Characterization of the functional and growth properties of long-term cell cultures established from a human somatostatinoma.

In somatostatinoma, a rare malignant somatostatin (SST)-secreting neoplasia, tumour regression is rarely observed, implying the need for novel antiproliferative strategies. Here, we characterized a long-term culture (SST-secreting cancer (SS-C cells)) established from a human somatostatinoma. High concentrations of SST and chromogranin A were released by SS-C cells and SST release was stimulated by depolarizing stimuli and inhibited by the SST analogue, octreotide. SS-C cells expressed mRNA for SST receptor (SSTR) subtypes 1, 2 and 4, being also able to bind native SST. Moreover, SS-C cells were positively stained with an antibody to SSTR2. SS-C cells also expressed interferon-gamma (IFN-gamma) receptor mRNA and measurable telomerase activity. Our findings indicate that in vitro exposure of SS-C cells to native SST-28, to octreotide, to IFN-gamma, or to 3'-azido-3'deoxythymidine (AZT), a telomerase inhibitor, results in inhibition of SS-C cell proliferation. Concomitant with growth inhibition, apoptosis was detected in SST-, octreotide-, IFN-gamma- or AZT-treated SS-C cell cultures. Taken together our results characterized native SST, SST analogues, IFN-gamma and a telomerase inhibitor as growth-inhibiting and proapoptotic stimuli in cultured human somatostatinoma cells. Based on these findings, the potential of SST analogues, IFN-gamma and AZT, alone or in combination, should be further explored in the medical treatment of somatostatinoma.

Allelic loss in parathyroid tumors from individuals homozygous for multiple endocrine neoplasia type 1.

Homozygosity for the multiple endocrine neoplasia type 1 (MEN1) gene mutation was described in two of three affected siblings of a kindred in which both parents and the third daughter were heterozygotes. Surprisingly, in the two homozygotes, the disease history did not differ from the one of the heterozygotes. In the attempt to unravel genetic differences in parathyroid tumorigenesis between homozygotes and heterozygotes, restriction fragment length polymorphism analysis and microsatellite PCR analysis for loss of heterozygosity (LOH) at the MEN1 gene region on chromosome 11q13 was performed in parathyroid tissues removed at surgery from the mother, her heterozygous sister, and the three siblings. Allelic losses were evidenced in the larger glands of each patient, with a similar pattern of chromosome 11q12-13 losses. The somatic mutation consisted of a large lose of genetic material from chromosome 11. No gross differences exist in the 11q12-13 LOH observed between homozygous and heterozygous carriers. Interestingly, one of the parathyroid tumors from one heterozygote exhibited region of skipped LOH at the 11q12-13 region. The region in the depth of the critical interval retained heterozygosity, whereas those flanking it shared LOH. These findings indicate that inactivation of both copies of the MEN1 gene are not sufficient for parathyroid tumor development in MEN 1 patients and that tumor suppressor genes, other than the MEN1 gene on chromosome 11 or on other chromosomes, can be involved in the pathogenesis of parathyroid tumorigenesis in MEN 1 syndrome.

MEN1 gene mutation analysis in Italian patients with multiple endocrine neoplasia type 1.

Multiple endocrine neoplasia type 1 (MEN 1) is a familial syndrome characterized by parathyroid, enteropancreatic and pituitary tumors. The gene responsible for this syndrome is localized at chromosomal 11q13 region and DNA markers from this region cosegregate with the disease. The recent identification of the MEN1 gene, encoding for a protein termed menin of 610 amino acids, allowed mutational screening to be performed both in affected families and sporadic cases. To date many different heterozygous mutations, spreading across all the encoding sequence, have been identified in MEN 1 patients with no apparent mutational hot spots or genotype-phenotype correlation. To analyze the genetic alterations of the MEN1 gene occurring in Italian patients we performed mutational screening by Denaturant Gradient Gel Electrophoresis followed by sequencing of exons 2-10 of the MEN1 gene in 27 Italian MEN 1 families and in five sporadic cases. We identified 17 different heterozygous mutations in 60% of analyzed cases. Twelve of these mutations are novel. Two mutations each occurred twice in unrelated families but no evidence of genotype-phenotype correlation can be established for these families. The extension of genetic diagnosis to asymptomatic family members allowed the identification of 10 MEN1 mutant gene carriers, one newly described and nine previously detected by linkage analysis with DNA markers from the 11q13 region. Our findings add new information to the diversity of mutations occurring in the MEN1 gene and confirm that the mutational screening of MEN 1 is a useful approach to detect individuals at higher risk of developing MEN 1-associated tumors.

Estrogen synthesis in human colon cancer epithelial cells.

Epidemiological and experimental data suggest an involvement of estrogen in the development and progression of colorectal cancer. In order to determine whether local synthesis of estrogen occurred in human colonic cancer cells, two colorectal cancer cell lines, HCT8 and HCT116, were evaluated for gene expression and enzyme activity of cytochrome P450 aromatase. In addition, the effect on aromatase expression of charcoal-stripped fetal calf serum, of quercetin and genistein and of tamoxifen and raloxifene was investigated in both cell lines. RT-PCR analysis revealed that colorectal adenocarcinoma cell lines contain aromatase as a major component. The conversion of [(3)H]-androstenedione to estrone and labeled water was dose-dependently inhibited by 4-hydroxyandrostenedione and obeyed Michaelis-Menten kinetic with apparent Km values of approximately 20 nM and V(max) values of approx. 200 and 500 fmol/mg protein/h for HCT8 and HCT116 cells, respectively. After 24 h incubation, genistein (1 microM) significantly increased aromatase activity in HCT8 cells, with no effect on HCT116 cells. In accord with previous observation in reproductive tissues, quercetin (1 microM) significantly inhibited the enzyme activity in both cell lines. Also tamoxifen (100 nM) acted as inhibitor, while raloxifene (10 nM) decreased the enzyme activity only in HCT116 cells. The aromatase gene expression modulation by these effective agents was consistent with their effects on enzyme activity. These findings demonstrate for the first time that colorectal adenocarcinoma cell lines express aromatase. Interestingly, the enzyme activity was inhibited by quercetin, one major dietary flavonoid, by tamoxifen, a hormonal therapeutic agent for breast cancer, and by raloxifene, used in the prevention of postmenopausal osteoporosis.

Estrogen metabolism in human colorectal cancer cells.

Epidemiological and "in vitro" studies support a direct role of estrogens in the pathogenesis and/or progression of colorectal cancer (CRC). Recent observations suggest a local synthesis of 17beta-estradiol (E(2)). In the present study, the CRC estrogen receptor beta (ERbeta) positive HCT8, HCT116, DLD-1 and LoVo cell lines were evaluated for expression of functional 17beta-hydroxysteroid dehydrogenase (17betaHSD) types 1, 2, 3, and 4. RT-PCR analysis revealed that while 17betaHSD1 and 17betaHSD4 were expressed in all the four cell lines, 17betaHSD2 and 17betaHSD3 were expressed in a cell-specific manner. The interconversion of tritiated estrone (E(1)) or E(2) evaluated by thin layer chromatography of conditioned media revealed that in HCT8, HCT116, and DLD-1 cells both reductive and oxidative activities were present, the latter showing K(m) values (approximately 10 microM) 40-fold higher than the former (approximately 250 nM). On the contrary, in LoVo cells, estrogens were almost (approximately 90%) completely metabolized to hydrophile compounds. Charcoal-dextrane (DC) stripped fetal calf serum (FCS) (10%), E(2) (10nM), Vitamin D(3) (100nM) and the combined E(2) and Vitamin D(3) treatment were evaluated for modulation of 17betaHSD isoenzymes gene expression and activity. Gene expression and activity of 17betaHSD reductive and oxidative isoenzymes were respectively inhibited and enhanced by Vitamin D(3) in HCT8 and LoVo cells. Surprisingly, DC-FCS induced a marked increase of estrogen metabolism toward hydrophile metabolites in all four cell lines. In conclusion, our results clearly show that metabolism of estrogens by 17betaHSD isoenzymes is functional and modulated by external stimuli in continuous neoplastic colonic epithelial cell lines.

Aromatase expression and activity in the human leukaemic cell line FLG 29.1.

The recent observation that estrogen synthesis occurs in osteoblast-like cells has suggested the aromatase activity as a possible local modulator of bone remodeling in post-menopausal women. To provide further insights into the androstenedione conversion to estrogen in bone-derived cells, we examined the human leukaemic cell line FLG 29.1, which is induced to differentiate toward the osteoclastic phenotype by TPA and TGF-beta1. Southern blot of RT-PCR products with a 32P-labeled cDNA probe for the human aromatase demonstrated that FLG 29.1 cells express aromatase mRNA. The enzyme activity, determined by measuring [3H]H2O release from [3H]androstenedione, obeyed Michaelis-Menten kinetic with apparent Km and Vmax values ranging from 5 to 10 nM and from 200 to 400 fmol/mg protein/6 h. Gene expression, enzyme activity and protein immunoreactivity, evaluated by immunocytochemistry, were stimulated in a time-dependent fashion by 5% charcoal-stripped FCS and by either 1-100 nM TPA or 0.01-0.5 ng/ml TGF-beta1, with maximal responses after 2-3 h exposure. After 24 h incubation of FLG 29.1 cells in the absence of these stimuli the aromatase mRNA and the protein were barely detectable. These findings demonstrate that cells of the osteoclastic lineage synthesize estrogen in vitro and that local cytokines, such as TGF-beta1, are able to induce androstenedione conversion.

A comparison of methods for the analysis of low abundance proteins in desmoid tumor cells.

The desmoids are a group of rare clinically diverse, deep-seated fibrous neoplasms. The exact etiology is unknown, but several factors are considered to be positively correlated with their development and growth, i.e., genetic and hormonal factors and trauma. These tumors may be sporadic or associated with a genetic disease such as familial adenomatous polyposis (FAP). Devoid of metastatic potential, they tend to form large, infiltrative masses which, if not completely excised, recur repeatedly. Although surgery is widely accepted as the first-line treatment for extra-abdominal and abdominal wall desmoids, a proportion of cases are successfully palliated with either estrogen antagonists (tamoxifen, toremifene, and raloxifene) or nonsteroidal anti-inflammatory drugs. We describe and compare four methods for evaluating the expression of estrogen receptors alpha/beta and COX-1 and COX-2 in desmoid tumor-derived cells and tissues: immunocytochemistry, immunohistochemistry, RT-PCR, and two-color Western blot detection with the Odyssey infrared imaging system. Through this comparative analysis, Western blot with Odyssey was recognized as the best method to analyze the expression particularly of low expressed proteins in desmoid-derived cells. The use of a specific and reliable assessment method becomes fundamental in the evaluation of the presence and modulation of proteins which are important but weakly expressed in these rare tumors.

The biphasic effects of nitric oxide in primary rat osteoblasts are cGMP dependent.

Nitric oxide is a gas radical regulating cell behaviour in the cardiovascular, immune, and central nervous systems. It has now been established as an important signalling molecule in bone. However, the effects of this gas radical on osteoblastic function are still unclear; in fact, while NO seems to be involved in anabolic processes mediated by mechanical strain, sex hormones and fracture healing, it also mediates catabolic processes in response to inflammation. We show here that a slow and moderate release of nitric oxide stimulates the replication of primary rat osteoblasts and alkaline phosphatase activity, while a rapid release and high concentrations of NO inhibit proliferation and induce apoptosis. We demonstrate that both the stimulatory and apoptosis-inducing effects of NO on primary osteoblasts are mediated by the second messenger cGMP, since both are abolished by the guanylate cyclase inhibitor ODQ.

Functional estrogen receptor beta in colon cancer cells.

Evidence exists for expression of estrogen receptor beta (ERbeta) in human colonic mucosa. Here we investigated the expression of the classical ER (ERalpha) and of four isoforms of the human ERbeta in HCT116, HCT8, DLD-1, and LoVo colon adenocarcinoma cell lines. In addition, [(3)H]17beta-estradiol (17betaE(2)) binding to intact colon cancer cells was evaluated. RT-PCR and Western blot analyses showed lack of expression of the classical ERalpha in the four colon cancer cell lines. Conversely, wild-type ERbeta isoform 1 was highly expressed in HCT8, HCT116, DLD-1, and LoVo cells and isoforms ERbeta2-5 were present in HCT8 and HCT116 cells. Scatchard and Hill analysis of [(3)H]17betaE(2) binding to the four different colon cancer cells revealed the presence of two classes of binding sites, one with high affinity (K(d) values of 1-2 nM) and the other with lower affinity (K(d) values of 10-20 nM). Forty-eight hour-pretreatment of cells with 1 and 10 nM 17betaE(2) did not induce an increase of progesterone-specific binding to HCT8 cells, while a significant induction was observed after treatment with 10 nM 17betaE(2) in HCT116 and DLD-1 cells and with both concentrations in LoVo cells. In addition, 1 pM-0.1 nM 17betaE(2) significantly induced cell proliferation of HCT8 cells, while reducing growth of HCT116 and DLD1 cells at 10 nM-1 microM concentrations and of LoVo cells at all tested concentrations (1 pM-1 microM). These in vitro findings pose the basis for in vivo functions of ERbeta and ERbeta-interacting molecules in human colon cancer tissue.

Heterogeneity of binding sites and bioeffects of raloxifene on the human leukemic cell line FLG 29.1.

The benzothiophene divarative raloxifene is known to mimic estrogen in human bone remodeling. To investigate the "in vitro" properties of raloxifene on osteoclast precursors, the human leukemic cell line FLG 29.1, which differentiates toward the osteoclastic phenotype, was examined for raloxifene binding and for evidence of its bioeffects. Scatchard and Hill analysis of binding data with the tritiated raloxifene demonstrated the presence of two classes of binding sites in both nuclear and cytosol fractions with Kd values of approximately 1 nM and approximately 5 nM, respectively. In addition, analysis of binding data using tritiated 17 beta E2 as ligand at high concentrations (10-40 nM) and either unlabeled 17 beta E2 or raloxifene as competitors gave similar results demonstrating the presence of type II EBS in these cells. Picomolar concentrations of raloxifene significantly (p < 0.05) inhibited cell proliferation. Moreover, the compound at nanomolar concentrations induced a significant dose- and time-dependent increase of progesterone receptor, and activated apoptotic cell death. These findings clearly demonstrate that raloxifene acts as an estrogen agonist in FLG 29.1 cells, acting through the estrogen receptor and, possibly, via multiple cooperative binding component(s).

Telomerase repeat amplification protocol (TRAP): A new molecular marker for parathyroid carcinoma.

Telomerase results to be active in human germ, stem cells, several malignant cell tumors and in immortalized cell lines. In order to investigate if molecular mechanisms other than Rb gene inactivation can be helpful to diagnose malignancy of parathyroid tumors, we decided to investigate the presence of active telomerase in homogenates from different pathological parathyroid tissues (hyperplastic, adenomatous, carcinomatous, and normal) and primary cell cultures. The TRAP assay was performed to detect this activity in histologically characterized normal, hyperplastic, adenomatous, and carcinomatous human parathyroid tissues, primary cell lines, and one metastatic tissue from parathyroid carcinoma. Only malignant parathyroid glands and the metastatic tissue were TRAP positive. Our findings suggest that telomerase expression could represent an important molecular mechanism underlying the acquisition and progression of an aggressive phenotype of epithelial parathyroid cells and it may help to predict their malignant potential. The TRAP assay is easy to perform and it could become an additional tool to be included in the harmamentarium for the molecular diagnosis of parathyroid carcinoma.