Application of Deep Sequencing on Leukemia Clinical Practice: How to Use?
*Molecular Biology Coutinho Department Of Molecular Biology, National Institute Of Cancer (INCA), Brazil
*Corresponding Author: Molecular Biology Coutinho
Department Of Molecular Biology, National Institute Of Cancer (INCA), Brazil Email:email@example.com
Published on: 2016-12-10
The Human Genome Project (HGP) was an international collaborative research with the goal to sequence and map the whole human DNA. It was believed that determining the sequence of the base pairs (A; T; C; and G) on human DNA would allow better understanding of the genetic basis of different diseases, including cancer. The draft of the human genome published in 2001 [1,2] did not ensure us the complete knowledge of diseases; however, it had started an important step to scientific research. The HGP was accomplished with first-generation sequencing (or Sanger sequencing), and this was one of the reasons it took more than 10 years to be completed and cost about $3 billion. The delay and cost of the HGP stimulated the development of new laboratory strategies for genome studies beginning the high throughput DNA sequencing era. The next generation sequencing (NGS) comprises a set of different platforms able to generate large amount of data in short time with high throughput capacity. Currently, there are a number of commercially available NGS machines, each using a particular nucleotide detection system. There are many possibilities of applying NGS into scientific and clinical support, allowing from whole genome sequencing (WGS) or exome (WES) - subset of genome that is protein coding - to the mutational evaluation of target genes [3,4]. Here we will discuss the application of NGS and Sanger sequencing in hematological malignancies, focusing on Chronic Myeloid Leukemia (CML) and Myelodysplastic Syndrome (MDS).
CML is a clonal proliferative disorder of hemopoietic stem cells characterized by a chromosomal translocation which is detectable cytogenetically as the Philadelphia (Ph) chromosome . The translocation forms a novel gene by fusing the BCR gene on chromosome 22 with the ABL proto-oncogene on chromosome 9 (t(9;22) / BCR-ABL). Ph chromosome discovery was the first consistent chromosome abnormality associated with a human cancer. So, either the presence of Ph chromosome identified by karyotype or BCR-ABL gene identified by PCR is sufficient to diagnostic this type of leukemia. CML has a unique place in oncology due to the fact that virtually all patients express the genetic rearrangement formed by reciprocal translocation. It makes BCR- ABL a perfect biomarker, where its presence could be translated to a clinical space. The understanding of CML molecular pathogenesis led to the development of a specific tyrosine-kinase inhibitor (TKI). TKI are small molecules that compete for ATP site on BCR-ABL protein in CML cells. When they are covalently linked in the protein they interrupt the intracellular signaling, leading to cell death by apoptosis .