SPECIAL FEATURE :: PCR
Microsatellite instability (MSI) is a key factor in several cancers including colorectal, endometrial, ovarian, and gastric cancers. Colorectal cancer studies have demonstrated two mechanisms for MSI occurrence. The first is in heredi- tary nonpolyposis colorectal cancer (HNPCC) or Lynch syndrome, where an inherited mutation in a mismatch- repair gene causes a microsatellite repeat replication error to go unfixed. The replication error results in a frameshift mutation that inactivates or alters major tumor suppressor genes. These genes are essential in the regulation of the cell cycle and, ultimately, the prevention of cancer. The second mechanism whereby MSI causes colorec- tal cancer is an epigenetic change which silences an essential mismatch-repair gene. In both cases, microsat- ellite insertions and deletions within tumor suppressor gene coding regions result in uncontrolled cell division and tumor growth. Five markers have been recom- mended by the National Cancer Institute to screen for MSI in HNPCC tumors (often called Bethesda markers). Generally, MSI detection in two of the markers is considered a positive result or high probability of MSI (MSI-H). Figure 6 is an example of a sample with MSI-H. The tumor sample fragments are compared to the fragments from non-tumor tissue of the same source by overlaying the electropherograms. The normal tissue is the red trace; the other traces are the tumor sample. Each of the polymorphic loci have additional microsatellite fragments in the tumor sample. The summary table highlights any of the markers with an increase in the number of microsatellite fragments.
Monitoring chimerism
Monitoring post bone marrow transplant chimerism, the extent to which the donor cells have engrafted in the recipi- ent, is essential to confirm stability or detect any signs of graft failure. The analysis uses the same QF-PCR human identity chemistries which amplify short tandem repeats (STRs) used for forensic human identity testing. Highly polymorphic STRs are amplified using a multiplex of STR primers and separated by capillary electrophoresis. Peak heights or areas of fragments from donor and recipient are used to calculate chimerism, the percent of the DNA from the donor. Figure 7 is an electropherogram from a control 3:1 mixture. Peaks attributed to donor, recipient, or shared are indicated by the flag labels (D, R, D/R). Figure 8 contains the corresponding result table of the percent donor at each locus, total percent donor chimerism, and quality metrics.
Editor’s note: Figures 1-8 and references can be found online at
www.mlo-online.com.
Teresa Snyder-Leiby, PhD has served as product manager for DNA fragment analysis software at SoftGenetics for 11 years. Teresa was a biology professor at the State University of New York (SUNY New Paltz) prior to joining the support and development team at SoftGenetics.
* * 6 * for on
* 6%CV at the 99th percentile for Troponin I. Source: IFCC Table of analytical characteristics of commercial cardiac Troponin I and T assay declared by the manufacturer – June 2017 (
www.ifcc.org)
Emergency Department, Food and Drug Administration, American Heart Association, Coefficient of Variation 800-431-2123
info@polymedco.com . 2018 Polymedco, Inc. LSI
cardiac events *
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48
