Azathioprine and UVA light generate mutagenic oxidative DNA damage

Incidence of Cancer in ANCA-Associated Vasculitis: A Meta-Analysis of Observational Studies

Objective

The purpose of this paper is to examine cancer incidence in patients with ANCA-associated vasculitis (AASV) derived from population-based cohort studies by means of meta-analysis.

Methods

Relevant electronic databases were searched for studies characterizing the associated risk of overall malignancy in patients with AASV. Standardized incidence rates (SIRs) with 95% confidence intervals (CIs) were used to evaluate the strength of association. We tested for publication bias and heterogeneity and stratified for site-specific cancers.

Results

Six studies (n = 2,578) were eventually identified, of which six provided the SIR for overall malignancy, five reported the SIR for non-melanoma skin cancer (NMSC), four for leukemia, five for bladder cancer, three for lymphoma, three for liver cancer, four for lung cancer, three for kidney cancer, four for prostate cancer, four for colon cancer and four for breast cancer. Overall, the pooled SIR of cancer in AASV patients was 1.74 (95%CI = 1.37–2.21), with moderate heterogeneity among these studies (I² = 65.8%, P = 0.012). In sub-analyses for site-specific cancers, NMSC, leukemia and bladder cancer were more frequently observed in patients with AASV with SIR of 5.18 (95%CI = 3.47–7.73), 4.89 (95%CI = 2.93–8.16) and 3.84 (95%CI = 2.72–5.42) respectively. There was no significant increase in the risk of kidney cancer (SIR = 2.12, 95%CI = 0.66–6.85), prostate cancer (SIR = 1.45, 95%CI = 0.87–2.42), colon cancer (SIR = 1.26, 95%CI = 0.70–2.27), and breast cancer (SIR = 0.95, 95%CI = 0.50–1.79). Among these site-specific cancers, only NMSC showed moderate heterogeneity (I² = 55.8%, P = 0.06). No publication bias was found by using the Begg’s test and Egger's test.

Conclusions

This meta-analysis shows that AASV patients treatment with cyclophosphamide (CYC) are at increased risk of late-occurring malignancies, particularly of the NMSC, leukemia and bladder cancer. However, there is no significant association between AASV and kidney cancer, prostate cancer, colon cancer and breast cancer. These findings emphasize monitoring and preventative management in AASV patients after cessation of CYC therapy is momentous.

Incidence, risk factors and outcome of de novo tumors in liver transplant recipients focusing on alcoholic cirrhosis

Orthotopic liver transplantation (OLT) is an established life-saving procedure for alcoholic cirrhotic (AC) patients, but the incidence of de novo tumors ranges between 2.6% and 15.7% and is significantly increased in comparison with patients who undergo OLT for other etiologies. Tobacco, a known carcinogen, has been reported to be between 52% and 83.3% in AC patients before OLT. Other risk factors that contribute to the development of malignancies are dose-dependent immunosuppression, advanced age, viral infections, sun exposure, and premalignant lesions (inflammatory bowel disease, Barrett’s esophagus). A significantly more frequent incidence of upper aerodigestive (UAD) tract, lung, skin, and kidney-bladder tumors has been found in OLT recipients for AC in comparison with other etiologies. Liver transplant recipients who develop de novo non-skin tumors have a decreased long-term survival rate compared with controls. This significantly lower survival rate is more evident in AC recipients who develop UAD tract or lung tumors after OLT mainly because the diagnosis is usually performed at an advanced stage. All transplant candidates, especially AC patients, should be encouraged to cease smoking and alcohol consumption in the pre- and post-OLT periods, use skin protection, avoid sun exposure and over-immunosuppression, and have a yearly otopharyngolaryngeal exploration and chest computed tomography scan in order to prevent or reduce the incidence of de novo malignancies. Although still under investigation, substitution of calcineurin inhibitors for sirolimus or everolimus may reduce the incidence of de novo tumors after OLT.

MUTYH mediates the toxicity of combined DNA 6-thioguanine and UVA radiation

The therapeutic thiopurines, including the immunosuppressant azathioprine (Aza) cause the accumulation of the UVA photosensitizer 6-thioguanine (6-TG) in the DNA of the patients' cells. DNA 6-TG and UVA are synergistically cytotoxic and their interaction causes oxidative damage. The MUTYH DNA glycosylase participates in the base excision repair of oxidized DNA bases. Using Mutyh-nullmouse fibroblasts (MEFs) we examined whether MUTYH provides protection against the lethal effects of combined DNA 6-TG/UVA. Surprisingly, Mutyh-null MEFs were more resistant than wild-type MEFs, despite accumulating higher levels of DNA 8-oxo-7,8-dihydroguanine (8-oxoG).Their enhanced 6-TG/UVA resistance reflected the absence of the MUTYH protein and MEFs expressing enzymatically-dead human variants were as sensitive as wild-type cells. Consistent with their enhanced resistance, Mutyh-null cells sustained fewer DNA strand breaks and lower levels of chromosomal damage after 6-TG/UVA. Although 6-TG/UVA treatment caused early checkpoint activation irrespective of the MUTYH status, Mutyh-null cells failed to arrest in S-phase at late time points. MUTYH-dependent toxicity was also apparent in vivo. Mutyh-/- mice survived better than wild-type during a 12-month chronicexposure to Aza/UVA treatments that significantly increased levels of skin DNA 8-oxoG. Two squamous cell skin carcinomas arose in Aza/UVA treated Mutyh-/- mice whereas similarly treated wild-type animals remained tumor-free.

Skin changes following organ transplantation: an interdisciplinary challenge

BACKGROUND

The immunosuppressants used in transplantation medicine significantly elevate the incidence of neoplasia, particularly in the skin. The cumulative incidence of non-melanocytic skin cancer (NMSC) in renal transplant recipients was 20.5% in a study carried out in German centers. Data on more than 35 000 renal transplant recipients in the USA document a cumulative NMSC incidence of over 7% after 3 years of immunosuppression.

METHOD

The authors selectively review publications obtained by a PubMed search to discuss the incidence of, and major risk factors for, skin tumors and infectious diseases of the skin in immunosuppressed patients.

RESULTS

The main risk factors for skin tumors are age at the time of transplantation, light skin color, previous and present exposure to sunlight, and the type and duration of immunosuppressive treatment. Squamous-cell carcinoma (SCC) is the most common kind of skin tumor in immunosuppressed patients. Human herpesvirus 8 and Merkel-cell polyoma virus also cause neoplasia more often in immunosuppressed patients than in the general population. Surgical excision is the treatment of choice. Actinic keratosis markedly elevates the risk that SCC will arise in the same skin area (odds ratio 18.36, 95% confidence interval 3.03-111). Patients with multiple actinic keratoses can be treated with photodynamic therapy or with acitretin. To lower the skin cancer risk, organ transplant recipients should apply medical screening agents with a sun protection factor of at least 50 to exposed skin areas every day. 55% to 97% of organ transplant recipients have skin infections; these are treated according to their respective types.

CONCLUSION

Squamous-cell carcinoma of the skin adds to the morbidity and mortality of transplant recipients and is therefore among the major oncological challenges in this patient group. Structured concepts for interdisciplinary care enable risk-adapted treatment.

Nrf2 Activation Protects against Solar-Simulated Ultraviolet Radiation in Mice and Humans

The transcription factor Nrf2 determines the ability to adapt and survive under conditions of electrophilic, oxidative, and inflammatory stress by regulating the expression of elaborate networks comprising nearly 500 genes encoding proteins with versatile cytoprotective functions. In mice, disruption of Nrf2 increases susceptibility to carcinogens and accelerates disease pathogenesis. Paradoxically, Nrf2 is upregulated in established human tumors, but whether this upregulation drives carcinogenesis is not known. Here we show that the incidence, multiplicity, and burden of solar-simulated UV radiation-mediated cutaneous tumors that form in SKH-1 hairless mice in which Nrf2 is genetically constitutively activated are lower than those that arise in their wild-type counterparts. Pharmacologic Nrf2 activation by topical biweekly applications of small (40 nmol) quantities of the potent bis(cyano enone) inducer TBE-31 has a similar protective effect against solar-simulated UV radiation in animals receiving long-term treatment with the immunosuppressive agent azathioprine. Genetic or pharmacologic Nrf2 activation lowers the expression of the pro-inflammatory factors IL6 and IL1β, and COX2 after acute exposure of mice to UV radiation. In healthy human subjects, topical applications of extracts delivering the Nrf2 activator sulforaphane reduced the degree of solar-simulated UV radiation-induced skin erythema, a quantifiable surrogate endpoint for cutaneous damage and skin cancer risk. Collectively, these data show that Nrf2 is not a driver for tumorigenesis even upon exposure to a very potent and complete carcinogen and strongly suggest that the frequent activation of Nrf2 in established human tumors is a marker of metabolic adaptation.

Glutathione transferases in the bioactivation of azathioprine

The prodrug azathioprine is primarily used for maintaining remission in inflammatory bowel disease, but approximately 30% of the patients suffer adverse side effects. The prodrug is activated by glutathione conjugation and release of 6-mercaptopurine, a reaction most efficiently catalyzed by glutathione transferase (GST) A2-2. Among five genotypes of GST A2-2, the variant A2*E has threefold-fourfold higher catalytic efficiency with azathioprine, suggesting that the expression of A2*E could boost 6-mercaptopurine release and adverse side effects in treated patients. Structure-activity studies of the GST A2-2 variants and homologous alpha class GSTs were made to delineate the determinants of high catalytic efficiency compared to other alpha class GSTs. Engineered chimeras identified GST peptide segments of importance, and replacing the corresponding regions in low-activity GSTs by these short segments produced chimeras with higher azathioprine activity. By contrast, H-site mutagenesis led to decreased azathioprine activity when active-site positions 208 and 213 in these favored segments were mutagenized. Alternative substitutions indicated that hydrophobic residues were favored. A pertinent question is whether variant A2*E represents the highest azathioprine activity achievable within the GST structural framework. This issue was addressed by mutagenesis of H-site residues assumed to interact with the substrate based on molecular modeling. The mutants with notably enhanced activities had small or polar residues in the mutated positions. The most active mutant L107G/L108D/F222H displayed a 70-fold enhanced catalytic efficiency with azathioprine. The determination of its structure by X-ray crystallography showed an expanded H-site, suggesting improved accommodation of the transition state for catalysis.

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.

Generation of reactive oxygen species by lethal attacks from competing microbes

Whether antibiotics induce the production of reactive oxygen species (ROS) that contribute to cell death is an important yet controversial topic. Here, we report that lethal attacks from bacterial and viral species also result in ROS production in target cells. Using soxS as an ROS reporter, we found soxS was highly induced in Escherichia coli exposed to various forms of attacks mediated by the type VI secretion system (T6SS), P1vir phage, and polymyxin B. Using a fluorescence ROS probe, we found enhanced ROS levels correlate with induced soxS in E. coli expressing a toxic T6SS antibacterial effector and in E. coli treated with P1vir phage or polymyxin B. We conclude that both contact-dependent and contact-independent interactions with aggressive competing bacterial species and viruses can induce production of ROS in E. coli target cells.

Does a personal or family history of malignancy preclude the use of immunomodulators and biologics in IBD

The medical treatment for inflammatory bowel disease (IBD) has improved over the past 20 years. Although the routine use of immunomodulators and biologic agents in the treatment of IBD in the modern era has been a great achievement, these medicines are associated with rare but serious adverse events. In addition to the infectious complications, there are data to suggest that some of these agents are associated with higher rates of malignancy. In a patient with a history of cancer, or a family history of cancer, the gastroenterologist must be prepared to answer questions about the oncogenic potential of these agents. Thiopurines have been associated with a small increased risk of lymphoma in patients with IBD. In addition, an association with skin cancer has been established. Methotrexate is generally considered safe in patients with a history of cancer. There may be a small risk of lymphoma and possibly skin cancer with anti-tumor necrosis factor agents, but determining the cancer risk of these medications is difficult as they are often used in combination with thiopurines. In general, a family history of cancer should not influence a patient's medical regimen. Treatment for a patient with a personal history of cancer must be individualized and take into account the type and stage of cancer, time since completion of therapy, and the opinion of an oncologist.

Surveillance of nonmelanoma skin cancer incidence rates in kidney transplant recipients in Ireland

BACKGROUND

The incidence of nonmelanomatous skin cancer (NMSC) is substantially higher among renal transplant recipients (RTRs) than in the general population. With a growing RTR population, a robust method for monitoring skin cancer rates in this population is required.

METHODS

A modeling approach was used to estimate the trends in NMSC rates that adjusted for changes in the RTR population (sex and age), calendar time, the duration of posttransplant follow-up, and background population NMSC incidence rates. RTR databases in both Northern Ireland (NI) and the Republic of Ireland (ROI) were linked to their respective cancer registries for diagnosis of NMSC, mainly squamous cell carcinoma (SCC) and basal cell carcinoma (BCC).

RESULTS

RTRs in the ROI had three times the incidence (P<0.001) of NMSC compared with NI. There was a decline (P<0.001) in NMSC 10-year cumulative incidence rate in RTRs over the period 1994-2009, which was driven by reductions in both SCC and BCC incidence rates. Nevertheless, there was an increase in the incidence of NMSC with time since transplantation. The observed graft survival was higher in ROI than NI (P<0.05) from 1994-2004. The overall patient survival of RTRs was similar in NI and ROI.

CONCLUSION

Appropriate modeling of incidence trends in NMSC among RTRs is a valuable surveillance exercise for assessing the impact of change in clinical practices over time on the incidence rates of skin cancer in RTRs. It can form the basis of further research into unexplained regional variations in NMSC incidence.

Skin cancer in solid organ transplant recipients: are mTOR inhibitors a game changer?

While immunosuppressive agents are necessary to prevent the rejection of transplanted organs, and are a great medical success story for protecting against early allograft loss, graft and patient survival over the long term are diminished by side effects from these same drugs. One striking long-term side effect is a high rate of skin cancer development. The skin cancers that develop in transplant recipients tend to be numerous, as well as particularly aggressive, and are therefore a major contributor to morbidity and mortality in transplant recipients. An apparent reason for the high incidence of skin cancer likely relates to suppression of immune surveillance mechanisms, but other more direct effects of certain immunosuppressive drugs are also bound to contribute to cancers of UV-exposed skin. However, over the past few years, evidence has emerged to suggest that one class of immunosuppressants, mammalian target of rapamycin (mTOR) inhibitors, could potentially inhibit skin tumour formation through a number of mechanisms that are still being studied intensively today. Therefore, in light of the high skin cancer incidence in transplant recipients, it follows that clinical trials have been conducted to determine if mTOR inhibitors can significantly reduce these post-transplant skin malignancies. Here, the problem of post-transplant skin cancer will be briefly reviewed, along with the possible mechanisms contributing to this problem, followed by an overview of the relevant clinical trial results using mTOR inhibitors.

Risk of merkel cell carcinoma after solid organ transplantation

BACKGROUND

Solid organ transplant recipients have elevated risks of virus-related cancers, in part because of long-term immunosuppression. Merkel cell carcinoma (MCC) is an aggressive skin cancer recently found to have a viral origin, but little is known regarding the occurrence of MCC after transplant.

METHODS

We linked the US Scientific Registry of Transplant Recipients with data from 15 population-based cancer registries to ascertain MCC occurrence among 189498 solid organ transplant recipients from 1987 to 2009. Risks for MCC following transplantation were compared with the general population using standardized incidence ratios, and Poisson regression was used to compare incidence rates according to key patient and transplant characteristics. All statistical tests were two-sided.

RESULTS

After solid organ transplantation, overall risk of MCC was increased 23.8-fold (95% confidence interval = 19.6 to 28.7, n = 110). Adjusted risks were highest among older recipients, increased with time since transplantation, and varied by organ type (all P ≤ .007). Azathioprine, cyclosporine, and mTOR inhibitors given for maintenance immunosuppression increased risk, and non-Hispanic white recipients on cyclosporine and azathioprine experienced increasing MCC risk with lower latitude of residence (ie, higher ultraviolet radiation exposure, P = .012).

CONCLUSIONS

MCC risk is sharply elevated after solid organ transplant, likely resulting from long-term immunosuppression. Immunosuppressive medications may act synergistically with ultraviolet radiation to increase risk.

Use of azathioprine for graft-vs-host disease is the major risk for development of secondary malignancies after haematopoietic stem cell transplantation: a nationwide population-based study

BACKGROUND

As more patients are treated by haematopoietic stem cell transplantation (HSCT), development of secondary malignancy (SM) becomes an increasingly common issue in long-term survivors.

METHODS

We conducted a nationwide population-based study of the Taiwanese population to analyse patients who received HSCT between January 1997 and December 2010. Standardised incidence ratios (SIRs) were used to compare the risk of SM in HSCT patients and the general population. Multivariate analysis was performed to identify independent predictors of SM.

RESULTS

Patients receiving HSCT had a significantly greater risk of developing SM (SIR 2.00; 95% confidence interval (CI) 1.45-2.69; P<0.001). Specifically, the incidence increased for cancers of the oral cavity (SIR 14.18) and oesophagus (SIR 14.75) after allogeneic HSCT. Multivariate analysis revealed an increased SIR for cancer in patients who received the immunosuppressant azathioprine. The risk of SM also increased with greater cumulative doses of azathioprine.

CONCLUSIONS

This study demonstrates an increased incidence of SM in Taiwanese patients who received allogeneic HSCT, especially for cancers of the oral cavity and oesophagus. This finding is different from results in populations of Western countries. Physicians should be cautious about azathioprine use for graft-vs-host disease after HSCT.

Rose Bengal-photosensitized oxidation of 4-thiothymidine in aqueous medium: evidence for the reaction of the nucleoside with singlet state oxygen

Thymidine and a thiothymidine dimer are the products from the reaction of 4-thiothymidine with ¹O₂ generated through Rose Bengal-mediated photosensitization.

A practical guide to the use of thiopurines in oral medicine

Thiopurines are widely used as first-line immunosuppressive therapies in the management of chronic inflammatory oral disease. However, despite over half a century of clinical experience, the evidence base for their use is limited. The aims of this paper were to review the evidence for the use of thiopurines in oral medicine and provide a contemporary model of thiopurine metabolism and mechanism of action and a rationale for clinical use and safe practice.

Skin cancer evaluation in transplant patients: a physician opinion survey with recommendations

BACKGROUND

Non-melanoma skin cancer is the most common malignancy in transplant patients. However, routine skin cancer evaluation is currently not the standard of care.

OBJECTIVE

To investigate the current barriers among transplant physicians to skin cancer screening in their patients. To provide recommendations for appropriate routine skin surveillance.

METHODS

A web-based survey was conducted among Baylor, Dallas transplant physicians. Thirty-seven of 46 responses were received, and 13 physicians (28%) were classified as "high screeners."

RESULTS

The univariate analysis revealed three main barriers including the perception of difficulty in seeing a dermatologist (p = 0.017), skin cancer evaluation is not an important aspect of transplant care (p = 0.038), and thirdly, the belief that there is insufficient evidence to warrant universal skin cancer screening in transplant patients (p = 0.013). The fully adjusted multivariable analysis resulted in two significant conclusions; the most important predictor was the perceived lack of medical evidence for skin cancer screening.

LIMITATIONS

The small sample size and all responses being from the same institution in Texas.

CONCLUSION

The dermatologic evidence for regular skin cancer screening in transplant patients needs dissemination to our transplant colleagues. This is a significant practice gap which can be appropriately closed by integrating dermatologists into the transplant team.

Previous cancer and/or lymphoma in patients with refractory IBD--con: anti-TNF or conventional immunosuppressive treatment

Patients with IBD and prior cancer are at increased risk of developing recurrent or de novo cancer. Depending on the type of malignancy, risk factors include IBD itself, age, environmental factors, genetic susceptibility and exposure to immunosuppressants (IMS), namely thiopurines, methotrexate and anti-TNFα biologics. The procarcinogenic effect of IMS depends on the type of drug and length of exposure. Thiopurines increase the rates of nonmelanoma skin cancer and lymphomas. Methotrexate is less harmful, but data are scarce. Evidence favoring the 'safety' of anti-TNF monotherapy is weak because most patients have been exposed to combinations of IMS prior to the development of malignancy. Anti-TNFα biologics may promote tumor proliferation and increase the risk of melanomas. Exclusion of these patients from trials with biologics, physician concerns or fear of incident cancers and medicolegal consequences, and patient concerns have led to a paucity of data regarding IMS treatment of patients with a prior malignancy. In the absence of guidelines, IMS should be avoided especially during the first 2 years after commencing cancer therapy. Depending on disease type, location and severity, 5-ASA, antibiotics, enteric nutrition, steroids alone or in combinations, seton placement, and 'curative' or 'diverting' surgery may allow for a crucial drug-holiday period before readministration of IMS. Preventive measures include smoking cessation, UV solar protection, annual skin examination and Pap test. If unavoidable, methotrexate should be the drug of first choice followed by anti-TNFα and then thiopurines. Patients should be managed on a case-by-case basis by a multidisciplinary team of experts.

Clinical lessons to be learned from patients developing chronic myeloid leukemia while on immunosuppressive therapy after solid organ transplantation: yet another case after orthotopic heart transplantation

Chronic myeloid leukemia developing after transplantation of solid organs and concomitant immunosuppression is a rare but still significant clinical phenomenon. We here describe an additional case of a 62-year-old male patient developing CML after orthotopic heart transplantation and medication with cyclosporine A, mofetil-mycophenolate, and steroids. Initial antileukemic therapy was imatinib at a standard dose and within 15 months of therapy a complete cytogenetic response was noted. In this report we discuss the clinical implications of these rare but biologically important cases.

DNA repair inhibition by UVA photoactivated fluoroquinolones and vemurafenib

Cutaneous photosensitization is a common side effect of drug treatment and can be associated with an increased skin cancer risk. The immunosuppressant azathioprine, the fluoroquinolone antibiotics and vemurafenib—a BRAF inhibitor used to treat metastatic melanoma—are all recognized clinical photosensitizers. We have compared the effects of UVA radiation on cultured human cells treated with 6-thioguanine (6-TG, a DNA-embedded azathioprine surrogate), the fluoroquinolones ciprofloxacin and ofloxacin and vemurafenib. Despite widely different structures and modes of action, each of these drugs potentiated UVA cytotoxicity. UVA photoactivation of 6-TG, ciprofloxacin and ofloxacin was associated with the generation of singlet oxygen that caused extensive protein oxidation. In particular, these treatments were associated with damage to DNA repair proteins that reduced the efficiency of nucleotide excision repair. Although vemurafenib was also highly phototoxic to cultured cells, its effects were less dependent on singlet oxygen. Highly toxic combinations of vemurafenib and UVA caused little protein carbonylation but were nevertheless inhibitory to nucleotide excision repair. Thus, for three different classes of drugs, photosensitization by at least two distinct mechanisms is associated with reduced protection against potentially mutagenic and carcinogenic DNA damage.

Risk of melanoma and non-melanoma skin cancer in ulcerative colitis patients treated with thiopurines: a nationwide retrospective cohort

OBJECTIVES

There are limited data on the risk of non-melanoma skin cancer (NMSC) and melanoma skin cancer (MSC) among thiopurine-treated patients with ulcerative colitis (UC). Our aim was to investigate the risk while on, by cumulative years, and after stopping thiopurine therapy.

METHODS

Nationwide data were obtained from the Veterans Affairs (VA) health-care system during 2001-2011. We performed a retrospective cohort study evaluating patients with UC. Cox regression was used to investigate the association between thiopurines use and time to NMSC while adjusting for demographics, ultraviolet radiation exposure, and VA visiting frequency. A matched nested case-control study was conducted to investigate the association between thiopurine use and MSC.

RESULTS

We included 14,527 patients with UC in the analysis, with a median follow-up of 8.1 years. A total of 3,346 (23%) patients used thiopurines for a median duration of 1.6 years. We identified 421 NMSC and 45 MSC cases. The adjusted hazard ratios of developing NMSC while on and after stopping thiopurines were 2.1 (P<0.0001) and 0.7 (P=0.07), respectively, as compared with unexposed patients. The incidence rate of NMSC among those who never used thiopurines was 3.7 compared with 5.8, 7.9, 8.3, 7.8, and 13.6 per 1,000 person-years for the 1st, 2nd, 3th, 4th, and 5th year of thiopurine use, respectively. No statistically significant association was observed between thiopurine use and MSC, odds ratio 0.8 (P=0.6).

CONCLUSIONS

In this predominantly white male nationwide cohort, there was a twofold increase in the risk of NMSC while on thiopurines. The incidence rate of NMSC significantly increased with subsequent years of cumulative exposure to thiopurines. Stopping thiopurines reduced the risk of NMSC to pre-exposure levels irrespective of the prior exposure duration.

Communication: the dark singlet state as a doorway state in the ultrafast and efficient intersystem crossing dynamics in 2-thiothymine and 2-thiouracil

Femtosecond broadband transient absorption experiments are reported for 2-thiothymine and 2-thiouracil in aqueous buffer solution and in acetonitrile. It is shown that the S1(nπ*) state acts as a doorway state in the ultrafast and efficient population of the T1(ππ*) state upon 316 nm excitation. A sequential kinetic model is presented to explain the excited-state dynamics in 2-thiothymine and 2-thiouracil upon UVA excitation: S2(ππ*) → S1(nπ*) → T1(ππ*). The experimental results are also used to scrutinize the excited-state relaxation pathways recently predicted for 2-thiouracil at the CASPT2//CASSCF level of theory [G. Cui and W. Fang, J. Chem. Phys. 138, 044315 (2013)]. The efficient population of the T1(ππ*) state for both 2-thiothymine and 2-thiouracil in a few hundreds of femtoseconds lends further support to the emerging idea that thiobase derivatives exhibit photo-toxic properties that can be effectively harnessed in photo-chemotherapeutic applications.

Risk of new or recurrent cancer under immunosuppressive therapy in patients with IBD and previous cancer

OBJECTIVE

To explore the risk of new or recurrent cancer among patients with IBD and previous cancer, exposed or not to immunosuppressants.

DESIGN

Among the 17 047 patients of the CESAME prospective observational cohort who were enrolled from May 2004 to June 2005, and followed-up until December 2007, we identified 405 patients with cancer diagnosed previous to study entry. We calculated the rates of incident cancer in patients with or without previous cancer, and we assessed by survival analysis and nested case-control study the impact of immunosuppressants on the risk of incident new or recurrent cancer in patients with previous cancer.

RESULTS

The rate of incident cancer was 21.1/1000 patient-years (PY) and 6.1/1000 PY in patients with and without previous cancer, respectively. The multivariate-adjusted HR of incident cancer between patients with and without previous cancer was 1.9 (95% CI 1.2 to 3.0, p=0.003). Among patients with previous cancer, the rates of new and recurrent cancers were, respectively, 13.2/1000 PY and 6.0/1000 PY in the 312 patients who were not taking immunosuppressant at the time of study entry, and 23.1/1000 PY and 3.9/1000 PY in the 93 patients treated with immunosuppressants at study entry. There was no significant association between the exposure to immunosuppressants and the risk of new or recurrent cancer.

CONCLUSIONS

Patients with IBD with a history of cancer are at increased risk of developing any (new or recurrent) cancer, with a predominant incidence of new cancers. Treatment with immunosuppressants has no overall major impact per se on this risk.

Optimal management of skin cancer in immunosuppressed patients

Skin cancer is the most common malignancy in humans with basal cell carcinoma representing the majority of cases in the general population. The prevalence of skin cancer is increased amongst immunosuppressed patients such as those with lymphoproliferative disorders including non-Hodgkin lymphoma and chronic lymphocytic leukemia or those with iatrogenic immunosuppression following organ transplantation. In addition, these patients experience greater morbidity and mortality associated with skin cancers. The most common skin cancer in immunosuppressed patients is squamous cell carcinoma, which often presents with more aggressive features and has a greater rate of metastasis. This article reviews the risk factors, etiology, clinical presentation, and prevalence of skin cancer amongst immunosuppressed patients, including organ transplant, lymphoproliferative disorders, autoimmune disorders, and human immunodeficiency virus. We also provide a comprehensive review of treatment guidelines for immunosuppressed patients with cutaneous malignancy. Surgical therapy is the cornerstone of treatment; however, we also discuss pharmacologic treatment options, lifestyle modifications, and revision of immunosuppressive regimens.

Harmful effects of the azathioprine metabolite 6-mercaptopurine in vascular cells: induction of mineralization

Vascular mineralization contributes to the high cardiovascular morbidity and mortality in patients who suffer from chronic kidney disease and in individuals who have undergone solid organ transplantation. The immunosuppressive regimen used to treat these patients appears to have an impact on vascular alterations. The effect of 6-mercaptopurine (6-MP) on vascular calcification has not yet been determined. This study investigates the effect of 6-MP on vascular mineralization by the induction of trans-differentiation of rat vascular smooth muscle cells in vitro. 6-MP not only induces the expression of osteo-chondrocyte-like transcription factors and proteins but also activates alkaline phosphatase enzyme activity and produces calcium deposition in in vitro and ex vivo models. These processes are dependent on 6-MP-induced production of reactive oxygen species, intracellular activation of mitogen-activated kinases and phosphorylation of the transcription factor Cbfa1. Furthermore, the metabolic products of 6-MP, 6-thioguanine nucleotides and 6-methyl-thio-inosine monophosphate have major impacts on cellular calcification. These data provide evidence for a possible harmful effect of the immunosuppressive drug 6-MP in vascular diseases, such as arteriosclerosis.

Non-melanoma skin cancer is reduced after switch of immunosuppression to mTOR-inhibitors in organ transplant recipients

BACKGROUND

Organ transplant recipients are prone to the development of non-melanoma skin cancer. Organ transplant recipients often develop multiple non-melanoma skin cancers and the tumors show an aggressive growth pattern, therefore surgical therapy can be difficult. Switch of the immunosuppressive regimen to mTOR-inhibitors such as everolimus or sirolimus can have an antitumor effect.

PATIENTS AND METHODS

In a monocentric retrospective study we evaluated organ transplant recipients who presented with non-melanoma skin cancer in the years 2008-2010. Experience with patients who were switched to an mTOR-inhibitor due to non-melanoma skin cancer are reported in detail, and recent clinical studies are reviewed.

RESULTS

60 organ transplant recipients with non-melanoma skin cancer were evaluated. Due to the development of multiple non-melanoma skin cancer within a few years, the immunosuppressive regimen was switched to everolimus in 7 patients and to sirolimus in 5 patients. Eight patients were evaluable for the effect of mTOR-inhibitors on the development of non-melanoma skin cancer; 4 patients had to discontinue the medication with mTOR-inhibitors early due to various side effects. In the year before the switch to mTOR-inhibitors, 8 patients developed 16 squamous cell carcinomas, 3 Basal cell carcinomas and 22 cases of Bowen's disease. All tumors were histologically confirmed. In the year after switch of immunosuppression, the rate of squamous cell carcinomas (n = 2) and Bowen's disease (n = 3), but not of basal cell carcinomas (n = 2) was significantly reduced. Moreover, 5 prospective randomized trials recently have demonstrated a reduced number of non-melanoma skin cancers in organ transplant recipients after switch of the immunosuppressive regimen to mTOR-inhibitors.

CONCLUSION

Switch of the immunosuppressive regimen to mTOR-inhibitors should be considered for organ transplant recipients suffering from multiple non-melanoma skin cancers.

Use of thiopurines in inflammatory bowel disease: Safety issues

Thiopurines are widely used for maintenance treatment of inflammatory bowel disease. Inter-individual variability in clinical response to thiopurines may be attributed to several factors including genetic polymorphisms, severity and chronicity of disease, comorbidities, duration of administration, compliance issues and use of concomitant medication, environmental factors and clinician and patient preferences. The purpose of this review is to summarise the current evidence on thiopurine safety and toxicity, to describe adverse drug events and emphasise the significance of drug interactions, and to discuss the relative safety of thiopurine use in adults, elderly patients, children and pregnant women. Thiopurines are safe to use and well tolerated, however dose adjustment or discontinuation of treatment must be considered in cases of non-response, poor compliance or toxicity. Drug safety, clinical response to treatment and short to long term risks and benefits must be balanced throughout treatment duration for different categories of patients. Treatment should be individualised and stratified according to patient requirements. Enzymatic testing prior to treatment commencement is advised. Surveillance with regular clinic follow-up and monitoring of laboratory markers is important. Data on long term efficacy, safety of thiopurine use and interaction with other disease modifying drugs are lacking, especially in paediatric inflammatory bowel disease. High quality, collaborative clinical research is required so as to inform clinical practice in the future.

Protein oxidation and DNA repair inhibition by 6-thioguanine and UVA radiation

Damage to skin DNA by solar UV is largely unavoidable, and an optimal cellular response to it requires the coordinated operation of proteins in numerous pathways. A fully functional DNA repair proteome for removing harmful DNA lesions is a prerequisite for an appropriate DNA damage response. Genetically determined failure to repair UV-induced DNA damage is associated with skin photosensitivity and increased skin cancer risk. Patients treated with immunosuppressant/anti-inflammatory thiopurines are also photosensitive and have high rates of sun-related skin cancer. Their DNA contains the base analog 6-thioguanine (6-TG), which acts as a UVA photosensitizer to generate reactive oxygen species (ROS), predominantly singlet oxygen ((1)O2). ROS damage both DNA and proteins. Here we show that UVA irradiation of cultured human cells containing DNA 6-TG causes significant protein oxidation and damages components of the DNA repair proteome, including the Ku, OGG-1, MYH, and RPA proteins. Assays of DNA repair in intact cells or in cell extracts indicate that this protein damage compromises DNA break rejoining and base and nucleotide excision repair. As these experimental conditions simulate those in the skin of patients taking thiopurines, our findings suggest a mechanism whereby UVA in sunlight may contribute to skin carcinogenesis in immunosuppressed patients.

Risk of malignancies in patients with inflammatory bowel disease treated with thiopurines or anti-TNF alpha antibodies

PURPOSE

We aimed to analyse malignancy rates and predictors for the development of malignancies in a large German inflammatory bowel disease (IBD) cohort treated with thiopurines and/or anti-tumour necrosis factor (TNF) antibodies.

METHODS

De novo malignancies in 666 thiopurine-treated and/or anti-TNF-treated IBD patients were analysed. Patients (n = 262) were treated with thiopurines alone and never exposed to anti-TNF antibodies (TP group). In addition, patients (n = 404) were exposed to anti-TNF antibodies (TNF+ group) with no (7.4%), discontinued (80.4%) or continued (12.1%) thiopurine therapy.

RESULTS

In the TP group, 20 malignancies were observed in 18 patients compared with 8 malignancies in 7 patients in the TNF+ group (hazard ratio 4.15; 95% CI 1.82-9.44; p = 0.0007; univariate Cox regression). Moreover, 18.2% of all patients in the TP group ≥50 years of age developed a malignancy, compared with 3.8% of all patients <50 years of age (p = 0.0008). In the TNF+ group, 6.5% of all patients ≥50 years of age developed malignancies compared with 0.3% of all patients <50 years of age (p = 0.0007). In both groups combined, thiopurine treatment duration ≥4 years was associated with the risk for skin cancer (p = 0.0024) and lymphoma (p = 0.0005).

CONCLUSIONS

Our data demonstrate an increased risk for the development of malignancies in IBD patients treated with thiopurines in comparison with patients treated with anti-TNF antibodies with or without thiopurines.

A dual-fluorescent reporter facilitates identification of thiol compounds that suppress microsatellite instability induced by oxidative stress

The DNA mismatch-repair (MMR) system corrects replicative errors and minimizes mutations that occur at a high rate in microsatellites. Patients with chronic inflammation or inflammation-associated cancer display microsatellite instability (MSI), indicating a possible MMR inactivation. In fact, H2O2-generated oxidative stress inactivates the MMR function and increases mutation accumulation in a reporter microsatellite. However, it remains unclear whether MSI induced by oxidative stress is preventable because of the lack of a sufficiently sensitive detection assay. Here, we developed and characterized a dual-fluorescent system, utilizing DsRed harboring the (CA)13 microsatellite as a reporter and GFP for normalization, in near-isogenic human colorectal cancer cell lines. Via flow cytometry, this reporter sensitively detected H2O2-generated oxidative microsatellite mutations in a dose-dependent manner. The reporter further revealed that glutathione or N-acetylcysteine was better than aspirin and ascorbic acid for suppressing oxidative microsatellite mutations. These two thiol compounds also partially suppressed oxidative frameshift mutations in the coding microsatellites of the hMSH6 and CHK1 genes based on a fluoresceinated PCR-based assay. MSI suppression by N-acetylcysteine appears to be mediated through reduction of oxidative frameshift mutations in the coding microsatellite of hMSH6 and protection of hMSH6 and other MMR protein levels from being decreased by H2O2. Our findings suggest a linkage between oxidative damage, MMR deficiency, and MSI. The two thiol compounds are potentially valuable for preventing inflammation-associated MSI. The dual-fluorescent reporter with improved features will facilitate identification of additional compounds that modulate MSI, which is relevant to cancer initiation and progression.

The oncogene ATF3 is potentiated by cyclosporine A and ultraviolet light A

Cutaneous squamous cell carcinoma (SCC) represents the most important cutaneous complication following organ transplantation. It develops mostly on sun-exposed areas. A recent study showed the role of activating transcription factor 3 (ATF3) in SCC development following treatment with calcineurin inhibitors. It has been reported that ATF3, which may act as an oncogene, is under negative calcineurin/nuclear factor of activated T cells (NFAT) control and is upregulated by calcineurin inhibitors. Still, these findings do not fully explain the preferential appearance of SCC on chronically sun-damaged skin. We analyzed the influence of UV radiation on ATF3 expression and its potential role in SCC development. We found that ATF3 is a specifically induced AP1 member in SCC of transplanted patients. Its expression was strongly potentiated by combination of cyclosporine A and UVA treatment. UVA induced ATF3 expression through reactive oxygen species-mediated nuclear factor erythroid 2-related factor 2 (NRF2) activation independently of calcineurin/NFAT inhibition. Activated NRF2 directly binds to ATF3 promoter, thus inducing its expression. These results demonstrate two mechanisms that independently induce and, when combined together, potentiate the expression of ATF3, which may then force SCC development. Taking into account the previously defined role of ATF3 in the SCC development, these findings may provide an explanation and a mechanism for the frequently observed burden on SCCs on sun-exposed areas of the skin in organ transplant recipients treated by calcineurin inhibitors.

Patients with systemic sclerosis present increased DNA damage differentially associated with DNA repair gene polymorphisms

OBJECTIVE

Patients with systemic sclerosis (SSc) exhibit increased toxicity when exposed to genotoxic agents. In our study, we evaluated DNA damage and polymorphic sites in 2 DNA repair genes (XRCC1 Arg399Gln and XRCC4 Ile401Thr) in patients with SSc.

METHODS

A total of 177 patients were studied for DNA repair gene polymorphisms. Fifty-six of them were also evaluated for DNA damage in peripheral blood cells using the comet assay.

RESULTS

Compared to controls, the patients as a whole or stratified into major clinical variants (limited or diffuse skin involvement), irrespective of the underlying treatment schedule, exhibited increased DNA damage. XRCC1 (rs: 25487) and XRCC4 (rs: 28360135) allele and genotype frequencies observed in patients with SSc were not significantly different from those observed in controls; however, the XRCC1 Arg399Gln allele was associated with increased DNA damage only in healthy controls and the XRCC4 Ile401Thr allele was associated with increased DNA damage in both patients and controls. Further, the XRCC1 Arg399Gln allele was associated with the presence of antinuclear antibody and anticentromere antibody. No association was observed between these DNA repair gene polymorphic sites and clinical features of patients with SSc.

CONCLUSION

These results corroborate the presence of genomic instability in SSc peripheral blood cells, as evaluated by increased DNA damage, and show that polymorphic sites of the XRCC1 and XRCC4 DNA repair genes may differentially influence DNA damage and the development of autoantibodies.

Association between thiopurine use and nonmelanoma skin cancers in patients with inflammatory bowel disease: a meta-analysis

OBJECTIVES

Thiopurines are the mainstay of treatment for patients with inflammatory bowel disease (IBD). Thiopurine therapy increases the risk of nonmelanoma skin cancers (NMSCs) in organ transplant patients. The data on NMSC in patients with IBD on thiopurines is conflicting.

METHODS

We searched electronic databases for full journal articles reporting on the risk of developing NMSC in patients with IBD on thiopurine and hand searched the reference lists of all retrieved articles. Pooled adjusted hazard ratios and 95% confidence intervals (CIs) were determined using a random-effects model. Publication bias was assessed using Funnel plots and Egger's test. Heterogeneity was assessed using Cochran's Q and the I(2) statistic.

RESULTS

Eight studies involving 60,351 patients provided data on the risk of developing NMSC in patients with IBD on thiopurines. The pooled adjusted hazards ratio of developing NMSC after exposure to thiopurines in patients with IBD was 2.28 (95% CI: 1.50 to 3.45). There was significant heterogeneity (I(2)=76%) between the studies but no evidence of publication bias. Meta regression analysis suggested that the population studied (hospital-based vs. population-based) and duration of follow-up contributed significantly to heterogeneity. Grouping studies based on population studied and duration showed higher hazard rations in hospital-based and shorter duration studies.

CONCLUSIONS

The risk of developing NMSC in patients with IBD on thiopurines is only modestly elevated. The difference in pooled risk between population-based and hospital-based studies suggests the possibility that ascertainment bias could have contributed to this increased risk.

Immune-mediated inflammatory reactions and tumors as skin side effects of inflammatory bowel disease therapy

All drugs currently used for treating patients with inflammatory bowel disease (IBD - including Crohn's disease and ulcerative colitis) have the potential to induce skin lesions ranging from mild eruptions to more serious and widespread clinical presentations. The number of cutaneous adverse reactions due to IBD therapies is progressively increasing and the most frequently involved drugs are thiopurines and biologics like tumor necrosis factor (TNF)-α antagonists. The main drug-induced cutaneous manifestations are non-melanoma skin cancer (NMSC), notably basal cell and squamous cell carcinomas, and viral skin infections for thiopurines and psoriasiform, eczematoid and lichenoid eruptions as well as skin infections and cutaneous lupus erythematosus for biologics. Cutaneous manifestations should be promptly recognized and correctly diagnosed in order to quickly establish an adequate therapy. The main treatment for NMSC is surgical excision whereas the management of immune-mediated inflammatory skin reactions varies from topical therapy for mild presentations to the shift to another drug alone or in combination with corticosteroids for extensive eruptions.

[Phototherapy and carcinogenesis]

Phototherapy successfully uses the short-term effects of ultraviolet light against inflammation and proliferation. For its long-term effects, however, ultraviolet light was recently classified as a carcinogen. The wave spectrum employed in phototherapy has various carcinogenic effects in experimental systems, most notably DNA mutations in keratinocytes. Clinically, PUVA increases the risk for squamous cell carcinoma of the skin, especially after following 350 or more phototherapy sessions over a lifetime. Melanoma and genital skin cancer are not increased by PUVA alone. Previous UV damage, immunosuppression and other systemic treatments increase cutaneous carcinogenesis through PUVA. In contrast, broad-band UVB, narrow-band UVB and UVA1 have not yet been linked to cutaneous carcinogenesis, but will need careful follow-up in larger studies. Phototherapy remains a safe treatment modality, provided that the indication is well-founded, previous exposure and co-carcinogens are considered, and short and dose-intensive treatment protocols are favored, PUVA is chosen as second-line treatment that should not be used for more than a lifetime total of 250-300 phototherapy sessions.

Mitigating UVA light induced reactivity of 6-thioguanine through formation of a Ru(ii) half-sandwich complex

Half-sandwich ruthenium complexes of 6-thioguanine.