Somatic DNA mutation analysis in targeted therapy of solid tumours

Abstract

Cancer is a disease of the genome with diverse aetiologies including the accumulation of acquired mutations throughout the genome. There has been a flood of knowledge improving our understanding of the biology and molecular genetics of melanoma, lung and colorectal cancer since the genomics era started. Translation of this knowledge into a better understanding of cell proliferation, survival and apoptosis has produced a paradigm shift in medical oncology enabling gene-based cancer treatment (called personalised or precision medicine). Somatic mutation analysis is crucial for a genomics approach since it can identify driver mutations-the "Achilles' heel" of cancer, and support clinical decision-making through targeted therapy. Nevertheless, the applications of somatic DNA testing in cancer face many challenges such as obtaining comprehensive coverage of the cancer genome with limited DNA being available, and delivering an accurate report in a timely fashion without false-negative and false-positive results. Further advances in DNA technologies and bioinformatics will overcome these issues and maximise opportunities for targeted therapy. Somatic mutation analysis will then become an integral part of cancer management for all malignancies.

Keywords: DNA testing; Somatic mutation; cancer genome; clinical implication; multigene analysis; solid tumours; targeted therapy.

Figure 1

Canonical RAS cascades and point-of action of targeted therapies. Membrane-bound tyrosine kinase receptor: e.g., EGFR (epidermal growth factor receptor) and KIT (tyrosine-protein kinase Kit or CD117). Mitogen-activated protein kinase (MAPK) pathway: RAF, rapidly accelerated fibrosarcoma; MEK, mitogen-activated protein kinase kinase; ERK, extracellular signal-regulated kinases. Phophoinositide 3-kinase (PI3K) pathway: PDK, phophosinositide-dependent kinase; AKT, activate protein kinase B. Tyrosine kinase inhibitor (TKI): EGFR inhibitors include gefitinib and erlotinib as the first-generation (reversible anilinoquinazoine and ATP-mimetic), afatinib as the second-generation and AZD9291 and CO-1686 (covalent pyrimidine inhibitors) as the third-generation. KIT inhibitor is imatinib (2-phenyl-amino-pyrimidine derivative). BRAF inhibitor: sorafenib as a pan-kinase inhibitor, vemurafenib, dabrafenib and LGX818 as the selective inhibitor. MEK inhibitor: MEK162, selumetinib and trametinib as the second- and third-generations.