Ethnic differences in breast cancer risk: a possible role for pregnancy levels of alpha-fetoprotein?

Maternal Pregnancy Hormone Concentrations in Countries with Very Low and High Breast Cancer Risk

BACKGROUND

Breast cancer rates in Asia are much lower than in Europe and North America. Within Asia, rates are lower in Mongolia than in neighboring countries. Variation in pregnancy exposure to endogenous hormone concentrations may explain the differences, but data are lacking.

METHODS

We measured maternal serum progesterone, prolactin, estradiol and estrone concentrations in the second half of pregnancy in a cross-sectional study of urban (n = 143-194 depending on the analyte) and rural (n = 150-193) Mongolian women, and U.S. women from Boston (n = 66-204). Medical records provided information on maternal and perinatal factors. Geometric mean hormones were estimated from standard linear models with the log-hormone as the dependent variable and country as the independent variable adjusted for maternal and gestational age at blood draw.

RESULTS

Mean concentrations of prolactin (5722 vs. 4648 uIU/mL; p < 0.0001) and estradiol (17.7 vs. 13.6 ng/mL; p < 0.0001) were greater in Mongolian than U.S. women, while progesterone (147 vs. 201 ng/mL; p < 0.0001) was lower. Mean hormone concentrations were similar in rural and urban Mongolian women. Results were generally similar, with additional adjustment for gravidity, parity, height, body mass index at blood draw, education and alcohol use during pregnancy, and when stratified by offspring sex or parity.

CONCLUSIONS

Mongolian women had greater concentrations of prolactin and estrogen and lower concentrations of progesterone than U.S. women, while hormone concentrations were similar in rural and urban Mongolian pregnancies.

IMPACT

These data do not support the hypothesis that estrogen concentrations in pregnant women are lower in Mongolian compared with Caucasian women.

Serum chromogranin A is a useful marker for Japanese patients with pancreatic neuroendocrine tumors

Although chromogranin A (CGA) is a useful marker for pancreatic neuroendocrine tumors (pNET) in the West, its usefulness in Japanese populations is unclear. To assess this, we evaluated the serum CGA levels in 189 patients with various pancreatic diseases, including proven pNET (n = 69), pancreatic cancer (PC) (n = 50), chronic pancreatitis (CP) (n = 50) and autoimmune pancreatitis (AIP) (n = 20), and 112 normal controls (controls) using an ELISA kit. The mean CGA level of patients with pNET was significantly higher than any of the other groups (407.8 ± 984.6 ng/mL [pNET] vs 91.8 ± 101.8 ng/mL [PC], 93.6 ± 57.5 ng/mL [CP], 69.9 ± 52.4 ng/mL [AIP] and 62.5 ± 48.3 ng/mL [controls]). Limiting the analysis to patients not using proton pump inhibitors (PPI), the CGA level of patients with PC or CP was not significantly different compared with the controls. Discriminant analysis revealed that the best cut-off value of CGA to distinguish patients with pNET from the controls was 78.7 ng/mL, with a sensitivity and specificity of 53.6% and 78.6%, respectively. In patients with pNET, significant factors associating with elevated CGA levels were tumor classification, tumor size, and the presence of liver metastases in univariate analysis as well as PPI use and the presence of liver metastases in multivariate analysis. We show that CGA is a useful marker for diagnosing pNET in Japanese populations and for distinguishing patients with pNET from patients with other pancreatic diseases. The increased use of CGA in Japan will likely be a helpful tool in managing these patients, as found in the West.

Screening preeclamptic cord plasma for proteins associated with decreased breast cancer susceptibility

Preeclampsia, a complication of pregnancy characterized by hypertension and proteinuria, has been found to reduce the subsequent risk for breast cancer in female offspring. As this protective effect could be due to exposure to preeclampsia-specific proteins during intrauterine life, the proteomic profiles of umbilical cord blood plasma between preeclamptic and normotensive pregnancies were compared. Umbilical cord plasma samples, depleted of 14 abundant proteins, were subjected to proteomic analysis using the quantitative method of nanoACQUITY ultra performance liquid chromatography-mass spectrometry with elevated energy mode of acquisition(E) (NanoUPLC-MS(E)). Sixty-nine differentially expressed proteins were identified, of which 15 and 6 proteins were only detected in preeclamptic and normotensive pregnancies, respectively. Additionally, expression of 8 proteins (gelsolin, complement C5, keratin type I cytoskeletal 10, pigment epithelium-derived factor, complement factor B, complement component C7, hemoglobin subunit gamma-2 and alpha-fetoprotein) were up-regulated in preeclampsia with a fold change of ≥2.0 when compared to normotensive pregnancies. The identification of alpha-fetoprotein in preeclamptic umbilical cord blood plasma supported the validity of this screen as alpha-fetoprotein has anti-estrogenic properties and has previously been linked to preeclampsia as well as a reduced breast cancer risk. The findings of this pilot study may provide new insights into the mechanistic link between preeclampsia and potentially reduced breast cancer susceptibility in adult life.

Cord serum estrogens, androgens, insulin-like growth factor-I, and insulin-like growth factor binding protein-3 in Chinese and U.S. Caucasian neonates

Markedly lower breast cancer incidence rates in Asians than Caucasians are not explained by established adult risk factors. Migration studies suggest the importance of early-life exposures, including perhaps the in utero period. Concentrations of steroid hormones and insulin-like growth factors (IGF) were measured in umbilical cord sera from pregnancies in Shanghai, China (n = 121) and Boston, MA (n = 111). Pregnancy characteristics were ascertained by interview and medical records. Means and percent differences in hormone concentrations comparing Chinese with Caucasians and 95% confidence intervals were estimated from linear regression models. Cord concentrations of androstenedione (91.9%), testosterone (257%), estriol (48.6%), and IGF binding protein-3 (21.1%) were significantly higher in the Chinese than U.S. samples, and cord prolactin was lower (-14.9%). Cord estradiol and IGF-I concentrations did not differ by race/ethnicity. With adjustment for gestational length, maternal age, pre-pregnancy weight, and weight gain, androstenedione (60.5%), testosterone (185%), and IGF binding protein-3 (40.4%) remained significantly higher in the Chinese, whereas the higher estriol and lower prolactin concentrations were attenuated. In addition, estradiol levels became lower in the Chinese (-29.8%) but did not reach statistical significance. Results were generally similar when restricted to first full-term pregnancies, with reduced estradiol concentrations in the Chinese reaching statistical significance after adjustment. These data are consistent with the hypothesis that elevated prenatal androgen exposure could mediate reductions in breast cancer risk. The meaning of the change in findings for estrogens after controlling for factors related to the pregnancy is unclear with regard to explaining international breast cancer differences.

Multiparity and the risk of premenopausal breast cancer: different effects across ethnic groups in Singapore

BACKGROUND

The relationship between multiparity and premenopausal breast cancer risk is different in Caucasian, African-American and Hispanic women. For Asian women, this relationship has never been well studied.

METHODS

Within the Singapore Birth Registry, we selected all women who had a first child between 1986 and 2002 (169,936 Chinese, 40,521 Malay, 17,966 Indian). We linked them to the Singapore Cancer Registry data to identify those who developed breast cancer after childbirth (n = 527). We used multivariate Cox analysis to examine the relationship between parity, ethnicity and premenopausal breast cancer risk.

RESULTS

Compared to Chinese, Malay women had increased and Indian women had decreased risks of premenopausal breast cancer (adjusted Hazard Ratios [HRadj] 1.25 [1.0-1.6] and 0.48 [0.3-0.8] respectively). Multiparity did not modify the risk of premenopausal breast cancer in Chinese and Indians. In Malays there was a significant risk reduction with increasing parity (P (trend )0.037). Malay women with one, two and >or=3 children had premenopausal breast cancer risks (HR(adj)) of 1.86 (1.2-3.0), 1.52 (1.1-2.2) and 0.87 (0.6-1.3) respectively compared to their Chinese counterparts.

CONCLUSIONS

The impact of multiparity on premenopausal breast cancer risk differs across ethnic groups in Singapore. Increasing parity reduces the risk of premenopausal breast cancer in Malay, but not in Chinese and Indian women. Uniparous Malay women have twice the risk of premenopausal breast cancer compared to uniparous Chinese. This excess risk disappears after giving birth to >or=3 children. Indian women have lower premenopausal breast cancer risks than Chinese, regardless of their parity status.

Exploring the underlying hormonal mechanisms of prenatal risk factors for breast cancer: a review and commentary

Prenatal factors have been hypothesized to influence subsequent breast cancer development. Directly evaluating the associations of in utero exposures with risk, however, presents several methodologic and theoretical challenges, including the long induction period between exposure and disease and the lack of certainty regarding the critical timing of exposure. Indirect evaluation of these associations has been achieved by use of proxies such as gestational and neonatal characteristics. Evidence suggests that preeclampsia is associated with a reduced breast cancer risk, whereas high birth weight and dizygotic twinning seem associated with an increased risk. Asians born in Asia have substantially lower breast cancer risks than women born in the West. Although data thus far are few, what exists is not consistent with a unifying hypothesis for a particular biological exposure (such as estrogens or androgens) during pregnancy as mediating the observed associations between pregnancy factors and breast cancer risk. This suggests that additional studies of prenatal factors should seek to broaden the range of hormones, growth, and other endocrine factors that are evaluated in utero. Once candidate biomarkers are identified, assessing them with respect to breast cancer and with intermediate end points in carcinogenesis should be a priority. In addition, investigations should explore the possibility that in utero exposures may not act directly on the breast, but may alter other physiologic pathways such as hormone metabolism that have their effect on risk later in life.

Levels and correlates of alpha-fetoprotein in normal pregnancies among Caucasian and Chinese women

Alpha-fetoprotein has been suggested to have anti breast cancer properties both in adult life and in utero. We studied correlates of maternal serum alpha-fetoprotein levels in normal singleton pregnancies. This was a prospective study relying on women attending maternal units in major teaching hospitals in Boston, USA and Shanghai, China. Specifically, 212 Caucasian women in Boston, and 196 Asian women in Shanghai provided blood samples at the 16th and 27th gestational week. Maternal serum alpha-fetoprotein levels were measured and correlated with maternal and newborn parameters through multiple regression procedures, controlling for a set of potential confounders, including maternal levels of measured hormones. Alpha-fetoprotein was strongly inversely associated with maternal prepregnancy body mass index (-4.73 ng/l at the 27th week per 1 kg/m of body mass index, with 95% confidence intervals -7.09 to -2.36), whereas it was not related to parity, gender of offspring or birth weight. Duration of gestation was inversely associated with maternal alpha-fetoprotein levels, particularly among Caucasian women (-0.22 weeks per 60 ng/l of alpha-fetoprotein at the 27th week, with 95% confidence intervals -0.39 to -0.05). In normal pregnancies, maternal alpha-fetoprotein is inversely related to prepregnancy body mass index and appears to have a physiologic role on duration of gestation rather than on birth weight.

Effects of parity on pregnancy hormonal profiles across ethnic groups with a diverse incidence of breast cancer

Epidemiologic evidence suggests that a full-term pregnancy may affect maternal risk of breast cancer later in life. The objective of this cross-sectional study was to compare circulating levels of maternal hormones affecting breast differentiation (human chorionic gonadotropin and prolactin) and proliferation [alpha-fetoprotein, insulin-like growth factor I (IGF-I), and estradiol] between women at a low to moderate risk (Asians and Hispanics), as compared with women at a high risk for breast cancer (Caucasians and African-Americans). Between May 2002 and December 2004, a total of 586 pregnant women were approached during a routine prenatal visit. Among them, 450 women (206 Caucasian, 126 Asian, 88 Hispanic, and 30 African-American) met the inclusion criteria and signed the informed consent. Only singleton pregnancies were considered. Blood samples were drawn during the second trimester of pregnancy. Laboratory analyses were done using the IMMULITE 2000 immunoassay system. Gestational age standardized mean levels of estradiol, IGF-I, and prolactin were significantly higher in Hispanic women compared with Caucasian women. Mean concentration of IGF-I was significantly higher in African-American women compared with Caucasian and Asian women. No significant differences in pregnancy hormone levels were observed between Caucasian and Asian (predominantly second-generation Chinese) women in this study. Irrespective of ethnicity, women who had their first pregnancy had substantially higher mean levels of alpha-fetoprotein, human chorionic gonadotropin, estradiol, and prolactin compared with women who previously had at least one full-term pregnancy. These data suggest that circulating pregnancy hormone levels may explain some of the ethnic differences in breast cancer risk.

Estrogen and -Fetoprotein Levels in Maternal and Umbilical Cord Blood Samples in Relation to Birth Weight

Birth weight has been associated with a subsequent risk of breast cancer. The present study examined associations between birth weight and pregnancy estrogens and alpha-fetoprotein (AFP). The concentrations of estradiol, estriol, and AFP were measured in maternal and umbilical cord blood samples from 194 women during pregnancy and at birth. Birth weight was significantly positively correlated with maternal serum estradiol and estriol levels in the 29th week (estradiol: r = 0.16, P = 0.03; estriol: r = 0.29, P = 0.001) and at delivery (estradiol: r = 0.20, P = 0.01; estriol: r = 0.41, P < 0.0001) after controlling for covariates. The umbilical cord estriol level was moderately but significantly correlated with birth weight (r = 0.15, P = 0.049). There was no significant association between umbilical cord serum estradiol and birth weight. There was no significant association between birth weight and maternal serum AFP in any gestational week. Umbilical cord AFP was significantly inversely correlated with birth weight (r = -0.16, P = 0.04). Umbilical cord AFP was unrelated to cord levels of estradiol and estriol. The data suggested a greater exposure to estriol and a lower exposure to AFP among high birth weight babies.

Maternal hormone levels and risk of cryptorchism among populations at high and low risk of testicular germ cell tumors

Cryptorchism is one of the few well-described risk factors for testicular cancer. It has been suggested that both conditions are related to increased in utero estrogen exposure. The evidence supporting the "estrogen hypothesis" has been inconsistent, however. An alternative hypothesis suggests that higher in utero androgen exposure may protect against the development of cryptorchism and testicular cancer. In order to examine both hypotheses, we studied maternal hormone levels in two populations at diverse risks of testicular cancer; Black Americans (low-risk) and White Americans (high-risk). The study population of 200 mothers of cryptorchid sons and 200 mothers of noncryptorchid sons was nested within the Collaborative Perinatal Project, a cohort study of pregnant women and their children. Third trimester serum levels of estradiol (total, free, bioavailable), estriol, testosterone (total, free, bioavailable), sex hormone-binding globulin, alpha-fetoprotein, and the ratios of estradiols to testosterones were compared between the case and control mothers. The results found no significant differences in the levels of testosterone (total, free, bioavailable), alpha-fetoprotein, sex hormone-binding globulin, or in the ratios of estrogens to androgens. Total estradiol, however, was significantly lower in the cases versus the controls (P = 0.03) among all mothers and, separately, among White mothers (P = 0.05). Similarly, estriol was significantly lower among all cases (P = 0.05) and among White cases (P = 0.05). These results do not support either the estrogen or the androgen hypothesis. Rather, lower estrogens in case mothers may indicate that a placental defect increases the risk of cryptorchism and, possibly, testicular cancer.

Multicultural considerations in women's health

As patient practices continue to diversify, clinical skills need to extend beyond disease manifestation and treatment modalities into awareness of health statistics that highlight disparities, training, cross-cultural health care delivery at the individual and system-based levels. and skills of health care advocacy. Excellent care for multicultural women implies the ability to assess the health issues applicable to all women as well as the issues specific to the women in the clinician's office. It implies enabling the patient to share with her individual and cultural influences. Incorporating both of these influences at the same time and integrating them into her context of care can result in developing the best fit for health care goals, eliminating disparities and improving health outcomes in terms of quantity and quality of lives for all women.