Detection of minimal residual cells carrying the t(14;18) by DNA sequence amplification

Reverse transcriptase polymerase chain reaction (RT-PCR) detection of melanoma-related transcripts in the peripheral blood and bone marrow of patients with malignant melanoma. What have we learned?

The detection of circulating tumor cells (CTC) and bone marrow micrometastases (BMM) by reverse transcriptase polymerase chain reaction (RT-PCR) may help predict recurrence and survival in malignant melanoma (MM). Since the appearance of the original article by Smith et al. in 1991 (Lancet 338:1227), several groups have attempted the detection of CTC and BMM in MM using RT-PCR for melanocytic specific markers, mainly tyrosinase mRNA. Most studies show that tyrosinase is not present in the PB and BM of control individuals without MM. The PCR positivity rates in MM are extremely variable, ranging from 0% to 100%. There was a correlation between RT-PCR and stage in some but not all of the studies. These disparate findings could in part be explained by differences in RNA extraction and blood separation techniques, to unrecognized contamination leading to false positive results, or differences in patient selection. Despite these discrepancies, we and others have shown that RT-PCR for tyrosinase mRNA in PB is able to predict overall survival (OS) and disease-free survival (DFS) in a statistically significant manner. In AJCC stage II-IV patients rendered surgically free of disease, we found that blood tyrosinase positivity was an independent predictor of OS and DFS. We also found that BM tyrosinase positivity is an independent predictor of DFS in the same group of patients. RT-PCR may help identify subgroups of patients at high risk for early relapse for more aggressive adjuvant therapy. Large prospective studies and interlaboratory quality assurance initiatives are necessary to confirm the accuracy and prognostic value of these RT-PCR assays.

Optimization of the PCR for detection of Staphylococcus aureus nuc gene in bovine milk

Staphylococcus aureus is an economically important and a major mastitis-causing pathogen that also poses food safety and antimicrobial resistance threats. Substances in mastitic milk inhibit the Taq DNA polymerase reaction (Taq PCR) making it of limited use for detecting S. aureus mastitis. In the study reported here, a set of oligonucleotide primers of 21 and 24 bases was used in Taq-PCR to amplify DNA from S. aureus (isolates from bovine mastitis). A specific amplicon of 270 bp was generated as predicted. Replacing Taq DNA polymerase with Thermus thermophilus (Tth) DNA polymerase alone (Tth-PCR) raised the sensitivity of S. aureus detection in milk from experimentally infected cows from 65 to 80%. Combining the use of Tth DNA polymerase and the purification of crude DNA extract using Chelex-100 before PCR raised the sensitivity to 100%. In a random survey involving 100 milk samples from cattle not infected with S. aureus, the test was 100% specific. With milk samples from clinical cases of bovine mastitis, 100% sensitivity and specificity were also observed. It is concluded that Tth-PCR on milk samples with the purification of crude DNA extracts using Chelex-100 is as sensitive as but faster than conventional milk bacteriological culture techniques and is highly specific. The modified PCR correlates with elevated somatic cell counts, detects evidence of chronic and resolving infection based on S. aureus-specific DNA and circumvents the endogenous inhibitory effects of milk.

Characterisation of BCL2-JH rearrangements in follicular lymphoma: PCR detection of 3' BCL2 breakpoints and evidence of a new cluster

Follicular lymphomas (FL) are closely associated with a t(14;18)(q32;q21) translocation, leading to a bcl2 protein over-production. This translocation probably constitutes a very early step in the development of the disease. Besides the cytogenetic assay, t(14;18) detection can be achieved using either Southern blot or polymerase chain reaction (PCR). Since 1990, several publications have reported discrepancies between the results of cytogenetic and molecular analysis of t(14;18). Using methods able to explore long DNA fragments, several authors reported breakpoints located outside the usual breakpoint regions. However, these techniques cannot be easily used in routine. The aim of this study was to develop a simple PCR assay to amplify rearrangements usually not detected in FL. We selected a group of 83 patients with a t(14;18) on cytogenetic analysis: using usual probes and primers, 54/83 (65.1%) showed a MBR rearrangement, 7/83 (8.4%) were mcr positive and 22/83 (26.5%) remained negative. Among these 22 rearrangements, nine could be detected using this new PCR assay. Four breakpoints were located in a 20 bp area suggesting a recurrent breakpoint cluster close to an Alu repetitive sequence. Finally, remaining negative cases (13/83, 15.6%) suggest that other breakpoints are located between the MBR and mcr regions.

Serum BCL2/IGH DNA in follicular lymphoma patients: a minimal residual disease marker

The majority of follicular lymphoma patients carry a t(14,18) juxtaposing the BCL2 oncogene to the immunoglobulin heavy chain joining region (IgH). Molecular analysis for follicular lymphoma-specific DNA translocations may permit evaluation of minimal residual disease (MRD). We identify extracellular BCL2/IGH transgene DNA in the serum of patients with follicular lymphoma, and evaluate its utility as a surrogate marker. DNA was harvested from both the sera and bone marrow of 5 stage IV follicular lymphoma patients prior to and after chemotherapy and following a novel vaccine-based regimen. Serial PCR amplifications were performed using heminested BCL2-specific major breakpoint cluster region (MBR) primers and the immunoglobulin heavy chain consensus primer. Amplification products were detected by agarose gel electrophoresis, and comparison was made to amplification products from the original tumor biopsy. Results show that four of the five lymphoma patients carried extracellular BCL2/IGH transgene DNA in their serum. The remaining patient did not have an amplification product from either the tumor or the serum, suggesting either the absence of a translocation or the presence of a variant translocation not detectable with this primer set. Transgene DNA was detectable in serum even in patients with MRD, comparing favorably with bone marrow results. In at least one patient, the presence of the transgene in serum at the conclusion of therapy preceded relapse. In conclusion, it seems that tumor-specific, extracellular DNA is present in the serum of follicular lymphoma patients, including those with MRD. Because extracellular DNA may be released into the bloodstream by tumor throughout the body it may be less subject to sampling error, and appears to be an ideal surrogate marker.

Molecular detection and characterisation of circulating tumour cells and micrometastases in solid tumours

The detection and molecular characterisation of circulating tumour cells (CTC) and micrometastases may have important prognostic and therapeutic implications. Because their numbers are very small, these tumour cells are not easily detected using conventional methods. In the last decade, numerous groups have attempted to detect occult tumour cells in solid malignancies using the highly sensitive reverse transcriptase polymerase chain reaction (RT-PCR). These assays were in the vast majority directed against tissue-specific markers. PCR was shown to be superior to conventional techniques in detecting occult tumour cells allowing the identification of one malignant cell mixed with 1-10 million normal cells. In some tumours like melanoma and prostatic carcinoma, tissue-specific transcripts were detected with high specificity in the blood of patients with localised and advanced disease. In some reports, PCR was shown to be a strong predictor of poorer outcome. However, due to the many limitations of PCR (e.g false-positives), many groups are developing new approaches for the detection of occult tumour cells. The most attractive technique involves immunomagnetic isolation of CTC and micrometastases prior to downstream analysis. The tumour-rich magnetic fraction can be subjected to RT-PCR, immunocytochemistry and in situ hybridisation. This will lead to better quantification and molecular characterisation of these tumour cells. In conclusion, the molecular detection and characterisation of occult tumour cells offer a great opportunity for better stratifying patients with solid tumours and for developing new prognostic markers and targeted therapies.

Follicular lymphomas--a review of treatment modalities

Follicular lymphoma is the most common low-grade non Hodgkin's lymphoma and represent an homogeneous entity as defined by pathological, molecular and clinical data. This indolent disease is characterised by a slow growth pattern with possible spontaneous regression, is often disseminated but remains incurable with available treatments when disseminated. For localised stages, involved field radiotherapy remains the standard choice but other approaches remain to be investigated. In advanced disease, chemotherapy has been demonstrated to produce high response rates but recent trials with new treatment strategies including interferon and monoclonal antibodies may improve the current situation. In this article, we will review treatment of follicular lymphomas, specially emphasising published phase III trials.

RT-PCR-based detection of occult disseminated tumor cells in peripheral blood and bone marrow of patients with solid tumors. An overview

Despite recent progress in early detection and local curative therapy, patients with primary epithelial cancer quite frequently relapse with incurable metastasis. Early disseminated tumor cells that may be seminal for distant failure and are undetectable by current diagnostic methods have been identified by immunocytochemical techniques in bone marrow of cancer patients using monoclonal antibodies against cytokeratins. Recently, promising new molecular approaches, namely, reverse transcriptase--polymerase chain reaction (RT-PCR) assays, have been suggested as a potential technique for the detection of minimal residual tumor burden by targeting mRNA transcribed from epithelial genes in bone marrow, peripheral blood, or lymph nodes. Several studies using RT-PCR thus far indicate a highly sensitive and specific staging tool, although the prognostic value is still controversial. However, limitations may arise from ectopic expression of marker mRNA in hematopoietic cells and deficient expression in circulating tumor cells. The present review focuses on the relevant literature and demonstrates the range of current applications of RT-PCR-based assays for detecting disseminated tumor cells in peripheral blood and bone marrow of patients with solid tumors. We will both summarize technical evaluations of published molecular approaches and discuss the widely disparate results on PCR findings in clinical studies.

Melanoma. A multidisciplinary approach for the general surgeon

Advances in the understanding of the biology and treatment of melanoma have moved the care of melanoma patients into an increasingly multidisciplinary environment. Surgeons must understand these advances because they will often be responsible for directing the overall care of these patients. Most patients with melanomas more than 1 mm in diameter and no evidence of metastatic disease should be offered SLNB to more accurately stage them and direct decisions about participation in postoperative adjuvant therapy trials. Until the results of the MSLT are known, the effect of SLNB and ELND on outcome remains unknown. SLNs should be analyzed with serial sectioning and immunohistochemistry to avoid missing micro-metastatic disease. Based on the results of the ECOG-1684 trial, the FDA approved IFN-alpha 2b for the adjuvant treatment of melanoma patients with thick primary tumors (> 4 mm) or resected nodal disease. IFN-alpha 2b treatment is expensive and potentially toxic. The data from ECOG-1684 do not support the use of IFN-alpha 2b in patients with node-negative disease. In light of the ECOG-1690 trial results, the role of high-dose IFN-alpha 2b in the management of patients with resected nodal disease is considerably less clear. Any recommendations for treatment with high-dose IFN-alpha 2b should be made only after weighing the costs, side effects, and potential benefits for individual patients. Numerous, less toxic, promising, adjuvant immunotherapeutic strategies have been developed and are being tested in multicenter, prospective, randomized trials. These strategies include GMK, PMCV, and Melacine. If the results of any of these trials show a survival advantage compared with placebo or equivalent survival compared with IFN-alpha 2b, these immunotherapeutic agents will become the adjuvant treatment of choice for patients with resected high-risk melanoma. RT-PCR detection of tyrosinase in SLNs can identify patients with submicroscopic nodal disease who may be at increased risk for recurrence or death from melanoma. An ongoing, prospective, randomized trial will determine whether patients with histologically negative but RT-PCR-positive SLNs will benefit from lymphadenectomy or adjuvant IFN-alpha 2b therapy. RT-PCR can also identify minimal residual disease in peripheral blood and bone marrow from patients with high-risk melanoma, but RT-PCR analysis of peripheral blood and bone marrow is still experimental, and procedural details need to be standardized and prospectively validated in large patient groups before its use can be considered the standard of care.

Variability of polymerase chain reaction detection of the bcl-2-IgH translocation in an international multicentre study

BACKGROUND

The capacity of the polymerase chain reaction (PCR) to detect very low numbers of cells bearing a t(14;18) translocation has led to its application in assessment of the results of treatment for follicular lymphoma, and suggestions that therapy might be guided by molecular studies. To test the reliability of PCR a collaborative study was undertaken to compare results from different laboratories in Europe and North America.

METHODS

Twenty laboratories with records of publication in molecular diagnostics were sent blood from normal donors with varying numbers of t(14;18)-bearing cells added from a cell line with a translocation in the major breakpoint region (MBR) of the bcl-2 gene. Samples contained 1000, 100, 10, 1 or 0 cells per ml of whole blood and were sent blinded in duplicate. PCR methodology varied widely, with the total number of amplification cycles between 30 and 70, and 13 different primers used for the MBR region. Twelve laboratories used nested PCR and eight single round amplification.

RESULTS

The sensitivity of nested and single round PCR was similar at 100 cells/ml but below this the nested method proved significantly more sensitive. The false positive rate was 28%, with 11 samples from 9 laboratories reported as positive when no t(14;18) cells were added. PCR product size and sequence analysis showed that false positives were due to contamination from cell-line DNA rather than background translocations in the donors. There was no significant difference in false positive rates between nested and single round techniques.

CONCLUSION

The polymerase chain reaction to detect bcl-2-IgH rearrangements is presently carried out with widely disparate results. Further effort is required to bring forward a standard PCR protocol which can be re-tested in different laboratories to improve accuracy and reproducibility. The application of quantitative techniques such as real-time PCR may resolve many of the problems presently encountered.

Complete molecular remissions induced by patient-specific vaccination plus granulocyte-monocyte colony-stimulating factor against lymphoma

Lymphomas express a tumor-specific antigen which can be targeted by cancer vaccination. We evaluated the ability of a new idiotype protein vaccine formulation to eradicate residual t(14;18)+ lymphoma cells in 20 patients in a homogeneous, chemotherapy-induced first clinical complete remission. All 11 patients with detectable translocations in their primary tumors had cells from the malignant clone detectable in their blood by PCR both at diagnosis and after chemotherapy, despite being in complete remission. However, 8 of 11 patients converted to lacking cells in their blood from the malignant clone detectable by PCR after vaccination and sustained their molecular remissions. Tumor-specific cytotoxic CD8+ and CD4+ T cells were uniformly found (19 of 20 patients), whereas antibodies were detected, but apparently were not required for molecular remission. Vaccination was thus associated with clearance of residual tumor cells from blood and long-term disease-free survival. The demonstration of molecular remissions, analysis of cytotoxic T lymphocytes against autologous tumor targets, and addition of granulocyte-monocyte colony-stimulating factor to the vaccine formulation provide principles relevant to the design of future clinical trials of other cancer vaccines administered in a minimal residual disease setting.

Recent advances in the molecular pathogenesis of lymphomas

Most human lymphomas remain heterogeneous biologic entities in spite of recent advances in the description of their clinical presentation, cellular morphology, immunophenotype, and genotype. Elucidation of genetic alterations causing malignant transformation may explain pathogenesis, refine differential diagnosis, clarify prognosis, and provide rational basis for new therapy. During the last year the expression of anaplastic lymphoma kinase clarified presentation and provided clues toward the outcome of anaplastic large cell lymphoma; the breakpoints of t(2;5) were mapped; constitutive activation of anaplastic lymphoma kinase by a chromosomal inversion was described; transformation was shown to be independent of nuclear localization of anaplastic lymphoma kinase; and phospholipase C-gamma was identified as a molecular target for the kinase activity of anaplastic lymphoma kinase. Molecular characterization of recurrent chromosome abnormalities has identified new candidate oncogenes: bcl-9, bcl-10, PAX-5, MMSET, and c-maf. Their precise role in malignant transformation, and the frequency of their alteration in lymphoma and myeloma, is not yet defined. The expression of the antiapoptotic protein bcl-2 on aggressive lymphomas was shown to be associated with inferior disease-free survival by several investigators. This may be a target of pharmacologic reduction of bcl-2 levels. Can these advances in molecular pathogenesis improve cure rates for lymphoma? The spectacularly successful molecular modeling of inhibitors for HIV protease suggests that this may be an attainable objective.

Establishment of a near-triploid human B-cell lymphoma cell line with t(14;18) and a p53 gene point mutation

We report a rare large B-cell non-Hodgkin's lymphoma having a characteristic near-triploid cell population with add(17)(p22) and t(14;18)(q32;q21) translocation. We also established and characterized a new cell line (TK cell) derived from the present lymphoma. A codon 180 mutation (GAG --> GAT) in the p53 gene was detected. t(14;18)(q32;q21) was revealed juxtaposition of the bcl-2 and JH genes. Immunoprecipitation analyses of p53 and bcl-2 revealed that abnormality of the p53 protein and aberrant bcl-2 expression, which may protect cells from apoptosis, may be critical to the development of leukaemogenesis exhibiting near-triploid chromosomes.

Correlation of Bcl-2 Rearrangement With Clinical Characteristics and Outcome in Indolent Follicular Lymphoma

The t(14;18) translocation, which involves the bcl-2oncogene, occurs in follicular lymphomas (FL) at two common sites: the major breakpoint region (MBR) and the minor cluster region (mcr). The biological and clinical significance of these breakpoints is unknown. The bcl-2 breakpoint site was determined in 247 previously untreated patients (49% men; median age 52 years) with indolent FL (155 grade I, 83 grade II, and 8 grade III) to correlate it with pretreatment characteristics, response, and outcome. The bcl-2 breakpoint site was determined by a polymerase chain reaction method of peripheral blood (all cases), bone marrows (149 cases), and fresh lymph node biopsy specimens (68 cases). The breakpoint site occurred at MBR in 175 cases (71%) and atmcr in 27 (11%). In 45 cases (18%), no breakpoint was detected (germline). No significant relationship was found between the rearrangements and the expression of BLC-2 and BAXproteins. Patients’ germline for MBR and mcr tended to present more frequently with stage IV disease and higher β2-microglobulin (β2M) levels, whereas mcr-rearranged patients presented more frequently with early stage and normal β2M. The complete response rate of germline patients was significantly lower than that of MBR and mcr patients. An estimated 3-year failure-free survival (FFS) for mcr, MBR, and germline cases was 95%, 76%, and 57%, respectively (P < .001). Thebcl-2 breakpoint site was independent of serum β2M and lactate dehydrogenase in its correlation with FFS. In conclusion, thebcl-2 rearrangement site is an important prognostic factor in indolent FL, useful to identify patients who may require different treatment.

Correlation of Bcl-2 Rearrangement With Clinical Characteristics and Outcome in Indolent Follicular Lymphoma

The t(14;18) translocation, which involves the bcl-2oncogene, occurs in follicular lymphomas (FL) at two common sites: the major breakpoint region (MBR) and the minor cluster region (mcr). The biological and clinical significance of these breakpoints is unknown. The bcl-2 breakpoint site was determined in 247 previously untreated patients (49% men; median age 52 years) with indolent FL (155 grade I, 83 grade II, and 8 grade III) to correlate it with pretreatment characteristics, response, and outcome. The bcl-2 breakpoint site was determined by a polymerase chain reaction method of peripheral blood (all cases), bone marrows (149 cases), and fresh lymph node biopsy specimens (68 cases). The breakpoint site occurred at MBR in 175 cases (71%) and atmcr in 27 (11%). In 45 cases (18%), no breakpoint was detected (germline). No significant relationship was found between the rearrangements and the expression of BLC-2 and BAXproteins. Patients’ germline for MBR and mcr tended to present more frequently with stage IV disease and higher β2-microglobulin (β2M) levels, whereas mcr-rearranged patients presented more frequently with early stage and normal β2M. The complete response rate of germline patients was significantly lower than that of MBR and mcr patients. An estimated 3-year failure-free survival (FFS) for mcr, MBR, and germline cases was 95%, 76%, and 57%, respectively (P < .001). Thebcl-2 breakpoint site was independent of serum β2M and lactate dehydrogenase in its correlation with FFS. In conclusion, thebcl-2 rearrangement site is an important prognostic factor in indolent FL, useful to identify patients who may require different treatment.

Development and validation of a quantitative polymerase chain reaction assay to evaluate minimal residual disease for T-cell acute lymphoblastic leukemia and follicular lymphoma

The presence of occult disease in cancer patients after therapy is one of the major problems faced by oncologists. For example, although 95% of pediatric T-cell acute lymphoblastic leukemia (T-ALL) patients have a complete therapeutic response to multiagent chemotherapy, half will relapse, indicating that they must have harbored low levels of residual cancer cells at the end of therapy. Sensitive detection assays promise to help identify those patients that carry this minimal residual disease (MRD) and are at risk of relapse. We have developed and validated a quantitative polymerase chain reaction (PCR) assay targeting tumor-specific chromosomal rearrangements, including del(1) involving the tal-1 locus in pediatric T-ALL and t(14;18) involving the bcl-2 locus in follicular lymphoma. This quantitative PCR assay utilizes a synthetic internal calibration standard (ICS) that contains priming sequences identical to those found flanking the chromosomal rearrangement breakpoints. Using this ICS-PCR method, the limits of detection were 5 tumor cells at ratios of 1 tumor cell in 10(5) normal cells and a linear range up to 100% tumor cells. This ICS-PCR method has also performed well in terms of precision and accuracy as indicated by low coefficients of variation, minimal random, proportional, and constant errors, and good clinical sensitivity and specificity characteristics. This technique will allow for the evaluation of parameters such as the rate of therapeutic response and the levels of MRD as predictors of patient outcome.

Rapid simultaneous amplification and detection of the MBR/JH chromosomal translocation by fluorescence melting curve analysis

Polymerase chain reaction (PCR) amplification and product analysis for the detection of chromosomal translocations, such as the t(14;18), has traditionally been a two-step process. PCR product detection has generally entailed gel electrophoresis and/or hybridization or sequencing for confirmation of assay specificity. Using a microvolume fluorimeter integrated with a thermal cycler and a PCR-compatible double-stranded DNA (dsDNA) binding fluorescent dye (SYBR Green I), we investigated the feasibility of simultaneous thermal amplification and detection of MBR/JH translocation products by fluorescence melting curve analysis. We analyzed DNA from 30 cases of lymphoproliferative disorders comprising 19 cases of previously documented MBR/JH-positive follicle center lymphoma and 11 reactive lymphadenopathies. The samples were coded and analyzed blindly for the presence of MBR/JH translocations by fluorescence melting curve analysis. We also performed dilutional assays using the MBR/JH-positive cell line SUDHL-6. Multiplex PCR for MBR/JH and beta-globin was used to simultaneously assess sample adequacy. All (100%) of the 19 cases previously determined to be MBR/JH positive by conventional PCR analysis showed a characteristic sharp decrease in fluorescence at approximately 90 degrees C by melting curve analysis after amplification. Fluorescence melting peaks obtained by plotting the negative derivative of fluorescence over temperature (-dF/dT) versus temperature (T) showed melting temperatures (Tm) at 88.85+/-1.15 degrees C. In addition, multiplex assays using both MBR/JH and beta-globin primers yielded easily distinguishable fluorescence melting peaks at approximately 90 degrees C and 81.2 degrees C, respectively. Dilutional assays revealed that fluorescence melting curve analysis was more sensitive than conventional PCR and agarose gel electrophoresis with ultraviolet transillumination by as much as 100-fold. Simultaneous amplification and fluorescence melting curve analysis is a simple, reliable, and sensitive method for the detection of MBR/JH translocations. The feasibility of specific PCR product detection without electrophoresis or utilization of expensive fluorescently labeled probes makes this method attractive for routine molecular diagnostics.

Detection of t(14;18) carrying cells in bone marrow and peripheral blood from patients affected by non-lymphoid diseases

AIMS/BACKGROUND

To assess the presence of bcl-2/JH rearrangements in bone marrow and peripheral blood lymphocytes from patients affected by diseases other than malignant lymphomas. The t(14;18) (q32;q21) translocation, which juxtaposes the bcl-2 oncogene on chromosome 18 and the JH segment of the immunoglobulin heavy chain (IgH) genes on chromosome 14, is found frequently in follicular lymphomas.

METHODS

A sensitive semi-nested polymerase chain reaction (PCR) was used to detect t(14;18) translocation in bone marrow aspirates and peripheral blood lymphocytes from 48 patients. In 137 additional individuals peripheral blood lymphocytes only were tested.

RESULTS

Cells carrying bcl-2/JH rearrangements were detected in about a quarter of the bone marrow samples and half of the peripheral blood lymphocyte samples. In seven patients, t(14;18) positive cells were found in both the bone marrow and peripheral blood lymphocyte samples. The size of the PCR products and bcl-2/JH DNA sequence analysis showed that the same t(14;18) carrying clone was present in the bone marrow and the corresponding peripheral blood lymphocyte samples in three of these seven patients. Some patients had more than one bcl-2/JH rearrangement. There was no significant correlation between age and the translocation incidence. Cells carrying the t(14;18) translocation were present in peripheral blood lymphocyte samples with a similar incidence--between 47% and 52% in all age groups from 20 to 79 years. Patients older than 80 years had a lower (37%) but not significantly different incidence.

CONCLUSIONS

These findings suggest that patients affected by non-lymphoid diseases may have several t(14;18) carrying cells and some of them undergo a clonal expansion. Whether individuals with t(14;18) positive cells are at a higher risk of lymphoid malignancies remains unanswered and further epidemiological studies are required.

Lymphoma cells associated with bone marrow stromal cells in culture exhibit altered growth and survival

The detection of clonal populations of lymphoma cells in histologically negative bone marrow using culture techniques is a predictor of poor outcome for patients undergoing high dose therapy and autologous transplantation. In positive cultures, lymphoma cells were observed as outgrowths in association with adherent stromal cells, whilst only stromal cells were observed in negative long-term cultures. This study developed an experimental model to further study the interactions occurring between lymphoma cells and stromal cells. Using random dot graticule analysis, 86% and 74%, respectively, of patient lymphoma cells grew in association with stromal cells in leukapheresis and bone marrow harvest cultures with the formation of cobblestone areas at sites of interaction between lymphoma cells and stromal cells. Secondary cultures showed that individual stromal cells were able to support the growth of a small number of lymphoma cells. Coculture of the human lymphoma cell lines with a murine bone marrow stromal cell line, MS-5 also resulted in the formation of cobblestone areas, which corresponded with the suppression of nonadherent cell production by the lymphoma cell lines. Upon interacting with MS-5 cells, the lymphoma cell lines formed pseudopodia and underwent pleiomorphic nuclear changes. Contiguous linear homotypic associations between lymphoma cells were evident, as opposed to focal contacts occurring in the heterotypic interactions between lymphoma cells and MS-5 cells. An increasing proportion of supernatant lymphoma cells underwent apoptosis as time in culture increased. These results demonstrate that bone marrow stromal cells alter the pattern of growth of lymphoma cells and may have an important role in the maintenance of occult lymphoma by inhibiting apoptosis.

Novel 5' exonuclease-based real-time PCR assay for the detection of t(14;18)(q32;q21) in patients with follicular lymphoma

The exonuclease-based real-time polymerase chain reaction (PCR) exploits 5'-->3' exonuclease activity of Taq polymerase and measures PCR product accumulation as the reaction proceeds through a dual-labeled fluorogenic probe. The utility of this exonuclease-based PCR assay as a rapid alternative to conventional PCR for follicular lymphoma-associated t(14;18)(q32;q21) was evaluated in this study. The specificity of the assay for t(14;18) involving bcl-2 and immunoglobulin heavy-chain joining region (JH) genes was assessed by analyzing DNA from 53 patients (38 B-cell non-Hodgkin's lymphomas and 15 nonneoplastic proliferations) and correlating the exonuclease PCR data with conventional PCR results. bcl-2/JH fusion sequences were detected by exonuclease-based PCR in 24 of 25 cases shown to be bcl-2 rearranged by conventional PCR. Fusion sequences were not detected in patients who were negative by conventional PCR. The overall concordance between the two assays was 98% (52 of 53 cases concordant positive or negative). In a serial dilution study using t(14;18)-positive cell line DNA, exonuclease-based PCR detected fusion sequences at DNA concentrations of 5 pg, equivalent to 0.6 to 0.8 genomes per reaction. Thus, this study demonstrated that exonuclease-based PCR for t(14;18) is both specific and highly sensitive. The elimination of the post-PCR amplicon detection steps and the ability to quantitate the input target DNA sequences make this assay ideal for routine diagnostics and monitoring minimal residual disease.

Characterization of t(2;5) Reciprocal Transcripts and Genomic Breakpoints in CD30+ Cutaneous Lymphoproliferations

NPM-ALK chimeric transcripts, encoded by the t(2;5), lead to an aberrant expression of ALK by CD30+ systemic lymphomas. To determine if t(2;5) is involved in cutaneous lymphoproliferative disorders, we studied 37 CD30+ cutaneous lymphoproliferations, 27 mycosis fungoides (MF), and 16 benign inflammatory disorders (BID). NPM-ALK transcripts were detected by nested reverse transcription-polymerase chain reaction (RT-PCR) in 1 of 11 lymphomatoid papulosis (LyP), 7 of 15 CD30+ primary cutaneous T-cell lymphoma (CTCL), 3 of 11 CD30+ secondary cutaneous lymphoma, 6 of 27 MF, and 1 of 16 BID. However, the expression of NPM-ALK transcripts was not associated with ALK1 immunoreactivity in MF, LyP, or BID cases. Only 1 CD30+ primary CTCL and 3 CD30+ secondary cutaneous lymphoma were ALK1 immunoreactive. The ALK1+cases were also characterized by amplification of tumor-specific genomic breakpoints on derivative chromosome 5. These cases, except for 1 secondary cutaneous lymphoma, were also characterized by reciprocal breakpoints on derivative chromosome 2, leading to the expression of reciprocal ALK-NPM transcripts. Amplification of chromosomal breakpoints on both derivative chromosomes could represent an alternative to conventional cytogenetics for the diagnosis of t(2;5) and seems to be more reliable than the detection of cryptic NPM-ALK transcripts by nested RT-PCR.

Characterization of t(2;5) Reciprocal Transcripts and Genomic Breakpoints in CD30+ Cutaneous Lymphoproliferations

NPM-ALK chimeric transcripts, encoded by the t(2;5), lead to an aberrant expression of ALK by CD30+ systemic lymphomas. To determine if t(2;5) is involved in cutaneous lymphoproliferative disorders, we studied 37 CD30+ cutaneous lymphoproliferations, 27 mycosis fungoides (MF), and 16 benign inflammatory disorders (BID). NPM-ALK transcripts were detected by nested reverse transcription-polymerase chain reaction (RT-PCR) in 1 of 11 lymphomatoid papulosis (LyP), 7 of 15 CD30+ primary cutaneous T-cell lymphoma (CTCL), 3 of 11 CD30+ secondary cutaneous lymphoma, 6 of 27 MF, and 1 of 16 BID. However, the expression of NPM-ALK transcripts was not associated with ALK1 immunoreactivity in MF, LyP, or BID cases. Only 1 CD30+ primary CTCL and 3 CD30+ secondary cutaneous lymphoma were ALK1 immunoreactive. The ALK1+cases were also characterized by amplification of tumor-specific genomic breakpoints on derivative chromosome 5. These cases, except for 1 secondary cutaneous lymphoma, were also characterized by reciprocal breakpoints on derivative chromosome 2, leading to the expression of reciprocal ALK-NPM transcripts. Amplification of chromosomal breakpoints on both derivative chromosomes could represent an alternative to conventional cytogenetics for the diagnosis of t(2;5) and seems to be more reliable than the detection of cryptic NPM-ALK transcripts by nested RT-PCR.

Polymerase chain reaction diagnosis of t(14;18) from paraffin-embedded tissues fixed with Holland Bouin fluid

The t(14;18) translocation and its molecular counterpart, the bcl-2/IgH gene rearrangement, are highly characteristic of follicular non-Hodgkin lymphomas. The identification of the tumor-specific t(14;18) clone is mandatory for any molecular studies on residual disease because of the existence of circulating t(14;18)-bearing benign cells. In this study, the ability to specifically polymerase chain reaction (PCR) amplify t(14;18) with DNA purified from tissues fixed with Holland Bouin fluid is demonstrated. The specificity of the PCR product was confirmed by internal probe hybridization and with comparison of the nucleotidic sequences of this PCR product with those obtained from the corresponding frozen material. Although the sensitivity of the technique is 50% to 60%, paraffin-embedded tissues fixed with bouin fluid may be a good alternative to frozen tissues to detect t(14;18) in tumors.

Utilization of polymerase chain reaction technology in the detection of solid tumors

BACKGROUND

Most cancer detection tests currently performed are based on either antibody assays to a marker protein with altered expression in cancer patients or on imaging studies to identify characteristic lesions. Generally, for a positive result, these detection assays require that a tumor have a significant volume of cancer cells. Advances in diagnostic techniques and technology may allow for cancer detection at earlier stages, when the tumor burden is smaller and potentially more curable. The molecular techniques of polymerase chain reaction (PCR) and reverse transcriptase PCR (RT-PCR) are highly sensitive methods for detecting a small number of cancer cells. Over the past few years, numerous clinical studies have used PCR techniques to detect physical alterations of genes, such as mutations, deletions, translocations and amplification, the presence of oncogenic viruses, and the expression of genes specific to tissue, cancer, and metastasis. The current status of PCR as a method for detecting marker genes in the management of solid tumors is reviewed.

METHODS

A review of the literature on the clinical utility of PCR and RT-PCR in the detection of solid tumor micrometastasis was conducted.

RESULTS

Amplification by PCR is a highly sensitive method to determine gene expression. A single cell expressing a tumor marker among 10-100 million lymphocytes can be detected by the PCR assay. This approach has been used to detect tumor cells in approximately 18 different solid tumor types, with melanoma and carcinoma of the breast and prostate the most widely investigated to date. PCR-based assays have been used to detect cancer cells in biopsies of solid tissue, lymph nodes, bone marrow, peripheral blood, and other body fluids. Several studies have reported a high specificity and sensitivity of tumor marker detection and a high correlation between PCR results and the presence of metastatic disease. However, in a few studies, PCR assays have not consistently demonstrated a higher sensitivity and specificity of detection than traditional modalities for many types of cancer. There has been a wide range in sensitivity and specificity among the studies, which may be partly attributed to the lack of uniformity among the PCR protocols used in different studies.

CONCLUSIONS

PCR can detect tumor marker-expressing cells that are otherwise undetectable by other means in patients with localized or metastatic cancer. Reports from various study groups have lacked uniformity in their protocols, and this has prevented adequate comparison. The clinical utility of this assay as a tool for the prognosis and management of cancer patients remains and area of active investigation. PCR is a powerful tool in the study of the biology of cancer metastasis and will likely serve as a useful adjunct to clinical decision-making in the future.

The Clinical Significance of Molecular Response in Indolent Follicular Lymphomas

Most patients with follicular lymphoma (FL) achieve a complete response (CR) after treatment, but eventually most of them, particularly those with stage IV, relapse due to minimal residual disease (MRD). The t(14;18) gives rise to a rearrangement of the bcl-2 oncogene that constitutes an excellent target for detection of MRD by polymerase chain reaction (PCR). One hundred ninety-four previously untreated patients with indolent FL and detectable bcl-2 rearrangement were studied. The PCR assay was used to detect bcl-2–rearranged cells in blood and marrow before and after treatment. Molecular response rate was 37%, 53%, 56%, and 66% at 3 to 5, 6 to 8, 9 to 14, and 15 to 18 months from the start of therapy, respectively. Although molecular response was higher among clinical CRs, one third of partial responders at 3 to 5 months also achieved a molecular response. Patients who achieved a molecular response during the first year of treatment had a significantly longer failure-free survival (FFS) than those who did not (4-year FFS: 76% v 38%, respectively; P &lt; .001). Similar results were also observed in the subset of patients in clinical CR 1 year after treatment. By multivariate analysis, β2-microglobulin (β2-M; P &lt; .01), and molecular response (P &lt; .001) were the most important variables associated with outcome. When we combined β2-M and molecular response, three prognostic groups emerged: (1) low β2-M and molecular responders, (2) low β2-M and nonresponders or high β2-M and responders, and (3) high β2-M and nonresponders. The 4-year FFS of these 3 groups were 86%, 65%, and 23%, respectively. Finally, patients who achieved molecular response and sustained it had better FFS than those who either reverted back to PCR-positive or who never achieved molecular response. Serial PCR analysis to determine the molecular response in FL correlates well with outcome especially when combined with pretreatment β2-M.

Single-Cell Analysis of the t(14;18)(q32;q21) Chromosomal Translocation in Hodgkin's Disease Demonstrates the Absence of This Translocation in Neoplastic Hodgkin and Reed-Sternberg Cells

Using the polymerase chain reaction (PCR) technique and total DNA extracts of Hodgkin's disease (HD)-involved lymph nodes, the t(14;18)(q32;q21) translocation was detected in 37 of 115 (32.2%) cases studied. No correlation was found between the presence of this translocation and bcl-2 protein expression in Hodgkin and Reed-Sternberg (HRS) cells detected by immunohistochemistry in 58 of 96 (60.4%) cases. To identify the cells carrying the t(14;18) translocation, single-cell DNA from HRS cells isolated by micromanipulation from frozen tissue sections of lymph nodes was investigated by PCR amplification. Eleven cases showing a positive band of the same size in at least two of five PCR experiments performed on the same total DNA extract were selected for single-cell PCR. We postulated that this repeated successful amplification could be indicative of the presence of the t(14;18) translocation in the neoplastic HRS cells. Single cells from frozen tumor sections of the t(14;18)-positive OCI LY8 cell line grafted into nude mice served as a positive control. The bcl-2/JH rearrangement, involved in this translocation, could be amplified from single-cell DNA of the latter tumor, whereas, in all of the HD cases, HRS cells were found to be negative. We conclude that the t(14;18) translocation is not localized in HRS cells, but in nonmalignant B bystander lymphocytes, admixed with these neoplastic cells.

Utilization of polymerase chain reaction technology in the detection of solid tumors

BACKGROUND

Most cancer detection tests currently performed are based on either antibody assays to a marker protein with altered expression in cancer patients or on imaging studies to identify characteristic lesions. Generally, for a positive result, these detection assays require that a tumor have a significant volume of cancer cells. Advances in diagnostic techniques and technology may allow for cancer detection at earlier stages, when the tumor burden is smaller and potentially more curable. The molecular techniques of polymerase chain reaction (PCR) and reverse transcriptase PCR (RT-PCR) are highly sensitive methods for detecting a small number of cancer cells. Over the past few years, numerous clinical studies have used PCR techniques to detect physical alterations of genes, such as mutations, deletions, translocations and amplification, the presence of oncogenic viruses, and the expression of genes specific to tissue, cancer, and metastasis. The current status of PCR as a method for detecting marker genes in the management of solid tumors is reviewed.

METHODS

A review of the literature on the clinical utility of PCR and RT-PCR in the detection of solid tumor micrometastasis was conducted.

RESULTS

Amplification by PCR is a highly sensitive method to determine gene expression. A single cell expressing a tumor marker among 10-100 million lymphocytes can be detected by the PCR assay. This approach has been used to detect tumor cells in approximately 18 different solid tumor types, with melanoma and carcinoma of the breast and prostate the most widely investigated to date. PCR-based assays have been used to detect cancer cells in biopsies of solid tissue, lymph nodes, bone marrow, peripheral blood, and other body fluids. Several studies have reported a high specificity and sensitivity of tumor marker detection and a high correlation between PCR results and the presence of metastatic disease. However, in a few studies, PCR assays have not consistently demonstrated a higher sensitivity and specificity of detection than traditional modalities for many types of cancer. There has been a wide range in sensitivity and specificity among the studies, which may be partly attributed to the lack of uniformity among the PCR protocols used in different studies.

CONCLUSIONS

PCR can detect tumor marker-expressing cells that are otherwise undetectable by other means in patients with localized or metastatic cancer. Reports from various study groups have lacked uniformity in their protocols, and this has prevented adequate comparison. The clinical utility of this assay as a tool for the prognosis and management of cancer patients remains and area of active investigation. PCR is a powerful tool in the study of the biology of cancer metastasis and will likely serve as a useful adjunct to clinical decision-making in the future.

Molecular and pathologic characterization of an AIDS-related body cavity-based lymphoma, including ultrastructural demonstration of human herpesvirus-8: a case report

Body cavity-based lymphoma, also known as primary effusion lymphoma, is a newly recognized acquired immunodeficiency syndrome (AIDS)-related lymphoma that has been linked to the Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8). To date, direct visualization of the virus in a clinical sample has not been demonstrated. We have performed an extensive clinical, histologic, immunophenotypic, ultrastructural, and molecular genetic correlative study on multiple tissue samples obtained premortem and at autopsy from an patient with AIDS with Kaposi's sarcoma and body cavity-based lymphomas. We demonstrate the presence of human herpesvirus-8 in a primary clinical sample at the ultrastructural and molecular level, as well as document multiple lymphomatous tumor masses at autopsy.

CD19 selection improves the sensitivity of B cell lymphoma detection

Reinfusion of residual tumor cells into B cell non-Hodgkin's lymphoma (B-NHL) patients during autologous transplantation may be an important cause of disease relapse. Determining the extent to which B-NHL cells are present in autologous progenitor cell products and if the presence of residual B-NHL cells is predictive of relapse will require extremely sensitive methods of detecting rare B-NHL cells. We attempted to improve the sensitivity of polymerase chain reaction (PCR)-based detection of rare B-NHL cells by preselecting CD19+ cells using an immunomagnetic column. To measure detection sensitivity, we prepared samples containing different levels of B-NHL cell contamination by mixing B-NHL cell lines containing the chromosomal translocation t(14;18) bcl-2/JH) with control leukapheresis samples. DNA extracted from each CD19-selected sample and from each matched nonselected sample was added to a PCR to amplify the bcl-2/JH breakdown junction. CD19 preselection improved the sensitivity of detection of t(14;18)-positive B-NHL cells 115-fold, so that B-NHL cells at a concentration of 1 tumor cell per 1 x 10(6) hematopoietic cells were detected in every specimen evaluated. t(14;18)-positive cells were not detected in any of 13 control leukapheresis specimens. We conclude that a combination of CD19 preselection and PCR amplification may improve the sensitivity of detection of rare lymphoma cells by two orders of magnitude without a significant decrease in specificity.

Refinement of the BCL2/immunoglobulin heavy chain fusion gene in t(14;18)(q32;q21) by polymerase chain reaction amplification for long targets

The t(14;18)(q32;q21) translocation, involving the BCL2 gene and junctional segments (JH) of the immunoglobulin heavy chain gene (IGH), constitutes the most common chromosomal translocation in non-Hodgkin's lymphoma of B-cell type. Although the breakpoints in BCL2 are largely clustered within the major breakpoint region (MBR) and minor cluster region (mcr), it is known that some breakpoints map away from these regions, resulting in negative amplification of the junctional sequence by polymerase chain reaction (PCR) for < 1 kb targets. To circumvent this problem, we applied a novel PCR technology for long DNA targets, long-distance (LD-) PCR, to the detection of t(14;18) in clinical materials. Oligonucleotide primers were designed to be quite distant from the two known cluster regions in BCL2, and those for the corresponding IGH were complementary to the enhancer and constant regions. In all 52 cases identified as carrying BCL2/JH fusion by conventional Southern blot analysis, LD-PCR successfully amplified fragments encompassing the junctions, which were readily identifiable on ethidium bromide-stained gel. The size of the LD-PCR products ranged from 3.9 kb to 10.7 kb in MBR/IGH fusion and 1.9 kb to 16 kb in mcr/IGH fusion. Furthermore, we established an LD-PCR protocol for > 20 kb targets, which covered the intervening region between the MBR and mcr. Restriction analysis of the LD-PCR products revealed that breakpoints in 33 cases fell within the 150 bp-MBR region, and in 3 cases were within the mcr determined previously by others. In contrast, the breakpoints of the remaining 16 cases were distributed over a large region from the MBR through mcr. Nucleotide sequence analysis of a potential cluster region revealed the presence of an Alu repeat sequence. Restriction analysis of LD-PCR products with BstEII demonstrated a predominant usage of the JH6 segment (71%) at the BCL2/JH junctions. LD-PCR using primers for the constant region genes showed that class switch recombination occurred in more than 80% of the IGH genes on the der(14) chromosome. Our study showed that LD-PCR was capable of detecting virtually any t(14;18) that occurred within the approximately 30 kb region downstream of the MBR, and thus is suitable for initial diagnosis of lymphoma tissues. Furthermore, as amplified fragments obtained by the LD-PCR contained distinctive regions of BCL2 and IGH, restriction analysis and nucleotide sequencing of the products refined the characteristics of t(14;18).

Molecular pathways in low grade B-cell lymphoma

Low grade B-cell non-Hodgkin's lymphomas (B-NHL) represent a markedly heterogeneous group of lymphoproliferative disorders, including B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma (B-CCL/SLL), lymphoplasmacytoid lymphoma (LPL), follicular lymphoma (FL), mucosa-associated lymphoid tissue lymphoma (MALTL), and splenic lymphoma with villous lymphocytes (SLVL). The molecular pathogenesis of low grade B-NHL is characterized by distinct genetic pathways which selectively associate with each clinicopathologic category. At diagnosis, B-CLL/SLL frequently display deletions of 13q14 and trisomy 12, whereas evolution to Richter's syndrome associates with disruption of p53. LPL carries t(9;14)(p13;q32) in 40-50% of the cases, leading to the deregulated expression of the PAX-5 gene. FL consistently harbors rearrangements of BCL-2 independent of the cytologic variant. With time, a fraction of FL cases accumulates mutations of p53 and evolves into a high grade B-NHL. Low grade MALTL are characterized by the frequent occurrence of trisomy 3 and, occasionally, by p53 mutations. SLVL carries p53 mutations in a fraction of cases. The identification of distinct genetic categories among low grade B-NHL may help in the therapeutic stratification of these disorders. In addition, genetic lesions of low grade B-NHL have proved to be a useful molecular marker for monitoring minimal residual disease.

Detection of BCL-2 gene rearrangement in follicular lymphoma by polymerase chain reaction and chemiluminescence technique

The incidence of follicular lymphoma in Saudi Arabia is very low compared to that in Western countries. We analyzed 22 diagnosed cases, based on conventional morphology examination and immunohistochemistry, to detect the Bcl-2 gene rearrangement by polymerase chain reaction (PCR). The DNA was extracted from formalin-fixed paraffin-embedded lymph node tissues by the standard xylene treatment and proteinase K digestion method. Rearrangement of the major breakpoint region was evident in 8 of the 22 cases (36%), determined by visualization of a discrete band hybridized with a chemiluminescence-labeled specific probe. Although the number of cases is small, we believe it denotes a normal detection rate for PCR analysis, using DNA isolated from fixed tissue. With the exception of follicular lymphoma, non-Hodgkin's lymphoma (NHL) analyzed included diffuse large cell lymphoma, lymphoblastic lymphoma, chronic lymphocytic leukemia, mucosa-associated lymphoid tissue and mantle zone lymphomas. No Bcl-2 gene rearrangement was detected in any of these cases. No evidence of Bcl-2 minor cluster sequence gene rearrangement was detected in any of the 38 NHL cases analyzed.

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

The application of fluorescence-based PCR and PCR-SSCP to monitor the clonal relationship of cells bearing the t(14;18)(q32;q21) in sequential biopsy specimens from patients with follicle center cell lymphoma

This study evaluates the utility of fluorescence-based polymerase chain reaction (PCR) and PCR-SSCP methodologies to monitor the clonal relatedness of cells with bcl-2 major break point region (mbr)/JR fusion sequences in sequential samples from patients with follicular lymphoma (FL). Fluorescence-tagged PCR products from 2-4 sequential samples from seven FL patients were resolved in acrylamide gels and analyzed on an Applied Biosystems' automated DNA sequencer equipped with Genescan software. The amplicons were sequenced directly using automated DNA sequencing to obtain the precise amplicon size and base sequence. Fluorescence-based PCR-single-strand conformation polymorphism (SSCP) analysis performed to distinguish amplicons of similar size but of different base sequence. Amplification products differing by as few as 5 bp resolved clearly under fluorescent PCR assay conditions making possible by visual inspection alone the distinction of two products that otherwise appeared to be of similar size by conventional gel electrophoretic methods. The size of the amplicons as determined by Genescan software correlated exactly with the sizes generated by sequence analysis confirming the precision and accuracy of the fluorescent PCR assay. Under nondenaturing conditions, the mobility profiles of the amplicons from sequential samples with identical base sequence remained indistinguishable, whereas amplicons of similar size but of dissimilar base sequence from different patients exhibited distinct migration patterns. Thus, this study demonstrates that a combination of fluorescent PCR and PCR-SSCP assays for the detection of the t(14;18) provides an accurate measure of clonal relationship based on molecular size and sequence similarities without involving radiolabeling and sequencing strategies. Furthermore, the demonstrated preservation of junctional sequences across sequential biopsy specimens validates the use of PCR in the monitoring of minimal residual disease and eliminates concern about the detection of secondary, non-tumor-related translocations.

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.

Molecular Monitoring of Minimal Residual Disease in Follicular and Mantle Cell Non-Hodgkin's Lymphomas Treated With High-Dose Chemotherapy and Peripheral Blood Progenitor Cell Autografting

Minimal residual disease (MRD) was evaluated in 30 patients with follicular or mantle cell non-Hodgkin's lymphoma (NHL) undergoing an intensive treatment with high-dose sequential (HDS) chemotherapy and peripheral blood progenitor cell (PBPC) autografting. To minimize the potential tumor cell contamination, PBPC harvests were scheduled at the end of HDS pretransplant phase. All patients had advanced-stage disease and most of them presented with bone marrow (BM) involvement. A tumor marker could be generated in 90% of patients using bcl-2 or Ig heavy-chain genes. MRD was analyzed on PBPC, BM harvests, and after autografting by polymerase chain reaction (PCR). All evaluable follicular and 6 of 9 mantle cell patients achieved clinical complete remission. PCR negativity of PBPC and/or BM harvests was documented in 68% of follicular and 12% of mantle cell lymphomas. Molecular remission of PBPC and/or BM harvests was achieved in 9 of 15 patients with overt marrow involvement and in all patients with only molecular marrow infiltration at onset. Molecular follow-up was conducted on 14 patients: all 7 evaluable patients who received at least one PCR-negative graft maintained the negative status at a median follow-up of 24 months and none of them relapsed so far. Thus, the results show that (1) a molecular marker to monitor MRD can be obtained in most follicular and mantle cell NHL patients, (2) the HDS regimen may provide PCR-negative PBPC and/or BM harvests even from patients with BM disease, and (3) autograft with at least one PCR-negative harvest is associated with a durable clinical and molecular remission.

Is there any place for a wait-and-see policy in stage I0 follicular lymphoma? A study of 43 consecutive patients in a single center

BACKGROUND

A wait-and-see policy (WS) does not appear to modify the long-term prognosis of advanced-stage follicular lymphomas (FL), while irradiation of limited stages sometimes causes complications and does not avert distant relapses. Consequently, we decided to test WS in a selected subset of the localized FL, i.e., patients in complete remission (CR) after the initial lymph node biopsy (stage I0).

PATIENTS AND METHODS

Forty-three previously untreated patients were diagnosed with stage I0 FL and 26 of them were included in the WS. Their median age was 60.3 years; 19 were male and 24 female. All histological slides were reviewed and confirmed the diagnosis of FL. Median follow-up was 6.3 years (y).

RESULTS

Thirteen of the 26 untreated patients are still relapse-free, while six relapsed locally only (median: 4.2 years after diagnosis), and reattained CR with radiotherapy. Seven patients relapsed at distant sites (median: 1 year after diagnosis). No localized relapses were observed in the treated group, but there were 7 distant relapses.

CONCLUSIONS

The use of WS in stage I0 FL did not appear to modify the prognosis of these patients. Furthermore, we observed two distinct patterns of relapse (local and distant) that are difficult to differentiate at onset.

The dual expression of minor and major bcr/abl chimeric mRNA in blast crisis of chronic myelogenous leukemia

The hypothesis that minor bcr/abl fusion mRNA is produced in blast crisis of chronic myelogenous leukemia (CML) is examined. The RNA transcripts encoding the minor and major bcr/abl fused protein were detected by polymerase chain reaction (PCR) using RNA from peripheral blood or bone marrow cells of eight patients with blast crisis or accelerated phase of CML. The mRNA encoding for major bcr/abl was detected in all eight cases. In four patients, however, transcripts encoding for minor bcr/abl mRNA were detected, as well as major bcr/abl mRNA. The presence of minor bcr/abl mRNA was verified with the hybridization with a junction-specific probe and DNA sequencing analysis of PCR products. The appearance of minor bcr/abl fusion mRNA was associated with the lymphoblastic immunophenotype of the blast cells. In two of these four patients, samples of initial diagnosis of chronic phase of CML were available, which did not show minor bcr/abl transcript. We conclude that the appearance of minor bcr/abl mRNA transcript is associated with the terminal evolution of CML in lymphoblastic crisis.

Polymerase chain reaction in the detection of micrometastases and circulating tumor cells

BACKGROUND

The sensitive detection of circulating tumor cells and micrometastases may have important therapeutic and prognostic implications.

METHODS

The molecular detection of occult tumor cells can be accomplished by amplifying tumor specific abnormalities present in the DNA or mRNA of malignant cells with the polymerase chain reaction (PCR). This approach has been used mainly for hemato-lymphoid malignancies. The other main PCR strategy for the detection of minimal residual disease (MRD) involves amplification of tissue-specific mRNA. This method was applied for the detection of occult disease in solid tumors.

RESULTS

PCR was shown to be superior to conventional techniques in detecting circulating tumor cells and micrometastases allowing the identification of 1 tumor cell diluted with 10(6)-10(7) normal cells. The central question of whether PCR positivity reliably predicts relapse remains unanswered for many tumor types. Serial analysis of a large number of samples is needed and currently undertaken in many institutions.

CONCLUSIONS

PCR is a highly sensitive method for the detection of circulating tumor cells and micrometastases in solid and hematopoietic malignancies. If PCR positivity is found to be a reliable tool, this will likely have a major impact on the treatment of many cancers. Patients could be selected for systemic therapy at an earlier stage when the metastatic tumor burden is low. PCR may improve the preoperative staging of patients with epithelial malignancies and therefore help avoid unnecessary radical procedures. Furthermore, this test may be useful in monitoring the effectiveness of adjuvant therapy, the intensity and duration of which is tailored to the individual patient. The impact of this PCR based approach on clinical oncology is likely to be profound.

Modification of prolactin receptor (PRL-R) expression by PRL in the mouse liver: estimation of the ratio of two forms of PRL-R mRNAs by "one-sided competitive PCR"

We developed new means of measuring the ratio of the short to the long form (S/L ratio) of the mouse prolactin receptor (mPRL-R) cDNA by PCR using a primer common to the two forms and two specific primers. A means of estimating the amount of mPRL-R cDNA by competitive PCR was also established. We confirmed that these procedures were valid, since the S/L ratio of standard DNA was unaltered by one-sided cPCR amplification under the following conditions: the ratio was between 0.1 and 4, and the amount of cDNA was between 10(3) and 10(7) molecules/tube. The result of one-sided cPCR showed that the short form was dominant in the mouse liver, while the long form was dominant in other tissues. In addition, pituitary grafting increased the S/L ratio in the liver, implying that prolactin down-regulated the functional long form of PRL-R and lowered tissue sensitivity to prolactin itself by modifying the post-transcriptional regulation of PRL-R.

Detection of minimal residual disease in multiple myeloma and acute leukaemia

The importance of minimal residual disease detection has increased due to the advanced therapeutic protocols available for multiple myeloma and acute leukaemia. High-dose chemotherapy, followed by stem cell transplantation is often used in patients with multiple myeloma. But despite a longer disease-free period and overall survival, all patients relapse. In the treatment of acute leukaemia, there are similar problems. The present strategy is to give continuous chemotherapy to eradicate minimal residual disease. In this review, we consider the methods used to detect and quantify minimal residual disease. At present, the most effective seem to be those based on the use of polymerase chain reactions to detect the malignant cells.

Minimal residual disease post-bone marrow transplantation for hemato-oncological diseases

The detection of minimal residual disease (MRD), which is important in cancer treatment, gained special significance in bone marrow transplantation (BMT-) due to the possibility not just to detect but recently also to prevent, treat and reinduce remission in patients that relapsed post-BMT by immunotherapy. The various modern techniques of MRD detection are described including cytogenetics, analysis of restriction fragment length polymorphism, variable number of tandem repeats by Southern Blot or polymerase chain reaction (PCR), microsatellite sequences, PCR amplification products of the Y chromosome or the Amelogenin gene, quantitative PCR and fluorescence in situ hybridization. The role of MRD detection in refinement of indications for BMT, autografting, prediction of relapse, adoptive immunotherapy, mixed chimerism in nonmalignant diseases and in solid organ transplantation is discussed.