title: Quantitation of cell-free DNA and RNA in plasma during tumor progression in rats.
abstract: BACKGROUND
  To clarify the implications of cell-free nucleic acids (cfNA) in the plasma in neoplastic disease, it is necessary to determine the kinetics of their release into the circulation.
  
  
  METHODS
  To quantify non-tumor and tumor DNA and RNA in the plasma of tumor-bearing rats and to correlate such levels with tumor progression, we injected DHD/K12-PROb colon cancer cells subcutaneously into syngenic BD-IX rats. Rats were sacrificed and their plasma was analyzed from the first to the eleventh week after inoculation.
  
  
  RESULTS
  The release of large amounts of non-tumor DNA into plasma was related to tumor development from its early stages. Tumor-specific DNA was detected in 33% of tumor-bearing rats, starting from the first week after inoculation and at an increasing frequency thereafter. Animals that were positive for tumor DNA in the plasma had larger tumors than those that were negative (p = 0.0006). However, the appearance of both mutated and non-mutated DNA fluctuated with time and levels of both were scattered among individuals in each group. The release of non-tumor mRNA was unaffected by tumor progression and we did not detect mutated RNA sequences in any animals.
  
  
  CONCLUSIONS
  The release of normal and tumor cfDNA into plasma appeared to be related to individual-specific factors. The contribution of tumor DNA to the elevated levels of plasma DNA was intermittent. The release of RNA into plasma during cancer progression appeared to be an even more selective and elusive phenomenon than that of DNA.
authors: Experimental Research Unit, General University Hospital of Albacete, C/ Hermanos Falcó 37, 02006, Albacete, Spain. doloresg@sescam.jccm.es
authors: Dolores C
authors: DC
authors: García-Olmo
authors: María G
authors: MG
authors: Picazo
authors: Inmaculada
authors: I
authors: Toboso
authors: Ana I
authors: AI
authors: Asensio
authors: Damián
authors: D
authors: García-Olmo
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D004247:DNA / Q000097:blood* / Q000235:genetics; D018450:Disease Progression; D005260:Female; D008297:Male; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000097:blood; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics; D012313:RNA / Q000097:blood* / Q000235:genetics; D051381:Rats
chemical_list: C528430:Kras protein, rat; D012313:RNA; D004247:DNA; D016283:Proto-Oncogene Proteins p21(ras)
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