Most cancers are genetically complex and involve a series of patho-genomic DNA mutations or genetic hits. The order of development of these genetic hits is extremely diverse and this diversity in order of development of genomic mutations makes the diagnosis of most types of cancers very much challenging. So, each cancer needs to be treated as a single novel case. So, a new era has arrived when personalized diagnosis of cancer can be offered with development of massively parallel sequencing technology, popularly known as Next- Generation Sequencing. With this technology, it is quite possible to look into the substantial part of the genome of a cancer cell within a very short period of time and at an affordable cost.
Next Generation sequencing represents an effective way for capturing a substantially large amount of genetic information about a cancer. Most Next-Generation Sequencing technologies involve sequencing by synthesis, while other use sequencing by ligation. Each DNA fragment to be sequenced is actually bound to an array. DNA polymerase then adds labeled nucleotides sequentially to it. Then, a high-resolution camera captures the signal from each nucleotide, as it got integrated. The camera also takes notes on the spatial coordinates and time. Then the sequence at each spot can be inferred by a computer program/ software to generate a contiguous DNA sequence, which is termed as read. Multiple Next- Generation Sequencing technology uses different ways to capture the signal and make a read. Illumina GA/Miseq, HiSeq uses fluorescent chemistry, where as Life Technologies Ion PGM, Ion Proton uses semiconductor based chemistry to capture the signal. In nutshell, Next-Generation Sequencing has revolutionized the sequencing and cost has brought down to quite an affordable level, so that it can be implemented in clinical settings for regular diagnostic procedures in molecular pathology lab.