PubMed · 3043546
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J B Vogler, W A Murphy. 1988. Bone marrow imaging.. https://doi.org/10.1148/radiology.168.3.3043546
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BACKGROUND: Therapeutic decisions in cancer are generally guided by molecular biomarkers or, for some newer therapeutics, primary tumor genotype. However, because biomarkers or genotypes may change as new metastases emerge, circulating tumor cells (CTCs) from blood are being investigated for a role in guiding real-time drug selection during disease progression, expecting that CTCs will comprehensively represent the full spectrum of genomic changes in metastases. However, information is limited regarding mutational heterogeneity among CTCs and metastases in breast cancer as discerned by single cell analysis. The presence of disseminated tumor cells (DTCs) in bone marrow also carry prognostic significance in breast cancer, but with variability between CTC and DTC detection. Here we analyze a series of single tumor cells, CTCs, and DTCs for PIK3CA mutations and report CTC and corresponding metastatic genotypes. METHODS: We used the MagSweeper, an immunomagnetic separation device, to capture live single tumor cells from breast cancer patients' primary and metastatic tissues, blood, and bone marrow. Single cells were screened for mutations in exons 9 and 20 of the PIK3CA gene. Captured DTCs grown in cell culture were also sequenced for PIK3CA mutations. RESULTS: Among 242 individual tumor cells isolated from 17 patients and tested for mutations, 48 mutated tumor cells were identified in three patients. Single cell analyses revealed mutational heterogeneity among CTCs and tumor cells in tissues. In a patient followed serially, there was mutational discordance between CTCs, DTCs, and metastases, and among CTCs isolated at different time points. DTCs from this patient propagated in vitro contained a PIK3CA mutation, which was maintained despite morphological changes during 21 days of cell culture. CONCLUSIONS: Single cell analysis of CTCs can demonstrate genotypic heterogeneity, changes over time, and discordance from DTCs and distant metastases. We present a cautionary case showing that CTCs from any single blood draw do not always reflect metastatic genotype, and that CTC and DTC analyses may provide independent clinical information. Isolated DTCs remain viable and can be propagated in culture while maintaining their original mutational status, potentially serving as a future resource for investigating new drug therapies.
BACKGROUND: Polymerase chain reaction (PCR) assays that detect fusion genes resulting from consistent chromosomal translocations have been used to detect minimal residual disease, primarily in hematologic malignancies. Molecular assays have been developed recently that detect the PAX3-FKHR or PAX7-FKHR fusion transcript resulting from the t(2; 13) or t(1; 13) translocation consistently observed in alveolar rhabdomyosarcoma. Because of the tumor's propensity to disseminate widely, our aim was to determine whether or not reverse transcriptase-PCR assays could detect submicroscopic disease in bone marrow or peripheral blood specimens. METHODS: We analyzed 19 bone marrow samples from 11 patients with a known gene fusion in their primary tumor. Specimens were collected at diagnosis, remission, and relapse. Fourteen peripheral blood samples were obtained serially from 5 of these patients. A reverse transcriptase-PCR assay was used to detect the presence of the PAX3-FKHR or PAX7-FKHR fusion transcript. These results were compared with the results of microscopic examination of the bone marrow. Medical records of all 11 patients were reviewed. RESULTS: Adequate amplifiable RNA was obtained in 17 of 19 marrow samples. The PCR assay detected fusion products in all 4 specimens obtained from 3 patients with histologic evidence of bone marrow involvement. In addition, PAX3-FKHR fusion products were detected in bone marrows from 2 patients for whom there was no histologic evidence of disease. The fusion transcripts were not detected in any of the peripheral blood samples. CONCLUSIONS: The detection of submicroscopic disease is possible in alveolar rhabdomyosarcoma patients using PCR. These assays may have a role in staging, monitoring therapy, purging protocols for autologous bone marrow transplantation, and post therapy follow-up. Larger prospective studies are needed to address the clinical relevance of these results.
Thirty-one patients (27 with acute myeloid leukemia [AML], 2 with acute lymphocytic leukemia [ALL], and 2 with acute mixed lineage leukemia [AMLL]) treated with conventional chemotherapy (CHT) and 23 patients (13 AML, 5 ALL, and 5 with chronic myeloid leukemia [CML]) treated with allogeneic bone marrow transplantation (BMT) were monitored for WT1 expression levels in BM and peripheral blood (PB) by reverse transcriptase-polymerase chain reaction over a long-term period (mean, 29 months for CHT and 24 months for BMT). Sixteen of the patients in the CHT group and 3 in the BMT group who had achieved complete remission suffered clinical relapse. In 10 of these patients, WT1 expression that had returned to normal BM levels (< 10(-3); the WT1 expression level of K562 cells was defined as 1.0) after complete remission (CR) either gradually or rapidly increased again to abnormal levels 1 to 18 months (mean, 7 months) before clinical relapse became apparent. In another 9 patients, WT1 expression never returned to normal BM levels even after CR and the subsequent relapse was accompanied by a rapid increase in WT1 expression to levels higher than 10(-2) (10(-3) levels in PB). On the other hand, the remaining 35 patients (15 CHT and 20 BMT) maintained their CR. In 29 of these patients (11 CHT and 18 BMT), WT1 expression either gradually or rapidly decreased to normal BM levels, whereas in the other 6 (4 CHT and 2 BMT), low or very low levels of WT1 mRNAs (10(-3) to 10(-2) in BM and 10(-5) to 10(-3) in PB) remain detectable, but without any clinical signs of relapse. A clear correlation was found to exist between the minimal residual disease (MRD) detected in the paired BM and PB samples for all types of leukemias (AML, ALL, and CML), with MRD in PB being approximately one-tenth of that in BM. WT1 quantitation of 168 paired BM and PB samples showed that PB samples were superior to BM samples for the detection of MRD. We conclude that monitoring of WT1 expression levels in BM and PB makes it possible to rapidly assess the effectiveness of individual treatment and diagnose clinical relapse in the early stage for all leukemia patients regardless of the presence or absence of tumor-specific DNA markers.