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Such silencing is proposed to act similarly to a germ-line mutation in a DNA repair gene, and predisposes the cell and its descendants to progression to cancer. Another review [18] also indicated an early role for hypermethylation of DNA repair genes in cancer. If a gene necessary for DNA repair is hypermethylated, resulting in deficient DNA ...
DNA mismatch repair protein Msh2 also known as MutS homolog 2 or MSH2 is a protein that in humans is encoded by the MSH2 gene, which is located on chromosome 2.MSH2 is a tumor suppressor gene and more specifically a caretaker gene that codes for a DNA mismatch repair (MMR) protein, MSH2, which forms a heterodimer with MSH6 to make the human MutSα mismatch repair complex.
The central role of DNA damage and epigenetic defects in DNA repair genes in carcinogenesis. DNA damage is considered to be the primary cause of cancer. [17] More than 60,000 new naturally-occurring instances of DNA damage arise, on average, per human cell, per day, due to endogenous cellular processes (see article DNA damage (naturally occurring)).
Individuals with inherited mutations in any of 34 DNA repair genes are at increased risk of cancer (see DNA repair defects and increased cancer risk). In sporadic cancers, a deficiency in DNA repair is occasionally found to be due to a mutation in a DNA repair gene, but much more frequently reduced or absent expression of DNA repair genes is ...
Deficient expression of DNA repair proteins due to an inherited mutation can cause increased risk of cancer. Individuals with an inherited impairment in any of 34 DNA repair genes (see article DNA repair-deficiency disorder) have an increased risk of cancer, with some defects causing up to a 100% lifetime chance of cancer (e.g. p53 mutations ...
MGMT (O-6-methylguanine-DNA methyltransferase) is an important cancer biomarker because it is involved in the repair of DNA damage and is often silenced or inactivated in cancer cells. The loss of MGMT function leads to a higher rate of mutations, promoting the formation and progression of tumors.
Ordinarily, deficient expression of a DNA repair enzyme results in increased un-repaired DNA damages which, through replication errors (translesion synthesis), lead to mutations and cancer. However, XRCC1 mediated MMEJ repair is directly mutagenic, so in this case, over-expression, rather than under-expression, apparently leads to cancer.
For example, epigenetic silencing of genes responsible for the repair of mispairs or damages in the DNA (e.g. MLH1 or MSH2) results in an increase of genetic mutations. Deficiency of DNA repair proteins PMS2, MLH1, MSH2, MSH3, MSH6 or BRCA2 can cause up to 100-fold increases in mutation frequency [51] [52] [53] Epigenetic deficiencies in DNA ...