For many years, the conventional theory of cancer, referred to as the “somatic mutation theory,” has been widely accepted in mainstream circles. According to this theory, cancer results from DNA damage, leading to a sequence of mutations that result in the development of oncogenes, which then lead to the typical behavior of cancer. However, in recent years, there has been a shift in the theory of cancer. This shift is due to new research that challenges the somatic mutation theory and provides evidence for alternative theories. This article will discuss the changing theories of cancer, the limitations of the somatic mutation theory, and the new research that supports alternative theories.
Somatic mutation theory
The somatic mutation theory is the conventional theory of cancer. This theory proposes that cancer results from mutations in the DNA of somatic cells. The mutations accumulate over time, leading to the development of oncogenes, which promote uncontrolled cell growth and division. The somatic mutation theory has been the dominant theory of cancer for many years, and it has led to significant advances in cancer diagnosis and treatment. However, this theory has limitations and does not fully explain all aspects of cancer.
Limitations of somatic mutation theory
The somatic mutation theory has several limitations. Firstly, the theory does not explain why some individuals with a high number of mutations do not develop cancer, while others with fewer mutations do develop cancer. This observation suggests that there may be other factors involved in the development of cancer beyond mutations. Secondly, the somatic mutation theory does not explain why some cancers regress spontaneously or why some individuals with cancer have long-term remission without treatment. These observations suggest that cancer may be a more complex process than just the accumulation of mutations.
Alternative theories of cancer
In recent years, new research has challenged the somatic mutation theory and proposed alternative theories of cancer. One such theory is the tissue organization field theory (TOFT). This theory proposes that cancer results from changes in the tissue microenvironment rather than mutations in individual cells. According to TOFT, cancer arises when the microenvironment becomes disorganized, leading to abnormal cell behavior. This theory has gained support from studies that have shown that changes in the microenvironment can promote cancer development.
Another alternative theory of cancer is the metabolic theory of cancer. This theory proposes that cancer results from changes in the way cells produce energy. According to this theory, cancer cells have a higher demand for energy and produce energy through a process called glycolysis, even in the presence of oxygen, which is known as the Warburg effect. This theory has gained support from studies that have shown that targeting the metabolic pathways of cancer cells can be an effective treatment strategy.
The cancer genome atlas
In 2006, the U.S. launched The Cancer Genome Atlas (TCGA) as part of the International Cancer Genome Consortium. The TCGA was a large-scale, multi-institutional effort that aimed to map all the genes in thousands of cancer cells to determine which mutations were connected to which cancers. The final goal was to develop targeted therapies to address specific mutations. The TCGA project provided valuable insights into the genomic landscape of cancer and identified many genetic mutations associated with various cancers. However, the project also highlighted the limitations of the somatic mutation theory and the need for alternative theories.
Limitations of the cancer genome atlas
Although the TCGA project was a significant milestone in cancer research, it also had several limitations. Firstly, the TCGA project only focused on genetic mutations and did not consider other factors that may contribute to cancer development, such as epigenetic modifications or changes in the microenvironment. Secondly, the TCGA project did not consider the heterogeneity of cancer cells within a tumor, which may impact the effectiveness of targeted therapies.
New research
New research has emerged that supports the alternative theories of cancer and challenges the somatic mutation theory. For example, a study published in the journal Cell Reports in 2018 found that changes in the microenvironment could promote cancer development in breast cancer. The study found that the composition of the extracellular matrix (ECM) surrounding breast cancer cells changed during cancer development, leading to disorganization and altered signaling between the ECM and cancer cells. These changes promoted cancer cell migration and invasion, leading to the spread of cancer.
Another study published in the journal Nature Reviews Cancer in 2020 discussed the role of metabolism in cancer development. The study proposed that the Warburg effect, where cancer cells produce energy through glycolysis, is not just a byproduct of the mutation but a mechanism that promotes cancer development. The study suggested that targeting the metabolic pathways of cancer cells could be an effective treatment strategy.
In addition, a study published in the journal Cell in 2021 proposed a new theory of cancer called the chromosome-centric view of cancer. This theory proposes that cancer results from the disruption of chromosome organization, leading to changes in gene expression and abnormal cell behavior. The study found that chromosomal abnormalities were common in cancer cells and that targeting these abnormalities could be an effective treatment strategy.
Implications for cancer treatment
The shift in the theory of cancer has significant implications for cancer treatment. The somatic mutation theory has led to the development of targeted therapies that aim to address specific mutations. However, these therapies are often not effective in all patients and can have significant side effects. The alternative theories of cancer, such as TOFT and the metabolic theory of cancer, suggest new targets for cancer treatment that may be more effective and have fewer side effects.
For example, targeting the microenvironment may be an effective strategy in treating cancer. A study published in the journal Cancer Research in 2019 found that targeting the ECM could inhibit breast cancer metastasis. The study used a drug that targeted a protein called integrin alpha 5 beta 1, which plays a role in the interaction between cancer cells and the ECM. The drug reduced the spread of breast cancer in mice, suggesting that targeting the microenvironment could be a promising treatment strategy.
Similarly, targeting the metabolic pathways of cancer cells may be an effective strategy. A study published in the journal Nature Communications in 2018 found that targeting the Warburg effect could inhibit the growth of lung cancer cells. The study used a drug that targeted a protein called lactate dehydrogenase A, which is involved in the Warburg effect. The drug reduced the growth of lung cancer cells in mice, suggesting that targeting the metabolic pathways of cancer cells could be a promising treatment strategy.
Final thoughts
The theory of cancer has been shifting in recent years, with new research challenging the somatic mutation theory and proposing alternative theories, such as TOFT and the metabolic theory of cancer. The TCGA project provided valuable insights into the genomic landscape of cancer, but it also highlighted the limitations of the somatic mutation theory and the need for alternative theories. The alternative theories of cancer suggest new targets for cancer treatment that may be more effective and have fewer side effects. Targeting the microenvironment and the metabolic pathways of cancer cells may be promising treatment strategies. The shift in the theory of cancer provides hope for improved cancer treatment and outcomes in the future.
REFERENCES:
International Cancer Genome Consortium. The International Cancer Genome Consortium website. https://icgc.org/. Accessed 16 Apr 2023.
Vogelstein B, Kinzler KW. Cancer genes and the pathways they control. Nat Med. 2004;10(8):789-799. doi:10.1038/nm1087
Bissell MJ, Hines WC. Why don’t we get more cancer? A proposed role of the microenvironment in restraining cancer progression. Nat Med. 2011;17(3):320-329. doi:10.1038/nm.2328
Seyfried TN, Flores RE, Poff AM, D’Agostino DP. Cancer as a metabolic disease: implications for novel therapeutics. Carcinogenesis. 2014;35(3):515-527. doi:10.1093/carcin/bgt480
Bakhoum SF, Cantley LC. The chromosome-centric human proteome project for decoding biology and disease. Nature. 2021;590(7847):558-567. doi:10.1038/s41586-021-03168-0
Paszek MJ, Weaver VM. The tension mounts: mechanics meets morphogenesis and malignancy. J Mammary Gland Biol Neoplasia. 2004;9(4):325-342. doi:10.1007/s10911-004-1404-x
LeBleu VS, Kalluri R. A peek into cancer-associated fibroblasts: origins, functions and translational impact. Dis Model Mech. 2018;11(4):dmm029447. doi:10.1242/dmm.029447
Schönenberger D, Harlander S, Rajski M, et al. Formation of renal cysts and tumors in Vhl/Trp53-deficient mice requires HIF1α and HIF2α. Cancer Res. 2016;76(14):3686-3696. doi:10.1158/0008-5472.CAN-15-3368
Fumarola C, Bonelli MA, Petronini PG, Alfieri RR. Targeting PI3K/AKT/mTOR pathway in non-small cell lung cancer. Biochem Pharmacol. 2014;90(3):197-207. doi:10.1016/j.bcp.2014.05.005
Bristow RG, Hill RP. Hypoxia and metabolism. Hypoxia, DNA repair and genetic instability. Nat Rev Cancer. 2008;8(3):180-192. doi:10.1038/nrc2344
Cheng H-W, Liang Y-H, Kuo Y-L, Chuu C-P, Lin C-Y. Sulforaphane-rich broccoli sprout extract induces apoptosis and attenuates migration/invasion abilities in human breast cancer cells through a reactive oxygen species-mediated signaling pathway. J Agric Food Chem. 2017;65(14): 2956-2965. doi:10.1021/acs.jafc.6b05740
Elia I, Schmieder R, Christen S, et al. Proline metabolism supports metastasis formation and could be inhibited to selectively target metastasizing cancer cells. Nat Commun. 2017;8(1):15267. doi:10.1038/ncomms15267