Predicting cancer prognosis

Stanford, CA — Researchers led by Dr. Soheil Dadras at the Stanford University Medical Center have developed a novel methodology to extract microRNAs from cancer tissues. The related report by Ma et al, "Profiling and discovery of novel miRNAs from formalin-fixed paraffin-embedded melanoma and nodal specimens," appears in the September 2009 issue of the Journal of Molecular Diagnostics.

Cancer tissues from patients are often stored by a method that involves formalin fixation and paraffin embedding to retain morphological definition for identification; however, this method frequently prevents further molecular analysis of the tissue because of mRNA degradation. Even so, these tissues contain high numbers of microRNAs (miRNAs), which are short enough (~22 nucleotides) to not be broken down during the fixation process.

In this study, Dr. Dadras and colleagues optimized a new protocol for extracting miRNAs from formalin-fixed paraffin-embedded tissues. Using their new procedure, they identified 17 new and 53 known miRNAs from normal skin, melanoma, and sentinel lymph nodes. These miRNAs were well-preserved in a 10-year-old specimen. This new protocol, therefore, will allow for the identification of novel miRNAs that may differ in cancerous and healthy tissue, even from long-preserved tissue, leading to better predictions of disease prognosis and treatment response.

Ma et al suggest that their "cloning strategy has the advantage of not only discovering novel and known miRNA sequence identity but also providing an estimate of relative expression level. … [This methodology may provide] a more robust strategy to obtain an accurate expression profile for novel and/or previously characterized small RNAs from clinically defined [formalin-fixed paraffin-embedded] tumor specimens, thereby facilitating the discovery of 'oncomirs' as biomarkers."

Ma Z, Lui W-O, Fire A, Dadras SS: Profiling and discovery of novel miRNAs from formalin-fixed paraffin-embedded melanoma and nodal specimens. J Mol Diagn 2009, 420-429

This work was supported in part by 2007 Dermatology Foundation Dermatopathology Research Grant and the department of Pathology research funds at Stanford University Medical Center.

For press copies of the articles, please contact Dr. Angela Colmone at 301-634-7953 or acolmone@asip.org.

The Journal of Molecular Diagnostics, the official publication of the Association for Molecular Pathology, co-published by the American Society for Investigative Pathology, seeks to publish high quality original papers on scientific advances in the translation and validation of molecular discoveries in medicine into the clinical diagnostic setting, and the description and application of technological advances in the field of molecular diagnostic medicine. The editors welcome for review articles that contain: novel discoveries or clinicopathologic correlations including studies in oncology, infectious diseases, inherited diseases, predisposition to disease, or the description or polymorphisms linked to disease states or normal variations; the application of diagnostic methodologies in clinical trials; or the development of new or improved molecular methods for diagnosis or monitoring of disease or disease predisposition.