Nutritional risk factors for breast cancer

Cancer patterns in Karachi (all districts), Pakistan: First results (2010-2015) from a Pathology based cancer registry of the largest government-run diagnostic and reference center of Karachi

National level population-based cancer data have never been published from Pakistan in seven decades since independence (1947). Therefore, generation of high-quality regional data becomes highly relevant. Cancer data for the period of 2010-2015 representing the population from all districts of Karachi (14.6 million) are presented herein. After institutional approval (Ref no. IRB-459/DUHS/-14), a Pathology based cancer registry was established at the largest government-run diagnostic and reference center of Karachi. During 2010-2015, a total of 13,508 cancers (including 686 non-melanoma-skin-cancers (NMSC)) were diagnosed. Of these, 5665 (41.9%) were in males while 7843 (58.1%) were in females. Incidence rates for all cancers (excluding NMSC) were 66.7 per 100,000 (crude) and 105.1 per 100,000 (ASR) for males and 112.0 per 100,000 (crude) and 175.8 per 100,000 (ASR) for females. In males, cancer of lip and oral cavity was the most frequently diagnosed cancer (30.8%, ASR 33.1), followed by NMSC (7.7%, ASR 9.5) and colorectum (7%, ASR 7.3). In females, breast cancer was the most frequently recorded malignancy (49.5%, ASR 87.9), followed by lip and oral cavity (11.2%, ASR 22.0) and oesophagus (5.6%, ASR 10.7). We report that Karachi has the highest incidence of cancers of breast, lip and oral cavity, oesophagus and larynx in females and cancer of lip and oral cavity and larynx (2nd only to Turkey) in males compared to any of the Asian populations. Notably, incidence of tobacco associated cancers is very high in Karachi, demanding urgent attention by relevant authorities to address the un-controlled and drastically high consumption of various forms of tobacco in the city.

Association of overweight and obesity with breast cancer in India

Background:

In women, cancer of the breast is one of the most common incident cancer and cause of death from cancer. Anthropometric factors of weight, height, and body mass index (BMI) have been associated with breast cancer risk.

Objectives:

To study the association of overweight and obesity with breast cancer in India.

Materials and Methods:

A hospital-based matched case-control study was conducted. Three hundred and twenty newly diagnosed breast cancer patients and three hundred and twenty normal healthy individuals constituted the study population. The subjects in the control group were matched individually with the patients for their age ±2 years and socioeconomic status. Anthropometric measurements of weight and height were recorded utilizing the standard equipments and methodology. The paired ‘t’ test and univariate logistic regression analysis were carried out.

Results:

It was observed that the patients had a statistically higher mean weight, body mass index, and mid upper arm circumference as compared to the controls. It was observed that the risk of breast cancer increased with increasing levels of BMI. Overweight and obese women had Odd's redio of 1.06 and 2.27, respectively, as compared to women with normal weight.

Conclusions:

The results of the present study revealed a strong association of overweight and obesity with breast cancer in the Indian population.

Prevention of carcinogenesis and inhibition of breast cancer tumor burden by dietary stearate

Previous studies have shown that stearate (C18:0), a dietary long-chain saturated fatty acid, inhibits breast cancer cell neoplastic progression; however, little is known about the mechanism modulating these processes. We demonstrate that stearate, at physiological concentrations, inhibits cell cycle progression in human breast cancer cells at both the G(1) and G(2) phases. Stearate also increases cell cycle inhibitor p21(CIP1/WAF1) and p27(KIP1) levels and concomitantly decreases cyclin-dependent kinase 2 (Cdk2) phosphorylation. Our data also show that stearate induces Ras- guanosine triphosphate formation and causes increased phosphorylation of extracellular signal-regulated kinase (pERK). The MEK1 inhibitor, PD98059, reversed stearate-induced p21(CIP1/WAF1) upregulation, but only partially restored stearate-induced dephosphorylation of Cdk2. The Ras/mitogen-activated protein kinase/ERK pathway has been linked to cell cycle regulation but generally in a positive way. Interestingly, we found that stearate inhibits both Rho activation and expression in vitro. In addition, constitutively active RhoC reversed stearate-induced upregulation of p27(KIP1), providing further evidence of Rho involvement. To test the effect of stearate in vivo, we used the N-Nitroso-N-methylurea rat breast cancer carcinogen model. We found that dietary stearate reduces the incidence of carcinogen-induced mammary cancer and reduces tumor burden. Importantly, mammary tumor cells from rats on a stearate diet had reduced expression of RhoA and B as well as total Rho compared with a low-fat diet. Overall, these data indicate that stearate inhibits breast cancer cell proliferation by inhibiting key check points in the cell cycle as well as Rho expression in vitro and in vivo and inhibits tumor burden and carcinogen-induced mammary cancer in vivo.

Insulin and cancer

Obesity has recently been linked to mortality from the majority of cancers. The insulin/insulin-like growth factor (IGF) system may partly explain this effect. The metabolic syndrome, associated with hyperinsulinemia, may modulate this effect. Recent evidence supports the role of insulin and IGF-1 as important growth factors, acting through the tyrosine kinase growth factor cascade in enhancing tumor cell proliferation. In addition, the metabolic syndrome associated with a chronic inflammatory state and accompanying cytokine abnormalities may also contribute to tumor progression. Growing links between insulin and the etiology as well as prognosis in colon, prostate, pancreatic, and, particularly, breast cancer are reviewed. Of particular concern is the evidence that elevated IGF-1 may interfere with cancer therapy, adversely affecting prognosis. The role of insulin is of concern because of the increasing levels of obesity and the associated metabolic syndrome. Weight gain, through typical Western diet; limited levels of activity; and, more recently, stress-related changes in neuroendocrine function may lead to insulin resistance and hyperinsulinemia. The opportunity for a multidisciplinary approach involving nutrition, exercise, and stress reduction in an integrative setting may be crucial to limiting the insulin-resistant state and improving cancer outcomes.

Glutathione S-transferases (GSTT1 and GSTM1) gene deletions in Tunisians: susceptibility and prognostic implications in breast carcinoma

Glutathione S-transferase Theta1 and Mu1 (GSTT1 and GSTM1) are involved in the metabolism and detoxification of a wide range of potential environmental carcinogens. Conversely, they contribute to tumour cell survival by detoxification of numerous products induced by cancer therapy. The authors designed a large study to investigate the susceptibility and prognostic implications of the GSTT1 and GSTM1 gene deletions in breast carcinoma. The authors used the polymerase chain reaction to characterise the variation of the GSTT1 and GSTM1 genes in 309 unrelated Tunisian patients with breast carcinoma and 242 healthy control subjects. Associations of the clinic-pathologic parameters and the genetic markers with the rates of the breast carcinoma specific overall survival (OVS) and the disease-free survival (DFS) were assessed using univariate and multivariate analyses. A significant association was found between gene deletion of GSTT1 and the risk of early onset of breast carcinoma (OR=1.60, P=0.02). The lack of GSTT1 gene deletion was significantly associated with poor clinical response to chemotherapy (OR=2.29, P=0.03). This association was significantly higher in patients with axillary's lymph node-negative breast carcinoma (OR=12.60, P=0.005). The null-GSTT1 genotype showed a significant association with increased DFS in this selected population of patients. This association was even higher in patients carrying both null-GSTT1 and -GSTM1 genotypes. The gene deletion of GSTs may predict not only the early onset of breast carcinoma but also the clinical response to chemotherapy and the recurrence-free survival for patients with lymph node-negative breast carcinoma.

p53 as a mutagen test in breast cancer

The p53 gene is mutated in about half of all tumors. The p53 gene can be used as a "mutagen test," that is, the relative frequencies of the different types of mutation can be used as an epidemiological tool to explore the contribution of exogenous mutagens vs. endogenous processes in particular cancers. p53 has been used as a mutagen test in breast cancer. Surprisingly, the pattern of p53 mutations differs among 15 geographically and ethnically diverse populations. In contrast, mutation patterns in the human factor IX gene are similar in geographically and ethnically diverse populations. Diverse p53 mutation patterns in breast cancer are consistent with a significant contribution by a diversity of exogenous mutagens. Breast tissue may be uniquely sensitive to lipophilic mutagens because of its unique architecture, characterized by tiny islands of cancer-prone mammary epithelial cells surrounded by a sea of adipocytes. Mammary epithelial cells may be differentially susceptible to released lipophilic mutagens preferentially concentrated in adjacent adipocytes and originating in the diet. To test this hypothesis, we developed a method for measuring mutation load from ethanol-fixed, paraffin-embedded human tissues immunohistochemically stained with anti-p53 antibodies. Single cells staining positively for p53 overabundance are microdissected and the gene is sequenced. It is possible to identify individuals with a high mutation load in normal breast tissue and who are presumably at increased risk for breast cancer. In addition, analysis of the p53 gene with appropriate mutation detection methodology markedly improves the prediction of early recurrence, treatment failure, and death in breast cancer patients. Mutagen tests and mutation load measurements are useful tools to identify the role of mutagens in breast cancer.

Genetic susceptibility to breast cancer in French-Canadians: role of carcinogen-metabolizing enzymes and gene-environment interactions

Breast cancer is the most frequent malignancy among women. Since genetic factors such as BRCA1 and BRCA2 as well as reproductive history constitute only 30% of the cause, environmental exposure may play a significant role in the development of breast cancer. Likewise, the relevant enzymes involved in the biotransformation of xenobiotics (from tobacco smoke, diet or other environmental sources) might play a role in breast carcinogenesis. Since individuals with modified ability to metabolize these carcinogens could have a different risk for breast cancer, we investigated the role of cytochromes P-450 (CYP1A1, CYP2D6), glutathione-S-transferases (GSTM1, GSTT1, GSTP1) and N-acetyltransferases (NAT1, NAT2) gene variants in breast carcinogenesis. A case-control study was conducted on 149 women with breast carcinoma and 207 healthy controls, both of French-Canadian origin. The CYP1A1*4 allele was found to be a significant risk determinant of breast carcinoma (OR = 3.3, 95% CI 1.1-9.7), particularly among post-menopausal women (OR = 4.0, 95% CI 1.2-13.8). The frequency of NAT2 rapid acetylators was increased among smokers (OR = 2.6, 95% CI 0.8-8.2), while the NAT1*10 allele conferred a 4-fold increase in risk among women who consumed well-done meat (OR = 4.4, 95% CI 1.0-18.9). These data suggest that CYP1A1*4, NAT1 and NAT2 variants are involved in the susceptibility to breast carcinoma by modifying the impact of exogenous and/or endogenous exposures.

Prevalence of BRCA1 and BRCA2 mutations in male breast cancer patients in Canada

Men who inherit a mutation in the BRCA2 gene carry a 6% risk of developing breast cancer by the age of 70. The proportion of male breast cancers attributable to BRCA mutations has not yet been determined with accuracy. We studied a series of 14 male breast cancer patients, unselected for family history or ethnicity, who were treated at a single regional cancer center in Canada. Family histories were obtained, and the men were tested for germ-line mutations of BRCA1 and BRCA2. Seven of these patients had a significant family history of breast cancer (i.e., at least one first- or second-degree relative with breast cancer diagnosed before age 70). Two of the men carried BRCA2 mutations, but no BRCA1 mutations were found. Both mutation carriers reported a positive family history and a personal history of cancer that preceded their diagnosis of breast cancer. Our results support the recommendation that male breast cancer patients who have a significant family history of breast or ovarian cancer should be offered genetic counseling and testing.

Genetic counseling for women with an intermediate family history of breast cancer

Women with a family history of breast cancer often over-estimate their personal risk for cancer and may view themselves as candidates for genetic testing even when the likelihood of an informative test result is low. We report here on genetic counseling of women with an intermediate family history of breast cancer, defined as women who have one or more biological relatives with breast cancer but whose pedigree suggests a low likelihood of autosomal dominant transmission. A genetic counseling protocol based on traditional genetic counseling strategies was developed with additional components added to address the needs of women with moderately increased breast cancer risk. These additional components included information about non-genetic risk factors, comparisons of high and moderate risk pedigrees, and evaluation of personal risk based on both genetic and nongenetic risk factors. Most participants liked the genetic counseling and found it useful. At baseline, participants over-estimated both their personal risk of breast cancer and that of the average woman. After counseling, estimates of personal and average risk of breast cancer were lower, although both remained higher than actual risk. Most participants reported that they felt less worried about breast cancer after receiving their personal-risk estimate. At baseline, most women judged themselves to be candidates for genetic testing and expressed interest in testing. The number who considered themselves candidates for testing was reduced after counseling (60% versus 82%) but still constituted a majority. Similarly, interest in testing was partially reduced by counseling (60% versus 91%). We conclude that genetic counseling can help women with an intermediate family history of breast cancer to develop more accurate views of their risk, reduce their breast cancer worry, and aid some of them in developing a more realistic view of genetic testing.

Oxidants and antioxidants in breast cancer

Although a number of risk factors have been identified for breast cancer, mechanisms by which they increase risk of the disease are not clear. Breast cancer etiology could, in part, be related to oxidative stress. Recognized risk factors for breast cancer include a family history of the disease. BRCA1 is needed for post-transcriptional repair of oxidative damage, indicating that oxidative stress may be an important risk factor for women with a family history of the disease. Reproductive and hormonal factors that result in greater exposure to circulating estrogens also increase risk, and steroid hormones are metabolized to reactive quinones and hydroquinones, which can directly damage DNA. Alcohol consumption is associated with increased risk, and the metabolism of alcohol results in production of DNA-damaging reactive oxygen species (ROS). Finally, the inverse relationship noted with consumption of fruits and vegetables could be related to their being a source of antioxidant vitamins. Endogenous factors may play an equally important role in the effects of oxidative stress on breast carcinogenesis. Genetic variability in enzymes that result in increased production of ROS and those that protect the cell from oxidative stress could also have an impact for risk of the disease. In this review, a rationale is given for linking breast cancer risk factors to oxidative stress. The possible role of genetic polymorphisms in a number of enzymes that may be important in affecting levels of ROS to which the cell is exposed, as well as those that protect the cell from oxidative stress, is discussed.

Essential fatty acids, insulin resistance, and breast cancer risk

This review compares the prevalence of hyperinsulinemic insulin resistance in Caucasian-American women with that in Japanese-American and Pima Indian minority groups in the United States. It also examines the differences in breast cancer risk between these ethnic groups and suggests that risk may be modulated by ethnic genetic susceptibility to the effect of the Western diet in precipitating insulin resistance. It is widely agreed that the Western diet with its high saturated fatty acid content and high n-6/n-3 ratio of polyunsaturated fatty acids (PUFAs) favors the manifestation of hyperinsulinemia in individuals who are genetically predisposed. A number of case-control studies have shown hyperinsulinemia to be a marker of increased breast cancer risk, particularly in obese postmenopausal women. Mechanisms that have been postulated include an increased sex steroid level associated with a decreased serum level of sex hormone-binding globulin and an increased bioactive level of insulin-like growth factor I, which may synergize with estrogen in promoting mammary carcinogenesis. Dietary supplements rich in n-3 PUFAs have been shown to inhibit the growth of human breast cancer implants in nude mice, and members of the n-3 PUFA series can inhibit the growth of human breast cancer cell lines in vitro. On the basis of this experimental evidence, some have proposed dietary supplements rich in n-3 PUFAs for breast cancer protection. However, increased consumption of PUFAs requires increased intake of antioxidants. Vitamin E may be the most suitable agent, especially because of its added advantage that in animal models it is reported to reduce the incidence of carcinogen-induced mammary tumors. Preliminary trials of the combination may best be planned as adjuvant treatment after primary surgery for breast cancer, and the insulin hypothesis could be tested in the trials by monitoring fasting insulin and sex steroid levels.

Association between glutathione S-transferase M1, P1, and T1 genetic polymorphisms and development of breast cancer

BACKGROUND

Glutathione S-transferases (GSTs) are encoded by a superfamily of genes and play a role in the detoxification of potential carcinogens. In a nested case-control study, we investigated associations between genetic variability in specific GST genes (GSTM1, GSTT1, and GSTP1) and susceptibility to breast cancer.

METHODS

In 1989, a total of 32 898 individuals donated blood samples to a research specimen bank established in Washington County, MD. Genotypes of blood specimen DNA were determined for 110 of 115 women with incident cases of breast cancer diagnosed during the period from 1990 through 1995 and up to 113 of 115 control subjects. Associations between specific genotypes and the development of breast cancer were examined by use of logistic regression to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

The GSTM1 homozygous null genotype was associated with an increased risk of developing breast cancer (OR = 2.10; 95% CI = 1.22-3.64), principally due to an association with postmenopausal breast cancer (OR = 2.50; 95% CI = 1.34-4.65). For GSTP1, the data were suggestive of a trend of increasing risk with higher numbers of codon 105 valine alleles (compared with isoleucine alleles); a 1.97-fold increased risk of breast cancer (95% CI = 0.77-5.02) was associated with valine/valine homozygosity. The risk of breast cancer associated with the GSTT1 homozygous null genotype was 1.50 (95 % CI = 0.76-2.95). The risk of breast cancer increased as the number of putative high-risk genotypes increased (P for trend <.001) (OR = 3.77; 95% CI = 1.10-12.88 for a combined genotype of GSTM1 null, GSTT1 null, and either GSTP1 valine heterozygosity or GSTP1 valine homozygosity).

CONCLUSIONS

Our findings suggest that genetic variability in members of the GST gene family may be associated with an increased susceptibility to breast cancer.

Fatty acids and breast cancer cell proliferation

We and others have shown that fatty acids are important regulators of breast cancer cell proliferation. In particular individual fatty acids specifically alter EGF-induced cell proliferation in very different ways. This regulation is mediated by an EGFR/G-protein signaling pathway. Understanding the molecular mechanisms of how this signaling pathway functions and how fatty acids regulate it will provide important information on the cellular and molecular basis for the association of dietary fat and cancer. Furthermore these in vitro studies may explain data previously obtained from in vivo animal studies and identify "good" as well as "bad" fatty acids with respect to the development of cancer.

The role of multi-centre cohort studies in studying the relation between diet and cancer

In spite of important progress made during recent decades in nutritional epidemiology methods, many questions about the role of diet in determining cancer risk remain elusive. One example of an unresolved question is whether a high percentage of energy intake in the form of fat (especially saturated fat) is associated with an increased risk of breast cancer. Observations from international correlation and case-control studies support this hypothesis, while results from prospective cohort studies, generally considered less prone to bias, do not. In this paper, we review the advantages and limitations of these different types of epidemiological study design, and discuss how multi-centre studies may help answer some of the unresolved questions about relations between diet, nutritional status, and cancer risk. Multi-centre cohort studies may have the advantage of increased statistical power because of larger variations in individuals' dietary intake patterns and disease risk (as in international correlation studies), while at the same time offering all the possibilities of individual-level studies to model confounding and/or interaction effects.

The molecular epidemiology of p53 gene mutations in human breast cancer

The P53 tumor-suppressor gene is an advantageous tool for analyzing the molecular epidemiology of cancer. We describe the utility of the P53 gene as a 'mutagen test' and a prognostic indicator in breast cancer. Aspects of study design and methodology are discussed. Two major conclusions emerge: (1) there is an extraordinary diversity of mutational patterns among cohorts, hinting that the unique biology of mammary cells results in exposure to high doses of a diversity of ingested lipophilic mutagens; and (2) mutations in the P53 gene predict poor outcome in breast cancer.

Nutrition, hormones, and breast cancer: is insulin the missing link?

Breast cancer incidence rates are high in societies with a Western lifestyle characterized by low levels of physical activity, and by an energy-dense diet rich in total and saturated fat and refined carbohydrates. Epidemiologic studies, so far mostly on postmenopausal women, have shown that breast cancer risk is increased in hyperandrogenic women, with decreased levels of plasma sex-hormone binding globulin, and with increased levels of testosterone and of free estrogens. This paper describes the role of hyperinsulinemia as a physiologic link between nutritional lifestyle factors, obesity, and the development of a hyperandrogenic endocrine profile, and reviews evidence that may or may not support the theory that chronic hyperinsulinemia is an underlying cause of breast cancer. An hypothesis is presented, stipulating that breast cancer risk is increased not only in hyperandrogenic postmenopausal women, but also in premenopausal women with mild hyperandrogenism and normal (ovulatory) menstrual cycles. The author suggests further investigation as to whether there is a positive association between risk of breast cancer before menopause and subclinical forms of the polycystic ovary syndrome (PCOS), and to what extent diet and physical activity during childhood, by modulating the degree of insulin resistance during adolescence, may or may not be determinants of a PCO-like hyperandrogenic endocrine profile persisting into adulthood.

Trends in the incidence of female breast and cervical cancers in Miyagi Prefecture, Japan, 1959-1987

Trends in the incidence of female breast and cervical cancers were examined, using the cancer registry data in Miyagi Prefecture, Japan, during 1959-1987. The age-standardized incidence rate of breast cancer has been increasing, while that of cervical cancer has been decreasing. Age-period-cohort models were applied to clarify the trends in incidence. For breast cancer incidence, the age-period model adequately represented the data, and demonstrated that the risk of developing breast cancer has been increasing in recent time periods. The effect of cohort on breast cancer incidence was insignificant and the full model containing age, period and cohort showed irregularities in the cohort effect. For cervical cancer incidence, the effect of period was significant, while the effect of cohort was marginal. The full model containing age, period and cohort showed that cervical cancer risk has been decreasing in recent time periods and younger birth cohorts. Using published reports, we investigated the trends in the prevalence of various risk factors and compared them with the trends in the incidence at both sites. It is suggested that the effects of period and cohort might be related to the changes in the prevalence of these risk factors as well as to improvements of the diagnostic procedures.