Robert Zahorchak

Standardized RT-PCR and the Standardized Expression Measurement Center

Standardized reverse transcriptase polymerase chain reaction (StaRT-PCR) is a modification of the competitive template (CT) RT method described by Gilliland et al. StaRT-PCR allows rapid, reproducible, standardized, quantitative measurement of data for many genes simultaneously. An internal standard CT is prepared for each gene, cloned to generate enough for 10(9) assays and CTs for up to 1,000 genes are mixed together. Each target gene is normalized to a reference gene to control for cDNA loaded in a standardized mixture of internal standards (SMIS) into the reaction. Each target gene and reference gene is measured relative to its respective internal standard within the SMIS. Because each target gene and reference gene is simultaneously measured relative to a known number of internal standard molecules in the SMIS, it is possible to report each gene expression measurement as a numerical value in units of target gene cDNA molecules/ 10(6) reference gene cDNA molecules. Calculation of data in this format allows for entry into a common databank, direct interexperimental comparison, and combination of values into interactive gene expression indices.

Reproducible gene expression measurement among multiple laboratories obtained in a blinded study using standardized RT (StaRT)-PCR

AbstractBackground: A method that provides standardized data and is relatively inexpensive and capable of high throughput is a prerequisite to the development of a meaningful gene expression database suitable for conducting multi-institutional clinical studies based on expression measurement. Standardized RT (StaRT)-PCR has all these characteristics. In addition, the method must be reproducible. StaRT-PCR has high intralaboratory reproducibility. The purpose of this study is to determine whether StaRT-PCR provides similar interlaboratory reproducibility. Methods and Results: In a blinded interlaboratory study, expression of ten genes was measured by StaRT-PCR in a complementary DNA sample provided to each of four laboratories. The average coefficient of variation for interlaboratory comparison of the nine quantifiable genes was 0.48. In all laboratories, expression of one of the genes was too low to be measured. Conclusion: Because StaRT-PCR data are standardized and numerical and the method is reproducible among multiple laboratories, it will allow development of a meaningful gene expression database.

Multiplex standardized RT-PCR for expression analysis of many genes in small samples.

Standardized RT-PCR (StaRT-PCR) enables numerical quantification as well as intra- and inter-laboratory comparison of gene expression. Multiplex StaRT-PCR, using two rounds of amplification, was conducted on Stratagene Universal Reference RNA. In the first round, cDNA, competitive template (CT) mix, and primers for up to 96 genes were amplified for varying numbers of cycles. Next, products from round one were diluted, combined with primers for one gene, and amplified for an additional 35 cycles. No additional cDNA or CT mix was added. Expression values obtained by uniplex and multiplex StaRT-PCRs were highly correlated (R=0.993, p<0.001). Products from round one could be diluted as much as 100,000-fold and still be quantified following round two amplification. Thus, using multiplex StaRT-PCR, 96 genes were measured in the same amount of cDNA typically used to measure one gene with uniplex StaRT-PCR. Multiplex StaRT-PCR was also used to measure 18 genes in the fine needle biopsy of a primary lung carcinoma.

The c-myc x E2F-1/p21 interactive gene expression index augments cytomorphologic diagnosis of lung cancer in fine-needle aspirate specimens

Morphological analysis of cytologic samples obtained by fine-needle aspirate (FNA) or bronchoscopy is an important method for diagnosing bronchogenic carcinoma. However, this approach has only about 65 to 80% diagnostic sensitivity. Based on previous studies, the c-myc x E2F-1/p21WAF1/CIP1 (p21 hereafter) gene expression index is highly sensitive and specific for distinguishing normal from malignant bronchial epithelial tissues. In an effort to improve sensitivity of diagnosing lung cancer in cytologic specimens, we used Standardized Reverse Transcriptase Polymerase Chain Reaction (StaRT-PCR) to measure the c-myc x E2F-1/p21 index in cDNA samples from 14 normal lung samples (6 normal lung parenchyma and 8 normal bronchial epithelial cell [NBEC] biopsies), and 16 FNA biopsies from 14 suspected tumors. Based on cytomorphologic criteria, 11 of the 14 suspected tumors were diagnosed as bronchogenic carcinoma and three specimens were non-diagnostic. Subsequent biopsy samples confirmed that the three non-diagnostic samples were derived from lung carcinomas. The index value for each bronchogenic carcinoma was above a cut-off value of 7000 and the index value of all but one normal sample was below 7000. Thus the c-myc x E2F-1/p21 index may augment cytomorphologic diagnosis of bronchogenic carcinoma biopsy samples, particularly those considered non-diagnostic by cytomorphologic criteria.