Risk Factors for Early Fungal Disease in Solid Organ Transplant Recipients: A Systematic Review and Meta-analysis

BACKGROUND

Invasive fungal infections are associated with high morbidity in solid organ transplant recipients. Risk factor modification may help with preventative efforts. The objective of this study was to identify risk factors for the development of fungal infections within the first year following solid organ transplant.

METHODS

We searched for eligible articles through February 3, 2023. Studies published after January 1, 2001, that pertained to risk factors for development of invasive fungal infections in solid organ transplant were reviewed for inclusion. Of 3087 articles screened, 58 were included. Meta-analysis was conducted using a random-effects model to evaluate individual risk factors for the primary outcome of any invasive fungal infections and invasive candidiasis or invasive aspergillosis (when possible) within 1 y posttransplant.

RESULTS

We found 3 variables with a high certainty of evidence and strong associations (relative effect estimate ≥ 2) to any early invasive fungal infections across all solid organ transplant groups: reoperation (odds ratio [OR], 2.92; confidence interval [CI], 1.79-4.75), posttransplant renal replacement therapy (OR, 2.91; CI, 1.87-4.51), and cytomegalovirus disease (OR, 2.97; CI, 1.78-4.94). Both posttransplant renal replacement therapy (OR, 3.36; CI, 1.78-6.34) and posttransplant cytomegalovirus disease (OR, 2.81; CI, 1.47-5.36) increased the odds of early posttransplant invasive aspergillosis. No individual variables could be pooled across groups for invasive candidiasis.

CONCLUSIONS

Several common risk factors exist for the development of any invasive fungal infections in solid organ transplant recipients. Additional risk factors for invasive candidiasis and aspergillosis may be unique to the pathogen, transplanted organ, or both.

Cumulative epinephrine dose during cardiac arrest and neurologic outcome after extracorporeal cardiopulmonary resuscitation

BACKGROUND

Epinephrine is recommended without an apparent ceiling dosage during cardiac arrest. However, excessive alpha- and beta-adrenergic stimulation may contribute to unnecessarily high aortic afterload, promote post-arrest myocardial dysfunction, and result in cerebral microvascular insufficiency in patients receiving extracorporeal cardiopulmonary resuscitation (ECPR).

METHODS

This was a retrospective cohort study of adults (≥ 18 years) who received ECPR at large academic ECMO center from 2018 to 2022. Patients were grouped based on the amount of epinephrine given during cardiac arrest into low (≤ 3 mg) and high (> 3 mg) groups. The primary endpoint was neurologic outcome at hospital discharge, defined by cerebral performance category (CPC). Multivariable logistic regression was used to assess the relationship between cumulative epinephrine dosage during arrest and neurologic outcome.

RESULTS

Among 51 included ECPR cases, the median age of patients was 60 years, and 55% were male. The mean cumulative epinephrine dose administered during arrest was 6.2 mg but ranged from 0 to 24 mg. There were 18 patients in the low-dose (≤ 3 mg) and 25 patients in the high-dose (> 3 mg) epinephrine groups. Favorable neurologic outcome at discharge was significantly greater in the low-dose (55%) compared to the high-dose (24%) group (p = 0.025). After adjusting for age, those who received higher doses of epinephrine during the arrest were more likely to have unfavorable neurologic outcomes at hospital discharge (odds ratio 4.6, 95% CI 1.3, 18.0, p = 0.017).

CONCLUSION

After adjusting for age, cumulative epinephrine doses above 3 mg during cardiac arrest may be associated with unfavorable neurologic outcomes after ECPR and require further investigation.

Impact of intraoperative therapeutic plasma exchange on bleeding in lung transplantation

BACKGROUND

Our program uses a desensitization protocol that includes intraoperative therapeutic plasma exchange (iTPE) for crossmatch-positive lung transplants, which improves access to lung transplant for sensitized candidates while mitigating immunologic risk. Although we have reported excellent outcomes for sensitized patients with the use of this protocol, concern for perioperative bleeding appears to have hindered broader adoption of it at other programs. We conducted a retrospective cohort study to quantify the impact of iTPE on perioperative bleeding in lung transplantation.

METHODS

All first-time lung transplant recipients from 2014 to 2019 who received iTPE were compared to those who did not. Multivariable logistic regression was used to determine the association between iTPE and large-volume perioperative transfusion requirements (≥5 packed red blood cell units within 24 hours of transplant start), adjusted for disease type, transplant type, and extracorporeal membrane oxygenation or cardiopulmonary bypass use. The incidence of hemothorax (requiring reoperation within 7 days of lung transplant) and 30-day posttransplant mortality were compared between the 2 groups using chi-square test.

RESULTS

One hundred forty-two patients (16%) received iTPE, and 755 patients (84%) did not. The mean number of perioperative pRBC transfusions was 4.2 among patients who received iTPE and 2.9 among patients who did not. iTPE was associated with increased odds of requiring large-volume perioperative transfusion (odds ratio 1.9; 95% confidence interval: 1.2-2.9, p-value = 0.007) but was not associated with an increased incidence of hemothorax (5% in both groups, p = 0.99) or 30-day posttransplant mortality (3.5% among patients who received iTPE vs 2.1% among patients who did not, p = 0.31).

CONCLUSIONS

This study demonstrates that the use of iTPE in lung transplantation may increase perioperative bleeding but not to a degree that impacts important posttransplant outcomes.

Extending the age criteria of lung transplant donors to 70+ years old does not significantly affect recipient survival

OBJECTIVES

To determine the impact of older donor age (70+ years) on long-term survival and freedom from chronic lung allograft dysfunction in lung transplant (LTx) recipients.

METHODS

A retrospective single-center study was performed on all LTx recipients from 2002 to 2017 and a modern subgroup from 2013 to 2017. Recipients were stratified into 4 groups based on donor lung age (<18, 18-55, 56-69, ≥70 years). Donor and recipient characteristics were compared using χ2 tests for differences in proportions and analysis of variance for differences in means. Univariable and multivariable Cox regression was used to describe differences in long-term survival and freedom from chronic lung allograft dysfunction.

RESULTS

Between 2002 and 2017, 1600 LTx were performed, 98 of which were performed from donors aged 70 years or older. Recipients of 70+ years donor lungs were significantly older with a mean age of 55.5 ± 12.9 years old (P = .001) and had more Status 3 (urgent) recipients (37.4%, P = .002). After multivariable regression, there were no significant differences in survival or freedom from chronic lung allograft dysfunction between the 4 strata of recipients.

CONCLUSIONS

Lung transplantation using donors 70 years old or older can be considered when all other parameters suggest excellent donor lung function without compromising short- or long-term outcomes.

Heart-Lung Transplantation From Donation After Circulatory Death Using Mobile Normothermic Regional Perfusion

Combined heart-lung transplant (HTLx) is the most durable treatment available for end-stage heart and lung failure. Many patients are unable to receive combined organs due to organ availability and allocation policies prioritizing separate heart or lung transplantation. While an average of 45 HTLxs have been performed per year in the United States half the listed patients do not receive organs. Recently, donation after circulatory death (DCD) utilizing normothermic regional perfusion (NRP) has been utilized for heart allografts with excellent results, and here, we present a case utilizing mobile NRP to procure a heart and lung block from a circulatory death donor and successful implantation for a recipient in a separate center.

Early national trends of lung allograft use during donation after circulatory death heart procurement in the United States

Objective

Innovative technology such as normothermic regional perfusion and the Organ Care System has expanded donation after circulatory death heart transplantation. We wanted to investigate the impact of donation after circulatory death heart procurement in concurrent lung donation and implantation at a national level.

Methods

We reviewed the United Network for Organ Sharing database for heart donation between December 2019 and March 2022. Donation after circulatory death donors were separated from donation after brain death donors and further categorized based on concomitant organ procurement of lung and heart, or heart only.

Results

A total of 8802 heart procurements consisted of 332 donation after circulatory death donors and 8470 donation after brain death donors. Concomitant lung procurement was lower among donation after circulatory death donors (19.3%) than in donation after brain death donors (38.0%, P < .001). The transplant rate of lungs in the setting of concomitant procurement is 13.6% in donation after circulatory death, whereas it is 38% in donation after brain death (P < .001). Of the 121 lungs from 64 donation after circulatory death donors, 22 lungs were retrieved but discarded (32.2%). Normothermic regional perfusion was performed in 37.3% of donation after circulatory death donors, and there was no difference in lung use between normothermic regional perfusion versus direct procurement and perfusion (20.2% and 18.8%). There was also no difference in 1-year survival between normothermic regional perfusion and direct procurement and perfusion.

Conclusions

Although national use of donation after circulatory death hearts has increased, donation after circulatory death lungs has remained at a steady state. The implantation of lungs after concurrent procurement with the heart remains low, whereas transplantation of donation after circulatory death hearts is greater than 90%. The use of normothermic regional perfusion lungs has been controversial, and we report comparable 1-year outcomes to standard donation after circulatory death lungs. Further studies are warranted to investigate the underlying mechanisms of normothermic regional perfusion on lung function.

Determinants of Long-term Survival Decades After Esophagectomy for Esophageal Cancer

BACKGROUND

Long-term survival in esophagectomy patients with esophageal cancer is low due to tumor-related characteristics, with few reports of modifiable variables influencing outcome. We identified determinants of overall survival, time to recurrence, and disease-free survival in this patient cohort.

METHODS

Adult patients who underwent esophagectomy for primary esophageal cancer from January 5, 2000, through December 30, 2010, at our institution were identified. Univariate Cox models and multivariable logistic regression analyses were used to identify associations between modifiable and unmodifiable patient and clinical variables and outcome of survival for the total cohort and a subgroup with locally advanced disease.

RESULTS

We identified 870 patients with esophageal cancer who underwent esophagectomy. The median follow-up time was 15 years, and the 15-year overall survival rate was 25.2%, survival free of recurrence was 57.96%, and disease-free survival was 24.21%. Decreased overall survival was associated with the following unmodifiable variables: older age, male sex, active smoking status, history of coronary artery disease, advanced clinical stage, and tumor location. Decreased overall survival was associated with the following modifiable variables: use of neoadjuvant therapy, advanced pathologic stage, resection margin positivity, surgical reintervention, and blood transfusion requirement. The overall survival probability 6 years after esophagectomy was 0.920 (95% CI, 0.895-0.947), and time-to-recurrence probability was 0.988 (95% CI, 0.976-1.000), with a total of 17 recurrences and 201 deaths.

CONCLUSIONS

Once patients survive 5 years, recurrence is rare. Long-term survival can be achieved in high-volume centers adhering to National Comprehensive Cancer Network guidelines using multidisciplinary care teams that is double what has been previously reported in the literature from national databases.

Progress in genome-inspired treatment decisions for multifocal lung adenocarcinoma

INTRODUCTION

Multifocal lung adenocarcinoma (MFLA) is becoming increasingly recognized as a distinct subset of lung cancer, with unique biology, disease course, and treatment outcomes. While definitions remain controversial, MFLA is characterized by the development and concurrent presence of multiple independent (non-metastatic) lesions on the lung adenocarcinoma spectrum. Disease progression typically follows an indolent course measured in years, with a lower propensity for nodal and distant metastases than other more common forms of non-small cell lung cancer.

AREAS COVERED

Traditional imaging and histopathological analyses of tumor biopsies are frequently unable to fully characterize the disease, prompting interest in molecular diagnosis. We highlight some of the key questions in the field, including accurate definitions to identify and stage MLFA, molecular tests to stratify patients and treatment decisions, and the lack of clinical trial data to delineate best management for this poorly understood subset of lung cancer patients. We review the existing literature and progress toward a genomic diagnosis for this unique disease entity.

EXPERT OPINION

Multifocal lung adenocarcinoma behaves differently than other forms of non-small cell lung cancer. Progress in molecular diagnosis may enhance potential for accurate definition, diagnosis, and optimizing treatment approach.

Expanded extracorporeal membrane oxygenation bridge to heart and lung transplant candidate selection does not impact outcomes compared to traditional candidate selection criteria

Extracorporeal membrane oxygenation is used as a bridge to transplant (ECMO-BTT) in selected patients. The objective of this study was to determine whether 1-year post-transplant and post-ECMO survival are impacted by traditional compared to expanded selection criteria. We performed a retrospective study of patients >17 years who received ECMO as bridge to transplant (BTT) or bridge to transplant decision for lung or combined heart and lung transplantation at the Mayo Clinic Florida and Rochester. Institutional protocol excludes patients >55 years, maintained on steroids, unable to participate in physical therapy, with body mass index >30 or <18.5 kg/m², non-pulmonary end-organ dysfunction, or unmanageable infections from ECMO-BTT. For this study, adherence to this protocol was considered traditional whereas exceptions to the protocol were considered expanded selection criteria. A total of 45 patients received ECMO as bridge therapy. Out of those 29 patients (64%) received ECMO as bridge to transplant and 16 patients (36%) as bridge to transplant decision. The traditional criteria cohort consisted of 15 (33%) patients and expanded criteria cohort consisted of 30 (67%) patients. In the traditional cohort, 9 (60%) of 15 patients were successfully transplanted compared to 16 (53%) of 30 patients in the expanded criteria cohort. No difference in being delisted or dying on the waitlist (OR: 0.58, CI: 0.13-2.58), surviving to 1-year post-transplant (OR: 0.53, CI: 0.03-9.71) or 1-year post-ECMO (OR: 0.77, CI: 0.0.23-2.56) was observed between the traditional criteria and expanded criteria cohorts. At our institution, we did not see differences in odds of 1-year post-transplant and post-ECMO survival between those who met traditional criteria compared to those who did not. Multicenter, prospective studies are needed to evaluate the impact of ECMO-BTT selection criteria.

Lung Transplantation Long-term Survival is Worse in Patients Who Have Undergone Previous Cardiac Surgery

OBJECTIVE

Approximately 10% of lung transplant recipients have had previous cardiothoracic surgery. We sought to determine if previous surgery affects outcomes after lung transplant at a national level.

METHODS

The United Network for Organ Sharing database was analyzed from 2005-2019 to include adult patients who underwent lung transplant who had previous cardiac surgery, and previous thoracic surgery. T-test and chi-squared analysis was used to compare perioperative outcomes. Long-term survival comparison was performed using the Kaplan-Meier method in an unadjusted and propensity matched analysis.

RESULTS

Out of 24,784 lung transplants, 691 (2.7%) had previous cardiac surgery and 1,321 (6.5%) had previous thoracic surgery. Operative mortality was worse in previous cardiac surgery 42(6.1%) versus no previous cardiac surgery 740(3.1%), p < 0.001, and in previous thoracic surgery 65(4.9%) versus no previous thoracic surgery 717(3.1%), p < 0.001. The previous thoracic surgery group had more primary graft failure and treated rejection during the first-year post-transplant. There was no difference in stroke, dialysis, intubation and extracorporeal membrane oxygenation at 72 hours. Long-term survival was significantly worse for lung transplant patients who had undergone previous cardiac surgery (median 3.8 vs 6.3 years, p < 0.001) due to an increase in cardiovascular deaths (p = 0.008) and malignancy (p = 0.043). However, there was no difference in previous thoracic surgery (median 6.6 vs 6.1 years, p = 0.337).

CONCLUSIONS

Previous cardiac surgery prior to lung transplant results in worse survival related to cardiovascular death and malignancies. Previous thoracic surgery worsens perioperative outcomes but does not affect long term survival.

Analysis of Esophagectomy Margin Practice and Survival Implications

BACKGROUND

The objective of this study was to determine how thoracic surgeons manage intraoperative esophagectomy positive margins and how these decisions may relate to overall survival and progression-free survival in esophageal cancer.

METHODS

A survey was sent to thoracic surgeons to understand the management of intraoperative positive esophagectomy margins. Primary data at two high-volume esophageal cancer institutions from 1994 to 2017 were retrospectively reviewed to identify patients who had intraoperative positive frozen section margins during esophagectomy. Patient characteristics and survival data were collected and analyzed. Overall survival and progression-free survival were assessed using a Cox model.

RESULTS

Eighty-five percent of thoracic surgeons responding to a survey reported the utilization of frozen pathologic evaluation during esophagectomy with attempts at re-resection to achieve negative margin. Our esophagectomy database identified 94 patients with intraoperative positive margins. Of those re-resected (n = 67, 63%), 44 patients (46.8%) were converted to R0 resections. overall survival was improved for patients in the R0 group (13 months) vs R+ group (3.4 months, P = .04). Progression-free survival was also improved between the R0 group (8.6 months) and the R+ group (2.2 months, P = .03). In a multivariable analysis for progression-free survival, margin status was an independent predictor of survival (hazard ratio 3.13, P = .03).

CONCLUSIONS

From a thoracic surgery survey, 85% of surgeons use intraoperative frozen section margin analysis to guide surgical decision making during an esophagectomy. Analyzing patients with a positive margin discovered during esophagectomy suggests that esophageal cancer patients who can undergo re-resection to a negative margin have increased progression-free survival. The final margin appears to be related to progression-free survival.

Comparison of Laparoscopic Versus Open Surgical Management of Morgagni Hernia

BACKGROUND

Morgagni hernias are rare congenital diaphragmatic hernias that often do not become clinically significant until adulthood. The purpose of this study was to characterize the preoperative findings and describe surgical outcomes of Morgagni hernia repair based on operative approach.

METHODS

Charts of patients who underwent repair of a Morgagni hernia were retrospectively reviewed from 1987 to 2015. Medical records were reviewed for demographics, symptoms, comorbidities, surgical approach, hospital course, complications, and preoperative imaging.

RESULTS

Forty-three cases were identified, 23 male and 20 female. Median age was 50.4 years, and median body mass index was 33.1 kg/m². Most common presenting symptoms were respiratory (35.7%) and gastrointestinal (28.6%). Although 83.3% of cases were newly diagnosed, none required emergent repair. Preoperative imaging demonstrated an average hernia size of 8.2 cm. Surgical approaches included laparotomy (62.8%), laparoscopic (23.3%), and thoracotomy (14%). Primary hernia repair was most common (72%). Comparing laparotomy, thoracotomy, and laparoscopic approaches, mesh repair was more common with laparoscopy (p = 0.005), operative time was shortest with laparotomy (p = 0.029), and hospital length of stay was shortest with laparoscopy (p = 0.024). The most common complication was incisional/port site hernia, with no statistical significance between surgical approaches. There was one Morgagni hernia recurrence.

CONCLUSIONS

Morgagni hernias often present with respiratory and gastrointestinal symptoms and require repair. All cases in our series were repaired electively. Regardless of approach recurrence rate was low (2.3%) and complication rate was similar between laparoscopic, laparotomy, and thoracotomy. Given the shorter length of stay with similar recurrence rates, a laparoscopic approach is a viable option for repair of Morgagni hernia.

PP2A-activating drugs selectively eradicate TKI-resistant chronic myeloid leukemic stem cells

The success of tyrosine kinase inhibitors (TKIs) in treating chronic myeloid leukemia (CML) depends on the requirement for BCR-ABL1 kinase activity in CML progenitors. However, CML quiescent HSCs are TKI resistant and represent a BCR-ABL1 kinase-independent disease reservoir. Here we have shown that persistence of leukemic HSCs in BM requires inhibition of the tumor suppressor protein phosphatase 2A (PP2A) and expression--but not activity--of the BCR-ABL1 oncogene. Examination of HSCs from CML patients and healthy individuals revealed that PP2A activity was suppressed in CML compared with normal HSCs. TKI-resistant CML quiescent HSCs showed increased levels of BCR-ABL1, but very low kinase activity. BCR-ABL1 expression, but not kinase function, was required for recruitment of JAK2, activation of a JAK2/β-catenin survival/self-renewal pathway, and inhibition of PP2A. PP2A-activating drugs (PADs) markedly reduced survival and self-renewal of CML quiescent HSCs, but not normal quiescent HSCs, through BCR-ABL1 kinase-independent and PP2A-mediated inhibition of JAK2 and β-catenin. This led to suppression of human leukemic, but not normal, HSC/progenitor survival in BM xenografts and interference with long-term maintenance of BCR-ABL1-positive HSCs in serial transplantation assays. Targeting the JAK2/PP2A/β-catenin network in quiescent HSCs with PADs (e.g., FTY720) has the potential to treat TKI-refractory CML and relieve lifelong patient dependence on TKIs.

Sphingosine analogue drug FTY720 targets I2PP2A/SET and mediates lung tumour suppression via activation of PP2A-RIPK1-dependent necroptosis

Mechanisms that alter protein phosphatase 2A (PP2A)-dependent lung tumour suppression via the I2PP2A/SET oncoprotein are unknown. We show here that the tumour suppressor ceramide binds I2PP2A/SET selectively in the nucleus and including its K209 and Y122 residues as determined by molecular modelling/simulations and site-directed mutagenesis. Because I2PP2A/SET was found overexpressed, whereas ceramide was downregulated in lung tumours, a sphingolipid analogue drug, FTY720, was identified to mimick ceramide for binding and targeting I2PP2A/SET, leading to PP2A reactivation, lung cancer cell death, and tumour suppression in vivo. Accordingly, while molecular targeting of I2PP2A/SET by stable knockdown prevented further tumour suppression by FTY720, reconstitution of WT-I2PP2A/SET expression restored this process. Mechanistically, targeting I2PP2A/SET by FTY720 mediated PP2A/RIPK1-dependent programmed necrosis (necroptosis), but not by apoptosis. The RIPK1 inhibitor necrostatin and knockdown or genetic loss of RIPK1 prevented growth inhibition by FTY720. Expression of WT- or death-domain-deleted (DDD)-RIPK1, but not the kinase-domain-deleted (KDD)-RIPK1, restored FTY720-mediated necroptosis in RIPK1^−/− MEFs. Thus, these data suggest that targeting I2PP2A/SET by FTY720 suppresses lung tumour growth, at least in part, via PP2A activation and necroptosis mediated by the kinase domain of RIPK1.

Off-target function of the Sonic hedgehog inhibitor cyclopamine in mediating apoptosis via nitric oxide-dependent neutral sphingomyelinase 2/ceramide induction

Sonic hedgehog (SHh) signaling is important in the pathogenesis of various human cancers, such as medulloblastomas, and it has been identified as a valid target for anticancer therapeutics. The SHh inhibitor cyclopamine induces apoptosis. The bioactive sphingolipid ceramide mediates cell death in response to various chemotherapeutic agents; however, ceramide's roles/mechanisms in cyclopamine-induced apoptosis are unknown. Here, we report that cyclopamine mediates ceramide generation selectively via induction of neutral sphingomyelin phosphodiesterase 3, SMPD3 (nSMase2) in Daoy human medulloblastoma cells. Importantly, short interfering RNA-mediated knockdown of nSMase2 prevented cyclopamine-induced ceramide generation and protected Daoy cells from drug-induced apoptosis. Accordingly, ectopic wild-type N-SMase2 caused cell death, compared with controls, which express the catalytically inactive N-SMase2 mutant. Interestingly, knockdown of smoothened (Smo), a target protein for cyclopamine, or Gli1, a downstream signaling transcription factor of Smo, did not affect nSMase2. Mechanistically, our data showed that cyclopamine induced nSMase2 and cell death selectively via increased nitric oxide (NO) generation by neuronal-nitric oxide synthase (n-NOS) induction, in Daoy medulloblastoma, and multiple other human cancer cell lines. Knockdown of n-NOS prevented nSMase2 induction and cell death in response to cyclopamine. Accordingly, N-SMase2 activity-deficient skin fibroblasts isolated from homozygous fro/fro (fragilitas ossium) mice exhibited resistance to NO-induced cell death. Thus, our data suggest a novel off-target function of cyclopamine in inducing apoptosis, at least in part, by n-NOS/NO-dependent induction of N-SMase2/ceramide axis, independent of Smo/Gli inhibition.

Alteration of ceramide synthase 6/C16-ceramide induces activating transcription factor 6-mediated endoplasmic reticulum (ER) stress and apoptosis via perturbation of cellular Ca2+ and ER/Golgi membrane network

Mechanisms that regulate endoplasmic reticulum (ER) stress-induced apoptosis in cancer cells remain enigmatic. Recent data suggest that ceramide synthase1-6 (CerS1-6)-generated ceramides, containing different fatty acid chain lengths, might exhibit distinct and opposing functions, such as apoptosis versus survival in a context-dependent manner. Here, we investigated the mechanisms involved in the activation of one of the major ER stress response proteins, ATF-6, and subsequent apoptosis by alterations of CerS6/C(16)-ceramide. Induction of wild type (WT), but not the catalytically inactive mutant CerS6, increased tumor growth in SCID mice, whereas siRNA-mediated knockdown of CerS6 induced ATF-6 activation and apoptosis in multiple human cancer cells. Down-regulation of CerS6/C(16)-ceramide, and not its further metabolism to glucosylceramide or sphingomyelin, activated ATF-6 upon treatment with ER stress inducers tunicamycin or SAHA (suberoylanilide hydroxamic acid). Induction of WT-CerS6 expression, but not its mutant, or ectopic expression of the dominant-negative mutant form of ATF-6 protected cells from apoptosis in response to CerS6 knockdown and tunicamycin or SAHA treatment. Mechanistically, ATF-6 activation was regulated by a concerted two-step process involving the release of Ca(2+) from the ER stores ([Ca(2+)](ER)), which resulted in the fragmentation of Golgi membranes in response to CerS6/C(16)-ceramide alteration. This resulted in the accumulation of pro-ATF-6 in the disrupted ER/Golgi membrane network, where pro-ATF6 is activated. Accordingly, ectopic expression of a Ca(2+) chelator calbindin prevented the Golgi fragmentation, ATF-6 activation, and apoptosis in response to CerS6/C(16)-ceramide down-regulation. Overall, these data suggest a novel mechanism of how CerS6/C(16)-ceramide alteration activates ATF6 and induces ER-stress-mediated apoptosis in squamous cell carcinomas.

Results of a phase II trial of gemcitabine plus doxorubicin in patients with recurrent head and neck cancers: serum C₁₈-ceramide as a novel biomarker for monitoring response

PURPOSE

Here we report a phase II clinical trial, which was designed to test a novel hypothesis that treatment with gemcitabine (GEM)/doxorubicin (DOX) would be efficacious via reconstitution of C(18)-ceramide signaling in head and neck squamous cell carcinoma (HNSCC) patients for whom first-line platinum-based therapy failed.

EXPERIMENTAL DESIGN

Patients received GEM (1,000 mg/m²) and DOX (25 mg/m²) on days 1 and 8, every 21 days, until disease progression. After completion of 2 treatment cycles, patients were assessed radiographically, and serum samples were taken for sphingolipid measurements.

RESULTS

We enrolled 18 patients in the trial, who were evaluable for toxicity, and 17 for response. The most common toxicity was neutropenia, observed in 9 of 18 patients, and there were no major nonhematologic toxicities. Of the 17 patients, 5 patients had progressive disease (PD), 1 had complete response (CR), 3 exhibited partial response (PR), and 8 had stable disease (SD). The median progression-free survival was 1.6 months (95% CI: 1.4-4.2) with a median survival of 5.6 months (95% CI: 3.8-18.2). Remarkably, serum sphingolipid analysis revealed significant differences in patterns of C₁₈-ceramide elevation in patients with CR/PR/SD in comparison with patients with PD, indicating the reconstitution of tumor suppressor ceramide generation by GEM/DOX treatment.

CONCLUSIONS

Our data suggest that the GEM/DOX combination could represent an effective treatment for some patients with recurrent or metastatic HNSCC, and that serum C₁₈-ceramide elevation might be a novel serum biomarker of chemotherapy response.

Sphingolipids and cancer: ceramide and sphingosine-1-phosphate in the regulation of cell death and drug resistance

Sphingolipids have emerged as bioeffector molecules, controlling various aspects of cell growth and proliferation in cancer, which is becoming the deadliest disease in the world. These lipid molecules have also been implicated in the mechanism of action of cancer chemotherapeutics. Ceramide, the central molecule of sphingolipid metabolism, generally mediates antiproliferative responses, such as cell growth inhibition, apoptosis induction, senescence modulation, endoplasmic reticulum stress responses and/or autophagy. Interestingly, recent studies suggest de novo-generated ceramides may have distinct and opposing roles in the promotion/suppression of tumors, and that these activities are based on their fatty acid chain lengths, subcellular localization and/or direct downstream targets. For example, in head and neck cancer cells, ceramide synthase 6/C(16)-ceramide addiction was revealed, and this was associated with increased tumor growth, whereas downregulation of its synthesis resulted in ER stress-induced apoptosis. By contrast, ceramide synthase 1-generated C(18)-ceramide has been shown to suppress tumor growth in various cancer models, both in situ and in vivo. In addition, ceramide metabolism to generate sphingosine-1-phosphate (S1P) by sphingosine kinases 1 and 2 mediates, with or without the involvement of G-protein-coupled S1P receptor signaling, prosurvival, angiogenesis, metastasis and/or resistance to drug-induced apoptosis. Importantly, recent findings regarding the mechanisms by which sphingolipid metabolism and signaling regulate tumor growth and progression, such as identifying direct intracellular protein targets of sphingolipids, have been key for the development of new chemotherapeutic strategies. Thus, in this article, we will present conclusions of recent studies that describe opposing roles of de novo-generated ceramides by ceramide synthases and/or S1P in the regulation of cancer pathogenesis, as well as the development of sphingolipid-based cancer therapeutics and drug resistance.

Direct interaction between the inhibitor 2 and ceramide via sphingolipid-protein binding is involved in the regulation of protein phosphatase 2A activity and signaling

In this study, the inhibitor 2 of protein phosphatase 2A (I2PP2A) was identified in vitro and in situ as a ceramide-binding protein, which exhibits stereoisomer specificity and fatty acid chain length preference. Site- directed mutagenesis coupled with structural details of I2PP2A suggested that VIK 207-209 residues localized on helix 7 are important for ceramide binding and single mutation of K209D altered this interaction. Notably, I2PP2A-ceramide binding decreased the association between PP2A and the inhibitor, preventing the inhibition of PP2A activity in vitro. In addition, studies in A549 human lung cancer cells revealed that ceramide mediates c-Myc degradation via its PP2A-dependent dephosphorylation at S62, and treatment with okadaic acid and expression of c-Myc mutants with S62A or S62D conversions resulted in resistance to ceramide-mediated degradation. Importantly, whereas down-regulation of I2PP2A enhanced PP2A-mediated c-Myc degradation in response to ceramide, ectopic expression of wild-type I2PP2A but not of its K209D mutant protected this degradation in A549 cells. Moreover, expression of wild-type I2PP2A prevented the growth-inhibitory effects of ceramide both against A549 cells and xenograft-driven tumors in situ and in vivo compared with that in controls. Thus, these results suggest that direct interaction of I2PP2A with ceramide plays important biological roles via the regulation of PP2A activity and signaling, which in turn control ceramide-mediated degradation of c-Myc and antiproliferation.

Homoleptic Cobalt and Copper Phenolate A2[M(OAr)4] Compounds: The Effect of Phenoxide Fluorination

Two series of homoleptic phenolate complexes with fluorinated aryloxide ligands A2[M(OAr)4] with M=Co2+ or Cu2+, OAr-=(OC6F5)- (OArF) or [3,5-OC6H3(CF3)2]- (OAr'), A+=K (18-crown-6)+, Tl+, Ph4P+, Et3HN+, or Me4N+ have been synthesized. Two related complexes with nonfluorinated phenoxide ligands have been synthesized and studied in comparison to the fluorinated aryloxides demonstrating the dramatic structural changes effected by modification of OPh to OAr(F). The compounds [K(18-crown-6)]2[Cu(OArF)4], 1a; [K(18-crown-6)]2[Cu(OAr')4], 1b; [Tl2Cu(OArF)4], 2a; [Tl2Cu(OAr')4], 2b; (Ph4P)2[Cu(OArF)4], 3; (nBu4N)2[Cu(OArF)4], 4; (HEt3N)2[Cu(OArF)4], 5; [K(18-crown-6)]2[Cu2(mu2-OC6H5)2(OC6H5)4], 6; [K(18-crown-6)]2[Co(OArF)4], 7a; [(18-crown-6)]2[Co(OAr')4], 7b; [Tl2Co(OArF)4], 8a; [Tl2Co(OAr')4], 8b; (Me4N)2[Co(OArF)4], 9; [Cp2Co]2[Co(OAr')4], 10; and [(18-crown-6)])[Co2(mu2-OC6H5)2(OC6H5)4], 11, have been characterized with UV-vis and multinuclear NMR spectroscopy and solution magnetic moment studies. Cyclic voltammetry was used to study 1a, 1b, 7a, and 7b. X-ray crystallography was used to characterize 1b, 3, 4, 5, 6, 7a, 7b, 10, and 11. The related [MX4]2- compound (Ph4P)2[Co(OArF)2Cl2], 12, has also been synthesized and characterized spectroscopically, as well as with conductivity and single-crystal X-ray diffraction. Use of fluorinated aryloxides permits synthesis and isolation of the mononuclear, homoleptic phenolate anions in good yield without oligomerized side products. The reaction conditions that result in homoleptic 1a and 7a with OArF upon changing the ligand to OPh result in mu2-OPh bridging phenoxides and the dimeric complexes 6 and 11. The [M(OArF)4]2- and [M(OAr')4]2- anions in 1a, 1b, 3, 4, 5, 7a, 7b, 9, and 10 demonstrate that stable, isolable homoleptic phenolate anions do not need to be coordinatively or sterically saturated and can be achieved by increasing the electronegativity of the ligand.