Detection of melanoma cells in peripheral blood by means of reverse transcriptase and polymerase chain reaction

Preoperative TNM-classification is a better prognostic indicator for recurrence of hepatocellular carcinoma after liver transplantation than albumin mRNA in peripheral blood. Liver Transplant Oncology Group

BACKGROUND/AIM

Survival after orthotopic liver transplantation for hepatocellular carcinoma is limited by a high rate of tumor recurrence. A polymerase chain reaction assay based on the detection of albumin mRNA expression in peripheral blood for detection of hematogenous micrometastasis of hepatocellular carcinoma has been described, which may help to select candidates for orthotopic liver transplantation.

METHODS

The prognostic value of a highly sensitive nested reverse transcription-polymerase chain reaction assay was evaluated in comparison with the TNM-classification of the International Union against Cancer in a population of liver transplant candidates.

RESULTS

Eighty patients with liver disease and 42 control patients were evaluated. Six of 21 patients with hepatocellular carcinoma and 11 of 59 patients with other diseases of the liver were positive for albumin reverse transcription-polymerase chain reaction, making this assay an indicator of ongoing liver damage without absolute specificity for hepatocellular carcinoma. Twelve patients with hepatoma were followed after liver transplantation and seven of those patients had a tumor recurrence within 12 months. Six of these patients with recurrence had International Union against Cancer stage IV A tumors preoperatively, while only one of them was positive for albumin reverse transcription-polymerase chain reaction before transplantation. Only one patient with a stage I to III tumor had a recurrence within 12 months.

CONCLUSIONS

Detection of albumin mRNA in peripheral blood by reverse transcription-polymerase chain reaction seems to be an unreliable marker for assessing hematogenous spread of hepatocellular carcinoma. With International Union against Cancer stage IV A being a much better predictor of tumor recurrence, the practical value of albumin mRNA reverse transcription-polymerase chain reaction for patient selection in liver transplant candidates seems to be very limited.

Molecular detection of cancer cells by competitive reverse transcription-polymerase chain reaction analysis of specific CD44 variant RNAs

BACKGROUND

CD44 is a cell surface glycoprotein implicated in such diverse biologic processes as lymphocyte activation and homing, extracellular matrix adhesion, and cellular migration. Primary transcripts of the CD44 gene can be alternatively spliced to produce a variety of messenger RNA (mRNA) species. The standard form of CD44 mRNA contains sequences from at least 20 genomic exons; variant mRNAs contain sequences from one or more additional exons (v1-10). Predominant expression of a specific CD44 variant, i.e., CD44v8-10, in several human carcinomas has been described previously. In this study, we developed a novel molecular approach for detecting cancer cells that overexpress CD44v8-10 mRNA.

METHODS

After finding that CD44v8-10 was predominantly expressed in non-small-cell lung and bladder carcinomas and that CD44v10 was predominantly expressed in leukocytes, we developed a competitive reverse transcription-polymerase chain reaction assay (CC-RT-PCR) that allows quantification of the relative expression of these two mRNA species in clinical specimens (i.e., determination of a v8-10/v10 ratio). CC-RT-PCR analysis was applied to pleural effusion specimens from patients with benign or malignant lung diseases as well as to spontaneously voided urine samples from patients with benign or malignant urologic diseases.

RESULTS

Fifty two of 54 samples from patients with benign diseases expressed CD44v10 predominantly (v8-10/v10 ratio < or = 0.65), whereas 46 of 61 samples from patients with malignant diseases expressed CD44v8-10 predominantly (v8-10/v10 ratio > 1.00) (two-sided P < .001). CC-RT-PCR detected predominant expression of CD44v8-10 in cytologically negative samples from 11 patients who were later diagnosed with malignant disease.

CONCLUSIONS

CC-RT-PCR analysis of CD44v8-10 expression could be an important adjunct to cytologic examination in cancer diagnosis, especially in detecting exfoliated cancer cells in pleural effusions and urine.

Detection of tyrosinase mRNA in formalin-fixed, paraffin-embedded archival sections of melanoma, using the reverse transcriptase in situ polymerase chain reaction

Most studies of the reverse transcriptase in situ polymerase chain reaction technique have reported results from assessments of cultured cells, frozen sections, and cytospin preparations. For application to routine diagnosis, it will be necessary to adapt the technique for use with formalin-fixed, paraffin-embedded tissues, the materials that are generally available. We have evaluated the feasibility of such an approach, using surgical pathology archival material from 25 UCLA patients: 15 tissues from primary and metastatic melanoma, 7 from nonmelanocytic tumors, including cancer of the lung, colon, kidney and skin and a thyroid adenoma, and 3 nontumorous tissues. Seven of 15 melanoma tissues gave a strong positive signal, 5 gave a weak signal, and 3 were negative. None of the 10 nonmelanoma tissues gave a positive signal. The specific reaction product was mainly located in the cytoplasm. None of the nonmelanocytic tumors or normal tissues demonstrated this pattern of cytoplasmic staining. Some nonspecific nuclear staining was observed in melanocytic and nonmelanocytic tumors and must not be overread as a true positive result. It is possible to detect tyrosinase mRNA in formalin-fixed, paraffin-embedded tissue sections of melanoma, but the technique remains too demanding for routine application.

Clinical usefulness of RT-PCR detection of hematogenous prostate cancer spread

Understaging is commonly associated with therapeutic failure of surgical intervention in apparently localized prostate cancers. Methods that specifically detect prostate cancer cells in the circulation may be able to identify metastatic cancers and thus aid in the selection of the most adequate therapy. The high sensitivity and specificity of the reverse transcriptase-polymerase chain reaction (RT-PCR) encouraged various groups to investigate the mRNA expression of prostate-specific markers in the peripheral blood of patients with prostate cancer. However, probably due to methodological differences, many contradictory results have been obtained with the markers studied so far: prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSM). For this reason, clinical decisions should not be based yet on RT-PCR results. Future research and long-term follow-up on the patients may point out whether RT-PCR assays, following appropriate standardization, will have an additive value in prostate cancer staging and in prediction of tumor progression.

New evidence for presence of tyrosinase in substantia nigra, forebrain and midbrain

Tyrosinase and tyrosinase-related proteins (TRP-1 and TRP-2) are essential for melanin synthesis and are expressed in neural crest-derived melanocytes and in the pigment epithelium of the retina. Recent results suggest expression of all three proteins within the central nervous system. We performed a transgenic assay using beta-galactosidase as reporter gene to monitor tyrosinase promoter activity in vivo. During embryogenesis, we found expression in several locations of developing forebrain and midbrain. Tyrosinase, TRP-1 and TRP-2 had been equally found in extracts of adult mouse brain. In adult brain, we detected tyrosinase promoter activity in cortex, olfactory system, hippocampus, epithalamus and substantia nigra, areas corresponding to positive staining during embryogenesis. Thus, tyrosinase promoter is active throughout murine brain development, and tyrosinase could be implicated in neuromelanin formation in the substantia nigra, and in neurodegenerative disorders like Parkinson's disease.

Nucleic acid-based methods for the detection of cancer

Continued elucidation of the genetic changes that drive cancer progression is yielding new and potentially powerful nucleic acid-based markers of neoplastic disease. Pilot studies indicate that these markers can be used to detect cancer cells in a variety of clinical settings with unprecedented precision. Nucleic acid-based markers may prove to be valuable tools for early detection of cancer in asymptomatic individuals, for confirmation or exclusion of a cancer diagnosis that is based on suspicious but nondiagnostic clinical material, for assessment of tumor burden in cancer patients, and for assessment of response to preventive approaches applied to healthy individuals who are at high risk of developing cancer. Examples of these markers, their potential applications, and the current practical limitations on their clinical use are reviewed here.

Sub-lethal effects of exposing the human melanoma cell line SKmel-23 to 532 nm laser light

The human melanoma cell line SKmel-23 has been used to investigate the sub-lethal damage that can occur as a result of exposing melanin containing cells to light (532 nm) from a frequency doubled Q-switched (Nd:YAG) laser. A dose response curve was obtained, which indicates that at energy levels of 0.6 J/cm2 and below no effect on either the viability or growth rate of the cell line was observed. Above this, cells rapidly died and at an energy level of 2.0 J/cm2, only approximately 15% of cells survived. This contrasts with the effects on the G361 melanoma line, which contains far less melanosomes, as an LD50 for this cell line was approximately 5.5 J/cm2. Exposing SKmel-23 cells to 0.4 J/cm2 of 532 nm light results in a diminution of the number of melanosomes within cells as well as a marked decrease in melanin content, as determined by spectrophotometric assay and electron microscopy. Using the reverse transcriptase polymerase chain reaction technique, the reduction in melanin content of the cells was accompanied by a selective decrease in mRNA coding for tyrosinase, the first enzyme in the biosynthetic pathway for melanin. No decrease in the mRNA coding for the GAPDH protein was observed. Our finding has implications for understanding the control processes that regulate the melanin content of cells and suggests that the model described can be used to further investigate changes that may occur in cells as a result of their exposure to sub-lethal levels of laser light.

Detection of prostate specific antigen messenger RNA from pelvic lymph node in prostate cancer

We have adapted a sensitive method to detect pelvic lymph node metastasis using reverse transcriptase-polymerase chain reaction (RT-PCR) with primers specific for prostate-specific antigen (PSA) gene. Fine needle aspiration biopsy (FNAB) of pelvic lymph nodes was performed in 25 patients with prostate cancer. Each aspirated sample (0.05-0.1 mL) was divided into two parts: one for RNA extraction and RT-PCR to detect the fragment of PSA mRNA, and the other to smear on a slide glass for conventional cytology. RT-PCR detection of PSA gene was positive in 12 cases of FNAB samples, which included not only all 6 cytologically positive and 2 cytologically class III cases but also 4 of 17 cytologically negative cases. RT-PCR of FNAB samples of all 20 cases of bladder cancer were negative for the detection of PSA gene. RT-PCR for detection of PSA gene in FNAB samples may become a new diagnostic technique for detection of early lymph node metastasis in prostate cancer and an additional tool for cytologic diagnosis of prostate cancer.

Detection of pancreatic and gastric cancer cells in peripheral and portal blood by amplification of keratin 19 mRNA with reverse transcriptase-polymerase chain reaction

Reverse transcriptase-polymerase chain reaction (RT-PCR) targeted at keratin 19 mRNA was applied to detect circulating cancer cells in the peripheral and portal blood of pancreatic and gastric cancer patients. Keratin 19 mRNA expression was studied by RT-PCR in cancer tissues (12 pancreatic and 15 gastric cancers) and in peripheral and/or portal blood samples from patients with pancreatic cancer (stage I, n = 5; stage II, n = 1; stage III, n = 15; stage IV, n = 19), gastric cancer (stage la,b, n = 28; stage II, n = 9; stage IIIa,b, n = 5; stage IVa,b, n = 7) and benign pancreatic diseases (n = 7). Peripheral blood samples from 50 healthy volunteers served as controls. RT-PCR was conducted in duplicate in each sample, and only samples showing keratin 19 transcript in both determinations were considered as being positive. All the pancreatic and gastric cancers, but none of the control blood samples, were found to be positive. Dilution study using pancreatic cancer cells serially mixed against peripheral blood showed that detection sensitivity was more than one cancer cell in 10(6) peripheral blood mononuclear cells. In pancreatic cancer patients, RT-PCR analysis of the portal blood samples gave positive results in one stage III and one stage IV patient, and that of peripheral blood samples gave positive results in 2 stage IV patients. No positive results were obtained in any of the blood samples from gastric cancer patients. Our results indicate that incidence of circulating cancer cells is unexpectedly very low even in advanced pancreatic and gastric cancer patients.

Minimal illegitimate levels of cytokeratin K19 expression in mononucleated blood cells detected by a reverse transcription PCR method (RT-PCR)

Cytokeratin K19 (CK19) expression was evaluated by a reverse transcription PCR method (RT-PCR) in the RNA obtained from peripheral blood stem cell collections (PBSC) from four patients with breast cancers (BC) and 34 mononucleated blood cell (MBC) negative controls (17 PBMC from normal subjects 12 PBSC from different types of leukaemias--M3, M4Eo, M2, etc.--and two from patients with Hodgkin's lymphoma; and three bone marrow (BM) collections). Two BC tissues were taken as positive controls. The method studied (Datta YH, Paul T, Adams PT, Drobyski WR. Sensitive detection of occult breast cancer by reverse transcription polymerase chain reaction. J Oncol 1994;12:475-8) is sensitive enough to allow the detection of CK19 transcripts in a 10(-6) dilution of cDNA reverse transcribed from 1 microgram of BC RNA, but CK19 transcripts were also detected in 64% of the RNA obtained from the MBC controls. However, the amplified product detected in the control samples represents the transcript of the CK19 gene as confirmed by the results of Mae III digestion. It should be pointed out that although the CK19 expression was detected, the levels of expression in PBMC were almost negligible for they disappeared at 1:5 cDNA dilution. Moreover, a direct relationship between the number of BC cells added to PBMC and the increasing dilution levels of the cDNA necessary to prevent CK19 expression was observed. This allows us to conclude that the cDNA dilutions make it possible to distinguish the false from the true positive samples and that, in addition, the cDNA dilutions inform about the degree of BC cell contamination.

Ectopic expression of target genes may represent an inherent limitation of RT-PCR assays used for micrometastasis detection: studies on the epithelial glycoprotein gene EGP-2

Our objective was to develop and study the feasibility of a quantitative, nested reverse-transcription polymerase chain reaction (RT-PCR) assay for detection of micrometastatic, epithelial tumor cells using the epithelial glycoprotein EGP-2 gene as a target. Several carcinoma cell lines and peripheral blood samples of 10 healthy volunteers were screened for levels of EGP-2 mRNA. The assay included EGP-2 competitor molecules, carrying an internal deletion, that had been titrated by limiting dilution. Seven carcinoma cell lines showed a wide spectrum of EGP-2 mRNA expression levels, with the highest values (20-100 molecules/cell) seen in 3 breast-cancer cell lines. Unexpectedly, a consistent low level of EGP-2 mRNA expression (0.0004 molecules/cell) was observed in peripheral blood mononuclear cells, probably representing ectopic non-functional expression. Because of this background level, spiking experiments with T47D breast-carcinoma cells added to blood mononuclear cells exhibited a detection limit that was not better than approximately one tumor cell in 2 x 10(4) normal cells. Together with the considerable variation of EGP-2 transcript levels that is observed in different carcinoma cell lines, the extent of expression in normal blood cells would prevent a reliable estimation of low numbers of carcinoma cells in clinical samples. A similar situation might well apply for other target genes. This emphasizes the need for a critical evaluation of the different steps involved in the methods used for RT-PCR detection of micrometastatic tumor cells.

Prospective evaluation of circulating hepatocytes by alpha-fetoprotein mRNA in humans during liver surgery

OBJECTIVE

The objective of this study was to analyze the specificity of detecting liver tumor cell dissemination by alpha-fetoprotein (AFP) mRNA in peripheral blood.

SUMMARY BACKGROUND DATA

Alpha-fetoprotein mRNA has been used for the detection of circulating micrometastatic tumor foci of hepatocellular carcinoma (HCC); however, the interpretation of the results has been equivocal.

METHODS

Sixty-four consecutive patients with malignant HCC (n = 20), liver metastases (n = 27), or nonmalignant (n = 17) liver diseases undergoing partial or total hepatectomy and orthotopic liver transplantation were included in this prospective study from January to July 1995. Peripheral blood samples were obtained before surgery, during surgery, and after surgery (range, 6-15 months). Total mRNA was extracted from nucleated cells, and cDNA synthesis and polymerase chain reaction amplification (nested polymerase chain reaction in one tube) were performed with specific AFP primers.

RESULTS

Preoperative AFP mRNA was detected in 20 patients (17%), of which 5 of 20 had HCC. Intraoperative assessment showed positive AFP mRNA values in a total of 34 patients (53%) with various causes, of which 8 of 20 (40%) had HCC, 17 of 27 (63%) had other malignancies, and 9 of 17 (53%) had nonmalignant diseases. Recurrent tumor in patients with HCC occurred in four cases after surgery (range, 6-15 months) and did not correlate with AFP mRNA positivity before surgery, during surgery, or after surgery.

CONCLUSIONS

Alpha-fetoprotein mRNA in peripheral blood is not a specific marker of circulating micrometastases from HCC, especially in the context of surgical treatment of HCC.

Prediction of outcome for patients with cutaneous melanoma

Most patients with primary melanoma are cured by local surgery, but a significant minority develop fatal metastases. The ability to identify patients with progressive disease is central to efficient management: permitting optimal deployment of adjunctive therapy and sparing the non-progressing majority the morbidity of aggressive therapy. Accurate prediction on an individual patient basis is the ideal, but the best current prognosticators permit only assignment to risk categories. Formulaic combinations of well tried correlates of outcome (gender, ulceration, depth, thickness, and mitotic rate increase accuracy of prediction, but not to personalised level. The use of large data bases against which the attributes of individual patients may be compared is useful and amalgamation of data bases will increase the availability of this approach. The development of markers of proliferation fraction (PCNA and MIB-1) and of the metastatic phenotype (PNA-receptor status) will further refine the process. Staging of disease is critical. Accuracy of staging is improved by mapping the (sentinel) lymph nodes likely to contain early tumor by lymphoscintigraphy and dye/radiomarker localisation. The application of exquisitely sensitive immunohistochemical and molecular biological techniques to biopsies from tissues likely to be the site of metastases permit assessment of clinical stage with a previously impossible degree of accuracy (ultrastaging).

Detection of intact prostate cancer cells in the blood of men with prostate cancer

OBJECTIVES

To develop a procedure to be used to find, identify, and characterize the living prostate cancer cells in the blood of patients with prostate cancer.

METHODS

The procedure is based on a negative selection approach that removes most of the blood cells and collects the remaining prostate cancer cells, which are identified and characterized by fluorescent in situ hybridization with deoxyribonucleic acid probes and by indirect fluorescent immunocytochemical staining. The blood cells are removed via density gradient centrifugation.

RESULTS

Using the prostate cancer LNCaP cells as a model, the recovery rate of the added prostate cancer cells to 10 mL of blood was about 85%, with a dilution of 1 LNCaP cell to 10,000 white blood cells or more. Blood samples varying from 9 to 27 mL were collected and analyzed from 8 men aged 54 to 79 years who had varying levels of PSA in serum. In one blood sample, prostate cancer cells were not found; in the seven other samples, the number of prostate cancer cells found per milliliter of blood varied from 1 to 20. Prostate cancer cells were not found in 7.5 to 15-mL blood samples from 3 healthy younger men. The prostate cells were found to be aneuploid for chromosomes 7 and 8, highly suggestive that these cells were cancerous.

CONCLUSIONS

Using a negative selection approach, prostate cells can be found in the blood of patients with prostate cancer, as identified by prostate cell-specific probes and antibodies. These cells were found to be aneuploid.

Systemic therapy of malignant melanoma

The present status of medical treatment of malignant melanoma is briefly reviewed, both with regard to adjuvant therapy for individuals with high-risk melanoma and a high probability of harbouring subclinical micrometastases, as well as to therapy for established disseminated (macrometastatic) disease. At present, disseminated, macrometastatic melanoma is incurable in the majority of cases. Single agent chemotherapy has modest effects and results in disease remission in a minority of patients, usually of short duration, Combination chemotherapy, or the combination of chemotherapeutic drugs and cytokines, results in increased response rates and occasionally remissions of prolonged duration. So far, no regimen has demonstrated improved survival compared to single agent therapy in disseminated melanoma. New insights into the mechanisms of resistance to chemotherapeutic drugs may lead to development of predictive tests that can identify individuals with tumors sensitive to a specific agent, as well as to the development of strategies to circumvent drug resistance. It has recently been shown that adjuvant therapy of high-risk melanoma with large doses of interferon-alpha 2b significantly prolongs relapse-free and overall survival, at the price of considerable toxicity. Ongoing studies aim to define the optimum dose and duration of adjuvant interferon therapy. Recent advances in molecular biology and immunology may lead to the development of new treatment modalities, such as improved vaccines and other biologic therapies, which may benefit patients with malignant melanoma.

Reverse transcriptase-polymerase chain reaction assays for prostate cancer

RT-PCR, if targeted against a prostate-specific marker, can be a highly specific and sensitive assay to detect the presence of occult prostate cancer cells at sites far distant from the primary tumor. The low false-positive rate (0.8%) observed when combining most published studies and the high rate of detection of prostate cells in metastatic patients (88%) found in well-defined clinical studies address the basic requirements of a clinically effective diagnostic modality. Additionally, all reports indicate that RT-PCR positivity for PSA or PSMA increases with increased stage of prostate cancer, suggesting that RT-PCR assays may have value in staging the patient presumed to have clinically localized disease. Indeed, data from two institutions have shown the unique contribution that RT-PCR technology might lend to this most vexing problem. With the suggestive data already published, we remain optimistic that molecular staging will become a reality in the future. After all, the variability in techniques of RT-PCR (as well as differences in targets and samples assayed) used by the various laboratories now investigating this method could themselves be responsible for many of the differences reported. There is no question that standardization among laboratories is essential before clinical utility of molecular staging can be proved. Indeed, this endeavor represents the major aim of the RT-PCR consortium in the United States. Nevertheless, at our own medical center, we are struck by our finding that if a preoperative RT-PCR for PSA is negative, the patient can be assured of a successful operative outcome in 88% of cases. We also are impressed by the data showing that if the serum PSA level is greater than 10 ng/mL and the RT-PCR assay is positive, 90% of patients undergoing radical surgery have adverse pathology reports (and, in fact, have already experience operative failure in nearly half the cases). There is increasing consensus that RT-PCR assays afford prognostic information that is also unique. Three institutions have similar data comparing operative or preoperative RT-PCR strategies (employing all three potential sample sources) with treatment outcome. This may suggest the validity of RT-PCR as a staging modality or, alternatively, suggest that a truly metastatic phenotype is identified in patients with circulating PSA-synthesizing cells, or in patients harboring PSA-synthesizing cells in node or marrow tissues. In either case, RT-PCR appears already to provide information not available before the use of this technology. In fact, in the only series comparing RT-PCR with other, more established predictors (PSA, Gleason score) in a multivariate analysis, RT-PCR status provided the best prognostic information. Prostate manipulation does, in fact, appear to affect the RT-PCR assay. Although digital rectal examination and cystoscopy do not seem sufficiently invasive to release prostate cells into the circulation, a small number of individuals undergoing transrectal ultrasound biopsy will experience this phenomenon. This observation provides a cautionary note relative to timing of sample collection for RT-PCR assays. Furthermore, a significant fraction of patients undergoing prostate manipulation during radical surgery may experience shedding of prostate cells into the operative field and release of some into the peripheral circulation. This has not been universally observed and, even if true, may not share the significance of spontaneous RT-PCR positivity (before prostatic manipulation). In the one instance, a potentially metastatic phenotype is responsible for RT-PCR positivity, whereas in the other instance, PSA or PSMA synthesizing cells may have no metastatic potential at all. Further studies on the biologic half-life of such cells are required before any clinical judgement can be made regarding this phenomenon. In summary, there appears to be consensus that RT-PCR technology can differentiate controls from patients with metas

Tyrosinase mRNA is expressed in human substantia nigra

Dopamine acts, under appropriate conditions, as a selective neurotoxin. This toxicity is attributed to the autoxidation of the neurotransmitter into a reactive quinone that covalently modifies cellular macromolecules (i.e. proteins and nucleic acids). The oxidation of the catecholamine to a quinone is greatly accelerated by the enzyme tyrosinase. There is controversy, however, as to whether or not tyrosinase is expressed in human brain. In the present study, RT-PCR was utilized to demonstrate the presence of tyrosinase mRNA in post-mortem human brain tissues. Using gene-specific amplification primers, specific tyrosinase amplicons were detected following analysis of RNA from substantia nigra of four individuals. Analysis of cerebellar RNA from the same individuals produced no amplification products. Control reactions performed in the absence of reverse transcriptase failed to generate PCR products for any tissue tested. Three amplicons were subjected to direct DNA sequencing and all proved to be identical with tyrosinase sequences, thus obviating the possibility of amplification of a related gene. It is clear, therefore, that the tyrosinase gene is expressed in the human substantia nigra, lending support to previous studies describing tyrosinase-like activity and immunoreactive protein in the brain. This enzyme could be central to dopamine neurotoxicity as well as contribute to the neurodegeneration associated with Parkinson's disease.

Evaluating neoadjuvant therapy effectiveness on systemic disease: use of a prostatic-specific membrane reverse transcription polymerase chain reaction

OBJECTIVE

An on-going study at the Memorial Sloan-Kettering Cancer Center assessed the effectiveness of androgen deprivation therapy (ADT) prior to surgical removal of the prostate. In this report, we evaluate the effectiveness of ADT on systemic disease by monitoring the presence or absence of circulating prostatic epithelial cells using a reverse transcription polymerase chain reaction (RT-PCR) assay for prostatic-specific membrane antigen (PSM).

METHODS

PSM RT-PCR was performed on a total of 38 prostate cancer patients. There were 12 pT2 patients in the ADT group and 10 patients in the control pT2 group and 5 pT3 patients in the ADT group and 11 pT3 patients in the control group.

RESULTS

For pT2 patients, 2 of the 12 patients (17%) were positive for circulating prostatic cells during androgen deprivation therapy but before radical retroprostatectomy (RRP). Within a 6-month period after RRP, 3 of 12 patients (25%) were positive. For the period between the 7th and 12th month after RRP, 6 of 12 patients (50%) were positive. For the period 12-36 months after RRP, 2 of the 12 patients (17%) remained positive for circulating prostatic cells. In contrast, the pT2 control group had higher positive rates in comparable periods: 4 of 10 patients (40%) were positive prior to surgery; 6 of 10 patients (60%) were positive during the 6 months following surgery. For the period between the 7th and 12th month following surgery, 4 of 7 patients (57%) were positive for PSM. Finally, 3 of 6 patients (50%) were positive for the period longer than 12 months. Regarding patients who have extraprostatic disease (stage pT3), the ADT group had a lower rate of circulating PSM positive cells. Before RRP and during androgen deprivation therapy, 1 out of 5 patients (20%) in the ADT group were positive as compared to 4 out of 11 patients for the control group. Within a 6-month period after RRP, the ADT group had 4 out of 9 (44%) patients positive for PSM as compared to 9 of 11 (82%) for the control group. For the period between the 7th and 12th months postsurgery, 1 of 5 patients (20%) of the ADT group were positive as compared to 4 of 7 (57%) of the control patients.

CONCLUSIONS

These results indicate that patients with pT2 and pT3 lesions who receive neoadjuvant ADT are less likely to have circulating tumor cells detected compared to a control group both prior to and after surgery. In addition, irrespective of ADT or control group, there were increases in the detection of circulating tumor cells in the period after RRP, and this rise gradually decreased, suggesting that surgical manipulation may cause hematogenous dissemination of tumor cells and that ADT reduces such dissemination of tumor cells. Overall, these results indicate that the use of neoadjuvant ADT decreases the number of circulating prostatic cells. These data represent the initial results of an on-going study. As additional patients are added to the studies, attempts to correlate PSM positivity and serum PSA values postoperatively, recurrence, and margin positivity will be made.

Detection of squamous-cell carcinoma antigen-expressing tumour cells in blood by reverse transcriptase-polymerase chain reaction in cancer of the uterine cervix

We used a reverse transcriptase-polymerase chain reaction method for squamous-cell carcinoma (SCC) antigen mRNA to detect circulating tumour cells in patients with carcinoma of the uterine cervix. The sensitivity of the method, as determined by cell spiking experiments, was 10 cultured A431 cells among 10(6) white blood cells. Circulating tumour cells were detected in 6 of 15 patients. In our control group of 24 women, SCC antigen mRNA was detected in 2 pregnant women at term. We followed up the patients for 24 months after sampling and evaluated the outcome. Three out of 6 patients positive for SCC antigen mRNA have relapsed. Additionally, 1 patient has developed breast cancer. In the group of 9 patients negative for SCC antigen mRNA there has been 1 relapse and 1 case of progression of disease. These results suggest that detection of SCC antigen mRNA in peripheral blood by RT-PCR could be useful for staging and evaluation of prognosis in epidermoid carcinoma of the uterine cervix.

Demonstration of cytoplasmic tyrosinase mRNA in tissue-cultured cells by reverse transcription (RT) in situ polymerase chain reaction (PCR) and RT PCR in situ hybridization

To evaluate the specificity and applicability to the study of human tumor cells of the reverse transcription (RT) in situ PCR and RT polymerase chain reaction (PCR) in situ hybridization techniques, we examined five melanoma cell lines and five nonmelanoma lines for tyrosinase mRNA using primers specific for tyrosinase. Each procedural step was optimized and minutely controlled, and results from the in situ techniques and solution-phase RT-PCR were compared. All melanoma lines showed a specific pattern of perinuclear cytoplasmic reaction not seen in nonmelanoma lines. There was exact agreement between the results from the RT in situ PCR and RT-PCR in situ hybridization techniques and those from solution-phase RT-PCR. Ribonuclease digestion abolished cytoplasmic staining, as did omission of the reverse transcriptase step. Nuclear staining was seen in melanoma and nonmelanoma lines, apparently as a result of DNA synthesis from repair-replication and mispriming or nonspecific amplification. Neither high concentrations of deoxyribonuclease nor long incubation periods abolished this effect completely. Demonstration of cytoplasmic mRNA by RT in situ PCR and RT-PCR in situ hybridization specifically identifies cells of melanocytic lineage.

The analysis of tyrosinase-specific mRNA in blood samples of melanoma patients by RT-PCR is not a useful test for metastatic tumor progression

Reverse transcription (RT) of the tyrosinase mRNA and specific cDNA amplification by nested polymerase chain reactin (PCR) have been reported to facilitate the early detection of circulating tumor cells in melanoma patients. The significance and practical value of this procedure for the diagnosis of tumor dissemination in melanoma patients are unclear. In the current study we analyzed peripheral blood samples of 65 melanoma patients of different clinical stages for the presence of tyrosinase mRNA by RT-PCR using nested oligonucleotide primers specific for tyrosinase cDNA. Furthermore, blood samples were evaluated for tumor cell growth by cell culture assays in vitro. No tyrosinase mRNA was detectable in blood samples of 26 patients with primary melanoma and 16 patients with regional lymph node metastases. In five of 13 patients with visceral metastases we found at least one blood sample positive for tyrosinase mRNA during a 2-to 4-mo interval. Analyses of different blood samples of patients with visceral metastases taken in a 2-h interval, furthermore, indicate that tumor cells only transiently persist in the peripheral blood. We obtained in vitro proliferating melanoma cells from two blood samples derived from different patients with visceral melanoma metastases. This demonstrates that viable melanoma cells indeed circulate in the peripheral blood with retained proliferative capacity in vitro. The analysis of blood samples by RT-PCR for tyrosinase mRNA, however, is not suitable for the early detection of tumor progression in melanoma patients.

Molecular detection of circulating solid carcinoma cells in the peripheral blood: the concept of early systemic disease

Detection of the mRNA of selected genes by reverse transcriptase-polymerase chain reaction (RT-PCR) is a sensitive and powerful tool for detecting cancer cells in bone-marrow or peripheral-blood samples. In this study, we determined whether carcinoembryonic antigen (CEA) mRNA is detectable in the peripheral blood of patients with gastrointestinal or breast cancer. In addition, we studied selected patients undergoing surgical procedures to assess whether tumor manipulation during operation enhances cancer-cell dissemination. Peripheral blood from 55 patients with gastrointestinal or breast cancer and from 22 control cases was analysed for CEA mRNA using RT-PCR. For 15 selected cases undergoing curative surgery for cancer, samples were also obtained during and after surgery. The lower limit of detection was 1 to 10 CEA-positive cells diluted among 1 x 10(7) blood mononuclear cells. The test was positive for 20 of the 55 patients with cancer (36%). None of the 22 control samples were positive. An increase in positivity was observed with increasing stage of disease; however, even some patients with early-stage cancer showed positive results. In addition, CEA mRNA could be detected in the peripheral blood during operation in 3 of 13 patients whose pre-operative CEA mRNA in the peripheral blood had been negative. These findings suggest that, (1) RT-PCR amplification of CEA mRNA is an efficient means of detecting circulating solid cancer cells in the peripheral blood, although long-term clinical studies should be done to evaluate its usefulness; (2) not only breast cancer but also gastrointestinal cancer might be better regarded as a systemic disease even in early stages of carcinoma; and (3) surgical manipulation can provoke cancer-cell dissemination.

Detection of colorectal carcinoma cells in circulating peripheral blood by reverse transcription-polymerase chain reaction targeting cytokeratin-20 mRNA

For the detection of circulating colorectal carcinoma cells, we investigated the presence of cytokeratin 20 (CK 20) mRNA in the peripheral blood of colorectal carcinoma patients. Application of our published technique resulted in analysis by reverse transcription followed by three-step nested polymerase chain reaction. This analysis could detect a single Colo 205 colon cancer cell mixed with 1 ml of blood. Our system also successfully detected the presence of CK 20 mRNA in actual patients' peripheral blood samples. Our highly sensitive and specific system for the detection of CK-20 mRNA from patients' peripheral blood thus seems to be useful for screening for circulating colorectal carcinoma cells.

A quantitative reverse transcriptase polymerase chain reaction-based assay to detect carcinoma cells in peripheral blood

The presence of tumour cells in the circulation may predict disease recurrence and metastasis. To improve on existing methods of cytological or immunocytological detection, we have developed a sensitive and quantitative technique for the detection of carcinoma cells in blood, using the reverse transcriptase polymerase chain reaction (RT-PCR) identifying transcripts of the pancarcinoma-associated tumour marker EGP-2 (KSA or 17-1A antigen). The amount of EGP2 mRNA was quantified using an internal recombinant competitor RNA standard with known concentration and which is both reversely transcribed and co-amplified in the same reaction, allowing for a reliable assessment of the initial amount of EGP2 mRNA in the sample. Calibration studies, seeding blood with MCF-7 breast carcinoma cells, showed that the assay can detect ten tumour cells among 1.0 x 10(6) leucocytes. The PCR assay revealed that normal bone marrow expresses low levels of EGP2 mRNA, although immunocytochemistry with the anti-EGP2 MAb MOC31 could not identify any positively stained cell. Analyses using this RT-PCR assay may prove to have applications to the assessment of circulating tumour cells in clinical samples.

Elevated serum levels of S100 and survival in metastatic malignant melanoma

Current reports suggest serum S100 as a prognostic marker for disease progression in advanced malignant melanoma. In this study, we assessed serum levels of S100 and multiple clinical factors in relation to overall survival in 99 patients with metastatic malignant melanoma seen at our institution between May 1990 and April 1996. For statistical analysis, we used both univariate and multivariate Cox proportional-hazards models. Elevated serum levels of S100 correlated with poor outcome in metastatic malignant melanoma (P < 0.0001), univariate analysis). Upon multivariate analysis, however, S100 added no information to known clinical prognostic parameters.

Transcription of the gene encoding melanoma-associated antigen gp100 in tissues and cell lines other than those of the melanocytic lineage

The expression of the gp100 antigen is generally thought to be confined to cells of the melanocytic lineage, which makes the protein a suitable melanoma-specific marker. Strikingly, after screening a panel of normal tissues, tumour samples and cell lines of non-melanocytic origin, we found transcripts encoding gp100 in virtually every tissue and cell line tested. In contrast, tyrosinase and MART-1/MelanA transcripts were detected only in cells of the melanocytic lineage. However, no gp100 protein could be detected by either Western blotting or cytotoxicity assays. Therefore, at the protein level, gp100 remains exclusive for cells of melanocytic origin despite its transcription in many cell types. The major implication of this finding is that screening of patient material for gp100 expression should preferrably be performed by antibody staining. Reverse transcriptase polymerase chain reaction (RT-PCR) can be employed, provided that it is performed in a tightly controlled, semiquantitative setting.

Detection of alphafetoprotein-expressing cells in the blood of patients with hepatoma and hepatitis

The presence of tumour cells in the blood circulation may predict disease recurrence and metastasis. We have evaluated the specificity and sensitivity of detecting hepatoma cells in blood using nested polymerase chain reaction with primers specific for the alphafetoprotein (AFP) gene. The nested polymerase chain reaction amplified a 270-base pair AFP DNA fragment from cDNA of Hep 3B hepatoma cells. In a reconstitution experiment, AFP mRNA was detected from peripheral mononuclear cells isolated from 10 ml of blood containing as few as ten Hep 3B cells. Peripheral mononuclear cells from the blood of 20 hepatoma patients were analysed, and 19 patients showed positive AFP mRNA expression. Seven of 13 samples from hepatitis patients also showed positive AFP mRNA expression. All five paired samples of peripheral blood or umbilical cord blood from pregnant mothers and their babies, respectively, showed positive AFP expression. None of 22 control samples was positive. The presence of AFP mRNA in the blood of hepatitis or hepatoma patients suggests the presence of circulating hepatoma cells or hepatocytes in the circulation. The high incidence of AFP mRNA in the blood of hepatoma patients supports the notion of early haematogenous spreading of the disease.

Recent advances in the care of the patient with malignant melanoma

OBJECTIVE

The authors review the recent advances in the surgical care, staging, and adjuvant treatment of the patient with melanoma.

SUMMARY BACKGROUND DATA

Melanoma care has not changed significantly in the last 20 years, and the controversy of elective lymph node dissections in this disease continues to be discussed. Two advances in the care of the patient with melanoma have occurred in the last 3 years to make this an exciting time for clinicians and to offer more hope for the patients with this disease. The concept of the sentinel lymph node (SLN), defined by Morton as the first node in the lymphatic basin that drains the primary melanoma, has been documented to contain the first site of metastatic disease. This technology can be used to stage nodally the melanoma patient, identifying the subgroup of patients (stage III) who have a 5-year survival rate less than 50%. Members of this group are candidates for effective adjuvant therapies.

METHODS

A review of the surgical techniques of melanoma care, including recently reported new studies of elective node dissection (ELND) and SLN biopsy in patients with melanoma was performed. In addition, the Eastern Cooperative Oncology Group (ECOG) 1684 trial, which was the basis for the Food and Drug Administration approval of adjuvant interferon-alpha-2b (IFN-alpha-2b) is discussed.

RESULTS

The Intergroup Melanoma Trial has reported a survival benefit for performing ELND in patients with melanoma and tumor thickness between 1 and 2 mm or in patients that are younger than 60 years of age. With six reports in the literature that show there is an order to melanoma nodal metastases and that the SLN histology is reflective of the histology of the remainder of the nodal basin, the more conservative SLN biopsy can be performed to adequately stage nodally the patient with melanoma. Patients with nodal metastases who are rendered free of disease with surgical resection have the most to benefit from adjuvant IF-alpha-2b. If one considers only the lymph node-positive group of patients, the survival benefit associate with adjuvant IFN is significant (p = 0.008).

CONCLUSIONS

New standards of care for the melanoma patient have been established. Patients at high risk for recurrence have been shown to experience a survival benefit with adjuvant IFN-alpha-2b. With these data, the argument can be made that all patients with melanoma greater than 1 mm should have a nodal staging procedure. Selective lymphadenectomy with SLN biopsy is the least morbid procedure that can be used to obtain this information. If surgeons do not have the nuclear medicine or pathology support to perform lymphatic mapping, then the guidelines of the Intergroup Melanoma Study should be used to apply ELND in a selective fashion. In this way, patients are identified with micrometastatic disease early in their clinical course and can be offered the survival benefit of adjuvant therapy.

Detection of mutant K-ras DNA in plasma or serum of patients with colorectal cancer

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.

Cutaneous malignant melanomas in 57 cats: identification of (amelanotic) signet-ring and balloon cell types and verification of their origin by immunohistochemistry, electron microscopy, and in situ hybridization

Cutaneous malignant melanomas in cats, both melanotic and amelanotic, were diagnosed in 57 of 1.530 skin tumors during the period 1991-1995. All melanomas occurred in domestic shorthaircats of ages 3-19 years (mean = 11.5 years). Postmortem examination was performed on 16 cats. All had metastases in the regional lymph node and several organ systems. The average time of survival after surgical removal of the tumor was 4.5 months. Histologically, five types of melanomas could be distinguished: epithelioid, spindle, mixed, signet-ring, and balloon cell. Whereas all epithelioid, spindle, and mixed epithelioid/spindle cell types showed pigmentation, signet-ring and balloon cell types were often amelanotic. Immunohistochemical examination of the melanomas revealed a positive staining for S-100, vimentin, and neuron-specific enolase. The melanomas were negative for muscle cell markers, except in some of the signet-ring cell melanomas; 13 of 21 tumors showed a weak positive staining for polyclonal desmin. Electron microscopic examination of signet-ring cell melanomas revealed an abundance of intermediate filaments, whereas in some of these tumors a few cells with melanosomes were found. Nonisotopic in situ hybridization for mRNA encoding for tyrosinase verified the melanocytic origin of the amelanotic signet-ring and balloon cell melanomas.

Molecular detection of circulating solid carcinoma cells in the peripheral blood: the concept of early systemic disease

Detection of the mRNA of selected genes by reverse transcriptase-polymerase chain reaction (RT-PCR) is a sensitive and powerful tool for detecting cancer cells in bone-marrow or peripheral-blood samples. In this study, we determined whether carcinoembryonic antigen (CEA) mRNA is detectable in the peripheral blood of patients with gastrointestinal or breast cancer. In addition, we studied selected patients undergoing surgical procedures to assess whether tumor manipulation during operation enhances cancer-cell dissemination. Peripheral blood from 55 patients with gastrointestinal or breast cancer and from 22 control cases was analysed for CEA mRNA using RT-PCR. For 15 selected cases undergoing curative surgery for cancer, samples were also obtained during and after surgery. The lower limit of detection was 1 to 10 CEA-positive cells diluted among 1 x 10(7) blood mononuclear cells. The test was positive for 20 of the 55 patients with cancer (36%). None of the 22 control samples were positive. An increase in positivity was observed with increasing stage of disease; however, even some patients with early-stage cancer showed positive results. In addition, CEA mRNA could be detected in the peripheral blood during operation in 3 of 13 patients whose pre-operative CEA mRNA in the peripheral blood had been negative. These findings suggest that, (1) RT-PCR amplification of CEA mRNA is an efficient means of detecting circulating solid cancer cells in the peripheral blood, although long-term clinical studies should be done to evaluate its usefulness; (2) not only breast cancer but also gastrointestinal cancer might be better regarded as a systemic disease even in early stages of carcinoma; and (3) surgical manipulation can provoke cancer-cell dissemination.

Reverse transcriptase/polymerase chain reaction detection of cytokeratin-19 mRNA in bone marrow and blood of breast cancer patients

A two-step reverse-transcriptase-based polymerase chain reaction (PCR) with nested primer pairs was developed to amplify sensitive and specific cytokeratin-19 (CK-19) mRNA sequences from human breast cancer cells. No CK-19 pseudogene interference was seen. The larger DNA-derived amplification products could be clearly discriminated from mRNA-derived products. The CK-19 message was not amplified from bone marrow or blood of healthy volunteers and patients with haematological malignancies nor from myeloid and lymphoid cell lines. Breast cancer cells were diluted in buffy coat cells up to 10(-6) and CK-19 mRNA sought by PCR. The CK-19 message was detected in 14 of 26 blood samples and 14 of 24 marrow samples but in neither of two peripheral blood stem cell samples taken from 35 breast cancer patients. By sequence-analysis control of two of these samples and two cell lines, the amplified DNA fragments were confirmed to be homologous with the CK-19 sequence. The CK-19 message was further sought in matched blood/marrow samples taken from 13 untreated women in the same cohort at the time of diagnosis. In 3 of these, CK-19 RNA was detected in blood and marrow and, in 3 others, only in blood, but never in marrow alone. The results show that CK-19 assay by reverse transcriptase/PCR is a sensitive and specific technique for the detection of cancer cells in bone marrow and blood. It could be helpful in diagnosis and monitoring of metastatic breast cancer and detection of micrometastases. This should be evaluated on larger numbers of patients, with different clinical samples and epithelial malignancies.

Identification of carcinoembryonic antigen mRNA in circulating peripheral blood of pancreatic carcinoma and gastric carcinoma patients

To detect adenocarcinoma cells in the circulating peripheral blood, we "analyzed the presence of carcinoembryonic antigen (CEA) mRNA in the peripheral blood obtained from patients with pancreatic carcinoma (PC) or with gastric carcinoma (GC) and also, as controls, from pancreatitis or gastritis patients without carcinomas, a gastric lymphoma patient and four healthy volunteers. Because of the small number of carcinoma cells expected in the peripheral blood, the analysis was performed by the reverse transcription followed by an original two-step polymerase chain reaction. By this sensitive method, 3 of 9 PC patients and 2 of 9 GC patients were positive for CEA mRNA. Except for 1 highly advanced PC patient, 3 of 4 CEA mRNA-positive patients developed recurrence after curative resection or liver metastasis after palliative operation within 9 months after the analysis. None of the control patients was positive for CEA mRNA in the peripheral blood. The results suggest that our sensitive RT-PCR method for detecting CEA mRNA in the peripheral blood is practically useful to find the hematogenous spreading of adenocarcinoma cells.

Identification of carcinoembryonic antigen-producing cells circulating in the blood of patients with colorectal carcinoma by reverse transcriptase polymerase chain reaction

BACKGROUND

Application of the reverse transcriptase polymerase chain reaction (RT-PCR) to identification of circulating tumour cells in colorectal cancer.

AIMS

To assess whether circulating malignant cells in patients with colorectal liver metastasis could be identified by RT-PCR recognition of mRNA coding for the tumour marker carcinoembryonic antigen (CEA).

PATIENTS

A total of 31 with colorectal liver metastases and 22 no-cancer controls.

METHODS

Specific cDNA primers for CEA transcripts were used to apply RT-PCR to tissue biopsy specimens, colon carcinoma cell lines, and peripheral blood samples from patients with colorectal liver metastases. A strongly CEA-expressive HT115 colorectal carcinoma cell line was used to spike blood samples from no-cancer control subjects.

RESULTS

The limit for detection of CEA cDNA by Southern blotting using HT115 cells was 50 cells per 14 ml of spiked blood. There was a significant difference (p = 0.007) in RT-PCR positive expression between patients with liver metastasis (26/31) compared with controls (5/22). There was no significant relation between the prevalence of CEA cDNA amplification and serum CEA level or metastasis volume in patients with liver metastasis.

CONCLUSIONS

This is the first study to suggest that identification of circulating colorectal cancer cells using RT-PCR for detection of CEA cDNA is feasible.

Skip metastasis to the mediastinal lymph nodes in non-small cell lung cancer

BACKGROUND

Whether any difference exists in clinical characteristics between resected non-small cell lung cancer with either skip or ordinary mediastinal lymph node metastases (N2 disease) needs to be clarified.

METHODS

There were 110 patients with stage IIIA N2 disease. Thirty-three patients demonstrating no metastasis at the hilar nodes [skip (+) group] were compared with the other 77 patients [skip (-) group]. To investigate the extent of nodal involvement, we classified the mediastinal lymph nodes into three regions (superior, inferior, or aortic).

RESULTS

There were no significant differences regarding histologic type, T status, or the site of the primary tumors between the skip (+) and the skip (-) N2 groups. In the skip (+) group, mediastinal node metastasis was found in only one region (level 1) in 30 patients (90.9%) and in two regions (level 2) in 3 (9.1%), whereas 28 patients (36.4%) from the skip (-) group revealed mediastinal metastasis at two or three regions (level 2 or 3). The overall survival rate at 5 years after operation was 35% in the skip (+) group and 12.7% in the skip (-) group (p = 0.054). This favorable clinical outcome in the skip (+) group could be explained partially by the higher proportion of patients with level 1 metastases. Furthermore, regarding patients with level 1 disease, the skip (+) group tended to have a better prognosis than the skip (-) group (p = 0.096).

CONCLUSIONS

These results suggest that patients with skip mediastinal lymph node metastases represent a unique subgroup of N2 disease.

Genomic PCR detects tumor cells in peripheral blood from patients with myxoid liposarcoma

Myxoid liposarcoma (MLS) is the most common subtype of liposarcoma. The cytogenetic hallmark of MLS is the pathognomonic t(12;16)(q13;p11), present in more than 85% of cases. The translocation leads to the fusion of the CHOP and FUS genes at 12q13 and 16p11, respectively, and the generation of a FUS/CHOP hybrid protein. The presence of a tumor-specific chimeric gene makes it possible to identify MLS cells by polymerase chain reaction (PCR). We have analyzed peripheral blood samples obtained during a 10-year period at diagnosis of primary and/or recurrent disease in 19 MLS patients with t(12;16) and in one MLS patient with t(12;22;20), resulting in the fusion of the CHOP and EWS genes. Nested PCR on genomic DNA from blood samples amplified FUS/CHOP hybrid fragments in three patients and EWS/CHOP in the patient with t(12;22;20). There was no obvious association between PCR findings and clinical outcome, but larger series are needed to draw any firm conclusions.

High-sensitivity detection of minimal residual breast carcinoma using the polymerase chain reaction and primers for cytokeratin 19

We have developed a reverse transcriptase-polymerase chain reaction (RT-PCR) assay to identify breast carcinoma cells in bone marrow aspirates with high sensitivity and specificity. This assay relies on the detection of cytokeratin 19 (K19) RNA by nested primer PCR followed by annealing to a (32P)-labeled internal sequence probe and autoradiography. In reconstitution experiments, this assay is capable of detecting 10 fg of admixed mammary tumor RNA in 1 microgram of normal marrow RNA (a dilution of 1:10(7)). Thirty of 30 primary breast tumor specimens, 19 of 19 cytologically positive bone marrow aspirate specimens, and three of 11 aspirate negative/biopsy positive specimens showed detectable K19 transcript. This assay shows high specificity, with 50 of 52 negative control aspirates showing no detectable amplification product. False-positive amplification was noted in two of 18 aspirates obtained from patients with active chronic myelogenous leukemia. Of stage II and III postsurgical breast carcinoma patients with histologically negative bone marrows and no radiographic bone disease, 14 of 30 were K19 positive by PCR. RT-PCR analysis of K19 transcript is a highly sensitive and specific method of detecting and monitoring low-level metastatic disease in patients with primary carcinoma of the breast. The presence of K19 RNA in histologically negative bone marrows suggests that this assay may prove a powerful monitor for patients undergoing curative therapy as well as a novel prognostic indicator.