The Core Hallmarks of Cancer
The core hallmarks of cancer are six fundamental biological capabilities that cells acquire during malignant transformation: sustaining proliferative signaling, evading growth suppressors, resisting cell death, enabling replicative immortality, inducing angiogenesis, and activating invasion and metastasis 1.
The Original Six Hallmarks
These six capabilities represent the essential alterations in cell physiology that collectively dictate malignant growth 1:
- Sustaining proliferative signaling: Cancer cells generate their own growth signals or become hyperresponsive to normal growth signals, allowing uncontrolled proliferation
- Evading growth suppressors: Tumor cells circumvent mechanisms that normally limit cell proliferation, such as tumor suppressor pathways
- Resisting cell death: Cancer cells develop mechanisms to avoid apoptosis and other forms of programmed cell death
- Enabling replicative immortality: Malignant cells bypass normal limits on cellular replication, often through telomerase activation
- Inducing angiogenesis: Tumors stimulate new blood vessel formation to sustain nutrient and oxygen supply
- Activating invasion and metastasis: Cancer cells acquire the ability to invade local tissues and spread to distant sites
Enabling Characteristics
Two fundamental enabling characteristics underlie the acquisition of these hallmarks 1:
- Genome instability and mutation: Generates the genetic diversity that facilitates hallmark acquisition
- Tumor-promoting inflammation: Fosters multiple hallmark functions through immune cell recruitment and inflammatory signaling
Emerging Hallmarks
Two additional emerging hallmarks have been identified as having potential generality across cancer types 1:
- Reprogramming energy metabolism: Cancer cells alter their metabolic pathways, often favoring glycolysis even in oxygen-rich environments
- Evading immune destruction: Tumors develop mechanisms to avoid recognition and elimination by the immune system
Recent Expansions of the Framework
The most recent synthesis expands this framework further 2, 3. Additional dimensions now include phenotypic plasticity and disrupted differentiation as a discrete hallmark capability, nonmutational epigenetic reprogramming as an enabling characteristic, and polymorphic microbiomes as another enabling feature 3. Senescent cells have also been recognized as functionally important cell types within the tumor microenvironment 3.
Clinical Relevance
These hallmarks provide more than just a conceptual framework—they represent targetable vulnerabilities. Each hallmark capability arises through sequential acquisition of somatic mutations, some of which enable these characteristic traits 4. Understanding that tumors with complex subclonal structures tend to be more aggressive and resistant to therapy 4 emphasizes why hallmark-based therapeutic strategies targeting multiple capabilities simultaneously may offer superior clinical outcomes 2.
Important Caveats
The hallmarks should not be interpreted as applying uniformly to all cancer cells within a tumor or equally at all times 5. Cancer is an evolving, dynamic, and heterogeneous system with complex networks of interrelations between oncogenic events, signal transduction programs, and hallmark manifestations that vary between cells and over time 5. This heterogeneity partially explains treatment resistance and supports the rationale for simultaneous, multi-target therapeutic approaches 5.