Celecoxib, a cyclooxygenase-2 inhibitor, potentiates the chemotherapic effect of vinorelbine in the medullary thyroid cancer TT cell line.

We analyzed the in vitro effects of celecoxib, a COX-2 inhibitor, and determined if celecoxib can sensitize a human MTC-derived cell line (TT) to chemotherapeutics. We found that celecoxib induced apoptosis in TT cells and decreased drug efflux by reducing the expression of MDR-1 mRNA, which codes for the drug efflux pump P-gp. We also observed that TT cells were 10-fold more resistant to doxorubicin than to vinorelbine, mimicking what can be observed in clinical practice. In addition, we found that the combination of celecoxib and vinorelbine, but not doxorubicin, induced a significant reduction in cell viability and a significant increase in apoptosis. In conclusion, we showed that celecoxib was able to enhance the chemotherapeutic effect of vinorelbine. A clinical trial exploring the in vivo activities of celecoxib in MTC patients who cannot benefit from available treatments would be desirable, taking into account the possible risks of cardiovascular effects of this drug.

In silico and in vitro analysis of rare germline allelic variants of RET oncogene associated with medullary thyroid cancer.

Germline and somatic RET oncogene mutations are found in 98% hereditary and 40% sporadic medullary thyroid carcinomas. Our aim was to analyse by in silico and in vitro assays the transforming activity of six rare RET mutations (T338I, V648I, M918V, A883T, S904F and M848T). Six known RET mutations were used as controls. The in silico analysis showed the highest score value (i.e. 65) for S904F, M848T, M918T and C634R, whereas L790F, G691S, T338I and V648I had 0 score. Intermediate score values were obtained by A883T (score=55), M918V, V804M and Y791F (score=15). The in vitro focus formation assay showed that cells transfected with S904F, M918T, M848T or C634R generated the largest number of focus formation units (FFU). Intermediate numbers of FFU were observed in cells transfected with M918V, V804M, Y791F or A883T, while cells transfected with L790F, G691S, T338I or V648I showed a number of FFU similar to control cells. A positive correlation between the in silico score and in vitro FFU was found (P=0.0005). Only cells transfected with M918T or C634R grew faster and generated higher number of colonies in soft agar than control cells. However, the cells that were transfected with V804M produced an intermediate number of colonies. In conclusion, two of the six rare RET mutations, S904F and M848T possessed a relatively high transforming activity but a low aggressiveness; the other four mutations T338I, V648I, M918V and A883T were low or non-transforming, and their ability to induce tumoural transformation might be related to particular genetic conditions.

Re-differentiation of thyroid carcinoma cell lines treated with 5-Aza-2'-deoxycytidine and retinoic acid.

We studied cell growth rate, mechanisms of growth inhibition, phenotype re-differentiation, expression of RARalpha, beta, gamma and differentiation thyroid genes before and after combined treatment with 5-Aza-CdR and RA (5-Aza/RA) of human thyroid carcinoma cell lines (FRO, WRO, TT). Furthermore, the activity and localization of the re-expressed sodium-iodide-symporter (NIS) protein was analyzed. After 5-Aza/RA treatment, all cell lines showed a significant reduction in cell growth. This was associated with apoptosis in the TT, with inhibition of cell proliferation in the WRO, and with cell cycle impairment in FRO and WRO. FRO and WRO treated with 5-Aza/RA lost the ability to grow in soft agar. FRO re-expressed thyroid transcription factor-1 and thyroglobulin, TT and WRO re-expressed PAX-8 and FRO and TT re-expressed RARbeta and NIS mRNA. Despite this expression, they were unable to take up iodine: a cytoplasmic localization of NIS protein was demonstrated in FRO. In conclusion, besides a significant reduction in cell growth rate and in the ability to grow in soft agar, treatment with 5-Aza/RA partially re-differentiated FRO and induced expression of NIS mRNA and protein in FRO and TT, but this treatment was unable to restore the functional activity of NIS, likely because it was located into the cytoplasm without reaching the plasma membrane.

Retinoic acid receptor beta2 re-expression and growth inhibition in thyroid carcinoma cell lines after 5-aza-2'-deoxycytidine treatment.

The treatment of both undifferentiated and de-differentiated thyroid tumors, which are unresponsive to radioiodine, represents one of the biggest challenges for thyroidologists. The aim of the present study was to investigate in vitro the methylation status of retinoic acid receptors (RAR)beta2 promoter and the effect of the demethylating agent 5-aza-2'-deoxycytidine (5-Aza-CdR) on 5 human thyroid cancer cell lines. The methylation status of RARbeta2 promoter was analyzed by methylation-specific PCR. The effect of 5-Aza-CdR on cell growth and apoptosis was evaluated by cell counting, enzymelinked immunosorbent assay tests and fluorescence-activated cell sorting analysis, while the effect on the expression of RAR and thyroid-specific genes was measured by qualitative and quantitative RT-PCR. Methylation of RARbeta2 promoter was present only in ARO cells. 5-Aza-CdR determined growth inhibition in all cell lines, probably due to apoptosis in WRO, NPA, and ARO cells, and to inhibition of DNA synthesis in TT cells. Treatment with 5-Aza-CdR induced the expression of RARbeta mRNA in ARO and FRO cells, a slight increase of the expression of Tg, TPO and thyroid trancription factor 1 (TTF-1) mRNA and the new expression of low levels of NIS in TT cells. A significant increase of TTF-1 mRNA in FRO cells was also observed. In this study we demonstrated that RARbeta2 promoter was methylated in ARO cell line. However, the 5-Aza-CdR treatment induced RARbetamRNA expression not only in ARO but also in FRO and TT cell lines, whose RARbeta2 promoter was unmethylated. A significant reduction of cell growth, but not cell re-differentiation, was also observed after 5-Aza-CdR treatment.

[Serum mesothelin dosages in follow-up of previously exposed workers]. / Il dosaggio della mesotelina sierica nel follow-up dei lavoratori ex esposti ad amianto.

High dosages of Serum Mesothelin have been demonstrated to be significantly associated to Pleural Malignant Mesothelioma. We recently demonstrated that Serum Mesothelin may be clinically helpful both for diagnostic and prognostic purposes, with the best cut-off corresponding to 1 nM. We also discovered that high levels of Serum Mesothelin are significantly associated to Lung Cancer. The usefulness of this marker in secondary prevention has been suggested, though never demonstrated. We therefore started a long-term prospective cohort study including previously asbestos-exposed workers. These subjects periodically underwent both radiological tests and serum mesothelin dosages. As a mid-term goal of this longitudinal study we decided to check the variability of mesothelin dosages, comparing baseline and follow-up values, as well as the possible correlation with age, duration of exposure, smoking, any abnormality of respiratory functional tests (RFT) and/or radiological tests. At baseline, Mesothelin mean value was 0.66 +/- 0.4 (range 0.08-2.2 nM). Both age (p = 0.04) and abnormal thoracic TC (p = 0.04) were significantly correlated with increased serum mesothelin levels and increasing age. No association was found between baseline mesothelin levels and duration of asbestos exposure (p = 0.5), smoking habits (p = 0.2), abnormal RFT, DLCO (carbon monoxide diffusing capacity) or thoracic X-ray. No significant variation was observed between mesothelin values at baseline and at follow-up (p = 0.2).

[SV40: a possible co-carcinogen of asbestos in the pathogenesis of mesothelioma?]. / SV40: un possibile co-cancerogeno dell'amianto nella patogenesi del mesotelioma?

BACKGROUND: The etiopathogenic role of asbestos in causing malignant mesothelioma of the pleura is clearly supported by an impressive amount of data. Despite the frequent association with previous exposure to asbestos, only a relatively small fraction of those exposed develop malignant mesothelioma. The long latency period between initial exposure and onset of the tumor suggests that human mesothelioma, like many other tumors, has a multi-stage evolution with the occurrence of many mutating events involving various tumorigenic agents, probably in part initiating and in part promoting development. Recently this has raised great interest in the scientific world, in an attempt to identify possible factors which together with asbestos may have a role in developing this rare malignant tumor. Ionizing radiations and genetic susceptibility have occasionally been identified as the culprits. A virus called SV40 has been gaining increasing scientific credibility since the mid 1990's as a potential co-carcinogen of asbestos. OBJECTIVES: The aim of this article was to examine the supposed interaction between asbestos and SV40 in the pathogenesis of mesothelioma and the way this simian virus has become a human virus. METHODS: All biomolecular and epidemiological data available from medical literature along with the results of the experiments performed during the last 7 years in our department laboratories were reviewed and compared. RESULTS: The first two pieces of experimental evidence of the presence of SV40-like DNA sequences in mesothelioma samples were obtained in 1994 in the United States, and one year later in our laboratories. After these two studies many research groups started carrying out similar experiments, obtaining comparable results in most cases. Moreover, beyond the mere detection of viral DNA sequences large amount of biomolecular data has recently been added in favour of its role in the pathogenesis of mesothelioma. Epidemiological studies published to date were unable to provide similar unanimous results. Data regarding the source of human infection are still debatable, even if the inadvertent administration of contaminated poliovaccines to millions of people in Europe and the United States between 1955 and 1963 remains one of the most reasonable hypotheses. CONCLUSIONS: On the basis of all the biomolecular data reviewed and partially on the basis of epidemiological studies, SV40 seems to be the best candidate as a cofactor with asbestos in the development of human mesothelioma.

New breakpoints in both the H4 and RET genes create a variant of PTC-1 in a post-Chernobyl papillary thyroid carcinoma.

Two main types of RET/PTC oncogene, named RET/PTC-1 and 3, occur in papillary thyroid carcinomas especially in those from Belarus children after the Chernobyl nuclear accident. Several variants of RET/PTC-3 have also been found, having different break points with respect to the classical RET/PTC-3. To our knowledge, no variant of RET/PTC-1 has been described up to now. We found a post-Chernobyl papillary thyroid carcinoma with an RET/PTC-1 rearrangement characterized by a transcript longer than expected. Sequence analysis of the PCR product obtained after RT-PCR revealed new fusion points between H4 and RET genes. The genomic sequence showed new breakpoints in both H4 intronic and in RET exonic regions. The RET gene breakpoint occurred within exon 11, at variance with the classical form of RET/PTC-1, in which it is in intron 11. As a consequence of this new fusion point, the transcript included 132 nucleotides of exon 11, coding for 44 amino acids of RET protein. Regarding the H4 gene, the classical breakpoint is in the first intron and the cDNA contains a fragment of 339 nucleotides. In our case the cDNA had a longer fragment of H4 involving a total of 1266 nucleotides. Sequencing of genomic DNA revealed a rearrangement breakpoint at position 886 of a new H4 intron located downstream of the 1266 coding region. Furthermore, as a consequence of the activation of a cryptic splicing site, 132 nucleotides of this intron were spliced between the H4 and RET genes. Sequence analysis of the new chimera showed that the original frames of H4 and RET were joint with the intronic sequence without disruption of the open reading frame (ORF). Moreover, the genomic DNA of this case showed transforming activity in the DNA-mediated transfection assay using NIH-3T3 cells. In conclusion, we describe here the first variant of RET/PTC-1 oncogene, which we have termed 'long'-PTC-1, characterized by new breakpoints of both genes involved in the rearrangement and having transforming activity. Similar to previously reported PTC-3 variants, long-PTC-1 has been found in a post-Chernobyl papillary thyroid carcinoma confirming that RET/PTC rearrangements other than the classical forms (RET/PTC-1 and -3) are specifically associated with radiation-induced papillary thyroid cancer.

SV40 can be reproducibly detected in paraffin-embedded mesothelioma samples.

We studied tissue sections from 18 paraffin embedded mesothelioma specimens diagnosed by the Pathology Department of S. Chiara Hospital of Pisa. Using PCR analysis and Southern blot hybridization we examined the specimens for the DNA regulatory region of the virus. 10/18 (55.5%) of the samples tested contained SV40 DNA regulatory sequences, and of these positive samples, 80% were found to contain Tag sequences by PCR and Southern Blot hybridization. These results confirm that SV40 can be amplified and detected in paraffin embedded mesothelioma samples.

Simian virus 40-like DNA sequences in human papillary thyroid carcinomas.

Sequences of the SV40 virus, a virus of Asian macaques, have been found in human tumors, such as pleural mesotheliomas, ependimomas and choroid plexus tumors. Transgenic mice carrying the SV40 large T gene under the transcriptional control of the thyroglobulin gene promoter, develop thyroid dedifferentiation and follicular thyroid cell proliferation, leading to thyroid hyperplasia and adenocarcinomas. On these bases we investigated the presence of SV40 DNA sequences in 69 samples of papillary thyroid carcinomas (PTC) and in other thyroid and non-thyroid carcinomas, as well as in benign thyroid diseases. By Southern blot and PCR amplification followed by sequence analysis, we found the presence of SV40-related sequences integrated in the tumoral DNA of three cases of PTC. At least the 203 bp fragment of the aminoterminus of large T antigen, the 294 bp fragment of the VP1 gene and the 483 bp entire regulatory region were present in the tumoral DNA of these patients. SV40 sequences were not found in tissues other than PTC. Our results demonstrate that, in addition to previous findings in mesotheliomas and brain tumors, SV40 is somehow linked to papillary thyroid carcinoma. Although our data do not demonstrate a causative role in the development of PTC, this possibility must be considered and requires further studies.

Oncogenic risk in a chemical plant: a methological approach and preliminary results.

One of the major problems that occupational medicine has to deal with is cancer risk assessment. Recent Italian legislation requires the evaluation of occupational exposure to carcinogens in all workplaces, but a standardized method to be used in the environmental and biological criteria is generally lacking. The objective of this report is to identify a multidisciplinary approach to the research on this topic. The study is based on a chemical plant that produces pitch. The multidisciplinary approach is based on risk- and health-damage assessments. Ethical aspects are also taken into account, and the research design incorporates an informed consent for all employees. Some preliminary results are available. From the environmental point of view, all parameters provide an airborne concentration value below threshold limit values (TLVs), but biological monitoring demonstrates an increased urinary excretion of 1-OH-pyrene in all tested subjects. In conclusion, the first objective of our study is to demonstrate the carcinogenic risk of employees, searching for an agreement between environmental analysis, biological monitoring, and health effect data. A close collaboration between different professions is necessary.

A simple method to reveal possible ras mutations in DNA of urinary sediment cells.

Occupational and environmental exposure to carcinogens is reported to be responsible for 25% of all bladder tumors. Among many genetic alterations found in tumor bladder cells, chromosome aberrations and mutations of some oncogenes, such as ras genes, are common. Studies conducted to determine the rate and type of ras mutations involved reported rather contrasting results. Researchers agree that among the three members of the ras family, only H-ras is subject to mutations, mostly at codon 12. The rate of these mutations is still under investigation, although it has been evaluated as being between 6 and 76%. Using various techniques, some studies have shown that when a ras mutation occurs in a bladder tumor, it is also present in urinary sediment cells of the same patient. We suggest a simple method to directly detect ras mutations at codon 12 in urinary sediment.

Molecular biology studies on mesothelioma tumor samples: preliminary data on H-ras, p21, and SV40.

The ras gene is one of the oncogenes most commonly detected in human cancers; this protooncogene is converted to active oncogene by point mutations occurring at either codon 12, 13, or 61. SV40 is a DNA-transforming simian virus, a 105 bp sequence of which has been shown recently to be present in a significant fraction of human mesothelioma cells. Eleven human malignant mesotheliomas were examined for H-ras gene mutations at codon 12, 13, and 61 and for the presence of SV40-like sequences. DNA prepared from formalin-fixed and paraffin-embedded tissue was amplified by means of PCR and analyzed using designed restriction fragment length polymorphism. No mutation with respect to H-ras was found in any tumor sample, but the majority of mesothelioma cells contained SV40-like sequences.