A comprehensively characterized large panel of head and neck cancer patient-derived xenografts identifies the mTOR inhibitor everolimus as potential new treatment option.

Patient-derived xenograft (PDX) models have shown to reflect original patient tumors better than any other preclinical model. We embarked in a study establishing a large panel of head and neck squamous cell carcinomas PDX for biomarker analysis and evaluation of established and novel compounds. Out of 115 transplanted specimens 52 models were established of which 29 were characterized for response to docetaxel, cetuximab, methotrexate, carboplatin, 5-fluorouracil and everolimus. Further, tumors were subjected to sequencing analysis and gene expression profiling of selected mTOR pathway members. Most frequent response was observed for docetaxel and cetuximab. Responses to carboplatin, 5-fluorouracil and methotrexate were moderate. Everolimus revealed activity in the majority of PDX. Mutational profiling and gene expression analysis did not reveal a predictive biomarker for everolimus even though by trend RPS6KB1 mRNA expression was associated with response. In conclusion we demonstrate a comprehensively characterized panel of head and neck cancer PDX models, which represent a valuable and renewable tissue resource for evaluation of novel compounds and associated biomarkers.

Gastrin transactivates the chromogranin A gene through MEK-1/ERK- and PKC-dependent phosphorylation of Sp1 and CREB.

Our previous work revealed that gastrin regulates chromogranin A (CgA) transcription through enhanced binding of Sp1, CREB and Egr-1 to a proximal gastrin-responsive promoter element (Gas-RE). Here, we provide a detailed characterization of the signalling pathways transmitting the effect of gastrin on the CgA promoter. Gastrin treatment of gastric AGS-B cells potently stimulated MEK-1 as well as MAP kinases ERK-1/-2, JNK and p38 in a time-dependent manner. Interruption of ERK-1/-2/MEK-1 pathways abolished the transactivating effect of gastrin, whereas blockade of JNK or p38 activity was without effect. Functional promoter analysis revealed that the minimal element CgA-85/-64 was sufficient and necessary to confer MEK-1/ERK responsiveness. Analysis of proximal signalling pathways showed that activation of the MEK-1/ERK-1/2 module by gastrin does not require Ras, PI3-kinase or intracellular calcium signals, but depends on activation of kinases of the PKC family. This report demonstrates that a pathway comprising PKCs>Raf-1>MEK-1>ERK-1/-2 mediates the effect of gastrin on the CgA promoter, and strongly suggests that enhanced phosphorylation of Sp1 and CREB is crucial for CgA transactivation through the G protein-coupled CCK-B/gastrin receptor.

Overexpression of pRB in human pancreatic carcinoma cells: function in chemotherapy-induced apoptosis.

BACKGROUND: Human pancreatic adenocarcinomas are highly resistant to chemotherapy. The p16 tumor-suppressor protein is inactivated in more than 90% of human pancreatic cancers. The p16 protein transcriptionally inhibits expression of retinoblastoma tumor-suppressor gene pRB. The pRB protein transcriptionally inhibits expression of the p16 gene. Because pRB normally prevents apoptosis, we investigated whether pRB is involved in resistance to chemotherapy-induced apoptosis in pancreatic cancer cells. METHODS: pRB expression was examined by immunohistochemistry in 106 human pancreatic tissue specimens. The human pancreatic tumor cell line Capan-1 (pRB+/p16-) was stably transfected with p16 to functionally inactivate pRB. pRB gene expression was examined by western and northern blot analyses, and pRB function was assessed by electrophoretic mobility shift assays and promoter transactivation studies for the transcription factor E2F. Changes in cell sensitivity to chemotherapy were measured by assays for cytotoxicity and apoptosis. RESULTS: pRB was overexpressed in pancreatic ductal adenocarcinomas but was hardly detectable in other pancreatic malignancies, chronic pancreatitis, or nontransformed human pancreatic tissue. Expression of p16 in Capan-1 cells resulted in the loss of pRB gene and protein expression concomitant with increased activity of the transcription factor E2F, which was not detected in wild-type or control-transfected Capan-1 cells. Wild-type and control-transfected Capan-1 cells were resistant to chemotherapy-induced apoptosis, but pRB-depleted (i.e., p16-transfected) Capan-1 cells were highly sensitive. The effect was specific to pRB depletion because two other human pancreatic cancer cell lines that retained high pRB expression after p16 transfection were resistant to chemotherapy-induced apoptosis. CONCLUSIONS: Overexpression of pRB is associated with human pancreatic duct-cell cancer and may allow pancreatic cancer cells to evade chemotherapy-induced apoptosis.

Transient receptor potential channel TRPM8 agonists stimulate calcium influx and neurotensin secretion in neuroendocrine tumor cells.

TRPM8 is a member of the melastatin-type transient receptor potential ion channel family. Activation by cold or by agonists (menthol, icilin) induces a transient rise in intracellular free calcium concentration ([Ca(2+)](i)). Our previous study demonstrated that Ca(2+)-permeable cation channels play a role in IGF-1-induced secretion of chromogranin A in human neuroendocrine tumor (NET) cell line BON [Mergler et al.: Neuroendocrinology 2006;82:87-102]. Here, we extend our earlier study by investigating the expression of TRPM8 and characterizing its impact on [Ca(2+)](i) and the secretion of neurotensin (NT). We identified TRPM8 expression in NET BON cells by RT-PCR, Western blotting and immunofluorescence staining. Icilin increased [Ca(2+)](i) in TRPM8-transfected human embryonic kidney cells (HEK293) but not in mock-transfected cells. Icilin and menthol induced Ca(2+) transients in BON cells as well as in primary NET cell cultures of two different pancreatic NETs as detected by single cell fluorescence imaging. Icilin increased non-selective cation channel currents in BON cells as detected by patch-clamp recordings. This activation was associated with increased NT secretion. Taken together, this study demonstrates for the first time the expression TRPM8 in NET cells and its role in regulating [Ca(2+)](i) and NT secretion. The regulation of NT secretion in NETs by TRPM8 may have a potential clinical implication in diagnosis or therapy.

Evaluation of gas-filled microparticles and sonoporation as gene delivery system: feasibility study in rodent tumor models.

PURPOSE: To evaluate the feasibility of gene delivery mediated with diagnostic ultrasound and plasmid DNA (pDNA) encapsulated in gas-filled microparticles (GFMP) in rodent tumor models. MATERIALS AND METHODS: This study was performed according to a protocol approved by the regional animal research committee. The model plasmid UT651 (pUT651) that contained the Escherichia coli LacZ gene for beta-galactosidase was used to demonstrate the feasibility of ultrasound-mediated gene delivery in CC531 liver tumors in rats. In preliminary experiments, a single injection of pUT651-containing GFMP was administered intraarterially (n=4) or intravenously (n=6) with simultaneous sonication (color Doppler mode, maximum mechanical index) of the GFMP passing through the capillaries of the tumors. All animals were sacrificed 2-5 days later, and liver tumors were examined for beta-galactosidase expression histochemically. Subsequently, potential medical usefulness of this delivery system was tested in nude mice bearing Capan-1 tumors (adenocarcinoma of the human pancreas) by using the plasmid RC/CMV-p16 (pRC/CMV-p16), which contains tumor suppressor gene p16. The tumor suppressor gene p16 is deleted in Capan-1 cells. Twenty-five tumor-bearing mice were classified into five groups (four to six mice per group, one treatment group, four control groups) at random. All mice were treated once weekly for 5 weeks with intravenous infusion of p16-containing GFMP or control substances with simultaneous tumor sonication with color Doppler mode ultrasound and maximum mechanical index or without ultrasound treatment. The therapeutic effect of p16 was measured as an increase in tumor volume doubling time. Data were analyzed with analysis of variance. Results were considered significant at the 5% critical level (P < .05). RESULTS: A clear expression of pDNA was found in tumors in rats treated with a combination of pUT651-containing GFMP and ultrasound; relevant controls showed a significantly lower expression of marker gene. The controlled ultrasound-triggered release of pRC/CMV-p16 from GFMP leads to a strong tumor growth inhibition, which is significant (P < .002), compared with that in controls. CONCLUSION: A combination of GFMP and ultrasound provides an effective approach for nonviral gene therapy-based cancer treatment.