Breast Cancer


1. Breast gland

The mammary gland is derivatives epithelial cells. Anatomical structure of the breast outline composed of fatty tissue, lobes and lobules (glands each consist of 15-25 lobes) which produces liquid milk, and ductus lactiferous glands associated with lobes and lobules that serves the fluid milk, In addition there is also a connective tissue, blood vessels and nodes limphe (Hondermarck, 2003; Bergman et al., 1996). Breast lobules and ducts are very responsive to estrogen because the lobules and ductal epithelial cells express the estrogen receptor (ER), which stimulates the growth, differentiation, development of the mammary gland, and mammogenesis (Van De Graaff and Fox, 1995).
Growth and development of the mammary gland is a series of events involving the interaction of a variety of different types of cells that starts from birth and continues to take place under the influence of the menstrual cycle and gestation process. The series of events is governed by a complex interaction between the various steroid hormones and growth factors, both of cells adjacent to it as well as of the components in the cell environment (growth factors). The stimulation will affect changes in morphology and metabolism. Susceptibility to mammary gland tumorigenesis is influenced by the normal development of the gland itself, which is characterized by a variety of changes in the proliferation and differentiation of breast cells (Guyton and Hall, 1996; Kumar, et al., 2000).
Research shows that endocrine systems that control breast development affects the risk of breast cancer. The balance between proliferation, differentiation and death of mammary gland cells play an important role in the development process. Disturbance in this balance can lead to cancer (Kumar et al., 2000). Some endocrine factors associated with the risk factor is obesity, because in a state of obesity there is increased production of estrogen breast adipase tissue; increased levels of endogenous estrogen in the blood; levels of androstenedione and testosterone in the blood is higher than normal which can be converted into estrogens estrone and then estradiol; increased levels of estrogens and androgens in the urine.
Estrogen is a steroid hormone that gives sexual characteristics in women, affect various organs and tissues of whom are involved in the regulation of cell proliferation and differentiation either in women or men. Estrogen causes breast stromal tissue development, growth extensive duct system, and fat deposits in the breast (Guyton and Hall, 1996). Allegedly excessive exposure of endogenous estrogens in the phase of life of women and may be a factor contributing to the cause of breast cancer (Yager and Davidson, 2006).

2. Breast Cancer

Breast cancer is one type of cancer that has a high enough prevalence. Breast cancer can occur in men and women, it’s just that the prevalence is much higher in women. It is estimated that in 2006 in America, there are 212 920 new cases of breast cancer in women and 1,720 new cases in men, with 40 970 deaths in women and 460 deaths in men (Anonimc, 2006). In Indonesia, breast cancer ranks second after cervical cancer (Tjindarbumi, 1995). Breast cancer incidence in Indonesia amounted to 11% of all cancer incidence (Siswono, 2003).
In general, tumors in the breast originated from epithelial cells, so that most breast cancers are classified as carcinomas (malignant epithelial tumors). While sarcoma, which is a malignancy that departs from the connective tissue, rarely found in the breast. Based on the origin and character of breast cancer histology was grouped into two major groups, namely carcinoma in situ and invasive carcinoma. Carcinoma in situ is characterized by the localization of tumor cells both in ducts or lobular, without invasion through the basement membrane to the surrounding stroma. In contrast to invasive carcinoma, basal membrane will be damaged partially or as a whole and will be able to cancer cells invade surrounding tissue into metastatic cells (Hondermarck, 2003).
Breast cancer is generally in the form of invasive ductal breast cancer is not growing too fast  (Tambunan, 2003). Breast cancer most (approximately 70%) is characterized by the presence of a clot that usually feels pain in the breast, other signs also more rarely in the form of pain in the breast, erosion, retraction, enlargement and itching on the nipple, also overall redness, and possible shrinkage of breast enlargement. While the future may be symptoms of metastatic bone pain, jaundice or even weight reduction (Bosman, 1999). Breast cancer cells can grow into a lump the size of 1 cm 2 within 8-12 years (Tambunan, 2003). In malignant tumors, the lump is solid, hard, irregular, and nonmobile. In more severe cases the skin may occurs edema, redness, and burning sensations in the breast tissue (Lindley dan Michaud, 2005).
The causes of breast cancer are very diverse, but there are a number of risk factors associated with the development of this disease is cigarette smoke, alcohol consumption, age at first menstrual, age at first childbirth, fat on food, and family history of the presence or absence of a family member suffering from this disease (Macdonald dan Ford,1997). Hormones seem to play an important role in the occurrence of breast cancer. Estradiol and progesterone or in the normal menstrual cycle increases the risk of breast cancer. This occurs in breast cancers that have estrogen receptors, which is 50% of breast cancer cases are estrogen-dependent cancer (Gibbs, 2000).
Although the molecular mechanisms that influence the risk of breast cancer occurrence and progression of the disease is not yet known exactly but oncogene activation caused by genetic modification (mutation, amplification or chromosomal rearrangements) or by epigenetic modifications (over-expression) is reported to lead to the multiplication and cell migration. Several oncogenes have been known to affect breast cancer carcinogenesis, including Ras, c-myc, epidermal growth factor receptor (EGFR, erb-B1), and erb-B2 (HER-2/neu) (Greenwald, 2002). Change in the expression and function of tumor suppressor genes such as BRCA1, BRCA2 and p53 not entirely responsible for the high prevalence of spontaneous breast cancer. Mutation or absence of BRCA1 presents in <10% of breast cancers, while the mutation of p53 occurs in over 30% of breast cancer (Bouker et al., 2005).
It is estimated that the development of tumors of the first cellular changes until then visible through mammography takes 6 to 8 years. The change of breast cancer cells into malignant cells that have formed in an environment heterogenisitas in cells. In addition, local inflammation that occurs in the case of breast cancer cells indicates the activity of the immune system and its interaction with the tumor (Hondermarck, 2003).
Detection of breast cancer with mammograms that can be done can sometimes detect tumors at an early stage. Breast cancer stadium can be classified based on the diameter of the tumor, nodal involvement lymphe, and presence or absence of the affected tissue invasion of cancer metastasis. Prognostic factors of breast cancer screening also include lymphe node status, and tumor differentiation conditions, and the presence of estrogen receptors (Macdonald and Ford, 1997).

Initially, the process of breast cancer metastasis initiated by the presence of activation or over-expression of several proteins, for example estrogen receptor (ER) and c-erbB-2 (HER2) which is a breast cancer predisposition protein (Fuqua, 2001; Eccles, 2001). Around 50% breast cancer cases are estrogen-dependent cancer and around 30% cases a positive cancers express HER-2 redundant (Gibbs, 2000). Both of these proteins in addition to a role in metastasis, also plays a role in breast cancer development (early cancer development). Estrogen binds to estrogen receptors (ER) form the active receptor complex and affects the transcription of genes that regulate cell proliferation. Estrogen can stimulate the expression of proteins that play a role in cell cycle progression, such as Cyclin D1, CDK4 (cyclin-dependent kinases4), Cyclin E and CDK2. Activation of estrogen receptor also plays a role in the activation of several oncoprotein as Ras, Myc, and CycD1 (Foster et al., 2001). Activation of this protein led to overgrowth through the activation of another oncoprotein as PI3K, Akt, Raf and ERK. Myc protein is a transcription factor protein that is essential for growth, while CycD1 an important protein in cell cycle progression so that the continuity of the existence of such activation would result in accelerated cancer development (Hanahan and Weinberg, 2000). Estrogen will stabilize the presence of Myc protein. This protein inhibits its own function in the ability to inhibit Cdk2 CKIKIPI (Foster et al., 2001), whereas Cyclin E/Cdk2 complex is responsible for the transition of cells from G1 phase into the S phase (Pan et al., 2002).
In addition, the estrogen receptor complex also will spur tumor suppressor transcription of several genes, such as BRCA1, BRCA2, and p53. However, in patients with breast cancer (which generally are past menopause) genes that have undergone changes as a result of hyperproliferation of breast cells during development, so do not act as they should (Adelmann dkk., 2000; Clarke, 2000). BRCA 1 gene is located on chromosome 17q21, consists of 22 exons and the length is approximately 100 kb. This gene is a tumor suppresor gene. The risk of breast cancer due to mutations in this gene amount 85% and in women under the 50 years of age amount 50%. BRCA 2 gene have a size of 70 kb and consists of 27 exons, located on chromosome 13q12. The risk of breast cancer due to a mutation in this gene by 80-90% in women. P53 gene normally encodes a protein with a molecular weight of 53 kDa that is involved in the control of cell growth. The occurrence of mutations in these genes can lead the cell growth becomes uncontrolled (Gondhowiarjo, 2004). Disappearance of 4p, 4q and 5q in BRCA1 also 7p and 17q24 in BRCA2 can be used to differentiate between breast cancer is caused by hereditary factors or other common causes (Borg, 2005). Mutations in BRCA1 exon 11 deletions are while in BRCA2 is a deletion of exon 12 and 3 (Franks and Teich, 1997).
The results showed that the role of BRCA1 and BRCA2 among them can maintain stableand genetic integrity through its ability to perform homologous recombination.The protein is also involved in the repair of oxidative DNA damage through its interaction with RAD50, RAD51, and other proteins that responds to DNA damage. FunctionBRCA1 in DNA repair proteins associated withGADD45 (Growth Arrest and DNA Damage) which in-upregulation when the overexpression of BRCA1. When DNA damage occurs, it will be separated from her partner of BRCA1, namely CtIP (CtBP-Interacting Protein) that BRCA1 can activate GADD45 that will maintain genomic stability (Wickremasighe and Hoffbrand, 1999).

One model of breast cancer cells that are widely used in research isMCF7 and T47D cells. MCF-7 cells are breast cancer cells obtained from the pleural effusion of a breast adenocarcinoma Caucasian female patient aged 69 years, blood type O, Rh positive.Cells showed differentiation in mammary epithelial tissues including differentiation on the synthesis of estradiol.Basic medium grower MCF-7 cells are formulated Emem media. To obtain a complex mediathen added 0.01 mg / ml bovine insulin and FBS to a final concentration of FBS in the medium C and 5% CO2. Cells to 10%, cells were grown at 37 MCF-7 cell line classified as adherent (ATCC, 2008b) that express the estrogen receptor alpha (ER-α), resistant to doxorubicin (Zampieri dkk., 2002), and do not express caspase-3 (Onuki dkk., 2003; Prunet dkk., 2005). These characteristics distinguish it from other breast cancer cells, such as cells T47D.
T47D breast cancer cells are continuous cell lines such morphologic epithelial cells taken from breast tissue of a 54-year-old woman affected by ductal carcinoma.These cells can be grown in RPMI medium grower base (Roswell Park Memorial Institute) 1640. To obtain a complex medium then added 0.2 U / ml bovine insulin andFoetal Bovine Serum (FBS) to a final concentration of FBS in the medium to 10%. Cells were grown at 37 ° C with 5% CO2. This includes cell adherent cell line (ATCC, 2008a) that express ER-β(Zampieri dkk., 2002) evidenced by the increase in proliferative response as a result of exposure to 17β-estradiol (Verma dkk., 1998). These cells have a doubling time of 32 hours and were classified as susceptible to cell differentiation because it has estrogen receptor +(Wozniak and Keely, 2005). These cells are sensitive to doxorubicin(Zampieri dkk., 2002) and experience missense mutation at residue 194 (in zinc binding domain L2) p53 gene. The L2 loop plays an important role in DNA binding and protein stabilization. If p53 can not bind to the response element on DNA, its ability to cell cycle regulation may be reduced or lost (Schafer et al., 2000). In tumor cells with p53 mutations, known to be a reduction in response to agents that induce apoptosisand tumors are likely to be resistant to antineoplastic drugs that have the destruction of the target DNA(Crawford, 2002).