Langerhans cells in benign, premalignant and malignant skin lesions of renal transplant recipients and the effect of retinoid therapy

The Tumor Immune Microenvironment in Cutaneous Squamous Cell Carcinoma Arising in Organ Transplant Recipients

Cutaneous squamous cell carcinoma (cSCC) is the most common malignancy in immune-suppressed organ transplant recipients (OTRs). Whilst rates of other malignancies (both cutaneous and non-cutaneous) are elevated in this population, the increase is far less striking. This suggests that cSCC must be a highly immunogenic tumor. The tumor immune microenvironment is altered in cSCC from OTRs. It has reduced anti-tumor properties and instead provides an environment that facilitates tumor growth and survival. Understanding the composition and function of the tumor immune microenvironment in cSCC from OTRs is useful for prognostication and therapeutic decisions.

Advances in Cutaneous Squamous Cell Carcinoma Management

Simple Summary

Cutaneous squamous cell carcinoma (cSCC) is an increasingly prevalent and morbid cancer worldwide. Management of this cancer has changed significantly in the last decade through improved risk stratification and new therapies offering patients with locally advanced and metastatic disease more effective, less toxic, and more durable treatment options. Ongoing clinical trials are assessing new therapeutic options as well as optimizing existing regimens in efforts to better manage this cancer. The recent developments highlight the need for multidisciplinary care, especially for those with locally advanced and metastatic disease.

Abstract

cSCC is increasing in prevalence due to increased lifespans and improvements in survival for conditions that increase the risk of cSCC. The absolute mortality of cSCC exceeds melanoma in the United States and approaches that of melanoma worldwide. This review presents significant changes in the management of cSCC, focusing on improvements in risk stratification, new treatment options, optimization of existing treatments, and prevention strategies. One major breakthrough in cSCC treatment is the advent of immune checkpoint inhibitors (ICIs) targeting programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1), which have ushered in a renaissance in the treatment of patients with locally advanced and metastatic disease. These agents have offered patients with advanced disease decreased therapeutic toxicity compared to traditional chemotherapy agents, a more durable response after discontinuation, and improved survival. cSCC is an active field of research, and this review will highlight some of the novel and more developed clinical trials that are likely to impact cSCC management in the near future.

Langerhans cells and melanocytes share similar morphologic features under in vivo reflectance confocal microscopy: a challenge for melanoma diagnosis

BACKGROUND

Intraepidermal Langerhans cells (ILC) are difficult to differentiate from melanocytes under reflectance confocal microscopy (RCM) and their presence may simulate pagetoid spread of melanocytes on RCM images.

OBJECTIVE

We sought to correlate bright round and dendritic cells in a pagetoid pattern identified on RCM with findings of conventional histopathology and immunohistochemistry for lesions that were falsely diagnosed as melanoma by RCM.

METHODS

This retrospective study included histopathologically proven nevi, imaged by RCM, which displayed bright cells in a pagetoid pattern (BCPP) under RCM, resulting in the incorrect RCM diagnosis of melanoma. Morphological comparisons were made between RCM images of nevi showing BCPP, histopathologically proven melanomas displaying BCPP, and biopsy-proven nevi without BCPP.

RESULTS

We identified 24 nevi that were falsely diagnosed as melanoma by RCM because of the presence of BCPP. These pagetoid cells on RCM corresponded on histopathology to ILC with a high density in 23 of the 24 nevi (95%) and to melanocytes in 7 of the 24 nevi (29%). Among 6 melanomas displaying BCPP on RCM, ILC with high density were observed histopathologically in 5 of the 6 cases (83%) and pagetoid melanocytes were seen in all 6 cases (100%).

LIMITATIONS

The results cannot be generalized to clinically banal-appearing nevi.

CONCLUSIONS

Although the finding of BCPP is a useful RCM feature for the diagnosis of melanoma, it does not always imply the presence of pagetoid melanocytes but may at times represent ILC.

About the cutaneous targets of bexarotene in CTCL patients

There are several approved therapies for cutaneous T-cell lymphoma (CTCL). The retinoids are one of the major biologic response modifiers used in CTCL, producing good response rates but few complete responses. Bexarotene has been demonstrated to act on malignant T-cells by inducing their apoptosis, but nothing is known about its role on keratinocytes and Langerhans cells. Immunohistochemical analysis using CD1a, HLA-DR, ICAM-1 (activation markers), CD95 and CD40 (apoptosis markers) was conducted on frozen sections of bexarotene-exposed cutaneous explants and skin biopsy specimens from patients treated with bexarotene. None of the studied markers was significantly modulated both on cutaneous explants and on skin biopsy specimens after treatment with bexarotene, compared to controls. Langerhans cells and keratinocytes do not appear to play a central role in the therapeutic control of CTCL by bexarotene therapy. The main bexarotene's target thus remains T-cells by inducing their apoptosis, a mechanism that is different from the other retinoids used in CTCL.

Langerhans' cells and smoking in intraepithelial neoplasia of the cervix

OBJECTIVE

To compare the intraepithelial population of Langerhans' cells (LC) in normal cervix epithelium adjacent to cervical intraepithelial neoplasia grade 3 (CIN 3) and correlate to smoking habit.

METHODS

Cases in this study included conization specimens from 48 women affected by CIN 3. The LC count was performed in areas without histopathologic alteration adjacent to CIN 3. The control group is compound by normal cervix from 46 hysterectomy specimens. The identification of LC was done by immunohistochemical study demonstrating immunoreactivity to S-100 protein. The number of intraepithelial LC was determined using 400x magnification light microscope in 10 high-power fields, and results were expressed in number of cells per square millimeter (LC/mm(2)).

RESULTS

In the control group, there was lower number of Langerhans' cells in smokers than in non-smokers (P = 0.045). There was lower number of Langerhans' cells in normal areas adjacent to CIN 3 than in normal cervix control group (P = 0.004). There was no significant difference in the number of Langerhans' cells in normal areas of the cervix with CIN 3 between smokers and non-smokers (P = 0.991). The number of cigarettes consumed daily, time of consume, total number of cigarettes consumed showed a reduced LC count, yet was not statistically significant.

CONCLUSIONS

It was revealed that smoking reduces the number of intraepithelial Langerhans' cells in the uterine cervix. In women with CIN 3, the LC count was lower, despite the habit of smoking.

Mechanisms of the self/non-self-survey in the defense against cancer: Potential for chemoprevention?

When compared to a reference population, several large epidemiological studies with long-term follow-up have reported a three- to five-fold increased risk of neoplasia amongst patients who have received organ transplants, with an incidence curve that rises in a linear fashion with time. The relationship between the immune system and cancer is complex. The ability to discriminate "self" from "non-self" is one of the central roles of the immune system. Since tumors arise from transformation of host cells, it is not surprising that some aspects of tumor immunity resemble autoimmunity. The immune response to tumors shares aspects of both self- and non-self-immune recognition. What accounts for the apparent failure of immunity? In this review article, we address the role of the self/non-self-survey in the immune response to tumors, we describe mechanisms of immune surveillance against tumor cells, and we discuss models of ignorance, tolerance and tumor evasion of the immune response. The overall aim of the article is to demonstrate the scope for prevention of cancer in individuals at increased risk of developing malignancy due to immune compromise. Interventional strategies may involve the use of pro-differentiation agents such as retinoids, modifiers of polyamine biosynthesis or inhibitors of cyclooxygenase isozymes.

Systemic strategies for chemoprevention of skin cancers in transplant recipients

BACKGROUND

Solid organ transplant recipients (OTRs) are a growing population at high risk for cutaneous neoplasms, resulting in significant post-transplant morbidity and mortality. Management of malignant and pre-malignant cutaneous lesions in transplant recipients is challenging, making prevention of such neoplasms paramount. The objectives of the present study are to review and analyze systemic strategies for chemoprevention of malignant and pre-malignant cutaneous neoplasms in OTRs.

METHODS

MEDLINE and PubMed searches were performed to identify studies with original data quantifying the effects of systemic agents on the development of malignant cutaneous neoplasms in patients with solid organ transplants.

RESULTS

We identified nine studies describing 111 transplant recipients that quantified the effects of oral retinoids on cutaneous neoplasms. A majority of the studies found a decrease in the number of malignant and pre-malignant cutaneous lesions in patients treated with systemic retinoids, with several studies noting increased benefit in those patients with multiple previous skin cancers. Multiple studies described a rebound effect, with increased numbers of neoplasms occurring following discontinuation of retinoids. Side effects often limited dosing, but required discontinuation of retinoids in a minority of patients. No studies were identified that adequately quantified the effects of other systemic agents on skin cancer incidence in this population.

CONCLUSIONS

Although systemic retinoids are frequently used for chemoprevention of cutaneous malignancies in OTRs, the data supporting their use are composed largely of small uncontrolled case reports and case series. However, the available data suggest that retinoids have chemopreventative effects in this population. Although optimal dosing and indications for initiation of systemic retinoid therapy are not conclusive from the data, it suggests that retinoids are most effective in patients with multiple previous non-melanoma skin cancers. Side effects and beneficial effects were noted across a wide range of doses, suggesting that retinoids should be initiated at a low dose and increased as tolerated to a minimally effective dose. Further investigation through randomized controlled trials is needed to further clarify the tolerability and efficacy of multiple dosing regimens on the incidence of pre-malignant and malignant lesions in transplant recipients. The therapeutic role of other systemic agents in the transplant population has not been established.

Acitretin treatment in (pre)malignant skin disorders of renal transplant recipients: histologic and immunohistochemical effects

BACKGROUND

The incidence of (pre)malignant skin lesions after renal transplantation is high. Acitretin treatment appears to decrease the number of new squamous cell carcinomas and ameliorates the aspect and reduces the number of actinic keratoses. However, no histologic and immunohistochemical studies have been performed to further substantiate these observations.

METHODS

In 33 renal transplant recipients, biopsies were taken before and after 3 months of treatment with acitretin in doses up to 0.4 mg/kg/day. Histologic and immunohistochemical parameters for dysplasia, epidermal thickness, proliferation, differentiation, apoptosis, and dermal inflammation were analyzed.

RESULTS

Following acitretin treatment, a significant reduction in epidermal thickness (P =.002) and a significant increase in normal differentiation parameter K10 (P =.02) was observed. Epidermal proliferation did not change, nor did apoptosis, inflammation, keratinocytic epidermal neoplasia score, or transglutaminase staining. At baseline, in 8 actinic keratoses, a single cell expression pattern of K13 and/or K19 was found. This was associated with high levels of parameters indicative of high-risk lesions (P <.05). After acitretin treatment, an increase in K13 (P =.006) and K19 (P =.05) was found, together with a change in expression towards a focal or band-like staining pattern.

CONCLUSION

Acitretin improves the aspect of actinic keratoses via alteration of keratinization, resulting in peeling of the stratum corneum. No significant change in proliferation was found, which may explain the rapid recurrence of actinic keratoses seen after cessation of acitretin treatment.

Skin cancer in organ transplant recipients: Epidemiology, pathogenesis, and management

In the United States more than 100,000 people are living with solid organ transplants. The intense immunosuppressive regimens necessary for prolonged survival of allografts significantly increase the rates of both internal and cutaneous malignancies in recipients of solid organ transplants. Skin cancer is the most common cancer in patients after transplantation. Because of the early onset and high tumor burden in transplant recipients, dermatologists have significant challenges in managing the treatment of these patients. This article describes the epidemiology and clinical presentation of skin cancer during posttransplantation immunosuppression, discusses pathogenic cofactors, and reviews the optimal management for mild and severe skin cancer in transplant recipients.