Cytogenetic analysis other procedure that has been extensively used for the examination of cancer progression is comparative genomic hybridization (CGH). This Diagnostic technique is capable of discover small-scale copy number reformations (6). Promotion of cancer patterns can be diagnosed since CGH data based on the rates of chromosomal insertions or deletions. It should be a specific area is changed in most specimens of a cancer; it is derived that genetic incident happened initial in the progress of the tumor and was consequently; passed on to its posterity CGH has been used in demonstrating the progress of metastases from the primary place of cancer (7-11).
Other feasible observations in the usage of NGS to clinical tumor samples consist rotation time, the measure of input DNA needed, the necessity for secondary verification and expense (12).
Present opportunities for cancer diagnostics there are some of the exhilarating opportunities for the performance of NGS in a clinical position and, not wonder, there are a great interest and activity in this background. Some of these styles will easily replace current Sanger sequencing or PCR-based Measurement for genetic examination within genes related to familial cancer syndromes or for diagnosis of mutations in genes of therapeutic significance within cancer cells or tissues (13, 14).
The extension of high-throughput sequencing technologies facilitated research laboratories to appraisal disease mechanisms from the DNA sequence to transcriptional regulation and RNA expression. As complicated diseases are likely secondary to global concerns in cellular and physiologic networks, massive reporting of analyses consisted of DNA sequence types, RNA expression levels, and promoter methylation situation might become progressively related for detections and for prediction of a response to medical care. For the clinical science laboratory, the questions of development into these novel areas of nucleic-acid testing are horrific, and will be the probable need the use of numerous supplementary high-throughput sequencing technologies. In this section, we will momentarily elucidate some of the possible usages of NGS technology for clinical diagnosis.
Recently, much genomic research have noticed that the massive complexity of the cancer genome. Genomic profiling utilizing microarray technology could cover the tumors into identical subgroups, offering new clinical understandings for the progress of diagnosis and therapeutic also systematic insights on the basic mechanisms of tumor development. Moreover, the microarray technologies, detonating progresses on sequencing have been designed lately, which is entitled “NGS” (15, 16).
There are several limitations such as, restriction in throughput results and high expensive, it was never feasible to sequence many of genes and specimens. In order to overcome this barrier, novel sequencing technologies were invented. NGS capable sequence thousands of different DNA molecules in a parallel form, which has been lead to high speed and throughput. It can propagate both quantitative and qualitative sequence fidings, tantamount to the data from Human Genome Project (HPG), in several weeks. At the moment, there are multiple NGS platforms commercially accessible: the Illumina Hiseq and Miseq, the Roche 454 GS and Junior version, the personal genome machine Ion torrent, and the Life Technologies SOLiD. A number of NGS platforms, both Miseq and Ion torrent, are more desirable for clinical utilization because of their more pliable throughput and shorter rotation time (17-22). Weigh against to the preceding DNA sequencing of the Sanger method, which is employing dideoxynucleoside termination reaction termed as “first-generation” sequencing, NGS brings into service massively parallel sequencing operation generating hundreds of millions of short ( nearly 200 bp) DNA reads, which can be the sequence a human genome quickly with sorely lower expense. The previous NGS procedure with the single-end read sequencing naturally generates the short-read difficulties, restricting the fidelity of genome alignment. This could be ameliorated by use a paired-end sequencing procedure, permitting significant progresses in determination not only point mutations but also genomic rearrangements, resembling deletions, amplifications, inversions, translocations, and gene-fusions (23, 24). The NGS technology is now separated into sections “second generation sequencing” and “third-generation generation sequencing.” The second generation sequencing concerns to the schemes of short-read arrangement, while the quickly being advanced technology of the third-generation sequencing refers to the single DNA molecule based sequencing. The third-generation procedure has a benefit of less rate of DNA input that permits the emerging context of single cell sequencing (25). Furthermore, there is any stage for PCR amplification, so, the nucleotide incorporation errors can be handled. Anyway, all the platforms of NGS technologies still have limitations in exact base calling and alignment. The errors seem to be platform-related, which enhances the complexity of the data analysis. So, the cost for conformation analysis, instead of the sequencing itself continues to grow, which is referred to as “the $1,000 genomes, the $100,000 analysis” problem (26).