Diona L. Damian

Nicotinamide (vitamin B₃) has a range of photoprotective effects in vitro and in vivo; it enhances DNA repair, reduces UV radiation‐induced suppression of skin immune responses, modulates inflammatory cytokine production and skin barrier function and restores cellular energy levels after UV exposure. Pharmacological doses of nicotinamide have been shown to reduce actinic keratoses and nonmelanoma skin cancer incidence in high‐risk individuals, making this a nontoxic and accessible option for skin cancer chemoprevention in this population.

Nonmelanoma skin cancers, such as basal-cell carcinoma and squamous-cell carcinoma, are common cancers that are caused principally by ultraviolet (UV) radiation. Nicotinamide (vitamin B₃) has been shown to have protective effects against damage caused by UV radiation and to reduce the rate of new premalignant actinic keratoses.

Arsenic-induced skin cancer is a significant global health burden. In areas with arsenic contamination of water sources, such as China, Pakistan, Myanmar, Cambodia and especially Bangladesh and West Bengal, large populations are at risk of arsenic-induced skin cancer. Arsenic acts as a co-carcinogen with ultraviolet (UV) radiation and affects DNA damage and repair. Nicotinamide (vitamin B3) reduces premalignant keratoses in sun-damaged skin, likely by prevention of UV-induced cellular energy depletion and enhancement of DNA repair. We investigated whether nicotinamide modifies DNA repair following exposure to UV radiation and sodium arsenite. HaCaT keratinocytes and ex vivo human skin were exposed to 2μM sodium arsenite and low dose (2J/cm²) solar-simulated UV, with and without nicotinamide supplementation. DNA photolesions in the form of 8-oxo-7,8-dihydro-2′-deoxyguanosine and cyclobutane pyrimidine dimers were detected by immunofluorescence. Arsenic exposure significantly increased levels of 8-oxo-7,8-dihydro-2′-deoxyguanosine in irradiated cells. Nicotinamide reduced both types of photolesions in HaCaT keratinocytes and in ex vivo human skin, likely by enhancing DNA repair. These results demonstrate a reduction of two different photolesions over time in two different models in UV and arsenic exposed cells. Nicotinamide is a nontoxic, inexpensive agent with potential for chemoprevention of arsenic induced skin cancer.

Nicotinamide has shown potential as a safe and effective intervention for the prevention of malignant and premalignant skin lesions. Recent studies have shown that nicotinamide, in both oral and topical forms, is able to prevent ultraviolet-induced immunosuppression in humans [1,2,3] and mice [4,5]. Immunosuppression is a known factor for the progression of premalignant lesions, such as actinic keratosis [6]. Murine studies have shown that nicotinamide is also able to protect against photocarcinogenesis [4,5]. Preliminary human studies suggest that nicotinamide may help prevent skin cancers and enhance the regression of actinic keratoses.

Cutaneous melanoma is a significant cause of morbidity and mortality. Nicotinamide is a safe, widely available vitamin that reduces the immune suppressive effects of UV, enhances DNA repair in keratinocytes and has shown promise in the chemoprevention of non‐melanoma skin cancer. Here, we report the effect of nicotinamide on DNA damage and repair in primary human melanocytes. Nicotinamide significantly enhanced the repair of oxidative DNA damage (8‐oxo‐7,8‐dihydro‐2′‐deoxyguanosine) and cyclobutane pyrimidine dimers induced by UV exposure. It also enhanced the repair of 8‐oxo‐7,8‐dihydro‐2′‐deoxyguanosine induced by the culture conditions in unirradiated melanocytes. A significant increase in the percentage of melanocytes undergoing unscheduled but not scheduled DNA synthesis was observed, confirming that nicotinamide enhances DNA repair in human melanocytes. In summary, nicotinamide, by enhancing DNA repair in melanocytes, is a potential agent for the chemoprevention of cutaneous melanoma.

Primary upper gastrointestinal tract melanoma is a rare but well recognised entity, with a poor prognosis because of delay in diagnosis. Furthermore, it may be difficult to determine whether a gastrointestinal melanoma represents a metastasis or a primary tumour. We report a 67-year-old man with a primary oesophageal melanoma, treated with surgical resection, who remains disease-free two years post resection.

Topical diphencyprone (DPCP) can be used to treat in transit and cutaneously metastastatic melanoma. To date, 50 patients have received DPCP therapy for at least 1 month at our institution, with complete clearance of cutaneous disease in 46% and partial response in a further 38% of patients. Topical immunotherapy with DPCP is inexpensive and well‐tolerated and should be considered in patients with skin metastases unsuitable for or refractory to other forms of therapy. J. Surg. Oncol. 2014 109:308–313.