A validated quantitative assay to detect occult micrometastases by reverse transcriptase-polymerase chain reaction of guanylyl cyclase C in patients with colorectal cancer.

Authors

• Stephanie Schulz
• Terry Hyslop
• Janis Haaf
• Christine Bonaccorso
• Karl Nielsen
• Matthew E Witek
• Ruth Birbe
• Juan Palazzo
• David Weinberg
• Scott A Waldman

Publication/Presentation Date

8-1-2006

Abstract

PURPOSE: Guanylyl cyclase C (GCC), a receptor for bacterial diarrheagenic enterotoxins, may be a prognostic and predictive marker to detect occult micrometastases in patients undergoing staging for colorectal cancer. However, quantification of GCC expression in tissues by the quantitative reverse transcription-PCR (qRT-PCR) has not undergone analytic and clinicopathologic validation.

EXPERIMENTAL DESIGN: A technique to quantify GCC mRNA in tissues employing RT-PCR was developed and validated employing external calibration standards of RNA complementary to GCC.

RESULTS: GCC qRT-PCR exhibited reaction efficiencies >92%, coefficients of variations < 5%, linearity >6 orders of magnitude, and a limit of quantification of >25 copies of GCC cRNA. This assay confirmed that GCC mRNA was overexpressed by colorectal tumors from 41 patients, which correlated with increased GCC protein quantified by immunohistochemistry. Analyses obtained with 164 lymph nodes from patients free of cancer and 15 nodes harboring metastases established a threshold for metastatic disease of approximately 200 GCC mRNA copies/mug total RNA, with a sensitivity of 93% and specificity of 97%. GCC mRNA above that threshold was detected in 76 of 367 (approximately 21%) nodes free of disease by histopathology from 6 of 23 (26%) patients, suggesting the presence of occult micrometastases.

CONCLUSIONS: Quantifying GCC mRNA in tissues by RT-PCR employing external calibration standards is analytically robust and reproducible, with high clinicopathologic sensitivity and specificity. This validated assay is being applied to approximately 10,000 lymph nodes in a prospective trial to define the sensitivity of GCC qRT-PCR for staging patients with colorectal cancer.

Volume

12

Issue

15

First Page

4545

Last Page

4552

ISSN

1078-0432

Published In/Presented At

Schulz, S., Hyslop, T., Haaf, J., Bonaccorso, C., Nielsen, K., Witek, M. E., Birbe, R., Palazzo, J., Weinberg, D., & Waldman, S. A. (2006). A validated quantitative assay to detect occult micrometastases by reverse transcriptase-polymerase chain reaction of guanylyl cyclase C in patients with colorectal cancer. Clinical cancer research : an official journal of the American Association for Cancer Research, 12(15), 4545–4552. https://doi.org/10.1158/1078-0432.CCR-06-0865

Disciplines

Business Administration, Management, and Operations | Health and Medical Administration | Management Sciences and Quantitative Methods

PubMedID

16899600

Department(s)

Administration and Leadership

Document Type

Article