High-speed detection of occult tumor cells in peripheral blood

Although detection of tumor cells in peripheral blood using imitiunocytochemistry and optical scanning is a promising method for screening and monitoring cancer, it poses a major technical challenge due to the extremely low tumor cell concentration in blood. The preferred detection method - digital microscopy - is far too slow for analysis of the large numbers of cells required for statistical validity. We describe here a novel prescan instrument that rapidly identifies a small number of candidates for subsequent examination by digital microscopy to determine if they are genuine tumor cells. The prescan is 500 times faster than digital microscopy and yet has a similar sensitivity. The high prescan speed is accomplished by trading resolution for field of view. The resolution of the prescan is determined by the laser spot size of about 10 microns. While this resolution is much coarser than the submicron resolution of microscopes, it is still sufficient for detecting fluorescent cells because it matches the size of a typical cell. The wide field of view and high scan rate are enabled by a novel application of fiber optics.

Reliability of quantitative reverse-transcriptase-PCR-based detection of tumour cells in the blood between different laboratories using a standardised protocol

Differences in methods of reverse-transcriptase (RT)-polymerase chain reaction (PCR)-based detection of tumour cells in the blood gives rise to conflicting results, and standardisation is urgently needed. This pilot study aimed to assess the variation of RT-PCR-based detection of tumour cells in blood between four different laboratories using a commercially available kit with a standardised protocol. This kit allows comparison of results from different laboratories and facilitates the investigation of the influence of pre-analytical parameters. All laboratories analysed identical sets of blood samples spiked with tumour cells in a concentration range of 1-100 tumour cells/ml. To study at which level variation was introduced, three kinds of sample sets were generated in which (i) tumour cell RNA was spiked in the RNA of mononuclear cells (MNC), (ii) tumour cells were spiked in isolated MNC, and (iii) tumour cells were spiked in blood. Real-time quantitative RT-PCR was used to detect and quantify cytokeratin 20 (CK20) expression, which is indicative for the presence of epithelial tumour cells. All laboratories were able to detect CK20 expression in all spiked-RNA samples with limited variation in expression levels between laboratories. There was a positive correlation between the amount of spiked tumour cell RNA and CK20 expression level. RT-PCR analysis of spiked-MNC samples resulted in more variation in the CK20 expression levels between laboratories, however again all spiked samples were reported to be positive by all of the laboratories. The evaluation of spiked-blood samples gave rise to considerable quantitative and qualitative variation between the laboratories. Our results underline the importance and need for standardisation and extended quality control studies in the field of pre-analytics.

Circulating tumor cell clusters in the peripheral blood of colorectal cancer patients

PURPOSE

Recently several reverse transcription-PCR techniques have been proven to be useful for the detection of circulating micrometastases. However, this way intact cell clusters that were found in animal experiments of prognostic value could not be detected. In this study, evaluation and modification of a commercial, cytokeratin-based, immunomagnetic cell separation method was performed for the detection of intact cell clusters in colorectal carcinoma patients.

EXPERIMENTAL DESIGN

Thirty-two colon cancer patients (6 were in Dukes stage B, 13 in stage C, and 13 in stage D) and 20 healthy donor samples were evaluated. Immunomagnetic cell separation was performed from the buffy coat of peripheral blood samples (20 ml) using the Carcinoma Cell Enrichment Kit (Miltenyi Biotec, Bergisch Gladbach, Germany), avoiding any filtering steps. The enriched cell fraction was cytocentrifuged and immunocytochemically labeled using a pancytokeratin antibody (MNF116; Dako).

RESULTS

Of 20 healthy samples, 2 contained one cytokeratin-positive cell. Of 32 single samples from malignant cases, 24 showed cytokeratin-positive cells. Tumor cell clusters, mixed-cell doublets (one cytokeratin-positive and -negative cell), and mixed-cell clusters were detected in 22 of 24 patients. In six cases, cytokeratin-positive dendritic-like cells were detected. Follow-up data indicate that chemotherapy cannot destroy all of the circulating tumor cell clusters.

CONCLUSIONS

Using the methods presented, we could detect circulating colon cancer cells and cell clusters in colon carcinoma patients. Similar cellular structures were described previously only in rats. Present data prove that such structures are present in human colorectal cancer, too.

Loss of transforming growth factor beta 1 regulatory activity in human non Hodgkin lymphomas

Since TGF beta 1 inhibits the proliferation of normal B-cells, its disturbed activity in B cell lymphomas is conceivable. We found high expression of TGF beta 1 mRNA in three human B cell non-Hodgkin lymphoma xenografts; also, the gene product (in latent form) was detectable in all lymphoma cells. However, on exposing the cells to exogenously activated TGF beta 1, the incorporation of tritiated thymidine decreased in normal (murine thymocytes, human peripheral mononuclear cells), but not in lymphoma cells. These observations suggest the malfunction of TGF beta 1 mediated regulatory pathway (e.g. insufficient activation or receptor expression) which can contribute to the unlimited expansion of a lymphoid clone. The opposite expression of c-myc to TGF beta and the retained sensitivity to anti-IgM indicate that c-myc and Ig receptor can operate independently of TGF beta in the regulation of lymphoid cell proliferation.

Differential expression of proteoglycans on the surface of human melanoma cells characterized by altered experimental metastatic potential

Heparan sulphate (HS) and chondroitin sulphate (CS) proteoglycans (PGs) frequently have opposite biologic functions in cell-matrix adhesion as well as in the regulation of cell proliferation. Data revealed that sulphated glycosaminoglycans (sGAGs) (sugar chains of PGs) are differently expressed in tumor cells characterized by different metastatic potential; the more metastatic cells contain a higher HS/CS ratio. As the proliferative capacity of tumor cells is also frequently altered in parallel with their metastatic potential, it was not clear whether observed PG alterations reflect changes in cell proliferation or metastatic potential. The cell-associated PG expression and sGAG biosynthesis was studied in tumor cells of human melanoma lines characterized by different experimental metastatic potential to the mouse liver but similar in vitro/in vivo proliferation rates. Using antibodies against PGs we found different expression of PG epitopes in melanoma lines, except from the melanoma antigen. Unlike the low CSPG (melCSPG) metastatic melanoma cells, the cell line with high metastatic capacity contained a higher proportion of positive cells for surface-HSPG without the coexpression of certain cartilage-type CSPG epitopes (recognized by MAb HSFPG 529) as well as by an increased pericellular HS/CS ratio due to intracellular accumulation/retention of CS. Immunocytochemistry of adherent cells revealed HSPGs at substrate-attached membrane areas only in cases of highly metastatic melanoma cells. These data further support our view that the absolute or relative dominance of HSPGs over CSPGs at the cell surface of metastatic tumor cells can be considered a marker of a more metastatic phenotype.