Molecular genetic investigations of the mechanism of tumourigenesis in von Hippel-Lindau disease: analysis of allele loss in VHL tumours

Von Hippel-Lindau (VHL) disease is a dominantly inherited familial cancer syndrome characterised by the development of retinal and central nervous system haemangioblastomas, renal cell carcinoma (RCC), phaeochromocytoma and pancreatic tumours. The VHL disease gene maps to chromosome 3p25-p26. To investigate the mechanism of tumourigenesis in VHL disease, we analysed 24 paired blood/tumour DNA samples from 20 VHL patients for allele loss on chromosome 3p and in the region of tumour suppressor genes on chromosomes 5, 11, 13, 17 and 22. Nine out of 24 tumours showed loss of heterozygosity (LOH) at at least one locus on chromosome 3p and in each case the LOH included the region to which the VHL gene has been mapped. Chromosome 3p allele loss was found in four tumour types (RCC, haemangioblastoma, phaeochromocytoma and pancreatic tumour) suggesting a common mechanism of tumourigenesis in all types of tumour in VHL disease. The smallest region of overlap was between D3S1038 and D3S18, a region that corresponds to the target region for the VHL gene from genetic linkage studies. The parental origin of the chromosome 3p25-p26 allele loss could be determined in seven tumours from seven familial cases; in each tumour, the allele lost had been inherited from the unaffected parent. Our results suggest that the VHL disease gene functions as a recessive tumour suppressor gene and that inactivation of both alleles of the VHL gene is the critical event in the pathogenesis of VHL neoplasms. Four VHL tumours showed LOH on other chromosomes (5q21, 13q, 17q) indicating that homozygous VHL gene mutations may be required but may not be sufficient for tumourigenesis in VHL disease.     

Multiple endocrine neoplasia associated with von Recklinghausen's disease.

Details were studied of three patients with duodenal carcinoid tumour in association with neurofibromatosis and phaeochromocytoma, and of four patients with duodenal carcinoid and either von Recklinghausen''s disease or phaeochromocytoma. The rarity of these endocrine tumours, together with the unusual morphological features and somatostatin content of the two duodenal carcinoids examined, suggest that this combination of tumours is not a chance association. It is suggested that this linkage of neurofibromatosis, phaeochromocytoma, and duodenal carcinoid is a specific multiple endocrine neoplasia syndrome.     

Role of venous sampling in locating a phaeochromocytoma.

Selective venous sampling was performed in 31 patients in whom the diagnosis of phaeochromocytoma was suspected on clinical and biochemical grounds. Data from samples assayed for their adrenaline and noradrenaline content using a radioenzymatic technique were used to confirm or refute the suspected diagnosis. In 19 of the 31 patients a phaeochromocytoma was subsequently removed surgically, and the remaining 12 patients are now thought not to have tumours (mean follow up period: four years). Analysis of the assay data shows that selective venous sampling correctly identified the presence of a tumour in all 19 patients, and correctly excluded the diagnosis in 11 of the 12 remaining patients--an overall success rate of 97%. Success rates of 88% for arteriography and 84% for computed tomography were recorded, though these investigations were not performed in all patients. Ultrasound and intravenous urography were much less accurate. On the basis of this study a sequence of investigation is proposed for patients with a suspected phaeochromocytoma. Computed tomography occupies a central role in this sequence with venous sampling (and occasionally other techniques) being used only as complementary investigations when specific indications for their use exist.     

Chromogranin a expression in phaeochromocytomas associated with von Hippel-Lindau syndrome and multiple endocrine neoplasia type 2.

Chromogranin A (CGA) is a major secretory protein present in the soluble matrix of chromaffin granules of neuroendocrine cells and tumours, such as phaeochromocytomas. CGA has several functions, some of which may be involved in the distinct phenotypic differences of phaeochromocytomas in patients with von Hippel-Lindau (VHL) syndrome compared to multiple endocrine neoplasia type 2 (MEN 2). In this study, we therefore compared tumour and plasma levels of CGA in patients with phaeochromocytoma associated with the two syndromes. We show that phaeochromocytomas from MEN 2 patients express substantially more CGA than tumours from VHL patients at both the mRNA (3-fold greater) and protein (20-fold) level. We further show that relative to increases in plasma catecholamines, patients with phaeochromocytomas associated with MEN 2 have higher plasma concentrations of CGA than those with tumours in VHL syndrome. These data supplement other observations that phaeochromocytomas in VHL compared to MEN 2 patients express lower amounts of catecholamines and other chromaffin granule cargo, such as chromogranin B and neuropeptide Y. Possibly the differences in tumour CGA expression may contribute to differences in secretory vesicle formation and secretion in the two types of tumours. Alternatively the differences in expression in CGA and other secretory constituents may reflect downregulation of the entire regulated secretory pathway in VHL compared to MEN 2 tumours.     

Demonstration of a neuropeptide Y-like immunoreactivity in human phaeochromocytoma extracts

Using a porcine neuropeptide Y directed radioimmunoassay it was shown that acid extracts of human phaeochromocytoma tumour tissue contained a neuropeptide Y-like peptide. Further fractionation and purification of this immunoreactivity showed that this human neuropeptide Y-like immunoreactivity was closely similar in molecular size and separation characteristics to porcine neuropeptide Y. The possible contribution of neuropeptide Y to the hypertension characterizing human phaeochromocytoma is discussed.     

Haploinsufficiency for tumour suppressor genes: when you don't need to go all the way

Classical tumour suppressor genes are thought to require mutation or loss of both alleles to facilitate tumour progression. However, it has become clear over the last few years that for some genes, haploinsufficiency, which is loss of only one allele, may contribute to carcinogenesis. These effects can either be directly attributable to the reduction in gene dosage or may act in concert with other oncogenic or haploinsufficient events. Here we describe the genes that undergo this phenomenon and discuss possible mechanisms that allow haploinsufficiency to display a phenotype and facilitate the pathogenesis of cancer.     

Regulation of microtubule stability by the von Hippel-Lindau tumour suppressor protein pVHL

Von Hippel-Lindau (VHL) tumour suppressor gene inactivation is linked to the development of haemangioblastomas in the central nervous system and retina, often in association with other tumours, such as clear-cell carcinomas of the kidney and phaeochromocytomas. Here we show that the VHL protein (pVHL) is a microtubule-associated protein that can protect microtubules from depolymerization in vivo. Both the microtubule binding and stabilization functions of pVHL depend on amino acids 95-123 of pVHL, a mutational 'hot-spot' in VHL disease. From analysis of naturally occurring pVHL mutants, it seems that only point mutations such as pVHL(Y98H) and pVHL(Y112H) (that predispose to haemangioblastoma and phaeochromocytoma, but not to renal cell carcinoma) disrupt pVHL's microtubule-stabilizing function. Our data identify a role for pVHL in the regulation of microtubule dynamics and potentially provide a link between this function of pVHL and the pathogenesis of haemangioblastoma and phaeochromocytoma in the context of VHL disease.     

Secretion of Dopa in Phaeochromocytoma

In a series of 11 cases with phaeochromocytoma, two patients were found in whom the tumour secreted dopa in addition to dopamine, noradrenaline, and adrenaline. These two patients were normotensive in spite of high plasma and urinary levels of noradrenaline and adrenaline. This raises the possibility that dopa may be able to protect against the hypertensive action of noradrenaline. Such a mechanism would also explain the absence of hypertension in many cases of neuroblastoma.     

Epigenetic Alterations in Fanconi Anaemia: Role in Pathophysiology and Therapeutic Potential

Fanconi anaemia (FA) is an inherited disorder characterized by chromosomal instability. The phenotype is variable, which raises the possibility that it may be affected by other factors, such as epigenetic modifications. These play an important role in oncogenesis and may be pharmacologically manipulated. Our aim was to explore whether the epigenetic profiles in FA differ from non-FA individuals and whether these could be manipulated to alter the disease phenotype. We compared expression of epigenetic genes and DNA methylation profile of tumour suppressor genes between FA and normal samples. FA samples exhibited decreased expression levels of genes involved in epigenetic regulation and hypomethylation in the promoter regions of tumour suppressor genes. Treatment of FA cells with histone deacetylase inhibitor Vorinostat increased the expression of DNM3Tβ and reduced the levels of CIITA and HDAC9, PAK1, USP16, all involved in different aspects of epigenetic and immune regulation. Given the ability of Vorinostat to modulate epigenetic genes in FA patients, we investigated its functional effects on the FA phenotype. This was assessed by incubating FA cells with Vorinostat and quantifying chromosomal breaks induced by DNA cross-linking agents. Treatment of FA cells with Vorinostat resulted in a significant reduction of aberrant cells (81% on average). Our results suggest that epigenetic mechanisms may play a role in oncogenesis in FA. Epigenetic agents may be helpful in improving the phenotype of FA patients, potentially reducing tumour incidence in this population.     

Characterization of Catecholamine-Storage Organelles in Transplantable Phaeochromocytoma and Adrenal Glands of Rats

Abstract: The properties of the catecholamine-storing organelles from transplantable rat phaeochromocytoma and rat adrenal glands were compared by density gradient centrifugation. It was shown that tumour granules are more heterogeneous and less dense than adrenal granules. Both granule preparations can take up catecholamines and nucleotides by a process driven by an electrochemical proton gradient. Dopamine β-hydroxylase and glycoprotein III were analysed by immunological techniques. Glycoprotein III was shown to be a specific component of chromaffin granules. Tumour tissue (average weight 700 mg) contains amounts of these antigens comparable to those in 210 adrenals. The biosynthesis of granules in the tumour apparently occurs at a low rate, making turnover studies difficult. The transplantable rat phaeochromocytoma is very useful for studies on the uptake properties and the immunological characteristics of rat catecholamine storage granules because one tumour provides an amount of material that could otherwise be obtained only from a large number of adrenal glands.     

Polymeric immunoglobulin M is secreted by transfectants of non-lymphoid cells in the absence of immunoglobulin J chain.

Plasmids were constructed in which expression of genes encoding the heavy and light chains of a hapten-specific IgM antibody is under control of a heat shock promoter. Glioma, phaeochromocytoma and other non-lymphoid cell lines transfected with the plasmids were able to process and secrete immunoglobulin following heat induction. The glioma transfectants were studied in detail and were shown to secrete polymeric IgM in a yield similar to that obtained with a plasmacytoma. However, the glioma IgM was not associated with J chain and was largely composed of pentamers and hexamers. Thus, neither J chain nor other lymphoid-specific proteins are required for assembly and secretion of polymeric IgM although the absence of J chain may encourage hexamer formation.     

Radiolabelled metaiodobenzylguanidine targeted radiotherapy for malignant phaeochromocytoma.

Metaiodobenzylguanidine (MIBG) targeted radiotherapy is a promising treatment for malignant phaeochromocytoma. It is an effective palliative therapy and may influence prognosis by reducing tumour metabolic function and preventing excessive catecholamine secretion. Repeated treatments are necessary to achieve tumour arrest and disease regression, and it is essential that patients are followed closely for life. Toxicity is limited to myelosuppression but is cumulative. Bone marrow harvesting is recommended for all patients who are likely to undergo repeated treatments. Heightened clinical awareness and easier diagnosis of malignancy using MIBG scintigraphy are likely to result in an increasing number of referrals for treatment. It is essential, therefore, that experience is pooled from individual centres and that patients are treated according to agreed protocols, so that results can be directly compared.     

Variations of chromosomes 2 and 3 gene expression profiles among pulmonary telocytes,pneumocytes, airway cells,mesenchymal stem cells and lymphocytes

Telocytes (TCs) were identified as a distinct cellular type of the interstitial tissue and defined as cells with extremely long telopodes (Tps). Our previous data demonstrated patterns of mouse TC‐specific gene profiles on chromosome 1. The present study focuses on the identification of characters and patterns of TC‐specific or TC‐dominated gene expression profiles in chromosome 2 and 3, the network of principle genes and potential functional association. We compared gene expression profiles of pulmonary TCs, mesenchymal stem cells, fibroblasts, alveolar type II cells, airway basal cells, proximal airway cells, CD8⁺T cells from bronchial lymph nodes (T‐BL), and CD8⁺ T cells from lungs (T‐LL). We identified that 26 or 80 genes of TCs in chromosome 2 and 13 or 59 genes of TCs up‐ or down‐regulated in chromosome 3, as compared with other cells respectively. Obvious overexpression of Myl9 in chromosome 2 of TCs different from other cells, indicates that biological functions of TCs are mainly associated with tissue/organ injury and ageing, while down‐expression of Pltp implies that TCs may be associated with inhibition or reduction of inflammation in the lung. Dominant overexpression of Sh3glb1, Tm4sf1 or Csf1 in chromosome 3 of TCs is mainly associated with tumour promotion in lung cancer, while most down‐expression of Pde5 may be involved in the development of pulmonary fibrosis and other acute and chronic interstitial lung disease.     

Aromatase inhibitors--gene discovery

Microarray analysis of tumour RNA is an extremely powerful tool which allows global gene expression to be measured. When used in combination with neoadjuvant treatment protocols in which therapy is given with the primary tumour within the breast, sequential biopsies may be analysed and results correlated with clinical and pathological response. In the present study, a neoadjuvant protocol has been used, administering the third generation inhibitor, letrozole, for 3 months and subjecting RNA extracted from biopsies taken before and after 10–14 days of treatment to microarray analysis. The objectives were to discover: (i) genes that change with estrogen deprivation (the only known biological effect of letrozole is to inhibit aromatase activity and reduce endogenous estrogens in postmenopausal women) and (ii) genes whose basal, on treatment or change in expression differ between tumours which are either responsive or resistant to treatment (so that predictive indices of response/resistance may be developed).

Early changes in gene expression were identified by comparing paired tumour core biopsies taken before and after 14 days treatment in 58 patients using three different approaches based on frequency of changes, magnitude of changes and SAM analysis. All three approaches showed a greater number of genes were down-regulated than up-regulated. Merging of the data produced a total of 143 genes which were subject to gene ontology and cluster analysis. The ontology of the 91 down-regulated genes showed that they were functionally associated with cell cycle progression, particularly mitosis. In contrast, up-regulated genes were associated with organ development and extra-cellular matrix turnover and regulation.

Clinical response was assessable in 52 patients; 37 (71%) tumours were classified as clinical responders (>50% reduction in volume at 3 months). Microarray analysis of pre- and 14-day biopsies identified 291 covariates (84 baselines, 72 14-day and 135 changes) highly predictive of response status. A similarity matrix using the covariates showed responding tumours have a similar genetic profile which was dissimilar to non-responding cancers whereas non-responsive cases were distinctive from each other. Changed genes predicting for response showed no concordance with those changed significantly by treatment in the overall group.     

Thrombospondin-1 expression in breast cancer: prognostic significance and association with p53 alterations, tumour angiogenesis and extracellular matrix components

Thrombospondin (TSP-1) is a 450-kd adhesive glycoprotein that was initially discovered in platelets and subsequently in a variety of cell types. Several reports suggest that TSP-1 possesses tumour suppressor function, through its ability to inhibit tumour neovascularization. In this study we investigated tissue sections from 124 breast carcinomas for the immuno-histochemical expression of TSP-1 protein and its relationship to several clinicopathological parameters. The possible relationship to hormone receptors content, p53 protein, proliferation associated indices, angiogenesis, VEGF expression and extracellular matrix components (tenascin, fibronectin, laminin, collagen type IV and syndecan-1) was also estimated. TSP-1 was detected in the perivascular tissue, at the epithelial-stromal junction, in the stroma and in the tumour cells. High tumour cell TSP-1 expression was observed in 9.7%, moderate in 17.7%, mild in 10.5%, while 62.1% of the cases were negative for TSP-1 expression. The survival analysis showed an increased risk of recurrence associated with low TSP-1 tumour cell expression. High stromal TSP-1 expression was observed in 3.2% of the cases, moderate in 3.3%, mild in 27.4%, while 63.6% of the cases showed absence of TSP-1 expression. This expression was higher in invasive lobular type of breast cancer and inversely correlated with the lymph node involvement and the estrogen receptor content. Stromal TSP-1 expression was also positively correlated with extracellular matrix components expression, tenascin, fibronectin, collagen type IV, laminin, and syndecan-1. The relationship of TSP-1 expression with tumor angiogenesis, growth fraction and p53 protein expression was not significant. Our data suggest that TSP-1 expression seems to be associated with favorable biological behavior and may have clinical value in terms of predicting the risk of recurrence. In addition, TSP-1 might not be a direct anti-angiogenic factor, although it seems to be implicated in the remodeling of breast cancer tissue through interaction with other extracellular matrix components.     

Biochemical tests for diagnosis of phaeochromocytoma: urinary versus plasma determinations.

Fifteen patients with hypertension due to phaeochromocytoma and 35 controls with essential hypertension were studied to assess the diagnostic value of urinary and plasma biochemical determinations in phaeochromocytoma. In every case of phaeochromocytoma the urinary concentration of vanillylmandelate, metanephrines, or adrenaline plus noradrenaline was diagnostic of the disease irrespective of whether the patient was normotensive or hypertensive at the time. Plasma determinations of adrenaline and noradrenaline, however, gave falsely negative results on three occasions. These findings suggest that urinary biochemical determinations--particularly of metanephrines--are more reliable than plasma catecholamine measurements as a test for phaeochromocytoma. The test is particularly useful in patients with intermittent hypertension.