De novo malignancies after organ transplantation: focus on viral infections

Skin cancer in renal transplant recipients: outcomes from a safety net hospital in Boston

BACKGROUND

Renal transplant recipients (RTRs) are prone to skin cancer due to the immunosuppression required to maintain graft function. Existing studies of skin cancer in RTRs focus on patients with Fitzpatrick skin types I-II, with limited documentation of incidence in skin types III-VI. This study seeks to better characterize skin cancers in RTRs with skin types III-VI.

PRIMARY AIMS

Compare the incidence of skin cancer in RTRs of skin types I-II with skin types III-VI.

SECONDARY AIMS

Explore the association between the development of skin cancer and other contributing factors in RTRs of skin types I-VI.

METHODS

Retrospective chart review of RTRs at a single institution between January 1, 2000 and December 31, 2022. Patients were followed from the date of transplant to the last clinical follow-up or death. 777 RTRs were included in the study, including 245 patients with Fitzpatrick skin types I-II and 532 with skin types III-VI. A total of 48 patients developed NMSCs, 2 patients developed melanoma, and 3 patients developed Kaposi sarcoma.

RESULTS AND CONCLUSIONS

There is a higher incidence of skin cancer in RTRs with Fitzpatrick skin types III-VI compared to the reported incidence among non-transplant recipients of the same skin types, but the incidence remains considerably lower compared to RTR of skin types I-II.

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.

Adverse Drug Events after Kidney Transplantation

Introduction: Kidney transplantation stands out as the optimal treatment for patients with end-stage kidney disease, provided they meet specific criteria for a secure outcome. With the exception of identical twin donor-recipient pairs, lifelong immunosuppression becomes imperative. Unfortunately, immunosuppressant drugs, particularly calcineurin inhibitors like tacrolimus, bring about adverse effects, including nephrotoxicity, diabetes mellitus, hypertension, infections, malignancy, leukopenia, anemia, thrombocytopenia, mouth ulcers, dyslipidemia, and wound complications. Since achieving tolerance is not feasible, patients are compelled to adhere to lifelong immunosuppressive therapies, often involving calcineurin inhibitors, alongside mycophenolic acid or mTOR inhibitors, with or without steroids. Area covered: Notably, these drugs, especially calcineurin inhibitors, possess narrow therapeutic windows, resulting in numerous drug-related side effects. This review focuses on the prevalent immunosuppressive drug-related side effects encountered in kidney transplant recipients, namely nephrotoxicity, post-transplant diabetes mellitus, leukopenia, anemia, dyslipidemia, mouth ulcers, hypertension, and viral reactivations (cytomegalovirus and BK virus). Additionally, other post-kidney-transplantation drugs such as valganciclovir may also contribute to adverse events such as leukopenia. For each side effect, we propose preventive measures and outline appropriate treatment strategies.

Immunological considerations and challenges for regenerative cellular therapies

The central goal of regenerative medicine is to replace damaged or diseased tissue with cells that integrate and function optimally. The capacity of pluripotent stem cells to produce unlimited numbers of differentiated cells is of considerable therapeutic interest, with several clinical trials underway. However, the host immune response represents an important barrier to clinical translation. Here we describe the role of the host innate and adaptive immune responses as triggers of allogeneic graft rejection. We discuss how the immune response is determined by the cellular therapy. Additionally, we describe the range of available in vitro and in vivo experimental approaches to examine the immunogenicity of cellular therapies, and finally we review potential strategies to ameliorate immune rejection. In conclusion, we advocate establishment of platforms that bring together the multidisciplinary expertise and infrastructure necessary to comprehensively investigate the immunogenicity of cellular therapies to ensure their clinical safety and efficacy.

De Novo Cancer Incidence and Prognosis After Kidney Transplantation: A Single Center Analysis

BACKGROUND

Malignancy is an important cause of mortality in renal transplants recipients. The aim of this study was to evaluate the incidence, prognosis, and survival of patients developing a de novo post-transplant cancer.

METHODS

Using a retrospective cohort design, we evaluated the incidence of de novo cancers among kidney transplants patients in our hospital from January 2000 to December 2012. We also evaluated the patient survival after tumor diagnosis.

RESULTS

We included 535 kidney transplants recipients with a mean follow-up of 7.8 years; among them, 39 (7.2%) developed malignancies. Median time from transplant to cancer diagnosis was 3 years, with a median age at diagnosis of 60 years. Male patients were significantly older at time of cancer diagnosis (68.5 years) compared with women (38 years, P < .05), and cancer diagnosis occurred significantly earlier in men (3.5 years since transplantation) than in women (8.5 years, P < .05). Among 39 patients affected by a de novo post-transplant cancer, 18 patients (46.2%) died, with an average age at death of 58.5 years. The average time from cancer diagnosis to death was 1.5 years. Among the group of patients who did not develop a post-transplant cancer, 83 patients (16.7%) died, with a median age at time of death of 54.5 years (P < .05).

CONCLUSIONS

Kidney transplant recipients are at higher risk of developing a post-transplant cancer. Prognosis after cancer diagnosis is poor, probably as a consequence of a more aggressive behavior of cancer in transplant recipients. Intensive screening protocols could allow for an earlier diagnosis thereby improving the long-term outcome of these patients.

Cancer in kidney transplant recipients

Cancer is the second most common cause of mortality and morbidity in kidney transplant recipients after cardiovascular disease. Kidney transplant recipients have at least a twofold higher risk of developing or dying from cancer than the general population. The increased risk of de novo and recurrent cancer in transplant recipients is multifactorial and attributed to oncogenic viruses, immunosuppression and altered T cell immunity. Transplant candidates and potential donors should be screened for cancer as part of the assessment process. For potential recipients with a prior history of cancer, waiting periods of 2-5 years after remission - largely depending on the cancer type and stage of initial cancer diagnosis - are recommended. Post-transplantation cancer screening needs to be tailored to the individual patient, considering the cancer risk of the individual, comorbidities, overall prognosis and the screening preferences of the patient. In kidney transplant recipients diagnosed with cancer, treatment includes conventional approaches, such as radiotherapy and chemotherapy, together with consideration of altering immunosuppression. As the benefits of transplantation compared with dialysis in potential transplant candidates with a history of cancer have not been assessed, current clinical practice relies on evidence from observational studies and registry analyses.

Effects of psoriasis treatment on genital warts: a case report

The use of immunosuppressive drugs predisposes to infections, as they block the most important stage in antiviral defense, which is the cytotoxic T-lymphocyte HLA-dependent response. We report a case of extensive genital warts in a young woman on therapy for psoriasis with cyclosporine, afterwards successfully treated with an anti-tumor necrosis factor alpha (TNF-α) agent. Cyclosporine may predispose to the reactivation of latent infections and may favor the clinical manifestations of human papillomavirus (HPV)-related diseases, due to the inhibition of cell-mediated immunity that plays a crucial role in controlling HPV infections. In the literature the relationship between HPV and TNF-blockers has not yet been clearly defined. Our case underlines that the prompt interruption of cyclosporine can induce a complete regression of warts without any additional treatment and adds evidence to the possible use of anti-TNF-α in patients with psoriasis and genital warts.

Venous thromboembolism leading to diagnosis of de novo malignancy in an organ transplant recipient

We report the case of a patient with remote orthotopic liver transplant who was ultimately diagnosed with Merkel cell carcinoma following admission for initial venous thromboembolism. Additionally, we review pertinent literature related to the risk of skin cancer in solid organ transplant recipients and discuss the importance of yearly skin exams in this patient population.

Mortality risk after cancer diagnosis in kidney transplant recipients: the limitations of analyzing hospital administration data alone

Administrative data are frequently used for epidemiological studies but its usefulness to analyze cancer epidemiology after kidney transplantation is unclear. In this retrospective population-based cohort study, we identified every adult kidney-alone transplant performed in England (2003-2014) using administrative data from Hospital Episode Statistics. Results were compared to the hospitalized adult general population in England to calculate standardized incidence and mortality ratios. Data were analyzed for 19,883 kidney allograft recipients, with median follow-up 6.0 years' post-transplantation. Cancer incidence was more common after kidney transplantation compared to the general population in line with published literature (standardized incidence ratio 2.47, 95% CI: 2.34-2.61). In a Cox proportional hazards model, cancer development was associated with increasing age, recipients of deceased kidneys, frequent readmissions within 12 months post-transplant and first kidney recipients. All-cause mortality risk for kidney allograft recipients with new-onset cancer was significantly higher compared to those remaining cancer-free (42.0% vs. 10.3%, respectively). However, when comparing mortality risk for kidney allograft recipients to the general population after development of cancer, risk was lower for both cancer-related (standardized mortality ratio 0.75, 95% CI: 0.71-0.79) and noncancer-related mortality (standardized mortality ratio 0.90, 95% CI: 0.85-0.95), which contradicts reported literature. Although some plausible explanations are conceivable, our analysis likely reflects the limitations of administrative data for analyzing cancer data. Future studies require record linkage with dedicated cancer registries to acquire more robust and accurate data relating to cancer epidemiology after transplantation.

Hepatocellular cancer and recurrence after liver transplantation: what about the impact of immunosuppression?

Liver transplantation (LT) has originally been designed to treat hepatobiliary malignancies. The initial results of LT for hepatocellular cancer (HCC) were, however, dismal this mainly due to the poor patient selection procedure. Better surgical and perioperative care and, especially, the refinement of selection criteria led to a major improvement of results, making HCC nowadays (again!) one of the leading indications for LT. This evolution is clearly shown by the innumerable reports aiming to further extend inclusion criteria for LT in HCC patients. Nonetheless, the vast majority of papers only deals with morphologic (tumour diameter and number) and (only recently) biologic (tumour markers and response to locoregional treatment) parameters to do so. Curiously enough, the role of both the immune competent state of the recipient as well as the impact of both immunosuppression (IS) type and load has been very poorly addressed in this context, even if it has been shown for a long time, based on both basic and clinical research, that they all play a key role in the outcome of any oncologic treatment and in the development of de novo as well as recurrent tumours. This chapter aims to give, after a short introductive note about the currently used inclusion criteria of HCC patients for LT and about the role of IS in carcinogenesis, a comprehensive overview of the actual literature related to the impact of different immunosuppressive drugs and schemes on outcome of LT in HCC recipients. Unfortunately, up to now solid conclusions cannot be drawn due to the lack of high-level evidence studies caused by the heterogeneity of the studied patient cohorts and the lack of prospectively designed and randomized studies. Based on long-term personal experience with immunosuppressive handling in LT some proposals for further clinical research and practice are put forward. The strategy of curtailing and minimising IS should be explored in the growing field of transplant oncology taking thereby into account the immunological privilege of the liver allograft. These strategies will become more and more compelling when further extending the indications in which adjuvant chemotherapy will probably become an inherent part of the therapeutic scheme of HCC liver recipients.

Survival Benefit in Renal Transplantation Despite High Comorbidity

Background

The age and degree of comorbidity among transplant candidates is increasing. Knowledge of survival benefit in relation to recipient age and comorbidity is important, considering the scarcity of organs available for transplantation. The aim of the present study was to analyze the chances and survival benefit of transplantation among patients in different age groups and with different degrees of comorbidity score at the time of entering the waiting list.

Methods

Data from the Danish Nephrology Registry and Scandiatransplant were merged. Charlson Comorbidity Index scores were derived from the National Danish Admissions Registry. Study period is from January 1, 1995, to December 31, 2011. A multistate model was used to analyze the chance of having a renal transplantation and the effect of transplantation in different patients groups.

Results

Patients older than 65 years and patients with high comorbidity score had a decreased chance of being transplanted. However, if patients older than 65 years were transplanted with deceased donor, the mortality risk was reduced by 55% (hazard rate, 0.45 (0.26-0.75). In patients with a comorbidity score of 5 or greater, receiving a deceased donor transplant reduced the mortality risk by 72% (hazard rate, 0.28 (0.20-0.39). The overall survival benefit was 62% versus 70% in deceased versus living donor transplanted patients.

Conclusions

Poor health and old age reduced the chance of being transplanted. However, patients older than 65 years and patients with high comorbidity still had a survival benefit from renal transplantation.

De novo cancer in patients on dialysis and after renal transplantation: north-western Italy, 1997-2012

BACKGROUND

Kidney transplant recipients (KTR) are known to have a higher risk of cancer than the general population, especially of malignancies related to oncogenic viral infections. This study assessed the incidence of de novo malignancies (DNMs) in patients receiving kidney transplantation and in dialysis patients (DP) on the waiting list for transplantation at the same centre. The aim was to quantify the contribution of post-transplant immunosuppression to the underlying risk of developing a DNM in dialysis patients on the waiting list for kidney transplant.

METHODS

Cancer incidence rates were computed using the Kaplan-Meier product-limit method. The number of DNMs observed in both groups was compared to the expected incidence in the general Italian population through calculation of the standardized incidence ratios (SIR) and their 95% confidence intervals (CI). To identify risk factors, incidence rate ratios (IRR) and 95% CIs were computed using Poisson regression analysis. The comparison of incidence rates between the two cohorts was also performed using age standardized incidence rates (ASR) and their ratio (age standardized rate ratio, ASRR).

RESULTS

In 4858 person-years (PYs) of observation, 75 out of 735 KTR were diagnosed with DNM: 57 solid neoplasms, 13 post-transplant lymphoproliferative disorders (PTLD), and 12 Kaposi sarcomas (KS). The overall incidence was 17.5 cases/10³ PYs, resulting in a 2.1-fold increased risk. Twenty-four out of 912 DP, over a follow-up of 2400 PYs, were diagnosed with a solid neoplasm, but none had PTLD or KS. The use of induction therapy after transplant was associated with a significant increased risk of KS (IRR: 3.52; 95% CI 1.04-11.98, p < 0.05). ASRR for all cancers and for solid cancers only was 1.84- and 1.19-fold higher in KTR, respectively, than in the general population. The overall incidence in DP was 10.0 cases/10³ PYs, with a 1.6 significantly increased cancer risk compared to the general population.

CONCLUSION

Our study confirms the increased risk of cancer after transplantation and during dialysis, but showed that virus-related cancers only occur after post-transplant immunosuppression.

Incidence, risk factors and outcomes of de novo malignancies post liver transplantation

Liver transplantation (LT) is associated with a 2 to 7 fold higher, age and gender adjusted, risk of de novo malignancy. The overall incidence of de novo malignancy post LT ranges from 2.2% to 26%, and 5 and 10 years incidence rates are estimated at 10% to 14.6% and 20% to 32%, respectively. The main risk factors for de novo malignancy include immunosuppression with impaired immunosurveillance, and a number of patient factors which include; age, latent oncogenic viral infections, tobacco and alcohol use history, and underlying liver disease. The most common cancers after LT are non-melanoma skin cancers, accounting for approximately 37% of de novo malignancies, with a noted increase in the ratio of squamous to basal cell cancers. While these types of skin cancer do not impact patient survival, post-transplant lymphoproliferative disorders and solid organ cancer, accounting for 25% and 48% of malignancies, are associated with increased mortality. Patients developing these types of cancer are diagnosed at more advanced stages, and their cancers behave more aggressively compared with the general population. Patients undergoing LT for primary sclerosing cholangitis (particularly with inflammatory bowel disease) and alcoholic liver disease have high rates of malignancies compared with patients undergoing LT for other indications. These populations are at particular risk for gastrointestinal and aerodigestive cancers respectively. Counseling smoking cessation, skin protection from sun exposure and routine clinical follow-up are the current approach in practice. There are no standardized surveillance protocol, but available data suggests that regimented surveillance strategies are needed and capable of yielding cancer diagnosis at earlier stages with better resulting survival. Evidence-based strategies are needed to guide optimal surveillance and safe minimization of immunosuppression.

Kaposi's sarcoma presenting as violaceous macules on the chest of a kidney transplanted patient

Organ transplant recipients have a high incidence of cancer associated with persistent viral infections, such as human herpes virus 8. This virus is associated with Kaposi's sarcoma, and a change in the dose or type of immunosuppression regimen should be the first step in its treatment. A multidisciplinary approach with nephrologists, dermatologists and oncologists is necessary for the management of this disease. We report a clinical case with atypical presentation and discuss the treatment options.

HESI/FDA workshop on immunomodulators and cancer risk assessment: Building blocks for a weight-of-evidence approach

Profound immunosuppression (e.g., AIDS, transplant therapy) is epidemiologically associated with an increased cancer risk, and often with oncogenic viruses. It is currently unclear how broadly this association translates to therapeutics that modulate immunity. A workshop co-sponsored by the FDA and HESI examined how perturbing the immune system may contribute to carcinogenesis, and highlighted priorities for improving non-clinical risk assessment of targeted immunomodulatory therapies. Conclusions from the workshop were as follows. 1) While profound altered immunity can promote tumorigenesis, not all components of the immune system are equally important in defense against or promotion of cancer and a similar cancer risk for all immunomodulatory molecules should not be assumed. 2) Rodent carcinogenicity studies have limitations and are generally not reliable predictors of cancer risk associated with immunosuppression. 3) Cancer risk needs to be evaluated based on mechanism-based weight-of-evidence, including data from immune function tests most relevant to tumor immunosurveillance or promotion. 4) Information from nonclinical experiments, clinical epidemiology and immunomodulatory therapeutics show that immunosurveillance involves a complex network of cells and mediators. To support a weight-of-evidence approach, an increased focus on understanding the quantitative relationship between changes in relevant immune function tests and cancer risk is needed.

Immunosuppression and Multiple Primary Malignancies in Kidney-Transplanted Patients: A Single-Institute Study

Immunodeficiency is associated with higher cancer incidence. However, it is unknown whether there is a link between immunodeficiency and development of multiple primary malignancies. In the present study we analyse this link focusing on kidney-transplanted patients, as they are at higher risk of developing cancer due to the chronic assumption of immunosuppressants. We followed up 1200 patients who underwent kidney transplantation between 1980 and 2012. A total of 77/1200 kidney-transplanted patients developed cancer and 24 of them developed multiple cancers. Most multiple cancers were synchronous with a nonsignificant association between cancer and rejection episodes. In the general cancer population, one-ninth of patients are at higher risk of developing a second tumor over a lifetime; hence it would be reasonable to conclude that, from a merely theoretical and statistical viewpoint, long-term transplanted patients potentially have a higher risk of developing MPMs. However, data did not confirm this assumption, probably because these patients die before a second primary malignancy appears. Despite many observations on the increased incidence of different tumor types in immunodeficient patients and despite immunosuppression certainly being a predisposing factor for the multicancer syndrome, data so far are not robust enough to justify a correlation between immunodeficiency and multiple primary malignancies in transplanted patients.

Clinical and Genetic Factors Associated with Cutaneous Squamous Cell Carcinoma in Kidney and Heart Transplant Recipients

BACKGROUND

Cutaneous squamous cell carcinoma (cSCC) occurs with higher frequency and recurrence rates, increased morbidity and mortality, and more aggressive metastasis in kidney and heart transplant recipients compared to the general population but all transplant recipients do not develop cSCC. In addition, the phenotypic expression of cSCC among transplant recipients can vary between mild disease to extensive recurrent metastatic disease. These clinically observed differences in occurrence and severity of cSCC among transplant recipients suggest the possibility that an underlying genetic component might modify risk.

METHODS

We identified 88 white post-transplant cSCC cases (71 kidney and 17 heart) and 300 white post-transplant controls (265 kidney and 35 heart) using a DNA biobank linked with de-identified electronic medical records. Logistic regression was used to determine adjusted odds ratios (OR) for clinical characteristics and single nucleotide polymorphisms (SNP) associated with cSCC in both a candidate SNP and genome wide analysis.

RESULTS

Age (OR 1.08 [1.05-1.11], p<0.001) and azathioprine exposure (OR 8.64 [3.92-19.03], p<0.001) were significantly associated while gender, smoking tobacco use, dialysis duration and immunosuppression duration were not. Ten candidate SNPs previously associated with non-melanoma skin cancer in the general population were significantly associated with cSCC in transplant recipients. Genome wide association analysis implicated SNPs in genes previously associated with malignancy, CSMD1 (OR 3.14 [1.90-5.20]) and CACNA1D (OR 2.67 [1.73-4.10]).

CONCLUSIONS

This study shows an association of increasing age and azathioprine exposure with cSCC and confirms a genetic contribution for cSCC development in kidney and heart transplant recipients.

Preconditioning donor livers with cromolyn or compound 48/80 prolongs recipient survival in a rat orthotopic liver transplantation model

BACKGROUND

Acute rejection (AR) remains a challenge in organ transplantation. Preconditioning donor organs can reduce AR and prolong survival. Whether preconditioning with cromolyn (CRM), a mast cell (MC) stabilizer, or compound 48/80 (CMP 48/80), a MC degranulator, can alleviate AR and prolong survival has not been studied.

METHODS

We used the male-DA-to-female-Lewis-rat orthotopic liver transplantation (OLT) model. Donors were preconditioned with CRM in a MC stabilizing way (CRM group) or CMP 48/80 in a MC depleting way (CMP 48/80 group). Rats preconditioned with phosphate-buffered saline were used as controls (PBS group). After preconditioning, OLT surgeries were carried out. OLT male-Lewis-to-female-Lewis-rats were used as the syngeneic group (syngeneic group).

RESULTS

Rats in the PBS group developed AR rapidly and died at 7.40 ± 1.14 days. Rats in the CRM and CMP 48/80 groups had significantly slower rejections and died at day 17.40 ± 1.67 or 14.20 ± 2.28, respectively (P < .05). Rats in the syngeneic group survived more than 60 days. Rejection activity indexes (RAIs) and liver functions were all alleviated through CRM or CMP 48/80 preconditioning. Interferon-γ messenger RNA (mRNA) expressions were reduced and interleukin-10 mRNA levels were higher in allografts in the CRM and CMP 48/80 groups, compared with the PBS group. These were confirmed by testing serum interferon-γ and interlerkin-10.

CONCLUSION

Preconditioning donor livers with CRM or CMP 48/80 can reduce AR and prolong survival of recipients after OLT.

Epidemiology of de novo malignancies after solid-organ transplantation: immunosuppression, infection and other risk factors

Organ transplantation is an increasingly used medical procedure for treating otherwise fatal end-stage organ diseases, and a large number of anti-rejection drugs have been developed to prolong long-term survival of both the individual and the transplanted organ. However, the prolonged use of immunosuppressive drugs is well known to increase the risk of opportunistic diseases, particularly infections and virus-related malignancies. Although transplant recipients experience a nearly twofold elevated risk for all types of de novo cancers, persistent infections with oncogenic viruses are associated with up to hundredfold increased risks. Women of the reproductive age are growing in number among the recipients of solid-organ transplants, but specific data on cancer outcomes are lacking. This article updates evidences linking iatrogenic immunosuppression, persistent infections with oncogenic viruses, other risk factors and post-transplant malignancies. Epidemiological aspects, tumourigenesis related to oncogenic viruses, clinical implications, as well as primary and secondary prevention issues are discussed to offer clinicians and researchers alike an update of an increasingly important topic.

Improved detection reveals active β-papillomavirus infection in skin lesions from kidney transplant recipients

The aim of this study was to determine whether detection of β-HPV gene products, as defined in epidermodysplasia verruciformis skin cancer, could also be observed in lesions from kidney transplant recipients alongside the viral DNA. A total of 111 samples, corresponding to 79 skin lesions abscised from 17 kidney transplant recipients, have been analyzed. The initial PCR analysis demonstrated that β-HPV-DNA was highly present in our tumor series (85%). Using a combination of antibodies raised against the E4 and L1 proteins of the β-genotypes, we were able to visualize productive infection in 4 out of 19 actinic keratoses, and in the pathological borders of 1 out of 14 squamous cell carcinomas and 1 out of 31 basal cell carcinomas. Increased expression of the cellular proliferation marker minichromosome maintenance protein 7 (MCM7), that extended into the upper epithelial layers, was a common feature of all the E4-positive areas, indicating that cells were driven into the cell cycle in areas of productive viral infections. Although the present study does not directly demonstrate a causal role of these viruses, the detection of E4 and L1 positivity in actinic keratosis and the adjacent pathological epithelium of skin cancer, clearly shows that β-HPV are actively replicating in the intraepidermal precursor lesions of kidney transplant recipients and can therefore cooperate with other carcinogenic agents, such as UVB, favoring skin cancer promotion.