The Study Of Breast Cancer Nosogenesis: The Relationship Between Sulfation And Methylation Of Catecholestrogens And The Effects Of Nitric Oxide On Estrogen Sulfation

INTRODUCTION.Prolonged exposure to high level of estrogen is a well known risk factor for breast carcinogenesis.Most of the research focused on the estrogen and estrogen receptor(ER) approach.In cells,estrogens,in particular estrone(E₁) and 17β-estradiol(E₂), can be converted to catecholestrogens(CEs) which may be oxidized to form CE-semiquinones and CE-quinones that are capable of binding to DNA to induce mutations,followed by carcinogenesis.Whether the body is equipped with protective mechanisms against potentially harmful CEs,therefore,is an important issue.Sulfate conjugation is a major pathway for the biotransformation and excretion of estrogens.Nitric oxide(NO) may affect tumor growth, differentiation,metastasis capability.By now there are little evidences show that whether NO decreases estrogen metabolism by affecting estrogens' sulfation.The effects of tamoxifen (TAM) on NO to breast cancer remain unknown.Purpose of this study:Part 1,To analyze the expression of estrogen receptor(ER), progesterone receptor(PR) in 145 breast cancer samples from patients and the correlation between the expression of ER,PR and menopause.Part2,To examine the relation between sulfation and methylation in the metabolism of CEs.Part 3,to measure the effects of NO Donors on estrogen sulfation by MCF-7 and MCF10A and to evaluate the influence of TAM on NO Donor effects.MATERIALS AND METHODS.Part 1:We used immunohisto-chemical methods to detect the expression of ER and PR in 145 cases of breast cancer and the relation between ER, PR expression and menopause.Part 2,MCF-7 breast cancer cells and MCF 10A human mammary epithelial cells were metabolically labeled with[³⁵S]sulfate in the presence of individual CEs to observe the CEs' sulfation.Part 3:Five NO Donors with different concentration were added to MCF-7 and MCF10A to analysis the[³⁵S]sulfated estrogen. Moreover,different concentration of TAM,SIN-1(one of the NO Donors) and estrodiol were added to MCF-7 and MCF 10A to evaluate the relationship between TAM and SIN-1 on estrogen sulfation. RESULTS.Part 1:Among the 145 breast cancer patients,the positive expression of ER and PR was 71.7%and 69.0%,individually;more ER and PR expression was found in postmenopausal breast cancer women compared to patients before menopause,but the result showed no significant difference(P＞0.05).Part 2,Analysis of the labeling media showed the generation and release of exclusively[³⁵S]sulfated 2-methoxy-E₁ or[³⁵S]sulfated 2-or 4-methoxy-E₂ by cells labeled in the presence of 2-OH-E₁ or 2-or 4-OH-E₂.Whereas both [³⁵S]sulfated 4-methoxy-E₁ and[³⁵S]sulfated 4-OH-E₁ were detected in the labeling media of cells labeled in the presence of 4-OH-E₁.These results indicated a concerted action of catechol-O-methyltransferase(COMT) and the cytosolic sulfotransferase(SULT) enzyme(s) in the metabolism of CEs.Enzymatic assays revealed that,five(SULT1A1,SULT1A2, SULT1A3,SULT1C4,and SULT1E1) of eleven known human SULTs tested could use CEs and methoxyestrogens(MEs) as substrates,with SULT1E1 displaying the strongest sulfating activity.Part 2:Five NO Donors can decrease the estrogen sulfation by MCF-7 and MCF 10A cells.There are dose-dependent inhibitory effects between NO Donors and estrogen sulfation. TAM had no significant effects on this inhibition.CONCLUSION:1,Most breast cancer patients showed ER,PR positive and ER,PR expression showed no difference(P＞0.05) between postmenopausal patients and the patients before menopause.However,there still were breast cancer patients with negative ER.More research should be focused on the breast cancer mechanism except for the ER.2,Sulfation is a major pathway for the biotransformation and excretion of estrogens.The fact that sulfated CEs and MEs were generated and released by cultured cells suggests a concerted action of COMT and SULT enzymes in the metabolism and detoxification of these compounds in vivo.3,The inhibitory effects on estrogens sulfation in MCF-7 and MCF10A cells suggested that the increase of NO might promote the development of breast cancer.TAM showed its therapy effects on breasts cancer could be beyond the inhibition on estrogens sulfation by NO.