Role of retinoids in skin cancer treatment and prevention

Mechanistic aspects of carotenoid health benefits - where are we now?

Dietary intake and tissue levels of carotenoids have been associated with a reduced risk of several chronic diseases, including cardiovascular diseases, type 2 diabetes, obesity, brain-related diseases and some types of cancer. However, intervention trials with isolated carotenoid supplements have mostly failed to confirm the postulated health benefits. It has thereby been speculated that dosing, matrix and synergistic effects, as well as underlying health and the individual nutritional status plus genetic background do play a role. It appears that our knowledge on carotenoid-mediated health benefits may still be incomplete, as the underlying mechanisms of action are poorly understood in relation to human relevance. Antioxidant mechanisms - direct or via transcription factors such as NRF2 and NF-κB - and activation of nuclear hormone receptor pathways such as of RAR, RXR or also PPARs, via carotenoid metabolites, are the basic principles which we try to connect with carotenoid-transmitted health benefits as exemplified with described common diseases including obesity/diabetes and cancer. Depending on the targeted diseases, single or multiple mechanisms of actions may play a role. In this review and position paper, we try to highlight our present knowledge on carotenoid metabolism and mechanisms translatable into health benefits related to several chronic diseases.

Successful Treatment of Multiple Premalignant and Malignant Lesions in Arsenical Keratosis with a Combination of Acitretin and Intralesional 5-Fluorouracil

A case of arsenical keratosis with multiple lesions of Bowen's disease and squamous cell carcinoma is described. The patient was successfully treated with a combination of acitretin and intralesional 5-fluorouracil. All the lesions resolved after three months of therapy with no side effects and no recurrence during four months of follow-up.

Topical retinoids in skin ageing: a focused update with reference to sun-induced epidermal vitamin A deficiency

Vitamin A is an important constituent of the epidermis, where it plays a crucial role in epidermal turnover. A deficiency of epidermal vitamin A may be the consequence of nutritional vitamin A deficiency, exposure to sunlight or any UV source, oxidative stress or chronological ageing. As a consequence, any treatment aiming at increasing epidermal vitamin A would exert a protective effect against these deleterious conditions. Retinoids may counteract some deleterious actions of UV radiation by physical and biological mechanisms. Topical natural retinoic acid precursors such as retinaldehyde or retinol are less irritant than acidic retinoids and may prevent epidermal vitamin A deficiency due to nutritional deficiency, exposure to sunlight or any condition leading to free radical production. Retinoids may be combined with other compounds with complementary actions against ageing, nutritional deficiency and cancer, such as antioxidants, to potentiate their beneficial effects in the skin.

Cyclosporin A treatment in severe childhood psoriasis

Though used occasionally, systemic therapies in severe childhood psoriasis have not been systematically investigated. Cyclosporin A (CysA) is effective in adults with severe psoriasis but there are no extensive data regarding the efficacy and safety of its use in childhood psoriasis. In this paper, we describe six children aged between 11 months and 13 years (average: 7.6 years) treated with CysA microemulsion formulation for severe psoriasis, who had been unresponsive to other treatments. The CysA dose ranged from 2 to 4 mg/kg/day, for periods varying from 8 to 105 weeks (mean: 54 weeks). Dose tapering was gradual after lesion improvement and adjusted according to clinical response. Adjuvant therapy with topical steroids, vitamin D3 ointments, coal tar preparations or anthralin was used in all children. Acitretin was used in three patients for short periods. The children were regularly monitored for serum renal and liver function and blood pressure. Improvement of skin lesions was achieved after between 4 and 30 (mean: 12) weeks of treatment, with complete remission in three children. Relapse of lesions occurred in the other children during CysA reduction, but they responded to a dose increase. The treatment was found to be well tolerated and with no significant side-effects. CysA can be used in carefully selected and monitored patients and may represent an alternative tool for severe episodes of psoriasis in children, when other therapies are unsuccessful.

Spectral properties of topical retinoids prevent DNA damage and apoptosis after acute UV-B exposure in hairless mice

We showed in a recent study that topical retinyl palmitate prevented UV-B-induced DNA damage and erythema in humans. Given that retinyl palmitate is a precursor of retinoic acid, the biological form of vitamin A that acts through nuclear receptors, we wondered whether these protective effects toward UV-B exposure were either receptor dependent or linked to other properties of the retinoid molecule such as its spectral properties. We determined the epidermal retinoid profile induced by topical retinoic acid in hairless mice and analyzed its effect on markers of DNA photodamage (thymine dimers) and apoptosis following acute UV-B exposure; we compared these effects to those induced by other natural topical retinoids (retinaldehyde, retinol and retinyl palmitate) which do not directly activate the retinoid receptors. We then analyzed the direct action of these retinoids on UV-B-induced DNA damage and apoptosis in cultured A431 keratinocytes. Topical retinoic acid significantly decreased (approximately 50%) the number of apoptotic cells, as well as the formation of thymine dimers in the epidermis of mice exposed to acute UV-B. Interestingly, the other topical retinoids decreased apoptosis and DNA damage in a similar way. On the other hand, neither retinoic acid nor the other retinoids interfered with the apoptotic process in A431 keratinocytes exposed to UV-B, whereas DNA photodamage was slightly decreased. We conclude that the decrease of apoptotic cells in hairless mouse epidermis following topical retinoids and UV-B irradiation reflects a protection of the primary targets of UV-B (DNA) by a mechanism independent of the activation of retinoid nuclear receptors, rather than a direct inhibition of apoptosis.

Expression of RPE65, a putative receptor for plasma retinol-binding protein, in nonmelanocytic skin tumours

BACKGROUND

In a recent report we described RPE65, a protein originally characterized in retinal pigment epithelium, to be expressed in normal human epidermis. RPE65 is suspected to be involved in cellular uptake of retinol which is transported in the bloodstream complexed with plasma retinol-binding protein.

OBJECTIVES

To evaluate protein and mRNA expression of RPE65 in actinic keratosis (AK), squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) compared with normal skin.

METHODS

RPE65 mRNA expression in skin tumours relative to normal skin of the respective donor was studied by real-time polymerase chain reaction in AK (n = 15), invasive SCC (n = 30) and BCC (n = 18). A peptide-specific anti-RPE65 antibody was used for immunohistochemical staining of formalin-fixed and paraffin-embedded tissue sections of the respective tumours.

RESULTS

RPE65 mRNA expression was reduced in AK. A highly significant reduction of RPE65 mRNA was observed in invasive SCC relative to normal skin of the respective donors. Immunohistochemistry revealed a continuous staining of basal and suprabasal keratinocytes in normal human epidermis. RPE65 in AK shown by immunohistochemical staining was reduced and quite irregular, whereas invasive SCC revealed no staining of tumour cells with the anti-RPE65 antibody. RPE65 mRNA values were elevated, whereas immunohistochemical staining for RPE65 protein was heterogeneous in BCC.

CONCLUSIONS

These results suggest progressive downregulation of RPE65 from AK to invasive SCC.

Acitretin and skin cancer in kidney transplanted patients. Clinical and histological evaluation and immunohistochemical analysis of lymphocytes, natural killer cells and Langerhans' cells in sun exposed and sun protected skin

BACKGROUND

Renal transplanted recipients have an increased incidence of actinic keratosis and skin cancer.

METHODS

In order to examine the chemoprophylatic effects of low-dose acitretin on keratosis and skin cancer development we submitted 13 renal transplanted patients who presented actinic keratosis to acitretin therapy (20 mg/d) for 12 months. The patients were assessed at monthly intervals during the first 6 months and every 2 months until the 12th month for new skin lesions and for acitretin toxicity. Normal skin biopsies of sun exposed and sun protected areas were taken for histopathological examination and submitted to immunohistochemistry technique to demonstrate CD4+ and CD8+ T lymphocytes, natural killer (NK) cells and Langerhans' cells which were counted and compared before, after 6 and 12 months of the treatment.

RESULTS

There was an improvement of actinic keratosis in all patients. Only one patient developed new skin cancer. Side-effects were well tolerated and no significant biochemical effects were observed. There were no differences in the microscopic aspects of the skin and in the number of CD4+ and CD8+ T lymphocytes and NK cells. There was a significant increase in the number of epidermal Langerhans' cells after 12 months of acitretin therapy.

CONCLUSIONS

The data obtained permit us to conclude that low dose acitretin therapy is safe, well tolerated and partially effective in chemoprophylaxis of skin cancer in renal transplant recipients. The increase in epidermal Langerhans' cells observed may be an expression of the immunomodulatory effect of acitretin.

Medical therapies for non-melanoma skin cancer

The epidemic of nonmelanoma skin cancer (NMSC) continues, in part due to aging of the world's population, the frequency of early childhood sunburns, and episodic intense recreational sun exposure as opposed to sun exposure related to outdoor occupations. A nonsurgical approach to selected skin cancers could potentially decrease the expense and morbidity of surgical treatment for NMSC. The increase of comorbid medical conditions in the elderly makes alternatives to surgical management preferable under certain circumstances. This review will discuss medical alternatives ranging from biologic response modifiers to COX-2 inhibitors to lifestyle modifications, as well as their roles in the management of NMSC. This preliminary information will expand to include more therapeutic options for NMSC in the future. Further clinical trials are needed to better elucidate possible alternative treatment strategies for NMSC.

Stage-specific effect of N-(4-hydroxyphenyl)retinamide on cell growth in squamous cell carcinogenesis

Squamous cell carcinoma (SCC) is the most prevalent form of epithelial cancer. SCC results when normal epithelial cells undergo multiple neoplastic changes that culminate in the evolution of an invasive cancer. Retinoids are commonly used as chemopreventive and treatment agents in skin cancer; however, SCC progression is accompanied by a gradual loss of retinoid responsiveness. The synthetic retinoid N-(4-hydroxyphenyl)retinamide (HPR) has shown promising anti-neoplastic activity in a variety of tumor cells, including those that are resistant to all-trans retinoic acid (t-RA). We investigated the effect of HPR on growth and apoptosis of squamous cells at different stages of carcinogenesis. We then determined if retinoic acid receptor (RAR) overexpression affected the outcome of HPR treatment. To model SCC malignant progression, we used a panel of murine keratinocytes representing different stages of squamous cell carcinogenesis. This panel consisted of primary keratinocytes, SP1 and 308 papilloma cell lines, the PAM-212 squamous carcinoma cell line, and the spindle I7 cell line. With the exception of the primary keratinocytes, all cells were unresponsive to t-RA treatment. Pharmacological concentrations of HPR were non-cytotoxic to all keratinocytes tested and HPR sensitivity was stage-dependent, with the papilloma cell lines being the most sensitive, and the spindle cells being the most resistant. Overexpression of RARgamma in SP1 papilloma cells enhanced growth suppression and apoptosis induction by HPR. HPR-induced growth suppression was accompanied by a simultaneous block in the G(1) phase of the cell cycle in RAR-transduced and control SP1 cells and differential regulation of cell cycle and apoptotic mediators.

Combination therapy to treat moderate to severe psoriasis

In patients with moderate-to-severe psoriasis, remission can be difficult to achieve and sustain. Both acutely acting and long-term maintenance agents are needed. Speed and efficiency of available monotherapies tend to be inversely proportional to safety. Combination, rotational, and sequential approaches are often more effective and safer than single-agent therapy. Combining agents with complementary adverse effect profiles is preferable. Apparent synergistic enhancement is seen with most paired combinations of the four major therapies: acitretin, phototherapy (ultraviolet B/psoralen plus ultraviolet A), cyclosporine, and methotrexate. Of those, only cyclosporine in combination with psoralen plus ultraviolet A is contraindicated because of increased cancer risk. Combinations of each of those major therapies with topical agents (retinoids, steroids, vitamin D derivatives, and others) have been used with varying efficacy and safety. The immunomodulators, hydroxyurea and thioguanine, have also shown some success in combination therapy. The new biologic agents with their novel modes of action and adverse effect profiles may prove to be important adjuncts in combination/rotational/sequential approaches. In some cases, monotherapy (with either systemic agents or phototherapy) adequately controls moderate to severe disease. A regimen using a single agent has the advantages of lower cost and greater adherence by the patient. For any number of reasons, however, including loss of efficacy, adverse effects, or cumulative or acute toxicity-and especially the inability to clear resistant lesions-a single modality will not be adequate. Using two or more therapies is thus the rule rather than the exception for most patients with moderate-to-severe psoriasis, but picking a combination that serves to balance safety and efficacy needs careful consideration, especially since no evidence-based treatment guidelines exist.

Skin cancer chemoprevention: strategies to save our skin

There are over 1 million cases of skin cancer diagnosed yearly in the United States. The majority of these are nonmelanoma (NMSCs) and are associated with chronic exposure to ultraviolet light (UV). Actinic keratosis (AK) has been identified as a precursor for SCC, but not for BCC. AKs are far more common than SCC, making them excellent targets for chemoprevention. Cancer chemoprevention can prevent or delay the occurrence of cancer in high-risk populations using dietary or chemical interventions. We have developed strategies that have rational mechanisms of action and demonstrate activity in preclinical models of skin cancer. Promising agents proceed to phase I-III trials in subjects at high risk of skin cancer. UV light induces molecular signaling pathways and results in specific genetic alterations (i.e., mutation of p53) that are likely critical to skin cancer development. UVB-induced changes serve as a basis for the development of novel agents. Targets include inhibition of polyamine or prostaglandin synthesis, specific retinoid receptors, and components of the Ras and MAP kinase signaling pathways. Agents under study include: epigallocatechin gallate (EGCG), a green tea catechin with antioxidant and sunscreen activity, as well as UVB signal transduction blocking activity; perillyl alcohol, a monoterpene derived from citrus peel that inhibits Ras farnesylation; difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase and polyamines; retinoids that target retinoid X receptors and AP-1 activity; and nonsteroidal anti-inflammatory agents that inhibit cylooxygenase and prostaglandin synthesis. We performed a series of Phase I-II trials in subjects with multiple AK. For example, a phase II randomized trial of topical DFMO reduced AK number, suppressed polyamines, and reduced p53 protein. Our goal is to develop agents for use in combination and/or incorporation into sunscreens to improve chemoprevention efficacy and reduce skin cancer incidence.

Vitamin A and infancy. Biochemical, functional, and clinical aspects

Vitamin A is a very intriguing natural compound. The molecule not only has a complex array of physiological functions, but also represents the precursor of promising and powerful new pharmacological agents. Although several aspects of human retinol metabolism, including absorption and tissue delivery, have been clarified, the type and amounts of vitamin A derivatives that are intracellularly produced remain quite elusive. In addition, their precise function and targets still need to be identified. Retinoic acids, undoubtedly, play a major role in explaining activities of retinol, but, recently, a large number of physiological functions have been attributed to different retinoids and to vitamin A itself. One of the primary roles this vitamin plays is in embryogenesis. Almost all steps in organogenesis are controlled by retinoic acids, thus suggesting that retinol is necessary for proper development of embryonic tissues. These considerations point to the dramatic importance of a sufficient intake of vitamin A and explain the consequences if intake of retinol is deficient. However, hypervitaminosis A also has a number of remarkable negative consequences, which, in same cases, could be fatal. Thus, the use of large doses of retinol in the treatment of some human diseases and the use of megavitamin therapy for certain chronic disorders as well as the growing tendency toward vitamin faddism should alert physicians to the possibility of vitamin overdose.

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.

Chemoprevention of human skin cancer

The incidence of skin cancer has been rising in recent years with significant effects on public health. Primary prevention has proven inadequate in impacting the incidence of skin cancer, thus stimulating the development of chemopreventive strategies. The majority of skin cancer chemoprevention studies focus on occurrence of new nonmelanoma skin cancers (NMSC) in individuals with a previous NMSC, or on reduction in the number of premalignant skin lesions such as actinic keratoses (AK). Dysplastic nevi, a likely precursor of melanoma, are also potential targets for chemoprevention strategies. Premalignant lesions are especially attractive as endpoints since they are more common than frank cancer, resulting in reduced sample size, length, and cost of clinical trials. Development of new agents that affect the pathogenesis of skin cancer will be discussed, from elucidation of molecular targets to implementation of trials designed to determine the effects of chemopreventive interventions on human skin cancer.

Treatment of arsenical keratosis and Bowen's disease with acitretin

BACKGROUND

Long-term exposure to arsenic is associated with the development of arsenical keratosis, Bowen's disease, squamous cell carcinoma, and basal cell carcinoma. The efficacy of acitretin therapy was examined in two patients with cutaneous arsenical neoplasms.

METHODS

Lipid profile, hematological and liver function tests were performed regularly during the therapy at monthly intervals.

RESULTS

After the third month of treatment, improvement of lesions of arsenical keratosis and Bowen's disease were observed in both patients. For the first patient who received 1 mg/kg daily acitretin for 10 months nearly total clearing was obtained at the end of therapy. The second patient discontinued the treatment after a period of 5 months because of symptomatic side-effects. During therapy no new lesions and no laboratory side-effects were observed in either patient.

CONCLUSIONS

Although these results need to be confirmed by larger, long-term trials, it appears that acitretin is effective in the treatment of Bowen's disease related with arsenic, as well as arsenical keratosis.

The management of melanoma and nonmelanoma skin cancer: a review for the primary care physician

In the United States, the incidence of skin cancer is greater than that of all other cancers combined, and early diagnosis can be lifesaving. A substantial public health concern, skin cancer is increasingly being diagnosed and managed by primary care physicians. Basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) (known collectively as nonmelanoma skin cancer) and malignant melanoma are the most common cutaneous malignancies. Shave biopsy is usually performed if BCC is suspected; punch biopsy is preferred if SCC is thought to be present. The choice of biopsy techniques depends on the presumed depth of the lesion. Treatment has 3 goals: complete eradication of the cancer and preservation or restoration of normal function and cosmesis. Risk of recurrence or metastasis determines whether the tumor is high risk or low risk. Based on the level of risk, treatment options are considered, including whether the patient can be treated by a primary care physician or should be referred to a dermatologist. Choice of treatment approach depends on the tumor's location, size, borders, and growth rate. The standard treatment approaches are superficial ablative techniques (electro-desiccation and curettage and cryotherapy) used primarily for low-risk tumors and full-thickness techniques (Mohs micrographic surgery, excisional surgery, and radiotherapy) used to treat high-risk tumors. Removal of the entire tumor is essential to limit and prevent tumor recurrence.

Skin cancer in the elderly

This article describes the clinical features, treatment options, and prognosis of the most common skin cancers: basal cell carcinoma, squamous cell carcinoma, and melanoma. Emphasis is placed on specific issues that need to be considered when dealing with cancers of the skin in the elderly population. In addition, issues surrounding the early detection and prevention of skin cancer are addressed.

Cutaneous malignancies and their management

Skin cancer is the most common malignancy occurring in humans, and the incidence of basal cell carcinoma, squamous cell carcinoma, and melanoma continues to rise. Advances in the diagnosis and treatment of skin cancer have led to more successful management of these tumors. A number of options for the treatment of skin cancer are available to the patient and physician, allowing for high cure rates and excellent functional and cosmetic outcomes.