Analysis of EpCAM positive cells isolated from sentinel lymph nodes of breast cancer patients identifies subpopulations of cells with distinct transcription profiles.

INTRODUCTION: The presence of tumor cells in the axillary lymph nodes is the most important prognostic factor in early stage breast cancer. However, the optimal method for sentinel lymph node (SLN) examination is still sought and currently many different protocols are employed. To examine two approaches for tumor cell detection we performed, in sequence, immunomagnetic enrichment and RT-PCR analysis on SLN samples from early stage breast cancer patients. This allowed us to compare findings based on the expression of cell surface proteins with those based on detection of intracellular transcripts. METHODS: Enrichment of EpCAM and Mucin 1 expressing cells from fresh SLN samples was achieved using magnetic beads coated with the appropriate antibodies. All resulting cell fractions were analyzed by RT-PCR using four chosen breast epithelial markers (hMAM, AGR2, SBEM, TFF1). Gene expression was further analyzed using RT-PCR arrays and markers for epithelial to mesenchymal transition (EMT). RESULTS: Both EpCAM and Mucin 1 enriched for the epithelial-marker expressing cells. However, EpCAM-IMS identified epithelial cells in 71 SLNs, whereas only 35 samples were positive with RT-PCR targeting breast epithelial transcripts. Further analysis of EpCAM positive but RT-PCR negative cell fractions showed that they had increased expression of MMPs, repressors of E-cadherin, SPARC and vimentin, all transcripts associated with the process of epithelial to mesenchymal transition. CONCLUSIONS: The EpCAM IMS-assay detected tumor cells with epithelial and mesenchymal-like characteristics, thus proving to be a more robust marker than pure epithelial derived biomarkers. This finding has clinical implications, as most methods for SLN analysis today rely on the detection of epithelial transcripts or proteins.

Genome wide single cell analysis of chemotherapy resistant metastatic cells in a case of gastroesophageal adenocarcinoma.

BACKGROUND: Metastatic progression due to development or enrichment of therapy-resistant tumor cells is eventually lethal. Molecular characterization of such chemotherapy resistant tumor cell clones may identify markers responsible for malignant progression and potential targets for new treatment. Here, in a case of stage IV adenocarcinoma of the gastroesophageal junction, we report the successful genome wide analysis using array comparative genomic hybridization (CGH) of DNA from only fourteen tumor cells using a bead-based single cell selection method from a bone metastasis progressing during chemotherapy. CASE PRESENTATION: In a case of metastatic adenocarcinoma of the gastroesophageal junction, the progression of bone metastasis was observed during a chemotherapy regimen of epirubicin, oxaliplatin and capecitabine, whereas lung-, liver and lymph node metastases as well as the primary tumor were regressing. A bone marrow aspirate sampled at the site of progressing metastasis in the right iliac bone was performed, and single cell molecular analysis using array-CGH of Epithelial Specific Antigen (ESA)-positive metastatic cells, and revealed two distinct regions of amplification, 12p12.1 and 17q12-q21.2 amplicons, containing the KRAS (12p) and ERBB2 (HER2/NEU) (17q) oncogenes. Further intrapatient tumor heterogeneity of these highlighted gene copy number changes was analyzed by fluorescence in situ hybridization (FISH) in all available primary and metastatic tumor biopsies, and ErbB2 protein expression was investigated by immunohistochemistry. ERBB2 was heterogeneously amplified by FISH analysis in the primary tumor, as well as liver and bone metastasis, but homogenously amplified in biopsy specimens from a progressing bone metastasis after three initial cycles of chemotherapy, indicating a possible enrichment of erbB2 positive tumor cells in the progressing bone marrow metastasis during chemotherapy. A similar amplification profile was detected for wild-type KRAS, although more heterogeneously expressed in the bone metastasis progressing on chemotherapy. Correspondingly, the erbB2 protein was found heterogeneously expressed by immunohistochemical staining of the primary tumor of the gastroesophageal junction, while negative in liver and bone metastases, but after three initial cycles of palliative chemotherapy with epirubicin, oxaliplatin and capecetabine, the representative bone metastasis stained strongly positive for erbB2. CONCLUSION: Global analysis of genetic aberrations, as illustrated by performing array-CGH analysis on genomic DNA from only a few selected tumor cells of interest sampled from a progressing bone metastasis, can identify relevant therapeutic targets and genetic aberrations involved in malignant progression, thus emphasizing the importance and feasibility of this powerful tool on the road to more personalized cancer therapies in the future.

Mapping of oxidative stress responses of human tumor cells following photodynamic therapy using hexaminolevulinate.

BACKGROUND: Photodynamic therapy (PDT) involves systemic or topical administration of a lesion-localizing photosensitizer or its precursor, followed by irradiation of visible light to cause singlet oxygen-induced damage to the affected tissue. A number of mechanisms seem to be involved in the protective responses to PDT, including activation of transcription factors, heat shock proteins, antioxidant enzymes and apoptotic pathways. RESULTS: In this study, we address the effects of a destructive/lethal hexaminolevulinate (HAL) mediated PDT dose on the transcriptome by using transcriptional exon evidence oligo microarrays. Here, we confirm deviations in the steady state expression levels of previously identified early defence response genes and extend this to include unreported PDT inducible gene groups, most notably the metallothioneins and histones. HAL-PDT mediated stress also altered expression of genes encoded by mitochondrial DNA (mtDNA). Further, we report PDT stress induced alternative splicing. Specifically, the ATF3 alternative isoform (deltaZip2) was up-regulated, while the full-length variant was not changed by the treatment. Results were independently verified by two different technological microarray platforms. Good microarray, RT-PCR and Western immunoblotting correlation for selected genes support these findings. CONCLUSION: Here, we report new insights into how destructive/lethal PDT alters the transcriptome not only at the transcriptional level but also at post-transcriptional level via alternative splicing.

Specific isolation of disseminated cancer cells: a new method permitting sensitive detection of target molecules of diagnostic and therapeutic value.

Molecular studies of rare cells, such as circulating cancer cells, require efficient pre-enrichment steps to obtain a pure population of target cells for further characterization. We have developed a two-step approach, starting with immunomagnetic enrichment, followed by specific isolation of individual, easily identifiable bead-rosetted target cells using a new semi-automated CellPick system. With this procedure, 1-50 live target cells can now be isolated. As a model system, we spiked a small number of tumor cells into millions of normal mononuclear cells (MNCs). Efficient isolation of pure target cells was obtained by use of the CellPick system, and the nature of isolated, bead-rosetted cells was verified by use of FISH. Single breast cancer cells were picked directly into an RNA preserving lysis buffer, reverse transcribed, and PCR amplified with two cDNA specific primer sets. With the isolated cells we consistently obtained both ubiquitously expressed and tumor cell specific PCR products. We also performed a successful mutation analysis of single cells using PCR and cycling temperature capillary electrophoresis (CTCE). This may have significant clinical implications in cancer and in other diseases, e.g. in characterizing micrometastatic cancer cells in blood and lymph nodes to help identifying patients who most likely will respond to therapies like tyrosine kinase inhibitors and compounds targeting specific mutations. By use of the CellPick system it is possible to specifically isolate bead-rosetted or otherwise labelled target cells from a heterogeneous cell population for further molecular characterization.

Melanoma-specific expression in first-generation adenoviral vectors in vitro and in vivo -- use of the human tyrosinase promoter with human enhancers.

Current treatment regimens for patients with metastatic melanoma are not curative, and new treatment strategies are needed. One possible approach is targeted treatment using the tyrosinase promoter for melanoma-specific expression of genes delivered by adenoviral (Ad) vectors. In this study, a vector with the human minimal tyrosinase promoter and two human enhancer elements (2hE-hTyrP) was compared with different hybrid promoter constructs, containing tyrosinase regulatory sequences and the viral simian virus 40 (SV40) promoter. The tissue specificity of the first-generation vectors was measured by enhanced green fluorescence protein (EGFP) reporter flow cytometry in 12 human melanoma and nonmelanoma cell lines. In the melanotic melanoma cells, the activity of the 2hE-hTyrP promoter was comparable with the activity of the cytomegalovirus promoter, and the background expression levels obtained in the nonmelanoma cell lines confirmed the strict tissue-specific property of this promoter. The hybrid SV40-based promoters were effective, but no tissue specificity was observed even after the inclusion of tyrosinase enhancer elements identical to the elements used in the 2hE-hTyrP promoter. The in vivo tissue specificity of the 2hE-hTyrP vector was demonstrated in subcutaneous xenografted tumors by ex vivo detection of EGFP fluorescence with the IVIS Imaging equipment and fluorescence microscopy visualizing the in situ EGFP expression in tumor sections. The tyrosinase mRNA level in the 12 cell lines was measured by quantitative real-time RT-PCR, and the expression levels reliably reflected to what extent the 2hE-hTyrP promoter could drive the gene expression in the individual cell lines. In conclusion, the human tyrosinase promoter fused to two human tyrosinase enhancers (2hE-hTyrP) can be used for efficient tissue-specific expression from first-generation Ad vectors in melanoma cell lines both in vitro and in vivo, as predicted by the quantitative tyrosinase mRNA levels in the melanoma and nonmelanoma cell lines tested.

Interferon-gamma-induced suppression of S100A4 transcription is mediated by the class II transactivator.

We have previously shown that interferon-gamma (IFN-gamma) inhibits expression of the metastasis-promoting protein S100A4. In the present study, we further explore the mechanism behind the IFN-gamma-mediated effects on the human S100A4 promoter and demonstrate that IFN-gamma represses S100A4 promoter activity through induction of the class II transactivator (CIITA). The acidic domain in the N-terminal part of CIITA was crucial for the observed IFN-gamma-induced inhibition of S100A4 promoter activity, probably by binding the histone acetyltransferase CBP/p300. Importantly, overexpression of CIITA significantly reduced the expression of endogenous S100A4. Our data suggest a model where CIITA represses S100A4 transcription through sequestering of CBP/p300, thereby reducing the level of CBP/p300 at the S100A4 promoter, which in turn leads to inhibition of S100A4 transcription.

Photochemical treatment with endosomally localized photosensitizers enhances the number of adenoviruses in the nucleus.

BACKGROUND: In the present study the physical targeting technique photochemical internalization (PCI) has been used in combination with adenovirus. We have previously shown that PCI enhances transgene expression from AdhCMV-lacZ, and the aim of the present study was to further increase the understanding of photochemically mediated adenoviral transduction. METHODS: Two colorectal carcinoma cell lines, WiDr and HCT116, were pre-incubated with the photosensitizer TPPS(2a) or methylene blue derivates (MBD) followed by infection with adenovirus and light exposure. Transgene expression was measured by flow cytometry. Real-time polymerase chain reaction (PCR) and fluorescence in situ hybridization (FISH) were used to quantify the level of viral DNA in the nuclei. Real-time PCR was also used to measure the level of beta-galactosidase mRNA in samples infected with AdhCMV-lacZ. RESULTS: Exposing TPPS(2a)-treated cells to light enhanced the quantity of viral DNA in the nucleus, the mRNA level of the transgene and the transgene expression compared to non-illuminated cells. The increased transgene expression was independent of the promoter used, but dependent on the time of light exposure and the cellular localization of the photosensitizer. CONCLUSIONS: The enhanced transgene expression observed after photochemical treatment is most likely not a result of one event, but more an interplay between various mechanisms. An increased level of adenoviral DNA in the nucleus and a dependency of endosomal localization of the photosensitizer to obtain enhanced transgene expression suggested that endosomal rupture facilitated the transport of adenoviruses to the nucleus.