The Hidden Switch That Helps Breast Cancer Survive and Resist Treatment

Breast cancer remains one of the most extensively studied malignancies in modern oncology, yet a stubborn question continues to frustrate researchers: why do tumours that initially respond to therapy so often find ways to survive, spread and come back? A comprehensive review published in Molecular Biology Reports by Bavanilatha Muthiah and colleagues at the Sathyabama Institute of Science and Technology, together with collaborators from Sri Ramachandra Institute and Meenakshi Academy of Higher Education and Research, argues that a major part of the answer lies in a single, remarkably versatile transcriptional network: nuclear factor kappa B, or NF-κB. Far from being a simple on-off switch, NF-κB operates as a context-dependent signalling hub that integrates inflammatory, developmental, metabolic and DNA-damage signals, and in breast cancer its persistent or stimulus-coupled activity can drive proliferation, survival, epithelial-mesenchymal plasticity, invasion and resistance to virtually every class of therapy clinicians currently deploy.

To understand why this pathway has attracted such intense scrutiny, it helps to look at its molecular architecture. In its canonical form, NF-κB dimers—most commonly composed of the p65 (RelA) and p50 subunits—sit idle in the cytoplasm, tethered by inhibitory IκB proteins. When pro-inflammatory cytokines such as tumour necrosis factor alpha or interleukin-1 engage their receptors, a signalling cascade triggers the IκB kinase (IKK) complex, whose regulatory NEMO subunit assembles a ubiquitin-dependent signalosome. IKK then phosphorylates IκBα, marking it for proteasomal destruction and freeing NF-κB to enter the nucleus and switch on hundreds of target genes. The non-canonical arm works differently: NF-κB-inducing kinase (NIK) activates an IKKα-dependent process that processes the precursor p100 into p52, generating RelB/p52 dimers that control a distinct set of genes involved in lymphoid organogenesis, immune cell function and, crucially, tumour-microenvironment communication. The review emphasises that these two arms are not isolated modules but a single integrated system, with feedback loops, shared components such as the fourth IκB protein, and cross-regulation that shapes both the timing and the composition of the transcriptional response.

What makes NF-κB particularly treacherous in breast cancer is that its behaviour varies dramatically across molecular subtypes. The review systematically dissects luminal A, luminal B, HER2-enriched and basal-like or triple-negative disease, showing that the magnitude and biological consequences of NF-κB activation are anything but uniform. In hormone receptor-positive tumours, NF-κB engages in intimate crosstalk with the oestrogen receptor alpha. Landmark work cited in the review demonstrated that an IKKα-dependent transcriptional complex is required for oestrogen receptor-mediated gene activation, meaning that the inflammatory pathway is not merely a parallel route to malignancy but is physically embedded in the machinery that oestrogen-responsive tumours depend upon. This entanglement helps explain why NF-κB activity is repeatedly implicated in endocrine therapy resistance: as tumours evolve under the selective pressure of anti-oestrogen drugs, they appear to lean increasingly on inflammatory signalling to maintain survival programmes that the blocked receptor can no longer fully provide.

In HER2-positive disease, the picture shifts toward cooperation with the HER2-PI3K-AKT axis, one of the most consequential growth-factor pathways in this aggressive subtype. Constitutive activation of PI3K-AKT signalling can potentiate NF-κB-dependent transcription, reinforcing anti-apoptotic gene expression and supporting the survival of tumour cells exposed to HER2-targeted agents. The review also highlights experimental evidence that blocking NF-κB can enhance the responsiveness of mammary tumours to JAK inhibitors, suggesting that inflammatory and cytokine signalling pathways converge in ways that single-agent approaches fail to fully exploit. For triple-negative breast cancer—the subtype with the fewest targeted options—NF-κB assumes an even more central role. Studies using small inhibitory RNAs in oestrogen receptor-negative cell lines showed that suppressing the pathway impairs proliferation and survival, while IKK inhibition with compounds such as BMS-345541 has been reported to suppress breast tumorigenesis and metastasis by targeting GD2-positive cancer stem cell populations, the self-renewing cells widely believed to seed relapse and metastatic spread.

Perhaps the most clinically resonant section of the review concerns epithelial-mesenchymal transition, the cellular reprogramming that allows epithelial tumour cells to acquire motility, invasiveness and stem-like properties. NF-κB has been shown to regulate the expression of key EMT genes in breast cancer cells, effectively serving as a transcriptional gatekeeper for the plasticity that underpins metastasis. This connects directly to the inflammatory cytokine network: interleukin-1 signalling through NF-κB has been shown to be required for tumour invasiveness and angiogenesis in experimental models, and endogenous production of interleukin-1 beta by breast cancer cells has been demonstrated to drive metastasis and colonisation of the bone microenvironment in patient-derived systems. In other words, NF-κB does not merely respond to inflammation—it helps tumour cells manufacture their own inflammatory niche, a self-reinforcing loop that promotes dissemination to bone, the most common site of breast cancer metastasis.

The tumour microenvironment adds another layer of complexity. The review devotes substantial attention to macrophage heterogeneity, describing how tumour-associated macrophages can be co-opted by cancer cells to support growth and immune evasion. Recent work on an unconventional p65/p52 NF-κB module in breast tumour-associated macrophages suggests that these infiltrating immune cells use hybrid canonical-non-canonical signalling to regulate genes that shape the microenvironment in the tumour’s favour. Structural biology is beginning to illuminate how different NF-κB dimer compositions read DNA and activate transcription, with high-resolution studies of p52 homodimer-DNA complexes and NMR analyses of NF-κB-DNA interactions rationalising why specific dimer combinations produce distinct transcriptional outcomes. This structural and mechanistic granularity matters therapeutically: if different dimers control different gene programmes in different cellular compartments, then blunt pathway inhibition risks suppressing beneficial immune functions while sparing the tumour-promoting activities clinicians most want to eliminate.

Genotoxic stress introduces yet another dimension. Chemotherapy and radiotherapy work in part by damaging DNA, yet the review describes how the LUBAC ubiquitin ligase complex promotes linear ubiquitination of NEMO in response to genotoxic stress, activating NF-κB precisely when tumour cells are under attack. This damage-induced NF-κB activity can function as a survival shield, upregulating anti-apoptotic genes and helping cells repair or tolerate the damage inflicted by treatment. Consistent with this, proteasome inhibition with bortezomib has been shown to restore apoptotic factors and sensitise breast cancer cells to docetaxel in preclinical models, and clinical trials have tested bortezomib in combination with capecitabine in metastatic disease and with fulvestrant in hormone receptor-positive tumours resistant to aromatase inhibitors. A related strategy exploits SMAC mimetics, which synergise with endocrine therapy to potentiate antigen presentation and tumour regression in hormone receptor-positive breast cancer, in part by disabling NF-κB-dependent survival pathways.

Therapeutically, the review maps out a spectrum of intervention points, each with distinct trade-offs. Upstream inhibition can target receptor-level signals such as RANK/RANKL, which has attracted attention as a potential prevention target in BRCA1-mutation carriers, with a systematic review and meta-analysis now assessing the prognostic value of RANK signalling across breast cancer populations. Proteasome blockade offers a broad but toxic approach; selective NIK inhibitors are advancing as a more precise way to disable the non-canonical arm; and IKK inhibitors aim at the convergence point of both pathways. The authors also highlight emerging precision-delivery strategies and targeted-degradation concepts, including approaches that could eliminate specific NF-κB subunits rather than merely silencing their activity. Yet the review is notably candid about the translational gap: clinical data remain sparse relative to an enormous preclinical literature, and indiscriminate NF-κB inhibition carries real risks, given the pathway’s essential roles in immunity and inflammation.

The overarching message is one of disciplined optimism. NF-κB is neither a universal villain nor an untouchable guardian; it is a context-dependent network whose contribution to breast cancer depends on subtype, dimer composition, cellular compartment and the surrounding microenvironment. The review proposes a framework for subtype- and context-selective targeting, anchored in biomarker-driven patient stratification rather than blanket suppression. If that framework can be validated, the inflammatory switch that breast cancers exploit to survive, spread and resist treatment may finally become the vulnerability that clinicians have been searching for.

Subject of Research: NF-κB signalling mechanisms, crosstalk and therapeutic targeting in breast cancer

Article Title: Nuclear factor κB signalling in breast cancer: mechanisms, crosstalk and therapeutic targeting

Article References: Muthiah, B., Santha Moorthi Rajah, R. R., Kumar, A. S., Srikesavan, S., Chandrasekaran, V. N., & Priya, K. (2026). Nuclear factor κB signalling in breast cancer: mechanisms, crosstalk and therapeutic targeting. Molecular Biology Reports, 53(1), Article 1687. https://doi.org/10.1007/s11033-026-12871-y

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12871-y

Keywords: NF-κB, breast cancer, canonical pathway, non-canonical pathway, IKK, NIK, HER2, triple-negative breast cancer, tumour microenvironment, therapy resistance, EMT, RANK/RANKL