|Year : 2014 | Volume
| Issue : 3 | Page : 506-511
Breast cancer statistics and markers
Mallika Siva Donepudi, Kasturi Kondapalli, Seelam Jeevan Amos, Pavithra Venkanteshan
Department of Biotechnology, Acharya Nagarjuna University, Guntur, Andhra Pradesh, India
|Date of Web Publication||14-Oct-2014|
Department of Biotechnology, Acharya Nagarjuna University, Guntur - 522 510, Andhra Pradesh
Source of Support: University Grants Commission (UGC), New Delhi,
India, Conflict of Interest: None
Breast cancer is one of the familiar diseases in women. Incidence and mortality due to cancer, particularly breast cancer has been increasing for last 50 years, even though there is a lacuna in the diagnosis of breast cancer at early stages. According to World Health Organization (WHO) 2012 reports, breast cancer is the leading cause of death in women, accounting 23% of all cancer deaths. In Asia, one in every three women faces the risk of breast cancer in their lifetime as per reports of WHO 2012. Here, the review is been focused on different breast cancer markers, that is, tissue markers (hormone receptors, human epidermal growth factor-2, urokinase plasminogen activator, plasminogen activator inhibitor, p53 and cathepsin D), genetic markers (BRAC1 and 2 and gene expression microarray technique, etc.), and serum markers (CA 15.3, BR 27.29, MCA, CA 549, carcinoembryonic antigen, oncoproteins, and cytokeratins) used in present diagnosis, but none of the mentioned markers can diagnose breast cancer at an early stage. There is a disquieting need for the identification of best diagnosing marker, which can be able to diagnose even in early stage of breast carcinogenesis.
Keywords: Breast cancer, breast carcinogenesis, markers
|How to cite this article:|
Donepudi MS, Kondapalli K, Amos SJ, Venkanteshan P. Breast cancer statistics and markers. J Can Res Ther 2014;10:506-11
| > Introduction|| |
Cancer has been subsisting from many years, but now it is a major human health problem world-wide. Over the past 50 years, incidence of cancer all through the world has been increased significantly. Among different types of cancers, breast cancer is a heterogeneous and hormone dependent cancer, representing about 22.9%  of total female cancers and it is the second most common type diagnosed in women of developing countries. About one in eight women, one in 1000 men would develop invasive breast cancer over the course of their lifetime.  General risk factors of the breast cancer in females are age, infertility, age of first fulltime pregnancy, age of menopause, an inherited mutation in the BRCA1/BRCA2 breast cancer gene and usage of hormones (estrogen and or progestin) in postmenopausal stage. Cancer incidence increases with roughly the ﬁfth power of elapsed age.  Low and medium resource countries are arguably harder hit by cancer than high resource countries.  Global cancer burden has been estimated that 8.8 million people have died in 2004.  The proportion of cancer incidence represented continental were Africa 28.66%, the America 47.50%, Asia 37.5%, Europe 70.08%, and Oceania 57.5%. Global cancer burden could be increased over time with the increase of population. Aging is the major issue for the future cancer burden. Extrapolation of data from past 50 years shows that cancer incidence rate was constantly increasing from year to year. It could be expected that by the year 2030 the incidence rate would be 26.4 million and 17 million cancer deaths could occur in a year. 
| > Statistics of breast cancer in Asian region|| |
Breast cancer is by far the most frequent cancer among women with an estimated 1.7 million new cancer cases diagnosed in 2012 (23% of all cancers), and ranks second overall (11.9% of all cancers), while mortality has increased by 14%. It is now the most common cancer both in developed and developing regions. Breast cancer ranks as the fifth cause of death from cancer overall.  Overall risk of breast cancer doubles each decade until the menopause, when the increase slows down or remains stable. However, breast cancer is more common after the menopause. Studies of women who migrate from areas of low risk to areas of high risk assume the rate in the host country within one or two generations. This shows that environmental factors are important in the progression of the disease.  According to World Health Organization (WHO) IARC statistics 2012, total breast cancer registries world-wide was given in Graph 1 [Additional file 1] and in specific from Asian continent was given in [Table 1] and total mortality and registries were represented in Graph 2. [Additional file 2] According to Globocan (WHO), for the year 2012, India recorded 70,218 deaths due to breast cancer, more than any other country in the world (second: China - 47,984 deaths and third: US - 43,909 deaths).
| > Carcinogenesis mechanism|| |
Genes involved in cell cycle control are important among those subject to the genetic alterations that give rise to cancer. , The mechanism of cancer development or carcinogenesis, is clearly associated with an increase in cell number, alterations in mechanisms regulating cell proliferation, are only one facet of the mechanisms of cancer. A decreased rate of cell death or apoptosis also contributes to certain types of cancer. Cancer is distinctive from other tumor-forming processes because of its ability to invade surrounding tissues. Tumor genesis is a multistep process, having five rate limiting steps. They are genetic mutations; that dysregulate the activities of genes, which control cell growth, regulate sensitivity to programmed cell death, and maintain genetic stability.
The control of cell division is regulated by a complex interplay of many genes that control the cell cycle, with deoxyribonucleic acid (DNA) replication (S phase) and mitosis as major checkpoints [Figure 1]. Progression through the cell cycle is primarily controlled by cyclins, associated kinases and their inhibitors. Retinoblastoma (rB) and p53 are major suppressor genes involved in the G1/S checkpoint control. Mutation in the tumor suppressor genes such as p53, p16, and p21 lead to the onset of uncontrolled cell proliferation. Inactivation of these negative regulators for a few cell cycles normal checkpoint genes may be activated as oncogenes.  In case of breast cancer CCND1 gene encodes cyclin D1 activated as oncogene. Inactivation of this cyclin D1 function results in irregular cell proliferation. 
|Figure 1: Cancer cell cycle regulation mechanism. Cyclin EAD and B are mytogens and stimulate the cell to proliferate and when complexes with cyclin-dependent kinase (CDKs). Activation or arrest of cell cycle depends on CDK complex. G1 phase can respond to extra cellular signals like hormones and metal ions. p53 play a main role in DNA damage repair. P27 arrest the cell cycle at G1 and cell will enter into resting phase, that is, G0 phase|
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| > Grade and Stage of Tumors|| |
In the clinical setting tumor, grade and stage are important factors that influence the choice of treatment. Tumor stage can be determined depending on tumor size, invasive nature, lymph node involvement and spreading places. The purpose of the staging system is to help organize the different factors and some of the personality features of the cancer into categories in order to understand and for proper treatment. Different stages of breast tumors and their description are given in [Table 2].
Commonly and most widely used breast cancer grading system is TNM system: These three letters represent primary tumor, lymph node involvement and Metastasis respectively. This system has been accepted by Union for International Cancer Control and American Joint Committee on Cancer and used in most of cancer reports [Table 3].
| > Markers for Breast cancer|| |
Molecular markers are used to diagnose the cancer at the early stage and also to determine treatment. In general, they can be classified into tissue markers, genetic markers and serum markers.
Estrogen receptor (ER) and progesterone receptors (PR) are treated as predictive and prognostic markers (as per National Academy of Clinical Biochemistry guidelines). ER-α and PR should be measured in all patients with breast cancer. ER-β has clinical application to detect breast cancer. The primary purpose of measuring these receptors is to identify patients with breast cancer that can be treated with hormone therapy. , In general, recommended assay for ER-α and PR are ligand binding assay, enzyme-linked immunosorbent assay (ELISA) or immunohistochemistry (IHC). ER is alone a relatively weak prognostic factor. , It is important that patients with low ER levels have been reported to respond endocrine therapy. In combination with established prognostic factors, that is, tumor stage, tumor grade, and number of lymph node metastases, ER and PR may also be used for determining short-term prognosis in patients with newly diagnosed breast cancer. ,
Human epidermal growth factor-2 gene
Human epidermal growth factor-2 (HER2) oncogene encodes epidermal growth factor receptor. It is prognosis marker, most useful in node-positive patients but for node-negative patients use of this marker is conflicting.  HER2 should be measured in all patients with invasive breast cancer. The primary purpose of measuring HER2 is to select patients with breast cancer that may be treated with trastuzumab. ,, HER2 may also identify patients that preferentially benefit from anthracycline-based adjuvant chemotherapy. ,,, Two main assays to detect HER2 in breast tumors are immunohistochemical analysis and FISH. 
Urokinase plasminogen activator and plasminogen activator inhibitor
Urokinase plasminogen activator (uPA) and plasminogen activator inhibitor (PAI-1) may be carried out to identify lymph node-negative patients, who are not benefit from adjuvant chemotherapy. Lymph node-negative patients with low levels of both uPA and PAI-1 have a low risk of disease relapse. uPA and PAI-1 should be measured by a validated ELISA using Fresh or freshly frozen tissue extracts. ,,
It is a prognostic marker in breast cancer for only node-negative cases. It can be measured by specific ELISA and prognostic value in node-negative breast cancer validated by meta-analysis. However, assay of cathepsin D was not in clinical use because of conflicting results. ,,
p53 is a tumor suppressor gene, product of this gene is one of the major mechanism to control cancer. Inactivation of this gene leads to overexpression of p53 protein. Though overexpression is seen highly in breast cancer, but is also associated with other tumors making it a poor diagnostic and prognostic marker. ,, p53 can be determined by IHC. It is also used to predict the response to chemotherapy and hormone therapy, but the results are conflicting. 
BRCA1 and BRCA2: Mutation in genetic level of BRCA1 and BRCA2 genes are strong evidence of breast cancer with nearly 40-80% chance of developing cancer. Genetic testing of BRCA mutation is one of the powerful tools for predicting breast cancer.  These two markers are used for identifying individuals who are at high risk of developing breast cancer and ovarian cancer. 
1. Gene expression microarray: Gene expression profiling uses microarray technology to measure the simultaneous expression of thousands of genes. At least eight gene signatures have been described for predicting the outcome in patients with breast cancer. Some of the gene signatures are Amsterdam signature (70 genes), Rotterdam signature (76 genes), reoccurrence score (21 genes), wound response signature (512 genes), genomic grade (97 genes), p53 signature (32 genes) and invasiveness signature (186 genes) used as prognostication in early diagnosis of breast cancer 
2. Oncotype DX TM : Oncotype DX™ is a multigene assay that quantifies the likelihood of breast cancer recurrence in women with newly diagnosed, early stage breast cancer. The Oncotype DX test may be used for predicting recurrence in lymph node-negative, ER-positive patients receiving adjuvant tamoxifen. The Oncotype DX test may also be used to predict benefit from adjuvant chemotherapy (cyclophosphamide-methotrexate- 5-fluorouracil or methotrexate-5- fluorouracil) in node-negative, ER-positive patients, that is, patients with a high recurrence score appear to derive greater benefit from chemotherapy than those with low scores. 
| > Dna ploidy as prognostic marker|| |
DNA ploidy appeared to be a relatively independent factor associated only with histological tumor type. Diploid tumors were slightly better than the survival of those with aneuploidy tumors. Invasive ductal carcinomas turned out to be aneuploid significantly more often than other invasive carcinomas (53% vs. 23%). DNA ploidy of the primary tumor was found to be an independent prognostic factor for operable breast cancer, the prognostic value of DNA ploidy can be improved by the simultaneous use of information on the other tumor characteristic measured by flow cytometry, that is, the rate of cells in S phase of the cell cycle. However, the determination of the rate of cells in S phase in samples obtained from archival tissue specimens is difficult by the excess of debris.  The genetic aberrations range from single nucleotide point mutations and structural chromosomal changes to gross change in chromosome copy number, called aneuploidy. Approximately, 60-80% of breast cancers show clear evidence of an aneuploid DNA content by image and flow cytometry. Amplification of chromosome 11q13 is most frequent in primary breast carcinoma. DNA ploidy analysis may provide interesting global information on the genetic evolution of breast cancer. Because little information is available from premalignant (atypical hyperplasia) and pre-invasive (ductal carcinoma in situ) breast lesions.  The value of DNA ploidy as an independent prognostic factor of breast cancer is still questionable.
CA 15.3, BR 27.29, MCA, CA 549-MUC-1 family, carcinoembryonic antigen (CEA), oncoproteins (e.g. HER2/c-erbB-2) and cytokeratins (e.g. tissue polypeptide antigen and tissue polypeptide-speciﬁc antigen) MUC-1 family proteins, that is, CA15.3, BR 27.29, MCA and CA549 are the most commonly used serum markers. But as they have similar diagnostic sensitivities and speciﬁcities, the use of more than one MUC-1 antigen is unlikely to confer any advantage. ,, However, CEA measurement can provide additional complementary information. For this reason, the combination of one MUC-1 marker and CEA is the recommended serum marker panel in patients with breast cancer. High levels of CA 15.3 (e.g. 150 U/ml) and/or CEA (e.g. 120 ng/ml) in patients thought to have localized disease suggest the presence of unsuspected metastatic disease.
| > Circulating Nucleic acids as cancer markers|| |
DNA is the biochemical substance that specifies all the different parts in living organisms and defines an individual. Cancer is a DNA disease characterized by uncontrolled cell proliferation due to accumulation of genetic alterations; genetic instability has also been recognized as a central biomarker in many forms of cancer. Aberrant methylation can be used as a marker to detect cancer cells. Application of microarray methodology on to carcinoma tissues (breast, colon, or prostate) has resulted in the discovery of response changes in a variety of genes. Application of circulating DNA in plasma in cancer testing depends on the accumulation of genetic and epigenetic changes, such as (1) point mutations, (2) chromosomal rearrangements, (3) microsatellite instability, and (4) hypermethylation.  Circulating N-ras and K-ras gene mutations have been observed in circulating DNA in various cancer forms and persistence of mutated circulating K-ras sequences has been related to recurrence or progressive disease.  Microsatellite instability, particularly loss of heterozygosity (LOH), has been observed both in the tumor itself and in the corresponding circulating DNA.
Circulating cell free DNA (CCFDNA) molecules were first identified in 1948. Majority of the gene sequences of CCFDNA reported in the literature associated with disease (e.g. p53, the Ras family, beta-globin, or beta-actin) are not part of circulating DNA in healthy individuals. Most of the plasma DNA of normal individuals belongs to the Alu repeat family. In healthy individuals, the concentration of circulating DNA is low. The major sources of DNA in the plasma or serum is apoptosis, cell lysis by the necrotic pathway, spontaneous release of newly synthesized nucleic acids, breakdown of blood cells, break down of any pathogens. Molecular weight of circulating DNA may indicate its source, for example: Apoptosis ~ 180 bp and in case of necrosis results in higher molecular weight fragments. The circulating DNA can be detect by modified semi-nested or nested methylation-specific polymerase chain reaction (PCR), multiplex PCR, real-time quantitative PCR, etc., In case of breast cancer, ER-β, 14-3-3 sigma/stratifin, BRCA1 genes are involved in cell cycle and growth.  These genes have been identified as frequently hypermethylated; hence, they are potential targets to be detected in CCFDNA.
Circulating plasma DNA levels in breast cancer patients are significantly higher than in women with benign lesions and in control groups. In addition, circulating DNA levels are reduced after surgery. CCFDNA is associated with tumor size, tumor stage, tumor grade, lymph node involvement, HER2/neu and topoisomerase IIa expression. Similar associations have been found with LOH of circulating DNA at the markers D3S1605, D10S1765, D12S1725, D13S218, and D17S855. LOH of D12S1725, which has been mapped to cyclin D2 and is correlated with shorter overall survival.  List of some commonly used CCFDNA are given in [Table 4].
| > Conclusion|| |
Though a wide range of tumor markers have been identified for breast cancer, but lack of sensitivity and specificity for early diagnosis is the main disadvantage. Consequently, the available markers are of no value in either screening or diagnosing early breast cancer. Few biomarkers of breast cancer progression have been proven to be clinically useful and those are best-validated markers in breast cancer and include ER, PR, HER2, uPA, and PAI-1. Assay of ER, PR, and HER2 is now mandatory for all newly diagnosed breast cancer patients. The measurement of uPA and PAI-1, although technically and clinically validated, , is not presently in widespread clinical use, mainly due to the requirement of a minimum amount of fresh or freshly frozen tissue. Other tumor markers that have been considered as a prognostic marker in breast cancer include erbB2 amplification and overexpression, cathepsin D, and uPAR.  The consensus, however, remains that new prognostic factors that are more precise and reliable are needed.  Some of the emerging tumor markers includes blc-2, ARF, TBX2/3, cyclin D, cyclin E, VEGF, EZH2, hTERT DNA, glycan biomarkers, stem cell markers, topoisomerase IIa, serum autoantibodies, PPIA, PPRDX2, FKBP52, and micro-RNA's. 
| > Acknowledgments|| |
The authors are thankful to University Grants Commission (UGC), New Delhi for providing UGC-MRP research fellowship and also thankful to Acharya Nagarjuna University, Guntur, India for providing the congenial environment and also for extending the lab facilities to carry out this work.
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[Table 1], [Table 2], [Table 3], [Table 4]