Lymphoproliferative disorders after solid organ transplantation-classification, incidence, risk factors, early detection and treatment options

Posttransplant lymphoproliferative disorder (PTLD) is a heterogeneous disease group of benign and malignant entities. The new World Health Organisation classification introduced in 2008 distinguishes early lesions, polymorphic, monomorphic and classical Hodgkin lymphoma-type PTLD. Based on the time of appearance, early and late forms can be identified.PTLDs are the second most frequent posttransplantation tumors in adulthood, and the most frequent ones in childhood. The incidence varies with the transplanted organ-from 1%-2% following kidney transplantation to as high as 10% following thoracic organ transplantation-due to different intensities in immunosuppression. Immunocompromised state and Epstein-Barr virus (EBV) infection are the two major risk factors.In Europe and the US approximately 85% of PTLDs are of B-cell origin, and the majority are EBV-associated. Symptoms are often unspecific; extranodal, organ manifestations and central nervous system involvement is common. Early lesions respond well to a decrease in immunosuppression. Malignant entities are treated with rituximab, chemotherapy, radiotherapy and surgical therapy. Adoptive T-cell transfer represents a promising therapeutic approach. The prognosis is favorable in early PTLD, and poor in late PTLD. Five-year survival is 30% for high-grade lymphomas. The prognosis of EBV-negative lymphomas is worse.Lowering the risk of PTLD may be achieved by low dose maintenance immunosuppression, immunosuppressive drugs inhibiting cell proliferation, and special immunotherapy (e.g. interleukin-2 inhibitors). Early detection is especially important for high risk-e.g. EBV-negative-patients, where the appearance of EBV-DNA and the increase in its titer may help.

[Post-transplantation malignant tumors and the challenges of immunosuppressive therapy in transplanted patients developing lymphoma. Mycophenolic acid as a possibility]

The increasing frequency of malignant tumors developing during chronic immunosuppression is an important determinant of the long-term survival of organ transplanted patients. This problem can be solved only if we are aware of the special characteristics concerning our patients. The incidence and frequency of tumors occurring in kidney transplant recipients differ from those of the Hungarian population. The increased tumor risk resulting from chronic renal failure, increasing age of prospective kidney recipients and, in addition, the increasing frequency of tumors diagnosed in the early post-transplantation period emphasize the importance of regular oncological screening of patients on the waiting list. Early diagnosis and treatment of tumors and precancerous conditions are equally important in transplanted patients as well, and the tumor risk could be decreased by applying low dose immunosuppression and the preferential usage of immunosuppressive drugs with an oncologically favorable effect. The prognosis of post-transplantation tumors is poor, as they respond poorly to therapy. Lymphomas are of great importance because of their frequency. Different immunosuppressive regimens represent varying degrees of risk in lymphoma development. This risk is lower in the case of mycophenolic acid. The composition of immunosuppression is a major factor in treatment; an oncologically ideal compound would prevent organ rejection and, at the same time, would not counteract oncological therapy. We have shown that mycophenolic acid inhibits the proliferation of human B-cell non-Hodgkin lymphomas and induces apoptosis by activating the intrinsic pathway, both in vitro and in vivo. The favorable properties of mycophenolic acid suggest that it can provide the necessary immunoprotection for the transplanted organ and, given its anti-lymphoma effects, it may also prove useful in the therapy of lymphoma patients. It may also be helpful in the treatment of "traditional" lymphomas of the non-transplanted population, where the major cause of therapeutical failure is the development of apoptosis resistance. Mycophenolic acid, combined with other chemotherapeutical drugs, may enhance apoptosis in lymphoma cells. Our promising experimental results provide a basis for further, clinical studies.

Antiproliferative and apoptotic effects of mycophenolic acid in human B-cell non-Hodgkin lymphomas

Mycophenolic acid (MPA)/mycophenolate mofetil (MMF), a powerful immunosuppressive agent was tested on human B-lymphoma cells (Epstein-Barr virus +/-) in vitro and in SCID mouse xenograft model. Proliferation, apoptotic activity and tumor volume were evaluated. MPA inhibited lymphoma cell proliferation and induced apoptosis (50-60% at 72 h). In vivo, oral administration significantly inhibited subcutaneous tumor growth. Immunohistochemistry showed significantly decreased proliferation rate and higher apoptotic activity in tumors treated with MMF. Xenografted lymphoma cells remained sensitive to MPA. Our results suggest that MPA may be recommended as an additional component of lymphoma chemotherapeutical regimens, with special considerations to post-transplant lymphomas.

Malignancies after renal transplantation during 33 years at a single center

This study provides an analysis of incidence and characteristics of malignant tumors of 2535 patients who underwent renal transplantation between 1973 and 2007 at the Transplantation Center in Budapest. One hundred ninety-three malignant diseases were found in 188 patients (7.6%). The incidence of thyroid-, renal- hepatic-, skin- and gastric cancers as well as of Kaposi sarcoma and lymphomas increased in our transplant patient cohort compared to the figures of the general population based on the data of our Cancer Registry. On the other hand, colorectal-, oralprostate and lung cancers were underrepresented in our patient cohort. The mean time of diagnosis of malignancies following kidney transplantation was 58.5+/-44.8 months. One fifth of the tumors were detected within the first year. Patients with malignancies were distributed into four groups based on the immunosuppressive regimen: group I (8.5%), azathioprine + prednisone; group II (59.0%), cyclosporine + prednisone; group III (26.6%), cyclosporine + mycophenolate mofetil + prednisone; group IV (5.9%), tacrolimus + mycophenolate mofetil + prednisone. The mean age of patients was 47.3, 53.5, 55.5 and 58.1 years in group I, II, III and IV, respectively. Oncologic and immunosuppressive therapy was decided individually. Immunosuppression was switched to rapamycin-containing regimens in 63 cases. We lost 92 patients (48.9%) with a mean survival time of 25.8+/-39.4 months. Cumulative 1- and 5-year survivals were 69.5% and 52%, respectively. The increasing number of cancers seen early after transplantation and the increased risk of developing a cancer due to the older age of recipients draw attention to the importance of regular oncologic screening in patients on the waiting list and after transplantation.

Apoptosis and p53, Bcl-2 and bax gene expression in parathyroid glands of patients with hyperparathyroidism

Altogether 107 patients were operated on at the Department of Transplantation and Surgery of Semmelweis University in the past four years, for clinical symptoms of hyperparathyroidism. Clinical and laboratory data of the patients supported the diagnosis of primary or secondary hyperparathyroidism. Chronically impaired renal function was found in 52 cases. The removed parathyroid glands showed hyperplasia in 54, adenoma in 50 and carcinoma in 3 cases. The majority of parathyroid lesions in primary hyperparathyroidism were adenomas (41 cases) and in secondary hyperparathyroidism were hyperplasias (43 cases). The ratio of oxyphil to chief cells as well as occasional mitotic and apoptotic figures were determined. The oxyphil component was present in both hyperplastic and tumorous lesions. Apoptosis and mitosis were rarely seen in hyperplasias and adenomas (under 2%), whereas in carcinomas 3% of the tumor cells were apoptotic and 4% showed mitosis. Cytoplasmic p53 positivity could be observed in 3 of the adenomas and in 2 of the hyperplasias. The carcinomas, four adenomas and 3 hyperplasias showed nuclear p53 positivity. Bcl-2 and Bax were detected in the cytoplasm of the tumor cells in the majority of adenomas and in the cells of hyperplasias. Oxyphil cells were more frequently positive than chief cells or clear cells. Colocalization of Bcl-2 and Bax was found randomly in all types of lesions. The very low incidence of carcinoma, the low mitotic and apoptotic ratio in adenomas and hyperplasias suggest a potent antiproliferative defense mechanism in the parathyroid cell population. This may also be reflected in the cytoplasmic colocalization of various gene products which regulate cell death and cell proliferation. No significant differences in the p53, Bcl-2 and Bax spectrum were found between the primary and secondary (i.e. renal failure) parathyroid alterations.