Immunosuppressive TOR kinase inhibitor everolimus (RAD) suppresses growth of cells derived from posttransplant lymphoproliferative disorder at allograft-protecting doses

The IPTA Nashville consensus conference on post-transplant lymphoproliferative disorders after solid organ transplantation in children: IV-consensus guidelines for the management of post-transplant lymphoproliferative disorders in children and adolescents

The International Pediatric Transplant Association convened an expert consensus conference to assess current evidence and develop recommendations for various aspects of care relating to post-transplant lymphoproliferative disorders (PTLD) after pediatric solid organ transplantation. This report addresses the outcomes of deliberations by the PTLD Management Working Group. A strong recommendation was made for reduction in immunosuppression as the first step in management. Similarly, strong recommendations were made for the use of the anti-CD20 monoclonal antibody (rituximab) as was the case for chemotherapy in selected scenarios. In some scenarios, there is uncoupling of the strength of the recommendations from the available evidence in situations where such evidence is lacking but collective clinical experiences drive decision-making. Of note, there are no large, randomized phase III trials of any treatment for PTLD in the pediatric age group. Current gaps and future research priorities are highlighted.

Everolimus treatment enhances inhibitory immune checkpoint molecules' expression in monocyte-derived dendritic cells

BACKGROUND

Antigen-specific T-cell immunity is provided by dendritic cells (DCs), which are specialized antigen-presenting cells. Furthermore, they establish a link between innate and adaptive immune responses. Currently, DC modification is a new approach for the therapy of several disorders. During solid organ transplantation, Everolimus, which is a mammalian target of rapamycin (mTOR) inhibitor, was initially utilized to suppress the immune system's functionality. Due to the intervention of Everolimus in various signaling pathways in cells and its modulatory properties on the immune system, this study aims to investigate the effect of treatment with Everolimus on the maturation and expression of immune checkpoint genes in monocyte-derived DCs.

METHODS

To isolate monocytes from PBMCs, the CD14 marker was used via the MACS method. Monocytes were cultured and induced to differentiate into monocyte-derived DCs by utilizing GM-CSF and IL-4 cytokines. On the fifth day, immature DCs were treated with Everolimus and incubated for 24 h. On the sixth day, the flow cytometry technique was used to investigate the effect of Everolimus on the phenotypic characteristics of DCs. In the end, the expression of immune checkpoint genes in both the Everolimus-treated and untreated DCs groups was assessed using the real-time PCR method.

RESULTS

The findings of this research demonstrated that the administration of Everolimus to DCs led to a notable rise in human leukocyte antigen (HLA)-DR expression and a decrease in CD11c expression. Furthermore, there was a significant increase in the expression of immune checkpoint molecules, namely CTLA-4, VISTA, PD-L1, and BTLA, in DCs treated with Everolimus.

CONCLUSION

The findings of this study show that Everolimus can target DCs and affect their phenotype and function in order to shift them toward a partially tolerogenic state. However, additional research is required to gain a comprehensive understanding of the precise impact of Everolimus on the activation status of DCs.

Relative carcinogenicity of tacrolimus vs mycophenolate after solid organ transplantation and its implications for liver transplant care

BACKGROUND

De novo malignancy is a leading cause of late morbidity and mortality in liver transplant recipients. Cumulative immunosuppression has been shown to contribute to post-transplant malignancy (PTM) risk. There is emerging evidence on the differential carcinogenic risk profile of individual immunosuppressive drugs, independent of the net effect of immunosuppression. Calcineurin inhibitors such as tacrolimus may promote tumourigenesis, whereas mycophenolic acid (MPA), the active metabolite of mycophenolate mofetil, may limit tumour progression. Liver transplantation (LT) is relatively unique among solid organ transplantation in that immunosuppression monotherapy with either tacrolimus or MPA is often achievable, which makes careful consideration of the risk-benefit profile of these immunosuppression agents particularly relevant for this cohort. However, there is limited clinical data on this subject in both LT and other solid organ transplant recipients.

AIM

To investigate the relative carcinogenicity of tacrolimus and MPA in solid organ transplantation.

METHODS

A literature search was conducted using MEDLINE and Embase databases using the key terms "solid organ transplantation", "tacrolimus", "mycophenolic acid", and "carcinogenicity", in order to identify relevant articles published in English between 1st January 2002 to 11th August 2022. Related terms, synonyms and explosion of MeSH terms, Boolean operators and truncations were also utilised in the search. Reference lists of retrieved articles were also reviewed to identify any additional articles. Excluding duplicates, abstracts from 1230 records were screened by a single reviewer, whereby 31 records were reviewed in detail. Full-text articles were assessed for eligibility based on pre-specified inclusion and exclusion criteria.

RESULTS

A total of 6 studies were included in this review. All studies were large population registries or cohort studies, which varied in transplant era, type of organ transplanted and immunosuppression protocol used. Overall, there was no clear difference demonstrated between tacrolimus and MPA in de novo PTM risk following solid organ transplantation. Furthermore, no study provided a direct comparison of carcinogenic risk between tacrolimus and MPA monotherapy in solid organ transplantation recipients.

CONCLUSION

The contrasting carcinogenic risk profiles of tacrolimus and MPA demonstrated in previous experimental studies, and its application in solid organ transplantation, is yet to be confirmed in clinical studies. Thus, the optimal choice of immunosuppression drug to use as maintenance monotherapy in LT recipients is not supported by a strong evidence base and remains unclear.

Experience with the mTOR Inhibitor Everolimus in Pediatric Liver Graft Recipients

INTRODUCTION

Immunosuppression after pediatric liver transplantation remains a major challenge. MTOR inhibitors provide a promising therapeutic approach in combination with reduced CNI after transplantation. However, there are still few data regarding their use in children.

PATIENTS

We analyzed 37 patients with a median age of 10 years, who received Everolimus for one or more of the following indications: I = chronic graft dysfunction (n = 22); II = progressive renal impairment (n = 5); III = non-tolerable side effects with previous immunosuppressive medication (n = 6); and IV = malignancies (n = 10). The median follow-up time was 36 months.

RESULTS

Patient survival was 97%, and graft survival 84%, respectively. Stabilization of graft function was observed in 59% in subgroup 1, with 18.2% ultimately requiring retransplantation. No patient in subgroup IV developed recurrence of his primary tumor or PTLD by the endpoint of the study. Side effects were observed in 67.5% of the study patients, with infections being the most frequent (n = 20; 54.1%). There were no relevant effects on growth and development.

CONCLUSION

Everolimus seems to be a treatment option in selected pediatric liver graft recipients for whom other regimens are not suitable. Overall, the efficacy was good and the side effect profile appeared to be acceptable.

Management of Epstein-Barr Virus Infection and Post-Transplant Lymphoproliferative Disorder in Pediatric Liver Transplantation

With the advancement of immunosuppressive strategies, the outcome of liver transplantation during childhood has dramatically improved. On the other hand, Epstein–Barr virus (EBV) infection and associated post-transplant lymphoproliferative diseases (PTLD), such as malignant lymphoma, are serious complications that contribute to morbidity and mortality, and are still an important issue today. Recently, an early diagnosis by quantitative PCR and PET-CT testing, and treatment with rituximab (an anti-CD20 antibody) has been established, and long-term remission has been achieved in many cases. However, the optimal immunosuppression protocol after remission of PTLD needs to be determined, and it is hoped that a treatment for refractory PTLD (e.g., PTL-NOS) will be proposed.

Survival of Post-Transplant Lymphoproliferative Disorder after Kidney Transplantation in Patients under Rapamycin Treatment

Background: One of the important causes of mortality and morbidity in kidney transplanted patients is Post Transplant Lymphoproliferative Disease (PTLD), which is due to immunosuppression therapy and viral activity. It seems that Rapamycin, with dual antineoplastic and immunosuppressive effects, may have a pivotal role in the treatment of PTLD patients and preserving transplanted kidneys.

Methods and Materials: Twenty patients with PTLD were enrolled. Immunosuppressive therapy was reduced or ceased, and Rapamycin was initiated at the time of PTLD diagnosis. We evaluated the effects of switching immunosuppressive drugs to Rapamycin on graft status, the response of tumor, and 6, 12 months, and 5-year survival in patients.

Results: PTLD remission was achieved in 14 patients, while six patients died; no relapse was detected in recovered patients. The median of PTLD free time was 25 months, and the mean overall survival in patients with PTLD treated by Rapamycin was 84.8 (95% CI=61.3-108.23).The five-year survival rate was 67%, 12 months survival was 73.8%, and six months' survival was 80%. The response rate to Rapamycin and immunosuppression reduction alone was 46.6%. Four out of 13 Diffuse Large B-Cell Lymphoma patients achieved a complete response just only after the reduction of immunosuppressive drugs and the consumption of Rapamycin.

Conclusion: The present study demonstrated the effectiveness of conversion from immunosuppressive medication, particularly of Calcineurin inhibitors to Rapamycin in PTLD patients. However, more research is needed to confirm the Rapamycin effect on patients with PTLD.

Chronic everolimus treatment of high-fat diet mice leads to a reduction in obesity but impaired glucose tolerance

Everolimus, which inhibits mTOR kinase activity and is clinically used in graft rejection treatment, may have a two‐sided influence on metabolic syndrome; its role in obesity and hyperglycemic in animals and humans, however, has been explored insufficiently. This study further determined how continual everolimus treatment affects glucose homeostasis and body weight control in C57BL6/J mice with obesity. An obesity mouse model was developed by administering a high‐fat diet (HFD) to C57BL6/J mice over 12 weeks. The experimental group, while continuing their HFD consumption, were administered everolimus daily for 8 weeks. Metabolic parameters, glucose tolerance, fatty liver score, endocrine profile, insulin sensitivity index (ISI), insulin resistance (IR) index, and Akt phosphorylation, GLUT4, TNF‐α, and IL‐1 levels were measured in vivo. Compared with the control group, the everolimus group gained less body weight and had smaller adipocytes and lower fat pad weight; triglyceride (serum and hepatic), patatin‐like phospholipase domain‐containing 3, and fatty acid synthase levels; fatty liver scores; and glucose tolerance test values—all despite consuming more food. However, the everolimus group exhibited decreased ISI and muscle Akt phosphorylation and GLUT4 expression as well as impaired glucose tolerance and serum TNF‐α and IL‐1β levels—even when insulin levels were high. In conclusion, continual everolimus treatment may lead to diabetes with glucose intolerance and IR.

Association between infectious event and de novo malignancy after heart transplantation

The aim of the study was to investigate the incidence of and risk factors for de novo malignancy after heart transplantation (HTx) in a single center. We assessed 102 consecutive patients who received HTx and were followed-up in our center regularly for > 1 year from June 2006 to May 2018. We investigated the incidence of and risk factors for de novo malignancy. The cumulative incidence of each malignancy type during the follow-up period was one (0.98%) for skin cancer, four (3.92%) for nonskin solid organ cancer, and six (5.88%) for posttransplant lymphoproliferative disorder (PTLD). The percentage of patients with more than one infectious event ≤ 1 year after HTx was higher in the malignancy group than in the non-malignancy group. Furthermore, Kaplan-Meier analysis revealed that the incidence rate of infectious events was higher in patients with malignancies than in those without (log-rank P < 0.001). After dividing malignancies into a PTLD group and a solid organ malignancy group, we found that negative Epstein-Barr virus serostatus, cytomegalovirus-positive antigenemia, and the occurrence of any viral or gastrointestinal infectious event at ≤ 1 year were more frequent in patients with PTLD than in patients without it. The survival rate was significantly lower for patients with solid organ malignancy than for patients without malignancy. In conclusion, there was a correlation between infectious events and de novo malignancy, particularly in patients with PTLD. We should confirm this finding by conducting a larger cohort study.

Safety and Efficacy of Everolimus Rescue Treatment After Pediatric Living Donor Liver Transplantation

PURPOSE

Everolimus (EVR) is a derivative of sirolimus with a similar mechanism of action. The safety and efficacy of EVR after pediatric living donor liver transplantation (LDLT) are currently unknown. The purpose of this study was to examine the safety and efficacy of EVR as rescue therapy after pediatric LDLT.

METHODS

This study included patients younger than 19 years of age who received EVR after LDLT at our institution. EVR was administered as rescue treatment in addition to tacrolimus. In 21 patients, EVR dose, trough level, outcomes, and adverse effects were assessed.

RESULTS

Original diseases of patients consisted of biliary atresia (n = 11), Alagille syndrome (n = 3), fulminant hepatitis (n = 3), hepatoblastoma (n = 2), and other (n = 2). Mean age at transplant was 2.0 years (range 0.6-6.2 years). Mean age at initial EVR administration was 8.0 years (range 0.9-18.9 years). Indications for EVR use were graft fibrosis (n = 8), refractory acute cellular rejection (n = 5), renal sparing (n = 4), hepatoblastoma (n = 2), and chronic rejection (CR) (n = 2). Mean duration of administration was 17.1 months (range 2.1-60.4 months). Mean dose was 0.5 mg/m² twice daily. Mean EVR trough level was 2.5 ng/mL (range 1.5-5.0 ng/mL). Liver function improved and fibrosis did not progress in all patients with CR. However, 14 patients (67%) experienced adverse effects that required EVR dose reduction or discontinuation.

CONCLUSION

EVR is tolerable for pediatric patients after LDLT with dose adjustment. EVR had a certain effect to relieve progression on CR. Further follow-up is required.

Remission of Epstein-Barr virus-positive post-transplant lymphoproliferative disorder by conversion to everolimus in a kidney transplant recipient

Post-transplant lymphoproliferative disorder (PTLD) is a fatal complication of transplantation. There is no clear consensus on the treatment of PTLD. In most cases, the pathogenetic mechanism of PTLD involves the Epstein-Barr virus (EBV). We report the case of an elderly kidney transplant recipient who developed EBV-positive monomorphic T-cell PTLD 14 years after transplantation. Conversion from conventional immunosuppressants to everolimus induced complete remission of PTLD accompanied by a decrease in blood EBV-DNA level without chemotherapy.

Dual blockade of the PI3K/Akt/mTOR pathway inhibits posttransplant Epstein-Barr virus B cell lymphomas and promotes allograft survival

Posttransplant lymphoproliferative disorder (PTLD) is a serious complication of organ transplantation that often manifests as Epstein-Barr virus (EBV)-associated B cell lymphomas. Current treatments for PTLD have limited efficacy and can be associated with graft rejection or systemic toxicities. The mTOR inhibitor, rapamycin, suppresses tumor growth of EBV+ B cell lymphoma cells in vitro and in vivo; however, the efficacy is limited and clinical benefits of mTOR inhibitors for PTLD are variable. Here, we show constitutive activation of multiple nodes within the PI3K/Akt/mTOR pathway in EBV+ PTLD-derived cell lines. Inhibition of either PI3K or Akt, with specific inhibitors CAL-101 and MK-2206, respectively, diminished growth of EBV+ B cell lines from PTLD patients in a dose-dependent manner. Importantly, rapamycin combined with CAL-101 or MK-2206 had a synergistic effect in suppressing cell growth as determined by IC₅₀ isobolographic analysis and Loewe indices. Moreover, these combinations were significantly more effective than rapamycin alone in inhibiting tumor xenograft growth in NOD-SCID mice. Finally, both CAL-101 and MK-2206 also prolonged survival of heterotopic cardiac allografts in C57BL/6 mice. Thus, combination therapy with rapamycin and a PI3K inhibitor, or an Akt inhibitor, can be an efficacious treatment for EBV-associated PTLD, while simultaneously promoting allograft survival.

Everolimus Rescue Treatment for Chronic Rejection After Pediatric Living Donor Liver Transplantation: 2 Case Reports

Chronic rejection (CR) remains a challenging complication after liver transplantation. Everolimus, which is a mammalian target of rapamycin inhibitor, has an anti-fibrosis effect. We report here the effect of everolimus on CR. Case 1 was a 7-year-old girl who underwent living donor liver transplantation (LDLT) shortly after developing fulminant hepatitis at 10 months of age. Liver function tests (LFTs) did not improve after transplantation despite treatment with tacrolimus + mycophenolate mofetil (MMF). Antithymoglobulin (ATG) and steroid pulse therapy were also ineffective. The patient was diagnosed with CR, and everolimus was started with a target trough level of about 5 ng/mL. LFTs improved and pathological examination showed no progression of hepatic fibrosis. Case 2 was a 10-year-old girl with Alagille syndrome who underwent LDLT at 1 year of age. She had biopsy-proven acute cellular rejection with prolonged LFT abnormalities beginning 3 years after transplantation. She was treated with steroid pulse therapy, followed by MMF, tacrolimus, and prednisolone. Her condition did not improve, even after subsequent ATG administration. CR was suspected based on liver biopsy in the fourth postoperative year, and everolimus was introduced. The target trough level was around 5 ng/mL, but was reduced to 3 ng/mL due to stomatitis. Four years have passed since the initiation of everolimus, and LFTs are stable with no progression of liver biopsy fibrosis. We describe 2 cases in which everolimus was administered for CR. In both cases, LFTs improved and fibrosis did not progress, suggesting that everolimus is an effective treatment for CR after LDLT.

The future of cardiac transplantation

The first human-to-human heart transplant was performed 50 years ago in 1967. Heart transplantation has now entered an era of tremendous growth and innovation. The future of heart transplantation is bright with the advent of newer immunosuppressive medications and strategies that may even result in tolerance. Much of this progress in heart transplant medicine is predicated on a better understanding of acute and chronic rejection pathways through basic science studies. The future will also include personalized medicine where genomics and molecular science will dictate customized treatment for optimal outcomes. The introduction of mechanical circulatory support (MCS) devices has changed the landscape for patients with severe heart failure to stabilize the most ill patient and make them better candidates for heart transplant. As ex vivo preservation takes hold, we may witness an expansion of the donor pool through the use of donation after cardiac death (DCD) donors. In addition, further geographical donor heart sharing through ex vivo preservation may further decrease waitlist mortality by enabling longer distance donor hearts to be allocated for the sickest waitlist patient. It is no doubt an exciting time to be involved in the field of heart transplantation. In this perspective, we will summarize the present state of heart transplantation and discuss various innovations that are being pursued.

Posttransplant lymphoproliferative disorders in kidney transplant recipients: a retrospective cohort analysis over two decades in Hong Kong

Objective

To characterize the posttransplant lymphoproliferative disorders (PTLD) including the Epstein-Barr virus (EBV) status, histological subgroups, site of occurrence and the clinical outcome in the Chinese kidney transplant recipients.

Methods

A retrospective cohort study of 1, 227 adult kidney transplant recipients who were followed up in two transplant centers in Hong Kong over two decades.

Results

23 (1.9%) patients developed PTLD. Median duration from transplant to PTLD was 104 (5-252) months. Six patients (26.1%) had early PTLD and 17 (73.9%) had late PTLD. Ten (43%) developed PTLD >10 years after transplant. All patients in early PTLD group were EBV-positive. In the late PTLD group, 60% were EBV-negative and 40% EBV-positive. More than 90% of cases were monomorphic PTLD with majority being diffuse large B cell lymphoma. Bone marrow was the most common extranodal site. The overall treatment response rate was 52.2 %. None of the patients developed rejection or relapse after PTLD. At a median follow-up of 9 (1-79) months after PTLD, 18 patients died. Patient survival was 48% at 1 year and 30% at 3 years and death-censored allograft survival was 82% at 1year and 73% at 3 years.

Conclusion

Late PTLD is common. Careful adjustment of immunosuppression, close monitoring of patients, increased awareness and early detection of the disease are essential.

Clinical Utility of Epstein-Barr Virus Viral Load Monitoring and Risk Factors for Posttransplant Lymphoproliferative Disorders After Kidney Transplantation: A Single-Center, 10-Year Observational Cohort Study

Background

Posttransplant lymphoproliferative disease (PTLD) is an important cause of morbidity and mortality in solid organ transplants. Epstein Barr virus (EBV) plays a major role in PTLD development. Guidelines recommend EBV viral load (VL) monitoring in high-risk populations in the first year.

Methods

Retrospective observational study in all adult patients who had at least 1 EBV-VL performed in the postkidney transplant (KT) period from January 2005 to December 2014 at the Policlinico Modena Hospital. We compared patients with negative EBV-DNA to patients with positive EBV-DNA and we described PTLD developed in the study period.

Results

One hundred ninety (36.3%) KT patients of 523 were screened for EBV-DNA with 796 samples. One hundred twenty-eight (67.4%) of 190 tested patients presented at least 1 positive sample for EBV. Older age, the use of sirolimus, everolimus, and steroids were associated with EBV-DNA positivity in the univariate analysis. Nine (1.7%) of 523 patients had PTLD. Incidence rate of PTLD in the KT cohort was 0.19/100 person year follow-up (95% confidence interval, 0.09-0.37). One of 9 patients developed early PTLD and was a high-risk patient. Only this PTLD case was positive for EBV. No PTLD case had an EBV-VL superior to 4000 copies/mL.

Conclusions

Our results suggest that the keystone of PTLD diagnosis is the clinical suspicion. Our study suggests that, in line with guidelines, EBV-VL assays may be avoided in low-risk patients in the absence of a strong clinical PTLD suspicion without increasing patients' risk of developing PTLD. This represents a safe and cost-saving clinical strategy for our center.

Immunosuppression for in vivo research: state-of-the-art protocols and experimental approaches

Almost every experimental treatment strategy using non-autologous cell, tissue or organ transplantation is tested in small and large animal models before clinical translation. Because these strategies require immunosuppression in most cases, immunosuppressive protocols are a key element in transplantation experiments. However, standard immunosuppressive protocols are often applied without detailed knowledge regarding their efficacy within the particular experimental setting and in the chosen model species. Optimization of such protocols is pertinent to the translation of experimental results to human patients and thus warrants further investigation. This review summarizes current knowledge regarding immunosuppressive drug classes as well as their dosages and application regimens with consideration of species-specific drug metabolization and side effects. It also summarizes contemporary knowledge of novel immunomodulatory strategies, such as the use of mesenchymal stem cells or antibodies. Thus, this review is intended to serve as a state-of-the-art compendium for researchers to refine applied experimental immunosuppression and immunomodulation strategies to enhance the predictive value of preclinical transplantation studies.

Posttransplant Malignancy

In the past few decades, great advances have been made in the field of solid-organ transplantation. A greater understanding of immune system function, the development of modern immunosuppression, and advancements in surgical technique have led to marked improvements in both recipient and graft survivals, as well as recipients' quality of life. However, improved survival rates have also led to prolonged exposure to chronic immunosuppression, which increases the risk for the development of posttransplant malignancies. In addition, older transplant candidates are being considered, carrying with them the increased likelihood of pre-existing malignancy. Consequently, the potential risk of posttransplant malignancy must be considered. Moreover, as long-term transplant survivors continue to age, posttransplant malignancies will be seen more frequently. This review presents the more commonly encountered posttransplant malignancies and the measures that are currently being utilized to prevent and treat them.

Epstein-Barr Virus-Positive Posttransplant Lymphoproliferative Disease After Solid Organ Transplantation: Pathogenesis, Clinical Manifestations, Diagnosis, and Management

Posttransplant lymphoproliferative disease (PTLD) is a potentially fatal complication after (solid organ) transplantation, which is highly associated with Epstein-Barr virus (EBV). The EBV-specific cytotoxic T cell response that is essential in controlling the virus in healthy individuals is suppressed in transplant recipients using immunosuppressive drugs. A primary EBV infection in EBV-seronegative patients receiving an EBV-seropositive donor organ or a reactivation in those who are already latently infected pretransplantation can lead to uninhibited growth of EBV-infected B cells and subsequently to PTLD. Effective preventive strategies, such as vaccines and antiviral agents, are lacking. Because not every transplant recipient with increasing EBV viral load develops PTLD, it is hard to decide how intensively these patients should be monitored and how and when a preemptive intervention should take place. There is a need for other tools to help predict the development of PTLD in patients at risk to make timing and strategy of preemptive intervention easier and more reliable.

The cornerstone of the treatment of patients with PTLD is restoring the host's immunity by reduction of immunosuppressive drug therapy. American and British guidelines recommend to add rituximab monotherapy or rituximab in combination with cyclophosphamide, doxorubicin, vincristine, and prednisolone, depending on histology and clinical characteristics. Although response to these therapies is good, toxicity is a problem, and PTLD still has a relatively high mortality rate. An evolving therapy, especially in PTLD occurring in allogeneic stem cell transplantation, is restoring the host's immune response with infusion of EBV-specific cytotoxic T cells. This may also play a role in the future in both prevention and treatment of PTLD in SOT.

Post-transplantation malignancies: here today, gone tomorrow?

From the early days of transplantation onwards, increased cancer development in transplant recipients, who require immunosuppression to avoid graft rejection, has been recognized. Registry data indicate that approximately 10-30% of deaths are attributed to post-transplant malignancy, with an upward trend in this incidence as more patients have been exposed to chronic lifelong immunosuppression. In this Review, the overall incidence and most frequent types of cancer encountered are summarized, along with information about which transplant recipients are at the greatest risk of malignancy. Reasons for why differences exist in susceptibility to cancer in this patient population are examined, and approaches that might improve our understanding of the options available for reducing the incidence of this adverse effect of immunosuppression are described. Whether anti-rejection drugs have been successful in diminishing overall immunosuppressive burden, and consequently show any promise for decreasing post-transplant malignancies is also discussed. The topic shifts to one class of conventional anti-rejection drugs, the mammalian target of rapamycin (mTOR) inhibitors, which paradoxically have both immunosuppressive and anti-neoplastic properties. The complex activities of mTOR are reviewed in order to provide context for how these seemingly opposing effects are possible, and the latest clinical data on use of mTOR inhibitors in the clinic are discussed. The current and future perspectives on how best to normalize these unacceptably high rates of post-transplantation malignancies are highlighted.

Cellular and molecular effects of the mTOR inhibitor everolimus

mTOR (mechanistic target of rapamycin) functions as the central regulator for cell proliferation, growth and survival. Up-regulation of proteins regulating mTOR, as well as its downstream targets, has been reported in various cancers. This has promoted the development of anti-cancer therapies targeting mTOR, namely fungal macrolide rapamycin, a naturally occurring mTOR inhibitor, and its analogues (rapalogues). One such rapalogue, everolimus, has been approved in the clinical treatment of renal and breast cancers. Although results have demonstrated that these mTOR inhibitors are effective in attenuating cell growth of cancer cells under in vitro and in vivo conditions, subsequent sporadic response to rapalogues therapy in clinical trials has promoted researchers to look further into the complex understanding of the dynamics of mTOR regulation in the tumour environment. Limitations of these rapalogues include the sensitivity of tumour subsets to mTOR inhibition. Additionally, it is well known that rapamycin and its rapalogues mediate their effects by inhibiting mTORC (mTOR complex) 1, with limited or no effect on mTORC2 activity. The present review summarizes the pre-clinical, clinical and recent discoveries, with emphasis on the cellular and molecular effects of everolimus in cancer therapy.

Impact of Epstein Barr virus-related complications after high-risk allo-SCT in the era of pre-emptive rituximab

We monitored 133 high-risk allo-SCT recipients for 6 months after transplant for EBV reactivation by quantitative real-time PCR. Rituximab was given as pre-emptive therapy for viremia >1000 copies/mL. The 1-year cumulative incidence of EBV reactivation was 29.4% (95% confidence interval (CI): 18-40) in patients monitored due to initial high-risk characteristics (n=93) and 31.8% (95% CI: 19.7-44) in those followed because of the development of refractory GVHD (n=40). Overall response rate to Rituximab was 83%. Nine patients (9.6%) developed post-transplant lymphoproliferative disorder (PTLD) at a median of +62 days after SCT. Eight of them showed a concomitant CMV reactivation. Second SCT was the only risk factor associated with EBV infection and PTLD in multivariate analysis (hazard ratio (HR) 2.6 (95% CI: 1.1-6.4; P=0.04) and HR 6.4 (95%CI: 1.3-32; P=0.02)). The development of EBV reactivation was not associated with non-relapse mortality or OS (P=0.97 and P=0.84, respectively).

Epidemiology of de novo malignancies after solid-organ transplantation: immunosuppression, infection and other risk factors

Organ transplantation is an increasingly used medical procedure for treating otherwise fatal end-stage organ diseases, and a large number of anti-rejection drugs have been developed to prolong long-term survival of both the individual and the transplanted organ. However, the prolonged use of immunosuppressive drugs is well known to increase the risk of opportunistic diseases, particularly infections and virus-related malignancies. Although transplant recipients experience a nearly twofold elevated risk for all types of de novo cancers, persistent infections with oncogenic viruses are associated with up to hundredfold increased risks. Women of the reproductive age are growing in number among the recipients of solid-organ transplants, but specific data on cancer outcomes are lacking. This article updates evidences linking iatrogenic immunosuppression, persistent infections with oncogenic viruses, other risk factors and post-transplant malignancies. Epidemiological aspects, tumourigenesis related to oncogenic viruses, clinical implications, as well as primary and secondary prevention issues are discussed to offer clinicians and researchers alike an update of an increasingly important topic.

CNI withdrawal for post-transplant lymphoproliferative disorders in kidney transplant is an independent risk factor for graft failure and mortality

Post-transplantation lymphoproliferative disorders (PTLD) are associated with poor patient and graft survival. The risk of rejection and subsequent graft loss are increased by the reduction of immunosuppression therapy, the cornerstone of PTLD treatment. This multicentre, retrospective, nonrandomized cohort study includes 104 adults who developed PTLD after renal or simultaneous renal/pancreatic transplantation between 1990 and 2007. It examines the effect of calcineurin inhibitor (CNI) withdrawal on long-term graft and patient survival. At 10 years postonset of PTLD, the Kaplan-Meier graft loss rate was 43.9% and graft loss or death with functioning graft was 64.4%. Cox multivariate analysis determined risk factors of graft loss as PTLD stage greater than I-II and CNI withdrawal, and for graft loss and mortality, these remained risk factors along with age over 60 years. Type and location of PTLD, year of diagnosis, and chemotherapy regime were not independent risk factors. Multivariate analysis determined CNI withdrawal as the most important risk factor for graft loss (HR = 3.07, CI 95%: 1.04-9.09; P = 0.04) and death (HR: 4.00, CI 95%: 1.77-9.04; P < 0.001). While long-term stable renal function after definitive CNI withdrawal for PTLD has been reported, this review determined that withdrawal is associated with reduced graft and patient survival.

Everolimus inhibits anti-HLA I antibody-mediated endothelial cell signaling, migration and proliferation more potently than sirolimus

Antibody (Ab) crosslinking of HLA I molecules on the surface of endothelial cells triggers proliferative and pro-survival intracellular signaling, which is implicated in the process of chronic allograft rejection, also known as transplant vasculopathy (TV). The purpose of this study was to investigate the role of mammalian target of rapamycin (mTOR) in HLA I Ab-induced signaling cascades. Everolimus provides a tool to establish how the mTOR signal network regulates HLA I-mediated migration, proliferation and survival. We found that everolimus inhibits mTOR complex 1 (mTORC1) by disassociating Raptor from mTOR, thereby preventing class I-induced phosphorylation of mTOR, p70S6K, S6RP and 4E-BP1, and resultant class I-stimulated cell migration and proliferation. Furthermore, we found that everolimus inhibits class I-mediated mTORC2 activation (1) by disassociating Rictor and Sin1 from mTOR; (2) by preventing class I-stimulated Akt phosphorylation and (3) by preventing class I-mediated ERK phosphorylation. These results suggest that everolimus is more effective than sirolimus at antagonizing both mTORC1 and mTORC2, the latter of which is critical in endothelial cell functional changes leading to TV in solid organ transplantation after HLA I crosslinking. Our findings point to a potential therapeutic effect of everolimus in prevention of chronic Ab-mediated rejection.

Role of GAS5 noncoding RNA in mediating the effects of rapamycin and its analogues on mantle cell lymphoma cells

BACKGROUND

Inhibition of the mammalian target of rapamycin (mTOR) pathway is a promising strategy for the treatment of mantle cell lymphoma (MCL). ncRNA growth arrest-specific 5 (GAS5), a 5' terminal oligopyrimidine (5'TOP) RNA regulated by the mTOR pathway, is necessary and sufficient for normal growth arrest in leukemic and untransformed human lymphocytes.

METHODS

We downregulated endogenous GAS5 in mantle cell lymphoma cell lines using RNA interference before treatment with several rapalogues. The effect of GAS5 downregulation was monitored by 3 independent analyses of cell viability, DNA synthesis, and colony-forming ability.

RESULTS

Downregulation of GAS5 substantially reduced the effects of each rapalogue on cell viability, DNA synthesis, and colony-forming ability.

CONCLUSION

Stimulation of expression of candidate tumor suppressor GAS5 is responsible for much of the cytotoxic and cytostatic effects of rapalogues in MCL, suggesting that improved targeting of this pathway may allow improvements in the therapy of this intractable lymphoma.

Is murine gammaherpesvirus-68 (MHV-68) a suitable immunotoxicological model for examining immunomodulatory drug-associated viral recrudescence?

Immunosuppressive agents are used for treatment of a variety of autoimmune diseases including rheumatoid arthritis (RA), systemic lupus erythematosis (SLE), and psoriasis, as well as for prevention of tissue rejection after organ transplantation. Recrudescence of herpesvirus infections, and increased risk of carcinogenesis from herpesvirus-associated tumors are related with immunosuppressive therapy in humans. Post-transplant lymphoproliferative disorder (PTLD), a condition characterized by development of Epstein Barr Virus (EBV)-associated B-lymphocyte lymphoma, and Kaposi's Sarcoma (KS), a dermal tumor associated with Kaposi Sarcoma-associated virus (KSHV), may develop in solid organ transplant patients. KS also occurs in immunosuppressed Acquired Immunodeficiency (AIDS) patients. Kaposi Sarcoma-associated virus (KSHV) is a herpes virus genetically related to EBV. Murine gammaherpes-virus-68 (MHV-68) is proposed as a mouse model of gammaherpesvirus infection and recrudescence and may potentially have relevance for herpesvirus-associated neoplasia. The pathogenesis of MHV-68 infection in mice mimics EBV/KSHV infection in humans with acute lytic viral replication followed by dissemination and establishment of persistent latency. MHV-68-infected mice may develop lymphoproliferative disease that is accelerated by disruption of the immune system. This manuscript first presents an overview of gammaherpesvirus pathogenesis and immunology as well as factors involved in viral recrudescence. A description of different types of immunodeficiency then follows, with particular focus on viral association with lymphomagenesis after immunosuppression. Finally, this review discusses different gammaherpesvirus animal models and describes a proposed MHV-68 model to further examine the interplay of immunomodulatory agents and gammaherpesvirus-associated neoplasia.

Novel therapies for patients with chronic myeloid leukemia

The most immediate issues that will have a major impact on the long-term survival of patients with chronic myeloid leukemia is the optimal use of imatinib mesylate (Gleevec, Novartis) and the development of effective therapies for those patients who are intolerant of, or become resistant to, optimal doses of this agent. Of the multiple new agents that are currently being developed for patients with chronic myeloid leukemia, most are being investigated in patients who have developed resistance to imatinib, which is a confounding factor in itself. The mechanisms of action of novel agents are diverse and they may have a variably synergistic therapeutic relationship with imatinib. The complete blockade of the intracellular pathways that are triggered by Bcr-Abl, combined with successful reversal of apoptotic and/or angiogenic abnormalities in chronic myeloid leukemia, may well lead to a cure for the majority of patients.

Management of acute rejection in paediatric liver transplantation

The success of paediatric liver transplantation is attributed to improved surgical techniques and the advent of calcineurin inhibitor-based immunosuppression. Acute rejection (AR) rarely results in graft loss with calcineurin inhibitor immunosuppressive regimens, and the advent of newer agents like interleukin (IL)-2 receptor antibodies. The latter have the benefit of reducing the incidence of AR further and may be of use in patients who are susceptible to recurrent AR, were retransplanted for graft rejection or are in a steroid-sparing regimen. A total of 60 % of all paediatric liver transplants result in AR; however, there is a 75 % response rate to initial steroid therapy. Steroid therapy remains the mainstay of initial AR management, coupled with an increase in baseline immunosuppression. Steroid-resistant rejection (SRR), previously an immediate indication for potent anti-lymphocyte preparations, is now effectively treated with chimeric or humanised IL-2 receptor monoclonal antibodies. Recurrent AR can be treated by adding adjuvant immunosuppressive agents such as mycophenolate mofetil (MMF) or sirolimus. Studies have also demonstrated the efficacy of MMF as rescue therapy for SRR. Anti-lymphocyte preparations such as anti-thymocyte globulin (ATG) and OKT3 are rarely used in SRR but may be of use as rescue therapy for severe SRR. The challenges of the management of AR remain in the management of recurrent AR and SRR. We discuss the pathogenesis, diagnosis and management of AR, including prevention, and specific management of AR and SRR based on current evidence and our own experience at the King's College Paediatric Liver, Gastroenterology and Nutrition Centre in London.

Posttransplant Lymphoproliferative Disorder after Cardiac Transplantation in Children: Life Threatening Complications Associated with Chemotherapy Combined with Rituximab

Despite the excellent long-term survival currently achieved in pediatric heart transplant recipients, posttransplant lymphoproliferative disorders (PTLDs) are one of the most important causes of morbidity and mortality after heart transplantation (HTx), especially in children. Timely and accurate diagnosis based on histological examination of biopsy tissue is essential for early intervention for PTLD. Chemotherapy is indicated for patients with poor response to reduction of immunosuppressive medication and for highly aggressive monomorphic PTLD. The use of rituximab in combination with chemotherapy is effective to suppress B cell type PTLD (B-PTLD). However, PTLD relapses frequently and the outcome is still poor. Although everolimus (EVL) has been reported to inhibit growth of human Epstein-Barr-virus- (EBV-) transformed B lymphocytes in vitro and in vivo, EVL has several side effects, such as delayed wound healing and an increase in bacterial infection. During combined treatment of chemotherapy and rituximab, B-PTLDs are sometimes associated with life-threatening complications, such as intestinal perforation and cardiogenic shock due to cytokine release syndrome. In HTx children especially treated with EVL, stoma should be made to avoid reoperation or sepsis in case of intestinal perforation. In cases with cardiac graft dysfunction possibly due to cytokine release syndrome by chemotherapy with rituximab for PTLD, plasma exchange is effective to restore cardiac function and to rescue the patients.

The future of heart transplantation

The field of heart transplantation has seen significant progress in the past 40 years. However, the breakthroughs in long-term outcome have seen stagnation in the past decade. Through advances in genomics and transcriptomics, there is hope that an era of personalized transplant therapy lies in the future. To see where heart transplantation truly fits into the long term, searching for and understanding the alternative approaches for heart failure therapy is both important and inevitable. The application of mechanical circulatory support has contributed to the largest advancement in treatment of end stage heart failure. It has already been approved for destination therapy of heart failure, and greater portability and ease of use of the device will be the future trend. Although it is still not prime time for stem cell therapy, clinical experiences have already suggested its potential therapeutic effects. And finally, whole organ engineering is on the horizon as new techniques have opened the way for this to proceed. In the end, progress on alternative therapies largely depends on our deeper understanding of the mechanisms of heart failure and how to prevent it.

Targeting the PI3K/AKT/mTOR signaling axis in children with hematologic malignancies

The phosphatidylinositiol 3-kinase (PI3K), AKT, mammalian target of rapamycin (mTOR) signaling pathway (PI3K/AKT/mTOR) is frequently dysregulated in disorders of cell growth and survival, including a number of pediatric hematologic malignancies. The pathway can be abnormally activated in childhood acute lymphoblastic leukemia (ALL), acute myelogenous leukemia (AML), and chronic myelogenous leukemia (CML), as well as in some pediatric lymphomas and lymphoproliferative disorders. Most commonly, this abnormal activation occurs as a consequence of constitutive activation of AKT, providing a compelling rationale to target this pathway in many of these conditions. A variety of agents, beginning with the rapamycin analogue (rapalog) sirolimus, have been used successfully to target this pathway in a number of pediatric hematologic malignancies. Rapalogs demonstrate significant preclinical activity against ALL, which has led to a number of clinical trials. Moreover, rapalogs can synergize with a number of conventional cytotoxic agents and overcome pathways of chemotherapeutic resistance for drugs commonly used in ALL treatment, including methotrexate and corticosteroids. Based on preclinical data, rapalogs are also being studied in AML, CML, and non-Hodgkin's lymphoma. Recently, significant progress has been made using rapalogs to treat pre-malignant lymphoproliferative disorders, including the autoimmune lymphoproliferative syndrome (ALPS); complete remissions in children with otherwise therapy-resistant disease have been seen. Rapalogs only block one component of the pathway (mTORC1), and newer agents are under preclinical and clinical development that can target different and often multiple protein kinases in the PI3K/AKT/mTOR pathway. Most of these agents have been tolerated in early-phase clinical trials. A number of PI3K inhibitors are under investigation. Of note, most of these also target other protein kinases. Newer agents are under development that target both mTORC1 and mTORC2, mTORC1 and PI3K, and the triad of PI3K, mTORC1, and mTORC2. Preclinical data suggest these dual- and multi-kinase inhibitors are more potent than rapalogs against many of the aforementioned hematologic malignancies. Two classes of AKT inhibitors are under development, the alkyl-lysophospholipids (APLs) and small molecule AKT inhibitors. Both classes have agents currently in clinical trials. A number of drugs are in development that target other components of the pathway, including eukaryotic translation initiation factor (eIF) 4E (eIF4E) and phosphoinositide-dependent protein kinase 1 (PDK1). Finally, a number of other key signaling pathways interact with PI3K/AKT/mTOR, including Notch, MNK, Syk, MAPK, and aurora kinase. These alternative pathways are being targeted alone and in combination with PI3K/AKT/mTOR inhibitors with promising preclinical results in pediatric hematologic malignancies. This review provides a comprehensive overview of the abnormalities in the PI3K/AKT/mTOR signaling pathway in pediatric hematologic malignancies, the agents that are used to target this pathway, and the results of preclinical and clinical trials, using those agents in childhood hematologic cancers.

mTOR kinase inhibitors as a treatment strategy in hematological malignancies

The mammalian target of rapamycin (mTOR) kinase is a key element of intracellular signal transduction, responsible for the regulation of cell growth and proliferation. Since abnormal activation of the mTOR pathway was found in several tumors, including human malignancies, it may be an attractive target for antineoplastic treatment. The first identified mTOR inhibitor was rapamycin (sirolimus). Subsequently, the most potent rapamycin analogues (rapalogues), such as everolimus, temsirolimus and deforolimus, have been developed. After encouraging preclinical experiments, several clinical trials testing the rapalogues in monotherapy or in combinations with other cytotoxic agents have been conducted in patients with hematological malignancies. Results of these studies, described in this review, indicate that inhibition of the mTOR pathway may be a very promising strategy of anti-tumor treatment in several types of lymphomas and leukemias. Recently, a second generation of more effective mTOR inhibitors has been developed. These are currently being assessed in preclinical, Phase I or I/II clinical studies.

Inhibition of influenza A virus replication by antagonism of a PI3K-AKT-mTOR pathway member identified by gene-trap insertional mutagenesis

BACKGROUND

Host genes serving potential roles in virus replication may be exploited as novel antiviral targets.

METHODS

Small interfering RNA (siRNA)-mediated knockdown of host gene expression was used to validate candidate genes in screens against six unrelated viruses, most importantly influenza. A mouse model of influenza A virus infection was used to evaluate the efficacy of a candidate FDA-approved drug identified in the screening effort.

RESULTS

Several genes in the PI3K-AKT-mTOR pathway were found to support broad-spectrum viral replication in vitro by RNA interference. This led to the discovery that everolimus, an mTOR inhibitor, showed in vitro antiviral activity against cowpox, dengue type 2, influenza A, rhino- and respiratory syncytial viruses. In a lethal mouse infection model of influenza A (H1N1 and H5N1) virus infection, everolimus treatment (1 mg/kg/day) significantly delayed death but could not prevent mortality. Fourteen days of treatment was more beneficial in delaying the time to death than treatment for seven days. Pathological findings in everolimus-treated mice showed reduced lung haemorrhage and lung weights in response to infection.

CONCLUSIONS

These results provide proof of concept that cellular targets can be identified by gene knockout methods, and highlight the importance of the PI3K-AKT-mTOR pathway in supporting viral infections.

Association of immunosuppressive maintenance regimens with posttransplant lymphoproliferative disorder in kidney transplant recipients

BACKGROUND

The association of immunosuppressive regimens (ISRs) with posttransplant lymphoproliferative disorder (PTLD) may be related with the Epstein-Barr virus (EBV) recipient serostatus.

METHODS

We selected primary kidney transplant recipients from Organ Procurement Transplant Network/United Network for Organ Sharing database (2000-2009) who were discharged with a functioning graft and were receiving an ISR including an antiproliferative drug and a calcineurin inhibitor as follows: mycophenolate mofetil (MMF)/mycophenolate sodium+tacrolimus (TAC), MMF+cyclosporine A (CsA); mammalian target of rapamycin inhibitor (mTORi)+TAC; and mTORi+CsA. Adjusted risks of PTLD, rejection, death, and graft failure were examined in all recipients and compared between EBV+ and EBV- recipients.

RESULTS

Of 114,025 recipients, 754 developed PTLD (5-year incidence of 0.84%). Adjusted hazard ratio for PTLD was 4.39 (95% CI: 3.60-5.37) for EBV- versus EBV+ recipients; and 1.40 (95% CI: 1.03-1.90) for mTORi+TAC, 0.80 (95% CI: 0.65-0.99) for MMF+CsA, and 0.90 (95% CI: 0.57-1.42) for mTORi+CsA, versus MMF+TAC users. In EBV- recipients, hazard ratio for PTLD was 1.98 (95% CI: 1.28-3.07) for mTORi+TAC, 0.45 (95% CI: 0.28-0.72) for MMF+CsA, and 0.84 (95% CI: 0.39-1.80) for mTORi+CsA users versus MMF+TAC. No difference was seen in EBV+ recipient groups. Rejection rates were higher among MMF+CsA recipients in both EBV groups. Death and graft failure risk were increased in all EBV+ISR groups, while in EBV- these risks were only increased in mTORi+TAC group versus MMF+TAC.

CONCLUSIONS

In EBV- recipients, immunosuppression with mTORi+TAC was associated with increased risk of PTLD, death, and graft failure, while MMF+CsA use was associated with a trend to increased risk of rejection, lower PTLD risk, and similar risk for graft failure when compared with MMF+TAC.

New developments in mammalian target of rapamycin inhibitors for the treatment of sarcoma

Although sarcomas account for a small portion of solid malignancies, currently, there are few treatment options for sarcomas, particularly for advanced disease. The mammalian target of rapamycin (mTOR), a serine-threonine protein kinase in the phosphatidylinositol 3-kinase/serine/threonine protein kinase Akt signaling pathway, has an important role in the regulation of protein synthesis, cell proliferation, angiogenesis, and metabolism. Alterations of the mTOR signaling pathway are common in malignancies, including several types of sarcoma. Therefore, mTOR is a potentially important therapeutic target in these diseases. Rapamycin and its analogs (rapalogs) are effective anticancer agents in a broad range of preclinical models. Clinical trials with these agents alone and in combination with other anticancer agents, including chemotherapy and targeted therapies, have demonstrated potential clinical benefit in several types of sarcoma. The evidence from both preclinical and clinical studies supports further study of mTOR-targeting rapalogs in the treatment of various subtypes of sarcoma.

Everolimus in clinical practice in long-term liver transplantation: an observational study

INTRODUCTION

Everolimus, a mammalian target of rapamycin (mTOR) inhibitor, has been used in acute and chronic treatment of kidney and heart transplants. There is scarce information regarding its use in liver transplant recipients, although everolimus may be a useful alternative for selected cases.

OBJECTIVE

The objective of this study was to study the clinical, biochemical, and pathological features of patients to whom everolimus was added based upon defined clinical profiles.

STUDY DESIGN

This study was prospective observational ongoing study to evaluate the effectiveness and safety of everolimus alone or in combination with low doses of a calcineurin inhibitor (CNI). Chronic liver transplant recipients without contraindications to everolimus were defined based upon 7 profiles of complications. The initial everolimus dose (0.25 mg every 12 hours) was overlapped during conversion, measuring blood levels and evaluating clinical tolerance. Routine monitoring was performed to obtain immunosuppressant blood levels near the lower limit of the therapeutic range.

RESULTS

The 35 patients' including 17 men and 18 women, had an overall mean age of 61 ± 10 years with a mean follow-up of 34 months. The everolimus treatment lasted 20 months (range, 6-60). The indication for everolimus conversion were as follows: renal insufficiency (45.7%), no response to hepatitis C virus (HCV) treatment (42.9%), autoimmune hepatitis associated with interferon (8.5%), de novo autoimmune hepatitis (25.5%), de novo tumor (37.1%), neurotoxicity (14.3%), or side effects to rapamycin treatment (5.7%). Patients may have presented more than one indication. Effectiveness was assessed based upon improved liver (48.6%) or renal function (31.25% with renal insufficiency) or withdrawal of prednisone (100% of 10 patients receiving prednisone). CNI was withdrawn from 48.6% of patients due to de novo tumors or neurotoxicity. The side effect were as follows: anemia, leukopenia, or thrombocytopenia (11.4%) or dyslipidemia (27.3%). The survival rate was 94.3%.

CONCLUSIONS

Administration of everolimus to chronic liver transplants enhanced therapeutic options in the long term recipients when applied for predefined clinical indications and administrated with dose adjustments based on serial monitoring of exposure.

Conversion to everolimus in maintenance liver transplant patients: a multicenter, retrospective analysis

Data on the conversion of patients to everolimus after liver transplantation are sparse. A multicenter, retrospective study followed 240 maintenance liver transplant patients to analyze the current indications for everolimus conversion, the employed regimens and exposure levels, and the impact on efficacy and safety. The mean time from transplantation to the introduction of everolimus was 4.9 ± 5.2 years. The mean everolimus trough level was 7.3 ± 4.1 ng/mL at month 1 and 8.1 ± 4.7 ng/mL at month 12. At 12 months, 61.6% of the patients were no longer receiving calcineurin inhibitor (CNI) therapy. The mean estimated glomerular filtration rate (eGFR) according to the Cockcroft-Gault formula was 64.2 ± 30.0 mL/minute on day 0 and 68.4 ± 32.5 mL/minute at month 12 (P = 0.007). Among patients with baseline serum creatinine levels ≥ 130 μmol/L, the eGFR values were 44.3 ± 15.7 mL/minute on day 0 and 53.7 ± 26.0 mL/minute at month 12 (P = 0.003). Four patients (1.6%) developed mild or moderate biopsy-proven acute rejection. Adverse events led to everolimus discontinuation in 12.9% of the patients. After the initiation of everolimus, the mean white blood cell count decreased significantly, and the total cholesterol and triglyceride levels increased significantly. In this retrospective analysis of the largest cohort of maintenance liver transplant patients analyzed after their conversion to everolimus, more than 60% of the patients were kept free of CNIs with a very low risk of acute rejection and with an acceptable safety profile. Randomized trials in which maintenance liver transplant patients are switched to everolimus in response to clinical indications or preemptively are warranted.

The use of everolimus in pediatric liver transplant recipients: first experience in a single center

The role of mTOR inhibitors, such as EVL, has not been established for pediatric liver transplant recipients up to now, although data from adult solid organ graft transplantation are very promising. Major complications following pediatric liver transplantation in the long-term course include chronic graft rejection and CNI-derived nephrotoxicity. The purpose of our study was to report first results using EVL as a rescue therapy in pediatric liver transplant recipients for the following indications: chronic graft dysfunction n=12, suspected CNI toxicity n=3, hepatoblastoma n=2, and recurrence of primary sclerosing cholangitis post-Ltx n=1. Four patients with chronic graft dysfunction developed completely normal liver function tests using EVL, six patients showed partial improvement, and two patients did not respond at all. One patient with CNI-induced nephropathy showed a slightly improved GFR. Both patients with hepatoblastoma did not develop any metastasis post-Ltx. First experience with EVL in pediatric liver transplant recipients shows promising results in patients with chronic graft failure when standard immunosuppression has failed. The future role of EVL in immunosuppressive protocols for children post-Ltx has to be proven by controlled clinical trials.

Posttransplant lymphoproliferative disease in liver transplant patients

Posttransplant lymphoproliferative disorders (PTLD) are a life-threatening complication following solid organ transplantation. Many posttransplant lymphomas develop from the uncontrolled proliferation of Epstein-Barr virus (EBV)-infected B-cells, whereas EBV-negative PTLDs were increasingly recognized within the past decade. Major risk factors for the development of PTLDs after liver transplantation are immunosuppressive therapy and the type of underlying disease: viral hepatitis, autoimmune liver disease, or alcoholic liver cirrhosis contribute to an increased risk for PTLD. Therapeutic regimens include reduction of immunosuppression, the anti-CD20 antibody rituximab, and chemotherapy, as well as new approaches using interferon-α and anti-interleukin-6 antibodies. Despite the different therapeutic regimens, mortality from PTLD remains high. Therefore, it is of major importance to identify patients at risk at an early stage of the disease. In this review, risk factors for PTLD development after liver transplantation, clinical presentation, diagnosis, and therapy are discussed.

mTOR as a multifunctional therapeutic target in HIV infection

Patients undergoing long-term highly active antiretroviral therapy treatment are probably at a higher risk of various HIV-related complications. Hyperactivation of The mammalian target of rapamycin (mTOR) has been found to contribute to dysregulated apoptosis and autophagy which determine CD4(+)-T-cell loss, impaired function of innate immunity and development of neurocognitive disorders. Dysregulated mTOR activation has also been shown to play a key part in the development of nephropathy and in the pathogenesis of HIV-associated malignancies. These studies strongly support a multifunctional key role for mTOR in the pathogenesis of HIV-related disorders and suggest that specific mTOR inhibitors could represent a novel approach for the prevention and treatment of these pathologies.

Proliferation signal inhibitors and post-transplant malignancies in heart transplantation: practical clinical management questions

Although malignancy is a major threat to long-term survival of heart transplant (HT) recipients, clear strategies to manage immunosuppression in these patients are lacking. Several lines of evidences support the hypothesis of an anticancer effect of proliferation signal inhibitors (PSIs: mammalian target of rapamycin [mTOR] inhibitors) in HT recipients. This property may arise from PSI's ability to replace immunosuppressive therapies that promote cancer progression, such as calcineurin inhibitors or azathioprine, and/or through their direct biological actions in preventing tumor development and progression. Given the lack of randomized studies specifically exploring these issues in the transplant setting, a collaborative group reviewed current literature and personal clinical experience to reach a consensus aimed to provide practical guidance for the clinical conduct in HT recipients with malignancy, or at high risk of malignancy, with a special focus on advice relevant to potential role of PSIs.

Malignancy after renal transplantation: the role of immunosuppression

Outcomes of kidney transplantation, in terms of graft and patient survival, have improved over the past few decades, partly as a result of the introduction of new immunosuppressive drugs. Many immunosuppressive agents are associated with an increased risk of cardiovascular events and an increased risk of cancer, however, which can compromise patient survival. Cancer is more common among solid-organ transplant recipients than it is in the general population or in patients on dialysis. In fact, malignancy is the third most common cause of death in renal transplant recipients. Immunosuppressive treatments used in renal transplant recipients can cause malignancy by supporting oncogenesis caused by certain viruses or by impairing immune surveillance thereby enabling faster tumor growth. In this Review, we describe the epidemiological and clinical characteristics of common tumor types occurring after kidney transplantation, and the etiopathogenetic factors that lead to their appearance, with a particular focus on the relationship between immunosuppressive treatment and malignancy. Immunosuppressive drugs associated with an increased risk of malignancy after transplantation are also discussed, as are immunosuppressive drugs that seem to have antioncogenic properties.

Critical Review of Preclinical Approaches to Evaluate the Potential of Immunosuppressive Drugs to Influence Human Neoplasia

Many immunosuppressive drugs are associated with an increased risk of B-cell lymphoma, squamous cell carcinoma, and Kaposi sarcoma. Thirteen immunosuppressive drugs have been tested in 2-year carcinogenicity studies (abatacept; azathioprine; busulfan; cyclophosphamide; cyclosporine; dexamethasone; everolimus; leflunomide; methotrexate; mycophenolate mofetil; prednisone; sirolimus; and tacrolimus) and in additional models including neonatal and genetically modified mice; chemical, viral, ultraviolet, and ionizing radiation co-carcinogenesis, and in models with transplanted tumor cells. The purpose of this review is to outline the mechanisms by which immunosuppressive drugs can influence neoplasia, to summarize the available preclinical data on the 13 drugs, and to critically review the performance of the models. A combination of primary tumor and metastasis assays conducted with transplanted cells may provide the highest value for hazard identification and can be applied on a case-by-case basis. However, for both small molecules and therapeutic proteins, determining the relative risk to patients from preclinical data remains problematic. Classifying immunosuppressive drugs based on their mechanism of action and hazard identification from preclinical studies and a prospective pharmacovigilance program to monitor carcinogenic risk may be a feasible way to manage patient safety during the clinical development program and postmarketing.