The fuel for aggressive breast cancer comes from surrounding tissue, not the tumor itself

Triple-negative breast cancer earns its name the hard way. It lacks the three receptor targets - estrogen, progesterone, and HER2 - that oncologists rely on to treat most breast cancers. It strikes younger women disproportionately, metastasizes faster, and recurs more often. About 20% of all breast cancer cases fall into this category, and for the patients who get this diagnosis, the treatment options are brutally limited.

New research from HSE University's Faculty of Biology and Biotechnology offers a reason for that aggression - and it is not what decades of cancer research might have predicted. The signals fueling tumor growth are not coming from the cancer cells. They are coming from the neighborhood.

Fibroblasts as unwitting accomplices

The research team analyzed gene activity in both tumor cells and their surrounding tissue - the so-called tumor microenvironment - and cross-referenced this data with patient clinical records. They focused on a gene called IGF2, which encodes insulin-like growth factor 2. Under normal circumstances, IGF2 is a routine signaling protein involved in tissue growth and repair. In cancer, it becomes fuel for proliferation.

The surprise was the source. The primary producers of IGF2 were not the cancer cells but fibroblasts - connective tissue cells that normally provide structural support. In a healthy body, fibroblasts are quiet scaffolding. In the tumor microenvironment, they become active suppliers of a growth signal that cancer cells eagerly consume.

A broken containment system

The body does have a built-in brake for this process. A regulatory protein called IGFBP6 acts as a molecular trap for IGF2, binding to it and preventing it from reaching cancer cell receptors. Both the microenvironment cells and the tumor cells themselves produce IGFBP6 - a containment effort from both sides.

But in the most aggressive cases, that containment fails. The researchers found that patients with lower IGFBP6 levels in their tumors showed increased infiltration by macrophages - immune cells that, in established tumors, can undergo a troubling transformation. Rather than attacking cancer, these macrophages begin supporting it. The clinical consequence was measurable: lower IGFBP6 correlated with earlier recurrence.

From risk assessment to potential drug targets

The immediate practical value is in prognosis. Measuring IGFBP6 levels in triple-negative breast cancer could help identify patients at higher risk of early recurrence, allowing clinicians to intensify monitoring and treatment for those who need it most.

The longer-term possibility is therapeutic. "We propose shifting the focus to the tumour microenvironment and targeting the cells that support tumour growth," said Maxim Shkurnikov, who heads the Laboratory for Research on Molecular Mechanisms of Longevity at HSE and co-authored the study. The strategy would involve either boosting IGFBP6 levels artificially or blocking IGF2 production by fibroblasts - depriving the tumor of its external fuel supply.

This is an inversion of the standard oncology playbook, which focuses overwhelmingly on the cancer cells themselves. Conventional chemotherapy targets rapidly dividing cells, and in triple-negative breast cancer, the results are often insufficient. Going after the microenvironment instead is a fundamentally different approach.

What remains uncertain

The study, published in Current Drug Therapy, establishes correlations and proposes mechanisms, but it does not yet deliver a therapeutic intervention. The leap from identifying IGFBP6 as a biomarker to developing a drug that manipulates it safely in patients is substantial. Boosting one protein or suppressing another in the complex ecosystem of the tumor microenvironment carries the risk of unintended consequences - the microenvironment affects wound healing, immune function, and normal tissue maintenance, not just cancer.

The patient data also comes from a single research group, and broader validation across diverse populations and treatment histories would strengthen the findings. The macrophage connection, while clinically suggestive, needs mechanistic work to confirm whether it is causal or merely correlated with poor outcomes.

Still, the core insight - that the most dangerous signals in triple-negative breast cancer originate from bystander cells rather than the tumor itself - reframes the therapeutic challenge. If you cannot target the cancer directly because it lacks the usual receptors, perhaps you can cut off the supply lines instead.