**9. Biomarkers**

118 Breast Cancer – Focusing Tumor Microenvironment, Stem Cells and Metastasis

The role of metalloproteinases (TIMPs) is inhibiting the activity of matrix proteinases (MMPs). As a result, they suppress tumor metastasis. An interesting paradox is that increased TIMPs are associated with progression to metastatic disease in some studies. One proposed explanation is that the balance between MMPs and TIMPs is important than the

Maspin (belonging to the serpin family of serine protease inhibitors) is a tumor suppressor gene which has been established to be involved at least in breast and prostate cancer. Loss of

Kangai 1 (from Chinese kang ai meaning anticancer) or Kai1 is a member of the Transmembrane-4 superfamily of adhesion molecules and is involved in lymphocyte differentiation and function. It was originally described as a metastasis suppressor in prostate cancer but its role has been established as a general suppressor of the metastatic phenotype in many cancer types including breast cancer, although KAI1 does not affect

Breast cancer metastasis-suppressor 1 (BRMS1) decreases metastatic potential of tumor cells, although tumorigenicity do not affected. The mechanism underlying BRMS1 tumor suppression is not yet known, but some data suggest that this role may be mediated by enhanced immune recognition, altered transport, and/or secretion of metastasis-associated

This gene encodes a dual specificity protein kinase that belongs to the Ser/Thr protein kinase family. This kinase is a direct activator of MAP kinases in response to various environmental stresses or mitogenic stimuli. It has been shown to activate MAPK8/JNK1, MAPK9/JNK2, and MAPK14/p38, but not MAPK1/ERK2 or MAPK3/ERK3. This kinase is

A newly opened window in cancer studies is the discovery of microRNAs (mi RNAs). It has been noticed that alteration of non-coding genes, including miRNAs is related to cancer pathogenesis. Mi RNAs modulate the expression of many genes through cleaving mRNA molecules or inhibiting their translation. As a result, they are involved in a variety of physiological and pathological processes, including development, differentiation, cellular proliferation, programmed cell death, cancer initiation and metastasis. It is important to note that a single miRNA can influence the expression of hundreds of proteins. Early studies showed that compared to normal breast human tissues, miRNAs are extensively deregulated in breast tumors. MiRNAs exert their influences at several steps of tumor development and metastasis. Cancer cell adherence, migration, invasion, motility, and angiogenesis are all affected by these modulators. "Metastamir" is the name which has been applied for the class of miRNAs which are involved in metastasis associated processes.

phosphorylated, and thus activated by MAP3K1/MEKK (54).

maspin expression has been established during immunohistochemical studies (51).

expression of each protein (50).

primary tumor growth (52).

**8.6 Role of micro-RNAs** 

**8.2 Maspin** 

**8.3 Kai1** 

**8.4 BRMS1** 

proteins (53).

**8.5 MKK4** 

Identifying biomarkers in early stages of breast cancer as helpful instruments for increasing breast cancer survival has opened an important window in researches. Immunohistochemical testing of tumor samples for estrogen receptor(ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER 2) is a common method which is widely used (56,57). Biomarkers in biological fluids are more useful because they don't need biopsy and invasive methods. Four metabolic biomarkers including Homovanillate, 4-hydroxyphenylacetate, 5-hydroxyindoleacetate and urea have been shown to be different in urine samples of cancer subjects, compared to control group (58). The

Breast Cancer from Molecular Point of View: Pathogenesis and Biomarkers 121

PKC (a family of serine/threonine kinases involved in several cellular signaling pathways including proliferation, differentiation, apoptosis, and migration) is a marker associated with poor prognosis of breast cancer. Although most breast cancers are PKCa -negative, the

S100A4 protein expression appears to be elevated in early and advanced stages of breast cancer compared to normal breast, although its role in different stages of breast cancer seems to be complex. Compared to early stage, S100A4 protein has been observed to down

Aldehyde dehydrogenase 1 (ALDH1) tumor cell expression is an independent predictor of BRCA1 mutation status. Since BRCA1 related breast cancers consist of increased cancer stem cell components, these hereditary tumors shows significantly elevated expression of ALDH1. ALDH1 positive population of breast cancer cells show high tumorigenic capacity through serial passages *in vitro*, compared with A LDH1 negative population. ALDH1 tumor cell expression has been introduced as an independent predictor of BRCA1 mutation status. Furthermore, ALDH1 might be useful as a BRCA1 biomarker and therapeutic target (67). High saturated to monounsaturated fatty acid ratio measured in blood is another indicator associated with breast cancer risk. Low activity or reduced expression of stearoyl-CoA desaturase-1 will result in a decreased breast cancer risk. The suppression of stearoylCoA desaturase expression leads to reduction of cell proliferation and invasion in vitro, and impairs tumor formation and growth which could not be overcome by use of exogenous monounsaturated fatty acids. Since high saturated to monounsaturated fatty acid ratiois related to the activity of this enzyme, it can be used as a new marker to assume breast

Since SCD-1 expression is regulated by dietary and lifestyle factors, new nutritional

Newly introduced Metastamirs assume to be useful biomarkers for prediction of progression and prognosis of breast cancer and in identification of the novel targets for

Taken together, our knowledge about molecular pathways involved in breast cancer and prognostic and diagnostic markers are much more than before, although many works

[2] Rodriguez A.O., Chew H., Cress R., Xing G., McElvy S., Danielsen B., et. Al. Evidence of

poorer survival in pregnancy associated breast cancer. Obstetrics and Gynecology

http://www.uptodate.com/contents/epidemiology-and-risk-factors-for-breast-

[4] Park N.J., Kang D.H., Weaver N.T. Objective and Subjective Breast Cancer Risk. Cancer

strategies for cancer prevention could be focused on SCD1 function (68).

therapeutic intervention in future breast cancer diagnosis and treatment (55).

http://www.uptodate.com/contents/an-overview-of-breast-

cancer?source=search\_result&selectedTitle=1~150

small PKCa-positive ratio shows more aggressiveness (65).

regulate in more advanced stages of breast cancer (66).

cancer risk, although more studies should be done.

remain to be done.

**10. References** 

2008;112(1):71-8

cancer?source=see\_link

Nursing 2010; 33(6):411-20

[1] Uptodate.

[3] Uptodate.

intraductal sampling including samples of nipple aspiration, ductal lavage, and duct endoscopy, is newly used for direct access to the microenvironment surrounding the breast cells that are undergoing malignant transformation (59).

Serum antigens and autoantibody profiling is another approach for early detection and diagnosis of breast cancer. Elevation in level of two antigens, CA 15-3 and CA 27.29, has been reported. Another way is detection of serum autoantibodies against tumor suppressor genes. Studying the changes appeared in level of several autoantibodies instead of only one antibody appears preferable to achieve more accuracy.

BRCA1/2 mutation or functional losses are the other markers will likely serve as a useful predictive biomarker for diagnosis as well as of response to treatment with PARP inhibitors. REGγ (also known as PA28γ, PSME3 or Ki antigen) is a member of the REG or 11S family of proteasome activators which bind to 20S proteasome and facilitate the related degradation of its intracellular protein substrates. REGγ is one of the potential markers in breast cancer whose expression is associated with breast cancer development and the presence of ER, CerBb-2 and lymph node metastasis. It has been reported that REGγ could facilitate the growth of breast cancer cells. Abnormal high expression of REGγ has been observed in breast cancer and its metastatic lymph nodes (60).

BCL2 has been introduced as an independent biomarker for prognosis of all types of earlystage breast cancers. Immunohistochemical studies have been introduced BCL2 expression as a new diagnostic instrument in breast cancer studies although further work should be done to ascertain the exact way to apply BCL2 testing for risk estimation and to find a standard protocol for BCL2 immunohistochemistry (61).

Ki-67, MI, PCNA, and LI have been reported as markers for poor prognosis, although the most important one has not been established yet (62). Serum associated tumor markers have been newly introduced for breast cancer diagnosis. Carbohydrate antigen (CA) 15-3 and carcinoembryonic antigen (CEA) are the most well-known markers. The noticeable point is that the elevation of CA 15-3 between 4 and 6 weeks after initiation of a new therapy, i.e. spurious early rise (surge), indicates poor prognosis. However, American Society of Clinical Oncology (ASCO) guidelines don't recommend CA 15-3 alone as a marker for either diagnosis or detection of early recurrence of breast cancer. CEA expression level has been not also confirmed as a marker for diagnosis or routine surveillance after primary therapy. The ASCO recommend CEA level measurement as supplementary information (63).

Overexpression of cathepsin B (CTSB) - which is involved in proteolytic pathways that lead to the degradation of ECM proteins - and caveolin-1 (cav-1) - which is correlated with increased expression of RhoC and resultant increase in cell motility and invasion - have been established in Inflammatory breast cancer (IBC) compared to non-IBC tissues. Furthermore, CTSB expression level has shown a significant positive correlation with the number of positive metastatic lymph nodes in IBC (and not in non-IBC patients). IBC is the most invasive and fatal form of primary breast cancer, the 3-year survival rate for this kind of breast cancer is 40% which compared to 85% for non- IBC, is very poor. Distinct clinical features of this form include a rapid onset, erythema, edema of the breast and a "peaud' orange" appearance of the skin. High metastatic behavior, rapid invasion into blood and lymphatic vessels and formation of tumor emboli within these vessels are also major characteristics of IBC which make this form the most dangerous kind of breast cancer (64).

MTDH/AEG-1overexpression or genomic amplification can also be used as biomarker to identify subgroups of patients with requirement for more aggressive treatment, although more studies should be done (40).

PKC (a family of serine/threonine kinases involved in several cellular signaling pathways including proliferation, differentiation, apoptosis, and migration) is a marker associated with poor prognosis of breast cancer. Although most breast cancers are PKCa -negative, the small PKCa-positive ratio shows more aggressiveness (65).

S100A4 protein expression appears to be elevated in early and advanced stages of breast cancer compared to normal breast, although its role in different stages of breast cancer seems to be complex. Compared to early stage, S100A4 protein has been observed to down regulate in more advanced stages of breast cancer (66).

Aldehyde dehydrogenase 1 (ALDH1) tumor cell expression is an independent predictor of BRCA1 mutation status. Since BRCA1 related breast cancers consist of increased cancer stem cell components, these hereditary tumors shows significantly elevated expression of ALDH1. ALDH1 positive population of breast cancer cells show high tumorigenic capacity through serial passages *in vitro*, compared with A LDH1 negative population. ALDH1 tumor cell expression has been introduced as an independent predictor of BRCA1 mutation status. Furthermore, ALDH1 might be useful as a BRCA1 biomarker and therapeutic target (67). High saturated to monounsaturated fatty acid ratio measured in blood is another indicator associated with breast cancer risk. Low activity or reduced expression of stearoyl-CoA desaturase-1 will result in a decreased breast cancer risk. The suppression of stearoylCoA desaturase expression leads to reduction of cell proliferation and invasion in vitro, and impairs tumor formation and growth which could not be overcome by use of exogenous monounsaturated fatty acids. Since high saturated to monounsaturated fatty acid ratiois related to the activity of this enzyme, it can be used as a new marker to assume breast cancer risk, although more studies should be done.

Since SCD-1 expression is regulated by dietary and lifestyle factors, new nutritional strategies for cancer prevention could be focused on SCD1 function (68).

Newly introduced Metastamirs assume to be useful biomarkers for prediction of progression and prognosis of breast cancer and in identification of the novel targets for therapeutic intervention in future breast cancer diagnosis and treatment (55).

Taken together, our knowledge about molecular pathways involved in breast cancer and prognostic and diagnostic markers are much more than before, although many works remain to be done.
