Studying hallmarks of cancer
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The key markers and tools you need to study the hallmarks of cancer
In early 2000, Professors Hanahan and Weinberg proposed that when cells progress towards a neoplastic state, they acquire distinctive capabilities1. These were termed hallmarks of cancer and formed a useful framework in which to understand tumor pathogenesis. They include sustaining proliferative signaling, evading growth, suppressors, resisting cell death, enabling replicative immortality, inducing angiogenesis, and activating invasion and metastasis. There were all underpinned by genome instability and mutation.
Later in 2011, they published an update to reflect advances in understanding, and to include reprogramming of energy metabolism, avoiding immune destruction, tumor-promoting inflammation, and evading immune destruction2.
Here we provide the relevant markers and tools to study these important hallmarks of cancer.
Genome instability
| Mechanism | Key markers | Function |
| Nucleotide excision repair | ERCC1-XPF | ERCC1 – XPF is an essential endonuclease for DNA damage repair. It is also involved in DNA interstrand crosslink and double-strand break repair. |
| XPA | XPA is a Zinc finger protein responsible of DNA damage repair. | |
| TFIID | TFIID is a complex that binds to the TATA box in the core promoter of the gene. | |
| Base excision repair | APEX1/APEX2 | APEX are nucleases involved in DNA repair. |
| PNKP | PNKP catalyzes 5’- kinase and 3’ – phosphatases activity | |
| FEN1 | FEN1 is an endonuclease that removes 5’ overhanging flaps in DNA repair. | |
| Double-strand break (DSB) repair | Gamma H2AX | Gamma H2AX is a component of histone octamer in the nucleosome. It is phosphorylated in DNA damage. |
| XRCC4 | XRCC4 functions together with DNA ligase IV and DNA dependent protein kinase to repair DNA DSB. | |
| BRCA1 | BRCA genes are one of the widely studies tumor suppressor proteins that regulate DNA repair and cell cycle | |
| 53bp1 | 53bp1 binds to damaged chromatin and promotes DNA repair. | |
| Kap1 | Kap1 is a key regulator of normal development and differentiation. | |
| DNA mismatch repair | Msh2/Msh6 | Msh2 and Msh6 form MutSα which binds to the site of mismatch base. |
| Msh2/Msh3 | Msh2 and Msh3 form MutSβ which participates in insertion/deletion loop repair. | |
| PMS2 | Forms heterodimers with MLH1 to form MutLα. |
Enabling replicative immortality
| Mechanism | Key markers | Function |
| Telomere maintenance and regulation | hTERT | hTRET is the major component of telomerase activity. Telomerase has been identified as a diagnostic marker for various types of cancer. |
| TRF1/TRF2/POT1/ TIN2/RAP1/TPP1 | The Shelterin complex is a core of six proteins integral for telomere function. | |
| p53 signaling | TP53 (p53) | p53 is called the “guardian of the genome” is the key regulator of gene expression. |
| MDM2 | MDM2 is a proto-oncogene and plays an important p53 regulation. It is the primary inhibitor of p53 transcriptional activation. MDM2 activity is tightly controlled by post translational modifications. | |
| p14ARF/p19ARF | p14ARF is a tumor suppressor gene that that binds to the MDM2-p53 complex and prevent degradation of p53. | |
| E2F-1 | E2F-1 is the transcription factor of the p53 pathway that regulates by initiating transcription of p14ARF. |
Evading growth suppressors
| Mechanism | Key markers | Function |
| Tumor suppressors | Rb1 | Retinoblastoma regulates cell cycle and plays important role in cellular differentiation. |
| TP53 (p53) | p53 is called the “guardian of the genome” is the key regulator of gene expression. It is also an established marker for cancer diagnosis. | |
| APC | APC regulates tumor growth by suppressing Wnt signaling. It also plays an important role in cell adhesion and migration. | |
| BRCA1, BRCA2 | BRCA is one of the widely studies tumor suppressor proteins that regulate DNA repair and cell cycle | |
| PTEN | PTEN is a key regulator of cellular activities. It regulates PI3K-AKT-mTOR signaling through its lipid phosphatase activity. | |
| WT1, WT2 | Wilms tumor protein is a transcription factor important for normal cellular development and survival. WT1 plays both oncogenic role and tumor suppressor. | |
| NF1, NF2 | Neurofibromin is a tumor suppressor that negatively regulates Ras pathway. |
Cell death
Apoptosis is characterized by several features, including cell shrinkage, membrane blebbing, chromosome condensation (pyknosis), nuclear fragmentation (karyorrhexis), DNA laddering and the eventual engulfment of the cell by phagosomes.
Autophagy has an important role in allowing cells to survive in response to multiple stress conditions. Tumor cells exploit this autophagic mechanism as a way to overcome nutrient-limiting conditions and facilitate tumor growth. Autophagy can modulate the tumor microenvironment by promoting angiogenesis, supply nutrients, and modulate the inflammatory response.
Reprogramming energy metabolism
| Mechanism | Key marker | Function |
| Hypoxia | HIF1α/ HIF2a / HIF1β | HIF is a heterodimeric DNA binding transcription factor that regulates a broad range of cellular systems to hypoxia. |
| CAIX | CAIX is a mediator of hypoxia-induced stress response in a cancer cell. | |
| AP-1/c-jun | The AP-1 transcription factor family is known to play an important role in tumor progression and development. | |
| GLUT-1 | GLUT1 levels can be elevated in hypoxia and can be used to indicate the degree of hypoxia. | |
| Glycolysis | Tomm20 | TOMM20 and GAPDH have been shown to be upregulated in various types of cancer and it is necessary to metabolize glutamine. |
| V-ATPase | V-ATPase expression is shown to be upregulated in cancer cells. | |
| GAPDH | GAPDH and Tom20 have been shown to be upregulated in various types of cancer and can be used as a marker. | |
| Mitochondrial metabolism | COX IV | COX IV is used as a marker for the inner mitochondrial marker. |
| VDAC1/Porin | VDAC1/Porin is used as a marker for the outer mitochondrial marker. | |
| ATPase Beta | Beta subunit has a crucial role in the structural and functional maturation of Na+/K+-ATPase. |
Angiogenesis
Growth of the vascular network is important for metastasis as cancer cells require a sufficient supply of nutrients and oxygen, as well as a means of waste removal. This is achieved by angiogenesis and lymphangiogenesis, respectively.
Growth factors, such as VEGF, play a pivotal in angiogenesis, while several other angiogenic factors are linked to tumor aggressiveness.
Learn more about the role of VEGF in angiogenesis
Avoiding immune detection
The human immune system protects against foreign pathogens and diseases, but it also plays a very important role in clearing the body’s own unhealthy and ailing cells. As such, the immune system is also capable of recognizing and eliminating cancer cells.
T cells have the capacity to selectively recognize and kill pathogens or unhealthy cells by orchestrating a coordinated immune response that encompasses but the innate and adaptive responses.
Here we outline various strategies used in immunotherapy
See our pathway that outlines the immune checkpoint pathway
Tumor-promoting inflammation
| Mechanism | Key marker | Function |
| NF-κB signaling | NF-κB | NF-κB is a transcription factor plays an important role in the regulation of cytokines. Dysregulation of NF-κB is linked to inflammatory, autoimmune diseases, and cancer. |
| IKK Beta | IKK beta is part of the IKK complex which is a negative regulator of transcription factor NF-κB. | |
| Tumor-associated macrophages | CD68 | CD68 is a key marker to recognize both M1 and M2 macrophages in tumor tissue. |
| CD163 | CD163 is a scavenger receptor upregulated in macrophages in an anti-inflammatory environment. | |
| iNOS | iNOS is one of the major markers of M1 tumor-associated macrophages. |
Sustaining proliferative signaling
Cell proliferation can be used to assess normal cell health, to measure responses to toxic insult, or as a prognostic and diagnostic tool in several cancers. The available markers typically look at DNA levels or synthesis, cellular metabolism, or proliferation-specific proteins.
For a look at the most common methods to mark and score cell proliferation.
Activation of invasion and metastasis
| Mechanism | Key marker | Function |
| ECM | Hyaluronan | Hyaluronan is glycosaminoglycan found in the extracellular matrix (ECM). HA is dramatically increased in most malignancies. |
| Versican | Versican is either expressed by cancer cell or stromal cells and plays a wide role in invasion and metastasis. | |
| Collagen IV | Collagen IV is essential for tumor angiogenesis by modulating cell growth and proliferation. | |
| Adhesion molecules | CEACAM1 | CEACAM1is down-regulated in several cancers. L-Form CEACAM1 has tumor suppressive function and dysregulation is found in the early carcinogenic process. |
| DCC | DCC is a transmembrane receptor for netrins. It promotes apoptosis in the absence of netrin ligands. | |
| E-Cadherin | E-Cadherin regulates morphogenic process like cell-cell recognition, cytoskeleton regulation, and surface adhesion. | |
| Secreted factors | Tenascin C | Tenascin C interacts with ECM proteoglycans it can interfere with tumor suppressor activity of fibronectin. |
| Fibrinogen | Fibrin deposits occur in the stroma of many cancer types and affect the progression of tumor cells | |
| Periostin | Periostin is a secreted adhesion-related protein expressed in the periosteum and periodontal ligaments and plays a role in tumorigenesis. |
References
1. Hanahan, D. & Weinberg, R. A. The Hallmarks of Cancer. Cell 100, 57–70 (2000).
2. Hanahan, D. & Weinberg, R. A. Hallmarks of cancer: The next generation. Cell 144, 646–674 (2011).