The immunosuppressive drug mycophenolate mofetil impairs the adhesion capacity of gastrointestinal tumour cells

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.

Host and immunosuppression-related factors influencing fibrosis occurrence post liver transplantation

Post liver transplantation (LT) fibrosis has a negative impact on graft function. Cytokine production in the host immune response after LT may contribute to the variable CYP3A-dependent immunosuppressive drug disposition, with subsequent impact on liver fibrogenesis, together with host-related factors. We aimed to investigate whether the cytochrome P4503A5*3 (CYP3A5*3) or TBX21 genotypes impact post-LT liver fibrogenesis. Furthermore, the impact of immunosuppressants on cellular apoptosis has been evaluated using human hepatocytes harvested from cirrhotic explanted livers. We have enrolled 98 LT recipients that were followed for occurrence of liver fibrosis for at least 12 months. There was a statistically significant higher trough level of TAC in patients with homozygous CC-TBX21 genotype (7.83 ± 2.84 ng/ml) vs. 5.66 ± 2.16 ng/ml in patients without this genotype (p = 0.009). The following variables were identified as risk factors for fibrosis ≥2: donor age (p = 0.02), neutrophil to lymphocyte ratio (p = 0.04) and TBX21 genotype CC (p = 0.009). In the cell culture model cytometry analysis has indicated the lowest apoptotic cells percentage in human cirrhotic hepatocytes cultures treated with mycophenolate mofetil (MMF) (5%) and TAC + MMF (2%) whereas the highest apoptosis percentage was registered for the TAC alone (11%). The gene expression results are concordant to cytometry study results, indicating the lowest apoptotic effect for MMF and MMF + TAC immunosuppressive regimens. The allele 1993C of the SNP rs4794067 may predispose to the development of late significant fibrosis of the liver graft. MMF-based regimens have a favourable anti-apoptotic profile in vitro, supporting its use in case of LT recipients at high risk for liver graft fibrosis.

Current Status of Malignant Tumors after Organ Transplantation

Objective

To analyze the diagnosis and treatment of patients with concomitant malignant tumors after organ transplantation by compiling data from organ transplantation patients.

Methods

By searching CNKI and PubMed databases, we made a systematic analysis of the studies of postorgan transplantation complicating malignant tumors in the last decade.

Results

There were 10 articles on malignant tumors after renal transplantation, 8 articles on liver transplantation, 2 articles on heart transplantation, and 1 article on lung transplantation. The incidence of malignant tumors complicating renal transplantation is 10.4% in Europe, with skin cancer and Kaposi's sarcoma being common; the incidence in the United States is 3.4%, with PTLD having the highest incidence; the incidence of malignant tumors is relatively lowest in Asia, with gastrointestinal malignancies being the main ones. The mean time to complication of malignancy after renal transplantation is 3.83 years. The incidence of concurrent malignancies after liver transplantation is 8.8% in Europe, where skin cancer and Kaposi's sarcoma are common; 5.6% in Asia, where gastrointestinal tract tumors are prevalent; and 4.5% in the United States, where gastrointestinal tract tumors, PTLD, and hematologic diseases are predominant. The mean time to complication of malignancy after liver transplantation is 4.79 years. The incidence of malignancy after heart transplantation is 6.8-10.7%. The incidence of malignancy after lung transplantation is about 10.1%. Minimization of immunosuppression or modification of immunosuppression regimens may be a key component of cancer prevention. mTOR inhibitors and phenolate (MMF) reduce the incidence of de novo malignancies in patients after solid organ transplantation. Surgical treatment improves survival in patients with early malignancies. The use of external beam radiation therapy in the treatment of hepatocellular carcinoma is limited due to the risk of radiation liver disease.

Conclusions

The risk of concomitant malignancy needs to be guarded for 5 years of immunosuppressive therapy after organ transplantation surgery. Adjusting the immunosuppressive treatment regimen is an effective way to reduce concurrent malignancies. Systemic chemotherapy or radiotherapy requires vigilance against the toxic effects of drug metabolism kinetics on the transplanted organ.

Therapeutic potential and molecular mechanisms of mycophenolic acid as an anticancer agent

Mycophenolic acid (MPA) is the active metabolite of mycophenolate mofetil (MMF), an immunosuppressive drug approved for the prophylaxis of allograft rejection in transplant recipients. Recent advances in the role of the type II isoform of inosine-5'-monophosphate dehydrogenase (IMPDH2) in the tumorigenesis of various types of cancer have called for a second look of MPA, the first IMPDH2 inhibitor discovered a hundred years ago, to be repurposed as an anticancer agent. Over a half century, a number of in vitro and in vivo experiments have consistently shown anticancer activity of MPA against several cell lines obtained from different malignancies and murine models. However, a few clinical trials have been conducted to investigate its anticancer activity in humans, and most of which have shown unsatisfactory results. Understanding of available evidence and underlying mechanism of action is a key step to be done so as to facilitate further investigations of MPA to reach its full therapeutic potential as an anticancer agent. This article provides a comprehensive review of non-clinical and clinical evidence available to date, with the emphasis on the molecular mechanism of action in which MPA exerts its anticancer activities: induction of apoptosis, induction of cell cycle arrest, and alteration of tumor microenvironment. Future perspective for further development of MPA to be an anticancer agent is extensively discussed, with the aim of translating the anticancer property of MPA from bench to bedside.

Risk factors associated with post-kidney transplant malignancies: an article from the Cancer-Kidney International Network

In kidney transplant recipients, cancer is one of the leading causes of death with a functioning graft beyond the first year of kidney transplantation, and malignancies account for 8-10% of all deaths in the USA (2.6 deaths/1000 patient-years) and exceed 30% of deaths in Australia (5/1000 patient-years) in kidney transplant recipients. Patient-, transplant- and medication-related factors contribute to the increased cancer risk following kidney transplantation. While it is well established that the overall immunosuppressive dose is associated with an increased risk for cancer following transplantation, the contributive effect of different immunosuppressive agents is not well established. In this review we will discuss the different risk factors for malignancies after kidney transplantation.

Mycophenolate Mofetil induces c-Jun-N-terminal kinase expression in 22Rv1 cells: an impact on androgen receptor signaling

Mycophenolate Mofetil (MYC) is a transplant drug used to prevent rejection in heart and kidneys transplant patients. Inosine monophosphate dehydrogenase (IMPDH), an enzyme involved in de novo synthesis of guanosine nucleotides, was considered as a primary target for MYC. Recently, we described that MYC was activates aryl hydrocarbon receptor and it antagonizes glucocorticoid receptor. Here we describe an androgen receptor (AR) as another off-target for MYC.

We found that MYC increased basal and dihydrotestosterone (DHT)-inducible AR-dependent luciferase activity in AIZ-AR cells. In the same manner it induced or augmented mRNA level of KLK3 (prostate specific antigen; PSA) in 22Rv1 cells. Herein it displayed a hormetic effect on proliferation activity, since it significantly stimulated proliferation in lower concentrations but inhibited in higher (>1 µg/ml) concentrations in the presence of DHT. In contrast, MYC suppressed DHT-inducible KLK3 mRNA expression and cell proliferation in androgen-dependent LNCaP cells. MYC augmented DHT-inducible nuclear translocation of AR and increased the expression of MAPK8/9 (JNK46/54) resulting in the drop of their phosphorylation status. Moreover, MYC sensitized DHT-treated 22Rv1 cells to JNK-IN-8 mediated growth inhibition with the drop of IC₅₀ from 1425 nM to 84 nM within 24 hrs. In conclusion, we suggest that, castrate-resistant prostate cancers progression might be retarded with the combination of MYC and chemical JNK inhibitors, involving AR-dependent mechanism.

Comprehensive Review on Colorectal Cancer and Transplant

Colorectal cancer (CRC) is a common malignancy worldwide. Some studies suggest that organ recipients are at a higher risk for CRC than the general population. The underlying transplant indications and their inherent risk factors for CRC may drive the variation in incidence rates that are seen in patients receiving different allografts. Recipients with cystic fibrosis are now recognized as a population at high risk for CRC at a young age. Transplant recipients have high mortality following a CRC diagnosis, even if it is detected at an early stage. Certain types of immunosuppression have been shown to accelerate cancer transformation and may contribute to the more aggressive phenotype seen in organ recipients. Given the high incidence and progressive nature of posttransplant CRC, shorter screening intervals with a modality that can detect early-stage polyps may be essential to prevent mortality. Future research is needed to better elucidate the role of immunosuppression in carcinogenesis. This comprehensive review examines CRC risk, screening, and management specific to organ transplant candidates and recipients.

Downregulation of telomerase maintenance-related ACD expression in patients undergoing immunosuppresive therapy following kidney transplantation

Chronic administration of immunosuppressants has been associated with long-term consequences, including a higher risk of neoplasm development. The processes regulating telomere function exert a major influence on human cancer biology. The present study aimed to assess the effect of immunosuppressive therapy on the expression of genes associated with telomere maintenance and protection in patients following renal transplantation. A total of 51 patients that had undergone kidney transplantation and 54 healthy controls were enrolled in the study. The 51 transplant patients received a three-drug immunosuppressive regimen consisting of cyclosporine A, prednisone and mycophenolate mofetil. In stage 1 of the study, the expression profiles of 123 transcripts, which represented 70 genes, were assessed in peripheral mononuclear blood cells using an oligonucleotide microarray technique in 8 transplant recipients and 4 healthy control subjects. Among the analyzed transcripts, the expression levels of 4 differed significantly between the studied groups; however, only the ACD (adrenocortical dysplasia homolog) gene, encoding the telomere-binding protein POT1-interacting protein 1 (TPP1), was sufficiently specific for telomere homeostasis. The expression of ACD was downregulated in transplant recipients (fold change, 2.11; P=0.006). In stage 2 of the study, reverse transcription-quantitative polymerase chain reaction analysis of ACD, DKC1 and hTERT mRNA was conducted for all transplant patients and control subjects. The results confirmed the downregulation of the ACD gene in patients that had received immunosuppressive therapy (P=0.002). The results of the present study indicate that the downregulation of ACD gene transcription, and thus TPP1 protein expression, may enhance the capacity for cell immortalization, despite normal levels of other key telomere maintenance factors, in patients undergoing immunosuppressive therapy. Furthermore, the results indicate that TPP1 has potential for use as an early clinical marker and/or therapeutic target for cancer in patients following organ transplantation.

Management and prevention of post-transplant malignancies in kidney transplant recipients

The central issue in organ transplantation remains suppression of allograft rejection. Thus, the development of immunosuppressive drugs has been the key to successful allograft function. The increased immunosuppressive efficiency obtained in the last two decades in kidney transplantation dramatically reduced the incidence of acute rejection. However, the inevitable trade-off was an increased rate of post-transplant infections and malignancies. Since the incidence of cancer in immunosuppressed transplant recipients becomes greater over time, and the introduction of new immunosuppressive strategies are expected to extend significantly allograft survival, the problem might grow exponentially in the near future. Thus, cancer is becoming a major cause of morbidity and mortality in patients otherwise successfully treated by organ transplantation. There are at least four distinct areas requiring consideration, which have a potentially serious impact on recipient outcome after transplantation: (i) the risk of transmitting a malignancy to the recipient within the donor organ; (ii) the problems of previously diagnosed and treated malignancy in the recipient; (iii) the prevention of de novo post-transplant malignant diseases and (iv) the management of these complex and often life-threatening clinical problems. In this scenario, the direct and indirect oncogenic potential of immunosuppressive therapy should be always carefully considered.

A Review of the Potential Utility of Mycophenolate Mofetil as a Cancer Therapeutic

Tumor cells adapt to their high metabolic state by increasing energy production. To this end, current efforts in molecular cancer therapeutics have been focused on signaling pathways that modulate cellular metabolism. However, targeting such signaling pathways is challenging due to heterogeneity of tumors and recurrent oncogenic mutations. A critical need remains to develop antitumor drugs that target tumor specific pathways. Here, we discuss an energy metabolic pathway that is preferentially activated in several cancers as a potential target for molecular cancer therapy. In vitro studies have revealed that many cancer cells synthesize guanosine triphosphate (GTP), via the de novo purine nucleotide synthesis pathway by upregulating the rate limiting enzyme of this pathway, inosine monophosphate dehydrogenase (IMPDH). Non-proliferating cells use an alternative purine nucleotide synthesis pathway, the salvage pathway, to synthesize GTP. These observations pose IMPDH as a potential target to suppress tumor cell growth. The IMPDH inhibitor, mycophenolate mofetil (MMF), is an FDA-approved immunosuppressive drug. Accumulating evidence shows that, in addition to its immunosuppressive effects, MMF also has antitumor effects via IMPDH inhibition in vitro and in vivo. Here, we review the literature on IMPDH as related to tumorigenesis and the use of MMF as a potential antitumor drug.

In vitro effects of mycophenolic acid on survival, function, and gene expression of pancreatic beta-cells

Post-transplant diabetes mellitus represents an important complication of prolonged immunosuppressive treatment after solid organ transplantation. The immunosuppressive toxicity, responsible for a persistent impairment of glucose metabolism in pancreatic islet-transplanted patients, is mainly attributed to calcineurin inhibitors and steroids, while other immunosuppressive molecules (azathioprine and mycophenolic acid, MPA) are considered not to have a toxic effect. In the present study, in vitro effects of MPA have been investigated in mouse beta-cell lines (βTC-1 and βTC-6) and in purified human pancreatic islets. βTC-1, βTC-6, and human pancreatic islets were exposed to various concentrations of MPA for different times. Consequently, we evaluated the viability, the induction of apoptosis, the glucose-stimulated insulin secretion, and the expression of β-cell function genes (Isl1, Pax6, Glut-2, glucokinase) and apoptosis-related genes (Bax and Bcl2). βTC-1, βTC-6, and human islets treated, respectively, for 48 and 72 h with 15-30 nM MPA showed altered islet architecture, as compared with control cells. We observed for βTC-1 and βTC-6 almost 70% reduction in cell viability; three to sixfold induction of TUNEL/apoptotic-positive cells quantified by FACS analysis. A twofold increase in apoptotic cells was observed in human islets after MPA exposure associated with strong inhibition of glucose-stimulated insulin secretion. Furthermore, we showed significant down-regulation of gene expression of molecules involved in β-cell function and increase rate between Bax/Bcl2. Our data demonstrate that MPA has an in vitro diabetogenic effect interfering at multiple levels with survival and function of murine and human pancreatic β-cells.

Progression to adenocarcinoma in Barrett's esophagus after liver transplantation

BACKGROUND

The risk for development of certain malignancies after transplantation is well known. Especially in premalignant lesions of the skin and colon, rapid progression is described. The aim of this study is to evaluate the progress of Barrett's mucosa to adenocarcinoma of the esophagus after liver transplantation.

METHODS

Between 2000 and 2009, 895 patients underwent a liver transplantation in our department. All patients had an upper endoscopy as part of the evaluation before transplantation. Patients who had Barrett's mucosa described in their endoscopy report were identified. The records of these patients were retrospectively reviewed.

RESULTS

There were seven patients who had Barrett's mucosa in the preoperative endoscopy. Five of these patients (71%) developed an esophageal adenocarcinoma in a median time of 66 months after liver transplantation. One had stage II disease and four had stage III disease. Three of them underwent neoadjuvant therapy. All patients underwent an en bloc esophagectomy. One patient developed recurrent disease after 12 months and died 37 months after esophagectomy. The other four patients are still alive without recurrence and have a median survival of 16 months.

CONCLUSION

Esophageal cancer after liver transplantation is rare, whereas the risk for progression of Barrett's esophagus to adenocarcinoma is extremely high. Surveillance endoscopy with aggressive endoscopic treatment of the Barrett's is essential for these patients to prevent them from cancer death. Furthermore, immunosuppression therapy based on immunosuppressants with antitumoral effects should be preferred. The esophagectomy with neoadjuvant therapy is also in immunosuppressant patients feasible without increased risk for complications.

Risk of colorectal neoplasia in patients with solid organ transplantation

The incidence of colorectal adenomas and advanced neoplasia in the transplant population has not been well characterized. The aim of this study was to determine whether or not there was an increased incidence of colorectal adenomas and advanced neoplasia in solid organ transplantation (SOT) recipients compared with an average-risk population. We reviewed 360 patients with solid organ transplants who underwent colonoscopy between February 1995 and July 2008, and 360 age- and gender-matched patients in an average-risk population. The mean duration from transplantation to colonoscopy in the SOT group was 40.4 ± 34.0 months. Ninety-three (25.8%) adenomas were detected in the SOT group, while 98 (27.2%) adenomas were detected in the control group (p = 0.763). There was a statistically significant difference (p < 0.0001) in the number of patients with advanced neoplasia in the SOT group (24 patients [6.7%]) compared with the control group (3 patients [0.8%]). The independent risk factors of advanced neoplasia were old age (odds ratio [OR], 1.067; 95% CI, 1.019-1.118) and transplantation (OR, 6.069; 95% CI, 1.455-25.314). In summary, there was a significant increase in the incidence of advanced colorectal neoplasia in SOT recipients. The reason for this finding is unclear, and studies with a larger number of patients are needed to further evaluate this group.

[Bronchogenic carcinoma after lung transplantation: a case report and literature review]

背景与目的

肺移植是治疗终末期肺部疾病的有效手段，然而对肺移植术后肺癌却缺乏了解。我们通过对1例肺移植术后肺癌患者临床资料的报道，并结合相关文献复习，以提高对肺移植术后肺癌的认识、诊断及治疗水平。

方法

2007年5月我院为一例65岁、术前诊断为两肺特发性肺间质纤维化（idiopathic pulmonary fibrosis, IPF）的男性患者在体外膜肺氧合（extracorporeal membrane oxygenation, ECMO）辅助下成功进行了右侧单肺移植，患者术后46 d恢复良好出院。术后免疫抑制方案为他克莫司（Tac）+吗替麦考酚酯（骁悉）+类固醇激素。出院后患者定期随访。

结果

在移植术后13个月随访确诊为非移植侧左肺小细胞肺癌伴多发骨转移。患者给予依托泊苷联合顺铂（EP方案）化疗4次症状有所缓解，患者在诊断肺癌后11个月死亡。

结论

肺移植术后肺癌严重影响移植患者远期存活，慢性阻塞性肺病（chronic obstructive pulmonary disease, COPD）、IPF、吸烟史及免疫抑制剂等为其危险因素，为改善预后，需要早期诊断及早期治疗。

Brain dead donor kidneys are immunologically active: is intervention justified?

The improvement in the field of kidney transplantation, during the last decades, has brought kindey transplantation to the top of patient preference as the best kidney replacement therapy. The use of marginal kidney grafts, which are highly immunogenic has become common practice because of lack of kidney donors. Inflammatory activity in the kidneys after brain death is an ongoing phenomenon. The inappropriate treatment of brain dead donor may result to primary non function (PNF) of the graft, delayed graft function (DGF) or to long term graft dysfunction and shortened graft survival. Therefore correct handling of the brain dead donor is of paramount importance. The impact of various pharmacologic agents (catecholamines, glucocorticoids, carbamylated recombinant human erythropoietin, recombinant soluble P-selectin glycoprotein ligant, heme oxygenase-1, carbon monoxide, and mycophenolate mofetil) on the immunogenicity of brain dead donor kidneys is discussed.

Long-term risk of malignancy among patients treated with immunosuppressive agents for ocular inflammation: a critical assessment of the evidence

PURPOSE

To critically assess potentially carcinogenic effects of immunosuppressive therapy in the ocular inflammation setting.

DESIGN

Focused evidence assessment.

METHODS

Relevant publications were identified by MEDLINE and EMBASE queries and reference list searches.

RESULTS

Extrapolation from transplant, rheumatology, skin disease, and inflammatory bowel disease cohorts to the ocular inflammation setting suggest that: 1) alkylating agents increase hematologic malignancy risk and cyclophosphamide increases bladder cancer risk, but less so with < or =18 months' duration of therapy and hydration, respectively; 2) calcineurin inhibitors and azathioprine probably do not increase total cancer risk to a detectable degree, except perhaps some other risk factors (uncommon in ocular inflammation patients) might interact with the former to raise risk; 3) tumor necrosis factor (TNF) inhibitors may accelerate diagnosis of cancer in the first six to 12 months, but probably do not increase long-term cancer risk; and 4) changes in risk with methotrexate, mycophenolate mofetil, and daclizumab appear negligible, although nontransplant data are limited for the latter agents. Immunosuppression in general may increase skin cancer risk in a sun exposure-dependent manner.

CONCLUSION

Use of alkylating agents for a limited duration seems justifiable for severe, vision-threatening disease, but otherwise cancer risk may be a relevant constraint on use of this approach. Antimetabolites, daclizumab, TNF inhibitors, and calcineurin inhibitors probably do not increase cancer risk to a degree that outweighs the expected benefits of therapy. Monitoring for skin cancer may be useful for highly sun-exposed patients. Data from ocular inflammation patients are needed to confirm the conclusions made in this analysis by extrapolation.

Immunosuppressive therapy and malignancy in organ transplant recipients: a systematic review

Post-transplant malignancy is recognised as being a major limitation to the success of solid organ transplantation and it is currently considered one of the unavoidable costs of long-term immunosuppressive therapy. However, the continual introduction of new immunosuppressive drugs and the growing knowledge about their different oncogenic profiles, requires a continuous evaluation of the available evidence on this topic. The incidence and risk of malignancy is elevated in solid organ transplant recipients compared with the general population. As proof of the relationship between immunosuppressive therapy and post-transplant malignancy, epidemiological data reveal that the length of exposure to immunosuppressive therapy and the intensity of therapy are clearly related to the post-transplant risk of malignancy, and that once cancer has developed, more intense immunosuppression can translate into more aggressive tumour progression in terms of accelerated growth and metastasis and lower patient survival. The association between malignancy and immunosuppressive therapy is mediated through several pathogenic factors. Indirectly, immunosuppressive drugs greatly increase the post-transplant risk of malignancy by impairing cancer surveillance and facilitating the action of oncogenic viruses. However, the direct pro- and anti-oncogenic actions of immunosuppressants also play an important role. The cancer-promoting effect of calcineurin inhibitors, independently of depressed immunosurveillance, has been demonstrated in recent years, and currently only mammalian target of rapamycin (mTOR) inhibitors have shown simultaneous immunosuppressive and antitumour properties. Reports of the initial results of the reduced incidence of cancer in organ transplant recipients receiving mTOR inhibitor therapy strongly indicate separate pathways for pharmacological immunosuppression and oncogenesis. The role of mTOR inhibitors has been firmly established for the treatment of post-transplant Kaposi's sarcoma and its role in the management of patients with other post-transplant malignancies should be clarified as soon as possible. Prevention of morbidity and mortality resulting from post-transplant malignancy should become a main endpoint in solid organ transplant programmes, and the choice and management of immunosuppressive therapy in each phase of transplantation plays a central role in this objective. Although comprehensive and rigorous information about the management of immunosuppressive therapy in transplant recipients at risk of or affected by cancer is still lacking, new experimental and clinical data about mTOR inhibitors offers novel approaches to this problem.

Antiproliferative and Overadditive Effects of Everolimus and Mycophenolate Mofetil in Pancreas and Lung Cancer Cells In Vitro

BACKGROUND

Everolimus inhibits the growth of several tumor cell lines in vitro as well as tumor growth in a rat model. Mycophenolate mofetil (MMF) inhibits growth of a Walker sarcoma in a rat model in vivo. Herein we tested the in vitro antiproliferative capacity of everolimus and MMF on a pancreatic tumor cell line Panc-1 and on a small cell lung cancer cell line ScLc.

MATERIALS AND METHODS

Cells were cultured under standardized conditions. Everolimus was added in increasing doses from 0.005 to 500 microg/mL; MMF was used from 0.05 to 5000 microg/mL. For co-incubation experiments, we combined everolimus (0.005 microg/mL and 0.05 microg/mL) with five concentrations of MMF; and MMF (0.5 microg/mL and 5 microg/mL) with five concentrations of everolimus. The antiproliferative capacity was assessed by a BrdU incorporation assay.

RESULTS

Everolimus and MMF inhibited BrdU incorporation into Panc-1 and ScLc in a dose-dependent fashion. A 50% inhibition was seen in Panc-1 only at 50 microg/mL everolimus, but in ScLc at 5 microg/mL everolimus. MMF was clearly more potent in Panc-1: 50% inhibition was observed at 5 microg/L. In ScLc, 40% inhibition of BrdU incorporation was seen only at 50 microg/L MMF. In co-incubation, an effective combination for both Panc-1 and ScLc was 5 microg/mL MMF with 0.005 microg/mL everolimus resulting in 50% inhibition of BrdU incorporation (P < .001).

CONCLUSIONS

Everolimus and MMF showed dose-dependent antiproliferative effects in tumor cell lines in vitro both alone and in combination. The combined use of everolimus and MMF showed supra-additive effects at concentrations used for therapeutic immunosuppression in patients.

Revisiting the immunomodulators tacrolimus, methotrexate, and mycophenolate mofetil: their mechanisms of action and role in the treatment of IBD

Inflammatory bowel diseases (IBDs) are thought to result from unopposed immune responses to normal gut flora in a genetically susceptible host. A variety of immunomodulating therapies are applied for the treatment of patients with IBDs. The first-line treatment for IBDs consists of 5-aminosalicylate and/or budesonide. However, these first-line therapies are often not suitable for continuous treatment or do not suffice for the treatment of severe IBD. Recently, efforts have been made to generate novel selective drugs that are more effective and have fewer side effects. Despite promising results, most of these novel drugs are still in a developmental stage and unavailable for clinical application. Yet, another class of established immunomodulators exists that is successful in the treatment of inflammatory bowel diseases. While waiting for emerging novel therapies, the use of these more established drugs should be considered. Furthermore, one of the advantages of using established immunomodulators is the well-documented knowledge on the long-term side effects and on the mechanisms of action. In this review, the authors discuss 3 well-known immunomodulators that are being applied with increased frequency for the treatment of IBD: tacrolimus, methotrexate, and mycophenolate mofetil. These agents have been used for many years as treatment modalities for immunosuppression after organ transplantation, for the treatment of cancer, and for immunomodulation in several other immune-mediated diseases. First, this review discusses the potential targets for immunomodulating therapies in IBDs. Second, the immunomodulating mechanisms and effects of the 3 immunomodulators are discussed in relationship to these treatment targets.

Malignancy after transplantation

As newer immunosuppressive regimens have steadily reduced the incidence of acute rejection and have extended the life expectancy of allograft recipients, posttransplant malignancy has become an important cause of mortality. In fact, it is expected that cancer will surpass cardiovascular complications as the leading cause of death in transplant patients within the next 2 decades. An understanding of the underlying pathobiology and how to minimize cancer risks in transplant recipients are essential. The etiology of posttransplant malignancy is believed to be multifactorial and likely involves impaired immunosurveillance of neoplastic cells as well as depressed antiviral immune activity with a number of common posttransplant malignancies being viral-related. Although calcineurin inhibitors and azathioprine have been linked with posttransplant malignancies, newer agents such as mycophenolate mofetil and sirolimus have not and indeed may have antitumor properties. Long-term data are needed to determine if the use of these agents will ultimately lower the mortality due to malignancy for transplant recipients.

Incidence of cancer after immunosuppressive treatment for heart transplantation

Prolonged or intensive immunosuppressive therapy used after organ transplantation is complicated by an increased incidence of cancer. Striking differences in incidence are observed in heart and heart-lung transplant recipients when compared with renal transplant patients. The most significant increase was in the incidence of lymphomas in cardiac versus renal patients. Moreover, a two-fold greater increase of all neoplasms was found in cardiac recipients, with nearly a six-fold increase in visceral tumors. Several factors may account for these differences. In cardiac allograft recipients, intensive immunosuppression is frequently used to reverse acute rejection and the highest number of cardiac transplants was performed in the era of polypharmacy, usually consisting of triple therapy.

Mycophenolate mofetil modulates adhesion receptors of the beta1 integrin family on tumor cells: impact on tumor recurrence and malignancy

Background

Tumor development remains one of the major obstacles following organ transplantation. Immunosuppressive drugs such as cyclosporine and tacrolimus directly contribute to enhanced malignancy, whereas the influence of the novel compound mycophenolate mofetil (MMF) on tumor cell dissemination has not been explored. We therefore investigated the adhesion capacity of colon, pancreas, prostate and kidney carcinoma cell lines to endothelium, as well as their beta1 integrin expression profile before and after MMF treatment.

Methods

Tumor cell adhesion to endothelial cell monolayers was evaluated in the presence of 0.1 and 1 μM MMF and compared to unstimulated controls. beta1 integrin analysis included alpha1beta1 (CD49a), alpha2beta1 (CD49b), alpha3beta1 (CD49c), alpha4beta1 (CD49d), alpha5beta1 (CD49e), and alpha6beta1 (CD49f) receptors, and was carried out by reverse transcriptase-polymerase chain reaction, confocal microscopy and flow cytometry.

Results

Adhesion of the colon carcinoma cell line HT-29 was strongly reduced in the presence of 0.1 μM MMF. This effect was accompanied by down-regulation of alpha3beta1 and alpha6beta1 surface expression and of alpha3beta1 and alpha6beta1 coding mRNA. Adhesion of the prostate tumor cell line DU-145 was blocked dose-dependently by MMF. In contrast to MMF's effects on HT-29 cells, MMF dose-dependently up-regulated alpha1beta1, alpha2beta1, alpha3beta1, and alpha5beta1 on DU-145 tumor cell membranes.

Conclusion

We conclude that MMF possesses distinct anti-tumoral properties, particularly in colon and prostate carcinoma cells. Adhesion blockage of HT-29 cells was due to the loss of alpha3beta1 and alpha6beta1 surface expression, which might contribute to a reduced invasive behaviour of this tumor entity. The enhancement of integrin beta1 subtypes observed in DU-145 cells possibly causes re-differentiation towards a low-invasive phenotype.