical remodeling in diseased hearts

BACKGROUND

Mutations in KCNE2 have been linked to long-QT syndrome (LQT6), yet KCNE2 protein expression in the ventricle and its functional role in native channels are not clear.

METHODS AND RESULTS

We detected KCNE2 protein in human, dog, and rat ventricles in Western blot experiments. Immunocytochemistry confirmed KCNE2 protein expression in ventricular myocytes. To explore the functional role of KCNE2, we studied how its expression was altered in 2 models of cardiac pathology and whether these alterations could help explain observed changes in the function of native channels, for which KCNE2 is a putative auxiliary (beta) subunit. In canine ventricle injured by coronary microembolizations, the rapid delayed rectifier current (I(Kr)) density was increased. Although the protein level of ERG (I(Kr) pore-forming, alpha, subunit) was not altered, the KCNE2 protein level was markedly reduced. These data are consistent with the effect of heterologously expressed KCNE2 on ERG and suggest that in canine ventricle, KCNE2 may associate with ERG and suppress its current amplitude. In aging rat ventricle, the pacemaker current (I(f)) density was increased. There was a significant increase in the KCNE2 protein level, whereas changes in the alpha-subunit (HCN2) were not significant. These data are consistent with the effect of heterologously expressed KCNE2 on HCN2 and suggest that in aging rat ventricle, KCNE2 may associate with HCN2 and enhance its current amplitude.

CONCLUSIONS

KCNE2 protein is expressed in ventricles, and it can play diverse roles in ventricular electrical activity under (patho)physiological conditions.

A porcine beating heart model for robotic coronary artery surgery

BACKGROUND

The application of robotically assisted coronary artery surgery continues to be investigated clinically. Consequently, there is a need for a simple method to train surgeons in performing these operations. The aim of the present study was to assess a model using an excised porcine heart for the training of surgeons in creating a robotically assisted arterial anastomosis.

METHODS

An ex vivo beating heart model was constructed with a porcine heart and was evaluated by 3 cardiac surgeons previously trained in robotic surgery. All anastomoses from the first half of the study were reviewed to measure anastomotic time, the number of sutures placed, and the rate of suture placement per minute and were compared to those completed in the second half of the study by means of a unpaired Student t test.

RESULTS

Fifty-seven anastomoses were completed with the beating heart model, 28 in the first half of the study and 29 in the second half. The mean time to create an anastomosis in the first half of the study was 19.3 minutes (range, 10-28 minutes), compared with 15.0 minutes (range, 7-20 minutes) in the second half; the difference did not meet statistical significance. However, the number of sutures placed per minute did increase in the second half of the study with a mean of 0.77 sutures per minute (range, 0.55-1.25), compared with 0.56 sutures per minute (range, 0.40-0.80) in the first half of the study (P <.0001). The number of sutures per anastomosis also decreased in the second half of the study with a mean of 9.0 sutures (range, 8-11), compared with 10.6 sutures (range, 8-16) in the first half of the study (P =.0049).

CONCLUSIONS

This preliminary experience demonstrated technical improvements in the second half of the study. Fewer sutures were placed per anastomosis with better precision, implying a learning curve that could be accelerated with our model. This porcine beating heart model represents an inexpensive training method that mimics the beating heart, complete with coronary blood flow, and may be used multiple times to train and assess a surgeon's skill in robotically assisted coronary surgery.

Warm ischemia lung protection with pinacidil: an ATP regulated potassium channel opener

BACKGROUND

Ischemia/reperfusion injury remains a limiting factor in lung transplantation. Traditional hyperkalemic preservation solutions are associated with a host of metabolic derangements. ATP-regulated potassium channel openers (PCOs) may provide an attractive alternative to traditional solutions by utilizing inherent mechanisms of ischemic preconditioning. The purpose of this study was to assess warm ischemia graft protection with pinacidil, a nonspecific PCO.

METHODS

An isolated recirculating blood perfused ventilated rabbit lung model was used (n = 15). No ischemia control lungs underwent immediate reperfusion (n = 5). Warm ischemia control lungs were flushed with lactated Ringers (LR), stored at 37 degrees C for 2.5 hours and then reperfused for 2 hours (n = 5). PCO protected lungs were flushed with LR + 100 micromol/L pinacidil, stored, and then reperfused (n = 5). Intermittent blood gases were taken from the pulmonary artery and left atria. Every 30 minutes, graft function was assessed with a 10-minute 100% fractional inspired oxygen concentration challenge to measure maximal gas exchange. Lung samples were graded for histologic injury and assayed for myeloperoxidase activity.

RESULTS

A mixed-models repeated measures ANOVA demonstrated a significant difference between groups. Tukey's honestly significant difference multiple comparison test demonstrated significantly improved graft function and reduced histologic injury with pinacidil protection compared with the warm ischemia controls. There was no significant difference in graft function or pathology grade between the pinacidil protected lungs and the no ischemia controls. A similar trend, although not significant, was seen in myeloperoxdiase activity.

CONCLUSIONS

Potassium channel openers with pinacidil can provide pulmonary protection against warm ischemia reperfusion injury.

Novel protection strategy for pulmonary transplantation

BACKGROUND

Ischemia-reperfusion injury continues to represent a significant challenge to successful lung transplantation. Traditional pulmonary ischemic protection is performed using hypothermic hyperkalemic depolarizing solutions to reduce the metabolic demands of the ischemic organ. Measures to further reduce the effects of ischemic injury have focused on the reperfusion period. We tested the hypothesis that novel physiologic hyperpolarizing solutions-using ATP-dependent potassium channel (K(ATP)) openers-given at the induction of ischemia, will reduce cellular injury and provide superior graft function even after prolonged periods of ischemia.

METHODS

An isolated blood-perfused ventilated rabbit lung model was used to study lung injury. Airway, left atrial, and pulmonary artery pressures were measured continuously during the 2-h reperfusion period. Oxygenation, as a surrogate of graft function, was measured using intermittent blood gas analysis of paired left atrial and pulmonary artery blood samples. Graft function was measured by oxygen challenge technique (F(i)O(2) = 1.0). Wet-to-dry ratio was measured at the conclusion of the 2-h reperfusion period. Control (Group I) lungs were perfused with modified Euro-Collins solution (depolarizing) and reperfused immediately (no ischemia). Traditional protection lungs were perfused with modified Euro-Collins flush solution and stored for 4 h (Group II) or 18 h (Group III) at 4 degrees C before reperfusion. Novel protection (Group IV) lungs were protected with a hyperpolarizing solution containing 100 nM Aprikalim, a specific K(ATP) channel opener, added to the modified Euro-Collins flush solution and underwent 18 h of ischemic storage at 4 degrees C before reperfusion.

RESULTS

Profound graft failure was measured after 18 h of ischemic storage with traditional protection strategies (Group III). Graft function was preserved by protection with hyperpolarizing solutions even for prolonged ischemic periods (Group IV). Wet-to-dry weight ratio, airway, left atrial, and pulmonary artery pressures were not significantly different between the groups.

CONCLUSIONS

We have created a model of predictable lung injury. Membrane hyperpolarization with a K(ATP) channel opener (PCO) provides superior prolonged protection from ischemia-reperfusion injury in an in vitro model of pulmonary transplantation.

Lack of replicative senescence in cultured rat oligodendrocyte precursor cells

Most mammalian somatic cells are thought to have a limited proliferative capacity because they permanently stop dividing after a finite number of divisions in culture, a state termed replicative cell senescence. Here we show that most oligodendrocyte precursor cells purified from postnatal rat optic nerve can proliferate indefinitely in serum-free culture if prevented from differentiating; various cell cycle-inhibitory proteins increase, but the cells do not stop dividing. The cells maintain high telomerase activity and p53- and Rb-dependent cell cycle checkpoint responses, and serum or genotoxic drugs induce them to acquire a senescence-like phenotype. Our findings suggest that some normal rodent precursor cells have an unlimited proliferative capacity if cultured in conditions that avoid both differentiation and the activation of checkpoint responses that arrest the cell cycle.

Evidence that axon-derived neuregulin promotes oligodendrocyte survival in the developing rat optic nerve

It was previously shown that newly formed oligodendrocytes depend on axons for their survival, but the nature of the axon-derived survival signal(s) remained unknown. We show here that neuregulin (NRG) supports the survival of purified oligodendrocytes and aged oligodendrocyte precursor cells (OPCs) but not of young OPCs. We demonstrate that axons promote the survival of purified oligodendrocytes and that this effect is inhibited if NRG is neutralized. In the developing rat optic nerve, we provide evidence that delivery of NRG decreases both normal oligodendrocyte death and the extra oligodendrocyte death induced by nerve transection, whereas neutralization of endogenous NRG increases the normal death. These results suggest that NRG is an axon-associated survival signal for developing oligodendrocytes.

Long-term culture of purified postnatal oligodendrocyte precursor cells. Evidence for an intrinsic maturation program that plays out over months

Oligodendrocytes myelinate axons in the vertebrate central nervous system (CNS). They develop from precursor cells (OPCs), some of which persist in the adult CNS. Adult OPCs differ in many of their properties from OPCs in the developing CNS. In this study we have purified OPCs from postnatal rat optic nerve and cultured them in serum-free medium containing platelet-derived growth factor (PDGF), the main mitogen for OPCs, but in the absence of thyroid hormone in order to inhibit their differentiation into oligodendrocytes. We find that many of the cells continue to proliferate for more than a year and progressively acquire a number of the characteristics of OPCs isolated from adult optic nerve. These findings suggest that OPCs have an intrinsic maturation program that progressively changes the cell's phenotype over many months. When we culture the postnatal OPCs in the same conditions but with the addition of basic fibroblast growth factor (bFGF), the cells acquire these mature characteristics much more slowly, suggesting that the combination of bFGF and PDGF, previously shown to inhibit OPC differentiation, also inhibits OPC maturation. The challenge now is to determine the molecular basis of such a protracted maturation program and how the program is restrained by bFGF.

Apoptosis induction by a novel anti-prostate cancer compound, BMD188 (a fatty acid-containing hydroxamic acid), requires the mitochondrial respiratory chain

We recently developed a class of novel anti-prostate cancer compounds, cyclic hydroxamates that elicit a potent apoptotic response in many tumor cells cultured in vitro (D.G. Tang et al., Biochem. Biophys. Res. Commun., 242: 380-384, 1998). The lead compound, termed BMD188, induces programmed cell death in a variety of prostate cancer cells in vitro as well as in vivo (L. Li et al., Anticancer Res., 19: 51-70, 1999). BMD188 kills androgen-independent prostate cancer cells as well as prostate cancer cells with a multidrug-resistance phenotype. The apoptotic effect of BMD188 in prostate cancer cells does not depend on cell cycle, p53 status, or its purported target, arachidonate 12-lipoxygenase, but does require caspase activation and seems to involve mitochondria. To synthesize more specific and effective anti-prostate cancer hydroxamic acid compounds, it is important to understand their mechanism(s) of action. In the present study, we studied the role of mitochondrial respiratory chain (MRC) in BMD188-induced apoptosis in androgen-independent prostate cancer PC3 cells and compared its effect with that of staurosporine (STS), a widely used apoptosis inducer. Several lines of evidence indicate that BMD188-induced cell death depends on MRC: (a) the death could be significantly inhibited by several complex-specific respiration inhibitors; (b) respiration-deficient rho0 cells were more resistant than wild-type parent cells to apoptosis induction by BMD188; and (c) BMD188 induced a rapid increase in reactive oxygen species in mitochondria, an up-regulation of cytochrome c oxidase subunits, a biphasic alteration (i.e., an early hyperpolarization, followed by later hypopolarization) in the mitochondrial membrane potential (delta psi(m)), dramatic changes in mitochondrial morphology and distribution prior to caspase activation, and an abnormal proliferation of mitochondria at the ultrastructural level. By contrast, STS-induced PC3 apoptosis seemed not to depend on MRC. Taken together, the data suggest that the MRC represents a functional target for anti-prostate cancer hydroxamates.

Hospital volume can serve as a surrogate for surgeon volume for achieving excellent outcomes in colorectal resection

OBJECTIVE

To examine the association of surgeon and hospital case volumes with the short-term outcomes of in-hospital death, total hospital charges, and length of stay for resection of colorectal carcinoma.

METHODS

The study design was a cross-sectional analysis of all adult patients who underwent resection for colorectal cancer using Maryland state discharge data from 1992 to 1996. Cases were divided into three groups based on annual surgeon case volume--low (< or =5), medium (5 to 10), and high (>10)--and hospital volume--low (<40), medium (40 to 70), and high (> or =70). Poisson and multiple linear regression analyses were used to identify differences in outcomes among volume groups while adjusting for variations in type of resections performed, cancer stage, patient comorbidities, urgency of admission, and patient demographic variables.

RESULTS

During the 5-year period, 9739 resections were performed by 812 surgeons at 50 hospitals. The majority of surgeons (81%) and hospitals (58%) were in the low-volume group. The low-volume surgeons operated on 3461 of the 9739 total patients (36%) at an average rate of 1.8 cases per year. Higher surgeon volume was associated with significant improvement in all three outcomes (in-hospital death, length of stay, and cost). Medium-volume surgeons achieved results equivalent to high-volume surgeons when they operated in high- or medium-volume hospitals.

CONCLUSIONS

A skewed distribution of case volumes by surgeon was found in this study of patients who underwent resection for large bowel cancer in Maryland. The majority of these surgeons performed very few operations for colorectal cancer per year, whereas a minority performed >10 cases per year. Medium-volume surgeons achieved excellent outcomes similar to high-volume surgeons when operating in medium-volume or high-volume hospitals, but not in low-volume hospitals. The results of low-volume surgeons improved with increasing hospital volume but never equaled those of the high-volume surgeons.

Hormone-refractory prostate cancer cells express functional follicle-stimulating hormone receptor (FSHR)

PURPOSE

Understanding growth regulation in hormone-refractory prostate cancer may provide avenues for novel treatment interventions. This study was conducted to characterize the expression of the receptor (FSHR) for follicle-stimulating hormone (FSH) in androgen-independent prostate cancer cell lines and in human malignant prostate tissues.

MATERIALS AND METHODS

Western blotting, immunohistochemistry (IHC), and flow cytometric analysis were used to study the expression of FSHR. The effect of FSH on cell growth and clonogenicity was studied using proliferation and clonogenic assays.

RESULTS

Immunohistochemistry revealed expression of FSH in PC3 and Du145 cells. FSHR was identified in PC3 and Du145 cells, as well as in human adenocarcinoma of the prostate. The specificity of the FSHR detected on prostate cancer tissues or cells by IHC and Western blotting was confirmed by preabsorbing the antibodies with the immunizing antigens. Stimulation of these hormone-refractory cells with FSH triggered a proliferative response in vitro, suggesting that the receptor is biologically active.

CONCLUSION

Hormone-refractory prostate cancer cells express FSH and biologically active FSHR. Our results suggest that FSHR and its ligand may play a role in the regulation of the growth of hormone-refractory prostate cancers.

Prostate secretory protein (PSP94) suppresses the growth of androgen-independent prostate cancer cell line (PC3) and xenografts by inducing apoptosis

BACKGROUND

PSP94 (prostate secretory protein of 94 aa; also called PIP), one of the predominant proteins secreted into the seminal fluid, was proposed as an independent diagnostic/prognostic marker for prostate cancers. It was also shown to inhibit rat prostate cancer growth. In this study, we investigated the effect of purified PSP94 on the growth of androgen-independent human prostate cancer cells (PC3) and its potential mechanism of action.

METHODS AND RESULTS

PSP94, in a dose- and time-dependent manner, inhibited the growth of PC3 cells. The protein demonstrated a stronger inhibitory effect on the colony-forming ability of PC3 cells in soft agar. A daily injection of PSP94 at 5 microg/kg/body weight resulted in a 50-60% inhibition in the growth of PC3 xenografts in athymic mice. PC3 cell growth inhibition by PSP94 resulted from cell death characteristic of morphological apoptosis, which was confirmed by dual fluorescence microscopy, electron microscopy, and DNA fragmentation assays. Mechanistic studies indicated that PSP94 enhanced the expression of proapoptotic protein Bax without affecting Bcl-2 levels.

CONCLUSIONS

This study suggests that PSP94 may represent a novel, apoptosis-based, antitumor agent applicable to the treatment of hormone-refractory human prostate cancers.

A novel hydroxamic acid compound, BMD188, demonstrates anti-prostate cancer effects by inducing apoptosis. I: In vitro studies

BACKGROUND

Prostate cancer is the most frequently diagnosed malignancy in the Western countries. Apoptosis-targeted drug development could represent a specific and effective weapon against the disease (Tang and Porter, 32: 284-293, 1997). We previously demonstrated that the arachidonate 12-lipoxygenase and its metabolic products could function as survival factors for many solid tumors (Tang et al., Proc. Natl. Acad. Sci. USA 93: 5241-5246, 1996; Tang and Honn, J. Cell. Physiol. 172: 155-170, 1997).

MATERIALS AND METHODS

In this study, we synthesized a series of novel cyclic hydroxamic acid compounds that demonstrated varying degrees of inhibitory effects on the arachidonate 12-lipoxygenase. Subsequently we studied the effects of these novel compounds on human prostate cancer cells. First, all these compounds were screened on androgen-independent PC3 adenocarcinoma cells. Second, based on the results (i.e., the LD50 values) of the primary, secondary and tertiary screening, lead compounds were determined. Third, the lead compounds were utilized to study their cytotoxic effects on various prostate cancer cells as well as several types of normal cells. Finally, the molecular nature of the cell death was thoroughly characterized and the potential mechanisms of cell death were determined.

RESULTS

About 30% of the compounds screened induced a strong apoptotic death of androgen-independent prostate cancer cells, PC3, with an LD50 mostly at 10-20 microM. A lead compound, BMD188 [cis-1-hydroxy-4-(1-naphthyl)-6-octylpiperidine-2-one], was subsequently identified which inhibited the growth of PC3 cells with an LD50 at approximately 10 microM. Comparative studies indicated that BMD188 induced a more potent apoptotic response in PC3 cells than several conventional chemotherapeutic drugs. Furthermore, unlike the above drugs, BMD188 could induce 100% apoptosis in tumor cells. BMD188 also caused apoptosis of other types of prostate cancer cells including cells with multidrug resistance phenotype, independent of the androgen-dependence and p53 status. By contrast, BMD188 generally demonstrated 2-5 fold lower cytotoxicity towards several normal cell types including normal prostate epithelial cells. The growth inhibition by BMD188 was due to apoptosis induction as evidenced by DNA ladder formation, PARP [poly(ADP-ribose)polymerase] cleavage, and typical apoptotic morphology. BMD188-induced apoptosis does not depend on its inhibitory effects on lipoxygenase since target cells (i.e., PC3 and Du145) did not express the lipoxygenase mRNA and protein. In contrast, the apoptosis-inducing effect of BMD188 in PC3 cells could be significantly inhibited by serine protease inhibitors TPCK and TLCK as well as by caspase inhibitors DEVD and zVAD. The involvement of caspases in the apoptotic effects of BMD188 was further confirmed by the activation of caspase-3 (CPP32). In the accompanying paper, we show that BMD188 also inhibits the primary growth and local invasion of Du145 prostate cancer cells orthotopically implanted into the SCID or athymic nude mice.

CONCLUSION

The data presented here suggest that these novel cyclic hydroxamic acid compounds, via induction of apoptotic death, may find potential clinical applications in the treatment of human prostate cancers.

Extract of Solanum muricatum (Pepino/CSG) inhibits tumor growth by inducing apoptosis

BACKGROUND

Apoptosis, or programmed cell death, is characterized by certain distinct morphological and biochemical features. Most chemotherapeutic drugs exert their anti-tumor effects by inducing apoptosis. Therefore, an effective compound inducing apoptosis appears to be a relevant strategy to suppress various human tumors. In a search for tumor inhibitors from various kinds of plants, we found that extracts from Solanum muricatum (CSG) can inhibit tumor growth both in vivo and in vitro by inducing apoptosis.

MATERIALS AND METHODS

A lyophilized aqueous fraction extracted from Solanum muricatum (CSG4) was used in this study. The human cell lines tested include: prostate (PC3, DU145), stomach (MKN45), liver (QGY-7721, SK-HEP-1), breast (MDA-MB-435), ovarian (OVCAR), colon (HT29) and lung (NCI-H209) cancer cells; NHP (prostate), HUVEC (umbilical vein endothelial cell), and WI-38 (lung diploid fibroblasts) normal cells. The cell survival was determined by either Cell Titer MTS cell proliferation kit or trypan blue dye exclusion assay. The apoptosis was analyzed by (a) apoptotic morphology by light microscopy; (b) DNA ladder formation; (c) PARP cleavage assay.

RESULTS

a) CSG possesses selective cytotoxic activity against all the tumor cell lines being tested. The LD50 value is 561-825 micrograms/ml. b) CSG showed a much lower cytotoxicity to NHP, HUVEC and WI-38 normal cell lines with LD50 value being 2.8-3.2 mg/ml, which is 3-6 fold higher than on tumor cells. c) The in vivo study demonstrated that injection of CSG (100 micrograms) directly into tumor mass can reduce the tumor volume dramatically in nude mice inoculated with MKN45 gastric cancer cells. d) CSG-mediated tumor growth inhibition is through induction of apoptotic cell death, as manifested by (a) typical apoptotic morphology; (b) DNA ladder formation; and (c) PARP cleavage assay.

CONCLUSION

Taken together, the present study suggests, for the first time, that CSG may represent promising new chemical entity which preferentially targets various tumor cells by triggering apoptosis.

A novel hydroxamic acid compound, BMD188, demonstrates anti-prostate cancer effects by inducing apoptosis. II: In vivo efficacy and pharmacokinetic studies

BACKGROUND

In the preceding paper, we demonstrated that, BMD188 [cis-1-hydroxy-4-(1-naphthyl)-6-octylpiperidine-2-one], a newly synthesized cyclic hydroxamic acid compound, induces potent apoptotic death of prostate cancer cells in vitro. In this project, we studied the in vivo pharmacokinetic behavior and anti-tumor efficacy of this novel compound.

MATERIALS AND METHODS

A bioavailability/elimination study was first performed using radiolabeled BMD188 administered to rats through intraperitoneal (i.p.), intravenous (i.v). or oral (p.o.) routes. Based on these pharmacokinetic data as well as pilot experiments on in vivo toxicity, two sets of efficacy studies, with i.p. administered BMD188, were performed in SCID mice or athymic nude mice which had been orthotopically transplanted with Du145 human prostate cancer cells. Tumor growth rate was measured and the final tumor weights and sizes determined. Subsequently, histopathological data were obtained and tumor tissue sections were used for apoptosis (i.e., TUNEL) staining.

RESULTS

The pharmacokinetic studies revealed low (approximately 8%) absorption through the p.o. route and high (approximately 70%) absorption through the i.p. route. The average plasma half life (T1/2) of BMD188 was approximately 50 h. Post-absorption, plasma elimination of radioactivity was similar to that in animals given [3H]-188 intravenously. The in vivo efficacy results indicate that i.p. administered BMD188 significantly inhibited the primary growth and local invasion of Du145 prostate cancer cells orthotopically implanted into SCID or athymic nude mice. The tumor-inhibitory effect of BMD188 was due to apoptosis induction in vivo, as revealed by histological analysis as well as TUNEL staining of the tumor tissue sections.

CONCLUSION

Collectively, the preceding in vitro and the current in vivo studies suggest that BMD188 and its analogs may find clinical applications in the treatment of prostate cancer patients by inducing apoptotic death of prostate cancer cells.

Extended survivability of prostate cancer cells in the absence of trophic factors: increased proliferation, evasion of apoptosis, and the role of apoptosis proteins

This project was undertaken to study the survival properties of various prostate cells, including normal (NHP), BPH (benign prostate hyperplasia), primary carcinoma (PCA), and metastatic prostate cancer cells (LNCaP, PC3, and Du145), in the absence of trophic factors. Cell proliferation and cell death were quantitated by enumerating the number of live cells using MTS/PMS kit and of dead (apoptotic) cells using 4',6-diamidino-2-phenylindole dihydrochloride nuclear staining. These cells demonstrated an overall survivability in the order of BPH < NHP < LNCaP < PC3 < PCA < Du145. Upon growth factor deprivation, NHP/BPH cells rapidly underwent apoptosis, leading to a decreased number of live cells. PCA/PC3/Du145 cells, in contrast, demonstrated an initial phase of aggressive growth during which apoptosis rarely occurred, followed by a "plateau" phase in which cell loss by apoptosis was compensated by cell proliferation, followed by a later phase in which apoptosis exceeded the cell proliferation. LNCaP cells demonstrated survival characteristics between those of NHP/BPH and PCA/PC3/Du145 cells. We concluded that the increased survivability in prostate cancer cells results from enhanced cell proliferation as well as decreased apoptosis. The molecular mechanisms for evasion of apoptosis in prostate cancer cells were subsequently investigated. Quantitative Western blotting was used to examine the protein expression of P53 and P21WAF-1, Bcl-2 and Bcl-X(L) (anti-apoptotic proteins), and Bax, Bak, and Bad (proapoptotic proteins). The results revealed that, upon trophic factor withdrawal, NHP and BPH cells upregulated wild-type p53 and proapoptotic proteins Bax/Bad/Bak and down-regulated the expression of P21. Furthermore, NHP and BPH cells endogenously expressed little or no Bcl-2. In sharp contrast, prostate cancer cells expressed nonfunctional P53 and various amounts of Bcl-2 proteins. Upon deprivation, these cancer cells up-regulated P21 and Bcl-2 and/or BclX(L), lost response to withdrawal-induced up-regulation of Bax/Bad/Bak or decreased or even completely lost Bax expression and expressed some novel proteins such as P25 and P54/55 complex. These data together suggest that prostate cancer cells may use multiple molecular mechanisms to evade apoptosis, which, together with increased proliferation, contribute to extended survivability of prostate cancer cells in the absence trophic factors.

12(S)-hydroxyeicosatetraenoic acid increases the actin microfilament content in B16a melanoma cells: a protein kinase-dependent process

12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE], a lipoxygenase metabolite of arachidonic acid, has been shown to be involved in a wide variety of cellular activities (i.e., adhesion, spreading, motility, invasion) which promote metastasis to occur in tumor cells. In this study, several techniques (Western blotting, flow cytometry and DNase I assay) were performed to examine the alterations in the distribution of G- and F-actin expressed in B16a melanoma cells. Each of these methods independently revealed that 12(S)-HETE treatment (0.1 mM, 15 min) resulted in an increase in the F-actin content in the cytoskeletal preparations. Since the integrity of cytoskeletal networks (i.e., actin filaments) can be dynamically regulated through protein phosphorylation, we investigated the potential role of several protein kinases in the 12(S)-HETE-induced actin polymerization. By flow cytometric analysis, 12(S)-HETE was found to increase the actin filament contents. This effect could be inhibited by protein kinase C (PKC) inhibitors (calphostin C and staurosporine) as well as by protein tyrosine kinase (PTK) inhibitor (genistein) but not by protein kinase A inhibitor (H8), suggesting that the 12(S)-HETE effect involves PKC and PTK. This conclusion is consistent with the observations that phorbol 12-myristate-13-acetate (PMA) mimics the biological effect of 12(S)-HETE in promoting the F-actin formation in B16a cells. As a final analysis, direct protein phosphorylation studies indicate that 12(S)-HETE treatment led to enhanced phosphorylation of myosin light chain, which may contribute to the increased stress fiber formation following 12(S)-HETE stimulation.

Role of protein kinase C and phosphatases in 12(S)-HETE-induced tumor cell cytoskeletal reorganization

Adherent B16 amelanotic melanoma (B16a) cells exposed to fatty acid 12(S)-HETE, a lipoxygenase metabolite of arachidonic acid, demonstrated a gradual dissolution of stress fibers and bundling-together of vimentin. The 12(S)-HETE effects on tumor cell cytoskeleton appeared 5 min after treatment, became prominent approximately 15 min following stimulation, and generally disappeared by 30 min. Simultaneous treatment of cells with 12(S)-HETE and okadaic acid (OA) prevented disappearance of the 12(S)-HETE effects by 30 min. Quantitative double immunoblotting of actin and vimentin indicated that actin, but not vimentin, underwent a time-related depolymerization. On the other hand, enhanced phosphorylation of vimentin but not of actin was observed after 12(S)-HETE treatment. 12(S)-HETE-enhanced vimentin phosphorylation was abolished by protein kinase C (PKC) inhibitor calphostin C, thus suggesting the involvement of PKC.

Apoptosis in the absence of cytochrome c accumulation in the cytosol

Cytochrome c release from mitochondria to and subsequent accumulation in the cytosol has been considered a prerequisite for apoptosis. In this study, we present evidence for apoptosis induction without accumulation of cytochrome c in the cytosol. U937 lymphoma cells treated with staurosprine released cytochrome c from mitochondria to cytosol prior to PARP cleavage and DNA fragmentation. However, U937 cells treated with BMD188 (a hydroxamic acid and a potent apoptosis inducer) did not demonstrate any cytochrome c accumulation in the cytosol during apoptosis induction. This different pattern of cytochrome c alterations was also observed with these two inducers on leukemic HL60 cells and epithelial PC3 cells. Furthermore, when PC3 cells were treated with a panel of apoptosis-inducing agents, it was found that camptothecin, bleomycin, VP16 and TNF-alpha induced varying amounts of cytosolic accumulation of cytochrome c either prior to or concurrent with PARP cleavage while vinblastine and BHPP did not. Taken together, the present results suggest that cytochrome c accumulation in the cytosol during apoptosis is a cell type- and inducer-dependent phenomenon.

BMD188, A novel hydroxamic acid compound, demonstrates potent anti-prostate cancer effects in vitro and in vivo by inducing apoptosis: requirements for mitochondria, reactive oxygen species, and proteases

A newly synthesized cyclic hydroxamic acid compound, BMD188 [cis-1-hydroxy-4-(1-naphthyl)-6-octylpiperidine-2-one], was found to induce the apoptotic death of cultured prostate cancer cells by activating caspase-3. Orally administered BMD188 significantly inhibited the primary growth of prostate cancer cells (Du145) orthotopically implanted into SCID mice. Mechanistic studies indicated that BMD188 did not alter the protein levels of several Bcl-2 family members. In contrast, the BMD188 effect required three essential factors: reactive oxygen species (ROS), the mitochondrial respiratory chain function, and proteases. First, the apoptosis-inducing effect of BMD188 could be blocked by ROS scavengers such as Desferal. Second, both BMD188-induced PARP cleavage as well as PC3 cell apoptosis could be dramatically inhibited by several complex-specific mitochondrial respiration blockers. The involvement of mitochondria was also supported by the observations that BMD188 dramatically altered the mitochondrial distribution and morphology without affecting the cellular ATP levels. Finally, the apoptosis-inducing effect of BMD188 in PC3 cells could be significantly inhibited by serine protease inhibitors (TPCK and TLCK) as well as by caspase inhibitors (zVAD-fmk and DEVD-CHO). Collectively, the present study suggests that BMD188 and its analogs may find clinical applications in the treatment of prostate cancer patients by inducing apoptotic death of prostate cancer cells.

Actin cleavage in various tumor cells is not a critical requirement for executing apoptosis

Actin is a major cytoskeletal protein which is involved in many physiological cellular functions such as motility, cell shape, and adhesion. Recently, actin has also been reported to be cleaved by apoptotic proteases (i.e., caspases) and this cleavage is thought to contribute to the apoptotic process. However, conflicting data also exists as to whether actin represents a true caspase substrate during apoptosis induction in vivo (i.e., inside the cells). In this study, we critically examined the actin cleavage patterns during apoptosis of several tumor cell lines derived from three different species (i.e., mouse, rat, and human). Our findings demonstrate that: 1) actin cleavage in vivo is not a common phenomenon since apoptosis caused by multiple inducers in most cell types examined occurs without evidence of actin degradation; and 2) in certain cell types (e.g., U937), spontaneous, actin cleavage is observed which is not prevented by various specific chemical/peptide inhibitors of proteases such as caspases or serine proteases although apoptosis per se is retarded by some of these inhibitors. Our results conclude that actin is not a critical substrate for apoptotic proteases in vivo during apoptosis.

Suppression of W256 carcinosarcoma cell apoptosis by arachidonic acid and other polyunsaturated fatty acids

Serum-cultured rat W256 carcinosarcoma cells of the monocytoid origin undergo rapid apoptosis in response to the lipoxygenase inhibitor NDGA (nordihydroguaiaretic acid). Exogenous arachidonic acid (AA), in a time- and dose-dependent fashion, suppressed NDGA-induced W256 cell apoptosis as well as DNA fragmentation, with the maximal effect observed at approximately 25 microM. Mobilization of endogenous AA by calcium ionophore A23187 provided an even stronger and longer-lasting protection against NDGA-caused cell death. The A23187 effect on AA release as well as W256 cell death can be blocked by bromophenacyl bromide, thus suggesting involvement of phospholipase A2 activation. Serum withdrawal similarly caused W256 cells to undergo typical apoptosis, which was not rescued by several growth factors commonly found in serum. However, exogenous AA suppressed serum starvation-induced W256 cell apoptosis and significantly extended cell survival in a dose-dependent manner. Lipoxygenase products, 12(S)- and 15(S)-, but not 5(S)-hydroxyeicosatetraenoic acid (HETE), in a dose-dependent fashion, also prevented both NDGA- and serum-starvation-induced W256 cell apoptosis. AA appears to suppress W256 cell apoptosis via distinct signaling pathway(s) since it does not prevent cell death triggered by several other inducers. Examination of a panel of polyunsaturated fatty acids revealed that alpha-linolenic and linoleic acid can also suppress NDGA-induced W256 cell apoptosis. Our data suggest that AA and other polyunsaturated fatty acids and/or their metabolites may enhance tumor growth not only by promoting cell proliferation but also by suppressing apoptosis.

Target to apoptosis: a hopeful weapon for prostate cancer

BACKGROUND

Prostate cancer is the most commonly diagnosed neoplasm and the second leading cause of male death in this country. Multiple genetic and epigenetic factors have been implicated in the oncogenesis and progression of prostate cancer. However, the molecular mechanisms underlying the disease remain largely unknown. The major difficulty in the clinical management of prostate cancer stems from the reality that reliable and accurate diagnostic/prognostic biomarkers are not available and that effective treatment regimens for hormone-resistant prostate cancers are yet to be developed.

METHODS

The present review, through extensive literature research, summarizes the most recently accumulated experimental and clinical data on the relationship between apoptosis and prostate cancer. We analyze the possibility of inducing prostate cancer cell apoptosis by: 1) androgen ablation by castration or biochemical antagonists: 2) chemotherapeutic drugs or natural/synthetic chemicals; 3) manipulation of apoptosis-related oncoproteins; and 4) modulation of intracellular signal transducers.

RESULTS

1) Prostate cancer, like most other solid tumors, represents a very heterogeneous entity. Most prostate cancers, at the time of clinical diagnosis, present themselves as mixtures of androgen-dependent and androgen-independent cells. 2) Most prostate cancers respond initially to androgen ablation since the population of androgen-dependent cells undergoes rapid apoptosis upon androgen withdrawal. However, androgen ablation rarely cures patients, most of whom will experience recurrence due to takeover of the tumor mass by androgen-independent tumor cells as well as the emergence of apoptosis-resistant clones as a result of further genetic alterations such as bcl-2 amplification. 3) On the other hand, although androgen-independent prostate cancer cells do not undergo apoptosis upon androgen blocking, they do maintain the appropriate molecular machinery of apoptosis. Therefore, certain conventional chemotherapy drugs can eliminate androgen-independent cancer cells by inducing apoptosis. 4) However, most drugs used in chemotherapy induce apoptosis or mediate cytotoxicity only in proliferating cancer cells. Human prostate cancer cells demonstrate very slow growth kinetics. Thus, novel chemical/natural products need be identified to eradicate those nonproliferating cancer cells. In this regard, the angiogenesis inhibitor, linomide, and a plant extract, beta-lapachone, demonstrate very promising apoptosis-inducing effects on prostate cancer cells in a proliferation-independent manner. 5) An alternative way to modulate the apoptotic response is by interfering with the expression levels of essential regulatory molecule of apoptosis. Bcl-2 and p53 represent two prime targets for such manipulations. 6) Finally, modulation of signal transduction pathways (e.g., intracellular Ca2+ levels, PKC activity) involved in apoptosis may also induce and/or enhance the apoptotic response of prostate cancer cells.

CONCLUSIONS

Modulation of apoptotic response represents a novel mechanism-based approach which may help identify novel drugs and/or develop new therapeutic regimens for the treatment of prostate cancers.

Apoptosis of W256 carcinosarcoma cells of the monocytoid origin induced by NDGA involves lipid peroxidation and depletion of GSH: role of 12-lipoxygenase in regulating tumor cell survival

Arachidonate lipoxygenases (LOX) and their products play an important role in mediating growth factor-supported tumor cell proliferation and growth. The LOX pathway may also be critical in regulating tumor cell survival and apoptosis. Blocking the 12-LOX gene expression with sequence-specific antisense oligos or its activity with general or isoform-specific LOX inhibitors induces a strong apoptotic response in rat W256 carcinosarcoma cells of the monocytoid origin (Tang et al., 1996, Proc. Natl. Acad. Sci. U.S.A., 93:5241-5246). In the present study, several molecular approaches confirmed the predominant expression of platelet-type 12-LOX in W256 cells, with no or little expression of 5- and 15-LOX. NDGA, a general LOX inhibitor and BHPP, a 12-LOX-selective inhibitor, induced rapid and dose-dependent apoptosis of serum-cultured W256 cells as well as several other tumor (in particular leukemia) cell lines, thus suggesting a potential role for LOX in mediating serum-supported tumor cell survival. The molecular mechanism of NDGA-induced W256 cell death was subsequently investigated. NDGA-induced apoptosis could be significantly postponed by overexpression of 12-LOX, thus suggesting that the NDGA effect is, at least partly, dependent on its inhibition of LOX (i.e., 12-LOX). W256 cell apoptosis induced by NDGA could also be effectively inhibited by GSH-elevating or thiol agents as well as by lipid peroxidation inhibitors and an inhibitor of mitochondria respiratory chain rotenone. Further experiments demonstrated that NDGA treatment triggered rapid lipid peroxidation leading to the depletion of cytosolic and mitochondrial GSH pools. Interestingly, the lipid peroxidation induced by NDGA could not be inhibited by conventional free radical scavengers nor by cyclooxygenase or cytochrome P-450 monooxygenase inhibitors. In summary, the present work suggests a role of 12-LOX in regulating serum (growth factor)-supported survival of certain tumor cells.