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The chromosomal theory of cancer is a fundamental concept in cancer biology that suggests cancer is caused by genetic changes, particularly alterations in the structure or number of chromosomes in cells. These changes can lead to uncontrolled cell growth, a hallmark of cancer. [1]
The theory originated from the work of Theodor Boveri, a German biologist, in the early 20th century. Boveri's studies on sea urchin eggs provided early evidence that abnormal chromosome numbers could lead to developmental defects, leading him to propose a connection between chromosomal abnormalities and cancer. [2]
Further research by scientists such as David Hungerford and Peter Nowell in the 1960s identified specific chromosomal abnormalities in cancer cells, such as the Philadelphia chromosome in chronic myeloid leukemia, providing more support for the chromosomal theory of cancer. [3]
Normal cells have a precise and stable number of chromosomes, which is crucial for proper cell function and division. Chromosomes contain genes that control cell growth, differentiation, and other cellular processes. [4]
Cancer cells often exhibit chromosomal abnormalities, including chromosomal rearrangements (such as translocations), deletions, and duplications. These abnormalities can disrupt the normal function of genes involved in cell cycle regulation, leading to uncontrolled cell growth and tumor formation. [4]
Chromosomal abnormalities can contribute to cancer development through several mechanisms,
Chromosomal rearrangements can lead to the fusion of genes, creating oncogenes that promote cell growth and division uncontrollably.
Chromosomal deletions or mutations can lead to the loss of tumor suppressor genes, which normally inhibit cell growth. Loss of these genes can further promote uncontrolled cell growth and tumor formation.
Chromosomal abnormalities can cause genomic instability, leading to additional mutations and genetic changes that contribute to cancer progression. [5] [6]
Experimental studies using cell lines, animal models, and human cancer samples have provided strong evidence supporting the chromosomal theory of cancer. These studies have demonstrated that chromosomal abnormalities can drive tumorigenesis and are often associated with specific types of cancer. [7]
Chromosomal analysis, such as karyotyping and fluorescence in situ hybridization (FISH), is commonly used in cancer diagnosis and prognosis to detect chromosomal abnormalities in cancer cells. [8] [9]
Targeted therapies, such as imatinib for chronic myeloid leukemia [10] and trastuzumab for HER2-positive breast cancer, [11] have been developed based on the specific chromosomal abnormalities associated with these cancers.
Current research in cancer genetics is focused on further understanding the role of chromosomal abnormalities in cancer development and progression. Advances in technology, such as next-generation sequencing, are enabling researchers to study chromosomal abnormalities in cancer cells with greater detail and precision. [12]
Future directions include the development of new targeted therapies and personalized medicine approaches based on the specific chromosomal abnormalities present in individual patients' tumors.
An oncogene is a gene that has the potential to cause cancer. In tumor cells, these genes are often mutated, or expressed at high levels.
Aneuploidy is the presence of an abnormal number of chromosomes in a cell, for example a human cell having 45 or 47 chromosomes instead of the usual 46. It does not include a difference of one or more complete sets of chromosomes. A cell with any number of complete chromosome sets is called a euploid cell.
The Philadelphia chromosome or Philadelphia translocation (Ph) is a specific genetic abnormality in chromosome 22 of leukemia cancer cells. This chromosome is defective and unusually short because of reciprocal translocation, t(9;22)(q34;q11), of genetic material between chromosome 9 and chromosome 22, and contains a fusion gene called BCR-ABL1. This gene is the ABL1 gene of chromosome 9 juxtaposed onto the breakpoint cluster region BCR gene of chromosome 22, coding for a hybrid protein: a tyrosine kinase signaling protein that is "always on", causing the cell to divide uncontrollably by interrupting the stability of the genome and impairing various signaling pathways governing the cell cycle.
Chronic myelogenous leukemia (CML), also known as chronic myeloid leukemia, is a cancer of the white blood cells. It is a form of leukemia characterized by the increased and unregulated growth of myeloid cells in the bone marrow and the accumulation of these cells in the blood. CML is a clonal bone marrow stem cell disorder in which a proliferation of mature granulocytes and their precursors is found; characteristic increase in basophils is clinically relevant. It is a type of myeloproliferative neoplasm associated with a characteristic chromosomal translocation called the Philadelphia chromosome.
Comparative genomic hybridization (CGH) is a molecular cytogenetic method for analysing copy number variations (CNVs) relative to ploidy level in the DNA of a test sample compared to a reference sample, without the need for culturing cells. The aim of this technique is to quickly and efficiently compare two genomic DNA samples arising from two sources, which are most often closely related, because it is suspected that they contain differences in terms of either gains or losses of either whole chromosomes or subchromosomal regions. This technique was originally developed for the evaluation of the differences between the chromosomal complements of solid tumor and normal tissue, and has an improved resolution of 5–10 megabases compared to the more traditional cytogenetic analysis techniques of giemsa banding and fluorescence in situ hybridization (FISH) which are limited by the resolution of the microscope utilized.
Fluorescence in situ hybridization (FISH) is a molecular cytogenetic technique that uses fluorescent probes that bind to only particular parts of a nucleic acid sequence with a high degree of sequence complementarity. It was developed by biomedical researchers in the early 1980s to detect and localize the presence or absence of specific DNA sequences on chromosomes. Fluorescence microscopy can be used to find out where the fluorescent probe is bound to the chromosomes. FISH is often used for finding specific features in DNA for use in genetic counseling, medicine, and species identification. FISH can also be used to detect and localize specific RNA targets in cells, circulating tumor cells, and tissue samples. In this context, it can help define the spatial-temporal patterns of gene expression within cells and tissues.
Myeloproliferative neoplasms (MPNs) are a group of rare blood cancers in which excess red blood cells, white blood cells or platelets are produced in the bone marrow. Myelo refers to the bone marrow, proliferative describes the rapid growth of blood cells and neoplasm describes that growth as abnormal and uncontrolled.
A fusion gene is a hybrid gene formed from two previously independent genes. It can occur as a result of translocation, interstitial deletion, or chromosomal inversion. Fusion genes have been found to be prevalent in all main types of human neoplasia. The identification of these fusion genes play a prominent role in being a diagnostic and prognostic marker.
Polysomy is a condition found in many species, including fungi, plants, insects, and mammals, in which an organism has at least one more chromosome than normal, i.e., there may be three or more copies of the chromosome rather than the expected two copies. Most eukaryotic species are diploid, meaning they have two sets of chromosomes, whereas prokaryotes are haploid, containing a single chromosome in each cell. Aneuploids possess chromosome numbers that are not exact multiples of the haploid number and polysomy is a type of aneuploidy. A karyotype is the set of chromosomes in an organism and the suffix -somy is used to name aneuploid karyotypes. This is not to be confused with the suffix -ploidy, referring to the number of complete sets of chromosomes.
Acute myeloid leukemia (AML) is a cancer of the myeloid line of blood cells, characterized by the rapid growth of abnormal cells that build up in the bone marrow and blood and interfere with normal blood cell production. Symptoms may include feeling tired, shortness of breath, easy bruising and bleeding, and increased risk of infection. Occasionally, spread may occur to the brain, skin, or gums. As an acute leukemia, AML progresses rapidly, and is typically fatal within weeks or months if left untreated.
Acute myeloblastic leukemia with maturation (M2) is a subtype of acute myeloid leukemia (AML).
Wilms tumor protein (WT33) is a protein that in humans is encoded by the WT1 gene on chromosome 11p.
Platelet-derived growth factor receptor beta is a protein that in humans is encoded by the PDGFRB gene. Mutations in PDGFRB are mainly associated with the clonal eosinophilia class of malignancies.
Factor interacting with PAPOLA and CPSF1 is a protein that in humans is encoded by the FIP1L1 gene. A medically important aspect of the FIP1L1 gene is its fusion with other genes to form fusion genes which cause clonal hypereosinophilia and leukemic diseases in humans.
Platelet-derived growth factor receptor A, also termed CD140a, is a receptor located on the surface of a wide range of cell types. The protein is encoded in the human by the PDGFRA gene. This receptor binds to certain isoforms of platelet-derived growth factors (PDGFs) and thereby becomes active in stimulating cell signaling pathways that elicit responses such as cellular growth and differentiation. The receptor is critical for the embryonic development of certain tissues and organs, and for their maintenance, particularly hematologic tissues, throughout life. Mutations in PDGFRA, are associated with an array of clinically significant neoplasms, notably ones of the clonal hypereosinophilia class of malignancies, as well as gastrointestinal stromal tumors (GISTs).
Somatic evolution is the accumulation of mutations and epimutations in somatic cells during a lifetime, and the effects of those mutations and epimutations on the fitness of those cells. This evolutionary process has first been shown by the studies of Bert Vogelstein in colon cancer. Somatic evolution is important in the process of aging as well as the development of some diseases, including cancer.
Chromogenic in situ hybridization (CISH) is a cytogenetic technique that combines the chromogenic signal detection method of immunohistochemistry (IHC) techniques with in situ hybridization. It was developed around the year 2000 as an alternative to fluorescence in situ hybridization (FISH) for detection of HER-2/neu oncogene amplification. CISH is similar to FISH in that they are both in situ hybridization techniques used to detect the presence or absence of specific regions of DNA. However, CISH is much more practical in diagnostic laboratories because it uses bright-field microscopes rather than the more expensive and complicated fluorescence microscopes used in FISH.
A cancer biomarker refers to a substance or process that is indicative of the presence of cancer in the body. A biomarker may be a molecule secreted by a tumor or a specific response of the body to the presence of cancer. Genetic, epigenetic, proteomic, glycomic, and imaging biomarkers can be used for cancer diagnosis, prognosis, and epidemiology. Ideally, such biomarkers can be assayed in non-invasively collected biofluids like blood or serum.
Antineoplastic resistance, often used interchangeably with chemotherapy resistance, is the resistance of neoplastic (cancerous) cells, or the ability of cancer cells to survive and grow despite anti-cancer therapies. In some cases, cancers can evolve resistance to multiple drugs, called multiple drug resistance.
Clonal hypereosinophilia, also termed primary hypereosinophilia or clonal eosinophilia, is a grouping of hematological disorders all of which are characterized by the development and growth of a pre-malignant or malignant population of eosinophils, a type of white blood cell that occupies the bone marrow, blood, and other tissues. This population consists of a clone of eosinophils, i.e. a group of genetically identical eosinophils derived from a sufficiently mutated ancestor cell.
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