Allelic alterations of STRs in archival paraffin embedded tissue as DNA source for paternity testing

Owing to a wrong name registered on ID card, the identity of a businessman who had been dead and cremated was suspected, which led his son failed to get legacy. In order to prove the parenthood, the son submitted the gastric cancer tissues surgically removed and embedded in a paraffin block as DNA source for paternity test. After extracting DNA with QIAamp DNA Blood Mini Kit, the 16 STR loci was amplified by two commercial kits of Sinofiler® (ABI)and Powerplex 16 (Promega), respectively. Both of the STR profiles were similarly showing allelic imbalance pattern at some loci and an additional allele at locus D18S51. The cancerous tissues and adjacent normal tissues were then partitioned off from each other by microscopic analysis of H.E. stained sections and followed by DNA extracting and STR typing, respectively. The allelic alteration could not be found in normal tissues whereas it did in cancerous tissues whose STR profile showed complete loss of one allele (LOH) at loci D13S317 (allele 11 was lost), partial loss of one allele (pLOH) at loci D21S11, D7S820, D19S433, vWA, D12S391 and Amelogein and occurrence of an additional allele (allele 20 was added) at locus D18S51. The results demonstrated that the Paraffin Embedded cancer Tissue used as DNA source for forensic identification is possibly questionable because of their microsatellite instability (MSI) or loss of heterozygosity. It was suggested to partition the normal tissues from the cancer tissues by microscopic evaluation first and then analyzing DNA separately. Comparing the STRs profile of normal tissue with the son's blood sample, the final conclusion was acquired that the donor of the paraffin embedded tissues is the biological father of the son.