Background

The discovery of Breast Cancer Susceptibility Gene 1/2 (BRCA1/2) represents a pivotal moment in the history of cancer genetics, fundamentally altering the paradigm of tumor biology. Initially identified in the early 1990s through pedigree analysis of familial breast cancer patients, these genes were initially viewed primarily as diagnostic tools for predicting the risk of hereditary cancers. However, the realization that BRCA proteins are critical components of the Homologous Recombination (HR) pathway, which repairs Double-Strand Breaks (DSB) in DNA, heralded the dawn of precision medicine. Conventional chemotherapy indiscriminately attacks both normal and cancer cells, causing severe side effects in patients. Consequently, there was a growing need for companion diagnostics and therapeutic strategies that selectively target specific genetic vulnerabilities in cancer cells. Research aimed at elucidating the functional loss of BRCA genes laid the theoretical foundation for precision-targeted therapies that exploit these vulnerabilities.

Key Findings

The recently published BRCA Focus in Nature Genetics provides a comprehensive overview of the genetic research conducted over the past 30 years, along with the latest challenges. A notable achievement is the development of Poly (ADP-ribose) Polymerase (PARP) inhibitors, which target the Achilles' heel of BRCA-deficient cancer cells. While normal cells can survive even when specific DNA repair pathways are blocked by activating alternative pathways, BRCA-mutated cancer cells, which already have impaired homologous recombination function, are killed when PARP is also inhibited. This drug development, based on the 'Synthetic Lethality' mechanism, has led to the approval of several targeted anticancer agents, starting with Olaparib. However, clinical practice faces new challenges, including overcoming drug resistance and interpreting Variants of Uncertain Significance (VUS). A significant proportion of genetic tests reveal VUS, making it difficult to determine whether a BRCA gene mutation actually causes cancer. Recently, the combination of Next Generation Sequencing (NGS) technology and gene editing techniques has enabled the development of Multiplexed Assays of Variant Effect (MAVE), which simultaneously validates the function of thousands of variants, thereby improving diagnostic accuracy. Furthermore, various drug resistance mechanisms have been identified, including cancer cells acquiring additional mutations in BRCA genes to restore their own repair function. Researchers are using single-cell analysis and molecular modeling to design combination therapies that block these bypass pathways in cancer cells early on. Finally, this special issue highlights the global health disparities that arise from the lack of genomic data from non-European populations, including those in Asia and Africa.

Significance and Prospects

The 30-year history of BRCA research demonstrates how genetic discoveries can lead to new drugs that actually save patients' lives. It has been hailed as a model case of how to usher in an era of personalized precision medicine that treats cancer based on genetic mutations rather than by organ of origin. As the analysis of tumor genomic mutation profiles becomes more widespread, the area of targeted therapies that target BRCA mutations is expected to continue to expand beyond breast and ovarian cancer to include prostate and pancreatic cancer. However, the high cost of NGS testing and expensive drugs pose barriers for patients in low-income countries, limiting the realization of true personalized medicine. If screening infrastructure for non-European populations is not expanded, the benefits of precision medicine will inevitably be concentrated in certain countries or social classes. Future challenges lie not only in improving the technical sophistication of scientific discoveries but also in distributive justice, which involves equitably sharing accumulated data with patients worldwide.