Summary Increased understanding of the molecular basis of colorectal cancer and recognition that extracellular DNA circulates in the plasma and serum of cancer patients enables new approaches to detection and monitoring. We used a polymerase chain reaction (PCR) assay to demonstrate mutant K-ras DNA in the plasma or serum of patients with colorectal cancer. Plasma or serum was fractionated from the blood of 31 patients with metastatic or unresected colorectal cancer and from 28 normal volunteers. DNA was extracted using either a sodium chloride or a gelatin precipitation method and then amplified in a two-stage PCR assay using selective restriction enzyme digestion to enrich for mutant K-ras DNA. Mutant K-ras DNA was detected in the plasma or serum of 12 (39%) patients, all confirmed by sequencing, but was not detected in any of the normal volunteers. K-ras mutations were detected in plasma or serum regardless of sex, primary tumour location, principal site of metastasis or proximity of chemotherapy and surgery to blood sampling. Tumour specimens available for 19 of the patients were additionally assayed for ras mutations and compared with blood specimens. Our results indicate mutant K-ras DNA is readily detectable by PCR in the plasma or serum of patients with advanced colorectal cancer. Thus, plasma-or serum-based nucleic acid amplification assays may provide a valuable method of monitoring and potentially detecting colorectal cancer.
Plasma DNA assays for the detection of mutations in K-ras codon 12 may provide a feasible method to screen populations for somatic mutations frequently found in neoplasms. The clinical utility of using this test in screening populations requires further study.
CD4+ T cells can be expanded in vivo in cancer patients, which results in increased CD4:CD8 ratios. The timing of pheresis in relation to CTX administration influences the degree of CD4 expansion. Tumor responses with this regimen were observed in a variety of tumors, including melanoma and non-Hodgkin's lymphoma; a high percentage of patients had at least some tumor regression from the regimen that produced the greatest CD4+ T-cell expansion.
Cancer is commonly associated with the inappropriate mRNA expression of nonmutated genes. Recently, several tumor‐associated RNA species, including tyrosinase mRNA and telomerase RNA, have been demonstrated in plasma and serum. The presence of tumor RNA in plasma and serum affords the opportunity to diagnose or stratify patients with cancer when tissue is not readily available. To exemplify the potential for pharmacogenomic and phenotypic stratification of the cancer patient, we evaluated serum for 5T4 mRNA. 5T4 is a trophoblast glycoprotein frequently overexpressed in epithelial malignancies that provides a potential target for cancer therapeutics. Serum was collected from 19 patients with advanced breast cancer (5 patients) or non‐small‐cell lung cancer (14 patients), and from 25 normal control volunteers having amplifiable RNA. RNA extracted from the serum was RT‐PCR amplified using heminested, two‐stage reactions, with products detected by gel electrophoresis. 5T4 mRNA was reproducibly detected in 8/19 (42%) cancer patient sera, including 2/5 breast cancer patient sera and 6/14 lung cancer patient sera, but in only 3/25 (12%) normal control sera (p= 0.035). The potential for circulating mRNA to identify patients who might benefit from a 5T4‐directed therapy offers an example of the utility of circulating RNA as a tumor marker.
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