Fat intake and risk of squamous cell carcinoma of the skin

Dietary components and the risk of non-melanoma skin cancer: A systematic review of epidemiological studies

Non-melanoma skin cancer (NMSC) is the most common cancer among white-skinned people. The main environmental risk factor for all types of skin cancer is ultraviolet (UV) exposure to the sun. However, significant modifiable risk factors, such as diet, have been studied about NMSC risk. Several original studies have been conducted on the link between various dietary components and the risk of NMSC in the past decade, but have not been systematically reviewed. This review focuses on the potential impact of dietary components in the prevention of NMSC and evaluates the findings of epidemiologic evidence for dietary factors. We conducted a systematic search of three databases, including Scopus, ISI Web of Science, and PubMed, to identify relevant epidemiological studies published between 2000 and July 6, 2021. Finally, forty-three articles were included. Because of the inherent limitations of epidemiological studies, no definitive conclusions can be drawn; however, the links between folate, citrus, caffeine, and alcohol with BCC are notable; thus, high dietary folate intake, as well as citrus and alcohol consumption, are associated with an increased risk of basal cell carcinoma (BCC), whereas caffeine is associated with a lower risk. More research is required to reach a definitive conclusion.

Nutrition and nonmelanoma skin cancers

Nonmelanoma skin cancer (NMSC), the most widely diagnosed cancer in the United States, is rising in incidence despite public health and educational campaigns that highlight the importance of sun avoidance. It is,therefore, important to establish other modifiable risk factors that may be contributing to this increase. There is a growing body of evidence in the literature suggesting certain nutrients may have protective or harmful effects on NMSC. We review the current literature on nutrition and its effect on NMSC with a focus on dietary fat, vitamin A, nicotinamide, folate, vitamin C, vitamin D, vitamin E, polyphenols, and selenium.

Omega-3 fatty acid intake and decreased risk of skin cancer in organ transplant recipients

PURPOSE

Organ transplant recipients have over 100-fold higher risk of developing skin cancer than the general population and are in need of further preventive strategies. We assessed the possible preventive effects of omega-3 polyunsaturated fatty acid (PUFA) intake from food on the two main skin cancers, squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) in kidney and liver transplant recipients.

METHODS

Adult kidney or liver transplant recipients transplanted for at least 1 year and at high risk of skin cancer were recruited from the main transplant hospital in Queensland, 2012-2014 and followed until mid-2016. We estimated their dietary total long-chain omega-3 PUFAs and α-linolenic acid intakes at baseline using a food frequency questionnaire and ranked PUFA intakes as low, medium, or high. Relative risks (RRs_adj) of skin cancer adjusted for confounding factors with 95% confidence intervals (CIs) were calculated.

RESULTS

There were 449 transplant recipients (mean age, 55 years; 286 (64%) male). During follow-up, 149 (33%) patients developed SCC (median 2/person; range 1-40) and 134 (30%), BCC. Transplant recipients with high total long-chain omega-3 PUFA compared with low intakes showed substantially reduced SCC tumour risk (RR_adj 0.33, 95% CI 0.18-0.60), and those with high α-linolenic acid intakes experienced significantly fewer BCCs (RR_adj 0.40, 95% CI 0.22-0.74). No other significant associations were seen.

CONCLUSION

Among organ transplant recipients, relatively high intakes of long-chain omega-3 PUFAs and of α-linolenic acid may reduce risks of SCC and BCC, respectively.

The Potential Uses of Omega-3 Fatty Acids in Dermatology: A Review

BACKGROUND

A growing interest exists in the relationship between diet and skin disease, with many recent studies identifying a role for omega-3 fatty acids (O3FAs) in various dermatological conditions.

OBJECTIVE

Our objective was to identify the spectrum of uses for O3FA supplementation reported in literature and to evaluate the current level of evidence for its clinical application in skin disease prevention and management.

METHODS

A search was conducted using Ovid MEDLINE for primary literature that examined O3FA intake and skin health. A manual search of reference lists was performed to identify additional articles for inclusion.

RESULTS

A total of 38 studies met eligibility for review, reporting benefits for O3FA supplementation in the treatment of psoriasis, atopic dermatitis, acne, and skin ulcers. Additionally, a reduced incidence of skin cancer and a decrease in the severity of drug-associated mucocutaneous side effects were reported with O3FA supplementation.

CONCLUSION

This review yielded many well-studied benefits of O3FA uses in dermatology. Given its high safety profile, low cost, and ease of supplementation, O3FA is a reasonable supplement that may benefit patients wishing to improve inflammatory skin conditions through diet. Areas of particular clinical interest where supplementation may be valuable include O3FAs for systemic UV photoprotection, as well as adjuvant treatment for acne to reduce both inflammatory lesion count and the severity of mucocutaneous side effects associated with isotretinoin use.

Dietary Fat Intake and the Risk of Skin Cancer: A Systematic Review and Meta-Analysis of Observational Studies

We conducted a meta-analysis to evaluate the association between fat intake and the risk of three major types of skin cancer including basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and cutaneous malignant melanoma (CMM). A comprehensive search of PubMed and EMBASE was performed to identify all relevant observational studies published up to December 1, 2018. Specific odds ratio (OR) or relative risk (RR) estimates for the highest versus the lowest intake of dietary fat and 95% confidence intervals (CI) from the included studies were pooled using random effect model. Three prospective cohort studies (175,675 participants and 30,915 BCC cases, 4,106 SCC cases and 1,638 CMM cases) and nine case-control studies (328 BCC cases, 493 SCC cases, 1,547 CMM cases and 2,660 controls) were identified. The pooled results indicated that dietary consumption of total fat and saturated fat were not associated with three major types of skin cancer. High consumption of monounsaturated fat was significantly associated with a decreased risk of BCC (RR: 0.90, 95% CI: 0.85-0.96) and high level of polyunsaturated fat intake was potentially positively associated with SCC (RR: 1.19, 95% CI: 1.06-1.33). Our findings should be confirmed by further evidence from well-designed and large-scale prospective cohort studies.

Cosmetic and Therapeutic Applications of Fish Oil's Fatty Acids on the Skin

Fish oil has been broadly reported as a potential supplement to ameliorate the severity of some skin disorders such as photoaging, skin cancer, allergy, dermatitis, cutaneous wounds, and melanogenesis. There has been increasing interest in the relationship of fish oil with skin protection and homeostasis, especially with respect to the omega-3 polyunsaturated fatty acids (PUFAs), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA). The other PUFAs, such as α-linolenic acid (ALA) and linoleic acid (LA), also show a beneficial effect on the skin. The major mechanisms of PUFAs for attenuating cutaneous inflammation are the competition with the inflammatory arachidonic acid and the inhibition of proinflammatory eicosanoid production. On the other hand, PUFAs in fish oil can be the regulators that affect the synthesis and activity of cytokines for promoting wound healing. A systemic review was conducted to demonstrate the association between fish oil supplementation and the benefits to the skin. The following describes the different cosmetic and therapeutic approaches using fatty acids derived from fish oil, especially ALA, LA, DHA, and EPA. This review summarizes the cutaneous application of fish oil and the related fatty acids in the cell-based, animal-based, and clinical models. The research data relating to fish oil treatment of skin disorders suggest a way forward for generating advances in cosmetic and dermatological uses.

Fat Intake and Risk of Skin Cancer in U.S. Adults

Background: Fat intake has been associated with certain cancers, including colorectal, breast, and prostate cancers. However, literature on dietary fat and skin cancer has been limited.Methods: We examined the association between fat intake and risk of skin cancer including cutaneous malignant melanoma, squamous cell carcinoma (SCC), and basal cell carcinoma (BCC) within two prospective studies: the Nurses' Health Study (NHS) and the Health Professionals Follow-up Study (HPFS). Dietary information on total, saturated, monounsaturated, polyunsaturated, omega-6, and omega-3 fat and cholesterol was repeatedly assessed generally every 4 years. Incident cases were identified by self-report. Diagnosis on melanoma and SCC was confirmed by pathologic records.Results: A total of 794 melanoma, 2,223 SCC, and 17,556 BCC in the NHS (1984-2012) and 736 melanoma, 1,756 SCC, and 13,092 BCC in the HPFS (1986-2012) were documented. Higher polyunsaturated fat intake was associated with risk of SCC [pooled HR for highest vs. lowest quintiles, 1.16; 95% confidence interval (CI), 1.05-1.28; P_trend=0.001] and BCC (pooled HR, 1.06; 95% CI, 1.01-1.11; P_trend=0.01). Higher omega-6 fat intake was associated with risks of SCC, BCC, and melanoma. Omega-3 fat intake was associated with risk of BCC, but not with SCC or melanoma. No other fats were associated with melanoma risk. The associations were similar in women and men and by other skin cancer risk factors.Conclusions: Polyunsaturated fat intake was modestly associated with skin cancer risk.Impact: Further studies are needed to confirm our findings and to identify relevant biological mechanisms. Cancer Epidemiol Biomarkers Prev; 27(7); 776-82. ©2018 AACR.

Histology of Non-Melanoma Skin Cancers: An Update

Non-melanoma skin cancer (NMSC) is the most frequently diagnosed cancer in humans. Several different non-melanoma skin cancers have been reported in the literature, with several histologic variants that frequently cause important differential diagnoses with other cutaneous tumors basal cell carcinoma (BCC) is the most common malignant skin tumor, with different histologic variants that are associated with a greater or less aggressive behavior and that usually may be confused with other primitive skin tumors. Actinic keratosis, Bowen’s disease, keratoacanthoma, and invasive squamous cell carcinoma (SCC) correspond to the other line of NMSC, that may have only local tumoral behavior, easy to treat and with local management (as in the case of actinic keratosis (AK), Bowen’s disease, and keratoacanthoma) or a more aggressive behavior with a potential metastatic spread, as in case of invasive SCC. Therefore, histopathology serves as the gold standard during daily clinical practice, in order to improve the therapeutical approaches to patients with NMSC and to understand the distinct histopathological features of NMSC. Here, we reported the main pathological features of different non-melanoma skin cancers.

Potential Benefits of Omega-3 Fatty Acids in Non-Melanoma Skin Cancer

Considerable circumstantial evidence has accrued from both experimental animal and human clinical studies that support a role for omega-3 fatty acids (FA) in the prevention of non-melanoma skin cancer (NMSC). Direct evidence from animal studies has shown that omega-3 FA inhibit ultraviolet radiation (UVR) induced carcinogenic expression. In contrast, increasing levels of dietary omega-6 FA increase UVR carcinogenic expression, with respect to a shorter tumor latent period and increased tumor multiplicity. Both omega-6 and omega-3 FA are essential FA, necessary for normal growth and maintenance of health and although these two classes of FA exhibit only minor structural differences, these differences cause them to act significantly differently in the body. Omega-6 and omega-3 FA, metabolized through the lipoxygenase (LOX) and cyclooxygenase (COX) pathways, lead to differential metabolites that are influential in inflammatory and immune responses involved in carcinogenesis. Clinical studies have shown that omega-3 FA ingestion protects against UVR-induced genotoxicity, raises the UVR-mediated erythema threshold, reduces the level of pro-inflammatory and immunosuppressive prostaglandin E2 (PGE₂) in UVR-irradiated human skin, and appears to protect human skin from UVR-induced immune-suppression. Thus, there is considerable evidence that omega-3 FA supplementation might be beneficial in reducing the occurrence of NMSC, especially in those individuals who are at highest risk.

Diet in dermatology: Part I. Atopic dermatitis, acne, and nonmelanoma skin cancer

Patients commonly inquire about dietary modifications as a means to prevent or manage skin disease. Answering these questions is often challenging, given the vast and conflicting evidence that exists on this topic. This 2-part continuing medical education article summarizes the evidence to date to enable physicians to answer patients' questions in an evidence-based manner. Part I includes atopic dermatitis, acne, and nonmelanoma skin cancer. The role of dietary supplementation, dietary exclusion, food allergy, maternal diet, and breastfeeding in the development and/or prevention of atopic dermatitis is summarized. The dermatoendocrinologic mechanism for the effects of glycemic index/glycemic load and milk on acne is described, as well as related clinical evidence for dietary modifications. Finally, evidence and recommendations for restriction or supplementation of dietary factors in the prevention of nonmelanoma skin cancer, including fat, vitamins A, C, D, and E, and selenium, are reported.

Effect of the amount and type of dietary fat on cardiometabolic risk factors and risk of developing type 2 diabetes, cardiovascular diseases, and cancer: a systematic review

The effects of both the amount and quality of dietary fat have been studied intensively during the past decades. Previously, low-fat diets were recommended without much attention to the quality of fat, whereas there is general emphasis on the quality of fat in current guidelines. The objective of this systematic review (SR) was to assess the evidence of an effect of the amount and type of dietary fat on body weight (BW), risk factors, and risk of non-communicable diseases, that is, type 2 diabetes (T2DM), cardiovascular diseases (CVD), and cancer in healthy subjects or subjects at risk for these diseases. This work was performed in the process of updating the fourth edition of the Nordic Nutrition Recommendations from 2004. The literature search was performed in October 2010 covering articles published since January 2000. A complementary search was done in February 2012 covering literature until December 2011. Two authors independently selected articles for inclusion from a total of about 16,000 abstracts according to predefined criteria. Randomized controlled trials (RCT) and prospective cohort studies (PCS) were included as well as nested case-control studies. A few retrospective case-control studies were also included when limited or no data were available from other study types. Altogether 607 articles were quality graded and the observed effects in these papers were summarized. Convincing evidence was found that partial replacement of saturated fat (SFA) with polyunsaturated fat (PUFA) or monounsaturated fat (MUFA) lowers fasting serum/plasma total and LDL cholesterol concentrations. The evidence was probable for a decreasing effect of fish oil on concentration of serum/plasma total triglycerides as compared with MUFA. Beneficial effect of MUFA both on insulin sensitivity and fasting plasma/serum insulin concentration was considered as probable in comparisons of MUFA and carbohydrates versus SFA, whereas no effect was found on fasting glucose concentration in these comparisons. There was probable evidence for a moderate direct association between total fat intake and BW. Furthermore, there was convincing evidence that partial replacement of SFA with PUFA decreases the risk of CVD, especially in men. This finding was supported by an association with biomarkers of PUFA intake; the evidence of a beneficial effect of dietary total PUFA, n-6 PUFA, and linoleic acid (LA) on CVD mortality was limited suggestive. Evidence for a direct association between total fat intake and risk of T2DM was inconclusive, whereas there was limited-suggestive evidence from biomarker studies that LA is inversely associated with the risk of T2DM. However, there was limited-suggestive evidence in biomarker studies that odd-chain SFA found in milk fat and fish may be inversely related to T2DM, but these associations have not been supported by controlled studies. The evidence for an association between dietary n-3 PUFA and T2DM was inconclusive. Evidence for effects of fat on major types of cancer was inconclusive regarding both the amount and quality of dietary fat, except for prostate cancer where there was limited-suggestive evidence for an inverse association with intake of ALA and for ovarian cancer for which there was limited-suggestive evidence for a positive association with intake of SFA. This SR reviewed a large number of studies focusing on several different health outcomes. The time period covered by the search may not have allowed obtaining the full picture of the evidence in all areas covered by this SR. However, several SRs and meta-analyses that covered studies published before year 2000 were evaluated, which adds confidence to the results. Many of the investigated questions remain unresolved, mainly because of few studies on certain outcomes, conflicting results from studies, and lack of high quality-controlled studies. There is thus an evident need of highly controlled RCT and PCS with sufficient number of subjects and long enough duration, specifically regarding the effects of the amount and quality of dietary fat on insulin sensitivity, T2DM, low-grade inflammation, and blood pressure. New metabolic and other potential risk markers and utilization of new methodology in the area of lipid metabolism may provide new insight.

Can diet prevent nonmelanoma skin cancer progression?

Nonmelanoma skin cancer is the most prevalent malignant disease among light-skinned individuals in the USA, accounting for approximately 1 million new cases annually. Solar ultraviolet radiation is known to be the major cause of skin cancer. The idea that diet, particularly dietary fat, may play a role in modulating cancer incidence has been based largely upon indirect epidemiologic evidence. However, few studies have found correlations of dietary fat intake with skin cancer incidence. Nevertheless, a large body of evidence with experimental animals and one clinical intervention trial, the latter avoiding the pitfalls of many epidemiologic investigations, clearly demonstrate that the level of dietary fat intake can have a significant influence on the occurrence of skin cancer in individuals at high risk.

Consumption of omega-3 fatty acids and the risk of skin cancers: a systematic review and meta-analysis

Skin cancers have a higher incidence than all other cancers combined and are a major cause of morbidity worldwide. Laboratory data suggest certain dietary constituents, notably omega-3 polyunsaturated fatty acids (n-3 PUFAs), could potentially protect against skin malignancy, although no large-scale review has been conducted in humans. The objective of this review and meta-analysis was to determine the relationship between dietary n-3 PUFAs and skin cancer incidence. It considered all published randomized controlled trials and observational studies up to March 2013. Five studies (two case-control and three cohort) were identified pertaining to oral n-3 PUFA consumption and incidence of basal cell carcinoma (BCC), squamous cell carcinoma (SCC), melanoma (or a combination) and were included in a random-effects meta-analysis. A further six studies considering nondietary n-3 PUFA exposure (e.g., by tissue analysis) and/or recognized biological markers of skin cancer risk (e.g., p53 expression) were analyzed qualitatively. Dietary n-3 PUFAs were not associated with BCC (pooled OR 1.05, 95% CIs 0.86-1.28). Consumption of high levels of n-3 PUFAs were inversely associated with melanoma, although with only one estimate available (OR 0.52, 95% CI 0.34-0.78), and SCC, although nonsignificantly (pooled OR 0.86, 95% CIs 0.59-1.23). Available evidence is suggestive, but currently inadequate, to support the hypothesis that n-3 PUFAs protect against skin malignancy.

Impact of EPA ingestion on COX- and LOX-mediated eicosanoid synthesis in skin with and without a pro-inflammatory UVR challenge--report of a randomised controlled study in humans

Scope

Eicosapentaenoic acid (EPA), abundant in oily fish, is reported to reduce skin inflammation and provide photoprotection, potential mechanisms include competition with arachidonic acid (AA) for metabolism by cyclooxygenases/lipoxygenases to less pro-inflammatory mediators. We thus examine impact of EPA intake on levels of AA, EPA and their resulting eicosanoids in human skin with or without ultraviolet radiation (UVR) challenge.

Methods and results

In a double-blind randomised controlled study, 79 females took 5 g EPA-rich or control lipid for 12 wk. Pre- and post-supplementation, red blood cell and skin polyunsaturated fatty acids were assessed by GC, and eicosanoids from unexposed and UVR-exposed skin by LC-MS/MS. Active supplementation increased red blood cell and dermal EPA versus control (both p < 0.001), lowering relative AA:EPA content (4:1 versus 15:1 and 5:1 versus 11:1, respectively; both p < 0.001). Pre-supplementation, UVR increased PGE₂, 12-hydroxyeicosatetraenoic acids, 12-HEPE (all p < 0.001) and PGE₃ (p < 0.05). Post-EPA, PGE₂ was reduced in unchallenged skin (p < 0.05) while EPA-derived PGE₃ (non-sign) and 12-HEPE (p < 0.01) were elevated post-UVR. Thus, post-EPA, PGE₂:PGE₃ was lower in unchallenged (12:1 versus 28:1; p < 0.05) and UVR exposed (12:1 versus 54:1; p < 0.01) skin; 12-hydroxyeicosatetraenoic acids:12-HEPE was lower in UVR-exposed skin (3:1 versus 11:1; p < 0.001).

Conclusion

Dietary EPA augments skin EPA:AA content, shifting eicosanoid synthesis towards less pro-inflammatory species, and promoting a regulatory milieu under basal conditions and in response to inflammatory insult.

Plasma omega-3 and omega-6 concentrations and risk of cutaneous basal and squamous cell carcinomas in Australian adults

Laboratory-based evidence suggests that omega-3 and omega-6 polyunsaturated fatty acids may affect skin photocarcinogenesis, but epidemiologic evidence is inconsistent. In 1,191 White Australian adults, we prospectively investigated associations between baseline plasma concentrations of omega-3 and omega-6 fatty acids and cutaneous basal cell carcinomas (BCC) and squamous cell carcinomas (SCC). Relative risks (RR) and 95% confidence intervals (CI) were estimated on the basis of number of histologically confirmed tumors diagnosed during follow-up (1997-2007). Plasma eicosapentaenoic acid (EPA) concentrations and omega-3/-6 ratio showed significant inverse associations with SCC tumors, comparing higher tertiles with the lowest, in age- and sex-adjusted models (Ptrend = 0.02 and 0.03, respectively) which weakened after adjustment for past sun exposure. Associations between EPA and SCC were stronger among participants with a history of skin cancer at baseline (n = 378; highest vs. lowest tertile: RR = 0.50; 95% CI, 0.28-0.92; Ptrend = 0.01). Total omega-6 was inversely associated with BCC tumors in multivariate models (P = 0.04; highest vs. lowest tertile: RR = 0.71; 95% CI, 0.51-0.99), and more strongly in the subgroup with past skin cancer. Linoleic and linolenic acids were also inversely associated with BCC occurrence in this subgroup. When fatty acids were analyzed as continuous variables, however, there was no evidence of any linear or nonlinear associations. This study provides some support for reduced skin cancer risk with high plasma concentrations of omega-3 and omega-6 fatty acids, but results depended on how fatty acid data were modeled. Further investigation of these associations in larger datasets is needed.

Randomized controlled trial of oral omega-3 PUFA in solar-simulated radiation-induced suppression of human cutaneous immune responses

BACKGROUND

Skin cancer is a major public health concern, and the majority of cases are caused by solar ultraviolet radiation (UVR) exposure, which suppresses skin immunity. Omega-3 (n-3) PUFAs protect against photoimmunosuppression and skin cancer in mice, but the impact in humans is unknown.

OBJECTIVES

We hypothesized that EPA-rich n-3 PUFA would abrogate photoimmunosuppression in humans. Therefore, a nutritional study was performed to assess the effect on UVR suppression of cutaneous cell-mediated immunity (CMI) reflected by nickel contact hypersensitivity (CHS).

DESIGN

In a double-blind, randomized controlled study, 79 volunteers (nickel-allergic women, 22-60 y old, with phototype I or II) took 5 g n-3 PUFA-containing lipid (70% EPA plus 10% DHA) or a control lipid daily for 3 mo. After supplementation, nickel was applied to 3 skin sites preexposed on 3 consecutive days to 1.9, 3.8, or 7.6 J/cm(2) of solar-simulated radiation (SSR) and to 3 unexposed control sites. Nickel CHS responses were quantified after 72 h and the percentage of immunosuppression by SSR was calculated. Erythrocyte [red blood cell (RBC)] EPA was measured by using gas chromatography.

RESULTS

SSR dose-related suppression of the nickel CHS response was observed in both groups. Photoimmunosuppression appeared less in the n-3 PUFA group than in the control group (not statistically significant [mean difference (95% CI): 6.9% (-2.1%, 15.9%)]). The difference was greatest at 3.8 J/cm(2) SSR [mean difference: 11% (95% CI: 0.5%, 21.4%)]. Postsupplementation RBC EPA was 4-fold higher in the n-3 PUFA group than in the control group (mean difference: 2.69% (95% CI: 2.23%, 3.14%), which confirmed the EPA bioavailability.

CONCLUSION

Oral n-3 PUFAs appear to abrogate photoimmunosuppression in human skin, providing additional support for their chemopreventive role; verification of study findings is required. This trial was registered at clinicaltrials.gov as NCT01032343.

Arachidonic acid and cancer risk: a systematic review of observational studies

Background

An n-6 essential fatty acid, arachidonic acid (ARA) is converted into prostaglandin E₂, which is involved in tumour extension. However, it is unclear whether dietary ARA intake leads to cancer in humans. We thus systematically evaluated available observational studies on the relationship between ARA exposure and the risk of colorectal, skin, breast, prostate, lung, and stomach cancers.

Methods

We searched the PubMed database for articles published up to May 17, 2010. 126 potentially relevant articles from the initial search and 49,670 bibliographies were scrutinised to identify eligible publications by using predefined inclusion criteria. A comprehensive literature search yielded 52 eligible articles, and their reporting quality and methodological quality was assessed. Information on the strength of the association between ARA exposure and cancer risk, the dose-response relationship, and methodological limitations was collected and evaluated with respect to consistency and study design.

Results

For colorectal, skin, breast, and prostate cancer, 17, 3, 18, and 16 studies, respectively, were identified. We could not obtain eligible reports for lung and stomach cancer. Studies used cohort (n = 4), nested case-control (n = 12), case-control (n = 26), and cross-sectional (n = 12) designs. The number of subjects (n = 15 - 88,795), ARA exposure assessment method (dietary intake or biomarker), cancer diagnosis and patient recruitment procedure (histological diagnosis, cancer registries, or self-reported information) varied among studies. The relationship between ARA exposure and colorectal cancer was inconsistent based on ARA exposure assessment methodology (dietary intake or biomarker). Conversely, there was no strong positive association or dose-response relationship for breast or prostate cancer. There were limited numbers of studies on skin cancer to draw any conclusions from the results.

Conclusions

The available epidemiologic evidence is weak because of the limited number of studies and their methodological limitations, but nonetheless, the results suggest that ARA exposure is not associated with increased breast and prostate cancer risk. Further evidence from well-designed observational studies is required to confirm or refute the association between ARA exposure and risk of cancer.

Intake of omega-3 and omega-6 fatty acids and risk of basal and squamous cell carcinomas of the skin: a longitudinal community-based study in Australian adults

Intake of omega-3 and omega-6 fatty acids may modify the risk of basal and squamous cell carcinoma of the skin (BCC and SCC), but population-based evidence is limited and inconsistent. We examined prospectively associations between intake of omega-3 and omega-6 fatty acids estimated from food frequency questionnaires and BCC and SCC incidence among 1322 randomly selected adults in Nambour, Australia. Relative risks (RR) and 95% confidence intervals (CI) were estimated based on histologically confirmed tumors diagnosed between 1997 and 2007. Incidence of BCC was lowest in the middle third of both total omega-6 intake (RR(mv.adj) = 0.74, 95% CI = 0.56-0.97) and linoleic acid intake (RR(mv.adj) = 0.75, 95% CI = 0.57-0.99) compared with the lowest third of intake. Evidence for associations with SCC was weak, though persons with arachidonic acid intake in the middle third had a marginally increased risk of SCC (RR(mv.adj) = 1.42, 95% CI = 1.00-2.02). Consumption of omega-3 fatty acids was not associated with subsequent skin cancer risk. Suggestion that intake of arachidonic acid may be associated with increased SCC incidence and total omega-6 with reduced BCC from our study is still highly uncertain and may be due to chance. These data do not support an association between these fatty acids and risk of BCC or SCC.

Three-way assessment of long-chain n-3 PUFA nutrition: by questionnaire and matched blood and skin samples

The long-chain n-3 PUFA, EPA, is believed to be important for skin health, including roles in the modulation of inflammation and protection from photodamage. FFQ and blood levels are used as non-invasive proxies for assessing skin PUFA levels, but studies examining how well these proxies reflect target organ content are lacking. In seventy-eight healthy women (mean age 42·8, range 21-60 years) residing in Greater Manchester, we performed a quantitative analysis of long-chain n-3 PUFA nutrition estimated from a self-reported FFQ (n 75) and correlated this with n-3 PUFA concentrations in erythrocytes (n 72) and dermis (n 39). Linear associations between the three n-3 PUFA measurements were assessed by Spearman correlation coefficients and agreement between these measurements was estimated. Average total dietary content of the principal long-chain n-3 PUFA EPA and DHA was 171 (SD 168) and 236 (SD 248) mg/d, respectively. EPA showed significant correlations between FFQ assessments and both erythrocyte (r 0·57, P< 0·0001) and dermal (r 0·33, P= 0·05) levels, as well as between erythrocytes and dermis (r 0·45, P= 0·008). FFQ intake of DHA and the sum of n-3 PUFA also correlated well with erythrocyte concentrations (r 0·50, P< 0·0001; r 0·27, P= 0·03). Agreement between ranked thirds of dietary intake, blood and dermis approached 50% for EPA and DHA, though gross misclassification was lower for EPA. Thus, FFQ estimates and circulating levels of the dietary long-chain n-3 PUFA, EPA, may be utilised as well-correlated measures of its dermal bioavailability.

Omega-3 polyunsaturated fatty acids: photoprotective macronutrients

Ultraviolet radiation (UVR) in sunlight has deleterious effects on skin, while behavioural changes have resulted in people gaining more sun exposure. The clinical impact includes a year-on-year increase in skin cancer incidence, and topical sunscreens alone provide an inadequate measure to combat overexposure to UVR. Novel methods of photoprotection are being targeted as additional measures, with growing interest in the potential for systemic photoprotection through naturally sourced nutrients. Omega-3 polyunsaturated fatty acids (n-3 PUFA) are promising candidates, showing potential to protect the skin from UVR injury through a range of mechanisms. In this review, we discuss the biological actions of n-3 PUFA in the context of skin protection from acute and chronic UVR overexposure and describe how emerging new technologies such as nutrigenomics and lipidomics assist our understanding of the contribution of such nutrients to skin health.

Nutrition and nonmelanoma skin cancers

The incidence of nonmelanoma skin cancer is increasing every year. Basal cell carcinoma and squamous cell carcinoma are the two major types of nonmelanoma skin cancer. Among other factors, understanding the potential role of nutrients in the development, progression, and treatment of nonmelanoma skin cancer is critical. This contribution provides a review of the nutrients that have been more extensively investigated in the literature with regard to nonmelanoma skin cancer, including dietary fats, retinol, carotenoids, vitamin C, vitamin D, vitamin E, selenium, copper, iron, zinc, green tea, and black tea.

Docosahexaenoic acid reverts resistance to UV-induced apoptosis in human keratinocytes: involvement of COX-2 and HuR

The dramatic increase in the incidence of nonmelanoma skin cancer over the last decades has been related to the augmented exposure to ultraviolet (UV) radiation (UVR). It is known that apoptosis is induced as a protective mechanism after the acute irradiation of keratinocytes, whereas apoptotic resistance and carcinogenesis may follow the chronic exposure to UVR. We found that not all the human keratinocytes lines studied underwent apoptosis following acute exposure to UVR (10-60 mJ/cm(2)). Whereas UVR induced apoptosis in the HaCaT cells, NCTC 2544 and nr-HaCaT cells showed apoptosis resistance. The cytokeratin pattern of the apoptosis-resistant cells indicated that they possessed a degree of differentiation lower than that of HaCaT cells. They also showed an enhanced expression of cyclooxygenase-2 (COX-2), an early marker of carcinogenesis in various tissues, including skin. n-3 polyunsaturated fatty acids have drawn increasing interest as nutritional factors with the potential to reduce UVR carcinogenesis, and since they are apoptosis inducers and COX-2 inhibitors in cancer cells, we investigated the ability of n-3 polyunsaturated fatty acids to influence the resistance to UVR-induced apoptosis in keratinocytes. We observed that docosahexaenoic acid (DHA) reverted the resistance of nr-HaCaT cells to UVR-induced apoptosis, increasing the Bax/Bcl-2 ratio and caspase-3 activity, and reduced COX-2 levels by inhibiting the expression of the human antigen R (HuR), a known COX-2 mRNA stabilizer in keratinocytes. The transfection of nr-HaCaT cells with HuR siRNA mimicked the proapoptotic effect of DHA. Overall, our findings further support the role of DHA as a suitable anticarcinogenic factor against nonmelanoma skin cancers.

Nutritional approach to sun protection: a suggested complement to external strategies

The increasing incidence of skin cancer despite the use of externally applied sun protection strategies, alongside research showing that nutrients reduce photo-oxidative damage, suggest nutritional approaches could play a beneficial role in skin cancer prevention. Penetrating photo-oxidative ultraviolet A radiation reduces skin and blood antioxidants and damages cell components, including DNA. Dietary antioxidant vitamins, minerals, and phytochemicals in addition to n-3 polyunsaturated fatty acids, n-9 monounsaturated fatty acids, and low pro-inflammatory n-6 polyunsaturated fatty acids, have demonstrated protective properties. The presence of these elements in the traditional Greek-style Mediterranean diet may have contributed to the low rates of melanoma in the Mediterranean region despite high levels of solar radiation. This suggests a potentially relevant model for studying dietary/nutritional supplementation for lifelong internal support of sun-protection mechanisms, which could complement external strategies.

Cytotoxicity of unsaturated fatty acids in fresh human tumor explants: concentration thresholds and implications for clinical efficacy

Background

Unsaturated fatty acids (UFAs) exhibit in vitro cytotoxicity against many malignant cell lines and yield decreased cancer incidence and reduced tumor growth in animal models. But clinical and animal studies to date have achieved response using only localized delivery methods such as intratumoral infusion. To explore possibilities for enhanced clinical efficacy, fresh surgical explants of tumors from 22 patients with five malignancies were exposed to γ-linolenic acid (GLA) and α-linolenic acid (ALA) and analyzed with an in vitro chemosensitivity testing system, the Fluorescent Cytoprint Assay (FCA). A total of 282 micro-organ cultures derived from these malignant tumors were exposed to GLA and ALA at different concentrations.

Results

GLA and ALA exhibited greater than 90% cytotoxicity at a sharp concentration threshold between 500 μM and 1 mM against all but two malignant micro-organ cultures tested in 5-10% serum. In tests using 30-40% serum, GLA and ALA killed tumor at concentrations of 2 mM and above.

Conclusions

The concentration threshold of 500 μM to 2 mM exhibited for antitumor activity by GLA and ALA is much higher than that observed in most previously reported cell culture studies but consistent with physiological concentrations found to kill tumor clinically and in animals. A mechanism of antitumor activity by unsaturated fatty acids through selective destabilization of the malignant plasma membrane is considered. An oral regimen is proposed for phase I clinical testing that could push the area under the curve for serum concentration of unbound unsaturated fatty acids over time to much higher levels than previously achieved for systemic administration and into the range that could yield antitumor response.

Dietary fat intake and risk of skin cancer: a prospective study in Australian adults

Although intakes of dietary fat have been associated with both basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) of the skin, the evidence is sparse and inconsistent. This study prospectively investigated the association between total dietary fat; saturated, polyunsaturated and monounsaturated fatty acids; and percent energy from fat in relation to BCC and SCC of the skin. At baseline in 1992, total fat intake and intake of fatty acids were assessed in an Australian community-based longitudinal study, using a validated semi-quantitative food frequency questionnaire in 1,057 adult residents (aged 25-75 years) in Nambour, Queensland. Information on demography, sun-sensitivity history and sun exposure factors were obtained using self-administered questionnaires. Associations with BCC and SCC in terms of persons newly affected and of tumor counts were assessed using Poisson and negative binomial regression models, respectively, based on incident, histologically-confirmed tumors occurring between 1992 and 2002. No significant linear trends were observed in overall risk of BCC or SCC of the skin with increasing total fat intake. However, in participants with a history of skin cancer, total fat intake (multivariable adjusted RR = 2.42, 95% CI = 1.20-4.88; p for trend = 0.01) was associated with increased numbers of SCC tumors comparing the highest to lowest tertile. In conclusion, SCC tumor risk increased as total fat intake increased in people with a history of skin cancer. Dietary fats were not associated with BCC occurrence.

Inhibitory effect of polyunsaturated fatty acids on MMP-9 release from microglial cells--implications for complementary multiple sclerosis treatment

We investigated whether polyunsaturated fatty acids (PUFA), which might be a useful complementary therapy among patients with multiple sclerosis (MS), are able to modulate matrix metalloproteinase (MMP) production in microglial cultures. MMPs are myelinotoxic factors. Primary cultures of rat microglia were treated with different doses of omega-3 (omega-3) PUFA or purified fish oil, containing a mixture of omega-3 and omega-6 PUFA, and simultaneously activated by exposure to lipopolysaccharide (LPS). Culture supernatants were subjected to zymography and Western blot analysis for the assessment of MMP-2 and MMP-9 levels. Increased amounts of MMP-9, but not of the constitutively expressed MMP-2, were observed in supernatants from LPS-treated microglia in comparison with non-treated control cells. The treatment with both omega-3 PUFA and fish oil dose-dependently inhibited the LPS-induced production of MMP-9. Our results suggest that a low fat diet supplemented with omega-3 PUFA may become recommended for the well being of MS patients under therapy.

Nutrient intake and risk of squamous cell carcinoma of the esophagus: a case-control study in Uruguay

In 1996-2004 a case-control study on nutrient intake, dietary constituents and risk of squamous cell carcinoma of the esophagus was conducted in Montevideo, Uruguay. In fact, Uruguay, and especially its northern provinces, which border Brazil, are high-risk areas. The study included 234 cases and 936 controls. The controls were hospitalized patients with non-neoplastic disease, which was not related to tobacco smoking and alcohol drinking, and without recent changes in their diets. Controls were frequency matched to cases on age (10-yr intervals), sex, and residence (Montevideo and other provinces). Dietary constituents were energy adjusted using the residuals method and then categorized in quartiles according to the distribution of the controls. The final model included linoleic acid, lycopene, alpha-carotene, beta-cryptoxanthin, vitamin A, monounsaturated fat, total carbohydrates, beta-carotene, and folate. The odds ratio (OR) for high intake of linoleic acid was 1.4 (95% confidence interval, CI = 1.2-1.6), whereas lycopene displayed a strong protective effect (OR = 0.7; 95% CI = 0.6-0.9). The possible role of these and other dietary constituents in esophageal carcinogenesis is discussed.

Dietary pattern in association with squamous cell carcinoma of the skin: a prospective study

BACKGROUND

The role of diet in the development of skin cancer is inconclusive, and the effect of the combined consumption of foods has never been reported.

OBJECTIVE

We prospectively investigated the association between dietary patterns and cutaneous basal cell (BCC) and squamous cell (SCC) carcinoma.

DESIGN

Principal components analysis of 38 food groups was used to identify dietary patterns in 1360 adults aged 25-75 y who participated in a community-based skin cancer study in Nambour, Australia, between 1992 and 2002. We obtained baseline information about diet, skin color, and sun exposure factors. Multivariate-adjusted relative risks (RRs) for BCC and SCC tumors were estimated by using negative binomial regression modeling.

RESULTS

Two major dietary patterns were identified: a meat and fat pattern and a vegetable and fruit pattern. The meat and fat pattern was positively associated with development of SCC tumors (RR=1.83; 95% CI: 1.00, 3.37; P for trend=0.05) after adjustment for confounders and even more strongly associated in participants with a skin cancer history (RR=3.77; 95% CI: 1.65, 8.63; P for trend = 0.002) when the third and first tertiles were compared. A higher consumption of the vegetable and fruit dietary pattern appeared to decrease SCC tumor risk by 54% (P for trend = 0.02), but this protective effect was mostly explained by the association with green leafy vegetables. There was no association between the dietary patterns and BCC tumors.

CONCLUSION

A dietary pattern characterized by high meat and fat intakes increases SCC tumor risk, particularly in persons with a skin cancer history.

Stimulatory effect of voluntary exercise or fat removal (partial lipectomy) on apoptosis in the skin of UVB light-irradiated mice

Earlier studies indicated that high dietary fat and obesity are associated with an increased risk of cancer at several organ sites in experimental animals and in humans. In a recent study we found that voluntary running wheel exercise decreased body fat and inhibited ultraviolet B light (UVB)-induced carcinogenesis in the epidermis of SKH-1 mice. In the present study we demonstrate that voluntary running wheel exercise stimulated UVB-induced apoptosis in the epidermis by a p53-independent mechanism, and voluntary exercise also stimulated apoptosis in UVB-induced tumors in tumor-bearing mice. Exercise had no effect in non-UVB-treated epidermis or in areas of the epidermis away from tumors in tumor-bearing mice. In addition, we found that removal of the parametrial fat pads (partial lipectomy) 2 weeks before UVB irradiation enhanced UVB-induced apoptosis. The results of our studies suggest that fat cells secrete substances that inhibit apoptosis in cells with DNA damage and possibly also in tumors. Our results help explain why exercise or various dietary regimens that decrease tissue fat inhibit carcinogenesis.

The potential of omega-3 fatty acids in the prevention of non-melanoma skin cancer

In toto, there is strong circumstantial evidence from both experimental and clinical studies to support a role for omega-3 FA in the prevention of non-melanoma skin cancer (NMSC). In experimental animal studies there is direct evidence that dietary omega-3 FA inhibits ultraviolet radiation (UVR) carcinogenic expression, with regard to both increased tumor latent period and reduced tumor multiplicity. Equivalent levels of omega-6 FA increase UVR carcinogenic expression. Dietary omega-3 FA dramatically reduces the plasma and cutaneous pro-inflammatory and immunosuppressive PGE(2) levels in mice. Dietary omega-6 FA increases prostaglandin E synthase type 2 (PGE(2)) level. Dietary omega-3 FA significantly reduces the inflammatory response and sustains, or enhances, the delayed type hypersensitivity immune response in mice when compared to an equivalent dietary level of omega-6 FA. Supplementary omega-3 FA significantly increases the UVR-mediated erythema threshold in humans. Supplementary omega-3 FA significantly reduces the level of pro-inflammatory and immunosuppressive PGE(2) levels in Ultraviolet B-irradiated human skin.

Association between dietary fat and skin cancer in an Australian population using case-control and cohort study designs

BACKGROUND

Human studies of dietary fat as a possible risk factor for cutaneous malignant melanoma (CMM) and non-melanoma skin cancer (NMSC)--principally basal cell carcinoma (BCC) and squamous cell carcinoma (SCC)--have produced inconsistent results. We had the opportunity to examine the association concurrently for all three types of skin cancer in a population-based study in Tasmania, Australia, involving 652 cases of CMM, BCC and SCC and a common set of 471 controls.

METHODS

Histopathologically-confirmed cases of CMM, BCC and SCC were ascertained from the Tasmanian Cancer Registry (TCR), and controls were selected at random from the state's electoral roll. We compared subjects categorised by thirds of dietary fat intake score measured by the 'Dobson short fat questionnaire', with logistic regression models that adjusted for age, sex, skin type and usual sun exposure. We then followed all subjects for 56-80 months until 31 August, 2004 for a new NMSC using record linkage with both the TCR and the Births, Deaths, and Marriages registry. Incidence rates were calculated and ratios of rates were estimated using Poisson models.

RESULTS

Relative to subjects in the lowest fat intake category, the odds ratios (OR) comparing cases and controls were OR = 0.76 (95% CI: 0.56-1.03) for medium fat intake, and OR = 0.62 (95% CI: 0.45-0.85) for high fat intake, with a significant (p < 0.01) trend of reduced odds ratio with higher category dietary fat intake. Among cases, the incidence rate ratio (IRR) relative to those with lowest fat score was IRR = 0.72 (95% CI: 0.50-1.03) for medium fat intake, and IRR = 0.82 (95% CI: 0.56-1.20) for highest fat intake (linear trend p = 0.30).

CONCLUSION

Using the same dietary instrument with two study designs in the same Caucasian population, we found no evidence that high fat intake increases the risk of developing melanoma or non-melanoma skin cancers. Instead, our results suggest a risk reduction for high fat intake.

Role of dietary factors in the development of basal cell cancer and squamous cell cancer of the skin

The role of dietary factors in the development of skin cancer has been investigated for many years; however, the results of epidemiologic studies have not been systematically reviewed. This article reviews human studies of basal cell cancer (BCC) and squamous cell cancer (SCC) and includes all studies identified in the published scientific literature investigating dietary exposure to fats, retinol, carotenoids, vitamin E, vitamin C, and selenium. A total of 26 studies were critically reviewed according to study design and quality of the epidemiologic evidence. Overall, the evidence suggests a positive relationship between fat intake and BCC and SCC, an inconsistent association for retinol, and little relation between beta-carotene and BCC or SCC development. There is insufficient evidence on which to make a judgment about an association of other carotenoids with skin cancer. The evidence for associations between vitamin E, vitamin C, and selenium and both BCC and SCC is weak. Many of the existing studies contain limitations, however, and further well-designed and implemented studies are required to clarify the role of diet in skin cancer. Additionally, the role of other dietary factors, such as flavonoids and other polyphenols, which have been implicated in skin cancer development in animal models, needs to be investigated.

Nutritional Intervention With Omega-3 Fatty Acids in a Case of Malignant Fibrous Histiocytoma of the Lungs

We present a case of a 78-yr-old man with malignant fibrous histiocytoma with multiple lesions in both lungs. Following diagnosis, he declined conventional chemotherapy and elected nutritional intervention by increasing intake of omega-3 fatty acids and lowering intake of omega-6 fatty acids. We estimated that he consumed 15 g of the long-chain omega-3 fatty acids eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) per day, and the ratio of linoleic acid/long-chain omega-3 fatty acids in his diet was 0.81. Serial computed tomography scans and pulmonary x-rays revealed remarkably a slow and steady decrease in the size and number of bilateral nodules. He has no apparent side effects from consuming large quantities of fish and algae oils rich in DHA and EPA and he remains asymptomatic.

Fatty acid composition of red blood cell membranes and risk of squamous cell carcinoma of the skin

Differential effects of fatty acids on carcinogenesis suggest that fatty acid composition is important in tumor development. Arachidonic acid and its metabolites elicit inflammation and promote tumor formation in mouse skin. Inhibitors of the arachidonic cascade inhibit tumor incidence. A population-based case control study in Southeastern Arizona tested the hypothesis that lower levels of arachidonic acid in RBC membranes were associated with decreased risk of skin squamous cell carcinoma (SCC; n = 335 SCC cases and 321 controls). Extracted and esterified RBC fatty acids were analyzed using capillary gas chromatography. Individual peaks for 14 fatty acids were measured as a percentage of total fatty acids. Logistic regression was used to estimate odds ratios (OR), adjusting for SCC risk factors (age, gender, actinic keratosis history, freckling, and tanning ability). Increased levels of arachidonic acid in RBC membranes were associated with increased risk of SCC [odds ratio (OR), 1.08 per mg/100 mL change; 95% confidence interval (95% CI), 1.02-1.15] and this association remained when controls with actinic keratosis precursor lesions were excluded. SCC risk was highest among the upper quartile of arachidonic acid (OR, 2.38; 95% CI, 1.37-4.12). In contrast, increasing proportions of palmitic acid (OR, 0.94; 95% CI, 0.89-1.00) and palmitoleicacid (OR, 0.49; 95% CI, 0.30-0.81) were associated with reduced SCC risk. More studies are needed to elucidate the function of RBC fatty acids so that recommendations can be made to alter the human diet for cancer prevention.

Polyunsaturated fatty acids partially reproduce the role of melanocytes in the epidermal melanin unit

The incidence rate of melanoma is higher in fair-skinned than in dark-skinned individuals. In negroid skin there is more eumelanin which is present in all skin layers and fewer polyunsaturated fatty acids (PUFA) than in caucasoid skin. The western diet, which is rich in omega-6 polyunsaturated fatty acids, is associated with more proneness to cancer including cutaneous melanoma. To study the respective influence of omega-6 PUFA and low phototype melanocytes on redox status -basal and following UV irradiation-, we used epidermal reconstructs. The addition of polyunsaturated fatty acids as well as the presence of low phototype melanocytes affected basal status similarly except for catalase activity, which decreased significantly in polyunsaturated fatty acid-supplemented reconstructs. Following UV, polyunsaturated fatty acids and low phototype melanocytes increased lipid and protein oxidative damage without affecting direct DNA damage. However, polyunsaturated fatty acids increased epidermal apoptosis whereas low phototype melanocytes decreased it. Since our data suggest that an omega-6 PUFA rich-diet may increase oxidative damage in melanocytes without inducing apoptosis, the long-term net outcome could be cumulated mutations and an increased risk of skin cancer, especially melanoma.

Nutritional protection against skin damage from sunlight

The concept of systemic photoprotection by dietary means is gaining momentum. Skin is continuously exposed to ultraviolet (UV) radiation, the major cause of skin disorders such as sunburn, photodamage, and nonmelanoma skin cancer. Most of the erythemal annual UV dose is encountered under nonvacation conditions, when no sunscreen is applied. In the absence of topically added compounds, skin protection depends solely on endogenous defense. Micronutrients can act as UV absorbers, as antioxidants, or can modulate signaling pathways elicited upon UV exposure. UV-induced erythema is a suitable parameter to assess photoprotection. Dietary protection is provided by carotenoids, tocopherols, ascorbate, flavonoids, or n-3 fatty acids, contributing to maintenance resistance as part of lifelong protection.

Omega 3 but not omega 6 fatty acids inhibit AP-1 activity and cell transformation in JB6 cells

Epidemiological and animal-based investigations have indicated that the development of skin cancer is in part associated with poor dietary practices. Lipid content and subsequently the derived fatty acid composition of the diet are believed to play a major role in the development of tumorigenesis. Omega 3 (omega3) fatty acids, including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), can effectively reduce the risk of skin cancer whereas omega 6 (omega6) fatty acids such as arachidonic acid (AA) reportedly promote risk. To investigate the effects of fatty acids on tumorigenesis, we performed experiments to examine the effects of the omega3 fatty acids EPA and DHA and of the omega6 fatty acid AA on phorbol 12-tetradecanoate 13-acetate (TPA)-induced or epidermal growth factor (EGF)-induced transcription activator protein 1 (AP-1) transactivation and on the subsequent cellular transformation in a mouse epidermal JB6 cell model. DHA treatment resulted in marked inhibition of TPA- and EGF-induced cell transformation by inhibiting AP-1 transactivation. EPA treatment also inhibited TPA-induced AP-1 transactivation and cell transformation but had no effect on EGF-induced transformation. AA treatment had no effect on either TPA- or EGF-induced AP-1 transactivation or transformation, but did abrogate the inhibitory effects of DHA on TPA- or EGF-induced AP-1 transactivation and cell transformation in a dose-dependent manner. The results of this study demonstrate that the inhibitory effects of omega3 fatty acids on tumorigenesis are more significant for DHA than for EPA and are related to an inhibition of AP-1. Similarly, because AA abrogates the beneficial effects of DHA, the dietary ratio of omega6 to omega3 fatty acids may be a significant factor in mediating tumor development.