Dendritic cells and cutaneous T-cell lymphomas

Dendritic cells (DCs) are potent antigen-presenting cells that help orchestrate the innate and adaptive immune systems to induce tolerance and immunity. They are diversified in their phenotypes, stages of maturation, degrees of activation, and functions. Several subtypes of DCs exist among human lymphoid tissues, non-lymphoid tissues, and in peripheral blood. In the skin, three types of DCs are described: Langerhans cells (LCs), dermal dendritic cells (DDCs), and plasmacytoid dendritic cells (pDCs). In the peripheral blood, myeloid dendritic cells (mDCs) and plasmacytoid dendritic cells are well described. Dysfunctional DCs are found in many autoimmune disorders, allergies, and cancers. In this paper, we focus on DCs as related to cutaneous T cell lymphomas (CTCLs). Abnormal DC number and defective DC function are found in the blood of patients with advanced stage Sézary syndrome (SS), a leukemic variant of CTCLs. Extracorporeal photopheresis (ECP), an effective therapy for erythrodermic CTCLs, is thought to work by inducing apoptosis of tumor cells and monocytes-derived DCs. DC vaccination has been carried out successfully in some patients with CTCLs when combined with immune modifiers like toll like receptor agonists, which may enhance the function of DCs. However, DCs may perform a dual role in the pathogenesis of CTCLs. Immature DCs (langerhans cells) could promote the survival of malignant T cells. Further understanding of DCs and their role in CTCLs can help us to uncover the pathogenesis of this disease and to further explore the therapeutic uses of DCs.

Skin cancer in skin of color

In general, skin cancer is uncommon in people of color when compared to Caucasians. When it does occur, it is often associated with increased morbidity and mortality. Differences in survival rates may be attributed to skin cancers being diagnosed at a more advanced stage, and socioeconomic factors such as lack of adequate insurance coverage and lack of transportation can function as barriers to timely diagnosis and early treatment. In addition to advanced stage at presentation, malignant skin lesions in skin of color often present in an atypical fashion. Because skin cancer prevention and screening practices historically have been lower among Hispanics, Blacks, and Asians, and given the changing demographics in the United States, interventions that are tailored to each of these groups will be needed. Public educational campaigns should be expanded to educate people of all skin types with emphasis on skin cancers occurring in areas not exposed to the sun (Byrd-Miles et al., 2007), since sunlight is not as important an etiologic factor in the pathogenesis of skin cancer in people of color. Dermatologists and primary care physicians should instruct their darker-skinned patients on how to perform routine skin self-examinations. Physicians should also encourage patients to ask their specialists such as their gynecologist, dentist, and ophthalmologist to look for abnormal pigmentation during routine exams. To reduce the burden of skin cancer, several prevention methods for all people have been strongly encouraged, including monthly self-examinations, daily use of SPF 30 or greater sunscreen, sunglasses with UV-absorbing lenses, and avoiding tanning booths (American Cancer Society, 2008) (see Table 7). In addition, recommendations for clinicians to promote the prevention of skin cancer in skin of color have also been made, including closely monitoring changing pigmented lesions on the palms and soles and hyperkeratotic or poorly healing ulcers in immunosuppressed patients (Halder & Bridgeman-Shah, 1995) (see Table 7).

Bexarotene

Bexarotene is a selective retinoid X receptor (RXR) agonist. It binds to, and activates RXRs which function as ligand-activated transcription factors that control gene expression. This leads to modulation of cell growth, apoptosis, and differentiation. In patients with refractory or persistent early stage cutaneous T cell lymphoma (CTCL), the overall response rate was 54% after oral bexarotene 300 mg/m2/day. The overall response rate in patients with refractory or persistent advanced stage CTCL was 45% at the same dosage. An overall response rate of 63% was reported after topical bexarotene 0.1 to 1% twice daily in patients with early stage CTCL. Another trial reported an overall response rate of 44% after topical bexarotene 1% once daily escalated up to 4 times daily. Plaque elevation was significantly reduced, and the severity of moderate to severe psoriasis was substantially improved in patients receiving oral bexarotene 0.5 to 2 mg/kg/day. At clinically relevant oral dosages, bexarotene significantly decreases levels of serum thyrotropin and free thyroxine. The most common adverse events associated with oral bexarotene are hypertriglyceridemia, hypercholesterolemia, central hypothyroidism and headache. Reversible acute pancreatitis has occurred during oral bexarotene therapy. Adverse events associated with the topical formulation are limited to rash, pruritus, and pain.