Insulin immuno-neutralization decreases food intake in chickens without altering hypothalamic transcripts involved in food intake and metabolism

In mammals, insulin regulates blood glucose levels and plays a key regulatory role in appetite via the hypothalamus. In contrast, chickens are characterized by atypical glucose homeostasis, with relatively high blood glucose levels, reduced glucose sensitivity of pancreatic beta cells, and large resistance to exogenous insulin. The aim of the present study was to investigate in chickens the effects of 5 h fasting and 5 h insulin immuno-neutralization on hypothalamic mRNA levels of 23 genes associated with food intake, energy balance, and glucose metabolism. We observed that insulin immune-neutralization by administration of anti-porcine insulin guinea pig serum (AI) significantly decreased food intake and increased plasma glucose levels in chickens, while 5 h fasting produced a limited and non-significant reduction in plasma glucose. In addition, 5 h fasting increased levels of NPY, TAS1R1, DIO2, LEPR, GLUT1, GLUT3, GLUT8, and GCK mRNA. In contrast, AI had no impact on the levels of any selected mRNA. Therefore, our results demonstrate that in chickens, food intake inhibition or satiety mechanisms induced by insulin immuno-neutralization do not rely on hypothalamic abundance of the 23 transcripts analyzed. The hypothalamic transcripts that were increased in the fasted group are likely components of a mechanism of adaptation to fasting in chickens.

Stem cells and colon cancer: the questionable cancer stem cell hypothesis

The fine-tuning between cell proliferation and differentiation of self-renewing stem cells and pluripotent progenitors in gastric glands and colon epithelial crypts is coordinated by the mechanisms that regulate colon epithelial cell migration and guidance along the crypt axis. This leads to the acquisition of specialized cellular functions and the exfoliation of desquamated senescent and apoptotic epithelial cells at the apical mucosa interface with the gut lumen. Self-renewing stem cells and pluripotent progenitors are involved in the clonal and polyclonal growth of digestive tumors. Several lines of evidence support the existence of a subpopulation of cancer cells with stem cell-like (SCL) phenotypes in solid tumors of breast and digestive system. Consistently, epithelial cancer cell lines in long-term culture are phenotypically and functionally heterogeneous. It is suggested that only a small proportion of transformed cells are clonogenic in vivo and ex vivo to form colonies and to initiate tumor growth in immunodeficient mice. A discrete subpopulation of tumor -initiating SCL cancer cells are highly competent to survive, propagate and spread through the invasive and metastatic cascade. A better understanding of the mechanisms driving the plasticity and pluripotency of stem cells, their derived progenitors and SCL colon cancer initiating cells during tumor progression will open new avenues for the early detection and treatment of local and distant tumors of the digestive tract.

Immunohistochemical staining for mismatch repair proteins, and its relevance in the diagnosis of hereditary non-polyposis colorectal cancer

BACKGROUND

Hereditary non-polyposis colorectal cancer (HNPCC) arises mostly from germline mutations of the mismatch repair genes MSH2 and MLH1. The diagnosis of HNPCC is based on a set of clinical criteria that may be too restrictive to identify all affected patients. Immunohistochemical staining (IHC) for the mismatch repair proteins, MutS homologue 2 (MSH2) and MutL homologue 1 (MLH1), reliably identifies the microsatellite instability phenotype. This study evaluated the ability of IHC to detect germline mutations in an unselected group of patients with colorectal cancer (CRC).

METHODS

All patients with CRC operated on between July 2000 and March 2003, and demonstrating a loss of protein, were contacted. Following informed consent, searchs for germline mutation and methylation of the promoter were performed on normal and tumoral DNA.

RESULTS

Thirty patients agreed to participate, four of whom fulfilled the Amsterdam II criteria. Loss of expression of MLH1 was found in 20 patients, and loss of expression of MSH2 in ten patients. Four of the MLH1-deficient patients had a germline MLH1 point mutation (positive predictive value (PPV) 20 (95 per cent confidence interval (c.i.) 2 to 38 per cent) and 11 had promoter methylation. Seven of the MSH2-deficient patients had a germline MSH2 point mutation (PPV 70 (95 per cent c.i. 54 to 96 per cent), and none showed promoter methylation.

CONCLUSION

MLH1-deficient patients who are young or have a positive family history of cancer should be referred for genetic testing and counselling, whereas MSH2-deficient patients should be counselled in the same way as patients with HNPCC.

Protein kinase WNK2 inhibits cell proliferation by negatively modulating the activation of MEK1/ERK1/2

The recently identified subfamily of WNK protein kinases is characterized by a unique sequence variation in the catalytic domain and four related human WNK genes were identified. Here, we describe the cloning and functional analysis of the human family member WNK2. We show that the depletion of endogenous WNK2 expression by RNA interference in human cervical HeLa cancer cells led to the activation of the extracellular signal-regulated kinase (ERK)1/2 mitogen-activated protein kinases but, in contrast to the depletion of WNK1, had no effect on ERK5. Furthermore, expression of a kinase-dead WNK2-K207M mutant also activated ERK1/2 suggesting that WNK2 catalytic activity is required. Depletion of WNK2 expression increased G1/S progression and potentiated the cellular response to low epidermal growth factor concentrations. The molecular mechanism of ERK1/2 activation in WNK2-depleted cells lies downstream of the Raf kinases and involves MEK1 phosphorylation at serine 298 in both HeLa and HT29 colon cancer cells. This modification is linked to the upregulation of MEK1 activity toward ERK1/2. Together, these results provide evidence that WNK2 is involved in the modulation of growth factor-induced cancer cell proliferation through the MEK1/ERK1/2 pathway. The data identify WNK2 as a candidate tumor suppressor gene and suggest a coordinated activity of WNK kinases in the regulation of cell proliferation.

Opposing roles of netrin-1 and the dependence receptor DCC in cancer cell invasion, tumor growth and metastasis

Deleted in colon cancer (DCC) and UNC5 function as netrin dependence receptors by inducing apoptosis in the absence of their ligand and accordingly were recently designated as putative conditional tumor suppressors. Herein, we determined whether netrin-1 and its receptors are implicated in cancer cell invasion and tumor progression. Expression of DCC, UNC5 and adenosine A2B-receptors (A2B-Rs) was investigated by reverse transcription polymerase chain reaction in human colon cancer cells. The impact of DCC restitution and netrin-1 was evaluated on collagen type I invasion, tumor growth and metastasis in nude mice, cancer cell survival and gene expression profiling. Flow cytometry, poly(ADP-ribose)polymerase-1 and caspase-8 activation were used to evaluate the impact of DCC on cell death. Both netrin-1 and A2B-R activation induced the invasive phenotype through the Rho-Rho kinase axis in DCC-deficient human colorectal cancer cells. Restitution of wild-type DCC blocked invasion induced by netrin-1, A2B-R agonist and other agents. Ectopic expression of netrin-1 led to increased growth of human colon tumor xenografts in athymic mice. Conversely, introduction of wt-DCC in kidney MDCKts.src-ggl cells strongly inhibited metastasis in lymph nodes and lungs and increased sensitivity to apoptosis in hypoxia. DNA microarrays revealed that netrin and DCC had common and divergent impacts on gene expression linked to cell cycle, survival, surface signaling and adhesion. Our findings underscore that netrin is a potent invasion and tumor growth-promoting agent and that DCC is a metastasis suppressor gene targeting both proinvasive and survival pathways in a cumulative manner.

Induction of the adenoma-carcinoma progression and Cdc25A-B phosphatases by the trefoil factor TFF1 in human colon epithelial cells

TFF1 is overexpressed in inflammatory diseases and human cancers of the digestive and urogenital systems. To examine the transforming potential of TFF1 in human colon epithelial cells, premalignant PC/AA/C1 adenoma cells (PC) derived from a patient with familial adenomatous polyposis (FAP) were transformed by the TFF1 cDNA and used as a model of the adenoma-carcinoma transition. Constitutive expression of TFF1 increased anchorage-independent cell growth in soft agar, and induced or potentiated the growth of colon PC-TFF1 and kidney MDCKts.src-TFF1 tumor xenografts in athymic mice. This resulted in reduction of thapsigargin-induced apoptosis and promotion of collagen type I invasion through several oncogenic pathways. Using the differential display approach to identify TFF1 target genes, we found that the dual specific phosphatases Cdc25A and B implicated in cell cycle transitions are strongly upregulated under active forms in both PC-TFF1 and HCT8/S11-TFF1 colon cancer cells. Accordingly, TFF1 expression is absent in normal human colon crypts but is induced in correlation with Cdc25a and b transcript levels and tumor grade in familial and sporadic colon adenomas and carcinomas. We propose that TFF1 and Cdc25A-B cooperate with other dominant oncogenic pathways to induce the adenoma and adenocarcinoma transitions. Agents that target TFF1/Cdc25 signaling pathways may be useful for treating patients with TFF1-positive solid tumors.

[Trefoil factor family gene and peptide expression in pterygium]

PURPOSE

Trefoil factor family (TFF) peptides (formerly P-domain peptides; trefoil factor) are small (7-12 kDa) protease-resistant secreted peptides designated pS2 (or TFF1), SP (TFF2) and ITF (TFF3). Human conjunctival goblet cells (GCs) are known to synthesize TFF, but TFF expression by these cells has not been studied in pathological conditions. We quantified trefoil factor family (TFF) gene transcripts in pterygium, and we immunolocalized TFF protein.

METHODS

Eleven pterygium specimens were studied, together with 19 biopsy specimens of normal human conjunctiva as controls. TFF1 (pS2), TFF2 (spasmolytic peptide) and TFF3 (intestinal trefoil factor) mRNA expression was semiquantified by means of reverse-transcription polymerase chain reaction amplification (RT-PCR). TFF1, TFF2 and TFF3 mRNA levels were determined individually, relative to beta2 microglobulin housekeeping gene mRNA (internal standard), by coamplification of the target fragments and beta2 microglobulin in the same tube. Five pterygia and five normal human conjunctival biopsy specimens were also analyzed for TFF1 and mucin (MUC5AC) protein expression by immunostaining with monoclonal antibodies. Anti-PS2 (Zymed Laboratories, San Francisco), a mouse monoclonal antibody (MAb) against the 30 C-terminal amino acids of human TFF1, and P2802 (provided by Doctor Marie-Christine Rio, Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM, Strasbourg, France), a mouse MAb directed against a synthetic peptide corresponding to the last 28 amino acids of TFF1, were used at 1/20 dilution. A mouse monoclonal antibody directed against the peptidic core of gastric M1 mucin was used as previously described. M1 immunoreactivity is encoded by the MUC5AC gene.

RESULTS

TFF1 and TFF3 mRNA was expressed in all normal conjunctival and pterygium specimens. TFF2 mRNA was not expressed by either sample type, but was expressed by the positive control (human stomach cDNA). TFF1 mRNA expression was stronger in pterygium than in controls (p=0.02). TFF3 mRNA expression was similar in the two sample types (p=0.89). TFF are coexpressed and act in concert with mucins to protect mucous epithelia and trigger wound-healing responses. Inflammation and ulceration of the gastrointestinal tract are associated with increased TFF expression. Conjunctival GCs secrete TFF in both pigs and humans. We found that TFF1 mRNA was overexpressed in pterygium relative to healthy conjunctiva, whereas the TFF1 immunostaining patterns were similar. TFF1 protein expression was confined to goblet cells. However, whereas all GCs were positive for MUC5AC, not all GC were labeled by anti-TFF1 mAbs in either normal conjunctiva or pterygium. The observed TFF1 mRNA overexpression in pterygium was not associated with abnormal TFF1 peptide localization. Increased MUC5AC protein expression would be expected in pterygium, because of increased GC density. Indeed, in conjunctival diseases such as dry-eye syndrome in which GC density is decreased, mucin secretion is also decreased. This could explain the increased expression of TFF1 mRNA in pterygium, although not all GCs expressed TFF1 protein. TFF proteins are copackaged within mucous cell granules; TFF1 preferentially colocalizes with MUC5AC, and TFF3 with MUC2. However, we found some cell granules containing MUC5AC but not TFF1. The proportion of TFF1-negative GCs was similar in pterygium and normal conjunctiva. The normal TFF3 mRNA expression in pterygium was unexpected and suggests that only GCs involved in TFF1 secretion are overrepresented in this pathological tissue. TFF2 mRNA was undetectable in both normal conjunctiva and pterygium, possibly because of its copackaging in mucous cell granules and its preferential cosecretion with MUC6, which is not expressed in the conjunctiva.

CONCLUSION

As in normal conjunctiva, the TFF1 and TFF3 genes are expressed by conjunctival goblet cells in pterygium, contrary to the TFF2 gene. Only TFF1 gene expression was elevated in pterygium compared to normal conjunctiva.

Bile acids stimulate invasion and haptotaxis in human colorectal cancer cells through activation of multiple oncogenic signaling pathways

Bile acids are implicated in colorectal carcinogenesis as evidenced by epidemiological and experimental studies. We examined whether bile acids stimulate cellular invasion of human colorectal and dog kidney epithelial cells at different stages of tumor progression. Colon PC/AA/C1, PCmsrc, and HCT-8/E11 cells and kidney MDCKT23 cells were seeded on top of collagen type I gels and invasive cells were counted after 24 h incubation. Activation of the Rac1 and RhoA small GTPases was investigated by pull-down assays. Haptotaxis was analysed with modified Boyden chambers. Lithocholic acid, chenodeoxycholic acid, cholic acid and deoxycholic acid stimulated cellular invasion of SRC- and RhoA-transformed PCmsrc and MDCKT23-RhoAV14 cells, and of HCT-8/E11 cells originating from a sporadic tumor, but were ineffective in premalignant PC/AA/C1 and MDCKT23 cells. Bile acid-stimulated invasion occurred through stimulation of haptotaxis and was dependent on the RhoA/Rho-kinase pathway and signaling cascades using protein kinase C, mitogen-activated protein kinase, and cyclooxygenase-2. Accordingly, BA-induced invasion was associated with activation of the Rac1 and RhoA GTPases and expression of the farnesoid X receptor. We conclude that bile acids stimulate invasion and haptotaxis in colorectal cancer cells via several cancer invasion signaling pathways.

The role of bile acids in carcinogenesis

Bile acids play a role in colorectal carcinogenesis as evidenced by epidemiological and experimental studies. Some bile acids stimulate growth of normal colonic and adenoma cells, but not of colorectal cancer cells. Moreover, bile acids stimulate invasion of colorectal cancer cells, at least in vitro. One possible mechanism of action is bile acid-induced DNA binding and transactivation of the activator protein-1 (AP-1) by co-operate activation of extracellular signal-regulated kinases (ERKs) and PKC signaling. In the present paper, we review the mechanisms by which bile acids influence carcinogenesis.

[Preclinical studies of oxaliplatin in combination chemotherapy]

Therapeutic innovation in oncology often requires the optimization of combinations with active drugs based on in vitro and in vivo data. This is exemplified by oxaliplatin for which several preclinical studies of combinations have been realized. Oxaliplatin has been combined with 5-fluoro-uracile, gemcitabine, topoisomerase I inhibitors, taxanes demonstrating synergy or additivity. Synergistic and additive effects are often due to the optimization in the use of distinct mechanism of action or resistance and might be associated with no overlapping toxicity when combined in clinical trials.

Suppression of cellular invasion by activated G-protein subunits Galphao, Galphai1, Galphai2, and Galphai3 and sequestration of Gbetagamma

It was shown previously that platelet-activating factor receptors (PAF-Rs) inhibit invasiveness of colonic and kidney epithelial cells induced by the src and Met oncogenes via a pertussis toxin-sensitive mechanism. Therefore, Madin-Darby canine kidney (MDCKts.src) cells were stably transfected with constitutively activated forms of Galphao, Galphai1, Galphai2, Galphai3 (AGalphao/i), two Gbetagamma sequestering proteins [C-terminal end of beta-adrenergic receptor kinase (ct-betaARK) and the Galphat subunit of retinal G-protein transducin], and Gbeta1-Ggamma2 subunits alone or in combination. Cellular invasion induced by src, Met, and leptin was abrogated by the AGalphao/i, ct-betaARK, and Galphat-positive clones, but was induced by coexpression of Gbeta1gamma2. In contrast, invasion stimulated by the trefoil factors (TFFs) pS2 and intestinal trefoil factor in MDCKts.src cells or human colonic epithelial cells PCmsrc and HCT8/S11 was insensitive to PAF, AGalphao, AGalphai1, and AGalphai2, but was abolished by AGalphai3 and the protease-activated receptor-1 (PAR-1) agonist thrombin receptor-activating peptide. Depletion of free Gbetagamma heterodimers by ct-betaARK resulted in a remarkable decrease of cellular adhesion and spreading on collagen matrix. Our data demonstrate the following: 1) PAF-Rs impair cellular invasion induced by src, Met, and leptin via the activation of Galphao and Galphai1 to -3; 2) invasion induced by TFFs is selectively inhibited by PAR-1 receptors and Galphai3 activation; and 3) Gbetagamma dimers are required as positive effectors of invasion pathways induced by oncogenes and epigenetic factors. Thus, redistribution of Galphao/Galphai and Gbeta/gamma heterotrimeric G-proteins by PAF-R and PAR-1 exert differential functions on positive and negative signaling pathways involved in cellular invasion and may serve as potential targets for anticancer therapy.

Activation of cellular invasion by trefoil peptides and src is mediated by cyclooxygenase- and thromboxane A2 receptor-dependent signaling pathways

We have investigated the possible functional relationships between cellular invasion pathways induced by trefoil factors (TFFs), src, and the cyclooxygenases COX-1 and COX-2. Pharmacological inhibitors of the Rho small GTPase (C3 exoenzyme), phospholipase C (U-73122), cyclooxygenases (SC-560, NS-398), and the thromboxane A2 receptor (TXA2-R) antagonist SQ-295 completely abolished invasion induced by intestinal trefoil factor, pS2, and src in kidney and colonic epithelial cells MDCKts.src and PCmsrc. In contrast, invasion was induced by the TXA2-R mimetic U-46619, constitutively activated forms of the heterotrimeric G-proteins Galphaq (AGalphaq), Galpha12, Galpha13 (AGalpha12/13), which are signaling elements downstream of TXA2-R. Ectopic overexpression of pS2 cDNA and protein in MDCKts.src-pS2 cells and human colorectal cancer cells HCT8/S11-pS2 initiate distinct invasion signals that are Rho independent and COX and TXA2-R dependent. We detected a marked induction of COX-2 protein and accumulation of the stable PGH2/TXA2 metabolite TXB2 in the conditioned medium from cells transformed by src. This led to activation of the TXA2-R-dependent invasion pathway, which is monitored via a Rho- and Galpha12/Galpha13-independent mechanism using the Galphaq/PKC signaling cascade. These findings identify a new intracrine/paracrine loop that can be monitored by TFFs and src in inflammatory diseases and progression of colorectal cancers.

Induction of scattering and cellular invasion by trefoil peptides in src- and RhoA-transformed kidney and colonic epithelial cells

Trefoil factors (TFFs) are protease-resistant peptides that promote epithelial cell migration and mucosal restitution during inflammatory conditions and wound healing in the gastrointestinal tract. To date, the molecular mechanism of TFFs action and their possible role in tumor progression are unclear. In the present study, we observed that premalignant human colonic PC/AA/C1 and canine kidney MDCK epithelial cells are not competent to invade collagen gels in response to exogenously added TFFs (pS2, spasmolytic polypeptide, and intestinal trefoil factor). In contrast, activated src and RhoA exert permissive induction of invasion by the TFFs that produce similar parallel dose-response curves in src-transformed MDCKts.src and PCmsrc cells (EC50=20-40 nM). Cell scattering is also induced by TFFs in MDCKts.src cells. Stable expression of the pS2 cDNA promotes constitutive invasiveness in MDCKts.src-pS2 cells and human colonic HCT8/S11-pS2 cells established from a sporadic tumor. Furthermore, we found that TFF-mediated cellular invasion is dependent of several signaling pathways implicated in cell transformation and survival, including phosphoinositide PI3'-kinase, phospholipase C, protein kinase C, and the rapamycin target TOR. Constitutive and intense expression of pS2 was revealed by Western blot analyses and immunohistochemistry in human colorectal tumors and their adjacent control mucosa during the neoplastic progression, from the adenoma to the liver metastases. Our studies indicated that TFFs can be involved in cell scattering and tumor invasion via autocrine loops and may serve as potential targets in the control of colon cancer progression.

Phenotypic and functional characterization of human thymic stromal cell lines

To establish new tools for studying human thymic stromal cells, we transfected adherent cells from a human postnatal thymus using a plasmid encoding SV40 large T antigen. Among the cell lines obtained, we characterized four epithelial cell lines (LT-TEC1 to LT-TEC4) and one thymic myoid cell line (MITC). Several morphological, functional and phenotypic differences were observed between these 2 cell types. Epithelial cells were heterogeneous and larger than myoid cells. Untreated LT-TEC lines expressed MHC class I, ICAM-1 and LFA-3 antigens and not MHC class II antigens, similarly to primary thymic epithelial cells (PTEC), while MITC line expressed only class I and LFA-3 antigens. After IFN-gamma treatment, MHC class II and ICAM-1 antigens were markedly upregulated in LT-TEC lines but not in MITC, indicating the absence or a dysfunction of regulatory factors in MITC line. Myoid cells expressed mRNA for all the subunits of the acetylcholine receptor (AChR) while epithelial cells expressed only the alpha, beta and epsilon subunits. Strikingly, LT-TEC produced much more C-C chemokines and IL-6 than MITC cells, while these latter produced higher levels of IL-8 and TNF-alpha. Altogether, these results reveal phenotypic and functional differences between these two stromal cell types, suggesting a potential involvement of myoid cells in the thymic function.

Small GTPase Rac1: structure, localization, and expression of the human gene

Rac1 is a member of the Rho family of small GTPases involved in signal transduction pathways that control proliferation, adhesion, and migration of cells during embryonic development and invasiveness of tumor cells. Here we present the complete structure of the human RAC1 gene and characterize its expression. The gene comprises 7 exons over a length of 29 kb and is localized to chromosome 7p22. The GC-rich gene promoter shows characteristics of a housekeeping gene and Northern blot studies revealed ubiquitous expression of two rac1 transcripts, 1.2 and 2.5 kb in size. The two transcripts are expressed in tissue-specific ratios, reflecting competition between two alternative polyadenylation sites. The RAC1 but not RAC2 gene contains an additional exon 3b that is included by alternative splicing into the variant Rac1b, a constitutively active mutant which induces the formation of lamellipodia in fibroblasts. These data indicate that the RAC1 gene encodes two signaling GTPases. The gene structure reported here will enable studies on the regulation of RAC1 expression during tumorigenesis and development.

Leptin promotes invasiveness of kidney and colonic epithelial cells via phosphoinositide 3-kinase-, rho-, and rac-dependent signaling pathways

Leptin plays a key role regulating food intake, body weight and fat mass. These critical parameters are associated with an increased risk for digestive and mammary gland cancer in the Western population. Here we determined whether leptin contributes to the invasive phenotype of colonic and kidney epithelial cells at various stages of the neoplastic progression. First, leptin potently (EC50 = 10-30 ng/ml) induces invasion of collagen gels by premalignant familial adenomatous colonic cells PC/AA/C1 and nontumorigenic MDCK kidney epithelial cells, their src-transformed counterparts, and the human adenocarcinoma colonic cells LoVo and HCT-8/S11. Leptin and its Ob-Rb receptors were consistently identified by RT-PCR and immunoblotting in these cell lines, as well as in human colonic epithelial crypts, polyps, colonic tumor resections, and adjacent mucosa. Leptin-induced invasion was effectively blocked by pharmacological inhibitors of several downstream signaling pathways involved in cell transformation, namely, JAK2 tyrosine kinase (AG490), phosphoinositide PI3'-kinase (wortmannin and LY294002), mTOR kinase (rapamycin), and protein kinases C (GF109203X, Gö6976). Accordingly, leptin induces transient elevation of the PI3'-kinase lipid products in JAK2 immunoprecipitates prepared from parental MDCK cells. The leptin effect on invasion was potentiated by the activated form of the small GTPase RhoA and was abrogated by dominant negative mutants of RhoA, Rac1, and the p110alpha of PI3'-K. Our data indicate that leptin may exert a local and beneficial effect on migration of normal colonic epithelial cells and reparation of the inflamed or wounded digestive mucosa. We also emphasize a new role for leptin, linking the nutritional and body fat status to digestive cancer susceptibility by stimulating the invasive capacity of colonic epithelial cells at early stages of neoplasia. This finding has potential clinical implications for colon cancer progression and management of obesity.

Synergistic antitumoral activity of combined UFT, folinic acid and oxaliplatin against human colorectal HT29 cell xenografts in athymic nude mice

This study was designed to assess the inhibition of tumor growth by oxaliplatin combined with UFT and folinic acid (FA). Growth inhibition was studied in nude mice transplanted with human colorectal HT29 tumor cell xenografts and treated for 28 days with oral UFT (20 mg/kg/day) and FA (4 mg/kg/day), i.p. oxaliplatin (10 mg/kg on day 1) or a combination of oxaliplatin, UFT and FA, or else not treated (controls). Tumor surface area and weight were recorded twice a week, and mice were sacrificed at day 28. Two separate experiments were performed for each group of 25 mice. At day 28, mean tumor weights (g) were 2.89+/-0.22 (controls), 2.03+/-0.14 (oxaliplatin), 2.02+/-0.21 (UFT/FA) and 1.23+/-0.17 (oxaliplatin+UFT/FA). For the three treatment groups, tumor weight decreases were 30.1% (p<0.05), 29.9% (p<0.05) and 57.5% (p<0.001), respectively. Combined treatment (UFT/FA+oxaliplatin) reduced tumor weight by 39% compared to oxaliplatin alone (p<0.05) or UFT/FA (p<0.05). These results demonstrate the synergistic effect of the combination of oxaliplatin, UFT and FA in this HT29 cell xenograft model, and warrant further investigations in patients with metastatic colorectal cancer.

Deregulated expression of homeobox-containing genes, HOXB6, B8, C8, C9, and Cdx-1, in human colon cancer cell lines

Previously we have demonstrated a reciprocal deregulation of various homeobox genes (HOXB6, B8, C8 and C9 vs Cdx-1) in human colorectal cancer (CRC). In the present study, using RT-PCR, we have investigated the expression pattern of these homeobox genes in various human colon cell lines, representing various stages of colon cancer progression and differentiation. Thus, we have tested polyposis coli Pc/AA adenoma cells, Caco-2, HT-29 and LS174T adenocarcinoma cell lines. All cell lines, except LS174T, demonstrated a pattern of deregulated homeobox gene expression which resembled that of CRC. In contrast, the pattern of expression of these genes in the highly oncogenic LS174T cells, as well as in Caco-2 cells transfected with activated Ha-ras or Polyoma middle T oncogene, resembled that of the normal mucosa. The reciprocal deregulation of HOX and Cdx-1 genes in CRC and in CRC-derived cell lines suggests a possible role in human CRC development.

Decreased ADP-ribosylation of the Galpha(olf) and Galpha(s) subunits by high glucose in pancreatic B-cells

In HIT-T15 insulinoma B-cells incubated in presence of [(32)P]NAD, we identified by autoradiography and immunoblotting ADP-ribosylation (ADP-R) of the trimeric G-protein Galpha(s) and Galpha(olf) subunits (45 kDa) induced by cholera toxin in M1 (120,000g) and M2 (70,000g) subcellular fractions containing plasma membranes, insulin granules, and mitochondria. This ADP-R indicates that these two fractions contain functionally competent Galpha subunits for adenylyl cyclase activation. Prolonged exposure of HIT-T15 cells to high glucose (25 mM instead of 6 mM) specifically reduced the ADP-R in Galpha(s) and Galpha(olf) subunits in the M1 fraction only, despite the clear increase of their accumulation in this compartment. A similar alteration in the ADP-R of the M1-associated Galpha(s) and Galpha(olf) subunits was observed in pancreatic islets isolated from fasted and fed rats. These results may explain, at least in part, the undesirable effects of sustained hyperglycemia on the cAMP-dependent process of insulin secretion in diabetes.

Vegf, Vegf-B, Vegf-C and their receptors KDR, FLT-1 and FLT-4 during the neoplastic progression of human colonic mucosa

Because the crucial role of angiogenesis has been demonstrated in tumor growth and metastasis, the present study was undertaken to characterize the relative expression of vascular endothelial growth factors VEGF (vascular endothelial growth factor), VEGF-B, VEGF-C, and their receptors KDR (kinase insert domain-containing receptor), FLT-1 (fms-like tyrosine kinase), and FLT-4 in human colonic cancers, in relation to the Astler-Coller pathological classification, and to prognosis. VEGF and VEGF-B gene expression was quantified by Northern blot in 72 tumor samples matched with control tissues. VEGF gene expression was 1.4 times higher in adenocarcinomas than in control tissues (p = 0.02), but did not increase further between Astler-Coller tumor stages A and D, and did not correlate with disease recurrence for patients at stages B2 or C. In adenomas, VEGF mRNA levels were not significantly different from those in the paired control colonic mucosa. The expression pattern of VEGF isoforms, mainly identified by RT-PCR (reverse-transcriptase-coupled polymerase chain reaction) as VEGF121 and VEGF165 and to a lesser extent VEGF189, was comparable in tumor and control tissues. VEGF-B mRNA levels were unchanged during the neoplastic progression of colonic mucosa. In contrast to KDR and FLT-4, the expression of VEGF-C and FLT-1 genes increased in some pathological tissues. These results provide evidence that the early and sustained increase in VEGF transcripts and the expression of multiple angiogenic factors and receptors contribute to the development of colon cancer, and thus constitute a putative target for anti-angiogenic drug therapy.

Vegf, Vegf-B, Vegf-C and their receptors KDR, FLT-1 and FLT-4 during the neoplastic progression of human colonic mucosa

Because the crucial role of angiogenesis has been demonstrated in tumor growth and metastasis, the present study was undertaken to characterize the relative expression of vascular endothelial growth factors VEGF (vascular endothelial growth factor), VEGF-B, VEGF-C, and their receptors KDR (kinase insert domain-containing receptor), FLT-1 (fms-like tyrosine kinase), and FLT-4 in human colonic cancers, in relation to the Astler-Coller pathological classification, and to prognosis. VEGF and VEGF-B gene expression was quantified by Northern blot in 72 tumor samples matched with control tissues. VEGF gene expression was 1.4 times higher in adenocarcinomas than in control tissues (p = 0.02), but did not increase further between Astler-Coller tumor stages A and D, and did not correlate with disease recurrence for patients at stages B2 or C. In adenomas, VEGF mRNA levels were not significantly different from those in the paired control colonic mucosa. The expression pattern of VEGF isoforms, mainly identified by RT-PCR (reverse-transcriptase-coupled polymerase chain reaction) as VEGF121 and VEGF165 and to a lesser extent VEGF189, was comparable in tumor and control tissues. VEGF-B mRNA levels were unchanged during the neoplastic progression of colonic mucosa. In contrast to KDR and FLT-4, the expression of VEGF-C and FLT-1 genes increased in some pathological tissues. These results provide evidence that the early and sustained increase in VEGF transcripts and the expression of multiple angiogenic factors and receptors contribute to the development of colon cancer, and thus constitute a putative target for anti-angiogenic drug therapy.

An anti-insulin serum, but not a glucagon antagonist, alters glycemia in fed chickens

Attempts at altering plasma glucose and, as a consequence, food intake were performed in fed broiler chickens by single i.v. injection of des-His1(Glu9) glucagon amide (a glucagon antagonist) or a non-stimulating anti-insulin serum. Plasma glucose level was not altered by des-His1(Glu9) glucagon amide but was rapidly and largely increased (for at least 2 h) by the injection of the insulin-immune serum. Hour and cumulative food intake were unaltered up to 10 h post injection. These results strongly suggest that in fed chickens, plasma glucose is mainly, if not exclusively, controlled by plasma insulin, and that the transient and heavy hyperglycemia evoked by inhibiting insulin action does not alter food intake.

Differential roles of JNK and Smad2 signaling pathways in the inhibition of c-Myc-induced cell death by TGF-beta

The transforming growth factor beta (TGF-beta) plays an important role in constraining cellular proliferation, but it is also a potent inducer of programmed cell death or apoptosis. Here, we demonstrate that TGF-beta can have an opposite effect, acting as a survival factor to prevent c-Myc-induced cell death in Rat-1 fibroblasts. However, in marked contrast to TGF-beta, Smad2, which is a critical intracellular mediator of the TGF-beta signaling pathway, functions as an antagonist to induce increased cell death. The protective activity of TGF-beta was associated with the activation of c-Jun N-terminal Kinase (JNK) and was not linked to the ability of TGF-beta to promote cell cycle progression. Expression of dominant-interfering forms of various components of the JNK signaling pathway, including Rac1, Cdc42, mitogen-activated protein kinase kinase 4 (MKK4), and c-Jun, abolished TGF-beta-mediated cell survival. Furthermore, overexpression of the constitutively activated mutant RacL61F37A, which selectively stimulates JNK cascade but not G1 cell cycle progression or actin polymerization, was sufficient to prevent apoptosis induced by c-Myc. These findings describe a differential effect of two separated signaling pathways of TGF-beta and indicate for the first time that Smad2 can act as antagonist to suppress TGF-beta-dependent cell survival. Oncogene (2000) 19, 1277 - 1287.

Functional interactions between bile acids, all-trans retinoic acid, and 1,25-dihydroxy-vitamin D3 on monocytic differentiation and myeloblastin gene down-regulation in HL60 and THP-1 human leukemia cells

Bile acids were shown previously to inhibit proliferation and to induce monocytic differentiation in HL60 human acute promyelocytic leukemia cells (A. Zimber et al., Int. J. Cancer, 59: 71-77, 1994). In this report, we hypothesized that bile acids may exert a positive cooperativity with two known inducers of leukemic cell differentiation, all-trans retinoic acid and 1,25(OH)2-vitamin D3. Our results provide evidence that bile acids induced the monocytic differentiation of HL60 and THP-1 human leukemia cells exposed to ineffective concentrations of these inducers. The protein kinase C (PKC) inhibitors H-7 (10 and 20 microM) and staurosporine (5 and 20 nM) modulated the effects of bile acids on HL60 cell differentiation. Most interestingly, bile acids are shown herein to down-regulate the expression of the serine protease myeloblastin gene involved in the differentiation of myeloid hematopoietic cells. In agreement with the recent identification of nuclear receptors for bile acids, our data suggest that functional interactions between nuclear bile acid signaling pathways, PKC, and nuclear receptors for retinoic acid and vitamin D3 are involved in the down-regulation of the myeloblastin gene and the induction of cell differentiation in human leukemic cells.

Cloning of a novel human Rac1b splice variant with increased expression in colorectal tumors

Rac1 is a member of the Ras superfamily of small GTPases involved in signal transduction pathways that induce the formation of lamellipodia, stimulate cell proliferation and activate the JNK/SAPK protein kinase cascade. Here we describe that amplification by RT-PCR of the entire Rac1 coding sequence from a series of human adult and fetal tissues revealed beside the expected Rac1 cDNA, a variant product which contained additional 57 nucleotides between codons 75 and 76. This variant resulted in an in-frame insertion of 19 new amino acids immediately behind the switch II region, including two potential threonine phosphorylation sites for casein kinase II and protein kinase C. Primers designed within and downstream of the inserted nucleotide sequence allowed isolation of a genomic clone with intronic consensus sequences demonstrating that the insertion corresponds to a novel, yet undescribed exon 3b. This Rac1 splice variant, designated Rac1b, was predominantly identified in skin and epithelial tissues from the intestinal tract. Most notably, the expression of rac1b versus rac1 was found to be elevated in colorectal tumors at various stages of neoplastic progression, as compared to their respective adjacent tissues. We suggest that the 19 amino acid-insertion following the switch II region may create a novel effector binding site in rac1b, and thus participate in signaling pathways related to the normal or neoplastic growth of the intestinal mucosa.

Evidence that Smad2 is a tumor suppressor implicated in the control of cellular invasion

The Smad2 protein plays an essential role in the transforming growth factor-beta (TGF-beta) signaling pathway. This pathway mediates growth inhibitory signals from the cell surface to the nucleus. Although Smad2 protein is significantly mutated in human cancers, there is no definitive evidence implicating Smad2 as a tumor-suppressor gene. Here we show that overexpression of the tumor-derived missense mutation Smad2.D450E, an unphosphorylable form of Smad2 found in colorectal and lung cancers, did not abolish the TGF-beta-mediated growth arrest, suggesting that resistance to the growth-inhibiting effects of TGF-beta exhibited by human tumors cannot be linked to the inactivation of Smad2 protein. In contrast, overexpression of Smad2.D450E induces cellular invasion, and this effect was enhanced by TGF-beta. A similar invasive phenotype was obtained in cells expressing another inactivating mutation in Smad2 (Smad2.P445H) found in colorectal cancer. These findings indicate that genetic defects in Smad2 are sufficient to confer the invasion-promoting effect of TGF-beta and reveal that TGF-beta acts through Smad2 to induce cellular invasion by a novel mechanism that is independent of Smad2 phosphorylation by the activated TGF-beta type I receptor.

The oncogenic TEL/PDGFR beta fusion protein induces cell death through JNK/SAPK pathway

The TEL/PDGFR beta (T/P) fusion protein isolated from patients bearing a t(5;12) translocation is transforming when expressed in haematopoietic cells. To examine the signal transduction events activated by this protein, we measured the effect of T/P on activation of the c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) in mouse bone marrow-derived Ba/F3 cells. Significant increase in the activity of JNK/SAPK1 was observed in transient transfection as well as in Ba/F3 cells stably expressing T/P. This activation was abrogated when the T/P-expressing cells were treated with a specific inhibitor of the PDGFR beta tyrosine kinase, indicating that the activity of the PDGFR beta part of the fusion protein was involved in JNK/SAPK activation. Expression of a dominant negative mutant of mitogen-activated protein kinase kinase 4 (MKK4), a direct activator of JNK/SAPK, prevented T/P-induced JNK/SAPK activation. In addition, inhibition of phosphoinositide-3 OH kinase (PI-3 kinase), a promoting survival factor, potentiated the effect of T/P on JNK/SAPK activation. Interestingly, expression of T/P was shown to initiate an apoptotic response that was enhanced by treatment of cells with the PI-3 kinase inhibitor LY294002, suggesting that T/P mediated cell death through activation of JNK/SAPK signalling pathway. Consistent with this hypothesis, expression of the dominant negative mutant of MKK4 decreased T/P-mediated apoptosis, while a dominant-negative mutant of PI-3 kinase enhances cell death. These findings indicate that activation of JNK/SAPK by T/P is related to apoptosis rather than cell proliferation and transformation.

Extracellular regulation of cancer invasion: the E-cadherin-catenin and other pathways

The E-cadherin-catenin complex is pivotal for the regulation of cancer invasion. It not only serves cell-cell adhesion but also transduces signals from the micro-environment to other molecular complexes possibly implicated in invasion. Both functions are disturbed when the extracellular part of E-cadherin is cleaved off. Moreover, upon release into the environment, the E-cadherin fragments may interfere with intact complexes, as indicated by experiments with His-Ala-Val (HAV)-containing peptides that are homologous to parts of the first extracellular domain of E-cadherin. Scatter factor/hepatocyte growth factor (SF/HGF), on binding to its c-met tyrosine kinase receptor, can induce invasion through tyrosine phosphorylation of beta-catenin. SF/HGF-induced invasion is also associated with phosphorylation of pp125FAK, and both invasion and phosphorylation are inhibited by platelet-activating factor (PAF). Activation of the membrane-bound non-receptor tyrosine kinase pp60src can also induce invasion. Signal transduction pathways starting from pp60src include E-cadherin-associated beta-catenin as well as the focal adhesion kinase pp125FAK. Whereas all invasion-inducing pathways implicate phosphoinositide 3-kinase, the PAF pathway seems to be E-cadherin-catenin-independent. We conclude that cancer cell invasion is regulated by paracrine and autocrine factors that are released upon cross-talk with the host cells.

Functional Expression of Receptors for Calcitonin Gene-Related Peptide, Calcitonin, and Vasoactive Intestinal Peptide in the Human Thymus and Thymomas from Myasthenia Gravis Patients

The molecular and functional expression of serpentine membrane receptors for vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP), and calcitonin (CT) were characterized in human thymus and thymomas from myasthenia gravis (MG) patients and thymic epithelial cells either in primary culture (PTEC) or transformed by the siman virus 40 large T (SV40LT) oncogene (LT-TEC). Using RT-PCR combined with Southern analysis, we identified the PCR products corresponding to the receptor (-R) transcripts for VIP, CGRP, and CT in thymus from control subjects and MG patients with either hyperplasia or thymoma. Similar expressions of the VIP- and CGRP-R transcripts were observed in PTEC, whereas the CT-R message was not detected. In LT-TEC, the signals for VIP-R, CGRP-R, and CT-R transcripts were seen with a lower intensity than those in control and MG thymus. In agreement with our molecular analysis, 1) VIP was the most potent peptide among VIP-related peptides (VIP &gt; PACAP &gt; PHM &gt; PHV) to stimulate cAMP production through specific type 1 VIP receptors in both PTEC and LT-TEC; 2) cAMP generation was induced by CGRP in PTEC and by CT in LT-TEC; 3) in frozen thymic sections and by flow cytometry, type 1 VIP-R, CGRP-R, and CT-R were localized in epithelial cells; and 4) in parallel, the transcription of the acetylcholine receptor α subunit (the main autoantigen in MG) was induced by CGRP and CT in PTEC and LT-TEC, respectively. Our data suggest that the neuroendocrine peptides VIP, CGRP, and CT may exert functional roles during MG and malignant transformation of the human thymus.

Functional expression of receptors for calcitonin gene-related peptide, calcitonin, and vasoactive intestinal peptide in the human thymus and thymomas from myasthenia gravis patients

The molecular and functional expression of serpentine membrane receptors for vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP), and calcitonin (CT) were characterized in human thymus and thymomas from myasthenia gravis (MG) patients and thymic epithelial cells either in primary culture (PTEC) or transformed by the simian virus 40 large T (SV40LT) oncogene (LT-TEC). Using RT-PCR combined with Southern analysis, we identified the PCR products corresponding to the receptor (-R) transcripts for VIP, CGRP, and CT in thymus from control subjects and MG patients with either hyperplasia or thymoma. Similar expressions of the VIP- and CGRP-R transcripts were observed in PTEC, whereas the CT-R message was not detected. In LT-TEC, the signals for VIP-R, CGRP-R, and CT-R transcripts were seen with a lower intensity than those in control and MG thymus. In agreement with our molecular analysis, 1) VIP was the most potent peptide among VIP-related peptides (VIP > PACAP > PHM > PHV) to stimulate cAMP production through specific type 1 VIP receptors in both PTEC and LT-TEC; 2) cAMP generation was induced by CGRP in PTEC and by CT in LT-TEC; 3) in frozen thymic sections and by flow cytometry, type 1 VIP-R, CGRP-R, and CT-R were localized in epithelial cells; and 4) in parallel, the transcription of the acetylcholine receptor alpha subunit (the main autoantigen in MG) was induced by CGRP and CT in PTEC and LT-TEC, respectively. Our data suggest that the neuroendocrine peptides VIP, CGRP, and CT may exert functional roles during MG and malignant transformation of the human thymus.

Downregulation of the colon tumour-suppressor homeobox gene Cdx-2 by oncogenic ras

Downregulation of the colon tumour-suppressor homeobox gene Cdx-2 by oncogenic ras Constitutive activation of the ras proto-oncogene is a frequent and early event in colon cancers, but the downstream nuclear targets are not fully understood. The Cdx-1 and Cdx-2 homeobox genes play crucial roles in intestinal cell proliferation and differentiation. In addition, Cdx-2 is a colonic tumour-suppressor gene, whereas Cdx-1 has oncogenic potential. Here, we show that constitutive activation of ras alters Cdx-1 and Cdx-2 expression in human colonic Caco-2 and HT-29 cells that harbour a normal ras proto-oncogene. Oncogenic ras downregulates Cdx-2 through activation of the PKC pathway and a decline in activity of the Cdx-2 promoter AP-1 site. This decline results from a PKC-dependent decrease in the relative expression of c-Jun, an activator of Cdx-2 transcription, compared to c-Fos, an inhibitor of Cdx-2. Unlike Cdx-2, Cdx-1 is upregulated by oncogenic ras and this effect is mediated by activation of the MEK1 pathway. These results indicate that oncogenic ras activation has opposite effects on Cdx-1 and Cdx-2 expression through distinct signalling pathways and they provide the first evidence for a functional link between ras activation and the downregulation of the Cdx-2 tumour-suppressor gene in colon cancer cells.

[Tumoral angiogenesis: physiopathology, prognostic value and therapeutic perspectives]

INTRODUCTION

Angiogenesis activation plays a crucial role in tumoral growth and metastases dissemination. This review summarizes and analyzes current knowledge on molecular mechanisms related to angiogenesis and the prognostic value of its effectors. It also focuses on the therapeutical relevance of various drugs that might inhibit angiogenesic processes.

CURRENT KNOWLEDGE AND KEY POINTS

Tumor angiogenesis involves complex interactions between tumoral, stromal, endothelial cells, fibroblasts and the extracellular matrix. Normal and malignant angiogenesis depends on the balance of proangiogenic and antiangiogenic factors. Endothelial cells are activated by growth factors, such as Vascular Endothelial Growth Factor (VEGF), and proliferate; they release proteases able to induce degradation of the basement membrane and extracellular matrix, and undergo migration and tubulogenesis. Angiostatin and endostatin are two powerful inhibitors of angiogenesis in experimental models. Assessment of intratumoral microvessel density and quantification of angiogenic factors, including VEGF, are of prognostic value in most cancers, particularly in breast cancer. However, the use of these prognosis markers in clinical practice is still controversial due to the lack of prospective studies and to technical limits inherent to the scoring and standardization of immunohistochemical methods.

FUTURE PROSPECTS AND PROJECTS

Better understanding of the molecular basis of angiogenesis allows the development of new therapeutical strategies. Biochemical targets of antiangiogenic therapy are: the interaction between angiogenic factors and their receptors; the interaction of endothelial cells with the extracellular matrix; and intracellular signaling pathways. Angiogenesis inhibitors may not cause tumor regression, but inhibit cellular growth and produce "disease dormancy". Extensive phase I to III clinical trials involving antiangiogenesis therapy are in progress.

Differential transferrin receptor density in human colorectal cancer: A potential probe for diagnosis and therapy

Transferrin receptor density was investigated in human colorectal surgical specimens. Crude membranes were prepared from 23 cancer tumors (adenocarcinoma or malignant villous tumor) and 3 non-cancer tumors (polyadenoma or villous tumor) and 26 adjacent control mucosa. Contrary to non-cancer tumors, Scatchard analysis of 125I-transferrin binding data evidenced higher maximal transferrin binding capacity and lower dissociation constant in cancer tissues (Bmax cancer 1.828+/-0.320 nmol/g, Kd 24.1+/-4.7 nM), as compared to paired control colonic mucosa (Bmax contol 0.851+/-0.182 nmol/g, Kd 30.7+/-7.3 nM), paired t-tests: Bmax p<0.001, Kd p<0.05). As the cancer/control Bmax ratio was 2.6+/-0.4,transferrin carrier constructs should be proposed for cancer imaging or therapy.

Mucin gene expression in human embryonic and fetal intestine

BACKGROUND

The intestinal epithelium is covered by a continuous layer of mucus which is secreted by well differentiated epithelial cells. Disregulation of the expression of mucins has been reported to have possible implications in the neoplastic process which affects intestinal mucosae. It is well known that preneoplastic and neoplastic tissues can express fetal phenotypic characteristics.

AIMS

To assess whether the expression of mucin genes in the intestinal tract is linked to the stage of cellular differentiation and tissue development, by studying the expression of six mucin genes in human fetal small intestine and colon, and also adult tissues.

METHODS

In situ hybridisation was used to study mRNA expression of MUC2, MUC3, MUC4, MUC5B, MUC5AC, and MUC6 in 32 human embryos and fetuses (6.5-27 weeks gestation). Normal adult mucosae were used as controls.

RESULTS

Three mucin genes, MUC2, MUC4, and MUC5AC, were differently expressed in fetal intestine compared with expression in normal adults.

CONCLUSION

These differences in mucin gene expression suggest a possible regulatory role for these products in intestinal epithelial cell differentiation.

Oncogene-induced up-regulation of Caco-2 cell proliferation involves IGF-II gene activation through a protein kinase C-mediated pathway

We previously reported that ras and polyoma middle T (PyMT), a constitutive activator of the src protooncogene product, up-regulated Caco-2 cell proliferation along with protein kinase C (PKC) alpha expression and PKC activity. We aimed to investigate whether oncogene-induced up-regulation of Caco-2 cell proliferation involved stimulation of the autocrine IGF-II/IGF-I receptor (IGFIR) loop described in these cells and if so, to analyse the role of overexpressed and activated PKC. Compared with control vector transfected Caco-2 cells, ras- and PyMT-transfected cells exhibited increased expression of the 6.0 and 4.8 kb IGF-II transcripts. This was due to increased activity of the P3 and P4 promoters of the IGF-II gene which correlated with increased expression and DNA-binding activity of Sp1, a transcription factor interacting with several specific sites in P3 and P4 promoters. Oncogene-transfected cells displayed enhanced autocrine IGF-II production, which was fully responsible for the oncogene-induced increase in their proliferation since this increase was blunted by anti-human IGF-II and IGF1R (alphaIR3) antibodies. PKC mediated oncogene activation of the IGF-II gene presumably through action on Sp1 since (i) PKC activation by phorbol 12-myristate 13-acetate increased Sp1 expression, P3 and P4 activity and IGF-II mRNA in control but not in oncogene-transfected cells; and (ii) PKC inhibition by the PKC inhibitor Gö6976 reduced Sp1, P3 and P4 activity and IGF-II mRNA in all three cell lines. This is the first evidence that ras- and PyMT/src oncogenes up-regulate Caco-2 cell proliferation through a PKC-mediated pathway which stimulates IGF-II gene transcription and thereby increases autocrine IGF-II production. The mechanisms underlying IGF-II gene activation by PKC most probably involve action on Sp1.

Evidence for a role of NF-kappaB in the survival of hematopoietic cells mediated by interleukin 3 and the oncogenic TEL/platelet-derived growth factor receptor beta fusion protein

Interleukin 3 (IL-3) and other hematopoietic cytokines transduce signals that stimulate DNA synthesis and cell survival. In certain chronic myelomonocytic leukemias, a TEL/platelet-derived growth factor receptor beta (PDGFRbeta) fusion protein is produced as a consequence of the t(5;12) translocation. It contains the amino terminus of the transcription factor TEL fused to the transmembranous and cytoplasmic domains of the PDGFRbeta. It is oncogenic as it substitutes for IL-3, thus promoting cell growth and preventing apoptotic cell death. The mechanism by which TEL/PDGFRbeta generates survival signals remains undefined. Here, we report that both IL-3 and TEL/PDGFRbeta initiate a signaling cascade that leads to the activation of the transcriptional factor NF-kappaB. In fact, either cytokine deprivation of IL-3-dependent Ba/F3 cells or exposure of TEL/PDGFRbeta-expressing cells to the specific inhibitor of the PDGFR tyrosine kinase, CGP53716, caused a strong decrease in NF-kappaB activity followed by extensive cell death. Further, treatment with the proteasome inhibitor Z-IE(O-t-Bu)A-leucinal suppressed IL-3 and TEL/PDGFRbeta-dependent survival. The same result was seen upon overexpression of an unphosphorylable form of IkappaBalpha. Because both conditions inactivate NF-kappaB by preventing its translocation into the nucleus, that process seems to be essential for cell survival in response to IL-3 and TEL/PDGFRbeta. Moreover, overexpression of a dominant-negative mutant of the protooncogene c-Myc, a downstream target of NF-kappaB, had a similar effect. We conclude that NF-kappaB plays an important role in maintaining cell survival in response to IL-3 and TEL/PDGFRbeta and that c-Myc may be a downstream effector mediating this effect.

Inhibition by platelet-activating factor of Src- and hepatocyte growth factor-dependent invasiveness of intestinal and kidney epithelial cells. Phosphatidylinositol 3'-kinase is a critical mediator of tumor invasion

This study was designed to characterize platelet-activating factor receptor (PAF-R) expression and function in normal and cancerous human colonic epithelial cells. PAF-R gene transcripts were analyzed by reverse transcription-polymerase chain reaction and Southern blot, using three sets of primers corresponding either to the coding region of the human PAF-R sequence (polymerase chain reaction product: 682 base pairs (bp)) or to the leukocyte- and tissue-type transcripts of 166 and 252 bp, respectively. An elongated splice variant was identified in the 5'-untranslated region of the tissue-type PAF-R transcript (334 bp) in colonic epithelial crypts and tumors. In human colonic PCmsrc cells transformed by c-src oncogene, the hepatocyte growth factor (HGF)-dependent invasiveness of collagen gels was abolished by 0.1 microM PAF and restored by the PAF-R antagonists WEB2086 and SR27417. PAF blocked HGF-induced tyrosine phosphorylation of p125 focal adhesion kinase. The phosphatidylinositol 3'-kinase (PI3'-K) inhibitors wortmannin and LY294002 totally blocked the HGF-induced invasion. Similar effects were observed in ts-srcMDCK kidney epithelial cells transformed by a v-Src temperature-sensitive mutant: (i) PAF and wortmannin exerted additive inhibitory effects on Src-induced invasion and (ii) activated and dominant negative forms of p110alpha PI3'-K, respectively, amplified and abrogated the Src- and HGF-dependent invasiveness of parental and ts-srcMDCK cells. We also provided the first evidence for the contribution of rapamycin-insensitive, pertussis toxin-dependent G-protein pathways to the integration of the signals emerging from activated Met and PAF receptors. These results indicate that PI3'-K is a critical transducer of invasiveness and strongly suggest that PAF exerts a negative control on invasion by inhibiting this signaling pathway. A possible beneficial role of PAF analogs on tumor invasion is therefore proposed.

Overexpression of stromelysin-3, BM-40/SPARC, and MET genes in human esophageal carcinoma: implications for prognosis

Molecular markers can improve staging and predict aggressive clinical behavior in esophageal cancer, thus helping to define appropriate therapeutic protocols and to identify patients who will benefit from surgery. We therefore characterized, by Northern blot and/or immunohistochemistry, the relative expression of three effectors involved in the invasion, angiogenesis, and dissemination of tumor cells in esophageal cancer versus nontumoral mucosae: (a) stromelysin-3 (ST3), a member of the metalloproteinase family; (b) basement membrane 40/secreted protein acidic and rich in cysteine (BM-40/SPARC), an extracellular matrix-associated protein involved in angiogenesis; and (c) the hepatocyte growth factor receptor MET, which triggers the scattering of epithelial cells. Results were analyzed in relation to clinicopathological parameters (cpTNE) including tumor size (T), lymph node status (N), periesophageal tissue invasion (E), disease recurrence, and overall survival. The ST3, BM-40/SPARC, and MET genes were found to be overexpressed in tumor samples compared to control mucosa. BM-40/SPARC and MET mRNA levels were not linked to any one of the cpTNE, indicating that this overexpression occurs at an early stage of neoplastic progression. In contrast, ST3 expression, identified by immunohistochemistry in fibroblastic cells surrounding neoplastic islets, correlated with tumor size and periesophageal tissue invasion. Of the 36 patients studied, those with high ST3 levels had shorter disease-free survival than those with low levels, but there was no relationship between the cpTNE and disease recurrence or survival. Our study demonstrates that ST3, BM-40/SPARC, and MET are involved in different steps of esophageal carcinogenesis and that ST3 overexpression is a marker of aggressive clinical behavior. We conclude that in esophageal cancer, ST3 might help to assess survival and the risk of recurrence after surgical resection.

Differential expression of the CCK-A and CCK-B/gastrin receptor genes in human cancers of the esophagus, stomach and colon

The expression of cholecystokinin (CCK) and gastrin (G) receptors in human gastrointestinal cancers remains poorly documented and is still of a controversial nature. We have measured the levels of mRNA for CCK-A and CCK-B/gastrin receptors using quantitative reverse transcription-polymerase chain reaction (RT-PCR) in primary digestive cancers and hepatic metastases. CCK-A-receptor mRNA was detected in 5 out of 8 esophageal cancers (0.1-1 fg/microg), in 5 out of 8 gastric cancers (0.05-4.2 fg/microg) and in 5 out of 12 colon cancers (0.1-1 fg/microg RNA). CCK-B/gastrin mRNA was not detected in esophageal cancers but was detected in 7 out of 8 gastric cancers (0.05-5.2 fg/microg), and in only 2 out of 12 colon adenocarcinomas (0.05-1 fg/microg RNA). The expression of the CCK-A receptor in esophageal, gastric and colon cancers and of the CCK-B/gastrin receptor in the majority of gastric adenocarcinomas screened may be an important indicator of the influence of CCK and gastrin of local or systemic origin on the growth of these cancers.

Induction of apoptosis by DPC4, a transcriptional factor regulated by transforming growth factor-beta through stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) signaling pathway

Many of the actions of serine/threonine kinase receptors for the transforming growth factor-beta (TGFbeta) are mediated by DPC4, a human MAD-related protein identified as a tumor suppressor gene in pancreatic carcinoma. Overexpression of DPC4 is sufficient to induce the activation of gene expression and cell cycle arrest, characteristic of the TGFbeta response. The stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) is also one of the downstream targets required for TGFbeta-mediated signaling. Here we report that expression of the dominant-interfering mutant of various components of the SAPK/JNK cascade specifically blocked both TGFbeta and DPC4-induced gene expression. These dominant-interfering mutants also inhibited TGFbeta-stimulated DPC4 transcriptional activity. Moreover, we find that overexpression of DPC4 causes transfected cells to undergo the morphological changes typical of apoptosis. These findings define a mechanism whereby TGFbeta signals mediated by DPC4 and SAPK/JNK cascade are integrated in the nucleus to activate gene expression and identify a new cellular function for DPC4.

Antitumor activity of oxaliplatin in combination with 5-fluorouracil and the thymidylate synthase inhibitor AG337 in human colon, breast and ovarian cancers

Oxaliplatin, classical [5-fluorouracil (5-FU)] and non-classical (AG337) thymidylate synthase inhibitors have shown promising activity in the treatment of cancer. This study investigates the cytotoxic effects of oxaliplatin in combination with 5-FU and AG337 in cultured human colon (HT29, CaCo2), breast (MCF-7, MDA-MB-231) and ovarian (2008) cancer cell lines, and their derived counterparts selected for their resistance to 5-FU (HT29-5-FU), doxorubicin (MCF-7mdr) or cisplatin (2008C13). Therapeutic experiments were conducted in mice bearing colon-HT29 xenografts and in the GR hormone-independent mammary carcinoma model. In vitro, oxaliplatin shows potent cytotoxic activity in colon (IC50 from 2.1 +/- 1.1 to 5.9 +/- 1.7 microM), ovarian (IC50 = 10 +/- 1.6 microM) and breast cancer cells (IC50 from 7.4 +/- 2.7 to 17.9 +/- 7.1 microM). Oxaliplatin was a potent inhibitor of DNA synthesis and bound to cellular DNA. Surprisingly, the overall amount of oxaliplatin DNA binding was significantly inferior to that induced by isocytotoxic concentrations of cisplatin in HT29 (p=0.026). In vitro, synergistic antiproliferative effects were observed when oxaliplatin was added to 5-FU and AG337. Those synergistic effects of combinations were maintained in colon HT29-5-FU cancer cells. In vivo, 5-FU increased significantly the antitumor activity of oxaliplatin in HT29 xenografts (p=0.0036), and similarly 5-FU and AG337 increased the activity of oxaliplatin in the GR tumor model (p=0.0012). These data may encourage further clinical investigation of oxaliplatin in combination with classical and non-classical thymidylate synthase inhibitors in the treatment of human cancers.

Differential expression of the CCK-A and CCK-B/gastrin receptor genes in human cancers of the esophagus, stomach and colon

The expression of cholecystokinin (CCK) and gastrin (G) receptors in human gastrointestinal cancers remains poorly documented and is still of a controversial nature. We have measured the levels of mRNA for CCK-A and CCK-B/gastrin receptors using quantitative reverse transcription-polymerase chain reaction (RT-PCR) in primary digestive cancers and hepatic metastases. CCK-A-receptor mRNA was detected in 5 out of 8 esophageal cancers (0.1-1 fg/microg), in 5 out of 8 gastric cancers (0.05-4.2 fg/microg) and in 5 out of 12 colon cancers (0.1-1 fg/microg RNA). CCK-B/gastrin mRNA was not detected in esophageal cancers but was detected in 7 out of 8 gastric cancers (0.05-5.2 fg/microg), and in only 2 out of 12 colon adenocarcinomas (0.05-1 fg/microg RNA). The expression of the CCK-A receptor in esophageal, gastric and colon cancers and of the CCK-B/gastrin receptor in the majority of gastric adenocarcinomas screened may be an important indicator of the influence of CCK and gastrin of local or systemic origin on the growth of these cancers.

Detection of gastric mucins (M1 antigens) in cyst fluid for the diagnosis of cystic lesions of the pancreas

Mucinous cystic tumors of the pancreas must be distinguished from other cystic lesions because of their potential malignancy. Our purpose was to assess the reliability of gastric M1 mucin analysis in the fluid of cystic lesions of the pancreas in comparison or association with carcinoembryonic antigen. M1 mucin and carcinoembryonic antigen were measured in cyst fluid obtained preoperatively by fine-needle aspiration. The lesions consisted of 12 serous cystadenomas, 9 mucinous cystadenomas, 8 cystadenocarcinomas and 6 intraductal mucinous hypersecreting neoplasms. Thirty pancreatic pseudocysts complicating well-documented chronic pancreatitis were also examined. In addition, M1 mucins were localized by immunoperoxidase staining in fetal and normal adult pancreas and in mucinous and serous tumors. Carcinoembryonic values of > 20 ng/ml and M1 mucin values of > 50 U M1/ml represented 82 and 78% sensitivity, respectively, as well as 100% specificity for distinguishing mucinous lesions from serous cystadenomas; the sensitivity for this purpose was 100% using these criteria in combination. Carcinoembryonic antigen values of > 300 ng/ml and M1 mucin values of > 1,200 U M1/ml represented 56 and 30% sensitivity, respectively, as well as 100% specificity for distinguishing mucinous lesions from pseudocysts; the sensitivity for this purpose was 60% using these criteria in combination. By immunohistology, M1 mucins were detected in the wall of mucinous lesions but not in fetal and normal adult pancreas and in serous cystadenomas. Measurement of M1 mucin antigen in cyst fluid could thus improve the diagnosis of mucinous cystic lesions of the pancreas.

Down-regulation of carcinoembryonic antigen family member 2 expression is an early event in colorectal tumorigenesis

Carcinoembryonic antigen gene family member 2 (CGM2), a member of the carcinoembryonic antigen (CEA) family, is expressed in normal colon and rectum but is down-regulated in colorectal adenocarcinomas. In situ hybridization studies demonstrate that CGM2 expression is limited to epithelial cells in the upper third of the crypts. Two other CEA family members, biliary glycoprotein (BGP) and nonspecific cross-reacting antigen (NCA), are similarly expressed, whereas CEA transcripts were found down to the base of the crypts but were less predominant in the upper region. Only low CGM2 and BGP mRNA levels were seen in colorectal tumors. CEA mRNA was expressed at an equivalent level in normal epithelia and in tumor cells, whereas NCA transcript levels were upregulated in tumor cells. Monoclonal antibodies that recognize the CGM2 protein reveal its presence on the apical membranes of epithelial cells in the upper third of the crypts but its absence from colorectal tumors, which do express the CEA and NCA-50/90 proteins. The newly cloned CGM2 3'-untranslated region was used to probe RNAs from adenomas, colorectal tumors at different stages of progression, and liver metastases of colorectal adenocarcinomas. This showed that CGM2 is already down-regulated in adenomas when compared to normal mucosae. The CGM2 expression pattern along with its sequence homology to BGP suggests a similar tumor suppressor function for CGM2.