Post-transplant Kaposi sarcoma originates from the seeding of donor-derived progenitors

Post-transplant malignancy: Focusing on virus-associated etiologies, pathogenesis, evidence-based management algorithms, present status of adoptive immunotherapy and future directions

Modern immunosuppression has led to a decrease in rejection rates and improved survival rates after solid organ transplantation. Increasing the potency of immunosuppression promotes post-transplant viral infections and associated cancers by impairing immune response against viruses and cancer immunoediting. This review reflects the magnitude, etiology and immunological characteristics of various virus-related post-transplant malignancies, emphasizing the need for future research. A multidisciplinary and strategic approach may serve best but overall literature evidence targeting it is sparse. However, the authors attempted to provide a more detailed update of the literature consensus for the prevention, diagnosis, management and surveillance of post-transplant viral infections and associated malignancies, with a focus on the current role of adoptive immunotherapy and the way forward. In order to achieve long-term patient and graft survival as well as superior post-transplant outcomes, collaborative research on holistic care of organ recipients is imperative.

Prostate Cancer Stem Cells: Biology and Treatment Implications

Stem cells differentiate into mature organ/tissue-specific cells at a steady pace under normal conditions, but their growth can be accelerated during the process of tissue healing or in the context of certain diseases. It is postulated that the proliferation and growth of carcinomas are sustained by the presence of a vital cellular compartment resembling stem cells residing in normal tissues: 'stem-like cancer cells' or cancer stem cells (CSCs). Mutations in prostate stem cells can lead to the formation of prostate cancer. Prostate CSCs (PCSCs) have been identified and partially characterized. These express surface markers include CD44, CD133, integrin α2β1, and pluripotency factors like OCT4, NANOG, and SOX2. Several signaling pathways are also over-activated, including Notch, PTEN/Akt/PI3K, RAS-RAF-MEK-ERK and HH. Moreover, PCSCs appear to induce resistance to radiotherapy and chemotherapy, while their presence has been linked to aggressive cancer behavior and higher relapse rates. The development of treatment policies to target PCSCs in tumors is appealing as radiotherapy and chemotherapy, through cancer cell killing, trigger tumor repopulation via activated stem cells. Thus, blocking this reactive stem cell mobilization may facilitate a positive outcome through cytotoxic treatment.

Today's Kaposi sarcoma is not the same as it was 40 years ago, or is it?

This review will provide an overview of the notion that Kaposi sarcoma (KS) is a disease that manifests under diverse and divergent circumstances. We begin with a historical introduction of KS and KS-associated herpesvirus (KSHV), highlight the diversity of clinical presentations of KS, summarize what we know about the cell of origin for this tumor, explore KSHV viral load as a potential biomarker for acute KSHV infections and KS-associated complications, and discuss immune modulators that impact KSHV infection, KSHV persistence, and KS disease.

The Kaposi's sarcoma progenitor enigma: KSHV-induced MEndT-EndMT axis

Endothelial-to-mesenchymal transition has been described in tumors as a source of mesenchymal stroma, while the reverse process has been proposed in tumor vasculogenesis and angiogenesis. A human oncogenic virus, Kaposi's sarcoma herpes virus (KSHV), can regulate both processes in order to transit through this transition 'boulevard' when infecting KS oncogenic progenitor cells. Endothelial or mesenchymal circulating progenitor cells can serve as KS oncogenic progenitors recruited by inflammatory cytokines because KSHV can reprogram one into the other through endothelial-to-mesenchymal and mesenchymal-to-endothelial transitions. Through these novel insights, the identity of the potential oncogenic progenitor of KS is revealed while gaining knowledge of the biology of the mesenchymal-endothelial differentiation axis and pointing to this axis as a therapeutic target in KS.

Tumors after kidney transplantation: a population study

One of the main causes of post-transplant-associated morbidity and mortality is cancer. The aims of the project were to study the neoplastic risk within the kidney transplant population and identify the determinants of this risk. A cohort of 462 renal transplant patients from 2010 to 2020 was considered. The expected incidence rates of post-transplant cancer development in the referenced population, the standardized incidence ratios (SIR) taking the Italian population as a comparison, and the absolute risk and the attributable fraction were extrapolated from these cohorts of patients. Kidney transplant recipients had an overall cancer risk of approximately three times that of the local population (SIR 2.8). A significantly increased number of cases were observed for Kaposi's sarcoma (KS) (SIR 195) and hematological cancers (SIR 6.8). In the first 3 years post-transplant, the risk to develop either KS or hematological cancers was four times higher than in the following years; in all cases of KS, the diagnosis was within 2 years from the transplant. Post-transplant immunosuppression represents the cause of 99% of cases of KS and 85% of cases of lymphomas, while only 39% is represented by solid tumors. Data related to the incidence, the percentages attributable to post-transplant immunosuppression, and the time of onset of neoplasms, particularly for KS and hematological tumors could help improve the management for the follow-up in these patients.

KSHV infection of endothelial precursor cells with lymphatic characteristics as a novel model for translational Kaposi's sarcoma studies

Kaposi's sarcoma herpesvirus (KSHV) is the etiologic agent of Kaposi's sarcoma (KS), a hyperplasia consisting of enlarged malformed vasculature and spindle-shaped cells, the main proliferative component of KS. While spindle cells express markers of lymphatic and blood endothelium, the origin of spindle cells is unknown. Endothelial precursor cells have been proposed as the source of spindle cells. We previously identified two types of circulating endothelial colony forming cells (ECFCs), ones that expressed markers of blood endothelium and ones that expressed markers of lymphatic endothelium. Here we examined both blood and lymphatic ECFCs infected with KSHV. Lymphatic ECFCs are significantly more susceptible to KSHV infection than the blood ECFCs and maintain the viral episomes during passage in culture while the blood ECFCs lose the viral episome. Only the KSHV-infected lymphatic ECFCs (K-ECFCLY) grew to small multicellular colonies in soft agar whereas the infected blood ECFCs and all uninfected ECFCs failed to proliferate. The K-ECFCLYs express high levels of SOX18, which supported the maintenance of high copy number of KSHV genomes. When implanted subcutaneously into NSG mice, the K-ECFCLYs persisted in vivo and recapitulated the phenotype of KS tumor cells with high number of viral genome copies and spindling morphology. These spindle cell hallmarks were significantly reduced when mice were treated with SOX18 inhibitor, SM4. These data suggest that KSHV-infected lymphatic ECFCs can be utilized as a KSHV infection model for in vivo translational studies to test novel inhibitors representing potential treatment modalities for KS.

Donor-derived urologic cancers after renal transplantation: A retrospective non-randomized scientific analysis

Background

Malignancies in the urinary tract and the kidney graft are quite common after kidney transplantation. In some selected cases tumours develop from donor-derived tissue.

Objectives

We hypothesised that there is a clinical value to investigate donor/recipient origin in urologic malignancies in renal transplant recipients.

Methods

In this retrospective study, including patients transplanted between the years 1969 and 2014 at Uppsala University Hospital, Sweden, 11 patients with malignancies in urinary tract and 4 patients with malignancies in kidney transplants were investigated. Donor/recipient origin of tumour tissue was analysed by polymerase chain reaction (PCR) of human leucocyte antigen (HLA) genotypes or by fluorescence in situ hybridization (FISH analysis) of sex chromosomes. HLA genotype and sex chromosomes of the tumour were compared to the known HLA genotype and sex chromosomes of recipient and donor.

Results

Three of ten cancers in the urinary tract and three of four cancers in the kidney transplants were donor-derived.

Conclusions

We suggest that urologic malignancies in renal transplant recipients can be investigated for transplant origin. In addition to conventional therapy the allograft immune response against these tumours can be valuable to treat donor-derived cancers.

The lymphatic vascular system: much more than just a sewer

Almost 400 years after the (re)discovery of the lymphatic vascular system (LVS) by Gaspare Aselli (Asellius G. De lactibus, sive lacteis venis, quarto vasorum mesaraicorum genere, novo invento Gasparis Asellii Cremo. Dissertatio. (MDCXXIIX), Milan; 1628.), structure, function, development and evolution of this so-called 'second' vascular system are still enigmatic. Interest in the LVS was low because it was (and is) hardly visible, and its diseases are not as life-threatening as those of the blood vascular system. It is not uncommon for patients with lymphedema to be told that yes, they can live with it. Usually, the functions of the LVS are discussed in terms of fluid homeostasis, uptake of chylomicrons from the gut, and immune cell circulation. However, the broad molecular equipment of lymphatic endothelial cells suggests that they possess many more functions, which are also reflected in the pathophysiology of the system. With some specific exceptions, lymphatics develop in all organs. Although basic structure and function are the same regardless their position in the body wall or the internal organs, there are important site-specific characteristics. We discuss common structure and function of lymphatics; and point to important functions for hyaluronan turn-over, salt balance, coagulation, extracellular matrix production, adipose tissue development and potential appetite regulation, and the influence of hypoxia on the regulation of these functions. Differences with respect to the embryonic origin and molecular equipment between somatic and splanchnic lymphatics are discussed with a side-view on the phylogeny of the LVS. The functions of the lymphatic vasculature are much broader than generally thought, and lymphatic research will have many interesting and surprising aspects to offer in the future.

What Animal Cancers teach us about Human Biology

Cancers in animals present a large, underutilized reservoir of biomedical information with critical implication for human oncology and medicine in general. Discussing two distinct areas of tumour biology in non-human hosts, we highlight the importance of these findings for our current understanding of cancer, before proposing a coordinated strategy to harvest biomedical information from non-human resources and translate it into a clinical setting. First, infectious cancers that can be transmitted as allografts between individual hosts, have been identified in four distinct, unrelated groups, dogs, Tasmanian devils, Syrian hamsters and, surprisingly, marine bivalves. These malignancies might hold the key to improving our understanding of the interaction between tumour cell and immune system and, thus, allow us to devise novel treatment strategies that enhance anti-cancer immunosurveillance, as well as suggesting more effective organ and stem cell transplantation strategies. The existence of these malignancies also highlights the need for increased scrutiny when considering the existence of infectious cancers in humans. Second, it has long been understood that no linear relationship exists between the number of cells within an organism and the cancer incidence rate. To resolve what is known as Peto's Paradox, additional anticancer strategies within different species have to be postulated. These naturally occurring idiosyncrasies to avoid carcinogenesis represent novel potential therapeutic strategies.

Infiltrating Kaposi sarcoma presenting as acute kidney injury: An unexpected consequence of deliberate hepatitis C-positive organ transplantation

Kaposi sarcoma (KS) following kidney transplantation can result from recipient reactivation of latent human herpesvirus 8 (HHV-8) infection or activation of donor-acquired HHV-8 infection. Post-transplant KS typically manifests with cutaneous pathology, but rare cases of renal allograft involvement have been reported. We describe two cases of donor-derived HHV-8 infection in two hepatitis C (HCV) viremia-negative transplant recipients who each received a kidney from a donor with HCV viremia. One recipient did not develop KS while the other presented with acute kidney injury caused by extensive KS infiltration of the renal parenchyma and metastatic disease. This report reviews the literature for cases of KS involving the renal allograft and highlights an unexpected consequence of deliberate HCV-positive organ transplantation.

Concurrent development of HIV-negative Kaposi's sarcoma and mycosis fungoides in an elderly Inuit from Canada

An 88-year-old Inuit man from Northern Canada presented with an extensive skin rash associated with numerous violaceous skin nodules on his palms and lower extremities. Biopsy of a skin nodule revealed Kaposi’s sarcoma (KS), a human herpesvirus 8 (HHV8)-associated malignancy, whereas biopsy of the erythematous skin showed an atypical infiltrate of CD4-positive T-cells that, together with TCR gene rearrangement and presence of clonal T-cells in peripheral blood by flow cytometry, was consistent with a T-cell lymphoma, mycosis fungoides (MF) subtype. Serology was negative for HIV and HTLV-I/II and no immunodeficiency syndrome was identified. The patient was successfully treated with an oral retinoid for KS, and with topical hydrocortisone and ultraviolet B (UVB) phototherapy for MF. This case highlights the existence of HHV8-related lesions in native persons of Northern Canada, and also that MF-induced immunosuppression combined with immunosenescence may play a role in the development of non-HIV-related KS.

Donor-derived infections, lessons learnt from the past, and what is the future going to bring us

PURPOSE OF REVIEW

Donor-derived transmission of infectious diseases is a well-recognized complication of solid organ transplantation (SOT). Most donor-derived disease transmissions are expected. Although uncommon, unexpected donor-derived infections can be associated with significant morbidity and mortality, and as the volume of patients undergoing SOT increases, the number of infections transmitted through organ donation can also be expected to rise. The growing gap between the number of patients waiting for transplantation and available organs continue in fact to be the number one issue facing the transplant community. As a consequence the major focus in organ transplantation has been developing strategies to increase the available organs, including the use of organs from donors with infections or risky behaviors that have disqualified them from the donation in the past.

RECENT FINDINGS

In addition to the commonly reported donor-derived transmissions, an increasing number of studies have reported unusual infections transmitted by SOT.

SUMMARY

Transplant surgeons and physicians should increase their awareness toward uncommon donor-derived infections including them in the differential diagnosis of unusual clinical pictures in their recipients.

Donor-derived Viral Infections in Liver Transplantation

Donor-derived infections are defined as any infection present in the donor that is transmitted to 1 or more recipients. Donor-derived infections can be categorized into 2 groups: "expected" and "unexpected" infections. Expected transmissions occur when the donor is known to have an infection, such as positive serology for cytomegalovirus, Epstein Barr virus, or hepatitis B core antibody, at the time of donation. Unexpected transmissions occur when a donor has no known infection before donation, but 1 or more transplant recipients develop an infection derived from the common donor. Unexpected infections are estimated to occur in far less than 1% of solid organ transplant recipients. We will review the epidemiology, risk factors, and approaches to prevention and management of donor-derived viral infectious disease transmission in liver transplantation.

Kaposi's Sarcoma-Associated Herpesvirus (KSHV)-Associated Disease in the AIDS Patient: An Update

In this book chapter, we review the current knowledge of the biology and pathogenesis of Kaposi's sarcomaassociated herpesvirus (KSHV). We describe the lifecycle of KSHV, the cancers associated with this virus, as well as current treatment modalities.

Infectious Disease Transmission in Solid Organ Transplantation: Donor Evaluation, Recipient Risk, and Outcomes of Transmission

In 2016, the Transplantation Society of Australia and New Zealand, with the support of the Australian Government Organ and Tissue authority, commissioned a literature review on the topic of infectious disease transmission from deceased donors to recipients of solid organ transplants. The purpose of this review was to synthesize evidence on transmission risks, diagnostic test characteristics, and recipient management to inform best-practice clinical guidelines. The final review, presented as a special supplement in Transplantation Direct, collates case reports of transmission events and other peer-reviewed literature, and summarizes current (as of June 2017) international guidelines on donor screening and recipient management. Of particular interest at the time of writing was how to maximize utilization of donors at increased risk for transmission of human immunodeficiency virus, hepatitis C virus, and hepatitis B virus, given the recent developments, including the availability of direct-acting antivirals for hepatitis C virus and improvements in donor screening technologies. The review also covers emerging risks associated with recent epidemics (eg, Zika virus) and the risk of transmission of nonendemic pathogens related to donor travel history or country of origin. Lastly, the implications for recipient consent of expanded utilization of donors at increased risk of blood-borne viral disease transmission are considered.

Cutaneous Complications in Recipients of Lung Transplants: A Pictorial Review

Lung transplant is now an established modality for a broad spectrum of end-stage pulmonary diseases. According to the International Society for Heart and Lung Transplantation Registry, more than 50,000 lung transplants have been performed worldwide, with nearly 11,000 recipients of lung transplants alive in the United States. With the increasing use of lung transplant, pulmonologists must be cognizant of the common as well as the unique posttransplant dermatologic complications. Immunosuppression, infections, and a variety of medications and environmental exposures can contribute to these complications. This review aims to provide representative pictures and describe the pathogenesis, epidemiologic characteristics, and clinical manifestations of dermatologic complications encountered among recipients of lung transplants.

Etiology of increased cancer incidence after solid organ transplantation

Over the past decades, there has been an encouraging increase in survival after solid organ transplantation. However, with longer life spans, more transplant recipients are at risk of dying with functioning grafts from illnesses such as cancer and cardiovascular conditions. Malignancy has emerged as an important cause of death in transplant recipients and is expected to become the leading cause of death in transplanted patients within the next decade. While it is known that solid organ transplant recipients have a three to five-fold increased risk of developing cancer compared with the general population, the mechanisms that lead to the observed excess risk in transplant recipients are less clear. This review explores the etiology of the increased cancer incidence in solid organ transplant including the effect of immunosuppressants on immunosurveillance and activation of oncogenic viruses, and carcinogenic effects of these medications; the role of chronic stimulation of the immune system on the development of cancer; and the impact of pre-existing cancer risk factors and factors related to end-stage organ disease on the cancer excess incidence in solid organ transplant recipients.

Kaposi sarcoma herpesvirus pathogenesis

Kaposi sarcoma herpesvirus (KSHV), taxonomical name human gammaherpesvirus 8, is a phylogenetically old human virus that co-evolved with human populations, but is now only common (seroprevalence greater than 10%) in sub-Saharan Africa, around the Mediterranean Sea, parts of South America and in a few ethnic communities. KSHV causes three human malignancies, Kaposi sarcoma, primary effusion lymphoma, and many cases of the plasmablastic form of multicentric Castleman's disease (MCD) as well as occasional cases of plasmablastic lymphoma arising from MCD; it has also been linked to rare cases of bone marrow failure and hepatitis. As it has colonized humans physiologically for many thousand years, cofactors are needed to allow it to unfold its pathogenic potential. In most cases, these include immune defects of genetic, iatrogenic or infectious origin, and inflammation appears to play an important role in disease development. Our much improved understanding of its life cycle and its role in pathogenesis should now allow us to develop new therapeutic strategies directed against key viral proteins or intracellular pathways that are crucial for virus replication or persistence. Likewise, its limited (for a herpesvirus) distribution and transmission should offer an opportunity for the development and use of a vaccine to prevent transmission.

This article is part of the themed issue ‘Human oncogenic viruses’.

BALB/c mice immunized with a combination of virus-like particles incorporating Kaposi sarcoma-associated herpesvirus (KSHV) envelope glycoproteins gpK8.1, gB, and gH/gL induced comparable serum neutralizing antibody activity to UV-inactivated KSHV

Infection with Kaposi sarcoma-associated herpesvirus (KSHV) is estimated to account for over 44,000 new cases of Kaposi sarcoma annually, with 84% occurring in Africa, where the virus is endemic. To date, there is no prophylactic vaccine against KSHV. KSHV gpK8.1, gB, and gH/gL glycoproteins, implicated in the virus entry into host cells, are attractive vaccine targets for eliciting potent neutralizing antibodies (nAbs) against virus infection. We incorporated gpK8.1, gB, or gH/gL on the surface of virus-like particles (VLPs) and characterized these VLPs for their composition, size, and functionality. To determine which viral glycoprotein(s) elicit the most effective serum-nAbs, we immunized BALB/c mice with gpK8.1, gB, or gH/gL VLPs individually or in combination. Neutralizing antibody assay revealed that sera from mice immunized with the VLPs inhibited KSHV infection of HEK-293 cells in a dose-dependent manner. As a single immunogen, gpK8.1 VLPs stimulated comparable nAb activity to that of UV-inactivated KSHV (UV-KSHV). In contrast, UV-KSHV stimulated higher titers of nAb compared to gB (p = 0.0316) or gH/gL (p = 0.0486). Mice immunized with the combination of gB and gH/gL VLPs had a better nAb response than those immunized with either gB (p = 0.0268), or gH/gL (p = 0.0397) as single VLP immunogens. Immunization with any VLP combination stimulated comparable nAb activity to UV-KSHV serum. Our data provide the first evidence that KSHV gpK8.1, gB, and gH/gL glycoproteins can be incorporated onto the surface of VLPs and used as prophylactic vaccine candidates, with potential to prevent KSHV infection.

Donor-derived Kaposi's sarcoma in a liver-kidney transplant recipient

Human herpes virus 8 (HHV-8), also known as Kaposi's sarcoma associated herpesvirus (KSHV), is an oncogenic virus that can cause Kaposi's sarcoma (KS). KS can develop following organ transplantation through reactivation of the recipient's latent HHV-8 infection, or less commonly through donor-derived infection which has higher risk for severe illness and mortality. We describe a case of probable donor-derived KS in the recipient of a liver-kidney transplant. The donor had multiple risk factors for HHV-8 infection. The KS was successfully treated by switching immunosuppression from tacrolimus to sirolimus. With an increasing number of human immunodeficiency virus (HIV)-positive persons seeking organ transplantation and serving as organ donors for HIV-positive recipients, HHV-8 prevalence among donors and recipients will likely increase and with that the risk for post-transplant KS. Predetermination of HHV-8 status can be useful when considering organ donors and recipients with risk factors, although there are currently no validated commercial tests for HHV-8 antibody screening.

HIV-associated Kaposi sarcoma and related diseases

: The search for the etiologic agent for Kaposi sarcoma led to the discovery of Kaposi sarcoma-associated herpesvirus (KSHV) in 1994. KSHV, also called human herpesvirus-8, has since been shown to be the etiologic agent for several other tumors and diseases, including primary effusion lymphoma (PEL), an extracavitary variant of PEL, KSHV-associated diffuse large B-cell lymphoma, a form of multicentric Castleman disease, and KSHV inflammatory cytokine syndrome. KSHV encodes several genes that interfere with innate and specific immunity, thwart apoptosis, enhance cell proliferation and cytokine production, and promote angiogenesis, and these play important roles in disease pathogenesis. HIV is an important cofactor in Kaposi sarcoma pathogenesis, and widespread use of antiretroviral therapy has reduced Kaposi sarcoma incidence. However, Kaposi sarcoma remains the second most frequent tumor arising in HIV-infected patients in the United States and is particularly common in sub-Saharan Africa. KSHV prevalence varies substantially in different populations. KSHV is secreted in saliva, and public health measures to reduce its spread may help reduce the incidence of KSHV-associated diseases. Although there have been advances in the treatment of Kaposi sarcoma, KSHV-multicentric Castleman disease, and PEL, improved therapies are needed, especially those that are appropriate for Kaposi sarcoma in resource-poor regions.

Diagnosis and Treatment of Kaposi Sarcoma

Kaposi sarcoma (KS) is the most common neoplasm of people living with HIV today. In Sub-Saharan Africa, KS is among the most common cancers in men, overall. Not only HIV-positive individuals present with KS; any immune compromised person infected with KS-associated herpesvirus (KSHV) or human herpesvirus 8 is at risk: the elderly, children in KSHV-endemic areas, and transplant recipients. KS diagnosis is based on detection of the viral protein latency-associated nuclear antigen (LANA) in the biopsy, but not all cases of KS are the same or will respond to the same therapy. Standard KS therapy has not changed in 20 years, but newer modalities are on the horizon and will be discussed.

The Role of Hypoxia and Cancer Stem Cells in Renal Cell Carcinoma Pathogenesis

The cancer stem cell (CSC) model has recently been approached also in renal cell carcinoma (RCC). A few populations of putative renal tumor-initiating cells (TICs) were identified, but they are indifferently understood; however, the first and most thoroughly investigated are CD105-positive CSCs. The article presents a detailed comparison of all renal CSC-like populations identified by now as well as their presumable origin. Hypoxic activation of hypoxia-inducible factors (HIFs) contributes to tumor aggressiveness by multiple molecular pathways, including the governance of immature stem cell-like phenotype and related epithelial-to-mesenchymal transition (EMT)/de-differentiation, and, as a result, poor prognosis. Due to intrinsic von Hippel-Lindau protein (pVHL) loss of function, clear-cell RCC (ccRCC) develops unique pathological intra-cellular pseudo-hypoxic phenotype with a constant HIF activation, regardless of oxygen level. Despite satisfactory evidence concerning pseudo-hypoxia importance in RCC biology, its influence on putative renal CSC-like largely remains unknown. Thus, the article discusses a current knowledge of HIF-1α/2α signaling pathways in the promotion of undifferentiated tumor phenotype in general, including some experimental findings specific for pseudo-hypoxic ccRCC, mostly dependent from HIF-2α oncogenic functions. Existing gaps in understanding both putative renal CSCs and their potential connection with hypoxia need to be filled in order to propose breakthrough strategies for RCC treatment.

Chronic and recurrent benign lymphadenopathy without constitutional symptoms associated with human herpesvirus-6B reactivation

Chronic/recurrent behaviour may be encountered in some distinct atypical or malignant lymphoproliferations, while recurrences are not generally observed in reactive/benign lymphadenopathies. We retrospectively analysed a consecutive series of 486 human immunodeficiency virus-negative adults, who underwent lymphadenectomy. Neoplastic and benign/reactive histopathological pictures were documented in 299 (61·5%) and 187 (38·5%) cases, respectively. Of note, seven of the 111 (6·3%) patients with benign lymphadenopathy without well-defined aetiology, showed chronic/recurrent behaviour, without constitutional symptoms. Enlarged lymph nodes were round in shape and hypoechoic, mimicking lymphoma. Reactive follicular hyperplasia and paracortical expansion were observed. Human herpesvirus (HHV)-6B positive staining in follicular dendritic cells (FDCs) was documented in all seven patients. Serological, molecular and immunological examinations suggested HHV-6B reactivation. Among the remaining 104 cases with reactive lymphoid hyperplasia in the absence of well-known aetiology and without recurrences, positivity for HHV-6B on FDCs was found in three cases, whereas in seven further patients, a scanty positivity was documented in rare, scattered cells in inter-follicular regions. Immunohistochemistry for HHV-6A and HHV-6B was invariably negative on 134 lymph nodes, with either benign pictures with known aetiology or malignant lymphoproliferative disorders, tested as further controls. Future studies are warranted to investigate a potential association between HHV-6B reactivation and chronic/recurrent benign lymphadenopathy.

Kaposi sarcoma-associated herpesvirus-associated malignancies: epidemiology, pathogenesis, and advances in treatment

Kaposi sarcoma associated herpesvirus (KSHV), a γ2-herpesvirus, also known as human herpesvirus-8, is the etiologic agent of three virally associated tumors: Kaposi sarcoma, a plasmablastic form of multicentric Castleman disease (KSHV-MCD), and primary effusion lymphoma. These malignancies are predominantly seen in people with acquired immunodeficiencies, including acquired immunodeficiency syndrome and iatrogenic immunosuppression in the setting of organ transplantation, but can also develop in the elderly. Kaposi sarcoma (KS) is most frequent in regions with high KSHV seroprevalence, such as sub-Saharan Africa and some Mediterranean countries. In the era of combination antiviral therapy, inflammatory manifestations associated with KSHV-infection, including KSHV-MCD, a recently described KSHV-associated inflammatory cytokine syndrome and KS immune reconstitution syndrome also are increasingly appreciated. Our understanding of viral and immune mechanisms of oncogenesis continues to expand and lead to improved molecular diagnostics, as well as novel therapeutic strategies that employ immune modulatory agents, manipulations of the tumor microenvironment, virus-activated cytotoxic therapy, or agents that target interactions between specific virus-host cell signaling pathways. This review focuses on the epidemiology and advances in molecular and clinical research that reflects the current understanding of viral oncogenesis, clinical manifestations, and therapeutics for KSHV-associated tumors.

KSHV: pathways to tumorigenesis and persistent infection

Kaposi's sarcoma-associated herpesvirus (KSHV; also known as human herpesvirus 8) is the etiologic agent of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. These cancers often occur in the context of immunosuppression, which has made KSHV-associated malignancies an increasing global health concern with the persistence of the AIDS epidemic. KSHV has also been linked to several acute inflammatory diseases. KSHV exists between a lytic and latent lifecycle, which allows the virus to transition between active replication and quiescent infection. KSHV encodes a number of proteins and small RNAs that are thought to inadvertently transform host cells while performing their functions of helping the virus persist in the infected host. KSHV also has an arsenal of components that aid the virus in evading the host immune response, which help the virus establish a successful lifelong infection. In this comprehensive chapter, we will discuss the diseases associated with KSHV infection, the biology of latent and lytic infection, and individual proteins and microRNAs that are known to contribute to host cell transformation and immune evasion.

Transplantation: Donor-derived skin cancer in a kidney transplant recipient

Skin carcinomas, triggered by ultraviolet light, commonly develop post-transplantation and are associated with substantial morbidity and mortality. A recent study in kidney transplant recipients has shown that some of these tumours arise from donor-derived cells. This phenomenon is interesting for the study of carcinogenesis, although its effect on clinical practice is unknown.

Cellular origin of Kaposi's sarcoma and Kaposi's sarcoma-associated herpesvirus-induced cell reprogramming

Kaposi's sarcoma (KS) is the most common malignancy in untreated HIV patients. KS is characterised by abnormal neoangiogenesis, inflammation, and proliferation of tumour cells [KS spindle cells (SCs)]. Kaposi's sarcoma-associated herpesvirus (KSHV) is the aetiological agent of KS. KS SCs are the predominant KSHV-infected cells in KS lesions. In this review, we report advances in understanding of the cellular origin of the KS SC, a contentious topic in KSHV research. KS SCs are now known to be of endothelial cell (EC) origin, phenotypically most similar to lymphatic ECs (LECs), but poorly differentiated. We focus on recent insights into KSHV's ability to exploit the normal differentiation pathway and intrinsic plasticity of ECs, through manipulation of EC-specific transcriptional regulators [i.e., prospero homeobox 1 (PROX1) and MAF] and discuss how this may contribute to viral persistence and KS sarcomagenesis.

Human herpesviruses 6, 7 and 8 in solid organ transplant recipients

Human herpesviruses (HHV) 6 and 7 are ubiquitous infections that reactivate commonly in transplant recipients. However, clinical diseases due to these viruses are reported only in 1% of solid organ transplant recipients. Fever, rash and bone marrow suppression are the most common manifestations, but symptoms of tissue invasive disease may be observed. Treatment of HHV-6 and HHV-7 disease includes antiviral therapy and cautious reduction in immunosuppression. HHV-8 is an oncogenic gamma-herpesvirus that causes Kaposi's sarcoma, Castleman's disease and primary effusion lymphomas in transplant recipients. Nonmalignant diseases such as bone marrow suppression and multiorgan failure have also been associated with HHV-8. Reduction in immunosuppression is the first line treatment of HHV-8 infection. Other alternatives for treatment, especially for HHV-8 diseases not responsive to immuno-minimization strategies, are surgery and chemotherapy. Sirolimus has been shown to be a beneficial component for the treatment of Kaposi's sarcoma and the role of antivirals for HHV-8 infection is being investigated.

Human herpesviruses 6, 7, and 8 from a dermatologic perspective

Human herpesviruses (HHVs) have frequently been suspected as etiologic agents or cofactors in cutaneous disease. However, clearly established associations are rare. Investigations into an etiologic association between HHVs and cutaneous disease are complicated by the ubiquity and nearly universal prevalence of some herpesviruses. This article summarizes the associations between cutaneous disease and HHV-6, HHV-7, and HHV-8. In addition to a personal library of references, the PubMed database of biomedical literature was searched using the following Medical Subject Heading terms: HHV-6, HHV-7, and HHV-8, each in conjunction with cutaneous manifestations, virology, epidemiology, dermatopathology, and therapeutics, between 1998 and March 2011. Free-text searches with known or suspected disease associations were added for broader coverage. The results have been summarized to provide a practical review for the physician likely to encounter cutaneous diseases.

How I treat HHV8/KSHV-related diseases in posttransplant patients

Posttransplantation human herpesvirus-8 (HHV8)/Kaposi sarcoma herpesvirus (KSHV) primary infection and/or reactivations are associated with uncommon and sometimes fatal, neoplastic, and non-neoplastic diseases. HHV8-related clinical manifestations notably range from Kaposi sarcoma (KS) to either primary effusion lymphoma or multicentric Castleman disease B-cell malignancies, and from polyclonal HHV8-positive plasmacytic lymphoproliferative disorders to bone marrow failure and peripheral cytopenias, associated or not with hemophagocytic syndromes, and to acute hepatitis syndromes. We reviewed the patient series reported in the literature and summarized clinical management aspects, in terms of diagnosis, follow-up, and treatment. We described typical clinical presentations and histopathologic diagnostic features of these diseases, and we discussed the role of HHV8-specific serologic, molecular, and immunologic assays, particularly focusing on recent data from HHV8-specific T-cell monitoring in posttransplantation KS patients. We finally discussed actual therapeutic options, namely, the reduction or discontinuation of immunosuppressive therapy or the switch from calcineurin inhibitors to mTOR inhibitors, as alternatives to antineoplastic chemotherapy, along with the use of antiherpesvirus agents as prophylactic or therapeutic measures, and treatment with rituximab in posttrans-plantation multicentric Castleman disease patients and non-neoplastic HHV8-associated syndromes.

Vaccine prospect of Kaposi sarcoma-associated herpesvirus

Infection of Kaposi sarcoma-associated herpesvirus (KSHV) or human herpesvirus-8 (HHV-8) is estimated to account for 34,000 new cancer cases globally. Unlike other herpesviruses, KSHV is not ubiquitous but is highly prevalent in some areas, such as sub-Saharan Africa where Kaposi sarcoma is the leading cancer among adults. While latent infection of KSHV plays a major and direct role in tumorigenesis, viral lytic replication also makes significant contributions to this process. Efforts to develop a KSHV vaccine are limited, but studies with EBV have provided important lessons. Informative vaccine research has been conducted in the mouse infection model of a closely related rodent virus, murine gammaherpesvirus-68 (MHV-68 or γHV-68). This mouse model has generated fundamental principles for an effective vaccination strategy. KSHV vaccines designed to prevent a naïve host from infection and to boost the immune control of KSHV in persistently infected people will have major impact on individuals who are at a high risk of developing KSHV-associated diseases.

Mesenchymal stem cell-like cells in classic renal angiomyolipoma

As a benign mesenchymal tumor, classic renal angiomyolipoma (AML) may obliterate the kidney parenchyma and cause renal hemorrhage. It has previously been reported that mesenchymal stem cells (MSCs) are involved in tumorigenesis; however, there have been no studies on stem cells with renal AML origin. In the present study, six females with classic renal AML received a partial or total nephrectomy. During surgery, tumor tissues were collected and culture expansion of adhesive fibroblastoid cells from these tissues was performed. We successfully isolated and cultured MSC-like cells from all six renal AML tumors. MSC characteristics, including morphology, immunophenotype and multidifferentiation potential were analyzed. Flow cytometry analysis revealed that these cells are highly similar to human bone marrow MSCs due to the expression of MSC-specific surface proteins, including CD29, CD44, CD73, CD90 and CD105. The stem cell-like nature of these cells is further supported by their adipogenic and osteogenic differentiation potentials when incubated in appropriate differentiation cocktails. Renal AML-derived adhesive cells possessing the characteristics of MSCs are described for the first time. They are a novel cell type which may be useful in future studies with regards to determining the role of stem cells in the formation and development of renal AML.

Treatment of Kaposi sarcoma-associated herpesvirus-associated cancers

Kaposi sarcoma (KS) is the most frequent AIDS-defining cancer worldwide. KS-associated herpesvirus (KSHV) is the etiological agent of KS, and the virus is also associated with two lymphoproliferative diseases. Both KS and KSHV-associated lymphomas, are cancers of unique molecular composition. They represent a challenge for cancer treatment and an opportunity to identify new mechanisms of transformation. Here, we review the current clinical insights into KSHV-associated cancers and discuss scientific insights into the pathobiology of KS, primary effusion lymphoma, and multicentric Castleman's disease.

Risk factors in the development of stem cell therapy

Stem cell therapy holds the promise to treat degenerative diseases, cancer and repair of damaged tissues for which there are currently no or limited therapeutic options. The potential of stem cell therapies has long been recognised and the creation of induced pluripotent stem cells (iPSC) has boosted the stem cell field leading to increasing development and scientific knowledge. Despite the clinical potential of stem cell based medicinal products there are also potential and unanticipated risks. These risks deserve a thorough discussion within the perspective of current scientific knowledge and experience. Evaluation of potential risks should be a prerequisite step before clinical use of stem cell based medicinal products.

The risk profile of stem cell based medicinal products depends on many risk factors, which include the type of stem cells, their differentiation status and proliferation capacity, the route of administration, the intended location, in vitro culture and/or other manipulation steps, irreversibility of treatment, need/possibility for concurrent tissue regeneration in case of irreversible tissue loss, and long-term survival of engrafted cells. Together these factors determine the risk profile associated with a stem cell based medicinal product. The identified risks (i.e. risks identified in clinical experience) or potential/theoretical risks (i.e. risks observed in animal studies) include tumour formation, unwanted immune responses and the transmission of adventitious agents.

Currently, there is no clinical experience with pluripotent stem cells (i.e. embryonal stem cells and iPSC). Based on their characteristics of unlimited self-renewal and high proliferation rate the risks associated with a product containing these cells (e.g. risk on tumour formation) are considered high, if not perceived to be unacceptable. In contrast, the vast majority of small-sized clinical trials conducted with mesenchymal stem/stromal cells (MSC) in regenerative medicine applications has not reported major health concerns, suggesting that MSC therapies could be relatively safe. However, in some clinical trials serious adverse events have been reported, which emphasizes the need for additional knowledge, particularly with regard to biological mechanisms and long term safety.

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.

Do fewer cases of Kaposi's sarcoma in HIV-infected patients reflect a decrease in HHV8 seroprevalence?

Infection with human herpes virus 8 (HHV8) is associated with development of Kaposi's sarcoma (KS); therefore also known as KS-associated herpes virus. KS is closely associated with human immunodeficiency virus (HIV) infection, and consequently HHV8 seroprevalence is higher in HIV-infected compared to HIV-negative patients. Currently, KS is rarely seen in clinical practice, which might be a consequence of an optimized anti-HIV treatment leading to an improved immunological status, or alternatively of a decrease in HHV8 prevalence. To determine the prevalence of HHV8 antibodies in HIV-positive compared to HIV-negative patients from the University Hospital Frankfurt/Main, Germany, and to compare our results with previously published data to illustrate trends in the spread of infection. Hundred serum samples each of HIV-positive and HIV-negative patients were analyzed for HHV8 antibodies by using an IgG immunofluorescence test. The overall HHV8 seroprevalence was 16% with no statistically significant gender-specific differences; however, the distribution between the HIV-infected patients and the HIV-negative control group was significantly different (30 and 2%, respectively). The highest rate of seroprevalence in HIV-infected patients was detected at the age of 40-49 (42%) and the lowest rate at the age of 20-29 years (16.6%). In comparison with formerly conducted studies, our data clearly showed an increase in the HHV8 seroprevalence in HIV-infected patients, both in men and women. Therefore, we conclude that the low rate of clinical KS is associated with an improved immunological status due to an optimized anti-HIV therapy.

Contagious cancer

Although cancer can on occasion be caused by infectious agents such as specific bacteria, parasites, and viruses, it is not generally considered a transmissible disease. In rare circumstances, however, direct communication from one host to another has been documented. The Tasmanian devil is now threatened with extinction in the wild because of a fatal transmissible cancer, devil facial tumor disease (DFTD). Another example is canine transmissible venereal tumor (CTVT or Sticker's sarcoma) in dogs. There is a vast difference in prognosis between these two conditions. DFTD is often fatal within 6 months, whereas most cases of CTVT are eventually rejected by the host dog, who then is conferred lifelong immunity. In man, only scattered case reports exist about such communicable cancers, most often in the setting of organ or hematopoietic stem cell transplants and cancers arising during pregnancy that are transmitted to the fetus. In about one third of cases, transplant recipients develop cancers from donor organs from individuals who were found to harbor malignancies after the transplantation. The fact that two thirds of the time cancer does not develop, along with the fact that cancer very rarely is transmitted from person to person, supports the notion that natural immunity prevents such cancers from taking hold in man. These observations might hold invaluable clues to the immunobiology and possible immunotherapy of cancer.

Kaposi's sarcoma and its associated herpesvirus

Kaposi's sarcoma (KS) is the most common cancer in HIV-infected untreated individuals. Kaposi's sarcoma-associated herpesvirus (KSHV; also known as human herpesvirus 8 (HHV8)) is the infectious cause of this neoplasm. In this Review we describe the epidemiology of KS and KSHV, and the insights into the remarkable mechanisms through which KSHV can induce KS that have been gained in the past 16 years. KSHV latent transcripts, such as latency-associated nuclear antigen (LANA), viral cyclin, viral FLIP and viral-encoded microRNAs, drive cell proliferation and prevent apoptosis, whereas KSHV lytic proteins, such as viral G protein-coupled receptor, K1 and virally encoded cytokines (viral interleukin-6 and viral chemokines) further contribute to the unique angioproliferative and inflammatory KS lesions through a mechanism called paracrine neoplasia.