Cancer treatment has advanced dramatically over recent decades. Chemotherapy, radiation, surgery, immunotherapy, and targeted medicines have helped many patients live longer, and some cancers can now be cured. Yet one major challenge remains: why do some tumours return even after apparently successful treatment?
Part of the answer may lie in a population of tumour cells called cancer stem cells (CSCs).
These cells can renew themselves, produce diverse cancer cell populations, and survive conditions that kill other tumour cells. Researchers believe that stem-like cancer cells contribute to treatment resistance, tumour progression, and recurrence in certain cancers.
Scientists are investigating treatments that disrupt the biological processes that support these cells, including the Wnt/β-catenin, Notch, and Hedgehog signalling pathways.
An important August 2026 review in Signal Transduction and Targeted Therapy examines progress in CSC-targeted medicine and the challenges researchers face in turning laboratory discoveries into effective treatments.
The emerging picture is encouraging but complicated. Cancer stem cells are not necessarily a permanent, easily identifiable cell group. Some cancer cells can acquire or lose stem-like characteristics, making them moving targets.
Understanding this flexibility could reshape the future of cancer treatment.
- Cancer stem cells are tumour cells with stem-like properties, including self-renewal and the ability to generate different cancer cell populations.
- Stem-like cancer cells may contribute to drug resistance, tumour progression, and relapse, although their importance varies across cancers.
- Researchers are investigating Wnt/β-catenin, Notch, Hedgehog, and other signalling pathways as therapeutic targets.
- Researchers are exploring antibodies, immune therapies, metabolic treatments, and combinations with established cancer therapies.
- Some medicines already target pathways associated with cancer stemness, but this does not mean they have been proven to eliminate CSCs.
- As of November 2026, CSC-directed treatments remain an active area of research rather than a broadly established strategy for preventing cancer recurrence.
What Are Cancer Stem Cells?
Cancer stem cells are cancer cells that display biological properties similar to those of normal stem cells.
Two particularly important characteristics are:
Self-renewal: The ability to divide while maintaining the capacity to generate additional stem-like cancer cells.
Differentiation: The ability to produce other cancer cells with different characteristics within the same tumour.
These properties may allow a relatively small cell population to sustain tumour growth over time.
However, identifying cancer stem cells is not as straightforward as identifying a single unique cell type.
Researchers frequently use proteins such as CD44, CD133, EpCAM, and enzymes associated with aldehyde dehydrogenase (ALDH) activity to identify potentially stem-like populations.
The difficulty is that these markers are not exclusive to CSCs. They can also appear on normal cells or cancer cells without strong tumour-initiating capabilities.
Furthermore, cells that do not initially behave like CSCs may later acquire stem-like properties.
A 2025 review in BBA, Reviews on Cancer, emphasises that cancer stemness may be better understood as a dynamic cellular state rather than a fixed identity.
This distinction matters because therapies aimed only at a predefined CSC population may leave behind cancer cells capable of becoming stem-like again.
Why Are Cancer Stem Cells Difficult to Treat?
Cancer therapies work through different mechanisms. Many chemotherapy drugs damage DNA or interfere with cell division, while radiation damages cellular structures and genetic material.
Some CSC-enriched populations can resist these treatments through several biological mechanisms.
1. Cellular Dormancy and Slow Growth
Some cancer cells enter a state called quiescence, in which they divide slowly or temporarily stop dividing.
Because certain chemotherapy medicines work most effectively against actively dividing cells, quiescent cells may be less sensitive to those drugs.
However, not all CSCs are dormant, and not all conventional cancer therapies depend on rapid cell division.
Researchers are investigating how dormant tumour cells survive and what triggers them to become active again.
2. Increased Drug Efflux
Certain stem-like cancer cells express proteins known as ATP-binding cassette (ABC) transporters.
These proteins can move substances, including some anticancer drugs, out of cells.
Examples include ABCB1 (also known as P-glycoprotein) and ABCG2.
When these transporters are highly active, drug concentrations inside cancer cells may decrease, potentially reducing treatment effectiveness.
3. DNA Repair and Protection Against Oxidative Stress
Cancer cells may survive treatment by activating DNA repair systems or increasing their defences against oxidative damage.
In some CSC populations, antioxidant mechanisms involving glutathione and ALDH enzymes can support survival.
These characteristics vary by tumour type and treatment, so they should not be interpreted as universal features of every cancer stem cell.
4. Protection From the Tumour Microenvironment
Cancer cells do not function in isolation.
They interact with blood vessels, immune cells, fibroblasts, extracellular matrix proteins, and signalling molecules in the surrounding tissue.
This surrounding environment, known as the tumour microenvironment, can influence cell survival, inflammation, immune escape, and drug response.
In certain tumours, low oxygen levels and specialised cellular niches help sustain stem-like properties.
The interaction between CSCs and their surroundings is a key focus of ongoing research.
The Three Major Signalling Pathways Researchers Are Targeting
Several molecular pathways involved in normal development and tissue repair are also implicated in cancer stemness.
Researchers are particularly interested in Wnt/β-catenin, Notch, and Hedgehog signalling.
1. Wnt/β-Catenin: Controlling Cell Renewal
The Wnt/β-catenin pathway helps regulate cell growth, differentiation, and tissue maintenance.
When the pathway becomes abnormally activated, it can promote tumour development and help maintain stem-like cancer cell populations.
Wnt signalling is particularly relevant to colorectal cancer biology and is also being studied in other malignancies.
Researchers are investigating experimental drugs, including porcupine inhibitors that interfere with Wnt ligand production.
One challenge is that healthy stem cells also depend on Wnt signalling to maintain tissues such as the intestine.
Blocking the pathway too broadly could therefore harm normal tissues.
The goal is to identify tumours that depend on particular Wnt signals and develop treatments that suppress cancer-associated activity while limiting toxicity.
2. Notch: Regulating Cell Communication
Notch signalling lets neighbouring cells communicate and influence cell fate.
Abnormal Notch activity can contribute to tumour development, survival, and treatment resistance in certain contexts.
Researchers have investigated gamma-secretase inhibitors and other approaches that disrupt Notch signalling.
However, Notch biology is complex. Depending on the cancer type and molecular setting, the pathway can have different roles, including tumour-promoting or tumour-suppressing effects.
This makes careful patient selection essential.
Notch-targeting drugs have been studied in clinical trials, but their effectiveness as broadly applicable CSC-eliminating treatments has not been established.
3. Hedgehog: An Example of an Actionable Cancer Pathway
Hedgehog signalling is essential during embryonic development and supports tissue maintenance.
Abnormal activation of this pathway is particularly important in certain basal cell carcinomas.
Two Hedgehog pathway inhibitors already have established medical uses:
- Vismodegib (Erivedge): Approved in the United States for specified adults with metastatic or locally advanced basal cell carcinoma.
- Sonidegib (Odomzo): Approved for specified adults with locally advanced basal cell carcinoma.
These medicines act on Smoothened (SMO), a component of the Hedgehog signalling pathway.
According to the US National Cancer Institute, both drugs have demonstrated clinical activity in appropriately selected patients.
Sources: NCI, Vismodegib and NCI, Sonidegib.
Important distinction: Their clinical success demonstrates that abnormal Hedgehog signalling can be treated in some cancers. It does not prove that CSCs have been selectively eliminated or that the same approach will work across other cancer types.
New Cancer Stem Cell Research in 2026
Research published in 2026 has placed greater emphasis on cellular plasticity, treatment-resistant states, and the practical barriers to targeting stem-like cancer cells.
August 2026: Translating CSC Discoveries Into Treatments
A comprehensive review published on August 13, 2026, in Signal Transduction and Targeted Therapy, titled Translational insights and clinical challenges of targeting cancer stem cells, evaluated the biological mechanisms and experimental treatments involved in CSC research.
The authors examined multiple potential therapeutic approaches, including small-molecule drugs, antibodies, cellular immunotherapies, and cancer vaccines.
The review identified major obstacles:
- Cancer stem cell populations differ between tumours and between patients.
- Reliable biomarkers are difficult to establish.
- Stem-like and non-stem-like cancer cells can sometimes change states.
- Therapies may affect healthy tissues that depend on the same biological pathways.
- Evidence of CSC depletion in the laboratory does not necessarily translate into improved patient survival.
The authors argue that better models, stronger biomarkers, and carefully designed combination treatments are important for future progress.
Read the research: Translational insights and clinical challenges of targeting cancer stem cells, 2026.
October 2026: Understanding Cancer Cell Plasticity
A review published on October 14, 2026, in Nature Cancer, titled Reframing cancer therapy through tumour plasticity, highlights another major challenge in cancer treatment.
Cancer cells can sometimes change their biological state in response to therapy.
Rather than relying only on new genetic mutations, tumours may temporarily enter drug-tolerant states through changes in gene regulation, cell identity, and signalling activity.
These changes can help some cells survive treatment pressure.
The review proposes that future therapeutic strategies should consider both genetic resistance and reversible cellular states.
This is relevant to CSC research because a treatment that eliminates existing stem-like cells may still fail if other tumour cells subsequently regain stem-like capabilities.
The findings support investigating therapies that interfere with the mechanisms that allow cancer cells to adapt.
However, this publication is a scientific review, not a clinical trial demonstrating a new cancer cure.
Read the research: Reframing cancer therapy through tumour plasticity – Nature Cancer, 2026.
Emerging Strategies for Targeting Cancer Stem Cells
Researchers are investigating several approaches beyond blocking individual signalling pathways.
Antibodies and Antibody-Drug Conjugates
Antibodies can recognise specific proteins on cell surfaces.
An antibody-drug conjugate (ADC) combines an antibody with a potent anticancer drug, potentially delivering treatment preferentially to cells that express a chosen target.
Researchers are exploring whether proteins enriched in CSC populations could provide suitable targets.
The main challenge is specificity. Many potential CSC-associated markers are also present on healthy cells.
Targeting these proteins may therefore damage cells outside the tumour.
Although ADCs are established treatments in certain cancers, ADCs specifically validated to eliminate CSC populations and prevent recurrence remain investigational.
Immunotherapy and Cellular Treatments
Cancer immunotherapy uses components of the immune system to recognise and attack malignant cells.
Researchers are exploring ways to direct immune responses toward CSC-associated proteins.
Potential approaches include engineered T cells, therapeutic vaccines, and antibodies.
However, CSC-targeted immunotherapy faces significant challenges in solid tumours, including inconsistent target expression, immune suppression within the tumour microenvironment, and potential damage to normal tissues.
It is important not to confuse the established benefits of some immunotherapies with proof that those treatments eliminate CSCs.
Targeting Cancer Cell Metabolism
Cells require energy and nutrients to survive.
Some stem-like cancer populations use metabolic pathways differently from other tumour cells.
Researchers are studying mitochondrial metabolism, oxidative stress control, lipid metabolism, and related survival mechanisms.
Disrupting these processes might make some resistant cells more vulnerable to other treatments.
However, cancer cell metabolism varies significantly, and healthy tissues use many of the same biochemical processes.
Therefore, achieving selective toxicity remains difficult.
Epigenetic Therapies
Epigenetics refers to mechanisms that regulate gene activity without changing the underlying DNA sequence.
Epigenetic changes can influence whether tumour cells acquire or maintain stem-like characteristics.
Investigators are examining whether medicines that alter chromatin organisation or gene regulation could disrupt cancer stemness or increase sensitivity to standard therapies.
These approaches are being studied in different cancer settings, but their ability to reliably eliminate CSCs has not been established.
Conventional Cancer Therapy vs CSC-Directed Strategies
Traditional treatment and experimental CSC-directed approaches should not be viewed as competing alternatives.
In many cases, researchers are studying how they might work together.
| Feature | Established cancer treatments | Investigational CSC-directed approaches |
| Primary objective | Remove, destroy, or control malignant cells | Disrupt stem-like tumour cell survival and regeneration |
| Common methods | Surgery, chemotherapy, radiation, targeted drugs, immunotherapy | Stemness pathway inhibitors, specialised antibodies, metabolic and immune approaches |
| Clinical status | Established in defined indications | Mostly experimental as CSC-specific interventions |
| Main challenges | Toxicity, resistance, recurrence, tumour variability | Plasticity, biomarker limitations, off-target effects |
| Long-term benefit | Proven in many cancer settings | Potential benefit requires further clinical validation |
The distinction is important. Conventional treatments already cure some cancers and produce lasting remissions in others.
CSC-directed research aims to improve outcomes where current treatments remain insufficient, rather than replace proven medical care.
Could Combining Treatments Prevent Cancer Recurrence?
One leading research hypothesis is that combining established therapies with interventions targeting cancer stemness could improve long-term disease control.
For example, conventional treatment might reduce overall tumour burden while a second therapy interferes with cellular programs linked to resistance or tumour regeneration.
In theory, this could reduce the likelihood that surviving cancer cells re-establish tumour growth.
However, this strategy faces several practical difficulties.
A CSC-associated pathway may matter in one cancer but be less relevant in another.
A combination treatment might also introduce additional toxicity or fail because tumour cells activate alternative survival mechanisms.
Most importantly, improvements in laboratory measurements of stem-like cells do not necessarily mean patients will have fewer recurrences or live longer.
To demonstrate real clinical benefit, researchers need appropriately controlled studies that assess patient outcomes, including progression-free survival, overall survival, recurrence, and quality of life.
The 2026 review in Signal Transduction and Targeted Therapy reports that the clinical results of CSC-oriented approaches have generally been variable or limited.
This makes the strategy promising, but not yet a broadly validated solution to cancer relapse.
Why Hasn’t CSC Research Produced a Universal Cancer Cure?
Cancer stem cell research faces several fundamental challenges.
Tumour heterogeneity: Different patients and even different regions of one tumour can contain distinct cancer cell populations.
Cellular plasticity: Some cancer cells may transition into stem-like states after treatment.
Unreliable universal markers: No single biomarker accurately identifies all CSCs across every cancer type.
Overlapping biology: Many pathways important for CSC survival are also necessary for normal stem cells.
Insufficient clinical evidence: Laboratory results and animal studies cannot establish that a treatment is safe and effective in humans.
Cancer is not one disease. It includes many biologically distinct conditions, so a universal CSC-targeting drug is unlikely to benefit every patient equally.
The more realistic goal is to identify specific vulnerabilities in particular tumours and develop treatments matched to those characteristics.
The Future: Personalised and More Precise Cancer Treatment
Advances in molecular biology are giving researchers increasingly detailed information about how tumour cells behave.
Several technologies are particularly valuable.
Single-Cell Sequencing
Single-cell sequencing lets scientists examine gene activity in individual tumour cells.
This can help identify populations with stem-like characteristics and investigate how those populations change during treatment.
Spatial Transcriptomics
Spatial transcriptomics reveals patterns of gene expression while preserving information about where cells are located within tissue.
It may help researchers understand how resistant cancer cells interact with blood vessels, immune cells, and other components of the tumour microenvironment.
Patient-Derived Organoids
Organoids are laboratory-grown three-dimensional models that can reproduce selected characteristics of patient tumours.
Researchers use them to study cancer biology and test responses to experimental treatments.
Although promising, organoids do not perfectly replicate the complexity of the human body, and their predictions must be validated clinically.
Better Clinical Trial Design
Future trials may increasingly select patients using molecular biomarkers and assess whether treatments influence mechanisms associated with cancer stemness.
Such trials will need to show not only biological effects but meaningful improvements in patient outcomes.
These technologies may eventually support more individualised treatment approaches, but their clinical usefulness for CSC-directed treatment is still developing.
Conclusion: A Promising Direction, Not Yet a Proven Cure
Cancer stem cell research is helping scientists better understand why some tumours resist treatment and return after apparently successful therapy.
Studies have identified key survival mechanisms, including developmental signalling pathways, metabolic adaptation, protection from the tumour microenvironment, and cancer cells’ ability to change their biological state.
Major research reviews published in 2026 emphasise that these mechanisms may create opportunities for more effective treatment strategies.
However, translating promising laboratory findings into reliable clinical results remains challenging.
The future of CSC-directed cancer treatment will likely depend on identifying the right patients, understanding the specific biology of their tumours, and carefully testing combination treatments.
The most important development is not the discovery of a universal cancer cure, but the growing ability to understand and potentially target the biological processes that allow certain cancer cells to survive.
With continued research and rigorous clinical testing, these discoveries may contribute to safer, more precise, and more durable cancer treatments.
References
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https://www.nature.com/articles/s41392-026-02887-y
2. Shah A. M., Marsh B. P., and de Sauvage F. J. (2026). Reframing cancer therapy through tumour plasticity. Nature Cancer. Published October 14, 2026.
https://www.nature.com/articles/s43018-026-01232-0
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https://www.cancer.gov/about-cancer/treatment/drugs/vismodegib
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https://www.cancer.gov/about-cancer/treatment/drugs/sonidegib
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