MLH1/ MSH2 Microsatellite Instability - Colorectal Cancer Test Cost & Procedure

The Lynch syndrome genes are tested using MSI screening to determine their functional status. When mismatch repair isn't functioning properly, microsatellites, which are repeats of DNA, vary in length (display instability).

Why is this test advised?

• Short tandem repeats are susceptible to alterations associated with DNA sequences in some colorectal tumours (CRCs), a condition known as microsatellite instability (MSI).
• A germline/somatic mutation in the mismatch-repair (MMR) genes is the cause, which results in a DNA-mismatch-repair system deficiency.
• While epigenetic gene silencing causes sporadic CRC cancers, germline mutations cause Lynch syndrome (LS).
• The most significant clinical facets of MSI testing in CRCs are covered in our paper.

What Clinical Applications for Colorectal Cancer Do Microsatellite Instability Tests Have?

Historically, at least three clinical uses—prognostic, diagnostic, or predictive—could be thought of for MSI testing in CRC.

What is the Procedure for Microsatellite Instability Testing?

• MSI testing is done by amplifying microsatellite repeats using the polymerase chain reaction (PCR) and comparing the size of the repeats to the DNA of normal and malignant cells.
• It is now made using capillary electrophoresis and fluorescent primers.
• Two mononucleotide markers, BAT-25 and BAT-26, and three dinucleotide markers, D2S123, D5S346, and D17S250, make up the National Cancer Institute's suggested diagnostic panel for MSI testing. When at least two of the five markers in tumour cells exhibit variability, the MSI-H panel defines it as
• Meanwhile, the molecular phenotype is categorized as MSI-low if only one marker indicates instability in tumour cells (MSI-L). Intumourr cells with a microsatellite stable (MSS) status, there is no unstable marker present.
• Following this, various research revealed that mononucleotide markers in MSI testing had higher specificity and equal to higher sensitivity than dinucleotide markers, which led to the development of some commercial kits.
• Due to the quasi-monomorphic nature of these mononucleotide repeats, practically everyone is homozygous for each common allele of a given marker.