Effect of immunosuppressive drugs on spontaneous DNA repair in human peripheral blood mononuclear cells

Human Variation in DNA Repair, Immune Function, and Cancer Risk

DNA damage constantly threatens genome integrity, and DNA repair deficiency is associated with increased cancer risk. An intuitive and widely accepted explanation for this relationship is that unrepaired DNA damage leads to carcinogenesis due to the accumulation of mutations in somatic cells. But DNA repair also plays key roles in the function of immune cells, and immunodeficiency is an important risk factor for many cancers. Thus, it is possible that emerging links between inter-individual variation in DNA repair capacity and cancer risk are driven, at least in part, by variation in immune function, but this idea is underexplored. In this review we present an overview of the current understanding of the links between cancer risk and both inter-individual variation in DNA repair capacity and inter-individual variation in immune function. We discuss factors that play a role in both types of variability, including age, lifestyle, and environmental exposures. In conclusion, we propose a research paradigm that incorporates functional studies of both genome integrity and the immune system to predict cancer risk and lay the groundwork for personalized prevention.

Calcineurin inhibitor (CNI)-associated skin cancers: New insights on exploring mechanisms by which CNIs downregulate DNA repair machinery

The use of the calcineurin inhibitors (CNI) cyclosporine (CsA) and tacrolimus remains a cornerstone in post-transplantation immunosuppression. Although these immunosuppressive agents have revolutionized the field of transplantation medicine, its increased skin cancer risk poses a major concern. A key contributor to this phenomenon is a reduced capacity to repair DNA damage caused by exposure to ultraviolet (UV) wavelengths of sunlight. CNIs decrease DNA repair by mechanisms that remain to be fully explored. Though CsA is known to decrease the abundance of key DNA repair enzymes, less is known about how tacrolimus yields this effect. CNIs hold the capacity to inhibit both of the main catalytic calcineurin isoforms (CnAα and CnAβ). However, it is unknown which isoform regulates UV-induced DNA repair, which is the focus of this review. It is with hope that this insight spurs investigative efforts that conclusively addresses these gaps in knowledge. Additionally, this research also raises the possibility that newer CNIs can be developed that effectively blunt the immune response while mitigating the incidence of skin cancers with immunosuppression.

Human papillomavirus infection in solid organ transplant recipients: Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These guidelines from the American Society of Transplantation Infectious Diseases Community of Practice update the epidemiology and management of human papillomavirus (HPV) infections in organ transplant recipients. HPV is one of the most common sexually transmitted infections and is associated with cancers of the anogenital region. Increasing evidence suggests an association with head and neck cancers as well. Solid organ transplant recipients have a higher risk of HPV infection than the general population. Infection manifests as premalignant lesions, warts, or cancer of the cervix, penis, vulva, scrotum, and anal canal. Most are asymptomatic initially, so diagnosis can be difficult without screening. A vaccine is available though not effective in preventing all cancer-causing strains. Organ transplant recipients should be screened for HPV-associated cancers and appropriate therapy initiated in a timely manner. Further studies are warranted to delineate the most effective screening methods and therapeutic modalities, including whether changes in immunosuppression are effective in attenuating disease.

Dissecting the Multiplicity of Immune Effects of Immunosuppressive Drugs to Better Predict the Risk of de novo Malignancies in Solid Organ Transplant Patients

De novo malignancies constitute an emerging cause of morbidity after solid organ transplant (SOT), significantly affecting the long-term survival of transplant recipients. Pharmacologic immunosuppression may functionally impair the immunosurveillance in these patients, thereby increasing the risk of cancer development. Nevertheless, the multiplicity and heterogeneity of the immune effects induced by immunosuppressive drugs limit the current possibilities to reliably predict the risk of de novo malignancy in SOT patients. Therefore, there is the pressing need to better characterize the immune dysfunctions induced by the different immunosuppressive regimens administered to prevent allograft rejection to tailor more precisely the therapeutic schedule and decrease the risk of de novo malignancies. We herein highlight the impact exerted by different classes of immunosuppressants on the most relevant immune cells, with a particular focus on the effects on dendritic cells (DCs), the main regulators of the balance between immunosurveillance and tolerance.

Post-transplantation malignancies: here today, gone tomorrow?

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

Human Beta-papillomavirus infection and keratinocyte carcinomas

Although the role of oncogenic human Alpha-papillomaviruses (HPVs) in the development of mucosal carcinomas at different body sites (eg cervix, anus, oropharynx) is fully recognized, a role for HPV in keratinocyte carcinomas (KCs; basal and squamous cell carcinomas) of the skin is not yet clear. KCs are the most common cancers in Caucasians, with the major risk factor being ultraviolet (UV) light exposure. A possible role for Beta-HPV types (BetaPV) in the development of KC was suggested several decades ago, supported by a number of epidemiological studies. Our current review summarizes the recent molecular and histopathological evidence in support of a causal association between BetaPV and the development of KC, and outlines the suspected synergistic effect of viral gene expression with UV radiation and immune suppression. Further insights into the molecular pathways and protein interactions used by BetaPV and the host cell is likely to extend our understanding of the role of BetaPV in KC.

HPV Carcinomas in Immunocompromised Patients

Human papillomavirus (HPV) infection is the most common sexually transmitted disease worldwide and can result in pre-malignancies or overt malignancies of the skin and mucosal surfaces. HPV-related illnesses are an important personal and public health problem causing physical, mental, sexual and financial detriments. Moreover, this set of malignancies severely affects the immunosuppressed population, particularly HIV-positive patients and organ-transplant recipients. There is growing incidence of HPV-associated anogenital malignancies as well as a decrease in the average age of affected patients, likely related to the rising number of high-risk individuals. Squamous cell carcinoma is the most common type of HPV-related malignancy. Current treatment options for HPV infection and subsequent disease manifestations include imiquimod, retinoids, intralesional bleomycin, and cidofovir; however, primary prevention with HPV vaccination remains the most effective strategy. This review will discuss anogenital lesions in immunocompromised patients, cutaneous warts at nongenital sites, the association of HPV with skin cancer in immunocompromised patients, warts and carcinomas in organ-transplant patients, HIV-positive patients with HPV infections, and the management of cutaneous disease in the immunocompromised patient.

Intra-abdominal localisation of a buschke-lowenstein tumour: case presentation and review of the literature

Giant condyloma acuminatum or Buschke-Lowenstein tumour is a very rare disease which usually is located in the genital, anorectal, and perianal regions. It is regarded as a type of verrucous carcinoma occurring on anogenital mucosal surfaces where it is locally invasive but displays a benign cytology. We describe a case of a 24-year-old woman with persisting condyloma acuminata progressing to a large intra-abdominal Buschke-Lowenstein tumour. To our knowledge such an advanced stage has only been reported once before. The severity and extent of the tumour both determine the treatment and patient outcome. Treatment was impeded by cachexia, an immunosuppressive state after kidney transplantation and difficulties in establishing a reliable diagnose. Interferon treatment was started which initially led to tumour reduction but was complicated by an interferon-induced pancreatitis, pneumonia, and fasciitis necroticans resulting in death. We present a literature overview on the treatment options for a Buschke-Lowenstein tumour, with emphasis on interferon therapy, with all the advantages and disadvantages.

Papillomavirus-associated squamous skin cancers following transplant immunosuppression: one Notch closer to control

The frequent occurrence of cutaneous squamous cell carcinomas (SCCs) containing weakly tumorigenic human papillomaviruses (HPVs) following iatrogenic immunosuppression for organ transplantation remains incompletely understood. Here we address this problem in the light of recent insights into (1) the association of low-risk β-HPVs with skin SCCs in the rare genetic syndromes of epidermodysplasia verruciformis and xeroderma pigmentosum, (2) the frequent recovery of post-transplant tumor control on substituting calcineurin-inhibitory with mTOR-inhibitory immunosuppression, (3) the unexpectedly favorable prognosis of node-positive SCCs containing high-risk α-HPVs originating in the activated immune niche of the oropharynx, (4) the rapid occurrence of HPV-negative SCCs in ultraviolet (UV)-damaged skin of melanoma patients receiving Raf-inhibitory drugs, and (5) the selective ability of β-HPV E6 oncoproteins to inhibit Notch tumor-suppressive signaling in cutaneous and mesenchymal tissues. The crosstalk so implied between oncogenic UV-induced mutations, defective host immunity, and β-HPV-dependent stromal-epithelial signaling suggests that immunosuppressants such as calcineurin inhibitors intensify mitogenic signalling in TP53-mutant keratinocytes while also abrogating immune-dependent Notch-mediated tumor repression. This emerging interplay between solar damage, viral homeostasis and immune control makes it timely to reappraise strategies for managing skin SCCs in transplant patients.

Oxidative stress-induced DNA damage and repair in human peripheral blood mononuclear cells: protective role of hemoglobin

BACKGROUND

DNA repair is a cellular defence mechanism responding to DNA damage caused in large part by oxidative stress. There is a controversy with regard to the effect of red blood cells on DNA damage and cellular response.

AIM

To investigate the effect of red blood cells on H2O2-induced DNA damage and repair in human peripheral blood mononuclear cells.

METHODS

DNA breaks were induced in peripheral blood mononuclear cells by H2O2 in the absence or presence of red blood cells, red blood cells hemolysate or hemoglobin. DNA repair was measured by (3)H-thymidine uptake, % double-stranded DNA was measured by fluorometric assay of DNA unwinding. DNA damage was measured by the comet assay and by the detection of histone H2AX phosphorylation.

RESULTS

Red blood cells and red blood cells hemolysate reduced DNA repair in a dose-dependent manner. Red blood cells hemolysate reduced % double-stranded DNA, DNA damage and phosphorylation of histone H2AX. Hemoglobin had the same effect as red blood cells hemolysate on % double-stranded DNA.

CONCLUSION

Red blood cells, via red blood cells hemolysate and hemoglobin, reduced the effect of oxidative stress on peripheral blood mononuclear cell DNA damage and phosphorylation of histone H2AX. Consequently, recruitment of DNA repair proteins diminished with reduction of DNA repair. This suggests that anemia predisposes to increased oxidative stress induced DNA damage, while a higher hemoglobin level provides protection against oxidative-stress-induced DNA damage.

CSACI position statement: safety of topical calcineurin inhibitors in the management of atopic dermatitis in children and adults

Atopic dermatitis (AD) is a condition frequently encountered in medical practices across the country. Arming ourselves with appropriate and safe treatment modalities to provide relief for this chronic and relapsing inflammatory condition is of utmost importance to our patients and their families. Utilizing topical calcineurin inhibitors (TCIs) for the treatment of AD not responsive to high-potency corticosteroids, or low-potency corticosteroids and localized to the face, eyelids, and skin folds of patients >2 years, is reasonable to include in common practice. Despite the FDA’s Black Box warning, to date no evidence has been published linking the TCIs to an increased incidence of malignancy in either children or adults that establishes causation. The Canadian Society of Allergy and Clinical Immunology (CSACI) therefore recognizes that the benefits of TCIs should be carefully weighed with the theoretical risks in advising patients, and acknowledges that long-term studies remain in progress. The safety and efficacy of topical tacrolimus and pimecrolimus should therefore be considered when treating children and adults with AD in Canadian allergy and immunology practices.

Severe everolimus-induced steatohepatis: a case report

The mammalian target of rapamycin inhibitors are normally favored as immunosuppressant agents for solid organ transplantation such as kidney, liver or heart. Only in recent years have they been increasingly administered for the treatment of neuroendocrine tumors. Even though mammalian target of rapamycin inhibitors are known to exhibit specific side effects, everolimus-related severe hepatic steatosis has not as yet been described in the literature. We report the case of a 76-year-old man who developed severe hepatic steatosis within four weeks of treatment with everolimus as concomitant tumor therapy for a progressively growing neuroendocrine carcinoma of the ileum. A diagnosis of hepatic steatosis was established using computer tomography and fibroscan^©. Other underlying causes for steatosis hepatis could be excluded. Further studies are warranted to explain the underlying mechanisms.