Oncogenic transformation induced by cell-free nucleic acids circulating in plasma (genometastasis) remains after the surgical resection of the primary tumor: a pilot study.

BACKGROUND: The oncogenic transformation by cell-free nucleic acids circulating in plasma has been named as genometastasis. The feasibility of this phenomenon has been demonstrated and now it is necessary to value the impact of this phenomenon and to determine what conditions could promote or inhibit it. The goal of this study was to examine the transforming ability of plasma from colorectal cancer patients in a long-term follow-up after the surgical excision of the primary tumor, and to try correlate it with the clinical picture of patients. MATERIALS AND METHODS: Blood samples were taken from eight patients with K-ras-mutated colorectal tumors, who were under surgical primary tumor resection at least 2 years before. Plasma was isolated by two centrifugations and added to cultures of NIH-3T3 cells and human adipose-derived stem cells (hASCs). In two cases, plasma was separated from cells by a membrane with 0.4-µm pores. The presence of mutated and non-mutated human K-ras sequences was tested by real-time PCR in cultured cells. After 30 days, cells were subcutaneously injected into athymic nude mice in order to test their ability to generate tumors. RESULTS: In four of the eight patients analyzed after surgery, tumor DNA was detected in plasma. Plasmas from three of them were able to oncogenically transform NIH-3T3 cells in culture and, when those cells were injected in mice, carcinomas were generated. After a 2-year follow-up, metastases were found in two of the three patients whose plasmas were able to transform cells, and in two of the four in whom plasma tumor DNA was not detected. Thus, after a mean follow-up of 29.5 months, only four of 13 patients (30.8%) were alive and disease-free. CONCLUSION: Primary tumor resection does not assure a complete clean of blood of circulating oncogenes, in spite of a disease-free clinical picture. Moreover, in some cases plasma kept their oncogenic capabilities. The value of these findings as prognosis factor remains unclear and needs further investigations.

NIH-3T3 fibroblasts cultured with plasma from colorectal cancer patients generate poorly differentiated carcinomas in mice.

The ability of cells to undergo cellular transitions, in particular, to switch between epithelial and mesenchymal states, might be highly advantageous during the progression of carcinoma. Using histological and immunohistochemical techniques, we here show that the injection into mice of spontaneously transformed NIH-3T3 cells generated fusocellular sarcomas, whereas NIH-3T3 cells that had been transformed by culturing with plasma from colorectal cancer patients gave rise to tumors that phenotypically resembled the carcinomas of the original cancer patients. Thus, plasma from cancer patients is able to transform NIH-3T3 fibroblasts into malignant epithelial-like cells, suggesting that such cells might undergo mesenchymal to epithelial transition during plasma-induced transformation.

The concentration of deoxyribonucleic acid in plasma from 73 patients with colorectal cancer and apparent clinical correlations.

BACKGROUND: Detection of cell-free plasma DNA has considerable potential as a tool for the diagnosis and assessment of the prognosis of many types of cancer. The aim of the present study was to quantify, by spectrophotometry, the cell-free DNA in plasma samples from patients with colorectal cancer at different stages of the disease and to attempt to correlate the resultant values with the clinical picture. METHODS: We reviewed the medical reports of 73 patients, who had undergone resection of primary colorectal cancer. Samples of blood had been taken from each patient immediately prior to surgery. DNA was extracted from samples of plasma and quantified, by spectrophotometry, after a storage period of no longer than 2 years in 89% of the cases examined. RESULTS: The mean(+/-S.D.) concentration of DNA in plasma samples was 108+/-156 ng/microl. We found a statistically significant correlation between the concentration of DNA and the presence of metastases (mainly liver metastases). CONCLUSION: The detection and quantitation of cell-free DNA in plasma, using this simple technique, might be of clinical value for the surveillance of colon cancer patients and the detection of metastases.