Flow cytometry was originally established as an automated method for measuring optical or fluorescence characteristics of cells or particles in suspension. In the meantime, flow cytometers have become user-friendlier, less expensive instruments with an increasing importance in clinical diagnostics. Besides the classical fields of application, such as immunophenotyping blood cells or analyzing the cell cycle status by measuring the DNA content, novel flow cytometric methods have been developed to identify and to quantify disease-related gene sequences. Here we give an overview of current and future applications, including the detection of viral sequences via microsphere-based PCR assays and the analysis of single nucleotide polymorphisms, reflecting individual phenotypic traits. Furthermore, flow cytometry allows the quantification of gene expression changes as well as the isolation of differentially expressed gene sequences. Flow cytometry is also convenient for multiplex analyses, e.g. when hybridizing DNA samples to a mixture of various microsphere populations each coated with different DNA probes. Last but not least, the use of magnetic beads in combination with flow cytometers coupled with automated devices enables molecular diagnostics on a large scale. Overall, this review demonstrates flow cytometry as a rapid, sensitive, and reproducible tool applicable to a wide range of medical genetic approaches.

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Sclerosing basal cell carcinoma (S-BCC) is characterized by an abundant stroma. There is evidence that some tumor cells secrete cytokines that are mitogenic for stromal fibroblasts (FBs). From this study we report increased glycosaminoglycan (GAG) production by cultures of S-BCC FBs in comparison to cultures of nodular BCC (N-BCC) FBs and normal skin FBs. GAG production was measured by cetylpyridinium chloride precipitation of incorporated [3H]-glucosamine. The sclerosing BCC FBs demonstrated a significant increase in production of GAG over control FBs (P <.001) and over N-BCC FBs (P<.001). Values reported as a mean percentage +/- SEM for GAG production by S-BCC over control normal skin FBs are 359+/-28 and over N-BCC FBs are 266+/-27. In additional experiments, cell extract dilutions from S-BCC tumor, normal dermis, and normal epidermis were incubated with cultures of normal skin FBs. S-BCC-conditioned media was also incubated with normal FBs and GAG production was measured. For both S-BCC extracts and conditioned media, a dose response curve was established showing increased GAG production by normal FBs in relation to increasing the concentration of S-BCC extract or conditioned media. When S-BCC extract was added to normal FBs there was increased GAG production in comparison to normal FBs incubated with dermal or epidermal extracts (P<.001) for both. Two growth factors, transforming growth factor-beta (TGF-beta) and platelet-derived growth factor (PDGF), already known to be mitogenic for FBs, were incubated with N-BCC and normal FBs in an effort to elucidate the potential cytokine(s) released by S-BCC, causing increased GAG production by surrounding FBs. Neither of these cytokines proved to be effective in promoting a significant increase in GAG production. Our findings support the hypothesis that BCCs release factors that alter stromal FB production of GAG.

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