Negative‐Pressure Fixation Improves RNA Preservation and Increases the Success Rate of the Oncomine Dx Target Test in Lung Cancer Formalin‐Fixed Paraffin‐Embedded Samples

ABSTRACT

Genetic tests for lung cancer, such as the Oncomine Dx Target Test (ODxTT), are essential for patient management, and require RNA and DNA of sufficient quality and quantity from formalin‐fixed paraffin‐embedded (FFPE) samples. ODxTT fails due to poor nucleic acid preservation. Although enhancing the penetration of formalin into tissues improves nucleic acid preservation, the clinical utility of negative‐pressure fixation methods remains unclear. Therefore, we investigated whether the negative‐pressure fixation method using a vacuum fixation device improves ODxTT success rates and the quality of nucleic acids in FFPE samples from lung and other cancers, and examined the underlying mechanisms. The ODxTT success rate was higher with the negative‐pressure fixation method than with the conventional method (96.5% vs. 81.2%), accompanied by increased RNA quality and yield; however, no marked differences were observed in DNA. RNA deteriorated more rapidly than DNA in resected mouse liver tissues, indicating that RNA is more labile than DNA during cold ischemia. Furthermore, in FFPE samples from colon, pancreatic, and prostate cancers, negative‐pressure fixation consistently improved RNA DV200. These results indicate that the negative‐pressure fixation method improves ODxTT success by accelerating formalin penetration, which may suppress RNase‐mediated RNA degradation and preserve RNA quality.