NIST Standard Reference Material SRM® 2373 was developed to improve the measurements of the HER2 gene amplification in DNA samples. SRM® 2373 consists of genomic DNA extracted from five breast cancer cell lines with different amounts of amplification of the HER2 gene. The five components are derived from the human cell lines SK-BR-3, MDA-MB-231, MDA-MB-361, MDA-MB-453, and BT-474. The certified values are the ratios of the HER2 gene copy numbers to the copy numbers of selected reference genes (DCK, EIF5B, RPS27A, and PMM1). The ratios were measured using quantitative polymerase chain reaction and digital PCR, methods that gave similar ratios. The five components of SRM® 2373 have certified HER2 amplification ratios that range from 1.3 to 17.7. The stability and homogeneity of the reference materials were shown by repeated measurements over a period of several years. SRM® 2373 is a well-characterized genomic DNA reference material that can be used to improve the confidence of the measurements of HER2 gene copy number.
The amplification of the gene for HER2 occurs in approximately 20 to 25% of breast cancers. The accurate measurement of this biomarker is important for the proper treatment with anti-HER2 therapeutics. Clinical laboratories are beginning to utilize accurate and sensitive diagnostic tests based on measurements of DNA. We have prepared genomic DNA from 5 human breast cancer cell lines with different amounts of amplification of the HER2 gene. The copy numbers of the HER2 gene and 3 reference genes (not amplified) were measured using quantitative PCR and digital PCR assays. The certified values of the components are the ratios of the HER2 gene copy number to the reference gene copy numbers. The PCR assays were validated and calibrated using NIST SRM® 2372 component A (human genomic DNA). The stability of the components was shown by repeated measurements over several years. The DNA concentration determined from absorbance and the PCR assays was provided as informational value.
SRM® 2373 is currently available and can be obtained from the NIST SRM site http://www.nist.gov/srm/.