Detection of circulating tumour cells and nodal metastasis by reverse transcriptase-polymerase chain reaction technique

Diagnosing and monitoring hepatocellular carcinoma with alpha-fetoprotein: new aspects and applications

Hepatocellular carcinoma is the 5th most common cancer in the world. Prognosis for this disease is poor since hepatocellular carcinoma is mostly diagnosed at an advanced stage. Serum alpha-fetoprotein (AFP) is one of the most common diagnostic markers for hepatocellular carcinoma. However, its diagnostic value is more and more questioned. Therefore, research has focussed on AFP related parameters (AFP mRNA and AFP glycoforms). The aim of this paper is to review the present knowledge on AFP and its related parameters in diagnosing and monitoring HCC. AFP related parameters can be arranged in two types: AFP mRNA and AFP glycoforms. AFP mRNA is a potentially prognostic marker and AFP mRNA assays are based on PCR techniques. The AFP glycoforms have diagnostic potential and assays are based on isoelectric focussing and lectin affinity electrophoretic methods. Up to now the diagnostic use of the AFP related parameters is limited. Although some of them are recommended as a complementary test, they cannot (yet) replace serum AFP as the golden standard of diagnostic markers for hepatocellular carcinoma.

Quantitative RT-PCR detection of colorectal tumor cells in peripheral blood--a systematic review

BACKGROUND

Twenty percent to 40% of patients with node-negative colorectal cancer die of metastatic disease. Detection of cancer cell dissemination has been proposed as a tool to select patients at highest risk for recurrence. In this review, we summarize the evidence for detection with quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) assays of circulating tumor cells (CTCs) in peripheral blood of colorectal cancer patients.

MATERIALS AND METHODS

Pubmed and Embase were systematically searched for all English publications relevant to circulating cancer cells, peripheral blood, quantitative RT-PCR (q-RT-PCR), and colorectal cancer. Cross-references and the "related articles" function were used to broaden the search. Manuscripts reporting on the results of nonquantitative RT-PCR assays were excluded. The study methodology, CTCs detection rates in peripheral blood, and prognostic value were reviewed.

RESULTS

Twelve manuscripts on qRT-PCR were retrieved. Stage dependence was found for detection of CTCs in four of 10 studies. From univariate analysis performed for disease-free survival and overall survival in 4 of 12 studies, there was evidence (P < 0.05) for an effect of the detection of CTCs with qRT-PCR. None of the included trials identified detection of CTCs in peripheral blood as an independent predictor of survival.

CONCLUSION

Quantification of CTCs in peripheral blood holds promise in predicting stage and outcome in colorectal cancer patients. At present, evidence from the literature is too scarce to integrate quantitative RT-PCR assays to detect CTCs into the management of colorectal cancer.

Lymphatic staging in colorectal cancer: pathologic, molecular, and sentinel node techniques

PURPOSE

Accurate staging in colorectal cancer is important to predict prognosis and identify patients who could benefit from adjuvant therapy. Patients with lymphatic metastasis, Stage III/Dukes C, are generally treated with adjuvant chemotherapy. Still, patients without lymphatic metastasis do have relapse as high as 27 percent in five years in Dukes B2. It is hypothesized that these patients have occult (micro)metastasis in their lymph nodes. If these (micro)metastasis can be identified, these patients might benefit from adjuvant therapy. We reviewed the literature on procedures to improve lymph node staging.

METHODS

An extensive literature search was performed in PubMed (www.pubmed.com). Using the reference lists, more articles were found.

RESULTS

We found 30 articles about sentinel node in colorectal cancer describing original series. Some groups reported several studies including the same patients. We reported their largest studies. For all other techniques, we only included key articles.

CONCLUSIONS

Many techniques to improve staging have been described. The finding of occult (micro)metastasis is of prognostic significance in most studies. The sentinel node technique has been recently described for use in colorectal cancer. Although it seems clear that this technique has prognostic potential, it is not yet been shown in a follow-up study. Furthermore, the finding of occult (micro)metastasis in any technique used has not been shown to be clinically significant. Whether to treat patients with adjuvant therapy if occult (micro)metastasis are found needs to be proven in future studies.

The diagnostic significance of the detection of cytokeratin 19 mRNA by quantitative RT-PCR in benign and malignant pleural effusions

OBJECTIVE

To evaluate the diagnostic significance of detecting cytokeratin 19 (CK19) mRNA by quantitative reverse transcription polymerase chain reaction (RT-PCR) in benign and malignant pleural effusions.

METHODS

CK19 mRNA was examined by quantitative RT-PCR and CK19 was detected by Enzyme-linked immunoadsorbent assay (ELISA) in 32 patients with malignant pleural effusions and 35 patients with benign pleural effusions.

RESULTS

On the threshold of 200 copies/microl, the positive rate of CK19 mRNA in patients with malignant pleural effusions was 62.5%. The positive rates of CK19 mRNA and CK19 in the malignant pleural effusions were significantly higher than those in the benign group (P<0.01). Furthermore, the positive rate of CK19 mRNA was higher than that of CK19 in the malignant group (P<0.05).

CONCLUSION

Detection of CK19 mRNA can be a promising diagnostic marker in differential diagnosis of benign and malignant pleural effusions.

Prostate cancer invasion is influenced more by expression of a CD44 isoform including variant 9 than by Muc18

The standard form of cell adhesion glycoprotein CD44 is a metastasis suppressor in prostate cancer. However, we previously showed by RT-PCR and Western blotting that cancer overexpresses unique CD44 variant v7-v10 isoforms. Muc18 is another cell adhesion marker reportedly overexpressed by prostate cancer. Matched frozen section-confirmed tumor and benign tissues were harvested from 10 prostatectomy specimens and tumor was microdissected from two lymph node metastases. Tissues were homogenized for RNA preparations, and RT-PCR was performed for the CD44v7-v10 sequence. In cultured prostate cancer cells, we caused RNA interference against CD44v9 and/or Muc18. We used PC3M cells and a derivative cell line called G(s)alpha, that constitutively expresses this G-protein and is more invasive. Lipofection was performed for a green fluorescent protein plasmid and for two 22-mer DNA fragments, cloned into a plasmid expression vector to generate hairpin, interfering dsRNA. Assays for invasion into Matrigel, a basement membrane matrix, were performed in 4-5 experiments. RT-PCR demonstrated expression of a 608 bp band representing CD44v7-v10 or a 638 bp band of CD44v6-v10 in prostate cancer tissues and metastases but not benign tissue. Cultured G(s)alpha cells overexpressed CD44v9 by comparison with PC3M cells. At 90 h after 6-hour lipofection, protein silencing was evident by Western blots. Silencing the CD44v9 expression reduced invasiveness into Matrigel to 21.6+/-7.0% in PC3M cells (P<0.001) and 31.2+/-18.3% in G(s)alpha cells (P=0.001), compared to cells exposed to transfection vehicle alone. Silencing Muc18 expression reduced invasiveness to 76.9+/-13.5% of the control value in PC3M cells (P<0.05) and 84.8+/-29.9% in G(s)alpha cells (P=0.18). Prostate cancer invasion is facilitated more by its overexpression of CD44 variant 9 than by Muc18. Its relative overexpression by G(s)alpha cells is a novel finding, suggesting a link between signal transduction and cell adhesion marker expression.

Colon cancer: prevalence, screening, gene expression and mutation, and risk factors and assessment

Colon cancer detection at an early stage and identifying susceptible individuals can result in reduced mortality from this prevalent cancer. Genetic events leading to the development of this cancer involve a multistage progression of adenoma polyps to invasive metastatic carcinomas. Currently, there is no satisfactory screening method that is highly specific, sensitive, or reliable. Dietary patterns associated with the greatest increase in colon cancer risk are the ones that typify a diet rich in fat and calories, and low in vegetable, fruits, and fibers. Genetic susceptibility to environmental carcinogenesis must be factored into the risk assessment for this cancer. Many genes have been shown to be associated with increased expression and mutations in colorectal cancer patients. These genes have been reviewed; it is hoped that by carefully selecting a number of them, a molecular approach that is suitable for arriving at a tumorigenic expression index is developed, which will reliably detect this cancer at an early stage (i.e., before it metastasizes), especially in exfoliated samples (e.g., stool and blood), so that appropriate intervention strategies can be implemented. Illustrated herein is the utility of employing real-time reverse transcriptase polymerase chain reaction (RT-PCR) to quantitatively measure gene expression, and develop an index that is specific for this cancer, which if perfected may result in a reliable and sensitive screening technique for colorectal cancer detection.

Prospective evaluation of circulating hepatocytes by alpha-fetoprotein messenger RNA in patients with hepatocellular carcinoma

BACKGROUND

The significance of alpha-fetoprotein (AFP) messenger RNA as a surrogate marker for isolated tumor cells in the blood of patients with hepatocellular carcinoma (HCC) is controversial. Our goals were to correlate AFP mRNA with tumor recurrence and overall survival after patients with HCC received curative operations and to analyze AFP mRNA findings in control patients.

METHODS

In this prospective controlled study, RNA was purified from the blood of 85 patients with HCC before, during, and after therapy and from 116 control patients. Complementary DNA synthesis by reverse transcriptase and polymerase chain reaction amplification was performed with primers specifically for the AFP gene. Patients with HCC were divided into 4 subgroups depending on the therapy performed: (1) orthotopic liver transplantation (OLT), (2) resection, (3) transarterial chemoembolization, and (4) no therapy.

RESULTS

AFP mRNA was detected in 28% of the patients with HCC and 3% of the control patients (P <.01) before therapy. Of patients with HCC and OLT, 2 of the 6 patients who were AFP mRNA positive had a recurrence; none of the 4 patients who were negative had a recurrence. In the HCC patients who underwent tumor resection or received no therapy, the survival rates did not differ between patients who were AFP mRNA positive and negative (P =.21 and P =.94, respectively). After the tumor resection, no difference in survival at 2 years was evident in patients who were AFP mRNA positive versus those who were AFP mRNA negative. In the HCC patients who had curative operations (OLT and resection) the sensitivity and specificity of this test for tumor recurrence were 73% and 53%, respectively, excluding surgical mortality. The International Union Against Cancer tumor stages in the subgroups of OLT and resection showed no differences between patients with positive and negative findings (P =.76 and P =.15, respectively). AFP mRNA results and serum AFP levels revealed no correlation (P =.45).

CONCLUSIONS

The qualitative measurement of AFP mRNA in the blood of patients with HCC is not a clinically relevant method for determining therapy and prognosis, especially if AFP mRNA is detected during the surgical procedure or any other liver manipulation.

Molecular pathology of tumor metastasis. II. Molecular staging and differential diagnosis

Molecular Pathology of Tumor Metastasis With the development of non-invasive methods, diagnosis of metastasis from various solid malignancies has become a routine task for diagnostic pathology. However, the differential diagnosis between primary and metastatic cancers and the precise identification of various metastatic cancer types requires the coordinated use of various morphological (light- and electron microscopic-), immunological and molecular techniques. The detection of the lymphatic spread of the primary tumor may now based on the sentinel lymph node technology while the identification of the hematogenous progression may be based on the analysis of the peripheral blood and the bone marrow. More and more frequently these techniques employ highly sensitive immunological and molecular techniques. Accordingly, clinical staging is now confronted with the results of molecular staging, where the only techniques which are able to detect cancer cells are immunocytochemistry or nucleic acid-based methodology. Although several clinical studies have provided evidences for the impact of the immunocytochemistry-based identification of micrometastases on the survival of patients with various type of cancers, none of these methods have become part of standard diagnostic protocols. Although more sensitive molecular techniques are being introduced to identify micrometastasis, their clinical significance is yet unknown. Multicentric clinical trials are now warranted to establish the clinical impact of molecular staging in various cancer types. Without the integration of these methods into the prognostic/predictive pathological protocols it is difficult to envision significant improvement in the results of cancer therapy.

Functionality of circulating DNA: the hypothesis of genometastasis

The detection of free, circulating tumor DNA in the plasma of cancer patients opens up new possibilities for the diagnosis and prognostication of cancer. Whatever might be the mechanism for the presence of such DNA, it is now clear that oncogenes can circulate in the plasma fraction of blood and we can now ask whether this phenomenon has potentially important implications in cancer patients. The results of our experiments, together with previous observations of other authors, have led us to propose the "Hypothesis of Genometastasis", which suggests that metastases might develop as a result of transfection of susceptible cells in distant target organs with dominant oncogenes that circulate in the plasma and are derived from the primary tumor.

Telomerase and oral cancer

The development of malignant neoplasms is a multistep process and it is believed that multiple genetic alterations are involved. The progression of neoplastic lesions is also characterized by reactivation of telomerase, a ribonucleoprotein complex enzyme that adds telomere repeats at the ends of chromosomes. In view of the close association between telomerase and malignancy, this molecule may prove to be a useful marker for malignancy. This review focuses on the diagnostic and therapeutic potential of telomerase. The experimental data for telomerase assays with the potential for oral cancer detection and diagnosis are also reviewed.

Minimal residual disease in gastrointestinal cancer

Tumor progression after curative resection of gastrointestinal carcinomas is probably caused by pre- or intraoperative tumor cell dissemination. Disseminated tumor cells are generally detected by immunohistochemistry- or PCR-based molecular-biology methods. A consensus on which is the most adequate detection method has not yet been found, which makes the comparison of data difficult. The prognostic relevance of disseminated cells has been shown, at least in part, for esophageal, gastric, pancreatic, and colonic cancer. The data regarding hepatocellular cancer is conflicting. This article gives a critical review of tumor cell detection in gastrointestinal cancer.

Lack of prognostic influence of circulating tumor cells in peripheral blood of patients with colorectal cancer

BACKGROUND AND AIMS

Circulating tumor cells in peripheral blood may be detected using high-sensitivity molecular techniques in several types of solid neoplasms, but their significance in colorectal cancer is controversial. The aim of this study was to assess the prognostic value of carcinoembryonic antigen (CEA) messenger RNA (mRNA) detection in peripheral blood samples from patients with colorectal cancer.

METHODS

Peripheral vein blood samples from 95 consecutive patients with histologically confirmed colorectal carcinoma were obtained immediately before surgery to determine the presence of circulating tumor cells by use of a reverse-transcription polymerase chain reaction targeting CEA mRNA. Endpoints of the study were disease-free and overall survival. Results are referred to the whole series and, more importantly, to the 68 patients who underwent surgery for cure.

RESULTS

After a median follow-up of 42 months, 19 of 68 patients (28%) operated on for cure had tumor relapse. In addition, 50 of 68 patients (73%) were alive. The probability of disease-free and overall survival was dependent on lymph node metastases and degree of differentiation, but not on the presence of circulating tumor cells (disease-free survival: relative risk, 1.00; 95% confidence interval [CI], 0.39-2.22, P = 0.99; overall survival: relative risk, 0.91, 95% CI, 0.34-2.43; P = 0.84). Similar results were obtained when all 95 patients with colorectal cancer were analyzed (disease-free survival: relative risk, 1.11; 95% CI, 0.63-1.95; P = 0.71; overall survival: relative risk, 1.21; 95% CI, 0.63-2.30, P = 0.55).

CONCLUSIONS

Preoperative detection of blood circulating tumor cells by means of reverse-transcription polymerase chain reaction of CEA does not have prognostic significance in patients with colorectal cancer.

Experimental evidence does not support use of the "no-touch" isolation technique in colorectal cancer

PURPOSE

The benefits of the "no-touch" isolation technique usually performed to prevent the circulation of tumor cells are not evident. The aim of this study was to determine whether conventional surgical procedures for treatment of colon cancer could provoke the circulation of tumor cells detected by a genetic technology.

METHODS

Sixteen patients undergoing resection for colorectal cancer and two patients with irresectable tumors were studied. No patient showed liver or lung metastasis. With specific primers for carcinoembryonic antigen, we used reverse transcriptase-polymerase chain reaction to analyze tumor biopsy specimens and blood samples obtained from the antecubital vein before and after surgery and from the main drainage vein of the tumor when the tumor had been extracted. Peritoneal fluid was also collected in irrecsectable cases.

RESULTS

Amplification of cDNA with carcinoembryonic antigen-specific primers was achieved with all tumor biopsies and samples of peritoneal fluid. In two patients carcinoembryonic antigen reverse transcriptase-polymerase chain reaction products were detected in antecubital vein blood before surgery and in one of them also after surgery. Only in one patient (Dukes C) were carcinoembryonic antigen reverse transcriptase-polymerase chain reaction products detected from the main drainage vein of the tumor. In serial dilution experiments we determined that the limit of detection of this method was ten tumor cells in 2 ml of blood.

CONCLUSION

Our data suggest that the use of no-touch isolation techniques in colorectal cancer is not justified, based on lack of evidence indicating the detachment of cells from the tumor at surgery.

Detection of genomically-tagged cancer cells in different tissues at different stages of tumor development: lack of correlation with the formation of metastasis

Genetic detection of tumor cells in blood, lymphatic nodes or bone marrow using reverse transcription and polymerase chain reaction (PCR) is quite attractive because it allows the early diagnosis of cancer dissemination. Unfortunately, this type of detection strategy cannot be applied to solid parenchymas, because they usually share with tumor cells the mRNA markers. To avoid this impediment, we have developed an experimental model of cancer using cells with a genome-associated tag. DHD/K12-PROb cancer cells were stably transfected with pcDNA3.1CAT. Approximately 10(6) transfected cells (DHD-CAT cells) were injected subcutaneously into the chest of BD-IX rats. Animals were divided into 11 groups according to the time between injection of tumor cells and euthanasia. An additional 'untagged group' was injected with untransfected cells (DHD-Wild). Blood and tissues samples were collected after euthanasia. Macroscopic and microscopic analysis was done. To detect circulating tumor cells or their presence in peripheral organs, we performed PCR with nested primers to amplify chloramphenicol acetyl transferase-encoding (CAT-encoding) DNA sequences. The minimum number of cells that yielded detectable cells routinely was 2 in 10(6). No modification of cancer aggressiveness was observed in DHD-CAT cells. DHD-CAT cells were detected by PCR in lung from the 1st week after inoculation, in liver, spleen and kidney from the 3rd week and in the blood from the 5th week. All animals analyzed 12 weeks after injection showed lung metastases. Metastases in liver, spleen or kidney, either microscopic or macroscopic, were never detected. We have developed an experimental model of cancer based on genomic tagging of tumor cells that allows the detection of small numbers of cells in all organs and the blood. The presence of cancer cells in parenchymas detected with molecular technology does not correlate with the development of clinically relevant metastases.

Detection of cytokeratins 19/20 and guanylyl cyclase C in peripheral blood of colorectal cancer patients

The clinical significance of detecting supposed tumour cell-derived mRNA transcripts in blood using the polymerase chain reaction (PCR) remains unclear. We have used a fully quantitative 5′-nuclease RT-PCR assay to screen for the expression of cytokeratins (ck) 19 and 20 and guanylyl cyclase C (GCC) in the peripheral blood of 21 healthy controls and 27 colorectal cancer patients. Expression of cytokeratin 19 and 20 mRNA was detected in 30% and 100% of samples, respectively, taken from healthy volunteers. There was no apparent difference in ck19 and ck20 mRNA transcription levels between controls and patients, or between patients with different Dukes' stages. While GCC mRNA was detected in only 1/21 control samples, it was expressed in approximately 80% of patients, although again there was no correlation between GCC levels and disease stage. Transcription levels of all three markers varied considerably between samples, even between samples taken from the same person at different times. We conclude that neither ck19 nor ck20 are reliable markers for the detection of colon epithelial cells in peripheral blood and that an evaluation of the usefulness of GCC awaits further longitudinal studies. © 1999 Cancer Research Campaign