**11. References**

12 Biomarker

patients with CRC (Brittan, et al, 2004 & Loktionov, et al, 2007) . It is presumed that exfoliated colonocytes from healthy colon and neoplastic lesions carry important genetic and epigenetic information that could be utilized for subsequent testing, such as the detection of mutant genes or dysregulated mRNAs, proteins and miRNAs (Loktionov, et al, 2009). It is proposed that even small neoplastic loci can alter colonic cell exfoliation rate and may lead to early detection of these lesions (Loktionov, et al, 2007). The effectiveness of an exfoliated colonocyte based detection system requires an efficient isolation of colonocytes while minimizing the amount of background faecal debris. In order to achieve maximum retrieval of colonocytes, strategies that have been employed include density gradient centrifugation and/or immunoaffinity on either homogenized stool samples or scrapings from the stool surface (Loktionov, et al, 2007). However, cell yields are generally very low, often with conspicuous background debris, which makes cell identification difficult and time consuming (Deuter, et al, 1995). Consequently, such preparations would be unsuitable for high-throughput population screening programs (White, et al, 2009). Furthermore, colonocytes shed from a proximal colonic region travel a longer distance and are more exposed to cytolytic agents, thus making them less likely to be preserved and sampled. If this does prove to be a common problem, stool miRNA markers for right-sided CRC will be less effective. There is evidence, from the work of Koga and Colleagues (Koga, et al, 2010) that this is indeed the case. In this study immunomagnetic beads were conjugated with EpCAM monoclonal antibody to isolate colonocytes from stool. Despite the selection of two highly up regulated miRNAs in CRC cells, the sensitivity of detection was approximately 70% as shown in table 6. However, the detection rate for left sided colonic and rectal tumour was significantly higher, suggesting the potential utility of exfoliated colonocytes based miRNA assay as an alternative to flexible sigmoidoscopy. It is well established that profound deregulation of apoptosis is a characteristic feature of cancer. As a result of apoptosis, tumour specific proteins and genetic information i.e. DNA, RNA and miRNA are released into the lumen of colon (Ahlquist, et al, 2010). Stool environment is much more complex and hostile than plasma, and human RNA are rapidly degraded and only constitute <1% of total stool RNA (Ahlquist, et al, 2010). In contrast with the fast degradation of mRNA, human miRNAs are packed in micro vesicles and are well protected from degradation. The available data indicates that stool miRNA analysis can distinguish

**Tissue Type Studies Participants Target** 

CRC (n= 197) Control (n=119)

CRC (n=10)

Adenoma (n=9)

Control (n=10)

Koga , et al,

Link , et al, 2010

2010

Exfoliated Colonocytes

Faeces

Table 6.

**MiRNAs** 

miR-21

miR-106

**Diagnostic Accuracy Sensitivity %**

Distinguished adenomas and carcinomas from healthy controls P<0.05

miR-17-92 69.5 81.5

miR-135 46.2 95

**Specificity %** 


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**2** 

**Epigenetics in Cancer: The Myelodysplastic** 

Epigenetics is characterized as hereditary changes in gene activity and expression that occur without alteration in DNA genomic sequence. It is known that epigenetics corresponds basically by two majority modifications: DNA methylation and histone modifications. Epigenetics events are reversible without primary DNA base sequence changes, resulting in possible modulation of the gene expression. The accurate DNA modifications and chromatin changes are important to normal embryonic development, to correct tissue cells differentiation, to precise cell cycle progression and cell death control. However, since epigenetics is also crucial to regulate gene expression, uncontrolled and/or incorrect modifications can unbalance the genetic expression profile and result in cellular

The development of cancer cell is frequently associated with sequential of genetic and/or epigenetics hits, resulting in loss- or gain-of-function in genes, which leads to cell transformation. At a glance, aberrant global levels of histone modifications as well as incorrect methylation gene promoter may lead to the silencing of tumor suppressor genes and the activation of proto-oncogenes. Recently, many studies have revealed how epigenetics regulation has an implication in the identification of new biomarkers and the development of new therapies at several types of cancers. Moreover, nowadays, a series of identified epigenetics changes have been used as markers for cancer progression and for

The field of cancer epigenetics is evolving rapidly in many aspects. In myelodysplastic syndrome (MDS), some research groups have been showed the importance to study epigenetic alterations as new diagnostic, prognostic and risk stratification biomarkers. The

**1. Introduction** 

given prognostic value.

transformation from normal to malignant cells.

**Syndrome as a Model to Study Epigenetic** 

**Alterations as Diagnostic and** 

André Mencalha1 and Cecília de Souza Fernandez2

*Bone Marrow Transplantation Center (CEMO) Laboratory Division,* 

**Prognostic Biomarkers** 

Teresa de Souza Fernandez1,

*1National Cancer Institute (INCA),* 

*2Mathematics and Statistics Institute,* 

*Federal Fluminense University (UFF), Niterói, RJ,* 

*Rio de Janeiro, RJ,* 

*Brazil* 

prospective study of patients undergoing colonoscopy. Gastroenterology.2006; 131(5):1400-7.

