Optimization of a pentaplex panel for MSI analysis without control DNA in a Brazilian population: correlation with ancestry markers

Author(s)

Campanella, Nathalia C. ^[1] ; Berardinelli, Gustavo N. ^[1] ; Scapulatempo-Neto, Cristovam ^[1] ; Viana, Danilo ^[2] ; Palmero, Edenir I. ^[1] ; Pereira, Rui ^[3] ; Reis, Rui M. ^{[4, 1, 5]}

Affiliation

^[1] Barretos Canc Hosp, Mol Oncol Res Ctr, BR-14784400 Sao Paulo - Brazil

^[2] Barretos Canc Hosp, Oncogenet Dept, BR-14784400 Sao Paulo - Brazil

^[3] Univ Porto, IPATIMUP Inst Mol Pathol & Immunol, P-4100 Oporto - Portugal

^[4] ICVS 3Bs PT Govt Associate Lab, Braga - Portugal

^[5] Univ Minho, Life & Hlth Sci Res Inst, Braga - Portugal

• Document type: Journal article
• Source: European Journal of Human Genetics; v. 22, n. 7, p. 875-880, JUL 2014.
• Web of Science Citations: 14

Abstract

Microsatellite instability (MSI) testing has been advocated for all newly diagnosed colorectal cancer patients. One of the most common tests is composed by a pentaplex panel of mononucleotides markers (NR-27, NR-21, NR-24, BAT-25, and BAT-26), which allows the analysis of MSI in tumors without the need of reference DNA. For that, it is fundamental to establish a quasi-monomorphic variation range (QMVR) for each marker. Herein, we aimed to establish the QMVR in a Brazilian healthy population, to evaluate the feasibility of MSI determination of tumors, without the matching normal DNA. Furthermore, we intend to assess their ancestry using specific ancestry-informative markers (AIMs) and correlate with QMVR. The QMVR was assessed in 214 individuals, through a pentaplex PCR followed by fragment analysis. The ancestry analysis was done by 46 AIMs in a single multiplex PCR followed by capillary electrophoresis. Following QMVR establishment, we observed 23 individuals with alleles outside the QMVR. Importantly, none of them exhibited more than one marker outside the range. Therefore, individuals with instability at >= 2 markers would be accurately classified as MSI. The European ancestry proportion was the most frequent (67.5%), followed by the African (19.6%). The comparison of the individuals with alleles within (n = 191) and outside (n 23) the QMVR showed statistical difference in the proportions of European and African alleles, confirming the higher polymorphic nature of African ancestry. In conclusion, the present study reports an accurate methodology to assess MSI status without matched-normal DNA and independently of the ethnicity, even in the highly admixed population of Brazil. (AU)

• FAPESP's process: 12/01732-2 - Study of microsatellite instability and potential target genes in GISTs
• Grantee: Nathália Cristina Campanella
• Support Opportunities: Scholarships in Brazil - Master