A team of researchers at Sinai Health and the University of Toronto has identified 90 previously hidden genetic drivers of basal-like breast cancer, the most aggressive and treatment-resistant subtype of the disease, by testing thousands of genes directly inside living tumors for the first time. The findings, published in Nature, open a new map of potential drug targets for a cancer that has long resisted precision therapy because its core molecular drivers were poorly understood.
The study, led by Dr. Daniel Schramek, deputy director of discovery research at Sinai Health and senior investigator at the Lunenfeld-Tanenbaum Research Institute, and Dr. Khalid Al-Zahrani, an assistant professor of molecular genetics at the University of Toronto's Temerty Faculty of Medicine, used a gene-editing approach the team developed specifically for this purpose. The tool, called CRISPR-KOALA, allows researchers to both disable genes and increase their activity inside living animals, rather than relying on cell cultures, which prior research from the same group had shown miss the majority of relevant cancer drivers.
Why This Matters
Basal-like breast cancer, also known as triple-negative breast cancer, accounts for approximately 10 to 20 percent of all breast cancers but carries a disproportionately high mortality burden. It is called triple-negative because the tumors lack the three molecular receptors, estrogen, progesterone, and HER2, that clinicians rely on to target and treat other breast cancer subtypes. Without those receptors, the precision therapies that have transformed survival for hormone receptor-positive and HER2-positive breast cancers have no target to aim at in triple-negative disease.
The consequence is that most triple-negative breast cancer patients are still treated with chemotherapy alone. The five-year survival rate for metastatic triple-negative breast cancer remains among the lowest of any breast cancer subtype. Identifying what is actually driving these tumors at the genetic level is the essential first step toward developing drugs that can hit those targets specifically.
Basal-like breast cancer also disproportionately affects younger women and has a higher incidence in Black women compared to other racial and ethnic groups, making its biological complexity not just a scientific challenge but a health equity issue as well.
What We Know So Far
To map the genetic landscape of basal-like breast cancer, the Toronto team focused on a phenomenon called aneuploidy, a defining feature of this cancer in which entire chromosome arms are gained or lost. Each affected arm carries hundreds of genes, leaving researchers with a long-standing puzzle: which of those genes is actually pushing the cancer forward? Standard approaches, including cell culture experiments, had largely failed to answer this question reliably.
The CRISPR-KOALA system allowed the researchers to screen the mouse equivalents of 3,752 genes located on the ten most frequently altered chromosome arms in basal-like breast cancer, all within immunocompetent mice that have an intact immune system. This in-vivo screening condition is critical because the immune environment shapes tumor behavior in ways that laboratory cell cultures cannot replicate. Ninety percent of the driver genes the team identified were missed by standard cell culture assays, confirming that the living-tumor approach is not merely a refinement but a fundamentally different window into cancer biology.
Of the 90 driver genes identified, 81 had never previously been linked to breast cancer. These genes drive distinct signaling pathways including MAPK, HIPPO, and WNT, reflecting the high degree of genetic diversity within basal-like tumors. One standout candidate is PLGRKT, an oncogene whose tumor-promoting activity is associated with mitochondria that are highly resistant to cellular stress and enhanced ability to neutralize reactive oxygen species, a mechanism that makes tumor cells more resilient and harder to kill with standard therapies.
Where the Impact Is Highest
Triple-negative breast cancer has the highest incidence rates in major U.S. urban centers, and Black women are diagnosed with this subtype at rates approximately two times higher than white women. Cities including New York, Chicago, Detroit, Houston, Atlanta, and Baltimore, which have large Black populations and well-established cancer care centers, are on the frontlines of addressing the disease burden that triple-negative breast cancer places on women of color. The discovery of 81 new driver genes provides a starting map for research institutions in these cities to investigate which drivers are most prevalent in their specific patient populations.
What Doctors and Experts Say
"In many types of breast cancer that have been extensively researched, the five-year survival rate is around 95 percent. Most people survive because we were able to find the genes that drive the cancer," said Dr. Daniel Schramek, who holds the Canada Research Chair in Functional Cancer Genomics. "In this one subset, we don't know what the driver of the cancer is and therefore, it has some of the worst outcomes for patients."
Dr. Khalid Al-Zahrani described the scope of the approach to News-Medical: "This work brought together computational analysis, biotechnology development and functional genomics experiments across a range of mouse and human breast cancer models. Combining all of that enabled us to uncover roles for many genes that we did not know were driving breast cancer and to start thinking about how to tackle BLBC in a targeted way."
Schramek also told Earth.com that these genes "show up in living tumors because of the context that living organisms provide," describing why the cell culture gap matters: the immune system, tumor microenvironment, and the three-dimensional tissue architecture all shape which genes a tumor actually depends on for survival.
What the Evidence Shows and What It Does Not
This is a basic science study published in peer-reviewed Nature, using a novel CRISPR-based screening tool called CRISPR-KOALA applied to immunocompetent mouse models of basal-like breast cancer, with validation across mouse and human breast cancer models.
The study screened 3,752 genes on the ten most frequently altered chromosome arms in this cancer type and identified 90 cancer driver genes, of which 81 were previously unrecognized. The research found that 90 percent of these drivers were missed by standard cell culture assays, establishing in vivo screening as significantly more sensitive.
What the study did not do is test these genes as drug targets in human clinical trials. The translation from identified driver genes to approved therapies typically requires years of additional preclinical work, drug development, and clinical evaluation. PLGRKT is highlighted as an especially interesting target, but no drug targeting it yet exists in clinical testing. Readers should know this is a discovery study that significantly expands the map of triple-negative breast cancer biology, not an announcement of a new treatment.
Who Faces the Greatest Risk
Women diagnosed with basal-like or triple-negative breast cancer, particularly younger women and Black women who face disproportionate risk of this subtype, have the most direct stake in this research. Patients with BRCA1 mutations also primarily develop basal-like tumors, making the new driver gene discoveries relevant to the BRCA1-positive population as well. Patients who have already exhausted standard chemotherapy options and those with metastatic disease have the highest unmet need for the new targeted approaches that discoveries like this may eventually enable.
Symptoms and Warning Signs to Watch For
Basal-like breast cancers are more likely than other subtypes to present as rapidly growing lumps and are more commonly diagnosed in women under 50. Any new breast lump, change in breast shape or skin texture, nipple discharge, or armpit lymph node swelling warrants prompt evaluation by a physician, regardless of mammogram schedule. Women with a family history of breast cancer or a known BRCA1 mutation should discuss their screening protocols with a physician or genetic counselor, as the recommended schedule may differ from standard guidelines.
What You Can Do Now
Patients currently being treated for triple-negative breast cancer should discuss with their oncologist whether genomic profiling of their tumor has been performed, as identifying which of the newly discovered driver genes may be active in an individual tumor could eventually guide enrollment in targeted clinical trials. Comprehensive cancer centers including members of the National Cancer Institute's Comprehensive Cancer Center network are most likely to offer access to genomic profiling and clinical trials relevant to triple-negative disease. Patients can search for trials at ClinicalTrials.gov.
Cost and Access: What Patients Should Know
Standard triple-negative breast cancer treatment with chemotherapy and immunotherapy agents such as pembrolizumab is covered by most insurance plans for approved indications. Genomic profiling of tumors, which may identify enrollment in relevant clinical trials, is also increasingly covered by major insurers. Clinical trial participation typically does not require out-of-pocket payment for investigational treatment and in some cases includes coverage of associated costs. Patients at academic cancer centers are most likely to have access to both comprehensive genomic profiling and trial enrollment.
What Happens Next
The Schramek and Al-Zahrani laboratories will continue investigating which of the 90 newly identified driver genes represent the most actionable drug targets and will pursue preclinical validation of PLGRKT and other high-priority candidates. Further research will also explore how the frequency and combination of these driver genes vary across patient populations, which will be critical for understanding which patients might benefit from therapies targeting specific drivers. MedicalDaily will report on drug development and clinical trial developments as they emerge from this work.
The Bottom Line
The discovery of 90 previously hidden genetic drivers of basal-like breast cancer, using a new CRISPR tool that works directly in living tumors, is a significant scientific advance in understanding one of cancer's most intractable diseases. It does not produce a new treatment today, but it provides the biological map that future drug development will require. For the women most affected by this disease, particularly younger patients and Black women who face a disproportionate burden, this research represents meaningful forward movement in a field where progress has been frustratingly slow.
