Carlo Botti

Structure, function and gene expression of epithelial mucins.

In this review the main characteristics, i.e., structure, function and gene expression, of the different mucins are discussed. Mucin-type molecules consist of a core protein moiety (apomucin) where a number of carbohydrate chains are attached to serines and threonines by glycosidic bonds. O-linked carbohydrates form up to 80% of the molecule and the length of the glucidic side chains varies from one to more than 20 residues. At least eight mucin-like genes have been isolated so far, and the main characteristic is the presence of a central domain composed of a variable number of “tandem repeats”. The sequence homology of the central domain among the different members of the mucin-type family is limited, indicating that this internal domain is unique for each mucin. Thanks to the integrated results of genetic, immunological and biochemical studies, it is now possible to identify eight apomucin genes, namely MUC1, MUC2, MUC3, MUC4, MUC5AC, MUC5B, MUC6 and MUC7. MUC1 is the best characterized mucin and it is expressed on the apical surface of most polarized epithelial cells. The MUC1 gene has been cloned and sequenced. The MUC2 gene encodes a typical secretory gel-forming mucin which represents the predominant form in human intestinal and colon tissues. Another intestinal mucin is MUC3. The MUC4, MUC5AC and MUC5B genes have been isolated from a bronchial tissue cDNA library. The MUC4 and MUC5AC genes are mainly expressed in the respiratory tract, in gastric and reproductive mucosa, while MUC5B is highly detectable only in the bronchial glands. The MUC6 gene is expressed by gastric tissue and, recently, MUC7 has been cloned and sequenced using a salivary cDNA library.

Comparison of three different methods for radiolabelling human activated T lymphocytes

One approach in the treatment of ovarian cancer MOv18/anti-CD3 (biMAb OC/TR), which recognizes a 38-kDa glycoprotein expressed on ovarian carcinomas and the CD3 T cell receptor. However, little is known about the in vivo biodistribution of injected activated lymphocytes, information that could be obtained by scintigraphic imaging of radiolabelled T cells in order to visualize the migratory pattern. We compared the efficiency, stability and toxicity of technetium-99m hexamethylpropylene amine oxime (HMPAO),indium-111 oxine and fluorine-18 2-fluoro-2-deoxy-d-glucose (FDG) in radiolabelling activated lymphocytes targeted with biMAb OC/TR. The mean labelling efficiencies of111In-oxine and18F-FDG using 2.5×108 lymphocytes (68% and 64%, respectively) were more than twice that of99mTc-HMPAO (31%). Retention of the radionuclide in the cell was highest in the case of111In-oxine labelling (less than 25% of the initial cell-bound activity released after 240 min, as compared with 44% of the99mTc label in the same period and 45% of18F radionuclide released after 150 min). None of the three radiolabelling reagents induced any significant alteration in cell viability or immunophenotype. However, both111In-oxine and18F-FDG induced a loss of cytotoxic activity of lymphocytes against the ovarian carcinoma cell line IGROV1, and all three radiolabelling reagents caused a significant reduction in the proliferative ability of labelled lymphocytes compared to controls, with cell death occurring after 8–9 days. Radiolabelling with the more stable111In-oxine reagent using a higher number of lymphocytes (1.4x109) but the same total activity (around 55.5 MBq) resulted in improved labelled T cell viability and proliferative ability, although the mean labelling efficiency decreased (35.8%). Together the data suggest that111In-oxine at low activity per cell is the most appropriate reagent for radiolabelling activated retargeted T lymphocytes useful for in vivo biodistribution studies.

Neuron-Specific Enolase Evaluation in Patients with Neuroblastoma

Neuron-specific enolase (NSE) may be of interest for the prognostic evaluation and follow-up surveillance in patients with neuroblastoma. We evaluated NSE levels in 80 patients with neuroblastoma. The marker correlated with stage (in stage 1 patients, the median NSE level was 9.9 ng/ml, in stage 2, 45.1 ng/ml, in stage 3, 49 ng/ml, in stage 4, 93.9 ng/ml, in stage 4S, 53.4 ng/ml) and with survival. In patients with a favorable or a poor outcome, the difference in basal NSE serum levels was statistically significant (p = 0.0001). Serial measurements revealed that there was a good correlation between NSE levels and disease course. We concluded that NSE is a good marker for neuroblastoma and its quantitative determination in serum is valuable in the management of these patients to confirm the diagnosis, monitor the effect of treatment and detect recurrent disease.

Differential expression of mucins 1–6 in papillary thyroid carcinoma: evidence for transformation-dependent post-translational modifications of MUC1 in situ

Mucins are primary glycoproteins of epithelia that are known to undergo major changes in their post‐translational processing during neoplastic transformation. This study has examined the expression pattern of seven primary mucins, ie mucin (MUC) 1, 2, 3, 4, 5AC, 5B and 6, in normal, hyperplastic, benign neoplastic, and papillary‐type carcinoma (PTC) tissues of the thyroid. MUC1 and MUC5B were the only mucins to be widely transcribed in both benign and malignant tissues. In contrast, MUC4 transcripts were undetectable in normal thyroids, and were present in only 40% of the hyperplastic and malignant thyroid tissues. In PTC, MUC1 was identified as a single mRNA transcript, rejecting the idea that this mucin may undergo transformation‐dependent alternative splicing in thyroid tumours. The tissue distribution of MUC1 and MUC4 proteins was highly heterogeneous: this largely paralleled their mRNA expression profiles and supported the conclusion that whereas MUC1 was ubiquitously expressed in PTC, MUC4 was detectable in less than 20% of the cases analysed. In order to determine whether post‐translational modifications of MUC1, putatively associated with malignancy, also occurred in the mucin produced by PTC, immunohistochemistry was performed with a panel of well‐characterized anti‐MUC1 antibodies in conjunction with digestion of the tissue sections with deglycosylating enzymes. These experiments, which were supported by immunochemical analyses of the MUC1 and MUC4 glycoforms extracted from tissues, collectively demonstrated markedly divergent MUC1 glycosylation profiles in normal and benign thyroid tissues when compared with PTC. Characteristically, these latter neoplastic cells produced mucin molecules carrying complex poly‐N‐lactosamine‐type glycans capped with fucose and neuraminic acid residues. The present study also found evidence in PTC for the potential presence of proteolytically processed MUC1 isoforms which differ in their post‐translational traits depending on whether they are retained on the cell surface or secreted into the extracellular space. It is proposed that the observed differences in the glycosylation properties of normal and neoplastic MUC1 may be exploitable as an ancillary tool in the diagnosis of PTC. Copyright

Biochemical characteristics and recent biological knowledge on prostate-specific antigen.

Since its identification in seminal fluid in 1971, much new information has been obtained about the biology and expression of prostate-specific antigen (PSA). PSA is a glycoprotein composed of 93% amino acids and 7% carbohydrates, with a molecular weight of about 30,000 Da. Functionally and structurally PSA is a kallikrein-like serine protease, and its physiologic role is degradation of the major proteins of seminal coagulum (semenogelin I and II, fibronectin), which leads to semen liquefaction. The PSA gene is located on the 13q region of chromosome 19, and it has a high degree of homology (more than 80%) with genes of the human glandular kallikrein (hKGK1). PSA production and expression are preferentially but not exclusively associated to the normal, benign hyperplastic and cancerous tissues of the prostate. In fact, it has been demonstrated that PSA is also present in accessory male sex glands and breast cancer. It was recently reported that PSA was also present in milk of lactating women. Many factors may influence PSA synthesis and production, and among them the most important are androgen, retinoic acid and growth factor stimulation. Significant advances have been recently made as regards the molecular isoforms of PSA. In the seminal fluid PSA seems partially bound to a serpine (protein C inhibitor), whereas in serum it is predominantly associated to α-1-antichymotrypsin and in a small quantity to α-2-macroglobulin. These new findings will have implications for the clinical application of PSA as a tumor marker for prostate cancer.

BTA-TRAK combined with urinary cytology is a reliable urinary indicator of recurrent transitional cell carcinoma (TCC) of the bladder.

This study evaluated the diagnostic accuracy of BTA-TRAK in combination with urinary cytology (UC) in the follow-up of patients with a history of transitional cell carcinoma (TCC) of the bladder. The overall sensitivity of BTA-TRAK, UC and the two tests combined for the detection of recurrences was 82.7% (48/58), 84.2% (48/57) and 91.2% (52/57), respectively. BTA and UC showed comparable sensitivity for superficial recurrences (76.7% (33/43) and 78.5% (33/42), respectively) and for invasive recurrences (100% (15/15)); when the two tests were used in combination, the sensitivity for superficial lesions increased to 88% (37/42). BTA-TRAK was more sensitive than UC for G1 recurrences (81.2% (13/16) vs. 68.7% (11/16)), and when the two tests were combined the sensitivity increased to 87.5% (14/16). The sensitivity of the combination was 100% (15/15) for G3 lesions. The differences in urinary BTA-TRAK levels between patients with recurrences and those without evidence of disease were statistically significant (Wilcoxons test, p<0.05); among patients with recurrences BTA levels were significantly higher in the invasive and poorly differentiated subtypes. In the series of patients studied by us, BTA-TRAK combined with UC was shown to be a non-invasive, accurate test to predict TCC recurrences. Periodic measurement of BTA-TRAK combined with urinary cytology seems to provide additional information for the monitoring of patients treated for TCC; however, due to the presence of false positive and false negative results, this test cannot replace cystoscopy. In a selected group of patients it could, if combined with cytology and ultrasonography and if correctly used and interpreted, orient the timing and indication for cystoscopy.

Hormonal regulation of MUC1 expression.

Several circulating mucinous markers, including CA 15.3, MCA, CA 459, CASA, and Truquant BR, are secreted products of the polymorphic MUC1 gene, and are used as diagnostic tools in patients with breast cancer. In clinical practice the measurement of the levels of these markers in the blood can give important information on the tumors response to treatment and its biological behavior during disease monitoring. Since the marker levels reflect the activity of the tumor, it is important to know all factors influencing the production/secretion and the blood concentrations of MUC1 mucin. Recent findings suggest that MUC1 gene expression is regulated by steroid hormones and other substances present in the serum. Such observations are very important not only because of their biological significance but also for their clinical implications, as one approach to breast cancer therapy is based on chemical hormone manipulation. Nevertheless, we have preliminarily demonstrated that endocrine treatment in breast cancer patients does not influence the circulating CA 15.3 serum levels, so changes in marker levels are related only to the clinical evolution of the tumor.

Uptake of tritiated thymidine, deoxyglucose and methionine in three lung cancer cell lines : Deoxyglucose uptake mirrors tritiated thymidine uptake

[18F]-fluorodeoxyglucose and [11C]-methionine are tracers which are widely used in oncological positron emission tomography. This study has been designed to assess the deoxyglucose and methionine uptake behaviour in three cell lines from different lung cancer histotypes. Tracer uptake was compared with proliferative activity as determined by growth curves and tritiated thymidine uptake. Deoxyglucose paralleled thymidine in all cell lines, peaking in the lag phase, decreasing throughout the exponential phase, and reaching its minimum in the plateau phase. The correlation was statistically verified and Spearman’s ρ ranged from 0.79 to 0.99. The absolute methionine uptake was always highest and always peaked on day 2, followed by a quite rapid decrease. However, besides the delay in maximum uptake, methionine incorporation was also related to proliferation, although the statistical correlations were weaker. These results show for the first time a clear correlation between deoxyglucose uptake and cell proliferation in a model comparing tracer uptake in different growth phases. Although delayed, methionine uptake was also related to cell growth and its greater intensity could be of interest for clinical use.

Potential circulating markers for the management of kidney cancer (Review)

The prognosis of renal cell carcinoma (RCC) is generally poor. An easier detection of this tumor and a better monitoring of RCC patients would be possible if serum markers with acceptable sensitivity and specificity were available. In RCC, as opposed to other cancers, no circulating serum markers with sufficient renal specificity have been discovered. In fact, even when the hybridoma technology allowed the production of several monoclonal antibodies against RCC structures, none of them led to any available diagnostic immunoassays. Other possible circulating tumor markers of potential application in RCC patients include different substances such as acute phase reactant proteins, enzymes, mucins, cytokeratins, proteins, interleukins, that demonstrated some relationship with the presence and the changes in the RCC evolution. In this general review we report and discuss the results in the literature obtained by serum assays of these substances which have been shown to be of some help for the prognosis and monitoring of RCC. The greater part of these biomolecules are already measured in clinical practice for the management of other malignancies, but their application in RCC could give interesting clinical information.