What causes cancer?
Most cancers are not purely hereditary or only caused by acquired mutations. Many types of cancers are caused by a combination of heredity and the environment. For example, you have an increased risk for skin cancer if you have family history of skin
cancer, but if you never go in the sun, you will be much less likely to develop skin cancer. The mutations acquired from environmental exposure are called somatic mutations. They cannot be passed on to the affected person’s descendants. Somatic
mutations differ from germline mutations, which are inherited. You may inherit germline mutations from your parents which increase your risk for skin cancer. When you go in the sun, you can acquire somatic mutations that increase your total mutation
load, which is the combination of all somatic and germline mutations. Mutation load can be determined by sequencing, such as whole exome sequencing,
and can be a powerful predictor of a person’s risk for developing cancer.
There are two main areas of focus for cancer research: prevention and treatment. Understanding how cancer develops can help researchers find methods for both areas. Cancer research is furthered by cancer genomics research. Genomics research can reveal
biomarkers or genes that indicate risk. Cancer treatment research has two approaches:
tumor profiling and mutation load. A patient’s genotype can provide insight into how a patient might respond to a
specific cancer therapy. If the person’s cancer is at an advanced stage, their tumor may have developed some of its own somatic mutations, which can also affect how a patient might respond to treatment. Tumor profiling is performed using either
whole genome sequencing, or whole genome sequencing of tumor samples to identify mutations in the tumor. Tumor-normal profiling compares the genetic profile of tumor samples to the genetic
profile of healthy tissue samples.
Cancer sequencing methods
Next generation sequencing (NGS) is a massively parallel sequencing technology that can provide valuable insight
into cancer genetics. There are several approaches to using this technology for cancer research. Whole genome sequencing provides
a comprehensive view of the genetic sequence of the sample, whether it be blood, tissue, or tumor. Targeted next generation sequencing focuses
on specific areas of the genome that might be more relevant for cancer. For example, whole exome sequencing provides
insight into protein-coding genes and is especially useful when evaluating mutation load. Hybridization capture panels
can be customized to include non-coding genes that might be relevant to a specific cancer, e.g., leukemia or breast cancer. NGS can include sequencing DNA or RNA. Because RNA defines the way genes are expressed, RNA sequencing can also help
researchers learn more about cancer as it can help isolate unique transcripts and indicate gene expression profiles.