Oncogene — A Gene Driving Cancer Growth

In healthy biology, proto-oncogenes govern routine cellular functions, instructing cells when to grow, divide, and stay alive. When a proto-oncogene experiences a mutation, amplification, or rearrangement, it transforms into an oncogene. This alteration produces an abnormally active protein or an excessive amount of normal protein, signalling the cell to proliferate continuously without standard regulatory checks.

Unlike tumour suppressor genes, which act as cellular brakes, an oncogene acts as a stuck accelerator pedal. Even a single faulty copy of the gene can disrupt normal tissue architecture. Consequently, cells evade natural cell death pathways and accumulate further DNA damage, forming tumours and potentially facilitating metastasis throughout the body.

Knowing whether a cancer harbours specific oncogenes shifts care from generalised approaches to personalised medicine. Oncogene status frequently defines an individual's diagnosis, prognosis, and therapeutic options. Instead of relying purely on conventional cytotoxic chemotherapy, clinicians can select treatments tailored to block the exact molecular engine driving the malignancy. This targeted strategy often yields higher response rates while sparing healthy cells, reducing certain side effects and helping patients make well-informed decisions regarding clinical trials and standard treatment pathways.

Oncogenes are detected by examining tumour tissue or circulating tumour DNA via liquid biopsy. Next-generation sequencing panels evaluate dozens or hundreds of cancer genes simultaneously. Polymerase chain reaction assays identify specific point mutations, while fluorescence in situ hybridisation highlights gene amplifications or structural rearrangements. Immunohistochemistry also evaluates the overexpression of proteins produced by these altered genes.

Oncogenes feature prominently across many malignancies. Non-small cell lung cancer commonly involves mutations in the EGFR, KRAS, and ALK oncogenes. Breast cancer frequently exhibits amplification of HER2 (ERBB2). Colorectal cancer regularly presents alterations in KRAS and BRAF, while melanoma is heavily driven by BRAF V600E mutations. Chronic myeloid leukaemia is defined by the BCR-ABL fusion oncogene.

Identifying an oncogene often unlocks targeted therapies such as small-molecule tyrosine kinase inhibitors or monoclonal antibodies. For example, EGFR inhibitors target EGFR-mutant lung tumours, whereas trastuzumab blocks HER2 signalling in breast cancer. When oncogenes mutate further, secondary resistance can emerge, prompting oncologists to switch targeted drugs or combine them with immunotherapy or chemotherapy.