Dexamethasone affects Fas- and serum deprivation-induced cell death of human osteoblastic cells through survivin regulation.

Glucocorticoid-induced bone loss is the most prevalent form of secondary osteoporosis. Such loss could be due to the alteration of osteoclast and osteoblast lifespan through regulated apoptosis. The current study investigated the effect of dexamethasone on Fas- and starvation-induced apoptosis of mature osteoblasts and their precursors. Using the human osteoblastic hFOB1.19 and the MG63 osteosarcoma cell lines, we found that sub-lethal doses of dexamethasone act on pre-osteoblasts but not on mature cells by increasing their susceptibility to apoptosis. Apoptosis occurs in a caspase-dependent manner as both DNA fragmentation and mitochondrial transmembrane potential dissipation (ΔΨm) are inhibited by the pan-caspase inhibitor zVAD. The increased susceptibility of osteoblast precursors to apoptosis could be due to dexamethasonemediated down-regulation of survivin expression. Dexamethasone can up-regulate survivin, and to a lesser extent Bcl-2, in mature cells but not in pre-osteoblasts. In addition, it can induce FLIP over-expression in osteosarcoma cells. All these effects are inhibited by the glucocorticoid antagonist RU486, indicating that dexamethasone action is specific and, furthermore, that it depends on glucocorticoid receptor. Finally, we have found that survivin and Bcl-2 are essential for pre- and mature osteoblast survival as their silencing is sufficient to induce spontaneous apoptosis in both cell types. In conclusion, our data outline a new molecular mechanism of glucocorticoid-mediated bone loss due to the enhanced apoptosis of precursors compared to mature osteoblasts. Furthermore, the data suggest a mechanism of dexamethasone-induced resistance of osteosarcoma cells to Fas- and stress-induced apoptosis.

Malignant mesothelioma resistance to apoptosis: recent discoveries and their implication for effective therapeutic strategies.

Malignant Mesothelioma is an aggressive and fatal type of tumor. The incidence of mesothelioma has increased in the past 30 years and is now common as male cancers of the liver, bone and bladder, especially in Europe and Australia. The main risk factor is asbestos exposure even if other co-factor, such as simian virus 40 (SV40) could be implied in its etiology. Unfortunately, its incidence is expected to continue to increase for the next decades, also in rapidly industrializing countries, such as India, where it is not recognised as an occupational disease. Furthermore, some disastrous events, such as the World Trade Center Disaster, may contribute to increase future risk for mesothelioma. The treatment-resistant phenotype of mesothelioma is largely due to its ability to escape from the highly regulated apoptotic machinery. The understanding of the molecular mechanisms responsible of the malignant mesothelioma resistance to apoptosis is now advancing, allowing developing new therapeutic strategies to change the natural history and improve survival of patients. This review gives an overview of the main anti-apoptotic strategies devised by malignant mesothelioma and the therapeutic implication and opportunities for this cancer.

Differential gene expression profile reveals overexpression of MAP3K8 in invasive endometrioid carcinoma.

Gene microarray technology is highly effective in screening for differential gene expression and has hence become a popular tool in the molecular investigation of cancer. In the present study, cDNA microarrays containing 2,000 different genes were used to analyze gene expression profiles in ten human postmenopausal endometrioid-paired carcinoma specimens versus corresponding adjacent normal tissue to identify differentially expressed genes. In our study several genes were found differentially expressed. One of them was the MAP3K8, a gene that has never been described to be overexpressed in this kind of malignancy. To validate the differential expression of this gene as well as the membrane array, we performed semiquantitative reverse transcription-PCR analysis. MAP3K8 was found overexpressed in 30% of the endometrial carcinoma samples. To the best of our knowledge this is the first report showing the MAP3K8 oncogene linked to human endometrial carcinoma suggesting that it may be another molecule involved in human endometrial cancer.

Differential gene expression assessed by cDNA microarray analysis in breast cancer tissue under tamoxifen treatment.

Our purpose was to identify tamoxifen (TAM) responsive genes after 30 days of TAM treatment in tumor tissues obtained from women with breast cancer using microarray expression analysis. In our study, we identified 12 candidates to be considered as tamoxifen-modulated genes. Among them, we selected two candidates the TEGT BI-1 (testis enhanced gene transcript Bax Inhibitor-1) and the CD63 gene in order to further confirm their differential expression under tamoxifen effects. We observed that both were down-regulated in tumor tissues of patients during TAM treatment. TEGT is able to inhibit the expression of Bax, which is known to promote apoptosis. On the other hand, CD63 encodes a cell membrane protein and it seems to be involved in mechanisms of platelet activation, cell adhesion and cell motility. We therefore hypothesize that TAM would be able to modulate tumor growth by down-regulating genes involved in mechanisms such as cell cycle control, tumor invasion and metastasis.

Tamoxifen down-regulates CaMKII messenger RNA levels in normal human breast tissue.

Tamoxifen was proven to reduce the incidence of breast cancer by 49% in women at increased risk of the disease in the Breast Cancer Prevention Trial. In order to identify potential candidates to explain the preventive effect induced by tamoxifen on breast cancer, normal breast tissue obtained from 42 fibroadenoma patients, randomly assigned to receive placebo or tamoxifen, was analyzed by the reverse Northern blot and RT-PCR techniques. The cDNA fragments used on Northern blot membranes were generated by the Human Cancer Genome Project funded by the Ludwig Institute for Cancer Research and FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo, Brazil). Total RNA was obtained from normal breast tissue from patients with clinical, cytological and ultrasound diagnosis of fibroadenoma. After a 50-day treatment with tamoxifen (10 or 20 mg/day) or placebo, normal breast tissue adjacent to the tumor was collected during lumpectomy with local anesthesia. One differentially expressed gene, Calcium/calmodulin-dependent protein kinase II (CaMKII), was found to be down-regulated during TAM treatment. CaMKII is an ubiquitous serine/threonine protein kinase that has been implicated in the diverse effects of hormones utilizing Ca2+ as a second messenger as well as in c-fos activation. These results indicate that the down-regulation of CaMKII induced by TAM might represent alternative or additional mechanisms of the action of this drug on cell cycle control and response to hormones in normal human breast tissue.