High incidence of microsatellite instability and loss of heterozygosity in three loci in breast cancer patients receiving chemotherapy: a prospective studyReport as inadecuate

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BMC Cancer

, 12:373

First Online: 28 August 2012Received: 24 January 2012Accepted: 21 August 2012DOI: 10.1186-1471-2407-12-373

Cite this article as: Kamat, N., Khidhir, M.A., Jaloudi, M. et al. BMC Cancer 2012 12: 373. doi:10.1186-1471-2407-12-373


BackgroundThe aim of the study was to evaluate potential chemotherapy-induced microsatellite instability, loss of heterozygosity, loss of expression in mismatch repair proteins and associations with clinical findings in breast cancer patients, especially resistance to chemotherapy and-or development of other tumors in the four years following chemotherapy treatment.

MethodsA comprehensive study of chemotherapy-related effects with a follow-up period of 48 months post treatment was conducted. A total of 369 peripheral blood samples were collected from 123 de novo breast cancer patients. Microsatellite instability and loss of heterozygosity in five commonly used marker loci including Tp53-Alu of the tumor suppressor gene TP53 were analyzed in blood samples. Sampling was conducted on three occasions; 4–5 weeks prior to the first chemotherapy session pre-treatment, to serve as a baseline, followed by two consecutive draws at 12 weeks intervals from the first collection. Mismatch repair protein expression was evaluated in cancer tissues using immunohistochemistry for three mismatch-repair related proteins.

ResultsA total of 70.7% of the patients showed microsatellite instability for at least one locus, including 18.6% marked as high-positive and 52.1% as low-positive; 35.8% showed loss of heterozygosity in addition to microsatellite instability, while 29.3% exhibited microsatellite stability. The following incidence rates for microsatellite instability and loss of heterozygosity were detected: 39.1% positive for Tp53-Alu, 31.1% for locus Mfd41, and 25.3% for locus Mfd28. A higher occurrence of loss of heterozygosity was noted with alleles 399 and 404 of Tp53-Alu. The mismatch repair protein expression analysis showed that the chemotherapy caused a loss of 29.3% in hMLH1 expression, and 18.7% and 25.2% loss in hMSH2 and P53 expression, respectively. A strong correlation between low or deficient hMSH2 protein expression and occurrence of mismatch repair-loss of heterozygosity events in Mfd41, Tp53-Alu, and Mfd28 was evident. A significant association between mismatch repair-loss of heterozygosity and incidence of secondary tumors was also established.

ConclusionOur results suggest that microsatellite instability, loss of heterozygosity, and deficiency in mismatch repair may serve as early prognostic factors for potential chemotherapy-related side effects in breast cancer patients.

KeywordsChemotherapy Breast cancer Genetic instability Microsatellites Mismatch repair Loss of heterozygosity AbbreviationsFECFlourouracil-Epirubicin-Cyclophosphamide Regimen

HNPCCHereditary Nonpolyposis Colorectal Carcinoma

hMLH1Human mutL homolog 1

hMSH2Human mutS homolog 2

LOHLoss of heterozygosity

MMRMismatch repair

MSIMicrosatellite instability

MSSMicrosatellite stable.

Electronic supplementary materialThe online version of this article doi:10.1186-1471-2407-12-373 contains supplementary material, which is available to authorized users.

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Author: Nasir Kamat - Mohammed A Khidhir - Mohammed Jaloudi - Sabir Hussain - Mouied M Alashari - Khaled H Al Qawasmeh - Ulf Ran

Source: https://link.springer.com/

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