Method enabling use of extracellular RNA extracted from...

Details Method enabling use of extracellular RNA extracted from... Method enabling use of extracellular RNA extracted from...

1998-09-22

2001-12-11

Whisenant, Ethan (Department: 1655)

Chemistry: molecular biology and microbiology

Micro-organism, tissue cell culture or enzyme using process...

Preparing compound containing saccharide radical

C435S006120, C435S091100, C435S091510, C436S094000, C536S023100, C536S024300, C536S024330

Reexamination Certificate

active

06329179

ABSTRACT:

BACKGROUND OF THE INVENTION
Ribonucleic acid (RNA) is essential to the processes which allow translation of the genetic code to form proteins necessary for all cellular functions, both in normal and neoplastic cells. While the genetic code structurally exists as deoxyribonucleic acid (DNA), it is the function of RNA, existing as the subtypes transfer-RNA, messenger-RNA or messenger-like RNA, and ribosomal-RNA, to carry and translate this code to the cellular sites of protein production. In the nucleus, this RNA may further exist as or in association with ribonucleoproteins (RNP). The pathogenesis and regulation of cancer is dependent upon RNA-mediated translation of specific genetic codes, which often reflects mutational events within oncogenes, to produce proteins involved with cell proliferation, regulation, and death. Furthermore, other RNA and their translated proteins, although not necessarily those involved in neoplastic pathogenesis or regulation, may serve to delineate recognizable characteristics of particular neoplasms by either being elevated or inappropriately expressed. Thus, recognition of specific RNA can enable the identification, detection, inference, monitoring, or evaluation of any neoplasm, benign, malignant, or premalignant, in humans and animals. Furthermore, since RNA can be repetitively created from its DNA template, for a given gene within a cell there may be formed a substantially greater number of associated RNA molecules than DNA molecules. Thus, an RNA-based assay should have greater sensitivity, and greater clinical utility, than its respective DNA-based assay. Note that the term RNA denotes ribonucleic acid including fragments of ribonucleic acid consisting of ribonucleic acid sequences.
RNA based nucleic acid amplification assays, including the reverse transcriptase polymerase chain reaction (RT-PCR, also known as reverse transcription polymerase chain reaction or RNA-PCR), branched DNA signal amplification, and self-sustained sequence replication assays, such as isothermal nucleic acid sequence based amplification (NASBA), have proven to be highly sensitive and specific methods for detecting small numbers of RNA molecules. As such, they can be used in direct assays of neoplastic tissue (1-3). Since peripheral blood is readily obtainable from patients with cancer, and metastatic cancer cells are known to circulate in the blood of patients with advanced cancer, several investigators have recently used RT-PCR to detect intracellular RNA extracted from circulating cancer cells (4-7). It must be emphasized that currently investigators apply RT-PCR to detect extracted intracellular RNA from a predominately cellular fraction of blood in order to demonstrate the existence of circulating cancer cells. RT-PCR is applied only to the cellular fraction of blood obtained from cancer patients, i.e., the cell pellet or cells within whole blood. The plasma or serum fraction of blood is usually discarded prior to analysis, but is not examined separately. Since such a cellular fraction approach relies upon the presence of metastatic circulating cancer cells, it is of limited clinical use in patients with early cancers, and is not useful in the detection of non-invasive neoplasms or pre-malignant states.
The invention described by this patent application demonstrates the novel use of that human or animal tumor-derived or tumor-associated RNA found circulating in the plasma or serum fraction of blood, as a means to detect, monitor, or evaluate cancer and premalignant states. This invention is based upon the application of RNA extraction techniques and nucleic acid amplification assays to detect tumor-derived or associated extracellular RNA found circulating in plasma or serum. In contrast to the detection of viral-related RNA in plasma or serum, and the detection of tumor-associated DNA in plasma and serum, the detection of human or mammalian RNA, and particularly tumor-derived or associated RNA, has never been detected specifically within the plasma or serum fraction of blood using nucleic acid amplification methodology, and thus represents a novel and non-obvious use for these RNA extraction methods and nucleic acid amplification assays. Since this invention is not dependent upon the presence of circulating cancer cells, it is clinically applicable to cases of early cancer, non-invasive cancers, and premalignant states, in addition to cases of invasive cancer and advanced cancer. Further, this invention allows the detection of RNA in previously frozen or otherwise stored plasma and serum, thus making plasma and serum banks available for analysis and otherwise increasing general usefulness.
Tumor-derived or tumor-associated RNA that is present in plasma and serum may exist in two forms. The first being extracellular RNA, but the second being extractable intracellular RNA from cells occasionally contaminating the plasma or serum fraction. In practice, it is not necessary to differentiate between intracellular and extracellular in order to detect RNA in plasma or serum using the invention, and this invention can be used for detection of both. The potential uses of tumor-derived or associated extracellular RNA have not been obvious to the scientific community, nor has the application of nucleic acid amplification assays to detect tumor-derived or associated extracellular RNA been obvious. Indeed, the very existence of tumor-derived or associated extracellular RNA has not been obvious to the scientific community, and is generally considered not to exist. It is generally believed that plasma ribonucleases rapidly degrade any extracellular mammalian RNA which might circulate in blood, rendering it nondetectable (8). Komeda et al., for example, specifically added free RNA to whole blood obtained from normal volunteers, but were unable to detect that RNA using PCR (54). However, nucleases appear inhibited in the plasma of cancer patients (9). In addition, extracellular RNA, either complexed to lipids and proteolipids, protein-bound, or within apoptotic bodies, would be protected from ribonucleases. Thus, although still undefined, tumor-derived or associated extracellular RNA may be present in plasma or serum via several mechanisms. Extracellular RNA could be secreted or shed from tumor in the form of lipoprotein (proteo-lipid)-RNA or lipid-RNA complexes, it could be found within circulating apoptotic bodies derived from apoptotic tumor cells, it could be found in proteo-RNA complexes released from viable or dying cells including or in association with ribonucleoproteins, or in association with other proteins such as galectin-3, or RNA could be released from necrotic cells and then circulate bound to proteins normally present in plasma. Additionally it could exist circulating within RNA-DNA complexes including those associated with ribonucleoproteins and other nucleic RNA. Further, RNA may exist within several of these moieties simultaneously. For example, RNA may be found associated with ribonucleoprotein found within proteo-lipid apoptotic bodies. The presence of extracellular RNA in plasma or serum makes their detection by nucleic acid amplification assays feasible.
Several studies in the literature support the existence of tumor-derived or associated extracellular RNA. RNA has been shown to be present on the cell surface of tumor cells, as demonstrated by electrophoresis (10), membrane preparations (11), and P
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release (12). Shedding of phospholipid vesicles from tumor cells is a well described phenomena (13,14), and similar vesicles have been shown to circulate in the blood of patients with cancer (15). Kamm and Smith used a fluorometric method to quantitate RNA concentrations in the plasma of healthy individuals (55). Rosi and colleagues used high resolution nuclear magnetic resonance (NMR) spectroscopy to demonstrate RNA molecules complexed with lipid vesicles which were shed from a human colon adenocarcinoma cell line (16). Further characterization of these lipid-RNA complexes demonstrated the vesicles additionally contained triglycerides, cholesterol esters, l

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