The use of genetic information plays a crucial role in precision medicine.
It not only detects cancer, but can also figure out or susceptibility,
if it will show a good prognosis, or verify the causes of relapse.
Identifying the genomic information of cancer contributes to higher treatment success rate.
We are more focused on -
Liquid Biopsy-based Cancer Genome Analysis
DNA which comes into blood vessels directly from various cells that compose cancer is called circulating tumor DNA (ctDNA), and analyzing
this enables directly monitoring tumor dynamics.
Because ctDNA takes up a small portion of normal DNA, however, it is difficult to monitor the changes in the cancer genome which
transforms in blood.
Cancer to Chronic Disease
Sampling with blood is less demanding to patients and so can be conducted regularly, and setting a direction for
treatment through regularly analyzing blood genome allows cancer to turn into a chronic disease.
Immune Checkpoint Inhibitor
Cancer cell confuses the immune checkpoint protein on the surface of immune cell (T cell) to avoid the attack by the immune cell. When
the immune checkpoint inhibitor interferes with the coupling of such cancer cell and immune checkpoint protein, the immune cell attacks
and removes the cancer cell. The clinical research has been actively carried out to find the biomarker to select the patient suitable for the
use of immune checkpoint inhibitor. Recently, such research result has been presented that the condition of microsatellite is highly related
to the effect of immune checkpoint inhibitor.
Microsatellite is a part where the short sequencing repeats several
times among entire human genes. Microsatellite is a vulnerable
part for gene replication error, which has been used for the
biomarker of test on the abnormality of gene repair system.
If mismatch repair gene does not function properly, the number of repeats of microsatellite cannot be maintained constantly
but abnormally increased or decreased. Such condition is called
'Microsatellite Instability (MSI).
Microsatellite Instability - Response to Immunotherapy
Microsatellite instability, MSI
Microsatellite instability is a type generated by the problem of the
system that repairs the problem (mismatch) occurred during the
replication of DNA. If mismatch repair system does not function
properly, the number of repeats of microsatellite cannot be
maintained constantly, but abnormally increased or decreased.
Such condition is called 'Microsatellite Instability (MSI).
The condition of microsatellite has been traditionally used for the
classification of colon cancer. Since the result was presented for
the high treatment efficiency by immune checkpoint inhibitor on
the metastatic colon cancer which is the microsatellite instability,
recently the microsatellite instability has been used in various
cancers for the useful marker of the prescription of specific
immune checkpoint inhibitor (Pembrolizumab, etc).
Comparison of colon cancer patients' survival rates
A clinical research shows that patients with MSI colon cancer
register a good prognosis for treatment with immune checkpoint
inhibitor (Pembrolizumab, PD-1 blockade) than those with MSS
(microsatellite stability) colon cancer. (Le et al., 2015. N Engl J
Diagnosing Microsatellite instability
Microsatellite instability (MSI) has been used for the marker to show the condition of cancer. In general, it is classified to MSI-H, MSI-L and
MSS. More than 2 genes of MSI-H are in unstable condition among 5 genes of microsatellite. One gene of MSI-L is in unstable condition among 5 genes of microsatellite.
It is called MSS when all 5 genes of microsatellite are in stable condition. Generally, the method to diagnose the instability of microsatellite genes uses the fragment analysis after PCR
The instability diagnosis on microsatellite based on the real time polymerase chain reaction is analyzed for the result analysis through one
step. The analysis is carried out by converting the difference of gene length between normal tissue and cancer tissue to the difference of temperature.