The Role of Nutrition in the Prevention of Breast Cancer

Effects of Inositol Hexaphosphate and Myo-Inositol Administration in Breast Cancer Patients during Adjuvant Chemotherapy

Background: Treatment of breast cancer (BC) includes locoregional and systemic therapies depending on tumor and patient’s characteristics. Inositol hexaphosphate (IP6) is known as a strong antioxidant agent, able to improve local (i.e., breast region) side effects, functional status and quality-of-life. We investigated some potential beneficial effects, including hematological and local, of the combined therapy with oral myo-inositol administration and topical IP6 application in patients undergoing surgery for BC and eligible to adjuvant chemotherapy. Methods: We considered BC patients randomly assigned to the Inositol Group (oral myo-inositol + IP6 local application for the entire neoadjuvant treatment period) and to the Control Group (standard of care). The EORTC QLQ-BR23 and QLQ-C30 questionnaires were administered to both groups and blood parameters were assessed as per clinical routine practice at baseline (before starting adjuvant chemotherapy), T1 (after the first two doses of epirubicin-cyclophosphamide regimen), T2 (at the end of epirubicin-cyclophosphamide regimen), T3 (after the first six doses of paclitaxel regimen), and T4 (at the end of the paclitaxel treatment). Results: A total of 36 BC patients were considered, 18 in the Inositol Group and 18 in the Control Group. The Inositol Group showed a lower decrease in red blood cells, hemoglobin levels and white blood cells with respect to controls (p ≤ 0.02), as well as amelioration in scores related to breast and arm local symptoms (p ≤ 0.02), body image (p = 0.04) and quality-of-life related symptoms (p ≤ 0.04). Conclusions: In our cohort of BC patients, a combined treatment with oral myo-inositol + IP6 local application was able to improve local symptoms and quality-of-life related symptoms which represent clinically relevant aspects associated with patient’s prognosis.

Association between Polyphenol Intake and Breast Cancer Risk by Menopausal and Hormone Receptor Status

There is limited evidence of phenolic compounds acting as protective agents on several cancer types, including breast cancer (BC). Nevertheless, some polyphenol classes have not been investigated and there is a lack of studies assessing the effect on menopausal status and hormone receptor status as influenced by these compounds. The objective of this study is to evaluate the association between the intake of all polyphenol classes in relation to the BC risk by menopausal and hormone receptor status. We used data from a population-based multi-case-control study (MCC-Spain) including 1472 BC cases and 1577 controls from 12 different regions of Spain. The odds ratios (ORs) with 95% CI were calculated using logistic regression of mixed effects by quartiles and log2 of polyphenol intakes (adjusted for the residual method) of overall BC, menopausal and receptor status. No associations were found between total intake of polyphenols and BC risk. However, inverse associations were found between stilbenes and all BC risk (OR_{Q4 vs. Q1}: 0.70, 95%CI: 0.56–0.89, P_trend = 0.001), the consumption of hydroxybenzaldehydes (OR_{Q4 vs. Q1}: 0.75, 95%CI: 0.59–0.93, P_trend = 0.012) and hydroxycoumarins (OR_{Q4 vs. Q1}: 0.73, 95%CI: 0.57–0.93; P_trend = 0.005) were also inversely associated. The intake of stilbenes, hydroxybenzaldehydes and hydroxycoumarins can contribute to BC reduction risk on all menopausal and receptor statuses.

Estrogen Receptor Beta (ERβ) May Act as Mediator in Apoptotic Induction of Grape Seed Extract (GSE)

BACKGROUND

Grape seed extract is a complex mixture of polyphenols. Its anti-tumor effects have been reported by several studies. Estrogen receptors (ERs) are commonly considered as important markers for breast cancer. The present study aimed to evaluate the apoptotic effects of GSE on MCF7 breast cancer cells and assessed the expression of ERβ during treatment of cells with GSE.

MATERIAL AND METHODS

The half maximal inhibitory concentration (IC50) of GSE in MCF7 breast cancer cells were calculated by treating cells with serial dilution of GSE for 48 hours and cell viability evaluated using MTT assay. Then cells assigned to three groups: control (no treatment), DMSO (cells treated with 0.05% of DMSO) and GSE group (cells treated with of GSE for 48 hours). The apoptosis assay was performed by detecting Annexin V protein by flow cytometry. The gene expression of ERβ and caspase-3 was evaluated by Real-Time PCR.

RESULTS

Cells in GSE group treated with GSE IC50 concentration for 48 hours. Annexin V staining assay, represented early apoptosis detected by flow cytometry analysis showed significantly higher expression (p<0.01) than control and DMSO groups. Moreover, results of Real-Time PCR showed a significant expression in ERβ and caspase-3 genes in GSE group compared to control and DMSO groups (Fold change = 2.3 and 3.5, respectively).

CONCLUSION

GSE may induce apoptosis in MCF7 human breast cancer cells by activation of ERβ gene.

Broad Spectrum Anticancer Activity of Myo-Inositol and Inositol Hexakisphosphate

Inositols (myo-inositol and inositol hexakisphosphate) exert a wide range of critical activities in both physiological and pathological settings. Deregulated inositol metabolism has been recorded in a number of diseases, including cancer, where inositol modulates different critical pathways. Inositols inhibit pRB phosphorylation, fostering the pRB/E2F complexes formation and blocking progression along the cell cycle. Inositols reduce PI3K levels, thus counteracting the activation of the PKC/RAS/ERK pathway downstream of PI3K activation. Upstream of that pathway, inositols disrupt the ligand interaction between FGF and its receptor as well as with the EGF-transduction processes involving IGF-II receptor and AP-1 complexes. Additionally, Akt activation is severely impaired upon inositol addition. Downregulation of both Akt and ERK leads consequently to NF-kB inhibition and reduced expression of inflammatory markers (COX-2 and PGE2). Remarkably, inositol-induced downregulation of presenilin-1 interferes with the epithelial-mesenchymal transition and reduces Wnt-activation, β-catenin translocation, Notch-1, N-cadherin, and SNAI1 release. Inositols interfere also with the cytoskeleton by upregulating Focal Adhesion Kinase and E-cadherin and decreasing Fascin and Cofilin, two main components of pseudopodia, leading hence to invasiveness impairment. This effect is reinforced by the inositol-induced inhibition on metalloproteinases and ROCK1/2 release. Overall, these effects enable inositols to remodel the cytoskeleton architecture.

Effect of 8-week nutrition counseling to increase phytochemical rich fruit and vegetable consumption in korean breast cancer patients: a randomized controlled trial

High fruit and vegetable consumption is associated with a lower risk of breast cancer. The incidence of breast cancer is continuously increasing in Korea, but only a few studies on nutrition intervention in breast cancer patients has been reported. The aim of this study was to investigate whether an 8-week nutrition intervention based on dietary counseling can promote fruit and vegetable consumption, increase serum antioxidant nutrient levels, and improve quality of life in Korean breast cancer patients. Sixty-one breast cancer patients received either standard care (n = 31) or nutrition counseling (n = 30). The standard care group was given brochures recommending phytochemical rich diet. The intervention group was provided with two nutrition counseling sessions and one cooking class session, thereby encouraged subjects to eat at least 10 or more servings of fruits and vegetables per day. After 8-week intervention, waist circumference in the intervention group was significantly decreased (p < 0.001) even though no difference was reported for body mass index. Energy intake (p = 0.007), fiber (p < 0.001), and antioxidant nutrient (vitamin A, C, E, and β-carotene, p < 0.001, respectively) intakes were significantly increased. Serum antioxidant level was also increased significantly, i.e., vitamin A (p = 0.048); vitamin E (p = 0.004). Total vegetable intake (excluding kimchi intake) in the intervention group was increased from 425 g to 761 g (p < 0.001), fruit consumption was also increased from 232 g to 334 g (p < 0.001), while standard care group did not show any significant change. Our study showed that nutrition counseling and providing cooking tips helped to encourage the patient to consume and maintain more fruit and vegetable intakes.

Diet components associated with perceived fatigue in breast cancer survivors

Little is known about the contribution of diet components independent of body composition to persistent fatigue in breast cancer survivors. Therefore, our study aim was to determine the associations among dietary intake and fatigue in relation to and independent of adiposity and physical activity (PA) in breast cancer survivors. Baseline data from 42 breast cancer survivors enrolled in a randomised exercise trial were analysed: fatigue (Functional Assessment of Cancer Therapy for fatigue), diet components (3-day diet record), body mass index, per cent body fat (dual-energy X-ray absorptiometry) and PA (accelerometer). The mean age was 54 ± 9 years with an average body mass index of 30.5 ± 8.1 kg/m(2). Fatigue was positively associated with % of kcal/day fat intake (r = 0.31, P < 0.05) and inversely related to fibre g/day (r = 0.38, P < 0.05) and carbohydrate g/day intake (r = 0.31, P < 0.05). Mean fatigue was greater for participants eating <25 g/day of fibre compared with >25 g/day of fibre (15.7 ± 10.8 versus 6.4 ± 3.7, P < 0.005). No significant associations were noted between fatigue and PA or body composition. Diets high in fibre and low in fat are associated with reduced fatigue in breast cancer survivors. The difference in fatigue for low- versus high-fibre diets exceeded the minimal clinically important difference of three units. Prospective studies evaluating the effect of changing diet on fatigue in breast cancer survivors are warranted.

The effect of inositol hexaphosphate on the expression of selected metalloproteinases and their tissue inhibitors in IL-1β-stimulated colon cancer cells

INTRODUCTION

Matrix metalloproteinases (MMPs) have repeatedly been shown to play a very active role in extracellular matrix degradation associated with tumor invasion and metastasis. Tissue inhibitors of MMPs (TIMPs) are well-known for their ability to inhibit MMP activity thereby inhibiting malignant progression. Inositol hexaphosphate (IP6 phytic acid) has been recognized to have both preventive and therapeutic effects against various cancers including that of colon. In in vitro studies, IP6 has been demonstrated to inhibit cancer cell adhesion and migration. In the present study, the effect of IP6 on the expression of MMP and TIMP genes was evaluated in unstimulated and IL-1β-stimulated colon cancer cell line Caco-2.

MATERIALS AND METHODS

Real-time QRT-PCR was used to validate the transcription level of selected MMP and TIMP genes in Caco-2 cells after treatment with 1 ng/ml of IL-1β, 2.5 mM of IP6, and both for 6, 12, and 24 h.

RESULTS

Stimulation of cells with IL-1β only resulted in an overexpression of MMP and their TIMP mRNAs. A significant decrease in MMP-13, MMP-3, MMP-2, and TIMP-1 basal expression was achieved by IP6. IP6 was also an efficient downregulator of MMP-1, MMP-9, and TIMP-2 genes transcription stimulated by IL-1β in 6 h lasting culture. After 12 h, IL-1β-induced MMP-2 mRNA expression was significantly reduced by IP6.

CONCLUSION

Proinflammatory cytokine IL-1β upregulates MMP and TIMP mRNAs expression in colon cancer epithelial cells Caco-2. IP6 (2.5 mM) influences constitutive expression of both MMP and TIMP genes and downregulates IL-1β stimulated transcription of some of these genes. IP6 exerts its anti-metastatic activity through modulation of MMP and TIMP genes expression to prevent cancer cell migration and invasion.

Antioxidants and breast cancer risk- a population-based case-control study in Canada

BACKGROUND

The effect of antioxidants on breast cancer is still controversial. Our objective was to assess the association between antioxidants and breast cancer risk in a large population-based case-control study.

METHODS

The study population included 2,362 cases with pathologically confirmed incident breast cancer (866 premenopausal and 1,496 postmenopausal) and 2,462 controls in Canada. Intakes of antioxidants from diet and from supplementation as well as other potential risk factors for breast cancer were collected by a self-reported questionnaire.

RESULTS

Compared with subjects with no supplementation, 10 years or longer supplementation of zinc had multivariable-adjusted odds ratios (OR) and 95% confidence intervals (CI) of 0.46 (0.25-0.85) for premenopausal women, while supplementation of 10 years or longer of multiple vitamin, beta-carotene, vitamin C, vitamin E and zinc had multivariable-adjusted ORs (95% CIs) of 0.74 (0.59, 0.92), 0.58 (0.36, 0.95), 0.79 (0.63-0.99), 0.75 (0.58, 0.97), and 0.47 (0.28-0.78), respectively, for postmenopausal women. No significant effect of antioxidants from dietary sources (including beta-carotene, alpha-carotene, lycopene, lutein and zeaxanthin, vitamin C, vitamin E, selenium and zinc) or from supplementation less than 10 years was observed.

CONCLUSIONS

This study suggests that supplementation of zinc in premenopausal women, and supplementation of multiple vitamin, beta-carotene, vitamin C, vitamin E and zinc in postmenopausal women for 10 or more years may protect women from developing breast cancer. However, we were unable to determine the overall effect of total dose or intake from both diet and supplement.

Dietary modification for women after breast cancer treatment: a narrative review

Diet is thought to account for about 25% of cancers in developed countries. It is well documented that the risks associated with both the breast cancer itself and its treatments are important for women previously treated for breast cancer. Women are at risk of recurrence of the primary disease and prone to develop treatment-induced co-morbidities, some of which are thought to be modified by diet. With a view to making dietary recommendations for the breast cancer patients we encounter in our clinical nursing research, we mined the literature to scope the most current robust evidence concerning the role of the diet in protecting women against the recurrence of breast cancer and its potential to ameliorate some of the longer-term morbidities associated with the disease. We found that the evidence about the role of the diet in breast cancer recurrence is largely inconclusive. However, drawing on international guidelines enabled us to make three definitive recommendations: women at risk of breast cancer recurrence, or who experience co-morbidities as a result of treatment, should limit their exposure to alcohol, moderate their nutritional intake so it does not contribute to post-menopausal weight gain, and should adhere to a balanced diet. Nursing education planned for breast cancer patients about dietary issues should ideally be individually tailored, based on a good understanding of the international recommendations and the evidence underpinning them.

Hormonal and metabolic modulation through nutrition: towards a primary prevention of breast cancer

Breast cancer (BC) is a polygenic and multifactorial disease for which estrogens have been recognized as the main risk factor, and for which lifestyle plays a key role. Previous epidemiologic cancer research performed in Uruguayan population delimited its dietary and anthropometric profiles. Recognizing the difficulty for universalizing a nutritional basis for prevention due to different eating patterns among regions and countries, we summarize the existent knowledge linking nutrition, estrogens, metabolism and BC. As an attempt towards primary prevention of BC, we present recommendations mainly based on country-specific research findings and modifiable putative risk and protective factors, proposing to modify the intake of meats and other fatty foods--especially sources of Ω-6 and Ω-3 fatty acids--adding olive oil, selected vegetables, citrus fruits and working towards adequate body fat/muscle proportions. From a medical and ethical viewpoint, it is justified to recommend certain nutritional changes to women, because no adverse side effects are expected to occur.

Do alterations in mitochondrial DNA play a role in breast carcinogenesis?

A considerable body of evidence supports a role for oxidative stress in breast carcinogenesis. Due to their role in producing energy via oxidative phosphorylation, the mitochondria are a major source of production of reactive oxygen species, which may damage DNA. The mitochondrial genome may be particularly susceptible to oxidative damage leading to mitochondrial dysfunction. Genetic variants in mtDNA and nuclear DNA may also contribute to mitochondrial dysfunction. In this review, we address the role of alterations in mtDNA in the etiology of breast cancer. Several studies have shown a relatively high frequency of mtDNA mutations in breast tumor tissue in comparison with mutations in normal breast tissue. To date, several studies have examined the association of genetic variants in mtDNA and breast cancer risk. The G10398A mtDNA polymorphism has received the most attention and has been shown to be associated with increased risk in some studies. Other variants have generally been examined in only one or two studies. Genome-wide association studies may help identify new mtDNA variants which modify breast cancer risk. In addition to assessing the main effects of specific variants, gene-gene and gene-environment interactions are likely to explain a greater proportion of the variability in breast cancer risk.

Meat, eggs, dairy products, and risk of breast cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort

BACKGROUND

A Western diet is associated with breast cancer risk.

OBJECTIVE

We investigated the relation of meat, egg, and dairy product consumption with breast cancer risk by using data from the European Prospective Investigation into Cancer and Nutrition (EPIC).

DESIGN

Between 1992 and 2003, information on diet was collected from 319,826 women. Disease hazard ratios were estimated with multivariate Cox proportional hazard models.

RESULTS

Breast cancer cases (n = 7119) were observed during 8.8 y (median) of follow-up. No consistent association was found between breast cancer risk and the consumption of any of the food groups under study, when analyzed by both categorical and continuous exposure variable models. High processed meat consumption was associated with a modest increase in breast cancer risk in the categorical model (hazard ratio: 1.10; 95% CI: 1.00, 1.20; highest compared with lowest quintile: P for trend = 0.07). Subgroup analyses suggested an association with butter consumption, limited to premenopausal women (hazard ratio: 1.28; 95% CI: 1.06, 1.53; highest compared with lowest quintile: P for trend = 0.21). Between-country heterogeneity was found for red meat (Q statistic = 18.03; P = 0.05) and was significantly explained (P = 0.023) by the proportion of meat cooked at high temperature.

CONCLUSIONS

We have not consistently identified intakes of meat, eggs, or dairy products as risk factors for breast cancer. Future studies should investigate the possible role of high-temperature cooking in the relation of red meat intake with breast cancer risk.

How old are African American women when they receive their first mammogram? Results from a church-based study

African American women in the U.S. have the highest breast cancer mortality though not the highest breast cancer incidence. This high mortality rate has been attributed in part to discrepancies in screening between African American and White women. Although this gap in mammography utilization is closing, little is known about what has been and is driving the screening practices of African American women, in particular age at first mammogram. This study examined the rates of breast cancer screening in an African American community sample from eight churches in greater Baltimore, Maryland and investigated the association between various factors and age at first mammogram. Participants were 213 women ages 22-89 years. About 77% of women had ever had a mammogram. Over 40% had their first mammogram before age 40. Women who first screened before age 40 had greater odds than women who had never screened of being knowledgeable about screening guidelines, of having received a physician recommendation to screen, and of having three or more female relatives who had been screened. Women who first screened at or after age 40 were more likely to have stronger religious beliefs of health than women who never had screened. These findings suggest the importance of reinforcing factors in screening behavior for African American women and have implications for physician training and public health education about breast cancer screening. A better understanding of African American women's mammography practice including early screening is needed to reduce this population's disproportionate breast cancer mortality risk.

Low-fat dietary pattern and risk of benign proliferative breast disease: a randomized, controlled dietary modification trial

Modifiable factors, including diet, might alter breast cancer risk. We used the Women's Health Initiative Dietary Modification trial to test the effect of the intervention on risk of benign proliferative breast disease, a condition associated with increased risk of, and considered to be on the pathway to, invasive breast cancer. The Women's Health Initiative Dietary Modification trial was a randomized, controlled, primary prevention trial conducted in 40 U.S. clinical centers from 1993 to 2005. A total of 48,835 postmenopausal women, ages 50 to 79 years, without prior breast cancer, were enrolled. Participants were randomly assigned to the dietary modification intervention group or to the comparison group. The intervention was designed to reduce total dietary fat intake to 20% of total energy intake, and to increase fruit and vegetable intake to > or =5 servings/d and intake of grain products to > or =6 servings/d, but resulted in smaller, albeit significant, changes in practice. Participants had biennial mammograms and regular clinical breast exams. We identified women who reported breast biopsies free of cancer, obtained the histologic sections, and subjected them to standardized central review. During follow-up (average, 7.7 years), 570 incident cases of benign proliferative breast disease were ascertained in the intervention group and 793 in the comparison group. The hazard ratio for the association between dietary modification and benign proliferative breast disease was 1.09 (95% confidence interval, 0.98-1.23). Risk varied by levels of baseline total vitamin D intake but it varied little by levels of other baseline variables. These results suggest that a modest reduction in fat intake and increase in fruit, vegetable, and grain intake do not alter the risk of benign proliferative breast disease.

Nutrients and nipple aspirate fluid composition: the breast microenvironment regulates protein expression and cancer aetiology

The aetiology of breast cancer is complex and multifactorial, and may include diet and xenobiotic compounds. A change in diet affects nutrient levels in blood, but to what extent diet can affect micronutrient concentrations in the breast is not yet well established. Breast nipple aspirate fluids (NAF) can be non-invasively obtained from the breast in most women; it represents a biological tool to assess metabolic changes in the breast ductal microenvironment. A wide variation in biomolecular and hormonal composition of NAFs collected from healthy and breast cancer patient may be due to genetic and nutritional factors; however, micro- and macro-nutrients may influence the secretory status of these women, thus NAF composition and risk of breast carcinoma. The aim of this overview is to highlight the detrimental/beneficial role that diet-related compounds in nipple aspirate fluid can have in breast cancer risk.

Role of dietary lignans in the reduction of breast cancer risk

Lignans are a large group of fiber-associated phenolic compounds widely distributed in edible plants. Some of the ingested plant lignans are converted by intestinal microbiota to enterolignans, enterodiol (END) and enterolactone (ENL), the latter of which has been thought to be the major biologically active lignan, and suggested to be associated with low risk of breast cancer. In line with this, administration of plant lignans which are further metabolized to ENL, or ENL as such, have been shown to inhibit or delay the growth of experimental mammary cancer. The mechanism of anticarcinogenic action of ENL is not yet fully understood, but there is intriguing evidence for ENL as a modulator of estrogen signaling. These findings have generated interest in the use of lignans as components of breast cancer risk reducing functional foods. Identification of target groups, who would benefit most, is of pivotal importance. Therefore, further identification and validation of relevant biomarkers, which can be used as indicators of lignan or ENL action and breast cancer risk reduction at different stages of the disease, are of importance.

Breast cancer and metabolic syndrome linked through the plasminogen activator inhibitor-1 cycle

Plasminogen activator inhibitor-1 (PAI-1) is a physiological inhibitor of urokinase (uPA), a serine protease known to promote cell migration and invasion. Intuitively, increased levels of PAI-1 should be beneficial in downregulating uPA activity, particularly in cancer. By contrast, in vivo, increased levels of PAI-1 are associated with a poor prognosis in breast cancer. This phenomenon is termed the "PAI-1 paradox". Many factors are responsible for the upregulation of PAI-1 in the tumor microenvironment. We hypothesize that there is a breast cancer predisposition to a more aggressive stage when PAI-1 is upregulated as a consequence of Metabolic Syndrome (MetS). MetS exerts a detrimental effect on the breast tumor microenvironment that supports cancer invasion. People with MetS have an increased risk of coronary heart disease, stroke, peripheral vascular disease and hyperinsulinemia. Recently, MetS has also been identified as a risk factor for breast cancer. We hypothesize the existence of the "PAI-1 cycle". Sustained by MetS, adipocytokines alter PAI-1 expression to promote angiogenesis, tumor-cell migration and procoagulant microparticle formation from endothelial cells, which generates thrombin and further propagates PAI-1 synthesis. All of these factors culminate in a chemotherapy-resistant breast tumor microenvironment. The PAI-1 cycle may partly explain the PAI-1 paradox. In this hypothesis paper, we will discuss further how MetS upregulates PAI-1 and how an increased level of PAI-1 can be linked to a poor prognosis.

Protection against cancer by dietary IP6 and inositol

Inositol hexaphosphate (IP(6)) is a naturally occurring polyphosphorylated carbohydrate, abundantly present in many plant sources and in certain high-fiber diets, such as cereals and legumes. In addition to being found in plants, IP(6) is contained in almost all mammalian cells, although in much smaller amounts, where it is important in regulating vital cellular functions such as signal transduction, cell proliferation, and differentiation. For a long time IP(6) has been recognized as a natural antioxidant. Recently IP(6) has received much attention for its role in cancer prevention and control of experimental tumor growth, progression, and metastasis. In addition, IP(6) possesses other significant benefits for human health, such as the ability to enhance immune system, prevent pathological calcification and kidney stone formation, lower elevated serum cholesterol, and reduce pathological platelet activity. In this review we show the efficacy and discuss some of the molecular mechanisms that govern the action of this dietary agent. Exogenously administered IP(6) is rapidly taken up into cells and dephosphorylated to lower inositol phosphates, which further affect signal transduction pathways resulting in cell cycle arrest. A striking anticancer action of IP(6) was demonstrated in different experimental models. In addition to reducing cell proliferation, IP(6) also induces differentiation of malignant cells. Enhanced immunity and antioxidant properties also contribute to tumor cell destruction. Preliminary studies in humans show that IP(6) and inositol, the precursor molecule of IP(6), appear to enhance the anticancer effect of conventional chemotherapy, control cancer metastases, and improve quality of life. Because it is abundantly present in regular diet, efficiently absorbed from the gastrointestinal tract, and safe, IP(6) + inositol holds great promise in our strategies for cancer prevention and therapy. There is clearly enough evidence to justify the initiation of full-scale clinical trials in humans.