Nicotinamide (vitamin B3) protects from ultraviolet (UV) radiation-induced carcinogenesis in mice and from UV-induced immunosuppression in mice and humans. Recent double-blinded randomized controlled Phase 2 studies in heavily sun-damaged individuals have shown that oral nicotinamide significantly reduces premalignant actinic keratoses, and may reduce new non-melanoma skin cancers. Nicotinamide is a precursor of nicotinamide adenine dinucleotide (NAD(+)), an essential coenzyme in adenosine triphosphate (ATP) production. Previously, we showed that nicotinamide prevents UV-induced ATP decline in HaCaT keratinocytes. Energy-dependent DNA repair is a key determinant of cellular survival after exposure to DNA-damaging agents such as UV radiation. Hence, in this study we investigated whether nicotinamide protection from cellular energy loss influences DNA repair. We treated HaCaT keratinocytes with nicotinamide and exposed them to low-dose solar-simulated UV (ssUV). Excision repair was quantified using an assay of unscheduled DNA synthesis. Nicotinamide increased both the proportion of cells undergoing excision repair and the repair rate in each cell. We then investigated ssUV-induced cyclobutane pyrimidine dimers (CPDs) and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8oxoG) formation and repair by comet assay in keratinocytes and with immunohistochemistry in human skin. Nicotinamide reduced CPDs and 8oxoG in both models and the reduction appeared to be due to enhancement of DNA repair. These results show that nicotinamide enhances two different pathways for repair of UV-induced photolesions, supporting nicotinamide's potential as an inexpensive, convenient and non-toxic agent for skin cancer chemoprevention.

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.

actinic keratoses basal cell carcinoma confidence interval least-squares squamous cell carcinoma Nicotinamide (vitamin B3) prevents photocarcinogenesis in mice (Gensler et al., 1999Gensler H.L. Williams T. Huang A.C. et al.Oral niacin prevents photocarcinogenesis and photoimmunosuppression in mice.Nutr Cancer. 1999; 34: 36-41Crossref PubMed Scopus (93) Google Scholar) and photoimmunosuppression in humans (Damian, 2010Damian D.L. Photoprotective effects of nicotinamide (invited review).Photochem Photobiol Sci. 2010; 9: 578-585Crossref PubMed Scopus (34) Google Scholar). Actinic keratoses (AKs) strongly predict non-melanoma skin cancer risk (Green and Battistutta, 1990Green A. Battistutta D. Incidence and determinants of skin-cancer in a high-risk Australian population.Int J Cancer. 1990; 46: 356-361Crossref PubMed Scopus (213) Google Scholar). These phase II studies aimed to determine whether oral nicotinamide, at different doses, reduced AKs in sun-damaged individuals. Healthy, immune-competent volunteers with ≥4 palpable AKs (face, scalp and upper limbs) were recruited from Royal Prince Alfred Hospital Dermatology Clinics, Sydney, Australia. The study protocols (ACTRN12609000490279; ACTRN12610000689077; http://www.anzctr.org.au) adhered to Helsinki Guidelines and were approved by the Sydney South West Area Health Service and University of Sydney ethics committees. All volunteers provided written informed consent. Participants were randomly assigned (1:1) to take nicotinamide 500mg (Nature's Own, Virginia, Queensland, Australia) or matched placebo (Australian Custom Pharmaceuticals, Sydney, New South Wales, Australia) twice daily (Study 1) or once daily (Study 2) for 4 months. The treatment allocation sequence was determined by a computer-generated randomization list prepared using a permuted blocks method (block size 6) by an investigator (DLD) not involved in AK assessment. Participants underwent complete skin examination before randomization, were encouraged to use daily sunscreen, and remained blinded throughout the study. At baseline, 2 and 4 months, palpable AKs were identified visually and by touch by a blinded observer (DS), counted and documented on a body grid chart. At baseline and 2 months, full blood count, creatinine, and liver function were assessed. A target of 36 patients was selected for Study 1 based on clinical judgement as this was our first pilot trial of oral nicotinamide. A conservative interpretation of the Study 1 results was used to inform the assumptions used in the sample size calculation for Study 2, where a sample size was selected to provide ≥80% power to detect a standardized effect size of 0.4 at the two-sided 5% level of significance, based on an analysis of covariance model given a correlation of 0.90 between baseline and follow-up assessments (Borm et al., 2007Borm G.F. Fransen J. Lemmens W.A.J.G. A simple sample size formula for analysis of covariance in randomized clinical trials.J Clin Epidemiol. 2007; 60: 1234-1238Abstract Full Text Full Text PDF PubMed Scopus (329) Google Scholar), allowing for 5% withdrawal. All randomized patients were eligible for inclusion in the efficacy analysis (intention to treat). The primary endpoint obtained for each patient was the AK count at 4 months. We also noted all histologically confirmed skin cancers during the study. The right-skewed distribution of the AK data was rectified by applying a loge transformation (with results back-transformed for reporting). The relative difference between groups on AK count was estimated using an analysis of covariance adjusting for baseline (Bonate, 2000Bonate P.L. Analysis of Pretest-Postest Designs. Chapman & Hall/CRC, Boca Raton, Florida, USA2000Crossref Google Scholar). Logistic and Poisson regression was used to compare treatment groups from both studies combined on skin cancer incidence with the number of previous cancers and study designation fitted as covariates. A total of 35 patients were enrolled in Study 1 (June–October 2009) (Table 1). One withdrew (nicotinamide) at 2 months because of invasive squamous cell carcinoma (SCC), but returned for his 4-month AK count. A total of 41 patients were enrolled in Study 2 (August–November 2010); two withdrew from treatment (placebo) soon after their baseline counts because of nursing-home placement, but agreed to follow up AK counts. Two nicotinamide participants withdrew from follow-up for personal reasons soon after enrolment; their baseline AK counts were carried forward and included in the primary analysis (Figures 1 and 2).Table 1Baseline characteristics and AKs during treatment with nicotinamide or placeboStudy 1 (500mg b.d.)Study 2 (500mg o.d.)PlaceboNicotinamidePlaceboNicotinamidePatients enrolled17182021Men:women10.715.314:614:7Mean age (years; range)72 (52–90)71 (59–82)72 (48–89)67 (52–80)Total AKs at baseline Mean (SD)31.5 (21.1)29.3 (23.5)40.3 (26.5)30.6 (16.3) Range (median)9–92 (23)6–89 (19)7–101 (37)12–73 (27)Total AKs at 2 months Mean (SD)28.2 (20.7)18.1 (16.8)35.5 (23.1)24.3 (14.6) Range (median)6–91 (20)3–65 (11)5–99 (34)4–60 (21) LS mean (95% CI)1Back-transformed estimates from an analysis of covariance performed on the loge(AK count) data at the time point indicated with treatment group included as a factor and the baseline loge(AK count) as a covariate. The absolute difference between the groups on loge(AK count) corresponds to the relative difference between the groups on AK count.20.9 (18.5-23.5)13.6 (12.1-15.3)26.1 (23.2–29.4)22.1 (19.7–24.8)Relative reduction (95% CI)1Back-transformed estimates from an analysis of covariance performed on the loge(AK count) data at the time point indicated with treatment group included as a factor and the baseline loge(AK count) as a covariate. The absolute difference between the groups on loge(AK count) corresponds to the relative difference between the groups on AK count.35% (23–45%)15% (0–28%) P-value<0.00010.046Total AKs at 4 months Mean (SD)27.1 (19.9)16.6 (13.9)34.8 (20.9)21.6 (14.7) Range (median)6–89 (20)2–54 (10)5–89 (32)3–60 (18) LS mean (95% CI)1Back-transformed estimates from an analysis of covariance performed on the loge(AK count) data at the time point indicated with treatment group included as a factor and the baseline loge(AK count) as a covariate. The absolute difference between the groups on loge(AK count) corresponds to the relative difference between the groups on AK count.19.9 (16.9–23.4)12.9 (11.0–15.2)25.9 (21.9–30.6)18.3 (15.6–21.6)Relative reduction (95% CI)1Back-transformed estimates from an analysis of covariance performed on the loge(AK count) data at the time point indicated with treatment group included as a factor and the baseline loge(AK count) as a covariate. The absolute difference between the groups on loge(AK count) corresponds to the relative difference between the groups on AK count.35% (18–48%)29% (11–44%) P-value2Very similar P-values were obtained in a sensitivity analysis when the groups were compared on percentage change from baseline at month 4 in AK count (statistical problems associated with using percentage change as an endpoint and rationale for statistical adjustment of baseline scores via analysis of covariance as the optimal analysis approach reviewed in Bonate (2000)).0.00060.005Abbreviations: AKs, actinic keratoses; CI, confidence interval; LS, least squares.Bold values indicate means and significant P-values.1 Back-transformed estimates from an analysis of covariance performed on the loge(AK count) data at the time point indicated with treatment group included as a factor and the baseline loge(AK count) as a covariate. The absolute difference between the groups on loge(AK count) corresponds to the relative difference between the groups on AK count.2 Very similar P-values were obtained in a sensitivity analysis when the groups were compared on percentage change from baseline at month 4 in AK count (statistical problems associated with using percentage change as an endpoint and rationale for statistical adjustment of baseline scores via analysis of covariance as the optimal analysis approach reviewed in Bonate, 2000Bonate P.L. Analysis of Pretest-Postest Designs. Chapman & Hall/CRC, Boca Raton, Florida, USA2000Crossref Google Scholar). Open table in a new tab Figure 2CONSORT 2010 flow diagram, study 2: nicotinamide 500mg daily versus placebo.View Large Image Figure ViewerDownload (PPT) Abbreviations: AKs, actinic keratoses; CI, confidence interval; LS, least squares. Bold values indicate means and significant P-values. AK counts at baseline and follow-up are shown in the Table 1. A 35% relative reduction in AK count at 4 months (95% confidence interval (CI): 18–48%; P=0.0006) was estimated from Study 1 (with similar results at 2 months). A 29% relative reduction in AK count at 4 months (95% CI: 11–44%; P=0.005) was estimated from Study 2 (with smaller but significant differences observed at 2 months). There was no evidence that the relative effect of nicotinamide was modified by baseline AK count (treatment-by-baseline interaction P-value was nonsignificant). For Studies 1 and 2 combined, 37 patients were randomized to placebo and 37 to nicotinamide. Eighty-one and 79% of placebo and nicotinamide patients, respectively, had previous, histologically confirmed skin cancers. During the 4-month trials, 11 placebo patients developed 20 new skin cancers (12 basal cell carcinoma (BCC) and 8 SCC) and 2 nicotinamide patients developed 4 cancers (2 BCC and 2 SCC). The odds of developing at least one skin cancer was significantly lower with nicotinamide (odds ratio=0.14; 95% CI: 0.03–0.73, P=0.019) as was the rate of new skin cancers (relative rate=0.24; 95% CI: 0.08–0.71, P=0.010) as estimated, respectively, by Logistic and Poisson regression models and adjusting for study and number of previous skin cancers. The treatment effect remained significant when analysis of skin cancer rates was repeated using a negative binomial model (P=0.038), although we note the unplanned nature of this combined analysis. Compliance, measured by counts of returned tablets, was 94–98%. One patient, who was also taking aspirin, described nausea while taking nicotinamide. No other potential side effects were reported and no clinically significant changes in blood profiles were observed. The mechanisms by which nicotinamide might prevent skin cancer or reduce progression of subclinical lesions are unclear. Nicotinamide is a substrate and inhibitor of the nuclear enzyme poly-ADP-ribose polymerase, which is centrally involved in DNA repair (Virag and Szabo, 2002Virag L. Szabo C. The therapeutic potential of poly(ADP-ribose) polymerase inhibitors.Pharmacol Rev. 2002; 54: 375-429Crossref PubMed Scopus (1223) Google Scholar). As a precursor of nicotinamide adenine dinucleotide, nicotinamide prevents the decline in cellular energy observed after UV exposure (Park et al., 2010Park J. Halliday G.M. Surjana D. et al.Nicotinamide prevents ultraviolet radiation-induced cellular energy loss.Photochem Photobiol. 2010; 86: 942-948Crossref PubMed Scopus (95) Google Scholar), and could therefore maintain efficient DNA repair. Immunosuppression has a key role in the malignant transformation of AKs (Frost and Green, 1994Frost C.A. Green A.C. Epidemiology of solar keratoses.Br J Dermatol. 1994; 131: 455-464Crossref PubMed Scopus (233) Google Scholar), and nicotinamide is highly immune protective in humans (Damian et al., 2008Damian D.L. Patterson C.R.S. Stapelberg M. et al.Ultraviolet radiation-induced immunosuppression is greater in men and prevented by topical nicotinamide.J Invest Dermatol. 2008; 128: 447-454Abstract Full Text Full Text PDF PubMed Scopus (170) Google Scholar). Hence, nicotinamide protection from photoimmunosuppression (Yiasemides et al., 2009Yiasemides E. Sivapirabu G. Halliday G.M. et al.Oral nicotinamide protects against ultraviolet radiation-induced immunosuppression in humans.Carcinogen. 2009; 30: 101-105Crossref PubMed Scopus (98) Google Scholar) may be a key mediator of the reduction in AKs observed here. Spontaneous fluctuation in AK counts has been previously reported (Criscione et al., 2009Criscione V.D. Weinstock M.A. Naylor M.F. et al.Actinic keratoses natural history and risk of malignant transformation in the Veterans Affairs Topical Tretinoin Chemoprevention Trial.Cancer. 2009; 115: 2523-2530Crossref PubMed Scopus (314) Google Scholar; Moloney et al., 2010Moloney F.J. Vestergaard M.E. Radojkovic B.L. et al.Randomised, double-blinded, placebo controlled study to assess the effect of topical 1% nicotinamide on actinic keratoses.Br J Dermatol. 2010; 162: 1138-1139Crossref PubMed Scopus (28) Google Scholar), consistent with the 13–15% reduction from baseline observed in our placebo groups. Our randomized, double-blinded design enabled detection of AK reductions with nicotinamide relative to any background variations in AKs due to seasonal and behavioral fluctuations in UV doses. Nicotinamide is well tolerated and costs $5–$10 per month at the doses used here. The results of these phase II studies suggest nicotinamide is effective in reducing AKs and shows promise for skin cancer chemoprevention. A longer phase III trial in a larger cohort, with new skin cancers as the primary endpoint, is now warranted. We are most thankful to our study participants, and gratefully acknowledge the funding of the Cancer Council New South Wales, Epiderm, and the Dermatology Research Foundation.

Nicotinamide (the amide form of vitamin B3) has been used in dermatology for more than 40 years for a diverse range of conditions including acne, rosacea, autoimmune bullous dermatoses, and now the treatment and prevention of photoaging and photoimmunosuppression. The broad clinical effects of nicotinamide may be explained by its role as a cellular energy precursor, a modulator of inflammatory cytokines, and an inhibitor of the nuclear enzyme poly(adenosine diphosphate-ribose) polymerase-1, which plays a significant role in DNA repair, maintenance ofgenomic stability, and cellular response to injury including inflammation and apoptosis. This review outlines the use of nicotinamide for inflammatory dermatoses and photoaging and focuses on its emerging role in photoprotection.

UV radiation is carcinogenic by causing mutations in the skin and also by suppressing cutaneous antitumor immunity. We previously found nicotinamide (vitamin B3) to be highly effective at reducing UV-induced immunosuppression in human volunteers, with microarray studies on in vivo irradiated human skin suggesting that nicotinamide normalizes subsets of apoptosis, immune function and energy metabolism-related genes that are downregulated by UV exposure. Using human adult low calcium temperature keratinocytes, we further investigated nicotinamide's effects on cellular energy metabolism. We found that nicotinamide prevented UV-induced cellular ATP loss and protected against UV-induced glycolytic blockade. To determine whether nicotinamide alters the effects of UV-induced oxidative stress posttranslationally, we also measured UV-induced reactive oxygen species (ROS). Nicotinamide had no effect on ROS formation, and at the low UV doses used in these studies, equivalent to ambient daily sun exposure, there was no evidence of apoptosis. Hence, nicotinamide appears to exert its UV protective effects on the skin via its role in cellular energy pathways.

Nicotinamide is a water-soluble amide form of niacin (nicotinic acid or vitamin B3). Both niacin and nicotinamide are widely available in plant and animal foods, and niacin can also be endogenously synthesized in the liver from dietary tryptophan. Nicotinamide is also commercially available in vitamin supplements and in a range of cosmetic, hair, and skin preparations. Nicotinamide is the primary precursor of nicotinamide adenine dinucleotide (NAD+), an essential coenzyme in ATP production and the sole substrate of the nuclear enzyme poly-ADP-ribose polymerase-1 (PARP-1). Numerous in vitro and in vivo studies have clearly shown that PARP-1 and NAD+ status influence cellular responses to genotoxicity which can lead to mutagenesis and cancer formation. This paper will examine the role of nicotinamide in the protection from carcinogenesis, DNA repair, and maintenance of genomic stability.